Method of an uplink HARQ operation at an expiry of time alignment timer

Abstract

Disclosed is the radio (wireless) communication system providing a radio communication service and the terminal, and more particularly, to a method of an uplink HARQ (Hybrid Automatic Repeat reQuest) operation at an expiry of time alignment timer in an Evolved Universal Mobile Telecommunications System (E-UMTS) evolved from the Universal Mobile Telecommunications System (UMTS) or a Long Term Evolution (LTE) system.

Claims

1. A method of processing data for a HARQ (hybrid automatic repeat request) operation in a wireless communication system, the method comprising: storing.Iadd., by a user equipment (UE), .Iaddend.a data unit into a corresponding HARQ buffer; and flushing.Iadd., by the UE, .Iaddend.the stored data unit in the corresponding HARQ buffer .Iadd.and performing, by the UE, a release procedure for at least one of a physical uplink control channel (PUCCH) or sounding reference symbol (SRS) resource, .Iaddend.when a timer expires, wherein the timer is a time alignment timer (TAT) which is used to control how long .[.a.]. .Iadd.the .Iaddend.UE .[.(User Equipment) is considered to have.]. .Iadd.has .Iaddend.an uplink time that is aligned, wherein the stored data unit in the corresponding HARQ buffer is flushed as a result of .[.the expired time.]. .Iadd.an expiration of the timer, wherein the timer is used to indicate a time duration .Iaddend.for which the UE .[.is considered to have.]. .Iadd.has .Iaddend.the uplink time that is aligned, wherein the stored data unit is a Medium Access Control (MAC) Protocol Data Unit (PDU), and wherein the TAT is started when a time advance command (TAC) is received from the network.

2. The method of claim 1, further comprising: receiving an uplink grant from a network; and generating a data unit based on the received uplink grant.

3. The method of claim 2, wherein the uplink grant is received on a PDCCH (Physical Downlink Control Channel).

4. The method of claim 2, wherein the uplink grant includes at least one of uplink scheduling information, a C-RNTI (Cell-Radio Network Temporary Identifier), .[.and.]. .Iadd.or .Iaddend.a Semi-persistent Scheduling C-RNTI.

5. The method of claim 2, wherein any configured downlink assignments and the uplink grant are cleared when the timer expires.

6. The method of claim 1, wherein the corresponding HARQ buffer is one of all HARQ buffers.

.[.7. The method of claim 6, wherein the all HARQ buffers are flushed when the timer expires..].

8. The method of claim 1, wherein a .[.PUCCH/SRS resources are released when the timer expires.]. .Iadd.RRC (Radio Resource Control) layer is notified to release the at lease one of the PUCCH or SRS resource.Iaddend..

9. The method of claim 7, wherein a RRC (Radio Resource Control) layer is notified to release the PUCCH/SRS resources.

10. A user equipment (UE) .[.using.]. .Iadd.configured to use .Iaddend.a HARQ (Hybrid Automatic Repeat reQuest) operation in a wireless communication system, the UE comprising: a controller configured to: store a data unit into a corresponding HARQ buffer; and flush the stored data unit in the corresponding HARQ buffer .Iadd.and perform a release procedure for at least one of a physical uplink control channel (PUCCH) or sounding reference symbol (SRS) resource, .Iaddend.when a timer expires, wherein the timer is a time alignment timer (TAT) which is used to control how long the UE .[.is considered to have.]. .Iadd.has .Iaddend.an uplink time that is aligned, wherein the stored data unit in the corresponding HARQ buffer is flushed as a result of .[.the expired time.]. .Iadd.an expiration of the timer, wherein the timer is used to indicate a time duration .Iaddend.for which the UE is considered to have the uplink time that is aligned, wherein the stored data unit is a Medium Access Control (MAC) Protocol Data Unit (PDU), and wherein the TAT is started when a time advance command (TAC) is received from the network.

11. The user equipment (UE) of claim 10, wherein the controller .Iadd.is .Iaddend.further configured to: receive an uplink grant from a network, and generate a data unit based on the received uplink grant.

12. The user equipment (UE) of claim 11, wherein the uplink grant is received on a PDCCH (Physical Downlink Control Channel).

13. The user equipment (UE) of claim 11, wherein the uplink grant includes at least one of uplink scheduling information, a C-RNTI (Cell-Radio Network Temporary Identifier), and a Semi-persistent Scheduling C-RNTI.

14. The user equipment (UE) of claim 11, wherein any configured downlink assignments and the uplink grant are cleared when the timer expires.

15. The user equipment (UE) of claim 10, wherein the corresponding HARQ buffer is one of all HARQ buffers.

.[.16. The user equipment (UE) of claim 15, wherein the all HARQ buffers are flushed when the timer expires..].

17. The user equipment (UE) of claim 10, wherein a .[.PUCCH/SRS resources are released when the timer expires.]. .Iadd.RRC (Radio Resource Control) layer is notified to release the at least one of the PUCCH or SRS resource.Iaddend..

18. The user equipment (UE) of claim 17, wherein a RRC (Radio Resource Control) layer is notified to release the PUCCH/SRS resources.

.Iadd.19. The method of claim 1, wherein the data unit is used for a retransmission when the retransmission for the data unit is indicated to the UE. .Iaddend.

.Iadd.20. The user equipment (UE) of claim 10, wherein the data unit is used for a retransmission when the retransmission for the data unit is indicated to the UE. .Iaddend.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an exemplary network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS) as a mobile communication system to which a related art and the present invention are applied;

(2) FIG. 2 shows an exemplary view of related art control plane architecture of a radio interface protocol between a terminal and an E-UTRAN;

(3) FIG. 3 shows an exemplary view of related art user plane architecture of a radio interface protocol between a terminal and an E-UTRAN;

(4) FIG. 4 is an exemplary view showing a HARQ operation method for an effective data transmission;

(5) FIG. 5 shows an exemplary view of a contention based random access procedure;

(6) FIG. 6 shows an exemplary view of a non-contention based random access procedure;

(7) FIG. 7 shows an exemplary view of flushing data in HARQ buffer at an expiry of time alignment timer (TAT) according to the present invention;

(8) FIG. 8 shows an exemplary view of flushing data in HARQ buffer when a time alignment timer (TAT) is not running according to the present invention; and

(9) FIG. 9 shows an exemplary view of flushing data in HARQ buffer by receiving a new timing advance command (TAC) when a time alignment timer (TAT) is not running according to the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

(10) One aspect of this disclosure relates to the recognition by the present inventors about the problems of the related art as described above, and further explained hereafter. Based upon this recognition, the features of this disclosure have been developed.

(11) Although this disclosure is shown to be implemented in a mobile communication system, such as a UMTS developed under 3GPP specifications, this disclosure may also be applied to other communication systems operating in conformity with different standards and specifications.

(12) Hereinafter, description of structures and operations of the preferred embodiments according to the present invention will be given with reference to the accompanying drawings.

(13) In general, a terminal (or UE) may perform a random access procedure in the following cases: 1) when the terminal performs an initial access because there is no RRC Connection with a base station (or eNB), 2) when the terminal initially accesses to a target cell in a handover procedure, 3) when it is requested by a command of a base station, 4) when there is uplink data transmission in a situation where uplink time synchronization is not aligned or where a specific radio resource used for requesting radio resources is not allocated, and 5) when a recovery procedure is performed in case of a radio link failure or a handover failure.

(14) In the LTE system, the base station allocates a dedicated random access preamble to a specific terminal, and the terminal performs a non-contention random access procedure which performs a random access procedure with the random access preamble. In other words, there are two procedures in selecting the random access preamble: one is a contention based random access procedure in which the terminal randomly selects one within a specific group for use, another is a non-contention based random access procedure in which the terminal uses a random access preamble allocated only to a specific terminal by the base station. The difference between the two random access procedures is that whether or not a collision problem due to contention occurs, as described later. And, the non-contention based random access procedure may be used, as described above, only in the handover procedure or when it is requested by the command of the base station.

(15) Based on the above description, FIG. 5 shows an operation procedure between a terminal and a base station in a contention based random access procedure.

(16) First, a terminal in the contention based random access randomly may select a random access preamble within a group of random access preambles indicated through system information or a handover command, may select PRACH resources capable of transmitting the random access preamble, and then may transmit the selected random access preamble to a base station (Step 1).

(17) After transmitting the random access preamble, the terminal may attempt to receive a response with respect to its random access preamble within a random access response reception window indicated through the system information or the handover command (Step 2). More specifically, the random access response information is transmitted in a form of MAC PDU, and the MAC PDU may be transferred on the Physical Downlink Shared Channel (PDSCH). In addition, the Physical Downlink Control Channel (PDCCH) is also transferred such that the terminal appropriately receives information transferred on the PDSCH. That is, the PDCCH may include information about a terminal that should receive the PDSCH, frequency and time information of radio resources of the PDSCH, a transfer format of the PDSCH, and the like. Here, if the PDCCH has been successfully received, the terminal may appropriately receive the random access response transmitted on the PDSCH according to information of the PDCCH. The random access response may include a random access preamble identifier (ID), an UL Grant, a temporary C-RNTI, a Time Alignment Command, and the like. Here, the random access preamble identifier is included in the random access response in order to notify terminals to which information such as the UL Grant, the temporary C-RNTI, and the Time Alignment Command would be valid (available, effective) because one random access response may include random access response information for one or more terminals. Here, the random access preamble identifier may be identical to the random access preamble selected by the terminal in Step 1.

(18) If the terminal has received the random access response valid to the terminal itself, the terminal may process each of the information included in the random access response. That is, the terminal applies the Time Alignment Command, and stores the temporary C-RNTI. In addition, the terminal uses the UL Grant so as to transmit data stored in a buffer of the terminal or newly generated data to the base station (Step 3). Here, a terminal identifier should be essentially included in the data which is included in the UL Grant (message 3). This is because, in the contention based random access procedure, the base station may not determine which terminals are performing the random access procedure, but later the terminals should be identified for contention resolution. Here, two different schemes may be provided to include the terminal identifier. A first scheme is to transmit the terminal's cell identifier through the UL Grant if the terminal has already received a valid cell identifier allocated in a corresponding cell prior to the random access procedure. Conversely, the second scheme is to transmit the terminal's unique identifier (e.g., S-TMSI or random ID) if the terminal has not received a valid cell identifier prior to the random access procedure. In general, the unique identifier is longer than the cell identifier. In Step 3, if the terminal has transmitted data through the UL Grant, the terminal starts the contention resolution timer.

(19) After transmitting the data with its identifier through the UL Grant included in the random access response, the terminal waits for an indication (instruction) of the base station for the contention resolution. That is, the terminal attempts to receive the PDCCH so as to receive a specific message (Step 4). Here, there are two schemes to receive the PDCCH. As described above, if the terminal identifier transmitted via the UL Grant is the cell identifier, the terminal attempts to receive the PDCCH by using its own cell identifier. If the terminal identifier transmitted via the UL Grant is its unique identifier, the terminal attempts to receive the PDCCH by using the temporary C-RNTI included in the random access response. Thereafter, for the former, if the PDCCH (message 4) is received through its cell identifier before the contention resolution timer is expired, the terminal determines that the random access procedure has been successfully (normally) performed, thus to complete the random access procedure. For the latter, if the PDCCH is received through the temporary cell identifier before the contention resolution timer is expired, the terminal checks data (message 4) transferred by the PDSCH that the PDCCH indicates. If the unique identifier of the terminal is included in the data, the terminal determines that the random access procedure has been successfully (normally) performed, thus to complete the random access procedure.

(20) FIG. 6 shows an operation procedure between a terminal and a base station in a non-contention based random access procedure. As compared with the contention based random access procedure, the random access procedure is determined to be successfully performed by receiving the random access response information in the non-contention based random access procedure, thus to complete the random access process.

(21) In general, the non-contention based random access procedure may be performed in the following two cases: one is the handover procedure, and the other is a request by the command of the base station. To be certain, the contention based random access procedure may also be performed in those two cases. First, for the non-contention based random access procedure, it is important to receive, from the base station, a dedicated random access preamble without having any possibility of contention. Here, a handover command and a PDCCH command may be used to assign the random access preamble. Then, after the random access preamble dedicated to only the terminal itself has been assigned from the base station, the terminal transmits the preamble to the base station. Thereafter, the method for receiving the random access response information is the same as that in the above-described contention based random access procedure.

(22) As aforementioned in this disclosure, the present invention proposes a method of flushing data in all HARQ buffer of the terminal when a time alignment timer (TAT) is not running or is expired.

(23) FIG. 7 shows an exemplary view of flushing data in HARQ buffer at an expiry of time alignment timer (TAT) according to the present invention. As illustrated in FIG. 7, the present invention proposes to flush all HARQ buffers at the TAT expiry. More detailed description of FIG. 7 will be given as following. First, the terminal may receive a PDCCH (Physical Downlink Control Channel) including an uplink scheduling information (i.e. UL grant) for a data transmission of an uplink. Here, the PDCCH may include a C-RNTI (Cell-Radio Network Temporary Identifier) or Semi-Persistent Scheduling C-RNTI (SPS C-RNTI). Thereafter, the terminal may generate a MAC PDU (referred as MAC PDU-1 hereafter) according to the received uplink scheduling information, and may store the generated MAC PDU-1 in a corresponding HARQ buffer. Further, the terminal may transmit the stored MAC PDU-1 to the base station at a transmission timing of a corresponding HARQ process. After the MAC PDU-1 is transmitted, the terminal may wait to receive a HARQ feedback from the base station. At this moment, the time alignment timer (TAT) of the terminal may expire. According to the present invention, the terminal may flush data in all HARQ buffers including a HARQ buffer having the MAC PDU-1 at the time of TAT expiry.

(24) FIG. 8 shows an exemplary view of flushing data in HARQ buffer when a time alignment timer (TAT) is not running according to the present invention. As illustrated in FIG. 8, the present invention proposes to flush all HARQ buffers when the TAT is not running. More detailed description of FIG. 8 will be given as following. After the TAT is expired, the terminal may flush data in all HARQ buffers. Here, a current TAT of the terminal is not running and there is no data in all HARQ buffers. In this case, the terminal may further receive a PDCCH including an uplink scheduling information for an uplink data transmission. Here, the PDCCH may include a C-RNTI (Cell-Radio Network Temporary Identifier) or Semi-Persistent Scheduling C-RNTI (SPS C-RNTI). Thereafter, the terminal may generate a MAC PDU (referred as MAC PDU-2 hereafter) according to the received uplink scheduling information, and may store the generated MAC PDU-2 in a corresponding HARQ buffer. However, according to the present invention, the terminal may flush data in all HARQ because the TAT of the terminal is not running.

(25) FIG. 9 shows an exemplary view of flushing data in HARQ buffer by receiving a new timing advance command (TAC) when a time alignment timer (TAT) is not running according to the present invention. As illustrated in FIG. 9, the present invention proposes to flush all HARQ buffers when the terminal receives a new TAC while a TAT of the terminal is not running after its expiration. More detailed description of FIG. 9 will be given as following. After the TAT is expired, the terminal may flush data in all HARQ buffers. While the TAT is not running, the terminal may further receive a PDCCH including an uplink scheduling information for an uplink data transmission. Here, the PDCCH may include a C-RNTI (Cell-Radio Network Temporary Identifier) or Semi-Persistent Scheduling C-RNTI (SPS C-RNTI). Thereafter, the terminal may generate a MAC PDU (referred as MAC PDU-3 hereafter) according to the received uplink scheduling information, and may store the generated MAC PDU-3 in a corresponding HARQ buffer. The terminal may attempt to transmit the MAC PDU-3 to the base station. However, since the TAT is not running, the terminal may not transmit the MACE PDU-3. Here, the MAC PDU-3 is kept in the corresponding HARQ buffer. At this moment, the terminal may receive a new TAC. For example, the terminal may receive the new TAC by a random access response during the random access channel (RACH) procedure. Once the new TAC is received by the terminal, the terminal may flush data in all HARQ buffer and may restart the TAT.

(26) According to the present invention, when the time alignment timer expires, all HARQ buffers (i.e., all uplink HARQ buffers) are flushed and the next transmission for each process is considered as the very first transmission. Namely, the terminal may notify RRC of PUCCH/SRS release and may clear any configured downlink assignment and uplink grants.

(27) The present disclosure may provide a method of processing data for a HARQ (Hybrid Automatic Repeat Request) operation in a wireless communication system, the method comprising: receiving an uplink Grant from a network; generating a data unit based on the received uplink grant; storing the generated data unit into a plurality of buffers; and flushing the stored data unit in the plurality of buffers when a timer expires, wherein the timer is a Time Alignment Timer (TAT), the uplink grant is received on a PDCCH (Physical Downlink Control Channel), the uplink grant includes at least one of uplink scheduling information, a C-RNTI (Cell-Radio Network Temporary Identifier), and a Semi-persistent Scheduling C-RNTI, the data unit is MAC PDU (Medium Access Control Protocol Data Unit), and the plurality of buffers is all uplink HARQ buffers.

(28) It can be also said that the present invention may provide a method of processing data for a HARQ (Hybrid Automatic Repeat Request) operation in a wireless communication system, the method comprising: receiving an uplink Grant from a network; generating a data unit based on the received uplink grant; storing the generated data unit into a plurality of buffers; and flushing the stored data in the plurality of buffers when the timer is not running, wherein the timer is a time Alignment timer (TAT), the uplink grant is received on a PDCCH (Physical Downlink Control Channel), the uplink grant includes at least one of uplink scheduling information, a C-RNTI (Cell-Radio Network Temporary Identifier), and a Semi-persistent Scheduling C-RNTI, the data unit is MAC PDU (Medium Access Control Protocol Data Unit), and the plurality of buffers is all uplink HARQ buffers.

(29) Also, the present invention may provide a method of processing data fora HARQ (Hybrid Automatic Repeat Request) operation in a wireless communication system, the method comprising: receiving an uplink Grant from a network; generating a data unit based on the received uplink grant; storing the generated data unit into a plurality of buffers; determining whether or not a timer is running; determining whether a command for starting the timer is received; and flushing the stored data in the plurality of buffers when it is determined that the timer is not running and the command is received, wherein the command is a Timing Advance Command (TAC).

(30) Although the present disclosure is described in the context of mobile communications, the present disclosure may also be used in any wireless communication systems using mobile devices, such as PDAs and laptop computers equipped with wireless communication capabilities (i.e. interface). Moreover, the use of certain terms to describe the present disclosure is not intended to limit the scope of the present disclosure to a certain type of wireless communication system. The present disclosure is also applicable to other wireless communication systems using different air interfaces and/or physical layers, for example, TDMA, CDMA, FDMA, WCDMA, OFDM, EV-DO, Wi-Max, Wi-Bro, etc.

(31) The exemplary embodiments may be implemented as a method, apparatus or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. The term “article of manufacture” as used herein refers to code or logic implemented in hardware logic (e.g., an integrated circuit chip, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), etc.) or a computer readable medium (e.g., magnetic storage medium (e.g., hard disk drives, floppy disks, tape, etc.), optical storage (CD-ROMs, optical disks, etc.), volatile and non-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.).

(32) Code in the computer readable medium may be accessed and executed by a processor. The code in which exemplary embodiments are implemented may further be accessible through a transmission media or from a file server over a network. In such cases, the article of manufacture in which the code is implemented may comprise a transmission media, such as a network transmission line, wireless transmission media, signals propagating through space, radio waves, infrared signals, etc. Of course, those skilled in the art will recognize that many modifications may be made to this configuration without departing from the scope of the present disclosure, and that the article of manufacture may comprise any information bearing medium known in the art.

(33) As the present disclosure may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.