WO2024108547A1

WO2024108547A1 - Enhancement on user activity detection

Info

Publication number: WO2024108547A1
Application number: PCT/CN2022/134352
Authority: WO
Inventors: Haiyou Guo
Original assignee: Nokia Shanghai Bell Co., Ltd.
Priority date: 2022-11-25
Filing date: 2022-11-25
Publication date: 2024-05-30

Abstract

Example embodiments of the present disclosure relate to user activity detection (UAD). A terminal device in a radio access network receives, from a network device in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences. Encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices. The terminal device transmits, to the network device, an encoded conjugated symmetric sequence in the common time-frequency resource. By utilizing the conjugated symmetric sequence with partial phase compensation, a synchronous UAD can be supported with massive capacity and scalability for massive accesses.

Description

ENHANCEMENT ON USER ACTIVITY DETECTION

FIELD

Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for user activity detection (UAD) .

BACKGROUND

Machine Type Communication (MTC) in 5G New Radio is split into Ultra Reliable Low Latency Communications (URLLC) , or critical MTC (cMTC) , in controlled environments with small-payloads and low-data rates, and massive MTC (mMTC) for large or dense deployments with sporadic traffic patterns. In the coming decade, owing to emerging industrial use cases and the verticalization of the service provision, these two domains will develop into several specialized subclasses, hence demanding multi-dimensional optimization and scalable designs.

In view of the above, 6G needs to serve highly diverse applications ranging from data-rate hungry holographic images and connected 360 XR (e.g., augmented/virtual/mixed reality) to massive access for various types of IoT devices. One of MTC service classes for 6G is proposed to be classified as scalable cMTC, which refers to supporting massive connectivity with high reliability and low latency, e.g., critical medical monitoring and factory automation. Scale and flexibility are also important measures for 6G performance. 6G is expected to support as high connection density as 10 million devices per square kilometers.

SUMMARY

In general, example embodiments of the present disclosure provide a solution of UAD enhancements.

In a first aspect of the present disclosure, there is provided a terminal device in a radio access network. The terminal device comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the terminal device at least to: receive, from a network device in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; and transmit, to the network device, an encoded conjugated symmetric sequence in the common time-frequency resource.

In a second aspect of the present disclosure, there is provided a network device in a radio access network. The network device comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network device at least to: transmit to a set of terminal devices in the radio access network, a configuration assigning a common time-frequency resource for the set of terminal devices and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; receive a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of terminal devices; and identify the set of active terminal devices out of the set of terminal devices by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.

In a third aspect of the present disclosure, there is provided a method. The method comprises: receiving, at a terminal device in a radio access network and from a network device in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; and transmitting, to the network device, an encoded conjugated symmetric sequence in the common time-frequency resource.

In a fourth aspect of the present disclosure, there is provided a method. The method comprises: transmitting, at a network device in a radio access network and to a set of terminal devices in the radio access network, a configuration assigning a common time-frequency resource for the set of terminal devices and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; receiving a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of terminal devices; and identifying the set of active terminal devices out of the set of terminal devices by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.

In a fifth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises: means for receiving, at the first apparatus in a radio access network and from a network device in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; and means for transmitting, to the network device, an encoded conjugated symmetric sequence in the common time-frequency resource.

In a sixth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises: means for transmitting, at the second apparatus in a radio access network and to a set of terminal devices in the radio access network, a configuration assigning a common time-frequency resource for the set of terminal devices and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; means for receiving a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of terminal devices; and means for identifying the set of active terminal devices out of the set of terminal devices by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.

In a seventh aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises program instructions for causing an apparatus to perform at least the following: receiving, at a terminal device in a radio access network and from a network device in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; and transmitting, to the network device, an encoded conjugated symmetric sequence in the common time-frequency resource.

In an eighth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises program instructions for causing an apparatus to perform at least the following: transmitting, at a network device in a radio access network and to a set of terminal devices in the radio access network, a configuration assigning a common time-frequency resource for the set of terminal devices and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; receiving a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of terminal devices; and identifying the set of active terminal devices out of the set of terminal devices by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.

It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, where:

FIG. 1 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

FIG. 2 illustrates a signaling chart for a synchronous UAD process according to some example embodiments of the present disclosure;

FIG. 3 illustrates a schematic diagram of resource mapping for conjugated symmetric sequence with partial phase compensation according to some example embodiments of the present disclosure;

FIG. 4 illustrates example simulation results of performance comparison on UAD according to some example embodiments of the present disclosure;

FIG. 5 illustrates a flowchart of a method implemented at a terminal device according to some example embodiments of the present disclosure;

FIG. 6 illustrates a flowchart of a method implemented at a network device according to some example embodiments of the present disclosure;

FIG. 7 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

FIG. 8 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish functionalities of various elements. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used herein, “at least one of the following: <a list of two or more elements> and “at least one of <a list of two or more elements> and similar wording, where the list of two or more elements are joined by “and” or “or” , means at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as fifth generation (5G) systems, Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, 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) new radio (NR) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a Next Generation NodeB (NR NB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , Integrated Access and Backhaul (IAB) node, a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology. The network device is allowed to be defined as part of a gNB such as for example in CU/DU split in which case the network device is defined to be either a gNB-CU or a gNB-DU.

As used herein, the term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. The terminal device may also correspond to Mobile Termination (MT) part of the integrated access and backhaul (IAB) node (a.k.a. a relay node) . In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably. In the following description, the terms “sequence” , “preamble” , “pilot signal” and “signal” may be used interchangeably.

As used herein, the term “active terminal device” or “active UE” refers to a terminal device that becomes active at one or more slot, and raises a service requesting flag, for example, a scheduling request for data awaiting transmissions, a position request, connection-state establishment request, or a retransmission request related to negative acknowledgment (NAK) in ARQ (Automatic Repeat-reQuest) protocol. Additionally, the term “inactive terminal device” or “inactive UE” refers to a terminal device that refrains from operations by the “active terminal device” or “active UE” and keep silence at one or more slot.

Although functionalities described herein can be performed, in various example embodiments, in a fixed and/or a wireless network node, in other example embodiments, functionalities may be implemented in a user equipment apparatus (such as a cell phone or tablet computer or laptop computer or desktop computer or mobile IoT device or fixed IoT device) . This user equipment apparatus can, for example, be furnished with corresponding capabilities as described in connection with the fixed and/or the wireless network node (s) , as appropriate. The user equipment apparatus may be the user equipment and/or or a control device, such as a chipset or processor, configured to control the user equipment when installed therein. Examples of such functionalities include the bootstrapping server function and/or the home subscriber server, which may be implemented in the user equipment apparatus by providing the user equipment apparatus with software configured to cause the user equipment apparatus to perform from the point of view of these functions/nodes.

As opposed to human-centric communications, machine-centric communications (e.g., scalable cMTC) generally possesses two distinctive features:

● The overall system needs to support massive connectivity-the number of devices connected to a cellular BS may be in the order of 10 ⁴ to 10 ⁷. The macro BS prefers to provide a unified massive access for various types of IoT devices, offering a low-cost solution for supporting massive connectivity with high reliability and low latency. Commercially, the telecommunication vendors favor a unified solution.

● The traffic pattern is sporadic-at any given time only a small fraction of potential devices is active. Typically, the machine-type devices connect asynchronously and sporadically to a network to send small data payloads. The sporadicity is due to the inherent burstiness of event driven IoT communications in controlled and/or sensing environments. Most of devices make random requests independently, less periodicity can be tracked and utilized. As such, it is impossible for the network to predict when and which device will deliver packet in advance.

In 6G MTC, the massive devices raise the sporadic but unpredictable scheduling requests to ask for uplink resources from the uplink scheduler. The scheduling request is a flag indicating that a device needs uplink resources for uplink shared channel (UL-SCH) transmission. There are two ways to issue the flag in LTE and NR as follows.

● For a device which has been configured with dedicated request resource, the scheduling request is usually transmitted on the (Physical Uplink Control Channel (PUCCH) using preconfigured and periodically reoccurring PUCCH resources dedicated to the device. Each device can be assigned with dedicated PUCCH scheduling request resources with a periodicity ranging from every second OFDM symbol to support very latency-critical services up to every 80 ms for low overhead. However, such a resource configuration becomes unsustainable as connection density increases to 10 million devices per square kilometers, coming at the unacceptable waste in spectrum. It is not wise to maintain the dedicated PUCCH simultaneously for the massive devices with low traffic intensity.

● For a device which has not been configured with scheduling request resources, it relies on the random-access mechanism to request resources. This can be used to create a contention-based mechanism for requesting resources. As an example of the classic ALOHA, however, the Physical Layer Random Access Channel (PRACH) mechanism imposes a limit on the number of active devices that are granted to access the network.

For these reasons, both methods may be infeasible for the scalable cMTC. Instead of them, UAD acts as a more efficient and effective way to manage with the uncertain and random scheduling requests. In fact, there is a small subset of devices being active for scheduling requests at a given transmission instant or frame. UAD helps the BS to identify the active subset out of the entire devices, prior to building successful connections between the devices and the BS. Once the BS knows which device (s) has an actual demand of data delivery at the beginning of one transmission cycle, the BS can assign the small number of active users with the scheduling grant, so that the active users can further provide more detailed scheduling information to the BS. An eligible UAD for massive access is expected be accurate, fast, and scalable at the minimum cost of measurement resource.

Although the subset of active users is random and unknown, on the other hand, they might have established a connection-like state through the initial access procedure. Except for the dedicated UL control channel for scheduling request, the users may has received necessary configurations, such as, system information, registered user ID, synchronized uplink timing, etc., and obtained a partial knowledge of the respective UL channel, which allows for a synchronous UAD with high accuracy.

According to some example embodiments of the present disclosure, there is provided a solution of UAD and a sequence design for the synchronous UAD. In this solution, terminal devices (e.g., UE) in a radio access network are pre-assigned with conjugated symmetric sequences respectively, and the symmetric sequences can be distinguished with associated frequency parameters. The active terminal devices transmit the associated conjugated symmetric sequences encoded with partial phase compensation on a common resource, respectively. A network device (e.g., gNB) can identify the active terminal devices out of the terminal devices by solving activity indicating symbols from a superimposed conjugated symmetric sequence in the common resource.

In this way, synchronous UAD is supported in the radio access network, which realizes a fast and effective active-user identification. The synchronous UAD can be readily integrated with the scheduling request-grant procedure for massive access, thus facilitating a low-cost and high-performance scheduling request-grant procedure. Also, the synchronous UAD can be readily integrated with ARQ protocol, thus avoiding the dedicated feedback channel for ACK/NAK and reducing the signaling overhead.

Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

Example Environment

FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. The communication environment 100 may be a radio access network. As shown in FIG. 1, the communication environment 100 includes a set of terminal devices 110-1 to 110-N and a network device 120, where N represents the number of the terminal devices 110-1 to 110-N, which may be collectively referred to as terminal device 110 hereinafter.

The set of terminal devices 110-1 to 110-N may be potential user devices (e.g., UEs) with sporadic traffic (e.g., NAK message in ARQ protocol) in a cell provided by the network device 120 (e.g., gNB) . The terminal device 110 and the network device 120 may communicate with each other. In the context of the present disclosure, a link from the terminal device 110 to the network device 120 is referred to as an uplink (UL) , while a link from the network device 120 to the terminal device 110 is referred to as a downlink (DL) . In UL, the terminal device 110 is a transmitting (Tx) device or a transmitter, and the network device 120 is a receiving (Rx) device or a receiver. In DL, the network device 120 is the Tx device or the transmitter, and the terminal device 110 is the Rx device or the receiver.

As an example of the implementations, network device 120 and each of the terminal devices 110-1 to 110-N may have a single or multiple transmit antenna. The set of terminal devices 110-1 to 110-N may be labelled by n∈S= {1, …, N} , respectively. Suppose that N terminal devices 110 have carried out the initial access procedure through previous random-access procedure, which establishes a connection-like state except for a dedicated UL control channel for the scheduling request. Accordingly, the terminal device 110 may have received necessary configurations, such as, system information, registered user ID, synchronized uplink timing, etc., and obtained a prior knowledge of the respective UL channel. The timing alignment information is assumed to be valid during the procedure of UAD, which is not outdated for static and low-mobility UEs. As such, the terminal device 110 can appropriately adjust their timing advance for UL transmissions, respectively, and enable a synchronous UL transmission with respect to reception window at the network device 120.

Each of the terminal devices 110-1 to 110-N is preassigned with a unique preamble used for all the time slots. This preamble may serve as the ID for a corresponding user, and thus it can be used for UAD. In particular, at each time slot, the network device 120 may detect at least one active terminal device by detecting which preamble (s) is present. In other words, such a preamble is exclusive for each terminal device 110. Generally, at a given slot, only a small fraction of potential devices, denoted by an active subset

become active and raise scheduling request for UL data awaiting transmission. The active subset S _A refers to as the set of active terminal devices, which is random and unknown for the network device 120. By way of example, in the example shown in FIG. 1, the active subset S _A includes the terminal devices 110-1, 110-n and 110-N, while the terminal devices 110-2 and 110-3 are inactive terminal devices.

In some example embodiments, the preamble may be in a form of a conjugated symmetric sequence that is a complex conjugated symmetric sinusoid sequence with a variable frequency parameter. The conjugated symmetric sequences associated with the set of terminal devices 110-1 to 110-N can be nonorthogonal complex conjugated symmetric sinusoid sequences, and different terminal devices can be discriminated by the distinct frequency parameter for avoiding preamble collision. Such a sequence design can facilitate convex signal processing to overcome the multi-user interference, thus realizing an efficient and accurate UAD.

In a case where the terminal device 110-n becomes an active terminal device, i.e.,

it will transmit the conjugated symmetric sequence encoded with a partial phase compensation to the network device 120. In other words, encoded transmission of a conjugated symmetric sequence indicates activity information of an active terminal device out of the entire set of terminal devices.

To carry out the UAD, the network device 120 may configure a common time- frequency resource, for example, a Physical Resource Block (PRB) for all N terminal devices 110 for transmission of the respective sequence or its variant. The shared PRB may comprise a plurality of resource elements (REs) in a coherence block, and each RE bears one symbol of conjugated symmetric sequence. The number of the REs may be determined based on an expected number of active devices which may be derived from the total number of the terminal device 110 and the probabilistic characteristics of traffics. For the case of multiple-antenna deployment, the common time-frequency resource may be based on a common antenna port. Without loss of generality, the channel coefficient from the terminal device 110-n to the network device 120 in the common time-frequency resource is denoted by

In this way, the network device 120 may receive a synchronous and superimposed signal from the set of active terminal devices. The network device 120 may identify the unknown active subset S _A based on the superimposed conjugated symmetric sequence, which will be discussed in detail below. Thus, a synchronous UAD is supported with a high accuracy and a low cost.

In a case where the UAD is integrated with the scheduling request-grant procedure for massive access, the network device 120 may further inform the identified active terminal devices through a mapping list. Each row of the list, dedicated to a identified terminal device, contains the ID of the corresponding terminal device and the related scheduling grant. The network device 120 may assign these resources only for the identified terminal devices, however, any of terminal devices can check the list. Through checking, an active terminal device may determine whether it has been successfully identified by the network device 120.

It should be understood that the numbers of terminal devices, network device and their connections shown in FIG. 1 are only for the purpose of illustration without suggesting any limitation. The communication network 100 may include any suitable number of devices configured to implementing example embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be located in the communication network 100.

Communications in the communication environment 100 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) , the fifth generation (5G) , the sixth generation (6G) , and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA) , Frequency Division Multiple Access (FDMA) , Time Division Multiple Access (TDMA) , Frequency Division Duplex (FDD) , Time Division Duplex (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Division Multiple (OFDM) , Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future.

Work Principle and Example Signaling for Communication

Reference is now made to FIG. 2, which illustrates a signaling chart 200 for synchronous UAD according to some example embodiments of the present disclosure. The synchronous UAD process 200 may involve the set of terminal devices 110-1 to 110-N and the network device 120, in particular, some of the actions involve the active terminal devices 110-1, 110-n, and 110-N. For the purpose of discussion, reference is made to FIG. 1 to describe the signaling flow 200. In addition, for ease of description, the terminal device 110-n may be taken as a representative of the active terminal devices.

In process 200, the synchronous UAD is realized by using a conjugated symmetric sequence set. To this end, the set of terminal devices 110-1 to 110-N are preassigned with a conjugated symmetric sequence set and a common time-frequency resource for transmission of respective conjugated symmetric sequence.

The terminal device 110-1 receives 205 a configuration assigning a common time-frequency resource for a set of terminal devices 110-1 to 110-N in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences from the network device 120. Similarly, the terminal device 110-n and 110-N also receive 210, 215 analogous configurations from the network device 120. In some examples of embodiment, configurations indicated by 205, 210, and 215 may be combined and transmitted from the network device 120 in a broadcast way.

By way of example, the common time-frequency resource may comprise M REs in a coherence block, and each RE bears one symbol of the conjugated symmetric sequence encoded by the terminal device 110.

For example, the terminal device 110-n, where n=1, 2, …, N, may be preassigned with the conjugated symmetric sequence, denoted by a vector

with

where

and M denotes a length of the conjugated symmetric sequence, and is supposed to be odd number without loss of generality. f _n denotes the unique frequency parameter with the terminal device 110-n that satisfies 0≤f _n<1, and f _n≠f _k for n≠k.

where the superscript (·) ^* denotes conjugation. Each sequence comprises M complex symbols that are mapping to M REs for transmission, respectively.

The conjugated symmetric sequence s _n may be a complex conjugated symmetric sinusoid sequence with a variable frequency parameter f _n . The conjugated symmetric sequence may be associated exclusively with the terminal device 110-n by associating a unique frequency parameter with the terminal device 110-n. As such, different terminal devices can be discriminated by the frequency parameters without preamble collision.

As an example of implementations, f _n= (n-1) /N , or f _n=sinθ _n for 0≤θ _n<π/2 . Moreover, s _n has a constant modulus such that

for m=0, 1, …, M-1 and ‖s _n‖ ²=1.

In some example embodiments, the length M of the conjugated symmetric sequence may be greater than or equal to twice a number of the set of active terminal devices, which may be an average number of active terminal devices, i.e., 2×E {|S _A|} , no matter how the total number of terminal devices, i.e., N. E {·} represents mathematical expectation and |·| stands for cardinality of a set.

Since the terminal device 110-n (as well as the terminal device 110-1 and 110-N) becomes the active terminal device, i.e.,

it will transmit the encoded conjugated symmetric sequence, denoted by

with a partial phase compensation.

In some example embodiments, the active terminal device 110-n may encode the conjugated symmetric sequence s _n with a partial phase-compensation factor

which may be determined as follows,

where

represents the angle of a complex number,

denotes a partial estimate of h _n, and the power of the transmitted sequence is configurated at level of P _n. In some example embodiments, the encoded conjugated symmetric sequence may be determined as

or

In other words, the encoded conjugated symmetric sequence is generated by encoding the conjugated symmetric sequence associated with the terminal device 110-n with a partial phase-compensation factor for compensating a phase of a channel (i.e., the UL channel) from the terminal device 110-n to the network device 120 in the common time-frequency resource, denoted by

Thus, the encoded transmission of a conjugated symmetric sequence indicates activity information of an active terminal device out of the entire set of terminal devices.

To save spectrum resources, all N terminal devices (i.e., terminal devices 110-1 to 110-N) are permitted to share a common time-frequency resource including M REs for transmitting their assigned sequences. As a result, each of the terminal devices 110-1, 110-n and 110-N transmits 220 to the network device 120 an encoded conjugated symmetric sequence in the common time-frequency resource.

FIG. 3 illustrates a schematic diagram of resource mapping 300 for conjugated symmetric sequence with partial phase compensation according to some example embodiments of the present disclosure. As shown in FIG. 3, the shared PRB comprises M REs and each RE bears one symbol of

denoted by

In this way, the network device 120 may receive a synchronous and superimposed signal from the set of active terminal devices S _A, and its base-band version can be written as an M-length vector:

where

represents an additive noise including the inter-cell interference, r represents the superimposed conjugated symmetric sequence received by the network device 120.

Considering that each terminal device 110-n may not possess full information of the phase of UL channel

but its partial estimate

the partial phase-compensation factor

is derived based on a partial knowledge on the phase of UL channel. In particular, the partial estimate

can be treated as a coarse estimate of

and the admissible estimation error can be up to

such that the absolute bias of the partial estimate satisfies

In some example embodiments, the partial estimate

can be derived for an estimate of the phase of the corresponding DL channel. In other words, the partial phase-compensation factor is determined based on an estimate of a phase of a channel from the network device 120 to the terminal device 110-n in the common time-frequency resource and a channel reciprocity between a transmission pair of the terminal device 110-n and the network device 120.

At the terminal device side, the UL channel phase is partially compensated by the partial knowledge

where the residual phase can be tolerated within a wide interval

In other words, the partial phase-compensation factor

may be determined based on a partial estimate of the phase of the channel from the terminal device 110 to the network device 120 in the common time-frequency resource, wherein an absolute bias of the partial estimate is less than half of π in radian. As can be seen, the tolerable error range is so loose and occupied half complex plane.

Since active terminal devices 110-1, 110-n and 110-N can adjust transmit-time advance according to the prior knowledge on timing alignment, they are synchronized within the cyclic prefix. In this case, the active terminal devices 110-1, 110-n and 110-N transmit their respective encoded conjugated symmetric sequences in a synchronous way based on timing alignment information from the network device 120. As a result, the block-fading assumption yields a legitimate model for the channel.

To this end, the network device 120 may transmit a beacon signal, for example, at the beginning of each transmission cycle to indicate transmission of the encoded conjugated symmetric sequence. This invites uplink transmissions from the active terminal devices. The sequences transmitted from all active terminal devices 110-1, 110-n and 110-N arrive at the network device 120 in a synchronous manner with respect to the receiving window of the network device 120.

Consequently, the network device 120 can observe a superimposed version of the encoded conjugated symmetric sequences transmitted from all active terminal devices 110-n for n∈S _A. In the example embodiments, no coordination among terminal devices is needed in the transmission procedure. Each active terminal device behaves independently according to its own scheduling request, and the inactive terminal devices not belong to S _A , e.g., terminal devices 110-2 and 110-3, refrain from any operations except for keeping silence. Note that the network device 120 has the a priori knowledge on association pattern between the set of conjugated symmetric sequences and the set of terminal devices 110-1 to 110-N, so that the network device 120 can identify the active terminal devices by detecting which conjugated symmetric sequence presents in the superimposed observation.

Accordingly, the superimposed conjugated symmetric sequence received at the network device 120 for UAD can be written as a length-M vector r as follows.

For the case of

the vector r may be rewritten in the form of activity indicating symbols associated with the set of terminal devices 110-1 to 110-N:

where

denotes the received activity indicating symbol associated with terminal devices 110-n and may be specified by

Both α _n and P _n share the same indices of nonzero entries induced by the active terminal devices 110-n for n∈S _A . Thus, vector {α _n} _n∈S is a sparse vector. Only a few number of components are nonzero that are corresponding to the active terminal devices 110-n for n∈S _A.

For the case of

with the partial phase compensation satisfying

the real parts of {α _n} _n∈S are always nonnegative, i.e., Re {α _n} ≥0 for any n∈S, where Re {·} represents the real part of a complex number. That is, {Re {α _n} } _n∈S is a sparse nonnegative vector in which positive components indicate user activity whereas the zeros indicate user inactivity. For the case of

the activity indicating symbols may be written as

where the real parts of the activity indicating symbols {α _n} _n∈S are nonpositive. In other words, the nonzero real parts of the activity indicating symbols {α _n} _n∈S have the same sign.

At the network device 120 side, after receiving the superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource, i.e., r, it identifies 225 the set of active terminal devices, i.e., S _A, out of the set of terminal devices by solving the activity indicating symbols, i.e., {α _n} _n∈S , from the superimposed conjugated symmetric sequence. This will be discussed in detail below.

In particular, the network device 120 may identify the active terminal devices by restoring N unknowns {α _n} _n∈S from the M mixed observations of the received vector r, where N>M . Indeed, this involves an inverse problem with respect to the observation model

which can be rewritten as a scalar form:

In essence, this is an underdetermined linear system with more unknown variables than equations, since S _A is an unknown set to be identified. Although {α _n} _n∈S is sparse with many zero components, the nonzero components are complex numbers in general resulting from total effect of channel experience and the partial phase compensation.

To figure out the high-dimensional complex vector {α _n} _n∈S from the low-dimensional original received data, in some example embodiments, the network device 120 may estimate the real parts and imaginary parts of {α _n} _n∈S separately and serially.

In particular, the real parts {Re {α _n} } _n∈S may be first derived for all the terminal devices 110-1 to 110-N by solving a large-scale subproblem involving N -dimensional optimization variables. Based on the estimate of the real parts {Re {α _n} } _n∈S , a coarse estimate of S _A can be identified out of the ensemble set S. The coarse estimate

pursues low miss-detection rate with tolerance of large false-alarm rate. For the purpose, a relatively small decision threshold, i.e., β _low , may be predefined as the first threshold, so that the coarse estimate

as the first set of identified active terminal devices, can include almost all active terminal devices while inevitably containing a certain number of inactive terminal devices. In particular,

is more than |S _A| but much less than N and the knowledge of the coarse estimate

can be utilized for model reduction. The system as derived by formular (8) with respect to N -dimensional unknowns can be reduced by removing the unknowns α _n’s for

Therefore, a reduced linear observation model with respect to

-dimensional unknowns can be derived as

The system as derived by formular (9) is a determined system because

is usually smaller than M . Such a model reduction overcomes the problem of dimensional deficiency, caused by inadequate measurement resource, and enables a complete estimate for

In this way, the network device 120 can easily reach the whole knowledge of α _n for

by solving a small-scale subproblem involving

-dimensional optimization variables. Finally, the whole knowledge of α _n is used to further refine

and obtain the second set of identified active terminal devices.

It is the conjugated symmetry in sequence design that ease the network device 120 to cancel out the imaginary parts of {α _n} _n∈S from the original received data r [m] , resulting in desirable observations of a superimposed complex sinusoid sequence only depending on the real parts as

where

In some example embodiments, a superimposed complex sinusoid sequence only depending on the imaginary parts of {α _n} _n∈S may be also derived from the original data r [m] through

In addition, the deliberate partial phase compensation for the conjugated symmetric sequence ensures that the real parts of the unknown vector {α _n} _n∈S are restricted to be nonnegative for the case of

Such a nonnegative constraint on unknowns facilitates solving

from the transformed observations y [m] , despite that the system derived by formular (10) remains underdetermined. Indeed, the system of y [m] turns out to be a nonnegative underdetermined system. Fortunately, the designed complex sinusoid sequence is vital to capture entire information about the unknown vector

with the minimum measurement resource. If 2|S _A|≤M,

can be uniquely solved from the system derived by formular (10) for noiseless case.

Such a careful and systematic design enable a fast and accurate detection method for the network device 120 to recover

from the noisy observation r [m] . In estimating the real parts

for all potential terminal devices 110-1 to 110-N, a nonnegative least square (LS) method is developed to solve it. In addition, the L-MMSE (Linear Minimum Mean Square Error) method with nonnegative constraints is designed for estimating

-dimensional unknows of

based on the reduced observation model. Finally, the whole knowledge of

and

are used to refine

via a stringent threshold (e.g., β _high) , as the second threshold, for reducing a false-alarm rate.

The detailed procedure of the proposed algorithm for the case of

is described in Table 1 as follows. In Step 5, for higher accuracy the real parts of the activity indicating symbol associated the first set of identified active terminal devices, i.e.,

are replaced with the corresponding real parts derived from the sparse nonnegative vector

For the case of

similar algorithm may be derived by replacing the nonnegative constraints with nonpositive constraints in

Steps

2 and 4, i.e., x _n≤0 and Re {z _n} ≤0.

Table 1. Example procedure of UAD algorithm

After identifying the active terminal devices, the network device 120 may then transmit 230 an indication indicative of the set of identified active terminal devices, i.e., the refined

through a common channel to the set of terminal devices 110-1 to 110-N. For example, the network device 120 may inform the identified active terminal devices of a mapping list. Each row of the list contains the ID of an identified terminal device and the related scheduling grant. The network device 120 may assign resources only for the identified terminal devices, although any of the entire set of terminal devices 110-1 to 110-N can check the list. Through checking, an active terminal device can determine whether it has been successfully identified by the network device 120.

Additionally. the indication may further indicate resources for performing the communication by the set of active terminal devices identified by the network device 120 respectively. Accordingly, the active terminal device being correctly identified 110-n for

may perform the communication with the network device 120 by using a respective resource related to the terminal device110-n for

Accordingly, in process 200, the set of terminal devices 110-1, 110-n and 110-N may determine 235, 240, 245 whether the terminal device is included in the set of active terminal devices identified by the network device 120, i.e., the refined

If the detection is successful, the active terminal device may proceed to provide the detailed scheduling information to the network device 120. By way of example, the indication from the network device 120 indicates that the terminal devices 110-1 and 110-n are included in the set of active terminal devices identified by the network device 120.

In this case, based on a determination that the terminal device 110-1 is included in the set of active terminal devices identified by the network device 120, the terminal device 110-1 may perform 250 communication with the network device 120. Similarly, the terminal device 110-n may perform 255 communication with the network device 120 based on an analogous determination.

Otherwise, if the detection is not successful, the active terminal device may raise the scheduling request by retransmitting their conjugated symmetric sequence with partial phase compensation in the next synchronous UAD occasions.

In the above example, since the terminal device 110-N is not included in the set of active terminal devices identified by the network device 120, the terminal device 110-N is miss-detected by the network device 120. In this case, the terminal device 110-N may retransmit 260 the encoded conjugated symmetric sequence to the network device 120.

As one of the various application scenarios, the conjugated symmetric sequence with partial phase compensation provided in the example embodiments can be readily integrated with the scheduling request-grant procedure. By way of example, in such an integrated procedure, all UEs may establish connection-like state without the dedicated scheduling request resource. The active UEs may then raise scheduling requests by transmitting their conjugated symmetric sequences with partial phase compensation, respectively and simultaneously in the common time-frequency resource. Upon receiving the superimposed conjugated symmetric sequences in the common time-frequency resource, the BS performs synchronous UAD. The BS may then give scheduling grants for the identified UEs via a common DL control channel. The common DL control channel may be a low-rate DL control channel which can be accessed by all UEs. Each active UE checks the DL control channel and determines whether it have been identified as an active UE. Accordingly, the identified UEs provide detailed traffic-demand information, such as, buffer state report, to the BS, while the miss-detected UEs are relegated to raise scheduling request in the next synchronous UAD occasion, for example, by retransmitting their encoded conjugated symmetric sequence with partial phase compensation.

It should be understood that some of the steps in process 200 are optional or can be omitted, and the order of the steps is given for an illustrative purpose. For example, the step 205 to 215 may be performed in parallel. Thus, the embodiments of the present disclosure are not limited in this regard.

According to the example embodiments of the present disclosure, a conjugated symmetric sequence {s _n} _n∈S is provided for accurate, fast and scalable UAD such that the required sequence length M can be as small as twice the average number of active terminal devices, i.e., 2×E {|S _A|} , no matter how the total number of devices, N, scales up. Taking advantage of the holistic design from the partial phase compensation, the communication system can benefit from following advantages:

● Minimize measurement cost required for perfect detection: Despite the sequence length is less than the total number of potential users M<N, the perfect synchronous UAD can be made as long as the number of actual active terminal devices is less than M/2. Such perfect detection is deterministic in the noiseless case.

● Scalability for massive access: The required measurement resource for perfect detection is just depending on the number of actual active users and independent of the total number of terminal devices, resulting in a scalable scheme.

● Facilitate the sparsity detection: Nonnegativity introduces the sparsity in a natural way. Thus, the regularization term (usually adopted by the compressive sensing) for encouraging sparsity can be avoided in the detection algorithm design, leading to a fast detection algorithm with finite-step computation.

● Fixed assignment between preamble and users establishes a unique association, which not only avoids the preamble collision due to random assignment, but also saves the additional procedure for reporting the user ID.

Example Simulation Results

Performance comparison between synchronous UAD via conjugated symmetric sequence and PRACH via ZC sequence under the same time-frequency resource (e.g., one PRB consisting of 241 REs) will now be discussed. Tables 2 and 3 list the detailed simulation parameters and channel model, respectively. For synchronous UAD, zero correlation zone of ZC sequence can be zero. This suggests that 241-length ZC sequence can provide 241 orthogonal sequences for synchronous users without ambiguity, which is more than those provided in PRACH for random access without timing alignment. The UAD performance is evaluated in terms of the probabilities of miss detection and false alarm. The simulation results are derived by averaging over 10000 independent experiments.

Table 2. Simulation setup

Table 3. Channel model

FIG. 4 shows various UAD performances under different transmission probabilities. In particular, for the synchronous UAD (S-UAD) via conjugated sequence with partial phase compensation, it can observe a threshold of transmission probability of 12.5%, beyond which the detection performance degrades severely, and the performance is limited by the degree-of-freedom. In fact, the threshold coincides with M/2N in the simulation case. The observation agrees with the theoretical analysis about perfect reconstruction condition.

Simulation results in FIG. 4 show that the conjugated symmetric sequence with partial phase compensation provided by the example embodiments can increase the supporting number of concurrent random-access users by above 2.5 times, compared to the existing PRACH scheme. Such a superiority is benefitted from the holistic design from the collision-free and complex conjugated symmetric sinusoid sequence, partial phase compensation to the advanced algorithm for UAD. For PARCH, in contrast, sequence collision from random selection remains the major cause to performance degradation.

Example Methods

FIG. 5 illustrates a flowchart of a method 500 implemented at a terminal device according to some example embodiments of the present disclosure. For example, the terminal device may include a UE, and so on. For the purpose of discussion, the method 500 will be described from the perspective of the terminal devices 110-1 in FIG. 1.

At block 510, the terminal device 110-1 receives, from a network device 120 in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices 110-1 to 110-N in the radio access network and a configuration associating the set of terminal devices 110-1 to 110-N with a set of conjugated symmetric sequences. Encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices 110-1 to 110-N.

In some example embodiments, the conjugated symmetric sequence may be a complex conjugated symmetric sinusoid sequence with a variable frequency parameter.

In some example embodiments, a length of the conjugated symmetric sequence may be greater than or equal to twice a number of the set of active terminal devices.

In some example embodiments, the conjugated symmetric sequence may be associated exclusively with the terminal device 110-1 by associating a unique frequency parameter with the terminal device 110-1.

At block 520, the terminal device 110-1 transmits, to the network device 120, an encoded conjugated symmetric sequence in the common time-frequency resource.

In some example embodiments, transmitting the encoded conjugated symmetric sequence may comprise: generating the encoded conjugated symmetric sequence by encoding a conjugated symmetric sequence associated with the terminal device 110-1 with a partial phase-compensation factor for compensating a phase of a channel from the terminal device 110-1 to the network device 120 in the common time-frequency resource.

In some example embodiments, the partial phase-compensation factor may be determined based on a partial estimate of the phase of the channel from the terminal device 110-1 to the network device 120 in the common time-frequency resource. An absolute bias of the partial estimate is less than half of Pi in radian.

In some example embodiments, the method 300 may further comprise: determining the partial phase-compensation factor based on an estimate of a phase of a channel from the network device 120 to the terminal device 110-1 in the common time-frequency resource and a channel reciprocity between a transmission pair of the terminal device 110-1 and the network device 120.

In some example embodiments, the method 300 may further comprise: receiving, from the network device 120, an indication indicative of a set of active terminal devices identified by the network device; determining whether the terminal device 110-1 is included in the set of active terminal devices identified by the network device 120; performing communication with the network device 120 based on a determination that the terminal device 110-1 is included in the set of active terminal devices identified by the network device; or retransmitting an encoded conjugated symmetric sequence to the network device 120 based on a determination that the terminal device 110-1 is excluded from the set of active terminal devices identified by the network device 120.

In some example embodiments, the indication may be further indicative of resources for performing the communication by the set of active terminal devices identified by the network device 120 respectively, and the terminal device 110-1 may perform the communication with the network device 120 by using a respective resource related to the terminal device 110-1.

In some example embodiments, transmitting the encoded conjugated symmetric sequence may comprise: transmitting the encoded conjugated symmetric sequence in a synchronous way based on timing alignment information from the network device 120.

FIG. 6 illustrates a flowchart of an example method 600 implemented at a network device in accordance with some example embodiments of the present disclosure. For example, the network element may include a gNB, and so on. For the purpose of discussion, the method 600 will be described from the perspective of the network device 120 in FIG. 1.

At 610, the network device 120 transmits to a set of terminal devices 110-1 to 110-N in the radio access network, a configuration assigning a common time-frequency resource for the set of terminal devices 110-1 to 110-N and a configuration associating the set of terminal devices 110-1 to 110-N with a set of conjugated symmetric sequences. Encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices 110-1 to 110-N.

In some example embodiments, the conjugated symmetric sequence may be a complex conjugated symmetric sinusoid sequence with a variable frequency parameter and a length of the conjugated symmetric sequence is greater than or equal to twice a number of the set of active terminal devices.

At 620, the network device 120 receives a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource. The superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of terminal devices 110-1 to 110-N.

In some example embodiments, the encoded conjugated symmetric sequences may be generated, respectively, by encoding conjugated symmetric sequences associated with the set of active terminal devices with partial phase-compensation factors for compensating phases of channels from the set of active terminal devices to the network device 120 in the common time-frequency resource.

In some example embodiments, nonzero real parts of the activity indicating symbols have the sign.

At 630, the network device 120 identifies the set of active terminal devices out of the set of terminal devices 110-1 to 110-N by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.

In some example embodiments, identifying the set of active terminal devices may comprise: determining, based on the superimposed conjugated symmetric sequence and its conjugated symmetricity, a superimposed complex sinusoid sequence comprising real parts of the activity indicating symbols associated with the set of terminal devices 110-1 to 110-N, while excluding imaginary parts of the activity indicating symbols associated with the set of terminal devices 110-1 to 110-N; determining a first set of identified active terminal devices based on the superimposed complex sinusoid sequence; and determining, based on the superimposed conjugated symmetric sequence and the first set of identified active terminal devices, a second set of identified active terminal devices as the set of identified active terminal devices.

In some example embodiments, determining the first set of identified active terminal devices may comprise: determining, based on the superimposed complex sinusoid sequence, a sparse nonnegative vector representing real parts of the activity indicating symbols associated with the set of terminal devices 110-1 to 110-N; determining effective nonzero components of the real parts of the activity indicating symbols associated with the set of terminal devices 110-1 to 110-N by comparing components of the sparse nonnegative vector with a first predefined threshold; and determining the first set of identified active terminal devices based on the effective nonzero components of the real parts of the activity indicating symbols associated with the set of terminal devices 110-1 to 110-N.

In some example embodiments, determining the sparse nonnegative vector may comprise: solving a nonnegative least square problem based on the superimposed complex sinusoid sequence and the set of conjugated symmetric sequences.

In some example embodiments, determining the second set of identified active terminal devices may comprise: determining, based on the superimposed conjugated symmetric sequence, a low-dimensional complex vector representing the activity indicating symbols associated with the first set of identified active terminal devices; determining effective nonzero components of the activity indicating symbols associated with the first set of identified active terminal devices by comparing amplitudes of components of the low-dimensional complex vector with a second predefined threshold; and determining the second set of identified active terminal devices based on the effective nonzero components of the activity indicating symbols associated with the first set of identified active terminal devices.

In some example embodiments, the low-dimensional complex vector may be determined under a constraint that nonzero real parts of the low-dimensional complex vector have the same sign.

In some example embodiments, the method 600 may further comprise: replacing real parts of the activity indicating symbol associated the first set of identified active terminal devices with corresponding real parts derived from the sparse nonnegative vector.

In some example embodiments, the method 600 may further comprise: transmitting, to the set of terminal devices 110-1 to 110-N, an indication indicative of the set of identified active terminal devices through a common channel.

In some example embodiments, the indication may be indicative of resources for performing a communication by each of the set of identified active terminal devices respectively.

the method 600 may further comprise: transmitting a beacon signal to the set of terminal devices 110-1 to 110-N indicating transmission of the encoded conjugated symmetric sequence.

Example Apparatus, Device and Medium

In some example embodiments, a first apparatus capable of performing any of the method 500 (for example, the terminal device 110-1 in FIG. 1) may comprise means for performing the respective operations of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the terminal device 110-1 in FIG. 1.

In some example embodiments, the first apparatus comprises: means for receiving, at the first apparatus in a radio access network and from a second apparatus in the radio access network, a configuration assigning a common time-frequency resource for a set of first apparatuses in the radio access network and a configuration associating the set of first apparatuses with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of first active apparatuses out of the set of first apparatuses; and means for transmitting, to the second apparatuses, an encoded conjugated symmetric sequence in the common time-frequency resource.

In some example embodiments, the conjugated symmetric sequence is a complex conjugated symmetric sinusoid sequence with a variable frequency parameter.

In some example embodiments, a length of the conjugated symmetric sequence is greater than or equal to twice a number of the set of first active apparatus.

In some example embodiments, the conjugated symmetric sequence is associated exclusively with the first apparatus by associating a unique frequency parameter with the first apparatus.

In some example embodiments, the means for transmitting the encoded conjugated symmetric sequence comprises: means for generating the encoded conjugated symmetric sequence by encoding a conjugated symmetric sequence associated with the first apparatus with a partial phase-compensation factor for compensating a phase of a channel from the first apparatus to the second apparatus in the common time-frequency resource.

In some example embodiments, the partial phase-compensation factor is determined based on a partial estimate of the phase of the channel from the first apparatus to the second apparatus in the common time-frequency resource, wherein an absolute bias of the partial estimate is less than half of Pi in radian.

In some example embodiments, the first apparatus further comprises: means for determining the partial phase-compensation factor based on an estimate of a phase of a channel from the second apparatus to the first apparatus in the common time-frequency resource and a channel reciprocity between a transmission pair of the first apparatus and the second apparatus.

In some example embodiments, the first apparatus further comprises: means for receiving, from the second apparatus, an indication indicative of a set of first active apparatuses identified by the second apparatus; means for determining whether the first apparatus is included in the set of first active apparatuses identified by the second apparatus; means for performing communication with the second apparatus based on a determination that the first apparatus is included in the set of first active apparatuses identified by the second apparatus; or means for retransmitting an encoded conjugated symmetric sequence to the second apparatus based on a determination that the first apparatus is excluded from the set of first active apparatuses identified by the second apparatus.

In some example embodiments, the indication is further indicative of resources for performing the communication by the set of first active apparatuses identified by the second apparatus respectively, and the first apparatus performs the communication with the second apparatus by using a respective resource related to the first apparatus.

In some example embodiments, the means for transmitting the encoded conjugated symmetric sequence comprises: transmitting the encoded conjugated symmetric sequence in a synchronous way based on timing alignment information from the second apparatus.

In some example embodiments, a second apparatus capable of performing any of the method 600 (for example, the network device 120 in FIG. 1) may comprise means for performing the respective operations of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the network device 120 in FIG. 1.

In some example embodiments, the second apparatus comprises: means for transmitting, at the second apparatus in a radio access network and to a set of first apparatuses in the radio access network, a configuration assigning a common time-frequency resource for the set of first apparatuses and a configuration associating the set of first apparatuses with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of first active apparatuses out of the set of first apparatuses; means for receiving a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of first active apparatuses in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of first apparatuses; and means for identifying the set of first active apparatuses out of the set of first apparatuses by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.

In some example embodiments, the conjugated symmetric sequence is a complex conjugated symmetric sinusoid sequence with a variable frequency parameter and a length of the conjugated symmetric sequence is greater than or equal to twice a number of the set of first active apparatuses.

In some example embodiments, the encoded conjugated symmetric sequences are generated, respectively, by encoding conjugated symmetric sequences associated with the set of first active apparatuses with partial phase-compensation factors for compensating phases of channels from the set of first active apparatuses to the second apparatus in the common time-frequency resource.

In some example embodiments nonzero real parts of the activity indicating symbols have the same sign.

In some example embodiments, the means for identify the set of first active apparatuses comprises: means for determining, based on the superimposed conjugated symmetric sequence and its conjugated symmetricity, a superimposed complex sinusoid sequence comprising real parts of the activity indicating symbols associated with the set of first apparatuses, while excluding imaginary parts of the activity indicating symbols associated with the set of first apparatuses; means for determining a first set of identified first active apparatuses based on the superimposed complex sinusoid sequence; and means for determining, based on the superimposed conjugated symmetric sequence and the first set of identified first active apparatuses, a second set of identified first active apparatuses as the set of identified first active apparatuses.

In some example embodiments, the means for determining the first set of identified first active apparatuses comprises: means for determining, based on the superimposed complex sinusoid sequence, a sparse nonnegative vector representing real parts of the activity indicating symbols associated with the set of first apparatuses; means for determining effective nonzero components of the real parts of the activity indicating symbols associated with the set of first apparatuses by comparing components of the sparse nonnegative vector with a first predefined threshold; and means for determining the first set of identified first active apparatuses based on the effective nonzero components of the real parts of the activity indicating symbols associated with the set of first apparatuses.

In some example embodiments, the low-dimensional complex vector is determined under a constraint that nonzero real parts of the low-dimensional complex vector have the same sign.

In some example embodiments, the means for determining the second set of identified first active apparatuses comprises: means for determining, based on the superimposed conjugated symmetric sequence, a low-dimensional complex vector representing the activity indicating symbols associated with the first set of identified first active apparatuses; means for determining effective nonzero components of the activity indicating symbols associated with the first set of identified first active apparatuses by comparing amplitudes of components of the low-dimensional complex vector with a second predefined threshold; and means for determining the second set of identified first active apparatuses based on the effective nonzero components of the activity indicating symbols associated with the first set of identified first active apparatuses.

In some example embodiments, the second apparatus further comprises: means for replacing real parts of the activity indicating symbol associated the first set of identified first active apparatuses with corresponding real parts derived from the sparse nonnegative vector.

In some example embodiments, the second apparatus further comprises: means for transmitting, to the set of first apparatuses, an indication indicative of the set of identified first active apparatuses through a common channel.

In some example embodiments, the indication is indicative of resources for performing a communication by each of the set of identified first active apparatuses respectively.

In some example embodiments, the second apparatus further comprises: means for transmitting a beacon signal to the set of first apparatuses indicating transmission of the encoded conjugated symmetric sequence.

FIG. 7 is a simplified block diagram of a device 700 that is suitable for implementing example embodiments of the present disclosure. The device 700 may be provided to implement an electronic device, for example, the terminal device 110, or the network device 120 as shown in FIG. 1. As shown, the device 700 includes one or more processors 710, one or more memories 720 coupled to the processor 710, and one or more communication modules 740 coupled to the processor 710.

The communication module 740 is for bidirectional communications. The communication module 740 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 740 may include at least one antenna.

The processor 710 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 700 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.

The memory 720 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 724, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , an optical disk, a laser disk, and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 722 and other volatile memories that will not last in the power-down duration.

A computer program 730 includes computer executable instructions that are executed by the associated processor 710. The instructions of the program 730 may include instructions for performing operations/acts of some example embodiments of the present disclosure. The program 730 may be stored in the memory, e.g., the ROM 724. The processor 710 may perform any suitable actions and processing by loading the program 730 into the RAM 722.

The example embodiments of the present disclosure may be implemented by means of the program 730 so that the device 700 may perform any process of the disclosure as discussed with reference to FIG. 3 to FIG. 6. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some example embodiments, the program 730 may be tangibly contained in a computer readable medium which may be included in the device 700 (such as in the memory 720) or other storage devices that are accessible by the device 700. The device 700 may load the program 730 from the computer readable medium to the RAM 722 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

FIG. 8 shows an example of the computer readable medium 700 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 700 has the program 730 stored thereon.

Generally, 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 representations, it is to be understood that the block, apparatus, system, technique or method 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.

Some example embodiments of the present disclosure also provides at least one computer program product tangibly stored on a computer readable medium, such as a non- transitory computer readable medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, 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. The program code 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 code, 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.

In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer 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. More specific examples of the computer 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.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A terminal device in a radio access network, comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the terminal device at least to:

receive, from a network device in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; and

transmit, to the network device, an encoded conjugated symmetric sequence in the common time-frequency resource.
The terminal device of claims 1, wherein the conjugated symmetric sequence is a complex conjugated symmetric sinusoid sequence with a variable frequency parameter.
The terminal device of claim 1 or 2, wherein a length of the conjugated symmetric sequence is greater than or equal to twice a number of the set of active terminal devices.
The terminal device of claim 1 or claim 2, wherein the conjugated symmetric sequence is associated exclusively with the terminal device by associating a unique frequency parameter with the terminal device.
The terminal device of claim 1, wherein the terminal device is caused to transmit the encoded conjugated symmetric sequence by:

generating the encoded conjugated symmetric sequence by encoding a conjugated symmetric sequence associated with the terminal device with a partial phase-compensation factor for compensating a phase of a channel from the terminal device to the network device in the common time-frequency resource.
The terminal device of claim 5, wherein the partial phase-compensation factor is determined based on a partial estimate of the phase of the channel from the terminal device to the network device in the common time-frequency resource, wherein an absolute bias of the partial estimate is less than half of Pi in radian.
The terminal device of claim 5 or claim 6, wherein the terminal device is further caused to:

determine the partial phase-compensation factor based on an estimate of a phase of a channel from the network device to the terminal device in the common time-frequency resource and a channel reciprocity between a transmission pair of the terminal device and the network device.
The terminal device of claim 1, wherein the terminal device is further caused to:

receive, from the network device, an indication indicative of a set of active terminal devices identified by the network device;

determine whether the terminal device is included in the set of active terminal devices identified by the network device;

perform communication with the network device based on a determination that the terminal device is included in the set of active terminal devices identified by the network device; or

retransmit an encoded conjugated symmetric sequence to the network device based on a determination that the terminal device is excluded from the set of active terminal devices identified by the network device.
The terminal device of claim 8, wherein the indication is further indicative of resources for performing the communication by the set of active terminal devices identified by the network device respectively, and the terminal device performs the communication with the network device by using a respective resource related to the terminal device.
The terminal device of claim 1, wherein the terminal device is caused to transmit the encoded conjugated symmetric sequence by:

transmitting the encoded conjugated symmetric sequence in a synchronous way based on timing alignment information from the network device.
A network device in a radio access network comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the network device at least to:

transmit, to a set of terminal devices in the radio access network, a configuration assigning a common time-frequency resource for the set of terminal devices and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices;

receive a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of terminal devices; and

identify the set of active terminal devices out of the set of terminal devices by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.
The network device of claim 11, wherein the conjugated symmetric sequence is a complex conjugated symmetric sinusoid sequence with a variable frequency parameter and a length of the conjugated symmetric sequence is greater than or equal to twice a number of the set of active terminal devices.
The network device of claim 11, wherein the encoded conjugated symmetric sequences are generated, respectively, by encoding conjugated symmetric sequences associated with the set of active terminal devices with partial phase-compensation factors for compensating phases of channels from the set of active terminal devices to the network device in the common time-frequency resource.
The network device of claim 11, wherein nonzero real parts of the activity indicating symbols have the same sign.
The network device of claim 11, wherein the network device is caused to identify the set of active terminal devices by:

determining, based on the superimposed conjugated symmetric sequence and its conjugated symmetricity, a superimposed complex sinusoid sequence comprising real parts of the activity indicating symbols associated with the set of terminal devices, while excluding imaginary parts of the activity indicating symbols associated with the set of terminal devices;

determining a first set of identified active terminal devices based on the superimposed complex sinusoid sequence; and

determining, based on the superimposed conjugated symmetric sequence and the first set of identified active terminal devices, a second set of identified active terminal devices as the set of identified active terminal devices.
The network device of claim 15, wherein the network device is caused to determine the first set of identified active terminal devices by:

determining, based on the superimposed complex sinusoid sequence, a sparse nonnegative vector representing the real parts of the activity indicating symbols associated with the set of terminal devices;

determining effective nonzero components of the real parts of the activity indicating symbols associated with the set of terminal devices by comparing components of the sparse nonnegative vector with a first predefined threshold; and

determining the first set of identified active terminal devices based on the effective nonzero components of the real parts of the activity indicating symbols associated with the set of terminal devices.
The network device of claim 16, wherein the network device is caused to determine the sparse nonnegative vector by:

solving a nonnegative least square problem based on the superimposed complex sinusoid sequence and the set of conjugated symmetric sequences.
The network device of claim 15, wherein the network device is caused to determine the second set of identified active terminal devices by:

determining, based on the superimposed conjugated symmetric sequence, a low-dimensional complex vector representing the activity indicating symbols associated with the first set of identified active terminal devices;

determining effective nonzero components of the activity indicating symbols associated with the first set of identified active terminal devices by comparing amplitudes of components of the low-dimensional complex vector with a second predefined threshold; and

determining the second set of identified active terminal devices based on the effective nonzero components of the activity indicating symbols associated with the first set of identified active terminal devices.
The network device of claim 18, wherein the low-dimensional complex vector is determined under a constraint that nonzero real parts of the low-dimensional complex vector have the same sign.
The network device of claim 18, wherein the network device is further caused to:

replace real parts of the activity indicating symbol associated the first set of identified active terminal devices with corresponding real parts derived from the sparse nonnegative vector.
The network device of any of claims 11-20, wherein the network device is further caused to:

transmit, to the set of terminal devices, an indication indicative of the set of identified active terminal devices through a common channel.
The network device of claim 21, wherein the indication is indicative of resources for performing a communication by each of the set of identified active terminal devices respectively.
The network device of any of claims 11-20, wherein the network device is further caused to:

transmit a beacon signal to the set of terminal devices indicating transmission of the encoded conjugated symmetric sequence.
A method comprising:

receiving, at a terminal device in a radio access network and from a network device in the radio access network, a configuration assigning a common time-frequency resource for a set of terminal devices in the radio access network and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices; and

transmitting, to the network device, an encoded conjugated symmetric sequence in the common time-frequency resource.
A method comprising:

transmitting, at a network device in a radio access network and to a set of terminal devices in the radio access network, a configuration assigning a common time-frequency resource for the set of terminal devices and a configuration associating the set of terminal devices with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of active terminal devices out of the set of terminal devices;

receiving a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of active terminal devices in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of terminal devices; and

identifying the set of active terminal devices out of the set of terminal devices by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.
A first apparatus comprising:

means for receiving, at the first apparatus in a radio access network and from a second apparatus in the radio access network, a configuration assigning a common time-frequency resource for a set of first apparatuses in the radio access network and a configuration associating the set of first apparatuses with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of first active apparatuses out of the set of first apparatuses; and

means for transmitting, to the second apparatuses, an encoded conjugated symmetric sequence in the common time-frequency resource.
A second apparatus comprising:

means for transmitting, at the second apparatus in a radio access network and to a set of first apparatuses in the radio access network, a configuration assigning a common time- frequency resource for the set of first apparatuses and a configuration associating the set of first apparatuses with a set of conjugated symmetric sequences, wherein encoded transmission of the conjugated symmetric sequences is indicative of activity information of a set of first active apparatuses out of the set of first apparatuses;

means for receiving a superimposed conjugated symmetric sequence associated with encoded conjugated symmetric sequences from the set of first active apparatuses in the common time-frequency resource, wherein the superimposed conjugated symmetric sequence comprises activity indicating symbols associated with the set of first apparatuses; and

means for identifying the set of first active apparatuses out of the set of first apparatuses by solving the activity indicating symbols from the superimposed conjugated symmetric sequence.
A computer readable medium comprising program instructions for causing an apparatus to perform the method of Claim 24 or 25.