WO2024119510A1 - Dispositifs et procédés de communication - Google Patents

Dispositifs et procédés de communication Download PDF

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Publication number
WO2024119510A1
WO2024119510A1 PCT/CN2022/138107 CN2022138107W WO2024119510A1 WO 2024119510 A1 WO2024119510 A1 WO 2024119510A1 CN 2022138107 W CN2022138107 W CN 2022138107W WO 2024119510 A1 WO2024119510 A1 WO 2024119510A1
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WIPO (PCT)
Prior art keywords
terminal device
relay
link quality
link
condition
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PCT/CN2022/138107
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English (en)
Inventor
You Li
Gang Wang
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Nec Corporation
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Publication date
Application filed by Nec Corporation filed Critical Nec Corporation
Priority to PCT/CN2022/138107 priority Critical patent/WO2024119510A1/fr
Publication of WO2024119510A1 publication Critical patent/WO2024119510A1/fr

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  • Example embodiments of the present disclosure generally relate to the field of communication techniques and in particular, to devices and methods for relay reselection and fallback to a direct link of user equipment (UE) -to-UE relay.
  • UE user equipment
  • a terminal device e.g., user equipment, UE
  • UE may communicate with another terminal device via a direct link or an indirect link.
  • the terminal devices may communicate with each other via at least one further terminal device, which is called relay terminal device.
  • relay terminal device Such relay communication is also referred to as U2U relay.
  • U2U relay As the locations of the terminal devices and the communication conditions may change over time, it is desired to trigger relay reselection or fallback to a direct link. However, there is lacking details about the relay reselection and fallback to the direct link in U2U relay.
  • embodiments of the present disclosure provide methods, devices and computer storage medium for relay reselection and fallback to a direct link of U2U relay.
  • a first terminal device comprising a processor configured to cause the first terminal device to: receive, from a relay terminal device or a second terminal device, first information indicating at least one of the following: a first link quality between the first terminal device and the relay terminal device, or a second link quality between the relay terminal device and the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and perform, based at least in part on the first information, a decision about a relay reselection or a fallback to a direct link for a further communication between the first and second terminal devices.
  • a terminal device comprising: a processor configured to cause the terminal device to: determine first information indicating at least one of the following: a first link quality between a first terminal device and a relay terminal device, or a second link quality between the relay terminal device and a second terminal device, the terminal device comprising the relay terminal device or the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and transmit the first information to the first terminal device or the second terminal device.
  • a relay terminal device comprising: a processor configured to cause the device to: determine second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determine, based at least in part on the second information, whether a relay reselection is to be triggered to reselect a further relay terminal device for a further communication between the first and second terminal devices; and in accordance with a determination that the relay reselection is to be triggered, transmit a first indication of relay reselection to at least one of the first terminal device or the second terminal device.
  • a relay terminal device comprising: a processor configured to cause the device to: determine second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determine, based at least in part on the second information, that at least one of a first link between the first terminal device and the relay terminal device, or a second link between the relay terminal device and the second terminal device is to be released; and transmit, to at least one of the first terminal device or the second terminal device, a second indication of releasing at least one of the first link or the second link.
  • a communication method comprises: receiving, at a first terminal device and from a relay terminal device or a second terminal device, first information indicating at least one of the following: a first link quality between the first terminal device and the relay terminal device, or a second link quality between the relay terminal device and the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and performing, based at least in part on the first information, a decision about a relay reselection or a fallback to a direct link for a further communication between the first and second terminal devices.
  • a communication method comprises: determining, at a relay terminal device or a second terminal device, first information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and transmit the first information to the first terminal device or the second terminal device.
  • a communication method comprises: determining second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determining, based at least in part on the second information, whether a relay reselection is to be triggered to reselect a further relay terminal device for a further communication between the first and second terminal devices; and in accordance with a determination that the relay reselection is to be triggered, transmitting a first indication of relay reselection to at least one of the first terminal device or the second terminal device.
  • a communication method comprises: determining second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determining, based at least in part on the second information, that at least one of a first link between the first terminal device and the relay terminal device, or a second link between the relay terminal device and the second terminal device is to be released; and transmitting, to at least one of the first terminal device or the second terminal device, a second indication of releasing at least one of the first link or the second link.
  • a terminal device comprising: a processor configured to cause the device to: receive, from a relay terminal device, a first indication of relay reselection to reselect a further relay terminal device for a further communication between a first terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and in response to the first indication, perform the relay reselection to reselect the further relay terminal device for a further communication between the first and second terminal devices.
  • a terminal device comprising: a processor configured to cause the device to: receive, from a relay terminal device, a second indication of releasing at least one of a first link between a first terminal device and the relay terminal device, or a second link between the relay terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device; and in response to the second indication, release the first link or the second link with the relay terminal device.
  • a communication method comprises: receiving, from a relay terminal device, a first indication of relay reselection to reselect a further relay terminal device for a further communication between a first terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and in response to the first indication, performing the relay reselection to reselect the further relay terminal device for a further communication between the first and second terminal devices.
  • a communication method comprises: receiving, from a relay terminal device, a second indication of releasing at least one of a first link between a first terminal device and the relay terminal device, or a second link between the relay terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device; and in response to the second indication, releasing the first link or the second link with the relay terminal device.
  • a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of the fifth, sixth, seven, eighth, eleventh, or twelve aspect.
  • FIG. 1 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented
  • FIGS. 2A-2D illustrate example protocol stacks for sidelink communications
  • FIG. 3 illustrates a signaling flow for communications in U2U relay according to some example embodiments of the present disclosure
  • FIGS. 4A-4D illustrate example scenarios where link qualities between the terminal devices can change
  • FIG. 5 illustrates a signaling flow for communications in U2U relay according to some other example embodiments of the present disclosure
  • FIG. 6 illustrates a signaling flow for communications in U2U relay according to some further example embodiments of the present disclosure
  • FIG. 7 illustrates a flowchart of a method implemented at a terminal device according to some other example embodiments of the present disclosure
  • FIG. 8 illustrates a flowchart of a method implemented at a terminal device according to some further example embodiments of the present disclosure
  • FIG. 9 illustrates another flowchart of a method implemented at a terminal device according to some further example embodiments of the present disclosure.
  • FIG. 10 illustrates another flowchart of a method implemented at a terminal device according to some further example embodiments of the present disclosure
  • FIG. 11 illustrates another flowchart of a method implemented at a terminal device according to some further example embodiments of the present disclosure
  • FIG. 12 illustrates another flowchart of a method implemented at a terminal device according to some further example embodiments of the present disclosure
  • FIG. 13 illustrates a simplified block diagram of an apparatus that is suitable for implementing example embodiments of the present disclosure.
  • terminal device refers to any device having wireless or wired communication capabilities.
  • the terminal device include, but not limited to, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, tablets, wearable devices, internet of things (IoT) devices, Ultra-reliable and Low Latency Communications (URLLC) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, devices on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, devices for Integrated Access and Backhaul (IAB) , Space borne vehicles or Air borne vehicles in Non-terrestrial networks (NTN) including Satellites and High Altitude Platforms (HAPs) encompassing Unmanned Aircraft Systems (UAS) , eXtended Reality (XR) devices including different types of realities such as Augmented Reality (AR) , Mixed Reality (MR) and Virtual Reality (VR) , the unmanned aerial vehicle (UAV)
  • UE user equipment
  • the ‘terminal device’ can further has ‘multicast/broadcast’ feature, to support public safety and mission critical, V2X applications, transparent IPv4/IPv6 multicast delivery, IPTV, smart TV, radio services, software delivery over wireless, group communications and IoT applications. It may also incorporate one or multiple Subscriber Identity Module (SIM) as known as Multi-SIM.
  • SIM Subscriber Identity Module
  • the term “terminal device” can be used interchangeably with a UE, a mobile station, a subscriber station, a mobile terminal, a user terminal or a wireless device.
  • network device refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate.
  • a network device include, but not limited to, a Node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNB) , a transmission reception point (TRP) , a remote radio unit (RRU) , a radio head (RH) , a remote radio head (RRH) , an IAB node, a low power node such as a femto node, a pico node, a reconfigurable intelligent surface (RIS) , and the like.
  • NodeB Node B
  • eNodeB or eNB evolved NodeB
  • gNB next generation NodeB
  • TRP transmission reception point
  • RRU remote radio unit
  • RH radio head
  • RRH remote radio head
  • IAB node a low power node such as a fe
  • the terminal device or the network device may have Artificial Intelligence (AI) or Machine Learning (ML) capability. It generally includes a model which has been trained from numerous collected data for a specific function, and can be used to predict some information.
  • AI Artificial Intelligence
  • ML Machine Learning
  • the terminal or the network device may work on several frequency ranges, e.g., FR1 (e.g., 450 MHz to 6000 MHz) , FR2 (e.g., 24.25GHz to 52.6GHz) , frequency band larger than 100 GHz as well as Tera Hertz (THz) . It can further work on licensed/unlicensed/shared spectrum.
  • FR1 e.g., 450 MHz to 6000 MHz
  • FR2 e.g., 24.25GHz to 52.6GHz
  • THz Tera Hertz
  • the terminal device may have more than one connection with the network devices under Multi-Radio Dual Connectivity (MR-DC) application scenario.
  • MR-DC Multi-Radio Dual Connectivity
  • the terminal device or the network device can work on full duplex, flexible duplex and cross division duplex modes.
  • the embodiments of the present disclosure may be performed in test equipment, e.g., signal generator, signal analyzer, spectrum analyzer, network analyzer, test terminal device, test network device, channel emulator.
  • the terminal device may be connected with a first network device and a second network device.
  • One of the first network device and the second network device may be a master node and the other one may be a secondary node.
  • the first network device and the second network device may use different radio access technologies (RATs) .
  • the first network device may be a first RAT device and the second network device may be a second RAT device.
  • the first RAT device is eNB and the second RAT device is gNB.
  • Information related with different RATs may be transmitted to the terminal device from at least one of the first network device or the second network device.
  • first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device.
  • information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device.
  • Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.
  • the singular forms ‘a’ , ‘an’ and ‘the’ are intended to include the plural forms as well, unless the context clearly indicates otherwise.
  • the term ‘includes’ and its variants are to be read as open terms that mean ‘includes, but is not limited to. ’
  • the term ‘based on’ is to be read as ‘at least in part based on. ’
  • the term ‘one embodiment’ and ‘an embodiment’ are to be read as ‘at least one embodiment. ’
  • the term ‘another embodiment’ is to be read as ‘at least one other embodiment. ’
  • the terms ‘first, ’ ‘second, ’ and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.
  • values, procedures, or apparatus are referred to as ‘best, ’ ‘lowest, ’ ‘highest, ’ ‘minimum, ’ ‘maximum, ’ or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.
  • the term “resource, ” “transmission resource, ” “uplink resource, ” or “downlink resource” may refer to any resource for performing a communication, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other resource enabling a communication, and the like.
  • a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.
  • FIG. 1 illustrates a schematic diagram of an example communication environment 100 in which example embodiments of the present disclosure can be implemented.
  • a terminal device 110 communicates with a terminal device 120 via a terminal device 130.
  • the terminal device 130 operates as a relay for communications between the terminal devices 110 and 120.
  • the terminal device 130 is sometimes referred to as a relay terminal device, or a serving relay terminal device for the terminal devices 110 and 120.
  • the terminal devices 110 and 120 are sometimes referred to as remote terminal devices or end devices.
  • the terminal device 130 may relay traffic from the terminal device 110 to the terminal device 120.
  • the terminal device 110 is referred to as a source terminal device or a transmitting (TX) terminal device and the terminal device 120 is referred to as a destination terminal device or a receiving (RX) terminal device.
  • TX transmitting
  • RX receiving
  • traffic from the terminal device 120 to the terminal device 110 is also supported. That is, dual communications between the terminal devices 110 and 120 are enabled. It would also be appreciated that although one relay terminal device is illustrated, there may be two or more relay terminal devices operating for the terminal devices 110 and 120.
  • the terminal devices 110 and 120, and the terminal devices 120 and 130 may communicate with each other via sidelink (SL) connection (s) .
  • a sidelink is a communication mode that allows direct communications between two or more terminal devices without the communications going through network device.
  • SL communications may be carried out on a wireless interface, e.g., PC5 interface.
  • SL communications may be unicast, groupcast, or broadcast, and may be used for device-to-device (D2D) communications, vehicle-to-everything (V2X) communications, etc.
  • D2D device-to-device
  • V2X vehicle-to-everything
  • U2U relay may enable sidelink (SL) services even if two specific devices are not within range of each other.
  • SL sidelink
  • U2U relay communications may be useful in a variety of settings such as for communication in public safety networks, or in out-of-coverage or network overload scenarios.
  • the terminal device 110 is within coverage of a cell 152-1 served by a network device 150-1
  • the terminal device 120 is within coverage of a cell 152-2 served by a network device 150-2
  • the terminal device 130 is located at edges of the cells 152-1, 152-2 to relay traffic between the terminal devices 110, 120 within the two different cells.
  • the network devices 150-1, 150-2 are collectively or individually referred to as network devices 150
  • the cells 152-1, 152-2 are collectively or individually referred to as cells 152.
  • U2U relay may be applied in various other scenarios to support communications between two terminal devices.
  • some or all of the terminal devices 110, 120, 130, 140 may be out of the coverage of the cells 152 and their relative locations may be varied.
  • terminal devices 140 there may be other terminal devices, e.g., terminal devices 140-1, 140-2, 140-3 (collectively or individually referred to as terminal devices 140) within the communication environment 100. Those terminal devices 140 may be within or out of the coverage of the cells 152 and may also operate as candidate relay terminal devices. The terminal device 130 is selected instead of those terminal devices 140 to serve as a relay terminal device for the terminal devices 110 and 120 according to any suitable criteria for relay selection.
  • the communication environment 100 may include any suitable number of network devices and/or terminal devices adapted for implementations of example embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be located in the cell, and one or more additional cells may be deployed in the communication environment 100.
  • the communications in the communication environment 100 may conform to any suitable standards including, but not limited to, Global System for Mobile Communications (GSM) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , New Radio (NR) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , GSM EDGE Radio Access Network (GERAN) , Machine Type Communication (MTC) and the like.
  • GSM Global System for Mobile Communications
  • LTE Long Term Evolution
  • LTE-Evolution LTE-Advanced
  • NR New Radio
  • WCDMA Wideband Code Division Multiple Access
  • CDMA Code Division Multiple Access
  • GERAN GSM EDGE Radio Access Network
  • MTC Machine Type Communication
  • Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols, 5.5G, 5G-Advanced networks, or the sixth generation (6G) networks.
  • the terminal device 130 may be selected to serve as a relay terminal device for the terminal devices 110 and 120 through a U2U relay discovery procedure.
  • the U2U relay discovery procedure may be performed as either Model A (announce/monitor) or Model B (discoverer/discoveree) .
  • a terminal device e.g., the terminal devices 130, 140 may announce that it can act as a U2U relay by periodically transmitting an announcement message.
  • the announcement message may include a list of target user information.
  • the list of target user information may indicate a list of directly reachable neighbouring terminal devices which are discovered by the terminal devices 130, 140 in previous steps (based on previous discover or based on existing or prior communications between the terminal devices 130, 140 and the neighbouring terminal devices) .
  • the terminal device 110 or 120 may decide to select the terminal device 130 as its serving relay terminal device.
  • the terminal devices 110 and 120 may then establish a one-to-one communication link with each other via the terminal device 130.
  • the Model B procedure is performed with two messages: a solicitation message (typically broadcasted or groupcasted) and a response message (typically unicasted) .
  • the terminal device 110 may broadcast a solicitation message indicating that it wants to communicate with the terminal device 120 via a relay.
  • the terminal devices 130, 140 which are candidate relay terminal devices, may broadcast solicitation messages with relay service codes (RSCs) or UE identities (ID) of target terminal devices.
  • the solicitation messages from the terminal devices 130, 140 may have relay indications enabled.
  • the terminal device 120 which matches the RSC or UE ID respond to the terminal device, e.g., the terminal device 130 with a response message.
  • the terminal device 130 further sends a response message to the terminal device 110 on reception of the response message from the terminal device 120. In this way, relay communications between the terminal devices 110, 130, and 120 are established.
  • a protocol stack for a control plane for Sidelink Control Channel (SCCH) for Radio Resource Control (RRC) in the PC5 interface consists of RRC, Packet Data Convergence Protocol (PDCP) , Radio Link Control (RLC) and Media Access Control (MAC sublayers) , and the physical (PHY) layer.
  • Protocol stacks 210 of control plane of two terminal devices (UE A and UE B) for SCCH for RRC is shown in FIG. 2A.
  • a PC5-S sublayer is located on top of PDCP, RLC and MAC sublayers, and the PHY layer in the control plane protocol stack for SCCH for PC5-S, as shown in example protocol stacks 220 in FIG. 2B.
  • the RRC sublayer provides the following services and functions over the PC5 interface, including transferring of a PC5-RRC message between peer terminal devices, maintenance and release of a PC5-RRC connection between two terminal devices, and detection of sidelink radio link failure for a PC5-RRC connection.
  • a PC5-RRC connection is a logical connection between two UEs for a pair of Source and Destination Layer-2 IDs which is considered to be established after a corresponding PC5 unicast link is established. There is one-to-one correspondence between the PC5-RRC connection and the PC5 unicast link.
  • an example protocol stack of an end-to-end (E2E) user plane for U2U relay between two terminal devices which includes Internet Protocol (IP) , Non-IP sublayers, Service Data Adaptation Protocol (SDAP) sublayer on top of PDCP, RLC and MAC sublayers, and the PHY layer.
  • FIG. 2C illustrates user plane protocol stacks 230 using a U2U relay.
  • An Adaptation layer is included on top of the RLC layer for the U2U relay, and is include between the RLC layer and PDCP layer for UE1 and UE2.
  • the security is established end to end between two terminal devices (UE1 and UE2) . Therefore, user data is never exposed at the relay node since the relay function does not process/apply any security on the relayed packets. Both IP traffic and Non-IP traffic are supported.
  • FIG. 2D illustrates control plane protocol stacks 240 using a U2U relay.
  • a PC5-S sublayer is located on top of PDCP, Adaptation, RLC and MAC sublayers, and the PHY layer.
  • the security is established end to end between UE1 and UE2 as shown by the PDCP layer terminating in UE1 and UE2. Therefore, the E2E PC5-S message between UE1 and UE2 is never exposed at the relay node since the relay function does not process/apply any security on the relayed E2E PC5-S messages.
  • protocol stacks illustrated in FIGS. 2A-2D are provided for the purpose of illustration only without suggesting any limitation. Other protocol stacks may also be applicable to support the relayed communications or direct communication between terminal devices.
  • a terminal device may determine to select a relay terminal device for communication with another terminal device in the case that a link quality of a direct link between the two terminal devices falls below a threshold.
  • the serving relay terminal device may not be a suitable choice for the two terminal devices.
  • Example embodiments of the present disclosure provide solutions for relay reselection and fallback to a direct link of U2U relay.
  • a relay terminal device serving for a first terminal device and a second terminal device determines information indicating at least one of the following: a first link quality between the first terminal device and the relay terminal device, and a second link quality between the relay terminal device and the second terminal device.
  • Such information is transmitted to at least one of the first terminal device or the second terminal device for use in determining whether or not to trigger a relay reselection or a fallback to a direct link for a further communication between the first and second terminal devices.
  • such information can be determined by one of the first and second terminal devices instead of by the relay terminal device.
  • the information may be provided to one of the first and second terminal devices which is allowed to trigger the relay reselection or the fallback to a direct link.
  • the first terminal device and/or the second terminal device can make a decision about the relay reselection or the fallback.
  • the communications between the two terminal devices can be conducted via links with satisfied qualities.
  • the relay terminal device is allowed to make a decision about the relay reselection or the fallback to a direct link for a further communication between the first and second terminal devices. The decision may be made based on the information about the first link quality and/or the second link quality. In those solutions, the relay terminal device may indicate the relay reselection to the first terminal device and/or the second terminal device. In alternative solution, the relay terminal device may determine, based on the information, to release a first link between the first terminal device and the relay terminal device, and/or a second link between the relay terminal device and the second terminal device. In such a case, the relay terminal device may indicate the link release to the first terminal device and/or the second terminal device. Through those solutions, on the basis of sufficient information about the link qualities, the relay terminal device is enabled to actively trigger the relay reselection and/or the fallback to the direct link.
  • FIG. 3 illustrates a signaling flow 300 for U2U relay according to some example embodiments of the present disclosure.
  • the signaling flow 300 will be discussed with reference to FIG. 1.
  • the signaling flow 300 involves the terminal devices 110, 120, and 130 in FIG. 1.
  • the terminal devices involved in the signaling flow 300 may be any terminal devices in any suitable locations in the communication environment 100, within or out of coverage of the network devices 150. Only for the purpose of illustration, the terminal devices 110, 120, and 130 are referred for discussion. It is also to be understood that the signaling flow 300 may involves more devices in some embodiments as discussed below.
  • the terminal device 130 acts as a relay for communications between the terminal devices 110 and 120, so as to relay a communication (s) between the terminal devices 110 and 120.
  • the terminal device 130 may relay traffic, e.g., data, via End-to-End (E2E) radio bearer (RB) from the terminal device 110 to the terminal device 120 and/or vice versa.
  • E2E End-to-End
  • RB radio bearer
  • the terminal device 130 is sometimes referred to as a relay terminal device, or a serving relay terminal device for the terminal devices 110 and 120.
  • the terminal devices 110 and 120 are sometimes referred to as remote terminal devices.
  • the terminal device 110 is referred to as a first terminal device and the terminal device 120 is referred to as a second terminal device.
  • the terminal device 110 is configured to be allowed to make a decision about whether to perform a relay reselection and/or fallback to a direct link for the communication between the terminal devices 110 and 120.
  • the terminal device 130 or the terminal device 120 determines (305) first information indicating at least one of the following: a first link quality between the terminal device 110 and the terminal device 130, or a second link quality between the terminal device 130 and the terminal device 120.
  • a link (or hop) between the terminal device 110 and the terminal device 130 may sometimes be referred to as a first link or first hop, and a link (or hop) between the terminal device 130 and the terminal device 120 may sometimes be referred to as a second link or second hop.
  • Data and/or signaling communicated between the terminal devices 110 and 120 are relayed via the first and second links.
  • the first link and second link may be established via PC5 interfaces.
  • a link quality between two terminal devices may be measured through any suitable manners.
  • a link quality may be determined by a signal strength over the corresponding link.
  • a link quality may be measured as a reference signal received power (RSRP) over the corresponding link, e.g., PC5 RSRP.
  • RSRP reference signal received power
  • a metric for a link quality may include a PC5 RSRP of a link.
  • the PC5 RSRP may include SL RSRP or sidelink discovery (SD) RSRP.
  • the first information may include or indicate other contents, which will be discussed below. The details of the first information will be discussed below.
  • the terminal device 130 or the terminal device 120 transmits (310) the first information to the terminal device 110.
  • both the terminal devices 120 and 130 may transmit first information to the terminal device 110.
  • the terminal device 130 as a relay terminal device, may monitor the first link between the terminal devices 110 and 130, and transmit first information indicating at least the first link quality to the terminal device 110.
  • the terminal device 120 may monitor the second link between the terminal devices 130 and 120, and transmit first information indicating at least the second link quality to the terminal device 110.
  • the terminal device 130 may monitor the second link and report the second link quality to the terminal device 110.
  • the terminal device 130 or the terminal device 120 may be able to monitor both links and determine both the first link quality and the second link quality and thus may indicate the two link qualities in the first information transmitted to the terminal device 110.
  • the terminal device 130 may report its first information to the terminal device 110 via PC5 RRC signaling or PC5-S signaling. In some embodiments, the terminal device 130 may report its first information to the terminal device 110 via (per-hop) L2 control information, such as RLC control Protocol Data Unit (PDU) , MAC control element (CE) or the like. In some embodiments, the terminal device 130 may report the first information to the terminal device 110 via (per-hop) L1 control information such as sidelink control information (SCI) .
  • PDU RLC control Protocol Data Unit
  • CE MAC control element
  • SCI sidelink control information
  • the terminal device 120 may report its first information to the terminal device 110 via E2E signaling from the terminal device 120 to the terminal device 110, such as E2E RRC signaling or E2E PC5-S signaling.
  • the terminal device 120 may report its first information to the terminal device 110 via per-hop signaling, such as (per-hop) PC5 RRC signaling, including first (per-hop) signaling from the terminal device 120 to the terminal device 130 and second (per-hop) signaling from the terminal device 130 to the terminal device 110.
  • the first information may conveyed via a RLC relay channel or via per-hop PC5 RRC signaling.
  • the terminal device 120 may report its first information to the terminal device 110 via (per-hop) L2 control information, such as RLC control PDU, MAC CE or the like.
  • the terminal device 130 may report the first information to the terminal device 110 via (per-hop) L1 control information such as SCI.
  • the terminal device 110 receives (315) the first information from the terminal device 130 or the terminal device 120 and performs (320) a decision, based at least in part on the first information, about a relay reselection or a fallback to a direct link for a further communication between the terminal devices 110 and 120. That is, the first information may be used to decide whether the first link and/or the second link with the currently serving relay terminal device (i.e., the terminal device 130) are still suitable for the two terminal devices 110 and 120.
  • a relay reselection is to reselect a further terminal device as a relay terminal device for the terminal devices 110 and 120, while the fallback is to establish a direct link (e.g., a direct sidelink) between the terminal devices 110 and 120, without U2U relay. Additionally, a relay reselection is also to measure or monitor the quality of link between the terminal device 110 and at least one further terminal device, and/or the quality of link between the terminal device 120 and at least one further terminal device. Similarly, a fallback to a direct link is also to measure or monitor a quality link In embodiments of the present disclosure, a decision about a relay reselection is equivalent to a decision of triggering a relay reselection. Similarly, a decision about a fallback to a direct link is equivalent to a decision of triggering a fallback to a direct link.
  • the terminal device 130 is currently serving as a relay for the terminal devices 110 and 120, the locations of any of those terminal devices may change over time and thus the link qualities between any two of the terminal devices may change accordingly. With the first information, the terminal device 110 may be able to determine whether the terminal device 130 is still suitable for acting as the relay.
  • the terminal device 110 is configured to perform such a decision and to trigger the relay reselection and/or the fallback to a direct link.
  • the terminal device 110 may be configured with a first configuration for the relay reselection and/or a second configuration for the fallback to a direct link.
  • the terminal device 110 may perform the decision based on the received first information and the first configuration and/or the second configuration.
  • the first configuration may indicate in what condition (s) the relay reselection can be performed/triggered.
  • the second configuration may indicate in what condition (s) the fallback to a direct link can be performed/triggered.
  • the first configuration and/or the second configuration may be configured by a network device 150 to the terminal device 110.
  • the first configuration and/or the second configuration may be pre-configured at the terminal device 110.
  • the first configuration may indicate at least one of a first condition for the first link quality or a second condition for the second link quality.
  • the relay reselection may be triggered by a satisfaction of the first link quality with the first condition and/or a satisfaction of the second link quality with the second condition.
  • the first condition for the first link quality may indicate that a first metric for the first link quality is below a first lower threshold (e.g., threshold_min_RSRP_1) .
  • a metric for a link quality may be a specific measurement value indicating the link quality.
  • the first metric for the first link quality may be a RSRP measured on the first link between the terminal device 110 and the terminal device 130.
  • the second condition for the second link quality may indicate that a second metric for the second link quality is below a second lower threshold (e.g., threshold_min_RSRP_2) .
  • the second condition for the second link quality may indicate that the second metric for the second link quality exceeds a second upper threshold (e.g., threshold_max_RSRP_2) .
  • the first lower threshold (e.g., threshold_min_RSRP_1) may be the same as the second lower threshold (e.g., threshold_min_RSRP_2)
  • the first upper threshold e.g., threshold_max_RSRP_1
  • the second upper threshold e.g., threshold_max_RSRP_2
  • the first condition may be the same as the second condition.
  • the first lower threshold (e.g., threshold_min_RSRP_1) may be different from the second lower threshold (e.g., threshold_min_RSRP_2)
  • the first upper threshold e.g., threshold_max_RSRP_1
  • the second upper threshold e.g., threshold_max_RSRP_2
  • the first condition may be different from the second condition.
  • a single parameter may be used to configure the thresholds for use by a terminal device, which may reduce the signaling overhead of the threshold configuration.
  • separate configuration parameters may be used to configure the two or more thresholds no matter whether their values are the same as or different from each other.
  • the first condition for the first link quality may concern the first lower threshold (e.g., threshold_min_RSRP_1) only, and/or the second condition for the second link quality may concern the second lower threshold (e.g., threshold_min_RSRP_2) only. That is, only the worse quality of the first link and/or the second link may trigger the relay reselection.
  • the first condition for the first link quality may concern the first upper threshold (e.g., threshold_max_RSRP_1) only, and/or the second condition for the second link quality may concern the second upper threshold (e.g., threshold_max_RSRP_2) only. That is, only the extreme high quality of the first link and/or the second link may trigger the relay reselection.
  • the first condition for the first link quality may concern both the first lower threshold and the first upper threshold.
  • the second condition for the second link quality may concern both the second lower threshold and the second upper threshold.
  • FIG. 4A illustrate an example scenario where link qualities between the terminal devices can change such that the relay reselection is to be triggered.
  • the terminal device 120 moves from location A to location B. Due to the increased distance, a metric for a second link quality between the terminal device 120 at location B and the terminal device 130 becomes worse, e.g., lower than the second lower threshold.
  • a relay reselection may be needed to reselect another terminal device, e.g., the terminal device 140, to act as a relay for communications between the terminal devices 110 and 120.
  • FIG. 4B illustrate a further example scenario where link qualities between the terminal devices can change such that the relay reselection is to be triggered.
  • the terminal device 130 moves from location C to location D.
  • a metric for a first link quality between the terminal device 110 and the terminal device 130 at location D becomes worse, e.g., lower than the first lower threshold
  • a metric for a second link quality between the terminal device 120 and the terminal device 130 at location D becomes higher, e.g., exceeding the second upper threshold.
  • a relay reselection may be needed to reselect a more suitable terminal device, e.g., the terminal device 140, to act as a relay for communications between the terminal devices 110 and 120.
  • the second configuration for the fallback to the direct link may indicate at least one of a third condition for the first link quality or a fourth condition for the second link quality.
  • the fallback to the direct link may be triggered by a satisfaction of the first link quality with the third condition and/or a satisfaction of the second link quality with the fourth condition.
  • the third upper threshold e.g., threshold_max_RSRP_3) may be the same as the fourth upper threshold (e.g., threshold_max_RSRP_4) . That is, the third condition may be the same as the fourth condition.
  • the third upper threshold e.g., threshold_max_RSRP_3) may be different from the fourth upper threshold (e.g., threshold_max_RSRP_4) . That is, the third condition may be different from the fourth condition.
  • FIG. 4C and FIG. 4D illustrate some example scenarios where link qualities between the terminal devices can change such that the fallback is to be triggered.
  • the terminal device 120 moves from location E to location F. Due to the decreased distance, a metric for a second link quality between the terminal device 120 at location F and the terminal device 130 becomes higher, e.g., higher than the third upper threshold.
  • the terminal device 110 may want to establish a direct link with the terminal device 120 instead of communicating with the terminal device 120 via the U2U relay.
  • the terminal devices 120 moves from location G1 to location G2, and the terminal device 130 moves from location H1 to location H2.
  • direct communication between the terminal devices 110 and 120 may be more desirable than the relaying communication via the terminal device 130.
  • the terminal device 110 may make a decision on the link qualities of both of the first and second links or a link quality of either one of the two links. Specifically, the terminal device 110 may decide to perform a relay reselection if the first link quality satisfies the above-mentioned first condition and the second link quality satisfies the above-mentioned second condition, for example, PC5_RSRP_1 ⁇ threshold_min_RSRP_1 and PC5_RSRP_2 ⁇ threshold_min_RSRP_2.
  • the terminal device 110 may decide to perform the fallback to the direct link if both the first link quality satisfies the above-mentioned third condition and the second link quality satisfies the above-mentioned fourth condition, for example, PC5_RSRP_1> threshold_max_RSRP_3 and PC5_RSRP_2> threshold_max_RSRP_4.
  • the terminal device 110 may decide to perform the relay reselection upon either satisfaction of the first link quality with the first condition or satisfaction of the second link quality with the second condition. Similarly, in some further examples, the terminal device may decide to perform the fallback to the direct link upon either satisfaction of the first link quality with the third condition and satisfaction of the second link quality with the fourth condition.
  • the condition (s) for the terminal device 110 to trigger a relay reselection may reuse the lower threshold for UE-to-network (U2N) relay reselection.
  • U2N relay reselection refers to selecting a relay terminal device to relay communications between a terminal device and a network device.
  • the condition (s) for the terminal device 110 to trigger a relay reselection may reuse both the lower threshold and the upper threshold for U2N relay reselection.
  • the terminal device 110 may start a predetermined timer to wait for recovery of the one link quality or the deterioration of the other link quality.
  • the timer may be initiated with any suitable predetermined duration.
  • the terminal device 110 may trigger a relay reselection even if the timer is still running. In this case, the timer may be stopped, upon the trigger of the relay reselection or upon the determination that both the first and second link qualities satisfy their corresponding conditions.
  • their corresponding condition e.g., both lower than the corresponding lower thresholds
  • the terminal device 110 may perform a decision not to trigger the relay reselection. In this case, the timer may be stopped. In some embodiments, if the timer is expired (for example, upon timeout of the timer) and the one of the first and second link qualities which was worse before is still worse, the terminal device 110 may perform a decision of triggering a relay reselection.
  • the updates of the first link quality and/or the second link quality during the running of the timer may be conveyed to the terminal device 110 from the terminal device 130 and/or the terminal device 120 via further first information.
  • the terminal device 110 may make the decision about the fallback to the direct link in a similar manner as in making the decision about the relay reselection, by setting a predetermined timer.
  • the same upper threshold and the same trigger condition may be reused for both the relay reselection and the fallback, at least for the same link.
  • the first upper threshold e.g., threshold_max_RSRP_1
  • the third upper threshold e.g., threshold_max_RSRP_3
  • the second upper threshold e.g., threshold_max_RSRP_2
  • the fourth upper threshold e.g., threshold_max_RSRP_4
  • both the relay reselection procedure and the fallback to the direct link procedure may be triggered if at least one of the following is met: the first metric for the first link quality (e.g., PC5_RSRP_1) exceeds the corresponding upper threshold, or the second metric for the second link quality (e.g., PC5_RSRP_2) exceeds the corresponding upper threshold. If both the relay reselection procedure and the fallback to the direct link procedure are to be triggered, then the terminal device 110 may select one of the procedures based on various criteria. In some embodiments, the criteria may be up to the implementations at the terminal device 110.
  • the terminal device 110 may select one of the relay reselection procedure and the fallback to the direct link procedure to be performed based on quality of service (QoS) or the application or service type. For example, the fallback procedure may be selected if the service requires less delay.
  • the criteria for selecting the relay reselection procedure or the fallback to the direct link procedure may be pre-configured at the terminal device 110, or may be configured by the network device 150 or by other entities from the network side. Accordingly, the terminal device 110 is enabled to select a proper procedure even if the same upper thresholds are reused.
  • the relay reselection is triggered if only one of the first link quality or the second link quality satisfies the corresponding upper thresholds, for example, PC5_RSRP_1>threshold_max_RSRP_1 or PC5_RSRP_2>threshold_max_RSRP_2.
  • the fallback to the direct link is triggered if both the first link quality and the second link quality satisfy the corresponding upper thresholds, for example, PC5_RSRP_1>threshold_max_RSRP_1 and PC5_RSRP_2>threshold_max_RSRP_2.
  • the relay reselection is triggered instead of the fallback to the direct link.
  • different upper thresholds are used for the relay reselection and the fallback to the direct link. More specifically, the first upper threshold (e.g., threshold_max_RSRP_1) may be different from the third upper threshold (e.g., threshold_max_RSRP_3) for the first link quality. Similarly, the second upper threshold (e.g., threshold_max_RSRP_2) may be different from the fourth upper threshold (e.g., threshold_max_RSRP_4) for the second link quality.
  • the first upper threshold e.g., threshold_max_RSRP_1
  • the third upper threshold e.g., threshold_max_RSRP_3
  • the second upper threshold e.g., threshold_max_RSRP_2
  • the fourth upper threshold e.g., threshold_max_RSRP_4
  • both the relay reselection procedure and the fallback to the direct link procedure are to be triggered, for example, PC5_RSRP_1 >threshold_max_RSRP_1 and PC5_RSRP_1 > threshold_max_RSRP_3, wherein threshold_max_RSRP_3 > threshold_max_RSRP_1.
  • the terminal device 110 may select one of the procedures based on the various criteria as described above. Alternatively, only the corresponding procedure with the higher upper threshold is triggered (e.g., the fallback) .
  • the first information reported by the terminal device 130 or the terminal device 120 may include a first metric for the first link quality and/or a second metric for the second link quality.
  • the first information may include the specific RSRP value (s) monitored by the terminal device 130 or the terminal device 120 on the first link and/or the second link.
  • the terminal device 120 may compare the metric (s) with the corresponding lower and/or upper threshold as indicated by the condition (s) used to trigger the relay reselection or the fallback to the direct link.
  • the fist information may indicate the first link quality and/or the second link quality by including an indication (s) of whether the metric (s) of either or both of the link qualities is below a corresponding lower threshold or exceeds a corresponding upper threshold.
  • the terminal device 130 or the terminal device 120 may be configured with a fifth lower threshold (e.g., threshold_min_RSRP_5) and/or a fifth upper threshold (e.g., threshold_max_RSRP_5) for the first link quality.
  • the terminal device 130 or the terminal device 120 may include in the first information a first quality indication indicating whether the first metric exceeds the fifth upper threshold.
  • the terminal device 130 or the terminal device 120 may include in the first information a second quality indication indicating whether the first metric is below the fifth lower threshold.
  • the terminal device 130 or the terminal device 120 may be configured with a sixth lower threshold (e.g., threshold_min_RSRP_6) and/or a sixth upper threshold (e.g., threshold_max_RSRP_6) .
  • the terminal device 130 or the terminal device 120 may include in the first information a fourth quality indication indicating whether the second metric is below a sixth lower threshold (e.g., PC5_RSRP_2 ⁇ threshold_min_RSRP_6) .
  • a sixth lower threshold e.g., PC5_RSRP_2 ⁇ threshold_min_RSRP_6
  • the threshold (s) for the first link quality may be the same as or different from the threshold (s) for the second link quality.
  • the sixth lower threshold e.g., threshold_min_RSRP_6
  • the fifth lower threshold e.g., threshold_min_RSRP_5
  • the sixth upper threshold e.g., threshold_max_RSRP_6
  • the sixth lower threshold (e.g., threshold_min_RSRP_6) may be different from the fifth lower threshold (e.g., threshold_min_RSRP_5)
  • the sixth upper threshold e.g., threshold_max_RSRP_6
  • the fifth upper threshold e.g., threshold_max_RSRP_5
  • the terminal device 130 or the terminal device 120 may be configured to report the first information if at least one of the fifth lower threshold, the fifth upper threshold, the sixth lower threshold, the sixth upper threshold is met. For example, if it is determined that the first metric for the first link quality is blow the fifth lower threshold and/or exceeds the fifth upper threshold, and/or the second metric for the second link quality is below the sixth exceeds the sixth upper threshold, the terminal device 130 or the terminal device 120 may report the first information to the terminal device 110.
  • the terminal device 130 or the terminal device 120 may be configured with a configuration indicating at least one of the fifth lower threshold, the fifth upper threshold, the sixth lower threshold, or the sixth upper threshold.
  • This configuration may be configured by a network device 150 or may be pre-configured at the terminal device 130.
  • the conditions for the terminal device 110 to make a decision about the relay reselection and that for the terminal device 130 to trigger reporting of the first information may use the same threshold (s) at least for the same link.
  • the fifth lower threshold (e.g., threshold_min_RSRP_5) for the first link quality may be the same as the first lower threshold (e.g., threshold_min_RSRP_1)
  • the fifth upper threshold (e.g., threshold_max_RSRP_5) for the first link quality may be the same as the first upper threshold (e.g., threshold_max_RSRP_1) .
  • the sixth lower threshold (e.g., threshold_min_RSRP_6) for the second link quality may be the same as the second lower threshold (e.g., threshold_min_RSRP_2)
  • the sixth upper threshold (e.g., threshold_max_RSRP_6) for the second link quality may be the same as the second upper threshold (e.g., threshold_max_RSRP_2) .
  • the terminal device 110 may be able to make a decision about the relay reselection.
  • the terminal device 130 or the terminal device 120 may also be configured with the same upper threshold (s) for triggering the fallback to the direct link, e.g., the third upper threshold (e.g., threshold_max_RSRP_3) for the first link quality, and/or the fourth upper threshold (e.g., threshold_max_RSRP_4) for the second link quality.
  • the terminal device 130 or the terminal device 120 may additionally or alternatively include in the first information a quality indication indicating whether the first metric for the first link quality exceeds the third upper threshold (e.g., threshold_max_RSRP_3) , and/or a quality indication indicating whether the second metric for the second link quality exceeds the fourth upper threshold (e.g., threshold_max_RSRP_4) .
  • the terminal device 110 may be able to make a decision about the fallback to the direct link.
  • the terminal device 130 or the terminal device 120 may not need to include separate quality indications in the first information to indicate whether the first and third upper thresholds are respectively satisfied and/or whether the second/fourth upper threshold are respectively satisfied, which could reduce the signaling overhead.
  • the terminal device 130 may report the first information about the first and/or second link qualities periodically to the terminal device 110. In some embodiments, the terminal device 130 may report the first information about the first and/or second link qualities in response to a request from the terminal device 110. In some embodiments, the terminal device 130 may report the first information about the first and/or second link qualities in accordance with a determination that at least one candidate relay terminal device for a further communication between the terminal devices 110 and 120 is detected. Such a candidate relay terminal device may be detected if the terminal device 130 receives a discovery message from this candidate relay terminal device indicating that it is performing as a relay, or it can reach at least one of the terminal device 110 or 120.
  • the terminal device 120 may report the first information about the first and/or second link qualities periodically to the terminal device 110. In some embodiments, the terminal device 120 may report the first information about the first and/or second link qualities in response to a request from the terminal device 110. In some embodiments, the terminal device 120 may report the first information about the first and/or second link qualities in accordance with a determination that at least one candidate relay terminal device for a further communication between the terminal devices 110 and 120 is detected. Such a candidate relay terminal device may be detected if the terminal device 120 receives a discovery message from this candidate relay terminal device indicating that it is performing as a relay, or it can reach at least one of the terminal device 110 or 120. The detection of the candidate relay terminal device will be discussed in more details below.
  • the first information reported by the terminal device 130 or the terminal device 120 may indicate a candidate relay list comprising at least one candidate relay terminal device, e.g., one or more terminal devices 140 in FIG. 1.
  • the candidate relay list in the first information may further save the time for further measurements to detect candidate relay terminal devices and select therefrom a target relay terminal device.
  • the candidate relay list may include all candidate relay terminal devices detected by the terminal device 130 or the terminal device 120. In some embodiments, the candidate relay list may include a predetermined number of candidate relay terminal devices.
  • cone or more candidate relay terminal devices included in the candidate relay list may meet at least one of the following criterion as determined by the terminal device 130 or 120.
  • one or more candidate relay terminal devices neighbored to the terminal device 110 or the terminal device 120 may be included in the candidate relay list.
  • one or more candidate relay terminal devices neighbored to both the terminal device 110 and the terminal device 120 may be included in the candidate relay list.
  • a terminal device 140 may indicate in a discovery message (Model A procedure) or a response message to a solicitation message (Model B procedure) a list of terminal devices neighbored to this terminal device 140.
  • the terminal device 130 or 120 may then determine if the terminal device 110 and/or 120 are included in the list of neighbored terminal devices of the terminal device 140.
  • the terminal device 130 or 120 may include one or more candidate relay terminal devices in the candidate relay list that have a potential to act as a relay terminal device between the terminal devices 110 and 120.
  • one or more candidate relay terminal devices included in the candidate relay list may have link qualities with the terminal device 110 (referred to as third link qualities) that satisfy a specific condition (referred to as a fifth condition) .
  • one or more candidate relay terminal devices included in the candidate relay list may have link qualities with the terminal device 120 (referred to as fourth link qualities) that satisfy a specific condition (referred to as a sixth condition) .
  • one or more candidate relay terminal devices included in the candidate relay list may have link qualities with the terminal device 110 that satisfy the fifth condition and have link qualities with the terminal device 120 that satisfy the sixth condition.
  • the fifth condition may indicate that a third metric for a third link quality (e.g., PC5_RSRP_3) between a candidate relay terminal device and the terminal device 110 exceeds a seventh lower threshold (e.g., threshold_min_RSRP_7) . That is, a relay terminal device having a good link quality with the terminal device 110 may be included in the candidate relay list.
  • the fifth condition may indicate that the third metric for the third link quality (e.g., PC5_RSRP_3) between the candidate relay terminal device and the terminal device 110 is below a seventh upper threshold (e.g., threshold_max_RSRP_7) .
  • a link quality between the candidate relay terminal device and the terminal device 110 may not be too good to exceed the upper threshold.
  • the fifth condition may indicate that the third metric for the third link quality exceeds the seventh lower threshold and is below the seventh upper threshold, e.g., threshold_min_RSRP_7 ⁇ PC5_RSRP_3 ⁇ threshold_max_RSRP_7.
  • the fifth condition may indicate that a candidate relay terminal device may have a link quality with the terminal device 110 higher than the currently serving relay terminal device (i.e., the terminal device 130) .
  • the fifth condition may indicate that a first difference between the third link quality and the first link quality between the terminal devices 110 and 130 exceeds a first difference threshold, for example, PC5_RSRP_3 -PC5_RSRP_1>offset_1.
  • the sixth condition may indicate that a fourth metric for a fourth link quality (e.g., PC5_RSRP_4) between a candidate relay terminal device and the terminal device 120 exceeds an eighth lower threshold (e.g., threshold_min_RSRP_8) . That is, a relay terminal device having a good link quality with the terminal device 120 may be included in the candidate relay list.
  • the sixth condition may indicate that the fourth metric for the fourth link quality (e.g., PC5_RSRP_4) between the candidate relay terminal device and the terminal device 120 is below an eighth upper threshold (e.g., threshold_max_RSRP_8) .
  • a link quality between the candidate relay terminal device and the terminal device 120 may not be too good to exceed the upper threshold.
  • the sixth condition may indicate that the fourth metric for the fourth link quality exceeds the eighth lower threshold and is below the eighth upper threshold, e.g., threshold_min_RSRP_8 ⁇ PC5_RSRP_4 ⁇ threshold_max_RSRP_8.
  • the sixth condition may indicate that a candidate relay terminal device may have a link quality with the terminal device 120 higher than the currently serving relay terminal device (i.e., the terminal device 130) .
  • the sixth condition may indicate that a second difference between the fourth link quality and the second link quality between the terminal devices 120 and 130 exceeds a second difference threshold, for example, PC5_RSRP_4 -PC5_RSRP_2>offset_2.
  • the seventh lower threshold (e.g., threshold_min_RSRP_7) for a link quality between a candidate relay terminal device and the terminal device 110 may be the same as or different from the fifth lower threshold (e.g., threshold_min_RSRP_5) used by the terminal device 130 or 120 for comparing with the first link quality between the terminal device 110 and the terminal device 120.
  • the seventh upper threshold (e.g., threshold_max_RSRP_7) may be the same as or different from the fifth upper threshold (e.g., threshold_max_RSRP_5) used by the terminal device 130 or 120.
  • the eighth lower threshold (e.g., threshold_min_RSRP_8) for a link quality between a candidate relay terminal device and the terminal device 120 may be the same as or different from the sixth lower threshold (e.g., threshold_min_RSRP_6) used by the terminal device 130 or 120 for comparing with the second link quality between the terminal device 130 and the terminal device 120.
  • the eighth upper threshold (e.g., threshold_max_RSRP_8) may be the same as or different from the sixth upper threshold (e.g., threshold_max_RSRP_6) used by the terminal device 130 or 120.
  • the reporting of the first information may be triggered if the terminal device 130 or 120 detects a new relay terminal device. In some embodiments, the reporting of the first information may be triggered if the terminal device 130 or 120 detects a candidate relay terminal device that has a link quality better than the currently serving relay terminal device (i.e., the terminal device 130) as discussed above.
  • the terminal device 130 or 120 may use the configured thresholds. Otherwise, the terminal device 130 or 120 may the pre-configured thresholds or thresholds received via system information.
  • the first information may additionally or alternatively include an indication of relay reselection.
  • the terminal device 130 or 120 may determine, based on the monitored first link quality and/or second link quality, whether the relay reselection is to be performed for the communications between the terminal devices 110 and 120. The conditions for deciding the relay reselection may be similar as those used by the terminal device 110 as discussed above and may be configured or pre-configured to the terminal device 130 or 120 for use. If the terminal device 130 or 120 determine that the relay reselection is to be performed, it may include an indication of relay reselection in the first information. By receipt of such an indication of relay reselection, the terminal device 110 may make a final decision about the relay reselection or the fallback to the direct link.
  • the first information reported by the terminal device 130 or the terminal device 120 may further indicate the at least one link quality between the at least one candidate relay terminal device and the terminal device 110. In some embodiments, alternatively or in addition, the first information reported by the terminal device 130 or the terminal device 120 may further indicate at least one link quality between the at least one candidate relay terminal device and the terminal device 120.
  • the first information may include the specific metric (s) for the link qualities or may include quality indications indicating whether the link qualities of the candidate relay terminal devices exceeds certain lower thresholds and/or are below certain upper thresholds as indicated above.
  • contents comprised in the first information reported by the terminal device 130 or 120 may be configurable by the network device or other entities from the network side, by the terminal device 110, or by pre-configured.
  • the terminal device 130 if the terminal device 130 is configured to report the first information, it may also be configured with specified content comprised in the first information to be included.
  • the terminal device 130 or the terminal device 120 may be configured whether to report the specific metrics of the first link quality and/or the second link quality, or the quality indications about the comparison results with the corresponding upper and/or lower thresholds.
  • the terminal device 130 or the terminal device 120 may be configured whether or not to report the candidate relay list, and/or whether or not to report the link qualities of the candidate relay terminal devices. In some embodiments, the terminal device 130 and the terminal device 120 may be configured to report different contents in the first information. In some embodiments, the terminal device 130 or 120 may be configured with whether or not to report the first information. In some embodiments, for the terminal device 130, it may be further configured with reporting of the first information to at least one of the terminal device 110 or the terminal device 120.
  • the terminal device 130 may be configured to determine the first information for reporting in the case that the terminal device 130 is powered on. In some embodiments, the terminal device 130 may be configured to determine the first information for reporting if the terminal device 130 is determined to serve as a relay for the terminal devices 110 and 120. Alternatively or in addition, the terminal device 130 may be configured to determine the first information for reporting if the terminal device 130 is configured to report the first information, for example, configured by the terminal device 110 or the network device.
  • the decision about the relay reselection or the fallback to the direct link may be performed at the RRC layer of the terminal device 110.
  • the RRC layer of the terminal device 110 may decide the relay reselection base on the first link quality and/or the second link quality.
  • the RRC layer may then trigger transmission of a discovery message or a direct communication request (DCR) message or may trigger a relay reselection procedure.
  • the RRC layer may indicate to the upper layer that the relay reselection procedure is triggered.
  • the decision about the relay reselection or the fallback to the direct link may be performed at the upper layer of the terminal device 110, such as a PC5-S layer.
  • the RRC layer of the terminal device 110 may receive and report the first information to the upper layer for making the decision.
  • the upper layer may indicate the RRC layer to perform the relay reselection procedure, and/or trigger transmission of a discovery message or a DCR message.
  • the terminal device 110 may be configured to monitor and determine itself the first link quality between the terminal device 110 and 120 and determines the relay reselection and/or the fallback to the direct link based on the first link quality. In those embodiments, the terminal device 110 may or may not need the second link quality to make the decision.
  • the terminal device 120 may also be configured to perform a decision about relay reselection and/or the fallback to the direct link.
  • the information and/or configuration used to make the decision at the terminal device 120 may be similar as that made by those used at the terminal device 110.
  • the terminal device 130 and/or the terminal device 110 may report first information at least indicating the first link quality and/or the second link quality to the terminal device 120 for use in making the decision.
  • the terminal device 130 or 110 may transmit the first information to the terminal device 120 periodically or in response to a request from the terminal device 120.
  • the terminal device 120 may monitor and determine the second link quality between the terminal devices 130 and 120 and receive the first link quality from the terminal device 130 or the terminal device 110.
  • the network device 150 or other entity from the network side may transmit signaling to indicate whether the terminal device 110 and/or the terminal device 120 is to make a decision about the relay reselection and/or the fallback.
  • the terminal devices 110 and 120 may negotiates with each other which one is to make a decision about the relay reselection and/or the fallback.
  • the terminal device 130 may be indicated explicitly to which one or both of the terminal devices 110 and 120 the first information is to be reported. In some embodiments, the terminal device 130 may be indicated implicitly.
  • the terminal device 130 may report the first information to both the terminal devices 110 and 120. Otherwise, the terminal device 130 may report the first information to the indicated terminal device 110 or 120 for decision making, in order to save signaling overhead.
  • both the terminal devices 110 and 120 may trigger a direct communication request (DCR) procedure, as a normal procedure, the terminal device 110 may determine the relay reselection and sends a DCR message (DCR message_1) via the terminal device 130 or via a candidate relay terminal device (candidate Relay_1) .
  • the terminal device 120 may determine the relay reselection and sends a DCR message (DCR message_2) via the terminal device 130 or via another candidate relay terminal device (candidate Relay_2) .
  • the terminal device 120 receives the DCR message sent by the terminal device 110 (DCR message_1) via the terminal device 130 or candidate Relay_1.
  • the terminal device 110 receives the DCR message sent by the terminal device 120 (DCR message_2) via the terminal device 130 or candidate Relay_2.
  • the terminal device 110 may prevent the procedure if another DCR message is received (e.g., from the terminal device 120) .
  • the terminal device 110 may also prevent a further DCR to be formed if the DCR message is received. The same rule may be applied for the terminal device 120.
  • the first terminal devices 110 and 120 may perform the normal procedure as indicated above.
  • the terminal device 110 if sending of a discovery message for relay reselection is initiated or the discovery message is formed but not sent yet, the terminal device 110 may prevent a further discovery message to be sent.
  • the terminal device 110 may also prevent a further discovery message to be sent to the terminal device 120 if the discovery message is received. The same rule may be applied for the terminal device 120.
  • the terminal device 130 may be allowed to decide the relay reselection and/or link release for the terminal devices 110 and 120.
  • FIG. 5 and FIG. 6 illustrate such embodiments.
  • FIG. 5 illustrates a signaling flow 500 for communications in U2U relay according to some other example embodiments of the present disclosure.
  • the signaling flow 500 will be discussed with reference to FIG. 1.
  • the signaling flow 500 involves the terminal devices 110, 120, and 130 in FIG. 1.
  • the terminal devices involved in the signaling flow 500 may be any terminal devices in any suitable locations in the communication environment 100, within or out of coverage of the network devices 150. Only for the purpose of illustration, the terminal devices 110, 120, and 130 are referred for discussion. It is also to be understood that the signaling flow 500 may involves more devices in some embodiments as discussed below.
  • the terminal device 130 acts as a relay for communications between the terminal devices 110 and 120, so as to relay a communication (s) between the terminal devices 110 and 120.
  • the terminal device 130 may relay traffic, e.g., data, via E2E RB from the terminal device 110 to the terminal device 120 and/or vice versa.
  • the terminal device 130 determines (505) second information indicating at least one of the following: a first link quality between the terminal device 110 and terminal device 130, or a second link quality between the terminal device 130 and the terminal device 120.
  • the determination of the first link quality and/or the second link quality may be the same as discussed above.
  • the terminal device 130 may monitor and detect the first link quality and/or the second link quality itself.
  • the terminal device 130 may receive information about the first link quality and/or the second link quality from the terminal device 110 and/or the terminal device 130.
  • the terminal device 130 determines (510) , based at least in part on the second information, whether a relay reselection is to be triggered to reselect a further relay terminal device for a further communication between the first and second terminal devices.
  • the conditions for triggering the relay reselection may be the same as or similar to those conditions used by the terminal device 110 as discussed above. For example, if the terminal device 130 determines that it is no longer suitable to act as a relay for the terminal devices 110 and 120 or a better candidate relay terminal device is found, the terminal device 130 may determine to trigger the relay reselection.
  • the terminal device 130 transmits (515) a first indication of relay reselection to at least one of the terminal device 110 or the terminal device 120.
  • the terminal device 130 may transmit the first indication to both the terminal devices 110 and 120.
  • the first indication may conveyed via a RLC relay channel or via per-hop PC5 RRC signaling.
  • the terminal device 130 may report the first indication via (per-hop) L2 control information, such as RLC control PDU, MAC CE or the like.
  • the terminal device 130 may report the first indication to the terminal device 110 or 120 via (per-hop) L1 control information such as SCI.
  • the terminal devices 110 and/or 120 receive (520, 525) , from the terminal device 130, the first indication of relay reselection to reselect a further relay terminal device for a further communication between terminal device 110 and terminal device 120. In response to the first indication, the terminal devices 110 and/or 120 performs (530, 535) the relay reselection to reselect the further relay terminal device for a further communication between the terminal devices 110 and 120. As a result, the terminal devices 110 and 120 may continue their communications via the further relay terminal device.
  • FIG. 6 illustrates a signaling flow 600 for communications in U2U relay according to some further example embodiments of the present disclosure.
  • the signaling flow 600 involves the terminal devices 110, 120, and 130 in FIG. 1.
  • the terminal devices involved in the signaling flow 600 may be any terminal devices in any suitable locations in the communication environment 100, within or out of coverage of the network devices 150. Only for the purpose of illustration, the terminal devices 110, 120, and 130 are referred for discussion. It is also to be understood that the signaling flow 600 may involves more devices in some embodiments as discussed below.
  • the terminal device 130 acts as a relay for communications between the terminal devices 110 and 120, so as to relay a communication (s) between the terminal devices 110 and 120.
  • the terminal device 130 may relay traffic, e.g., data, via E2E RB from the terminal device 110 to the terminal device 120 and/or vice versa.
  • the terminal device 130 determines (605) second information indicating at least one of the following: a first link quality between the terminal device 110 and terminal device 130, or a second link quality between the terminal device 130 and the terminal device 120.
  • the determination of the first link quality and/or the second link quality may be the same as discussed above.
  • the terminal device 130 may monitor and detect the first link quality and/or the second link quality itself.
  • the terminal device 130 may receive information about the first link quality and/or the second link quality from the terminal device 110 and/or the terminal device 130.
  • the terminal device 130 determines (610) , based at least in part on the second information, that at least one of a first link between the first terminal device and the relay terminal device, or a second link between the relay terminal device and the second terminal device is to be released. In some embodiments, the terminal device 130 may determine if a relay reselection for the terminal devices 110 and 120 are needed and thus may determine to release at least one of the first and second links if the relay reselection is needed. In some embodiments, the terminal device 130 may determine if a fallback to a direct link between the terminal devices 110 and 120 are needed and thus may determine to release at least one of the first and second links if the fallback is needed.
  • the first link between the terminal devices 110 and 130 serves for communications with the terminal device 120 and other terminal device (s) , it may not be released in some cases.
  • the second link between the terminal devices 130 and 120 may serve for communications with the terminal device 110 and other terminal device (s) and thus may not be released in some cases.
  • the conditions related to the relay reselection may be the same as or similar to those conditions used by the terminal device 110 as discussed above.
  • the conditions related to the fallback may be the same as or similar to those conditions used by the terminal device 110 as discussed above. For example, if the terminal device 130 determines that it is no longer suitable to act as a relay for the terminal devices 110 and 120, a better candidate relay terminal device is found, and/or a direct link may be more suitable, then the terminal device 130 may determine to trigger the relay reselection.
  • the terminal device 130 may reuse the conditions related to the relay reselection and/or related to the fallback to the direct link to directly determine if the first link and/or the second link is unavailable and directly determine to release the first link and/or the second link.
  • the terminal device 130 may adopt new conditions (e.g., pre-configured or configured by the network side) to determine whether the first link and/or the second link is to be released. The scope of the present disclosure is not limited in this regard.
  • the terminal device 130 transmits (615) , to at least one of the terminal devices 110 and 120, a second indication of releasing at least one of the first link or the second link. Specifically, if the first link is to be released, a second indication of releasing the first link is transmitted to the terminal device 110. If the second link is to be released, a second indication of releasing the second link is transmitted to the terminal device 120. Alternatively, the terminal device 130 may release the first or the second link locally and may not transmit a second indication to either one of the terminal devices 110 and 120. Accordingly, the terminal devices 110 and/or 120 may rely on the legacy Radio Link Failure (RLF) mechanism or keep-alive mechanism to trigger the relay reselection and/or trigger the link release.
  • RLF Radio Link Failure
  • the second indication may conveyed to the terminal device 110 or 120 via a RLC relay channel or via per-hop PC5 RRC signaling.
  • the terminal device 130 may report the second indication via (per-hop) L2 control information, such as RLC control PDU, MAC CE or the like.
  • the terminal device 130 may report the second indication to the terminal device 110 or 120 via (per-hop) L1 control information such as SCI.
  • the terminal devices 110 and/or 120 may receive (620, 625) , from the terminal device 130, the second indication of releasing at least one of the first link or the second link. In response to the second indication, the terminal devices 110 and/or 120 release (630, 635) the first link or the second link with the terminal device 130. After the link is released, the terminal devices 110 and/or 120 may determine to establish relayed connections with a further relay terminal device, and/or to establish a direct link.
  • the terminal device 130 may transmit both the first indication and the second indication to the terminal devices 110 and/or 120.
  • FIG. 7 illustrates a flowchart of a communication method 700 implemented at a terminal device in accordance with some embodiments of the present disclosure.
  • the method 700 will be described from the perspective of a first terminal device, e.g., the terminal device 110 in FIG. 1.
  • the first terminal device receives, from a relay terminal device (e.g., the terminal device 130) or a second terminal device (e.g., the terminal device 120) , first information indicating at least one of the following: a first link quality between the first terminal device and the relay terminal device, or a second link quality between the relay terminal device and the second terminal device.
  • a communication between the first and second terminal devices is relayed by the relay terminal device.
  • the first terminal device performs, based at least in part on the first information, a decision about a relay reselection or a fallback to a direct link for a further communication between the first and second terminal devices.
  • performing the decision comprises performing the decision further based on at least one of a first configuration for the relay reselection or a second configuration for the fallback to the direct link.
  • the first configuration indicates at least one of a first condition for the first link quality or a second condition for the second link quality, the relay reselection being triggered by a satisfaction of at least one of the first link quality with the first condition or the second link quality with the second condition.
  • the second configuration indicates at least one of a third condition for the first link quality or a fourth condition for the second link quality, the fallback to the direct link being triggered by a satisfaction of at least one of the first link quality with the third condition or the second link quality with the fourth condition.
  • the first condition indicates at least one of the following: a first metric for the first link quality exceeds a first upper threshold, or the first metric for the first link quality is below a first lower threshold.
  • the second condition indicates at least one of the following: a second metric for the second link quality exceeds a second upper threshold, or the second metric for the second link quality is below a second lower threshold.
  • the third condition indicates that the first metric for the first link quality exceeds a third upper threshold.
  • the fourth condition indicates that a second metric for the second link quality exceeds a fourth upper threshold.
  • performing the decision comprises in accordance with a determination of a satisfaction of one of the first link quality with the first condition and the second link quality with the second condition, and a dissatisfaction of the other one of the first link quality with the first condition and the second link quality with the second condition, starting a predetermined timer; during running of the predetermined timer, performing at least one of the following: in accordance with a determination of both dissatisfactions of the first quality with the first condition and the second quality with the second condition, performing a decision not to trigger the relay reselection; or in accordance with a determination of both satisfactions of the first link quality with the first condition and the second link quality with the second condition, performing a decision to trigger the relay reselection.
  • performing the decision further comprises in accordance with a determination that the predetermined timer is expired and in accordance with a determination of the satisfaction of the one of the first link quality with the first condition and the second link quality with the second condition, perform a decision to trigger the relay reselection.
  • the first information comprises at least one of the following: a first metric for the first link quality, a first quality indication indicating whether the first metric exceeds a fifth upper threshold, a second quality indication indicating whether the first metric is below a fifth lower threshold, a second metric for the second link quality, a third quality indication indicating whether the second metric exceeds a sixth upper threshold, or a fourth quality indication indicating whether the second metric is below a sixth lower threshold.
  • the first information further indicates at least one of the following: a candidate relay list comprising at least one candidate relay terminal device, at least one link quality between the at least one candidate relay terminal device and the first terminal device, at least one link quality between the at least one candidate relay terminal device and the second terminal device, or an indication of relay reselection.
  • the candidate relay list comprises at least one of the following: a first candidate relay terminal device neighbored to the first terminal device, a second candidate relay terminal device neighbored to the second terminal device, a third candidate relay terminal device neighbored to both the first and second terminal devices, a fourth candidate relay terminal device having a third link quality with the first terminal device, the third link quality satisfying a fifth condition, or a fifth candidate relay terminal device having a fourth link quality with the second terminal device, the fourth link quality satisfying a sixth condition.
  • the fifth condition indicates at least one of the following: a third metric for the third link quality exceeds a seventh lower threshold, the third metric for the third link quality is below a seventh upper threshold, or a first difference between the third link quality and the first link quality exceeds a first difference threshold.
  • the sixth condition indicates at least one of the following: a fourth metric for the fourth link quality exceeds an eighth lower threshold, the fourth metric for the fourth link quality is below an eighth upper threshold, or a second difference between the fourth link quality and the second link quality exceeds a second difference threshold.
  • the first information is received from the second terminal device via: first per-hop signaling from the second terminal device to the relay terminal device and second per-hop signaling from the relay terminal device to the first terminal device, or end-to-end signaling from the second terminal device to the first terminal device.
  • the first terminal device is configured to trigger at least one of the relay reselection or the fallback to the direct link.
  • the decision about the relay reselection or the fallback to the direct link is performed at a radio resource control (RRC) layer of the first terminal device.
  • RRC radio resource control
  • the RRC layer reports the first information to an upper layer and the decision about the relay reselection or the fallback to the direct link is performed at the upper layer.
  • the second terminal device is allowed to trigger the relay reselection or the fallback to the direct link.
  • the method 700 further comprises: in accordance with a determination that a direct communication request (DCR) is received from the second terminal device for the fallback to the direct link, preventing a further DCR to be formed or to be sent to the second terminal device; and in accordance with a determination that a discovery message for the relay reselection is received from the second terminal device, preventing a further discovery message to be formed or to be sent to the second terminal device.
  • DCR direct communication request
  • FIG. 8 illustrates a flowchart of a communication method 800 implemented at a terminal device in accordance with some embodiments of the present disclosure.
  • the method 800 will be described from the perspective of a relay terminal device (e.g., the terminal device 130 in FIG. 1) or a second terminal device (e.g., the terminal device 120 in FIG. 1) .
  • the relay terminal device or the second terminal device determines first information indicating at least one of the following: a first link quality between a first terminal device (e.g., the terminal device 110 in FIG. 1) and the relay terminal device, or a second link quality between the relay terminal device and the second terminal device.
  • a communication between the first and second terminal devices is relayed by the relay terminal device.
  • the relay terminal device or the second terminal device transmits the first information to the first terminal device or the second terminal device.
  • the first information comprises at least one of the following: a first metric for the first link quality, a first quality indication indicating whether the first metric exceeds a fifth upper threshold, a second quality indication indicating whether the first metric is below a fifth lower threshold, a second metric for the second link quality, a third quality indication indicating whether the second metric exceeds a sixth upper threshold, or a fourth quality indication indicating whether the second metric is below a sixth lower threshold.
  • the first information further indicates at least one of the following: a candidate relay list comprising at least one candidate relay terminal device, at least one link quality between the at least one candidate relay terminal device and the first terminal device, at least one link quality between the at least one candidate relay terminal device and the second terminal device, or an indication of relay reselection.
  • the candidate relay list comprises at least one of the following: a first candidate relay terminal device neighbored to the first terminal device, a second candidate relay terminal device neighbored to the second terminal device, a third candidate relay terminal device neighbored to both the first and second terminal devices, a fourth candidate relay terminal device having a third link quality with the first terminal device, the third link quality satisfying a fifth condition, or a fifth candidate relay terminal device having a fourth link quality with the second terminal device, the fourth link quality satisfying a sixth condition.
  • the fifth condition indicates at least one of the following: a third metric for the third link quality exceeds a seventh lower threshold, the third metric for the third link quality is below a seventh upper threshold, or a first difference between the third link quality and the first link quality exceeds a first difference threshold.
  • the sixth condition indicates at least one of the following: a fourth metric for the fourth link quality exceeds an eighth lower threshold, the fourth metric for the fourth link quality is below an eighth upper threshold, or a second difference between the fourth link quality and the second link quality exceeds a second difference threshold.
  • the indication of relay reselection is determined based on at least one of the first link quality or the second link quality.
  • the method 800 is performed at the second terminal device, and wherein the first information is transmitted to the first terminal device via: first per-hop signaling from the second terminal device to the relay terminal device and second per-hop signaling from the relay terminal device to the first terminal device, or end-to-end signaling from the second terminal device to the first terminal device.
  • transmitting the first information comprises transmitting the first information in accordance with a determination of at least one of the following: a first metric for the first link quality exceeding a fifth upper threshold, the first metric for the first link quality being below a fifth lower threshold, a second metric for the second link quality exceeding a sixth upper threshold, or the second metric for the second link quality being below a sixth lower threshold.
  • the relay terminal device or the second terminal device is configured with a configuration indicating at least one of the fifth lower threshold, the fifth upper threshold, the sixth lower threshold, or the sixth upper threshold.
  • transmitting the first information comprises transmitting the first information in accordance with a determination that a candidate relay terminal device for a further communication between the first and second terminal devices is detected.
  • the method 800 is performed at the relay terminal device, and the first information is transmitted periodically or in response to a request from the at least one of the first terminal device or the second terminal device.
  • the method 800 is performed at second terminal device, and the first information is transmitted periodically or in response to a request from the first terminal device.
  • the method 800 is performed at the relay terminal device, and the relay terminal device is configured with at least one of the following: reporting of the first information to the at least one of the first terminal device and the second terminal device, or specified content comprised in the first information.
  • the method 800 is performed at the second terminal device, and the second terminal device is configured with at least one of the following: reporting of the first information to the first terminal device, or specified content comprised in the first information.
  • the method 800 is performed at the relay terminal device, and determining the first information comprises: determining the first information in accordance with a determination of at least one of the following: the relay terminal device being powered on, the relay terminal device is determined to serve as a relay for the first and second terminal devices, or the relay terminal device is configured to report the first information.
  • FIG. 9 illustrates a flowchart of a communication method 900 implemented at a terminal device in accordance with some embodiments of the present disclosure.
  • the method 900 will be described from the perspective of a relay terminal device, e.g., the terminal device 130 in FIG. 1.
  • the relay terminal device determines second information indicating at least one of the following: a first link quality between a first terminal device (e.g., the terminal device 110 in FIG. 1) and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device (e.g., the terminal device 120 in FIG. 1) .
  • a communication between the first and second terminal devices is relayed by the relay terminal device.
  • the relay terminal device determines, based at least in part on the second information, whether a relay reselection is to be triggered to reselect a further relay terminal device for a further communication between the first and second terminal devices.
  • the relay terminal device transmits a first indication of relay reselection to at least one of the first terminal device or the second terminal device.
  • FIG. 10 illustrates a flowchart of a communication method 1000 implemented at a terminal device in accordance with some embodiments of the present disclosure.
  • the method 1000 will be described from the perspective of a terminal device which communicate with a further terminal device via a relay terminal device.
  • a terminal device may include, for example, the terminal device 110 or 120 in FIG. 1.
  • the terminal device receives, from a relay terminal device (e.g., the terminal device 130) , a first indication of relay reselection to reselect a further relay terminal device for a further communication between a first terminal device and a second terminal device.
  • a relay terminal device e.g., the terminal device 130
  • a communication between the first and second terminal devices is relayed by the relay terminal device.
  • the terminal device performs the relay reselection to reselect the further relay terminal device for a further communication between the first and second terminal devices.
  • FIG. 11 illustrates a flowchart of a communication method 1100 implemented at a terminal device in accordance with some embodiments of the present disclosure.
  • the method 1100 will be described from the perspective of a relay terminal device, e.g., the terminal device 130 in FIG. 1.
  • the relay terminal device determines second information indicating at least one of the following: a first link quality between a first terminal device (e.g., the terminal device 110 in FIG. 1) and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device (e.g., the terminal device 120 in FIG. 1) .
  • a communication between the first and second terminal devices is relayed by the relay terminal device.
  • the relay terminal device determines, based at least in part on the second information, that at least one of a first link between the first terminal device and the relay terminal device, or a second link between the relay terminal device and the second terminal device is to be released.
  • the relay terminal device transmits, to at least one of the first terminal device or the second terminal device, a second indication of releasing at least one of the first link or the second link.
  • FIG. 12 illustrates a flowchart of a communication method 1200 implemented at a terminal device in accordance with some embodiments of the present disclosure.
  • the method 1200 will be described from the perspective of a terminal device which communicate with a further terminal device via a relay terminal device.
  • a terminal device may include, for example, the terminal device 110 or 120 in FIG. 1.
  • the terminal device receives, from a relay terminal device (e.g., the terminal device 130) , a second indication of releasing at least one of a first link between a first terminal device (e.g., the terminal device 110 in FIG. 1) and the relay terminal device, or a second link between the relay terminal device and a second terminal device (e.g., the terminal device 120 in FIG. 1) .
  • a relay terminal device e.g., the terminal device 130
  • the terminal device releases the first link or the second link with the relay terminal device.
  • FIG. 13 is a simplified block diagram of a device 1300 that is suitable for implementing embodiments of the present disclosure.
  • the device 1300 can be considered as a further example implementation of any of the devices as shown in FIG. 1. Accordingly, the device 1300 can be implemented at or as at least a part of a terminal device 110, 120, 130, 140 or a network device 150.
  • the device 1300 includes a processor 1310, a memory 1320 coupled to the processor 1310, a suitable transmitter (TX) /receiver (RX) 1340 coupled to the processor 1310, and a communication interface coupled to the TX/RX 1340.
  • the memory 1310 stores at least a part of a program 1330.
  • the TX/RX 1340 is for bidirectional communications.
  • the TX/RX 1340 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones.
  • the communication interface may represent any interface that is necessary for communication with other network elements, such as X2/Xn interface for bidirectional communications between eNBs/gNBs, S1/NG interface for communication between a Mobility Management Entity (MME) /Access and Mobility Management Function (AMF) /SGW/UPF and the eNB/gNB, Un interface for communication between the eNB/gNB and a relay node (RN) , or Uu interface for communication between the eNB/gNB and a terminal device.
  • MME Mobility Management Entity
  • AMF Access and Mobility Management Function
  • RN relay node
  • Uu interface for communication between the eNB/gNB and a terminal device.
  • the program 1330 is assumed to include program instructions that, when executed by the associated processor 1310, enable the device 1300 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to FIGS. 1 to 11.
  • the embodiments herein may be implemented by computer software executable by the processor 1310 of the device 1300, or by hardware, or by a combination of software and hardware.
  • the processor 1310 may be configured to implement various embodiments of the present disclosure.
  • a combination of the processor 1310 and memory 1320 may form processing means 1350 adapted to implement various embodiments of the present disclosure.
  • the memory 1320 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 1320 is shown in the device 1300, there may be several physically distinct memory modules in the device 1300.
  • the processor 1310 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples.
  • the device 1300 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.
  • a terminal device comprises a circuitry configured to: receive, from a relay terminal device or a second terminal device, first information indicating at least one of the following: a first link quality between the first terminal device and the relay terminal device, or a second link quality between the relay terminal device and the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and perform, based at least in part on the first information, a decision about a relay reselection or a fallback to a direct link for a further communication between the first and second terminal devices.
  • the circuitry may be configured to perform any of the method implemented by the terminal device as discussed above.
  • a terminal device comprises a circuitry configured to: determine first information indicating at least one of the following: a first link quality between a first terminal device and a relay terminal device, or a second link quality between the relay terminal device and a second terminal device, the terminal device comprising the relay terminal device or the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and transmit the first information to the first terminal device or the second terminal device.
  • the circuitry may be configured to perform any of the method implemented by the terminal device as discussed above.
  • a relay terminal device comprises a circuitry configured to:determine second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determine, based at least in part on the second information, whether a relay reselection is to be triggered to reselect a further relay terminal device for a further communication between the first and second terminal devices; and in accordance with a determination that the relay reselection is to be triggered, transmit a first indication of relay reselection to at least one of the first terminal device or the second terminal device.
  • the circuitry may be configured to perform any of the method implemented by the relay terminal device as discussed above.
  • a relay terminal device comprises a circuitry configured to: determine second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determine, based at least in part on the second information, that at least one of a first link between the first terminal device and the relay terminal device, or a second link between the relay terminal device and the second terminal device is to be released; and transmit, to at least one of the first terminal device or the second terminal device, a second indication of releasing at least one of the first link or the second link.
  • the circuitry may be configured to perform any of the method implemented by the relay terminal device as discussed above.
  • a terminal device comprises a circuitry configured to: receive, from a relay terminal device, a first indication of relay reselection to reselect a further relay terminal device for a further communication between a first terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and in response to the first indication, perform the relay reselection to reselect the further relay terminal device for a further communication between the first and second terminal devices.
  • the circuitry may be configured to perform any of the method implemented by relay terminal device as discussed above.
  • a terminal device comprises a circuitry configured to: receive, from a relay terminal device, a second indication of releasing at least one of a first link between a first terminal device and the relay terminal device, or a second link between the relay terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device; and in response to the second indication, release the first link or the second link with the relay terminal device.
  • the circuitry may be configured to perform any of the method implemented by relay terminal device as discussed above.
  • circuitry used herein may refer to hardware circuits and/or combinations of hardware circuits and software.
  • the circuitry may be a combination of analog and/or digital hardware circuits with software/firmware.
  • the circuitry may be any portions of hardware processors with software including digital signal processor (s) , software, and memory (ies) that work together to cause an apparatus, such as a terminal device or a network device, to perform various functions.
  • the circuitry may be hardware circuits and or processors, such as a microprocessor or a portion of a microprocessor, that requires software/firmware for operation, but the software may not be present when it is not needed for operation.
  • the term circuitry also covers an implementation of merely a hardware circuit or processor (s) or a portion of a hardware circuit or processor (s) and its (or their) accompanying software and/or firmware.
  • embodiments of the present disclosure provide the following aspects.
  • a first terminal device comprises: a processor configured to cause the first terminal device to: receive, from a relay terminal device or a second terminal device, first information indicating at least one of the following: a first link quality between the first terminal device and the relay terminal device, or a second link quality between the relay terminal device and the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and perform, based at least in part on the first information, a decision about a relay reselection or a fallback to a direct link for a further communication between the first and second terminal devices.
  • the processor is further configured to cause the first terminal device to: perform the decision further based on at least one of a first configuration for the relay reselection or a second configuration for the fallback to the direct link, wherein the first configuration indicates at least one of a first condition for the first link quality or a second condition for the second link quality, the relay reselection being triggered by a satisfaction of at least one of the first link quality with the first condition or the second link quality with the second condition, and wherein the second configuration indicates at least one of a third condition for the first link quality or a fourth condition for the second link quality, the fallback to the direct link being triggered by a satisfaction of at least one of the first link quality with the third condition or the second link quality with the fourth condition.
  • the first condition indicates at least one of the following: a first metric for the first link quality exceeds a first upper threshold, or the first metric for the first link quality is below a first lower threshold.
  • the second condition indicates at least one of the following: a second metric for the second link quality exceeds a second upper threshold, or the second metric for the second link quality is below a second lower threshold.
  • the third condition indicates that the first metric for the first link quality exceeds a third upper threshold.
  • the fourth condition indicates that a second metric for the second link quality exceeds a fourth upper threshold.
  • the processor is further configured to cause the first terminal device to: in accordance with a determination of a satisfaction of one of the first link quality with the first condition and the second link quality with the second condition, and a dissatisfaction of the other one of the first link quality with the first condition and the second link quality with the second condition, start a predetermined timer; during running of the predetermined timer, perform at least one of the following: in accordance with a determination of both dissatisfactions of the first quality with the first condition and the second quality with the second condition, performing a decision not to trigger the relay reselection; or in accordance with a determination of both satisfactions of the first link quality with the first condition and the second link quality with the second condition, performing a decision to trigger the relay reselection; and in accordance with a determination that the predetermined timer is expired and in accordance with a determination of the satisfaction of the one of the first link quality with the first condition and the second link quality with the second condition, perform a decision
  • the first information comprises at least one of the following: a first metric for the first link quality, a first quality indication indicating whether the first metric exceeds a fifth upper threshold, a second quality indication indicating whether the first metric is below a fifth lower threshold, a second metric for the second link quality, a third quality indication indicating whether the second metric exceeds a sixth upper threshold, or a fourth quality indication indicating whether the second metric is below a sixth lower threshold.
  • the first information further indicates at least one of the following: a candidate relay list comprising at least one candidate relay terminal device, at least one link quality between the at least one candidate relay terminal device and the first terminal device, at least one link quality between the at least one candidate relay terminal device and the second terminal device, or an indication of relay reselection.
  • the candidate relay list comprises at least one of the following: a first candidate relay terminal device neighbored to the first terminal device, a second candidate relay terminal device neighbored to the second terminal device, a third candidate relay terminal device neighbored to both the first and second terminal devices, a fourth candidate relay terminal device having a third link quality with the first terminal device, the third link quality satisfying a fifth condition, or a fifth candidate relay terminal device having a fourth link quality with the second terminal device, the fourth link quality satisfying a sixth condition.
  • the fifth condition indicates at least one of the following: a third metric for the third link quality exceeds a seventh lower threshold, the third metric for the third link quality is below a seventh upper threshold, or a first difference between the third link quality and the first link quality exceeds a first difference threshold.
  • the sixth condition indicates at least one of the following: a fourth metric for the fourth link quality exceeds an eighth lower threshold, the fourth metric for the fourth link quality is below an eighth upper threshold, or a second difference between the fourth link quality and the second link quality exceeds a second difference threshold.
  • the first information is received from the second terminal device via: first per-hop signaling from the second terminal device to the relay terminal device and second per-hop signaling from the relay terminal device to the first terminal device, or end-to-end signaling from the second terminal device to the first terminal device.
  • the first terminal device is configured to trigger at least one of the relay reselection or the fallback to the direct link.
  • the decision about the relay reselection or the fallback to the direct link is performed at a radio resource control (RRC) layer of the first terminal device.
  • RRC radio resource control
  • the RRC layer reports the first information to an upper layer and the decision about the relay reselection or the fallback to the direct link is performed at the upper layer.
  • the second terminal device is allowed to trigger the relay reselection or the fallback to the direct link
  • the processor is further configured to: in accordance with a determination that a direct communication request (DCR) is received from the second terminal device for the fallback to the direct link, prevent a further DCR to be formed or to be sent to the second terminal device; and in accordance with a determination that a discovery message for the relay reselection is received from the second terminal device, prevent a further discovery message to be formed or to be sent to the second terminal device.
  • DCR direct communication request
  • a terminal device comprises: a processor configured to cause the terminal device to: determine first information indicating at least one of the following: a first link quality between a first terminal device and a relay terminal device, or a second link quality between the relay terminal device and a second terminal device, the terminal device comprising the relay terminal device or the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and transmit the first information to the first terminal device or the second terminal device.
  • the first information comprises at least one of the following: a first metric for the first link quality, a first quality indication indicating whether the first metric exceeds a fifth upper threshold, a second quality indication indicating whether the first metric is below a fifth lower threshold, a second metric for the second link quality, a third quality indication indicating whether the second metric exceeds a sixth upper threshold, or a fourth quality indication indicating whether the second metric is below a sixth lower threshold.
  • the first information further indicates at least one of the following: a candidate relay list comprising at least one candidate relay terminal device, at least one link quality between the at least one candidate relay terminal device and the first terminal device, at least one link quality between the at least one candidate relay terminal device and the second terminal device, or an indication of relay reselection.
  • the candidate relay list comprises at least one of the following: a first candidate relay terminal device neighbored to the first terminal device, a second candidate relay terminal device neighbored to the second terminal device, a third candidate relay terminal device neighbored to both the first and second terminal devices, a fourth candidate relay terminal device having a third link quality with the first terminal device, the third link quality satisfying a fifth condition, or a fifth candidate relay terminal device having a fourth link quality with the second terminal device, the fourth link quality satisfying a sixth condition.
  • the fifth condition indicates at least one of the following: a third metric for the third link quality exceeds a seventh lower threshold, the third metric for the third link quality is below a seventh upper threshold, or a first difference between the third link quality and the first link quality exceeds a first difference threshold.
  • the sixth condition indicates at least one of the following: a fourth metric for the fourth link quality exceeds an eighth lower threshold, the fourth metric for the fourth link quality is below an eighth upper threshold, or a second difference between the fourth link quality and the second link quality exceeds a second difference threshold.
  • the indication of relay reselection is determined based on at least one of the first link quality or the second link quality.
  • the terminal device comprises the second terminal device, and wherein the first information is transmitted to the first terminal device via: first per-hop signaling from the second terminal device to the relay terminal device and second per-hop signaling from the relay terminal device to the first terminal device, or end-to-end signaling from the second terminal device to the first terminal device.
  • the processor is further configured to cause the terminal device to: transmit the first information in accordance with a determination of at least one of the following: a first metric for the first link quality exceeding a fifth upper threshold, the first metric for the first link quality being below a fifth lower threshold, a second metric for the second link quality exceeding a sixth upper threshold, or the second metric for the second link quality being below a sixth lower threshold.
  • the terminal device is configured with a configuration indicating at least one of the fifth lower threshold, the fifth upper threshold, the sixth lower threshold, or the sixth upper threshold.
  • the processor is further configured to cause the terminal device to: transmit the first information in accordance with a determination that a candidate relay terminal device for a further communication between the first and second terminal devices is detected.
  • the terminal device comprises the relay terminal device, and the first information is transmitted periodically or in response to a request from the at least one of the first terminal device or the second terminal device. In some embodiments of the second aspect, the terminal device comprises the second terminal device, and the first information is transmitted periodically or in response to a request from the first terminal device.
  • the terminal device comprises the relay terminal device, and the relay terminal device is configured with at least one of the following: reporting of the first information to the at least one of the first terminal device and the second terminal device, or specified content comprised in the first information.
  • the terminal device comprises the second terminal device, and the second terminal device is configured with at least one of the following: reporting of the first information to the first terminal device, or specified content comprised in the first information.
  • the terminal device comprises the relay terminal device
  • the processor is further configured to: determine the first information in accordance with a determination of at least one of the following: the relay terminal device being powered on, the relay terminal device is determined to serve as a relay for the first and second terminal devices, or the relay terminal device is configured to report the first information.
  • a relay terminal device comprises: a processor configured to cause the device to: determine second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determine, based at least in part on the second information, whether a relay reselection is to be triggered to reselect a further relay terminal device for a further communication between the first and second terminal devices; and in accordance with a determination that the relay reselection is to be triggered, transmit a first indication of relay reselection to at least one of the first terminal device or the second terminal device.
  • a relay terminal device comprises: a processor configured to cause the device to: determine second information indicating at least one of the following: a first link quality between a first terminal device and the relay terminal device, or a second link quality between the relay terminal device and a second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; determine, based at least in part on the second information, that at least one of a first link between the first terminal device and the relay terminal device, or a second link between the relay terminal device and the second terminal device is to be released; and transmit, to at least one of the first terminal device or the second terminal device, a second indication of releasing at least one of the first link or the second link.
  • a terminal device comprises: a processor configured to cause the device to: receive, from a relay terminal device, a first indication of relay reselection to reselect a further relay terminal device for a further communication between a first terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device, wherein a communication between the first and second terminal devices is relayed by the relay terminal device; and in response to the first indication, perform the relay reselection to reselect the further relay terminal device for a further communication between the first and second terminal devices.
  • a terminal device comprises: a processor configured to cause the device to: receive, from a relay terminal device, a second indication of releasing at least one of a first link between a first terminal device and the relay terminal device, or a second link between the relay terminal device and a second terminal device, the terminal device comprising the first terminal device or the second terminal device; and in response to the second indication, release the first link or the second link with the relay terminal device.
  • a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform any of the methods implemented by a terminal device discussed above.
  • a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform any of the methods implemented by the terminal device discussed above.
  • various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
  • the present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium.
  • the computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to FIGS. 3 and 7 to 11.
  • program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types.
  • the functionality of the program modules may be combined or split between program modules as desired in various embodiments.
  • Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.
  • Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented.
  • the program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.
  • the above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.
  • the machine readable medium may be a machine readable signal medium or a machine readable storage medium.
  • a machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.
  • machine readable storage medium More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
  • RAM random access memory
  • ROM read-only memory
  • EPROM or Flash memory erasable programmable read-only memory
  • CD-ROM portable compact disc read-only memory
  • magnetic storage device or any suitable combination of the foregoing.

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  • Mobile Radio Communication Systems (AREA)

Abstract

Des modes de réalisation donnés à titre d'exemple de la présente divulgation concernent des solutions de resélection de relais et de repli vers une liaison directe d'un relais d'équipement utilisateur (UE) à UE. Dans une solution, un premier dispositif terminal reçoit, en provenance d'un dispositif terminal relais ou d'un second dispositif terminal, des premières informations indiquant au moins l'un des éléments suivants : une première qualité de liaison entre le premier dispositif terminal et le dispositif terminal relais, ou une seconde qualité de liaison entre le dispositif terminal relais et le second dispositif terminal, une communication entre les premier et second dispositifs terminaux étant relayée par le dispositif terminal relais. Le premier dispositif terminal exécute, sur la base, au moins en partie, des premières informations, une décision concernant une resélection de relais ou un repli vers une liaison directe pour une communication supplémentaire entre les premier et second dispositifs terminaux.
PCT/CN2022/138107 2022-12-09 2022-12-09 Dispositifs et procédés de communication WO2024119510A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105451282A (zh) * 2014-08-22 2016-03-30 电信科学技术研究院 一种中继终端重选的方法及设备
US20180152234A1 (en) * 2015-05-15 2018-05-31 Zte Corporation Method and system for replacing relay, d2d user equipment and control node
CN110461020A (zh) * 2019-08-16 2019-11-15 展讯通信（上海）有限公司 用于辅链路的中继选择方法及装置、存储介质、终端

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105451282A (zh) * 2014-08-22 2016-03-30 电信科学技术研究院 一种中继终端重选的方法及设备
US20180152234A1 (en) * 2015-05-15 2018-05-31 Zte Corporation Method and system for replacing relay, d2d user equipment and control node
CN110461020A (zh) * 2019-08-16 2019-11-15 展讯通信（上海）有限公司 用于辅链路的中继选择方法及装置、存储介质、终端

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