HK1177564A - Wireless transmit/receive unit, method and node-b - Google Patents

Abstract

The present invention provided a wireless transmit/receive unit (WTRU), a method and a Node-B. The WTRU comprises: at least one circuit configured to receive radio resource control (RRC) configuration information from a wireless network; the RRC configuration information indicates for each medium access control for dedicated channel (MAC-d) flow, a limit of a number of hybrid automatic repeat request (HARQ) retransmissions for each MAC-d flow; the at least one circuit is further configured to generate a medium access control for enhanced dedicated channel (MAC-e) protocol data unit (PDU), the at least one circuit is further configured to transmit the MAC-e PDU using at least one of a plurality of synchronous HARQ processes; each of the plurality of synchronous HARQ processes is configured to retransmit a MAC-e PDU that is not positively acknowledged on a condition that the limit of the number of HARQ retransmissions for a MAC-d flow of the MAC-e PDU is not reached; the at least one circuit is further configured to transmit with the MAC-e PDU an indication of a transport block size associated with the MAC-e PDU.

Description

Wireless transmitting/receiving unit, method and node B

The present application is a divisional application of the chinese patent application with the application number of 200580018200.9, the application date of 2005, 6/3, entitled "method and apparatus for dynamically adjusting data transmission parameters and controlling H-ARQ processes".

Technical Field

The present invention relates to a wireless communication system including a wireless transmit/receive unit (WTRU) and a node-B, and more particularly, to a method and apparatus for dynamically adjusting data transmission parameters, such as Modulation and Coding Scheme (MCS) and Transport Block Set (TBS) size, and allocating and releasing hybrid automatic repeat request (H-ARQ) procedures for controlling the WTRU and the node-B.

Background

In third generation cellular systems, adaptive modulation and coding (AM & C) and H-ARQ mechanisms have been developed to integrate enhanced uplink (ED) operations, which are designed to provide lower transmission latency, higher throughput, and more efficient use of physical resources.

The AM & C mechanism allows the MCS to be dynamically adjusted on a Transmission Time Interval (TTI) basis, whereby the MCS is selected to allow more efficient use of radio resources and to provide the highest possible data rate for each TTI. A less robust MCS uses less physical resources but is more error prone, and a more robust MCS uses more physical resources but provides more protection against errors.

The H-ARQ scheme is used to generate transmissions and retransmissions with lower latency, and the main direction of the H-ARQ scheme is to soft combine the data received in the failed transmission with the subsequent retransmissions to increase the probability of successful reception, and to use Chase Combining (CC) or Incremental Redundancy (IR). When using CC, the same MCS is chosen for retransmission, and when using IR, a more robust MCS is used at each retransmission.

Disclosure of Invention

The invention is implemented in a wireless communication system that includes a WTRU transmitting data to a node-B. Data transmission parameters like TB size are dynamically adjusted on a TTI basis, optionally the MCS may also be adjusted. H-ARQ processes for controlling data transmission between the WTRU and the node-B, depending on the assignment and release required. The WTRU transmits and retransmits data to the node-B via an enhanced uplink (ED) dedicated channel (E-DCH) in accordance with the feedback information received from the node-B. The WTRU stores transmission data on a queue and determines a transmission status for the data, the transmission status being set by a controller in the WTRU to "new transmission", "successful transmission", "retransmission", and "restart transmission". During each TTI, the WTRU initiates an EU transmission to the node-B, which explicitly or implicitly identifies the number of retransmissions, a new data indication, an assigned H-ARQ process, a TBS size, and optionally an MCS.

When the data is new, the data transmission status is set to "new transmission" by the controller in the WTRU. When an Acknowledgement (ACK) message is received from the node B, it is set to "successful transmission". Is either a non-acknowledgement (NACK) message from the node B or no response from the node B corresponding to the new data transmission, is set to "retransmit. When the retransmission count exceeds a predetermined retransmission maximum, the method is selectively set to "restart transmission".

If the transmission status is "" new transmission "", an initial H-ARQ process is assigned. If the transmission status is "retransmission", the same H-ARQ process is assigned, and the retransmission counter is incremented. If the transmission status is "successful transmission", the H-ARQ process is released. If the transmission status is "restart transmission", which is optional, an-H-ARQ procedure is assigned, the retransmission counter is initialized, and a New Data Indicator (NDI) is incremented.

The present invention provides a wireless transmit/receive unit (WTRU) comprising: at least one circuit configured to receive Radio Resource Control (RRC) configuration information from a wireless network; wherein the RRC configuration information indicates, for each dedicated channel medium access control (MAC-d) flow, a limit on a number of hybrid automatic repeat request (HARQ) retransmissions for each MAC-d flow; wherein the at least one circuit is further configured to generate an enhanced dedicated channel medium access control (MAC-e) Protocol Data Unit (PDU), wherein the at least one circuit is further configured to transmit the MAC-e PDU using at least one of a plurality of synchronous HARQ processes; wherein each of the plurality of synchronous HARQ processes is configured to retransmit a MAC-e PDU that is not acknowledged without reaching the limit of the number of HARQ retransmissions for a MAC-d flow of the MAC-e PDU; and wherein the at least one circuit is further configured to transmit an indication of a transport block size of the MAC-e PDU associated with the MAC-e PDU.

The invention also provides a method comprising: receiving, by a wireless transmit/receive unit, Radio Resource Control (RRC) configuration information from a wireless network; wherein the RRC configuration information indicates, for each dedicated channel medium access control (MAC-d) flow, a limit on a number of hybrid automatic repeat request (HARQ) retransmissions for each MAC-d flow; generating an enhanced dedicated channel medium access control (MAC-e) Protocol Data Unit (PDU); and transmitting the MAC-e PDU using at least one of a plurality of synchronous HARQ processes of the WTRU; wherein each of the plurality of synchronous HARQ processes retransmits a MAC-e PDU that has not been acknowledged without reaching the limit on the number of HARQ retransmissions for a MAC-d flow of the MAC-e PDU; wherein each MAC-e PDU is transmitted with an indication of a transport block size associated with the MAC-e PDU.

The present invention also provides a node B, including: at least one circuit configured to transmit a signal comprising Radio Resource Control (RRC) configuration information to a wireless transmit/receive unit (WTRU); wherein the RRC configuration information indicates, for each dedicated channel medium access control (MAC-d) flow, a limit on a number of hybrid automatic repeat request (HARQ) retransmissions for each MAC-d flow; wherein the at least one circuit is further configured to receive a MAC-e Protocol Data Unit (PDU) from the WTRU using at least one of a plurality of synchronous HARQ processes; and wherein the at least one circuit is further configured to receive an indication of a transport block size of the MAC-e PDU associated with the MAC-e PDU.

Drawings

The invention may be understood in more detail by reference to the following description of a preferred embodiment, given as an example, and the accompanying drawings, in which:

FIG. 1 is a block diagram of a wireless communication system operating in accordance with the present invention;

FIG. 2 is a process flow diagram of an initialization and release H-ARQ process in accordance with the present invention;

FIG. 3 is a flowchart of a process including steps for performing a CC method in accordance with the present invention; and

FIG. 4 is a flowchart of a process including steps for performing an IR method in accordance with the present invention.

Detailed Description

The term "WTRU" as used herein includes, but is not limited to, a User Equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terminology "node B" includes but is not limited to a base station, site controller, access point, or any other interfacing device in a wireless environment.

The features of the present invention may be integrated into an Integrated Circuit (IC) or may be configured on a circuit comprising a plurality of interconnected components.

Fig. 1 is a block diagram of a wireless communication system 100 according to the present invention, the system 100 including a WTRU102, a node-B104 and a Radio Network Controller (RNC) 106. The WTRU102 transmits data via an E-DCH108 with a transmitter 120 and receives feedback from the node-B104 via a Downlink (DL) signaling channel 110 with a receiver 122, which is based on a one-to-one initialized H-ARQ process. When the node-B is unable to decode the data sent by the WTRU102, the node-B transmits a NACK message to the WTRU102 via the DL signaling channel 110 or does not transmit feedback that the WTRU102 would interpret as a NACK. When the node-B successfully decodes the data sent by the WTRU102, the node-B104 transmits an ACK message to the WTRU102 that releases the H-ARQ process, which may be designed to perform CC or IR, for other transmissions. The RNC106 controls the overall operation of data transmissions that occur between the node-B104 and the WTRU102, including radio resource allocation. The WTRU102 includes a data buffer 112 for storing E-DCH data, an optional data lifespan timer 114 for determining whether to discard expired data, and a retransmission timer 116 for determining whether data transmitted by the WTRU102 but not received by the node-B104 should be retransmitted, or whether H-ARQ transmissions should be terminated, or optionally restarted. The buffer 112, the lifespan timer 114, and the retransmission timer 116 are controlled by a controller 118, and the controller 118 sets (i.e., records) each transmission status for H-ARQ processes.

Fig. 2 is a flow diagram of a process 200 including method steps for controlling an H-ARQ process, which may be synchronous or asynchronous, in accordance with the present invention. In synchronous H-ARQ operation, the WTRU102 records the time at which an expected response to a data transmission between the WTRU102 and the node-B104 is expected, and the duration of a predetermined H-ARQ retransmission. In asynchronous H-ARQ operation, the WTRU102 transmits data and waits for feedback for a predetermined time.

After the WTRU102 initializes the H-ARQ process and the retransmission counter 116, the WTRU102 transmits data to the node-B104 during an active TTI via the E-DCH108 (step 202). The WTRU102 waits for feedback from the node-B104 in step 204, and if the WTRU102 receives an ACK message from the node-B104, the WTRU102 then sets the transmission status to "successful transmission", releases the H-ARQ process, and re-initializes the retransmission counter 116 for subsequent data transmissions (step 208).

If the WTRU102 receives a NACK message or does not receive any response in step 206, the WTRU102 determines whether the retransmission count indicated by the retransmission counter 116 is less than or equal to the maximum allowed retransmission (step 212).

If the retransmission count determined at step 212 is less than the maximum allowed retransmission, the WTRU102 sets or maintains the transmission status as "retransmission" and increments the retransmission counter 116 (step 214), the retransmission counter 116 being incremented each time the same data is retransmitted by the WTRU 102.

If the retransmission count determined in step 212 is equal to or greater than the maximum allowed retransmission, the H-ARQ process transmission is terminated and reconfigured to support subsequent data transmissions (step 213), optionally, the WTRU102 may set the transmission status to "restart transmission" and re-initialize the retransmission counter (step 216). After setting the transmission status to "restart transmission", the WTRU102 either initializes the H-ARQ transmission process to "new transmission", or the WTRU102 optionally releases the H-ARQ process (step 218).

Fig. 3 is a flow chart of a process 300 including steps of performing a CC method according to the present invention, the process 300 being performed on a TTI basis (step 302). In step 304, the WTRU102 determines whether EU physical resources have been allocated by the node-B104 and an H-ARQ process is available for the WTRU102 to transmit data to the node-B104 via the E-DCH 108. If EU physical resources have not been assigned, the WTRU102 waits for EU physical resource allocation and data transmission is delayed until the next TTI (step 302). If EU entity resources are already allocated and there are H-ARQ processes available, the WTRU102 determines whether the data is new (step 306). If the data is determined to be new data in step 306, the WTRU102 selects the highest priority data to transmit (step 308). In addition, the WTRU102 selects the MCS and TBS size that maximizes the highest priority data transmission within an allowed limit (step 310). The TBS size is selected based on the maximum MCS the node B104 sends, the TBS size, the available E-DCH108 transmission power, the MCS, and the data available for transmission in the buffer 112.

For each transport channel (TrCH), dedicated channel medium access control (MAC-d) flow, or logical channel, a list of allowed TBS sizes, retransmission limits, and allowed transmission latencies (i.e., MAC data "age limits") that are the maximum amount of the WTRU102 is allowed to transmit in the current physical resource allocation period transmission is determined, either by the RNC106 according to a radio resource control procedure or as specified by a standard. The selected MCS and TBS size may be explicitly signaled (preferably from the node, or obtained from an associated parameter such as a Channel Quality Indicator (CQI) which may indicate the maximum allowed WTRU interference or transmission power and/or a Transport Format Combination (TFC) index). the node-B104 may signal this in an initial channel assignment, or the node-B104 may send this information when the WTRU102 requests additional EU channel allocations.

The WTRU102 then generates at least one EU MAC (MAC-e) Protocol Data Unit (PDU) based on the selected TBS size and assigns an H-ARQ process for transmission of the MAC-e PDU at step 312. In step 314, the WTRU102 initializes the retransmission counter 116, increments an NDI and optionally sets the lifespan timer 114 in the WTRU 102. The NDI is used to indicate when new data is transmitted and when the node B needs to clear the soft buffer for the H-ARQ process being transmitted. The initial value of the retransmission counter 116 may be interpreted as a transmission of new data and the NDI parameter is not required in this example. The WTRU102 then initiates an EU transmission to the node-B to identify the current H-ARQ process, TBS size (if not assigned by the node-B104), and MCS. Since a particular H-ARQ process is operational, the H-ARQ process and MCS may be implicitly known by the node-B104 and therefore may not need to be sent by the WTRU102 to the node-B104.

The TBS size information is identified by the node B104 for each transmission and retransmission when a CC is supported, unless the TBS is identified by the node B104 at the time of physical channel allocation. In the CC example, the retransmission has the same MCS and TBS as used for the initial transmission.

Referring to step 306, if it is determined that the data is not new, a determination is made whether the WTRU102 uses the lifespan timer 114 (step 315). If the WTRU102 uses the lifespan timer 114, the process 300 proceeds to step 316 to determine if the lifespan timer 114 has expired. If the lifespan timer 114 has expired, the WTRU102 discards the data and releases the H-ARQ process (step 318), and the process 300 returns to step 302. Optionally, when the lifespan timer 114 nears expiration, the WTRU102 may use a more robust MCS to increase the reliability of successful transmissions.

The retransmission counter 116 in the WTRU102 is incremented each time data is unsuccessfully transmitted and therefore not acknowledged by the node-B104. If the lifespan timer 114 has not expired, or if the WTRU102 is not using the lifespan timer 114, the process 300 proceeds to step 320 to retransmit the data, whereby the WTRU102 determines whether the retransmission count is less than the maximum allowed retransmission. If the retransmission count is less than the maximum allowed retransmission, the transmission state is set or maintained at "retransmission", and the WTRU102 increments the retransmission counter 116 (step 322) and uses the same H-ARQ process, TBS, MCS, and NDI (if not integrated into the retransmission counter) (step 324). The WTRU102 then initiates an EU transmission to the node-B104 to identify the H-ARQ process (which may be implicitly known by the node-B and need not be sent to the node-B), TBS size (if not assigned by the node-B), and MCS in the associated physical control channel (step 330).

If the retransmission count reaches or exceeds the maximum allowed retransmission, the process 300 proceeds to step 318 to discard the data and release the H-ARQ process. Or if a decision to restart transmission is allowed in optional step 325, the transmission status is set to "restart transmission" and the WTRU102 initializes the retransmission counter 116, increments the NDI and assigns a new H-ARQ process (step 326). If the transmission data previously stored in the soft combining buffer is interrupted for subsequent retransmissions, it is preferable to flush the soft buffer and restart the H-ARQ transmission to increase the probability of successful transmission. Thus, when a maximum amount of retransmission for a particular H-ARQ process is reached, the NDI (or an initial retransmission count) is sent to indicate that the H-ARQ transmission has been restarted. When the node-B104 receives the incremental NDI (or transmission count is set to an initial value), the node-B104 clears the soft combining buffer of the previously received data.

In step 328, a new H-ARQ transmission using the same TBS is initialized, and optionally a more robust MCS may be selected for the "new transmission" to increase the probability of successful delivery (step 328). To allow for a change in MCS, the TBS may be segmented into several independent transmissions, in which case the transmission is reinitialized with more redundancy (whether by a change in MCS or using fewer bits), and the previous TBS may no longer fit the allocated physical resources, in which case the original transmission may be segmented into several separate transmissions that do not exceed the requirements. The WTRU102 then initiates an EU transmission to the node-B that identifies the current H-ARQ process (implicitly known by the node-B), TBS size and MCS (if not assigned by the node-B) for the physical control channel (step 330).

Fig. 4 is a flow chart of a process 400 including steps of performing an IR method according to the present invention, the process 400 being performed on a TTI basis (step 402). In step 404, the WTRU102 determines whether EU physical resources have been allocated by the node-B104 and whether an H-ARQ is available for the WTRU to transmit data to the node-B104 via the E-DCH108 (step 404). If EU physical resources have not been assigned, the WTRU102 waits for EU physical resource allocation and the data transmission is delayed until the next TTI (step 402). If EU entity resources are already allocated and there are H-ARQ processes available, the WTRU102 determines whether the data is new data (step 406). If the data is determined to be new data in step 406, the WTRU102 selects the highest priority data transmission (step 408). In addition, the WTRU102 selects the largest TBS size and the corresponding TFC maximizing transmission of the highest priority data using the most robust MCS allowed (step 410).

The WTRU102 then generates at least one MAC-e PDU based on the selected TBS size and assigns an H-ARQ process for transmission of the MAC-e PDU at step 412. In step 414, the WTRU102 initializes the retransmission counter 116, increments an NDI and optionally sets the lifespan timer 114 in the WTRU102 (step 414). The NDI is used to indicate when new data is transmitted and when the node B104 needs to empty the soft buffer for the transmitted H-ARQ process. The initial value of the retransmission counter 116 may be considered as the transmission of new data, in which case the NDI parameter is not required. The WTRU102 then initiates EU transmission to the node-B104 to identify the current H-ARQ process, TBS size, and MCS in the associated physical control channel (step 430). Since a particular H-ARQ process is operational, the H-ARQ process and MCS may be implicitly known by the node-B104 and, therefore, need not be sent by the WTRU102 to the node-B104.

Referring to step 406, if it is determined that the data is not new data, a determination is made whether the WTRU102 uses the lifespan timer 114 (step 415). If the WTRU102 uses the lifespan timer 114, the process 400 proceeds to step 416 to determine if the lifespan timer 114 has expired. If the lifespan timer 114 has expired, the WTRU102 discards the data and releases the H-ARQ process (step 418), and the process 400 returns to step 402. Optionally, when the lifespan timer 114 nears expiration, the WTRU102 may use a more robust MCS to increase the reliability of successful transmissions.

The retransmission counter 116 in the WTRU102 is incremented each time data is unsuccessfully transmitted and therefore not acknowledged by the node-B104. If the lifespan timer 114 has not expired, or if the WTRU102 is not using the lifespan timer 114, the process 400 proceeds to step 420 to retransmit the data, whereby the WTRU102 determines whether the retransmission count is less than the maximum allowed retransmission. If the retransmission count is less than the maximum allowed retransmission, the transmission state is set or maintained at "retransmission", the WTRU102 increments the retransmission counter 116 and selects a more robust MCS if allowed (step 422), and the WTRU102 uses the same H-ARQ process, TBS/TFC, and NDI in step 424.

In the IR, the MCS and TBS size decisions need to take into account the support of the most robust MCS, what the data needs to be, which is waiting for transmission in the WTRU102, and the available WTRU transmit power. At each retransmission, a more robust MCS may be selected for the same TBS. Initial transmission of a less robust MCS may allow for a larger TBS size, but this size is limited so that the same TBS may still be supported by a more robust MCS. Similarly, in terms of TBS determination, the WTRU's available EU transmit power must take into account the most robust MCS that can be allowed, even though the most robust MCS is not required for successful transmission.

If the retransmission count reaches or exceeds the maximum allowed retransmission, the process 400 proceeds to step 418 to discard the data and release the H-ARQ process. Or if a determination to restart transmission is allowed in step 425, the transmission status is set to "restart transmission" and the WTRU102 initializes the retransmission counter 116, increments the NDI and assigns a new H-ARQ process (step 426). In step 428, the same TBS/TFC is used and an MCS is selected.

Although the features and elements of the present invention are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements of the present invention.

While the invention has been described in terms of preferred embodiments, other variations which do not depart from the scope of the invention as claimed will become apparent to those skilled in the art.

Claims (10)

1. A wireless transmit/receive unit (WTRU), comprising:

at least one circuit configured to receive Radio Resource Control (RRC) configuration information from a wireless network; wherein the RRC configuration information indicates, for each dedicated channel medium access control (MAC-d) flow, a limit on a number of hybrid automatic repeat request (HARQ) retransmissions for each MAC-d flow;

wherein the at least one circuit is further configured to generate an enhanced dedicated channel medium access control (MAC-e) Protocol Data Unit (PDU), wherein the at least one circuit is further configured to transmit the MAC-e PDU using at least one of a plurality of synchronous HARQ processes; wherein each of the plurality of synchronous HARQ processes is configured to retransmit a MAC-e PDU that is not acknowledged without reaching the limit of the number of HARQ retransmissions for a MAC-d flow of the MAC-e PDU; and

wherein the at least one circuit is further configured to transmit an indication of a transport block size of the MAC-e PDU associated with the MAC-E PDU.

2. The WTRU of claim 1, wherein the RRC configuration information further indicates an allowed transport block size for use in generating the MAC-e PDU; and wherein the transport block size associated with the MAC-e PDU is an allowed transport block size.

3. The WTRU of claim 1, wherein the at least one circuit is further configured to initially transmit the MAC-e PDU with a variable set to zero, and increment the variable for at least one retransmission of the MAC-e PDU.

4. The WTRU of claim 1, wherein the at least one circuit is further configured to select enhanced uplink data for the MAC-e PDU to maximize transmission of highest priority data.

5. A method, the method comprising:

receiving, by a wireless transmit/receive unit, Radio Resource Control (RRC) configuration information from a wireless network; wherein the RRC configuration information indicates, for each dedicated channel medium access control (MAC-d) flow, a limit on a number of hybrid automatic repeat request (HARQ) retransmissions for each MAC-d flow;

generating an enhanced dedicated channel medium access control (MAC-e) Protocol Data Unit (PDU); and

transmitting the MAC-e PDU using at least one of a plurality of synchronous HARQ processes of the WTRU; wherein each of the plurality of synchronous HARQ processes retransmits a MAC-e PDU that has not been acknowledged without reaching the limit on the number of HARQ retransmissions for a MAC-d flow of the MAC-e PDU; wherein each MAC-e PDU is transmitted with an indication of a transport block size associated with the MAC-e PDU.

6. The method of claim 5, wherein the RRC configuration information further indicates an allowed transport block size for use in generating the MAC-e PDU; and wherein the transport block size associated with the MAC-e PDU is an allowed transport block size.

7. The method of claim 5, wherein a variable is set to zero for an initial transmission of the MAC-e PDU and the variable is incremented for at least one retransmission of the MAC-e PDU.

8. The method of claim 5, further comprising:

selecting enhanced uplink data for the MAC-e PDU to maximize transmission of highest priority data.

9. A node B, the node B comprising:

at least one circuit configured to transmit a signal comprising Radio Resource Control (RRC) configuration information to a wireless transmit/receive unit (WTRU); wherein the RRC configuration information indicates, for each dedicated channel medium access control (MAC-d) flow, a limit on a number of hybrid automatic repeat request (HARQ) retransmissions for each MAC-d flow;

wherein the at least one circuit is further configured to receive a MAC-e Protocol Data Unit (PDU) from the WTRU using at least one of a plurality of synchronous HARQ processes; and

wherein the at least one circuit is further configured to receive an indication of a transport block size of the MAC-e PDU associated with the MAC-E PDU.

10. The node-B of claim 9 wherein the at least one circuit is further configured to receive a variable transmitted from the WTRU to a MAC-e PDU that is set, the variable indicating an initial transmission with a zero value and incremented to a non-zero value for retransmission.