WO2010076993A2

WO2010076993A2 - Method of trasmitting signlas from a user equipment by harq scheme in releasing sps radio resource and user equipment for the same

Info

Publication number: WO2010076993A2
Application number: PCT/KR2009/007537
Authority: WO
Inventors: Sung Jun Park; Seung June Yi; Sung Duck Chun
Original assignee: Lg Electronics Inc.
Priority date: 2009-01-02
Filing date: 2009-12-16
Publication date: 2010-07-08
Also published as: WO2010076993A3

Abstract

A method of transmitting signals from a user equipment by HARQ in releasing SPS radio resource and user equipment for the same are disclosed, by which signals can be efficiently transmitted. If a user equipment performs an SPS radio resource release command from a base station, HARQ feedback information received from the base station is forced to be set to ACK or an HARQ buffer of a corresponding HARQ process is flushed.

Description

METHOD OF TRASMITTING SIGNLAS FROM A USER EQUIPMENT BY HARQ SCHEME IN RELEASING SPS RADIO RESOURCE AND USER EQUIPMENT FOR THE SAME

The present invention relates to a mobile communication technology, and more particularly, to a method of transmitting signals from a user equipment by HARQ (hybrid automatic repeat request) in releasing SPS (semi-persistent scheduling) radio resource. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for enabling a user equipment to efficiently perform HARQ signaling in releasing SPS radio resource.

First of all, 3GPP LTE (3^rd generation partnership project) long term evolution: hereinafter called 'LTE') communication system is schematically described as a mobile communication system to which the present invention is applicable.

FIG. 1 is a schematic diagram of E-UMTS network structure as an example of a mobile communication system.

Referring to FIG. 1, E-UMTS (evolved universal mobile telecommunications system) is the system having evolved from UMTS (universal mobile telecommunications system) and its basic standardization is ongoing by 3GPP. Generally, the E-UMTS can be called LTE system.

E-UMTS network can be mainly divided into E-TRAN 101 and CN 102 (core network). The E-UTRAN (evolved-UMTS terrestrial radio access network) 101 consists of a user equipment (hereinafter abbreviated UE) 103, a base station (hereinafter named eNode B or eNB) 104, and an access gateway (hereinafter abbreviated AG) 105 located at an end point of the network to be externally connected to an external network. The AG 105 can be divided into one part responsible for user traffic processing and the other part for processing control traffic. In this case, the AG for new user traffic processing and the AG for processing control traffic can communicate with each other using a new interface.

At least one cell can exist at one eNode B. Between eNode Bs, an interface for user or control traffic transmission is usable. And, the CN 102 can consist of a node for user registrations of the AG 105 and other UE 103. Moreover, an interface for discriminating the E-UTRAN 101 and the CN 102 is available.

Layers of a radio interface protocol between a user equipment and a network can be divided into L1 (first layer), L2 (second layer) and L3 (third layer) based on three lower layers of the open system interconnection (OSI) reference model widely known in the field of communication systems. A physical layer belonging to the first layer provides an information transfer service using a physical channel. A radio resource control (hereinafter abbreviated RRC) located on the third layer plays a role in controlling radio resources between the user equipment and the network. For this, the RRC layers exchange RRC messages between the user equipment and the network. The RRC layers can be distributed to network nodes including the eNode B 104, the AG 105 and the like. Moreover, the RRC layer can be provided to the eNode B 104 or the AG 105 only.

FIG. 2 and FIG. 3 are diagrams for structures of a radio interface protocol between a user equipment and UTRAN based on the 3GPP radio access network specifications.

Referring to FIG. 2 and FIG. 3, a radio interface protocol horizontally consists of a physical layer, a data link layer and a network layer. And, the radio interface protocol vertically consists of a user plane for data information transfer and a control plane for control signal delivery (signaling). In particular, FIG. 2 shows the respective layers of the radio protocol control plane and FIG. 3 shows the respective layers of the radio protocol user plane. The radio protocol layers shown in FIG. 2 and FIG. 3 can be divided into L1 (first layer), L2 (second layer) and L3 (third layer) based on three lower layers of the open system interconnection (OSI) reference model widely known in the field of communication systems.

The respective layers of the radio protocol control plane shown in FIG. 2 and the respective layers of the radio protocol user plane shown in FIG. 3 are explained as follows.

First of all, a physical (PHY) layer of a first layer provides an upper layer with an information transfer service using a physical channel. The physical (PHY) layer is connected to a medium access control (MAC) layer on an upper layer via a transport channel. And, data is transported between the medium access control (MAC) layer and the physical (PHY) layer via the transport channel. In this case, the transport channel can be classified into a dedicated transport channel or a common transport channel according to whether a channel is shared or not. Moreover, data are transported via the physical channel between different physical layers, i.e., between a physical layer of a transmitting side and a physical layer of a receiving side.

Various layers exist in the second layer. First of all, a medium access control (hereinafter abbreviated MAC ) layer plays a role in mapping various logical channels to various transport channels. And, the MAC layer also plays a role as logical channel multiplexing in mapping several logical channels to one transport channel. The MAC layer is connected to a radio link control (RLC) layer of an upper layer via a logical channel. And, the logical channel can be mainly categorized into a control channel for transferring information of a control plane and a traffic channel for transferring information of a user plane according to a type of the transferred information.

A radio link control (hereinafter abbreviated RLC) of the second layer performs segmentation and concatenation on data received from an upper layer to play a role in adjusting a size of the data to be suitable for a lower layer to transfer the data to a radio section. And, the RLC layer provides three kinds of RLC modes including a transparent mode (hereinafter abbreviated TM), an unacknowledged mode (hereinafter abbreviated UM) and an acknowledged mode (hereinafter abbreviated AM) to secure various kinds of QoS demanded by each radio bearer (hereinafter abbreviated RB). In particular, the AM RLC performs a retransmission function through automatic repeat and request (ARQ) for the reliable data transfer.

A packet data convergence protocol (hereinafter abbreviated PDCP) layer of the second layer performs a header compression function for reducing a size of an IP packet header containing relatively large and unnecessary control information to efficiently transmit such an IP packet as IPv4 and IPv6 in a radio section having a small bandwidth. This enables a header part of data to carry mandatory information only to play a role in increasing transmission efficiency of the radio section. Moreover, in the LTE system, the PDCP layer performs a security function as well. This consists of ciphering for preventing data interception conducted by a third party and integrity protection for preventing data manipulation conducted by a third party.

A radio resource control (hereinafter abbreviated RRC) layer located at a most upper part of a third layer is defined in the control plane only and is responsible for controlling a logical channel, a transport channel and physical channels in association with configuration, reconfiguration and release of radio bearers (hereinafter abbreviated RBs). In this case, the RB means a logical path provided by the first and second layers of the radio protocol for the data delivery between the user equipment and the UTRAN. Generally, configuring an RB means to stipulate characteristics of radio protocol layers and channels required for providing a specific service and also means to configure detailed parameters and operational methods thereof. The RB can be classified into a signaling RB (SRB) or a data RB DRB). The SRB is used as a path for sending an RRC message in a control plane (C-plane) and the DRB is used as a path for transferring user data in a user plane (U-plane).

As a downlink transport channel for transporting data to a user equipment from a network, there is a broadcast channel (BCH) for transmitting system information and a downlink shared channel (SCH) for transmitting a user traffic or a control message. Downlink multicast, traffic of a broadcast service or a control message can be transmitted on downlink SCH or a separate downlink MCH (multicast channel). Meanwhile, as an uplink transport channel for transmitting data to a network from a user equipment, there is a random access channel (RACH) for transmitting an initial control message or an uplink shared channel (SCH) for transmitting user traffic or a control message.

As a downlink physical channel for transmitting information transferred on a downlink transport channel to a radio section between a network and a user equipment, there is a physical broadcast channel for transferring information of BCH, a physical multicast channel (PMCH) for transmitting information of MCH, a physical downlink shared channel for transmitting information of PCH and downlink SCH or a physical downlink control (or called DL L1/L2 control channel) for transmitting control information provided by first and second layers. As an uplink physical channel for transmitting information forwarded on an uplink transport channel to a radio section between a network and a user equipment, there is a physical uplink shared channel (PUSCH) for transmitting information of uplink SCH, a physical random access channel (PRACH) for transmitting RACH information or a physical uplink control channel (PUCCH) for transmitting such control information, which is provided by first and second layers, as HARQ ACK, HARQ NACK, scheduling request (SR), channel quality indicator (CQI) report and the like.

Based on the above description, resource allocation of speech data and scheduling method are explained as follows.

First of all, there are various kinds of modes in AMR (adaptive multi-rate) codec used for speech call. And, each of the modes is classified according to a size of speech information data. For example, in AMR NB (narrow band) 4.75 kbps mode, a 136-bit MAC SDU (medium access control service data unit) is delivered to a MAC entity each 20 ms. For another example, in AMR NB 12.65 kbps mode, a 288-bit MAC SDU is delivered to a MAC entity each 20 ms. Namely, if speech AMR codec is operable in one mode, AMR codec entity generates speech information having a predetermined size in a predetermined time interval. Hence, unless a mode of AMR codec is changed, a size of a speech information packet delivered to a radio protocol entity from an upper stage (e.g., an upper layer) is constant.

In due process, a base station or a user equipment is able to select an AMR codec mode to use in consideration of a quantity of radio resource available within a cell, a data transmission negotiated between the user equipment and the base station, a status of load within a cell and the like. Moreover, the selected AMR codec mode is reconfigurable according to a cell situation. Therefore, the base station or the user equipment has to cope with a change of the AMR codec mode.

Yet, speech information generated through AMR codec used for speech call, i.e., speech codec has special characteristics. First of al, speech data can have tow kinds of patterns, and more particularly, a period, for which a man actually talks, i.e., a talk spurt and a period, for which a man does not talk, i.e., a silent period. In the talk spurt, a speech packet including speech information is generated every 20ms. In the silent period, a silent packet (SID) including speech information is generated every 160ms.

In order for a base station to use a radio resource efficiently, if generated speech information corresponds to the talk spurt, the base station will set a radio resource to fit for a characteristic of the talk spurt. IN particular, the base station will set radio resource information allocated to a user equipment in 20ms interval using the characteristic that a speech packet is generated every 20ms.

In consideration of the above features of the speech data transmission, SPS (semi-persistent scheduling) is explained as follows.

FIG. 4 is a diagram for explaining a radio resource allocation scheme and FIG. 5 is a diagram for explaining SPS scheme.

A general process for a user equipment to transmit data to a base station (dynamic radio resource allocation scheme) is explained with reference to FIG. 4 as follows. First of all, a user equipment is able to make a request for a radio resource necessary for transmission of generated data to a base station [S401]. The base station is then bale to allocate a radio resource via a control signal in response to the radio resource request made by the user equipment [S402]. In LTE system, a resource allocation by a base station for uplink data transmission of a user equipment can be transmitted in form of an uplink grant (UL Grant) carried on a physical downlink control channel (PDCCH). Accordingly, the user equipment is able to transmit data to the base station via the allocated radio resource [S403]. The radio resource request made by the user equipment, the resource allocation conducted by the base station and the corresponding uplink data transmission performed by the user equipment can be repeated if necessary [S408 to S410].

Meanwhile, in case that the base station transmits downlink (DL) data to the user equipment, the base station transmits DL assignment to the user equipment via a physical downlink control channel to inform the user equipment that the transmitted data is carried on a prescribed radio resource [S404]. And, the base station is able to transmit data to the user equipment via a radio resource corresponding to this DL assignment message [S405]. In doing so, the DL assignment information transmission and the DL data transmission via the corresponding radio resource can be performed within the same TTI (transmission time interval). Moreover, this DL data transmitting process, as shown in FIG. 4, can be repeatedly performed.

Yet, as mentioned in the foregoing description, since small packets in small size are transmitted frequently and regularly in general according to RTP (real time protocol) in VoIP (voice over internet protocol) service, it is able to apply an efficient radio resource allocation scheme. Namely, SPS radio resource allocation scheme is one of the examples for radio resource allocation schemes optimized for the VoIP service as well. According to this scheme, as mentioned in the foregoing description, first and second steps in the three steps [i.e., (1) Resource request made by a user equipment, (2) Resource allocation conducted by a base station, (3) Data transmission performed by a user equipment according to the resource allocation] for transmitting data to a base station are skipped. In particular, when the VoIP service is initiated, a radio resource is permanently allocated by determining a size and period of packet of RTP in advance. Accordingly, the user equipment is able to perform the step of transmitting data directly according to the radio resource configuration without performing the aforesaid first and second steps, i.e., the radio resource requesting step and the radio resource allocating step. FIG. 5 conceptionally shows this SPS scheme. Namely, according to the SPS scheme, a base station needs not to transmit the radio resource allocation information via the PDCCH each time.

If the user equipment has no more data to transmit in the course of using the radio resource persistently according to the SPS scheme, it informs the base station that there is no more data to transmit. The base station is then able to inform the user equipment of the corresponding SPS radio resource release. Yet, in case that the user equipment operating by HARQ needs to retransmit the initially transmitted data, it may cause a problem related to the SPS radio resource release of the base station.

Accordingly, the present invention is directed to a method of transmitting signals from a user equipment by HARQ (hybrid automatic repeat request) in releasing SPS (semi-persistent scheduling) radio resource substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method of transmitting signals from a user equipment by HARQ in releasing SPS radio resource, by which signals can be efficiently transmitted.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of transmitting a signal, which is transmitted to a base station by a user equipment by HARQ, according to the present invention includes the steps of transmitting uplink data to the base station, receiving HARQ information corresponding to the uplink data and downlink control information from the base station, determining whether the downlink control information contains specific control information, and if the downlink control information contains the specific control information, controlling retransmission of the uplink data not to be performed.

Preferably, the step of controlling the retransmission of the uplink data not to be performed includes the step of setting a feedback value of the HARQ information to ACK.

Preferably, the step of controlling the retransmission of the uplink data not to be performed includes the step of flushing an HARQ buffer of an HARQ process corresponding to the uplink data transmission.

Preferably, the uplink data includes VoIP (voice over internet protocol) data.

Preferably, prior to the SPS activation message receiving step, the method further includes the step of receiving an RRC message containing SPS setting information from the base station.

More preferably, the SPS setting information contains SPS C-RNTI and uplink SPS interval information. In this case, the downlink control information is received via a physical downlink control channel (PDCCH) corresponding to the SPS C-RNTI.

In another aspect of the present invention, a user equipment, which transmits a signal to a base station by HARQ, includes a receiving module receiving downlink control information from the base station, a transmitting module transmitting uplink data using a radio resource according to the downlink control information, and an HARQ entity controlling the transmitting module to transmit the uplink data according to the downlink control information received by the receiving module, wherein if the downlink control information contains an SPS activation message, the HARQ entity controls the transmitting module to transmit the uplink data using the radio resource according to the SPS activation message, wherein the HARQ entity determines whether the downlink control information contains SPS release information, and wherein if the downlink control information contains the SPS release information, the HARQ entity controls retransmission of the uplink data not to be performed.

Preferably, the HARQ entity controls an HARQ operation of at least one HARQ process module. If the downlink control information includes the SPS release information, an HARQ process corresponding to the downlink control information is configured to set a corresponding HARQ feedback value to ACK.

Preferably, the HARQ entity controls HARQ operations of a plurality of HARQ process modules and each of a plurality of the HARQ process modules includes a corresponding HARQ buffer. If the downlink control information includes the SPS release information, the HARQ buffer of an HARQ process corresponding to the downlink control information is configured to be flushed.

Accordingly, the present invention provides the following effects and/or advantages.

First of all, the present invention determines an error situation of HARQ feedback via a specific control signal in the course of transmitting data via a supported radio resource from a user equipment to a base station, thereby preventing unintended HARQ retransmission. In particular, in case that the specific control signal is received, it is able to prevent HARQ retransmission by forcing the HARQ feed back to be determined as ACK or deleting data from an HARQ buffer corresponding to a related HARQ process. Therefore, the present invention prevents collision of radio resource shared with another user equipment, thereby reducing data loss and data delay time.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

FIG. 1 is a schematic diagram of E-UMTS network structure as an example of a mobile communication system;

FIG. 2 and FIG. 3 are diagrams for structures of a radio interface protocol between a user equipment and UTRAN based on the 3GPP radio access network specifications;

FIG. 4 is a diagram for explaining a radio resource allocation scheme;

FIG. 5 is a diagram for explaining SPS scheme;

FIG. 6 and FIG. 7 are diagrams for RRC signaling flow between a user equipment and a base station for SPS configuration;

FIG. 8 is a diagram for explaining an uplink HARQ operation;

FIG. 9 is a diagram for explaining an operation of a user equipment in case of SPS radio resource release;

FIG. 10 is a diagram for explaining an HARQ operating method of a user equipment in case of receiving an SPS radio resource release command according to a first embodiment of the present invention;

FIG. 11 is a diagram for explaining an HARQ operating method of a user equipment in case of receiving an SPS radio resource release command according to a second embodiment of the present invention; and

FIG. 12 is a block diagram for explaining a processor configuration of a user equipment according to one embodiment of the present invention.

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following detailed description of the invention includes details to help the full understanding of the present invention. Yet, it is apparent to those skilled in the art that the present invention can be implemented without these details. For instance, although the following detailed description is made in detail on the assumption that a mobile communication system is the 3GPP LTE system, it is applicable to other prescribed mobile communication systems by excluding unique items of the 3GPP LTE.

Occasionally, the structures and devices known to the public are omitted to avoid conceptional vagueness of the present invention or can be illustrated as block diagrams centering on their core functions.

Besides, in the following description, assume that a terminal is a generic term of such a mobile or fixed user stage device as a user equipment (UE), a mobile station (MS) and the like. Moreover, assume that a base station is a generic name of such a random node of a network end, which communicates with a terminal, as a Node B, an eNnode B and the like.

In the following description, an efficient HARQ signal transmitting method in releasing an SPS radio resource is explained. For this, SPS configuration and release processes and an HARQ operation of a user equipment are explained in detail as follows.

FIG. 6 and FIG. 7 are diagrams for RRC signaling flow between a user equipment and a base station for SPS configuration.

Particularly, FIG. 6 shows a case that an RRC (radio resource control) connection setup between a base station and a user equipment is successfully completed. And, FIG. 7 shows a case that an RRC (radio resource control) connection setup between a base station and a user equipment is not successfully completed.

First of al, a base station is able to send an RRC connection reconfiguration message to a user equipment by RRC signaling [S601, S701]. In this case, the RRC connection reconfiguration message can include a radio resource configuration IE (information element) radioResourceConfigDedicated. And, the radio resource configuration IE can include an SPS configuration IE (sps-config IE). Moreover, the SPS configuration IE can include such basic information for SPS configuration as a radio resource allocation period for SPS and the like. If the user equipment having received this information successfully performs the RRC connection setup, it is able to send an RRC connection reconfiguration complete message to the base station [S602]. On the contrary, if the RRC connection setup is not successfully performed, it is able to adjust the setup between the base station and the user equipment in a manner of exchanging an RRC connection reconfiguration message [S702].

In the following description, an HARQ operation in a user equipment is explained in detail.

FIG. 8 is a diagram for explaining an uplink HARQ operation.

Referring to FIG. 8, in order to transmit data by HARQ to a base station, a user equipment is able to receive UL grant information or uplink scheduling information (hereinafter abbreviated UL scheduling information) from the base station via PDCCH [S801]. Generally, the UL scheduling information can contain a UE identifier (e.g., C-RNTI (Cell- Radio Network Temporary Identifier), semi-persistent scheduling C-RNTI, etc.), a location of an allocated radio resource (resource block assignment), transmission parameters (e.g., modulation scheme, coding scheme, redundancy version, etc.), NDI and the like. In the LTE system, a user equipment has 8 HARQ processes. And, the HARQ processes operate by being synchronous with a transmission time interval (hereinafter abbreviated TTI). In particular, a specific HARQ process can be sequentially assigned according to each data receiving timing point in a manner of using HARQ process #1 in TTI 1, HARQ process #2 in TTI 2, HARQ process #8 in TTI 8 and then using HARQ process #1 in TTI 9 and HARQ process #2 in TTI 10 again.

As mentioned in the above description, since the HARQ processes are synchronously assigned, an HARQ process connected to the TTI, in which the PDCCH for initial transmission of specific data is received, is used for the above data transmission. For instance, assuming that a user equipment receives PDCCH containing UL scheduling information in an N^th TTI, the user equipment transmits data in (N+4)^th TTI. So to speak, HARQ process #K assigned in the (N+4)^th TTI is used for the data transmission. In particular, the user equipment checks incoming UL scheduling information by monitoring the PDCCH each TTI and is then able to transmit data to the base station via PUSCH according to the UL scheduling information [S802].

If receiving the data from the user equipment, the base station stores the received data in a soft buffer and then attempts decoding of the corresponding data. If successfully performing the decoding of the data, the base station transmits an ACK signal to the user equipment. Otherwise, the base station transmits a NACK signal to the user equipment. In FIG. 6, shown is an example that a base station fails in the data decoding and then transmitting a NACK signal on PHICH (physical HARQ indicator channel [S803].

If receiving the ACK signal from the base station, the user equipment detects that the data transmission to the base station is successfully completed and then transmits next data. Yet, like the example shown in FIG. 8, if the user equipment receives the NACM signal from the base station, the user equipment detects that the data transmission to the base station has not been successfully completed and is then able to retransmit the same data in the same or new format [S804].

The HARQ retransmission performed by the user equipment can be non-adaptively operated. In particular, an initial transmission of specific data is possible only if PDCCH containing UL scheduling information is received. Yet, the retransmission is possible despite that the PDCCH is not received. According to the non-adaptive HARQ retransmission, the data is retransmitted without PDCCH reception using the same UL scheduling information of the first transmission in the TTI having a next corresponding HARQ process assigned thereto.

Meanwhile, The HARQ retransmission performed by the user equipment can be adaptively operated. In this case, a transmission parameter for retransmission is received via PDCCH. UL scheduling information contained in the PDCCH may differ from that of the initial transmission according to a channel status. For instance, if the channel status is better than that of the initial transmission, it is able to instruct a transmission at a higher bit rate. On the contrary, if the channel status is not better than that of the initial transmission, it is able to instruct a transmission at a lower bit rate.

If a user equipment receives UL scheduling information via PDCCH, it is able to recognize whether data to be transmitted this time is the data for initial transmission or whether previous data will be retransmitted using an NDI field in the PDCCH. As mentioned in the foregoing description, the NDI field is toggled in the same manner of 0-> 1-> 0-> 1->... each time new data is transmitted. For the retransmission, the NDI field has the same value of the initial transmission. Therefore, the user equipment is able to know a presence or non-presence of data retransmission by comparing the NDI field has the same value of a previously transmitted value.

The user equipment counts a transmission number (CURRENT_TX_NB) each time data is transmitted once by HARQ. If the CURRENT_TX_NB reaches a maximum transmission count set by an RRC layer, the user equipment deletes the data from the HARQ buffer.

Meanwhile, if receiving the retransmitted data, the base station combines the received data with the former data stored in the soft buffer by failing to be previously decoded and then attempts decoding of the combined data. If this decoding is successful, the base station transmits an ACK signal to the user equipment. Otherwise, the base station transmits a NACK signal to the user equipment. The base station repeats the process of sensing the NACK signal and receiving retransmitted data until the data decoding is successfully completed. In the example shown in FIG. 8, the base station combines the data retransmitted in the step S804 with the previously received and stored data and then attempts decoding. If the base station succeeds in the received data decoding, the base station transmits an ACK signal to the user equipment via PHICH [S805]. Moreover, the base station is able to transmit UL scheduling information for next data transmission to the user equipment via PDCCH. In order to n\indicate that the UL scheduling information is used not for the adaptive retransmission but for new data transmission, the base station is able to perform the transmission by toggling the NDI into 1 [S806]. Accordingly, the user equipment is able to transmit new data to the base station via PUSCH corresponding to the received UL scheduling information [S807].

Based on the above description, overall operations of a user equipment in releasing an SPS radio resource are explained as follows.

FIG. 9 is a diagram for explaining an operation of a user equipment in case of SPS radio resource release.

Referring to FIG. 9, as mentioned in the foregoing description with reference to FIG. 6 and FIG. 7, a user equipment is able to receive information related to SPS setup from a base station via RRC signaling [S901]. The RRC signaling information includes an SPS UE identifier (semi-persistent scheduling (SPS) C-RNTI) used for activation and release of SPS allocation or HARQ retransmission using SPS radio resource. Moreover, information on a period for allocation of persistent radio resource and the like can be included in the SPS radio resource allocation information.

The base station is ale to activate the SPS radio resource set via the RRC signaling by transmitting PDCCH masked with the SPS C-RNTI [S902]. In particular, since the SPS radio resource has been activated, the user equipment is able to transmit the data using the activated resource [S903, S904].

According to a buffer status and scheduling policy of the user equipment, the base station is able to release the activated radio resource [S905]. In particular, the base station is able to release the activated SPS radio resource of the user equipment by transmitting a PDCCH masked with SPS-RNTI to the user equipment. In this case, as a release indicator is included in the PDCCH, the user equipment is able to discriminate the PDCCH for the activation and the PDCCH for the release from each other.

In addition, the base station is able to activate the persistent radio resource of the user equipment again according to a buffer status and scheduling policy of the user equipment [S906]. In doing so, the activating method can be performed in the same manner of the step S902.

As mentioned in the foregoing description, the base station keeps monitoring the buffer status of the user equipment. If there is no more data transmission, the base station is able to release the activated SPS radio resource. Yet, such a problem as the following scenario and the like may be caused.

The user equipment is able to transmit data to the base station using the activated SPS radio resource. The base station monitors the buffer status of the user equipment. If there is no more data transmission, the base station is able to release the SPS radio resource. In particular, in the course of transmitting the data stored in the buffer of the user equipment, if there is no more data to be transmitted, the user equipment is able to inform the base station that its buffer status is empty. Accordingly, the base station determines that the buffer status of the user equipment is empty and is then able to give a command for a release of the activated SPS radio resource to the user equipment.

According to the buffer status information of the user equipment and the like, the base station is able to give the release command to the user equipment. Besides, since the information received by the base station from the user equipment is received by HARQ, the base station is able to transmit HARQ ACK as a corresponding feedback to the user equipment. In particular, as a result of successful decoding of the data transmitted by the user equipment, the base station is able to transmit the HARQ ACK to the user equipment.

Yet, the user equipment may determine the HARQ ACK as HARQ NACK due to transmission error of the HARQ feedback. Moreover, the user equipment is able to receive the release command of the SPS radio resource together with the HARQ NACK.

Generally, the release command of the SPS radio resource is used for the purpose of sharing a corresponding radio resource with other user equipments. Namely, if the base station gives a command for the release of SPS radio resource allocation to a specific user equipment, it can be regarded as allocating a radio resource corresponding to the SPS radio resource to another user equipment. In particular, although the specific user equipment receives HARQ NACK and the release command of the SPS radio resource, the user equipment has to perform HARQ retransmission due to the reception of the HARQ NACK in course of the HARQ operation procedure. Therefore, it may cause a problem that collision with another user equipment occurs in using the corresponding radio resource.

For this, in case that a user equipment receives SPS release information via PDCCH in the course of SPS operation, one preferred embodiment of the present invention proposes that a signal retransmission according to an HARQ operation of the user equipment is set not to be performed. In particular, according to a first embodiment of the present invention, if a user equipment receives SPS release information via PDCCH, proposed is that an HARQ feedback value is set to ACK. According to a second embodiment of the present invention, if a user equipment receives SPS release information via PDCCH, proposed is that retransmission is set not to be performed by flushing an HARQ buffer corresponding to a corresponding HARQ process.

According to a first embodiment of the present invention, if a user equipment receives a specific control signal together with an HARQ feedback signal, proposed is that an HARQ feedback is set to HARQ ACK irrespective of a content of the HARQ feedback. In this case, the specific control signal may include an SPS release command received via PDCCH. As mentioned in the foregoing description, since the LTE uplink HARQ is synchronously operative, if HARQ NACK is received from a base station after initial transmission or retransmission, HARQ retransmission is performed after predetermined duration. According to the present embodiment, after a user equipment has received an HARQ feedback, if the user equipment determines an HARQ feedback value, the present invention proposes that a presence or non-presence of a specific control signal having been received by the user equipment is determined. If the specific control signal is received, the user equipment of the present embodiment determines it as HARQ ACK irrespective of the HARQ feedback value.

For example, if receiving HARQ NACK from a base station, a user equipment preferentially determines a presence or non-presence of a reception of the specific control signal in determining a value of an HARQ feedback. If the specific control signal is not received, the user equipment determines the HARQ feedback as HARQ NACK that is an intact value of the HARQ feedback. If the specific control signal is received, the user equipment determines the HARQ feedback not as a value of the HARQ feedback but as HARQ ACK according to the present embodiment. Once it is determined as HARQ ACK, a request for HARQ retransmission is not further made to the user equipment, it is able to avoid the collision with another user equipment in using radio resources.

FIG. 10 is a diagram for explaining an HARQ operating method of a user equipment in case of receiving an SPS radio resource release command according to a first embodiment of the present invention.

Referring to FIG. 10, a base station is able to set information relevant to SPS radio resource allocation for a user equipment via RRC signaling [S1001]. In this case, setting contents about SPS C-RNTI of the user equipment, a period of an SPS radio resource and the like can be contained in the relevant information.

Subsequently, the base station is able to transmit PDCCH masked with the SPS C-RNTI of the user equipment to the user equipment to activate the above-set SPS radio resource [S1002]. Having received this activation command, the user equipment is able to transmit data to the base station using the SPS radio resource [S1003]. In this case, the data transmitted by the user equipment can include VoIP packet data.

Meanwhile, according to SPS scheme, the user equipment is able to sustain an uplink transmission by a prescribed period within a separate UL-grant reception using the SPS radio resource [S1003, S1005, S1007]. To correspond to this uplink data transmission, the base station is able to transmit HARQ feedback information to the user equipment [S1004, S1006, S1008].

Meanwhile, according to a buffer status of the user equipment and a scheduling policy of the base station, the base station determines to release the above-activated SPS radio resource and is then able to transmit a release command of the radio resource via PDCCH masked with SPS C-RNTI of the user equipment to the user equipment [S1009]. In particular, the user equipment transmits data via the SPS radio resource and is then able to receive a command for the activated persistent radio resource release from the base station as soon as receiving an HARQ feedback for the transmitted data. In this case, the present embodiment proposes that the user equipment sets the HARQ feedback to ACK irrespective of a value of the HARQ feedback received in the step S1008 [S1010].

Thus, by preventing a user equipment from performing an unnecessary retransmission in case of SPS radio resource release, the present embodiment avoids wasting radio resources and prevents collision with other user equipments.

According to a second embodiment of the present invention, as mentioned in the foregoing description, if a user equipment receives a specific control signal together with an HARQ feedback, proposed is that data in an HARQ buffer is set to be flushed. As mentioned in the foregoing description, since LTE uplink HARQ is synchronously operative, when a user equipment receives HARQ NACK from a base station after initial transmission or retransmission, if data exists in an HARQ buffer corresponding to a corresponding HARQ process, the user equipment performs HARQ retransmission. Yet, according to the present embodiment, if a user equipment receives a specific control signal, the user equipment deletes data from an HARQ buffer, the user equipment is unable to further perform the HRAQ retransmission. Therefore, it is able to prevent an unintended HARQ retransmission.

Particularly, an HARQ process for flushing data from an HARQ buffer can be limited to a process for transmitting data via a persistent radio resource. For instance, when 8 HARQ processes exist, assuming that HARQ process #2, HARQ process #4 and HARQ process #6 are used in transmitting data via a persistent radio resource, if the specific control signal is received, data are flushed from HARQ buffers corresponding to the HARQ process #2, the HARQ process #4 and the HARQ process #6, respectively.

FIG. 11 is a diagram for explaining an HARQ operating method of a user equipment in case of receiving an SPS radio resource release command according to a second embodiment of the present invention.

Basically, the process shown in FIG. 11 is equivalent to the former process described with reference to FIG. 10 except the step S1110. In particular, a base station sends an RRC message for SPS radio resource allocation to a user equipment [S1101] and is then able to activate an SPS radio resource by transmitting a PDCCH signal masked with SPS C-RNTI for the allocated SPS radio resource activation [S1102].

Subsequently, the user equipment transmits Uplink data such as VoIP packet without a separate reception of UL-grant reception using the allocated SPS radio resource and is then able to receive an HARQ feedback signal from the base station [S1103 to S1108].

Meanwhile, according to a buffer status of the user equipment and a scheduling policy of the base station, the base station determines to release the activated SPS radio resource and is then able to transmit a release command of the radio resource via PDCCH masked with SPS C-RNTI of the user equipment to the user equipment [S1109]. Thus, the present embodiment proposes that the user equipment, which receives a PDCCH signal including the SPS radio resource release command, flushes data from an HARQ buffer corresponding to an HARQ process for performing the data transmission via the SPS radio resource [S1110]. Therefore, by flushing the HARQ buffer data of the HARQ process corresponding to the transmission of the data by SPS in case of SPS radio resource release, the present embodiment avoids wasting radio resources and prevents collision with other user equipments.

The above mentioned operation schemes of the user equipment is suitable for solving the problems occurring in the above situation described with reference to FIG. 9 and also has the following advantage. First of all, in case of receiving a specific control signal, i.e., an SPS radio resource release command, an HARQ entity (or a specific HARQ process module) is configured to sets a corresponding HARQ feedback signal to ACK or flush data from a corresponding HARQ buffer. Therefore, an HARQ operation can be made clear.

In the following description, a configuration of a user equipment according to the present invention is explained based on the above descriptions.

First of all, in a mobile communication system, a user equipment can include an input means, a display module and the like as well as a processor for processing signals. Particularly, a configuration of the processor responsible for substantial signal processing of the user equipment is described as follows.

FIG. 12 is a block diagram for explaining a configuration of a processor in a user equipment according to one embodiment of the present invention.

Referring to FIG. 12, a processor in a user equipment is ale to have various layer structures described with reference to FIG. 2 and FIG. 3. A physical layer module 1210 and a MAC layer module 1220 of the user equipment are intensively explained in the following description of the present embodiment. The physical layer module 1210 is able to include a receiving module 1211 configured receive downlink control information from a base station and a transmitting module 1212 configured to transmit uplink data using a radio resource according to the downlink control information received by the receiving module 1211.

The MAC layer module 1220 of the user equipment can include an HARQ entity 1221 controlling the transmitting module 1212 to transmit uplink data by HARQ according to the downlink control information received by the receiving module 1211. In particular, the HARQ entity 1221 controls HARQ operations of a plurality of HARQ process modules 1222. And, a plurality of the HARQ process modules 1222 can include corresponding HARQ buffers 1223, respectively.

In case that the downlink control information contains an SPS activation message, the HARQ entity 1221 of the user equipment according to the present embodiment controls the transmitting module 1212 to transmit uplink data using a radio resource according to the SPS activation message. Moreover, the HARQ entity 1221 determines whether the downlink control information contains SPS release information. If the downlink control information contains the SPS release information, it is proposed that the HARQ entity 1221 controls retransmission of uplink data not to be performed.

In particular, in case that the downlink control information contains the SPS release information, the HARQ process module 1222 corresponding to the downlink control information can be configured to set a corresponding feedback value to ACK. Moreover, in case that the downlink control information contains the SPS release information, it is able to configure to flush the HARQ buffer 1223 of the HARQ process module 1222 corresponding to the downlink control information. For example, if the HARQ process modules (#0, #2 and #6) 1222 are used in transmitting data by SPS, it is able to set the data of the corresponding buffer 1223 to be flushed.

Using the above-configured UE processor, it is able to efficiently set HARQ operation of a user equipment in case of SPS radio resource release.

Although the above descriptions are made with reference to a specific case that a user equipment receives an SPS radio resource release command from a base station, they are applicable to a scheme of setting to prevent retransmission in case of receiving a specific control signal from the base station in a similar situation.

As mentioned in the foregoing description, the retransmission prevention in HARQ operation can be performed by setting an HARQ feedback signal to ACK or flushing a corresponding HARQ buffer.

The above-described transmission/reception technology and terminal configuration thereof are explained mainly with reference to the example that they are applied to the 3GPP LTE system. Further, they are applicable to various mobile communication systems having the similar process as well as to the 3GPP LTE system.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

A method of transmitting a signal to a base station by a user equipment using a HARQ scheme, the method comprising:

transmitting uplink data to the base station;

receiving HARQ information corresponding to the uplink data and downlink control information from the base station;

determining whether the downlink control information contains specific control information; and

controlling a retransmission of the uplink data not to be performed, when the downlink control information contains the specific control information.
The method of claim 1, wherein the base station performs scheduling according to a SPS (semi-persistent scheduling) scheme, and

wherein the specific control information comprises SPS release information.
The method of claim 2, further comprising:

receiving a SPS activation message from the base station before transmitting the uplink data,

wherein the uplink data is transmitted using a radio resource according to the SPS activation message.
The method of claim 1, wherein controlling the retransmission of the uplink data not to be performed comprises setting a feedback value of the HARQ information to ACK.
The method of claim 1, wherein controlling the retransmission of the uplink data not to be performed comprises flushing an HARQ buffer of an HARQ process corresponding to the uplink data transmission.
The method of claim 2, wherein the uplink data comprises VoIP (voice over internet protocol) data.
The method of claim 2, wherein the base station, which had transmitted the SPS release information to the user equipment, allocates a radio resource allocated to the user equipment for the uplink data transmission to another user equipment.
The method of claim 3, further comprising:

receiving an RRC message containing SPS setting information from the base station prior to receiving the SPS activation message.
The method of claim 8, wherein the SPS setting information contains SPS C-RNTI (semi-persistent scheduling Cell Radio Network Temporary Identifier) and uplink SPS interval information.
The method of claim 9, wherein the downlink control information is received via a physical downlink control channel (PDCCH) corresponding to the SPS C-RNTI.
A user equipment transmitting a signal to a base station using a HARQ scheme, the user equipment comprising:

a receiving module receiving downlink control information from the base station;

a transmitting module transmitting uplink data using a radio resource according to the downlink control information; and

an HARQ entity controlling the transmitting module to transmit the uplink data according to the downlink control information received by the receiving module,

wherein the HARQ entity controls the transmitting module to transmit the uplink data using the radio resource according to first control information, when the downlink control information contains the first control information,

wherein the HARQ entity determines whether the downlink control information contains second control information, and

wherein the HARQ entity controls a retransmission of the uplink data not to be performed, when the downlink control information contains second control information.
The terminal of claim 11, wherein the base station performs scheduling according to a SPS (semi-persistent scheduling) scheme, and

wherein the second control information comprises SPS release information.
The terminal of claim 12, wherein the first control information comprises a SPS activation message, and

wherein the HARQ entity controls the transmitting module to transmit the uplink data using the radio resource according to the SPS activation message.
The terminal of claim 12, wherein the HARQ entity controls a HARQ operation of at least one HARQ process module, and

wherein a HARQ process corresponding to the downlink control information is configured to set a corresponding HARQ feedback value to ACK, when the downlink control information includes the SPS release information.
The terminal of claim 12, wherein the HARQ entity controls HARQ operations of a plurality of HARQ process modules,

wherein each of the plurality of the HARQ process modules includes a corresponding HARQ buffer, and

wherein the HARQ buffer of a HARQ process corresponding to the downlink control information is configured to be flushed, when the downlink control information includes the SPS release information.
The terminal of claim 12, wherein the uplink data comprises VoIP (voice over internet protocol) data.
The terminal of claim 12, wherein the user equipment receives a RRC message containing SPS setting information from the base station via the receiving module.
The terminal of claim 17, wherein the SPS setting information contains a SPS C-RNTI and uplink SPS interval information.
The terminal of claim 18, wherein the receiving module receives the downlink control information via a physical downlink control channel (PDCCH) corresponding to the SPS C-RNTI.