Method and apparatus for dynamically adjusting data transmission parameters and controlling h-arq processes

The present invention relates to a wireless communication system including a wireless transmit / receive unit (WTRU) and node B. More specifically, it dynamically adjusts data transmission parameters such as Modulation and Coding Scheme (MCS) and Transport Block Set (TBS) size, and between WTRU and node B. It relates to a method and an apparatus for assigning and releasing a hybrid-automatic repeat request (H-ARQ) process used to control data transfer.

Adapted to incorporate Enhanced Uplink (EU) operations designed to provide lower transmission delay times, higher throughput, and more efficient use of physical resources in 3rd generation cellular systems. Adaptive Modulation and Coding (AM & C) and H-ARQ methods are being studied.

The AM & C method allows the MCS to be dynamically adjusted for each Transmit Time Interval (TTI), using radio resources most efficiently for each TTI and as high as possible. MCS is selected to provide the data rate.

<p num="0004"> A less robust MCS uses less physical resources but is vulnerable to error. Robust MCS uses more physical resources but provides stronger protection against errors.</p><p num="0005"> The H-ARQ method is used to generate transmission and retransmission with low delay. The first aspect of the H-ARQ method is that the data received in the failed transmission can be soft-coupled to subsequent retransmissions to increase the probability of successful reception. Either Chase Combining (CC) or Incremental Redundancy (IR) can be applied. When CC is applied, the same MCS is selected for retransmissions. When IR is applied, a more robust MCS is used for each retransmission.</p>

<p num="0006"> The present invention is implemented in a wireless communication system including a WTRU that transfers data to node B. Data transmission parameters such as TBS size are dynamically adjusted for each TTI. Optionally, the MCS can also be adjusted. If necessary, the H-ARQ process used to control the data transfer between WTRU and Node B is assigned and released. The response information received from node B allows the WTRU to be an Enhanced uplink Dedicated channel for the Enhanced Uplink (EU). Send data to node B and resend it through CHannel: E-DCH). The WTRU queues the data to be transmitted and determines the data transmission state. The transmission state is set to one of "new transmission", "successful transmission", "retransmission", and "restart transmission" by the control device in WTRU. For each TTI, the WTRU sends the EU to node B, which explicitly or implicitly identifies the retransmission number, new data display, assigned H-ARQ processing, TBS size, and optional MCS. To start.</p><p num="0007"> The transmission status is set to "new transmission" when the data is new data, to "successful transmission" when an acknowledgment (ACK) message is received from node B, and to transmission of new data by the control device in WTRU. Correspondingly, if a negative response (NACK) message is received or no response from node B, it will be "retransmitted", and if the retransmission count exceeds the predetermined maximum number of retransmissions, it will be optionally "retransmitted". It is set to "Restart transmission" respectively.</p><p num="0008"> If the transmission status is "new transmission", the first H-ARQ process is assigned. If the transmission status is "retransmission", the retransmission count is increased and the same H-ARQ processing is assigned. If the transmission is "successful transmission", the H-ARQ process is released. Optionally, if the transmit state is "send restart", the retransmission count is initialized, the new data indicator (NDI) is incremented, and H-ARQ processing is assigned.</p><p num="0009"> The present invention can be understood in more detail from the following description of preferred embodiments, provided as an example and to be understood with the accompanying drawings. </p>

<p num="0010"> As described above, according to the present invention, in a wireless communication system including a wireless transmission / reception unit that transfers data to node B, data transmission parameters such as a modulation and coding method and a transport block group size are set for each transmission time interval. A system is provided in which the hybrid automatic repeat request processing, which is dynamically adjusted and used for data transfer control between WTRU and node B, is started and released as needed.</p>

<figref num="1">It is a block diagram of the wireless communication system which operates according to this invention.</figref><figref num="2">It is a flow diagram of the process which starts and releases the H-ARQ process according to this invention.</figref><figref num="3">FIG. 5 is a flow chart of a process including a method step of carrying out CC according to the present invention.</figref><figref num="4">FIG. 5 is a flow chart of a process including a method step of performing IR according to the present invention.</figref>

Hereinafter, the term "WTRU" is used, but not limited to, a user equipment (UE), a mobile terminal, a fixed or mobile subscriber unit, a pager, or any other capable of operating in a wireless environment. Also includes types of equipment. The term "node B" includes, but is not limited to, base stations, site controllers, access points, or any other type of interface device in a wireless environment, as referred to thereafter.

Features of the invention can be incorporated into integrated circuits (ICs) or configured in circuits with a large number of interconnected components.

FIG. 1 is a block diagram of a wireless communication system 100 that operates according to the present invention. System 100 includes WTRU102, node B104, and a radio network controller (Radio Network). Controller: RNC) 106 is provided. Based on the activated H-ARQ, the WTRU102 transmits data through the transmitter 120 through the E-DCH108 and receives feedback from the node B104 through the downlink (DL) signaling channel 110 through the receiver 122. If node B104 fails to decrypt the data sent by WTRU102, node B104 either sends a NACK message to WTRU102 over DL signaling channel 110 or does not send a response (which is interpreted by WTRU102 as NACK). ). When node B104 succeeds in decoding the data transmitted by WTRU102, node B104 sends an ACK message to WTRU102 and releases the H-ARQ process for other transmissions. The H-ARQ process can be designed to perform either CC or IR. RNC106 controls the overall operation of data transfer between nodes B104 and WTRU102, including the allocation of radio resources. The WTRU102 is transmitted by a data buffer 112 to store E-DCH data, any data lifetime timer 114 used to determine if expired data should be discarded, and the WTRU102. To determine if data that has not been received by node B104 should be retransmitted, H-ARQ transmission should be terminated, or optionally restarted. Contains the retransmission counter 116 used. The buffer 112, the lifetime timer 114, and the retransmission counter 116 are controlled by the controller 118. Controller 118 sets the state of each transmission associated with the H-ARQ process (ie, records the progress).

FIG. 2 is a flow chart of the process 200 including the method step of controlling the H-ARQ process according to the present invention. The H-ARQ process may be synchronous or asynchronous. In the synchronous H-ARQ operation, the WTRU102 tracks the course of what time the response to the data transmission between the WTRU102 and the node B104 is expected, and the periodicity of the H-ARQ retransmission is predetermined. In asynchronous H-ARQ operation, the WTRU102 sends data and waits for feedback for a predetermined time period.

After the WTRU102 activates the H-ARQ processing and retransmission counter 116, the WTRU102 sends data to node B104 via E-DCH108 during the current TTI (step 202). In step 204, WTRU102 waits for feedback from node B104. When WTRU102 receives an ACK message from node B104, WTRU102 sets the transmission status to "successful transmission", releases H-ARQ processing, and retransmits the retransmission counter 116 for subsequent data transmission. Invoke (step 208).

In step 206, if the WTRU102 receives a NACK message or no response, the WTRU102 determines whether the retransmission count indicated by the retransmission counter 116 is less than or equal to the maximum allowed retransmissions. Is determined (step 212).

In step 212, if the determined retransmission count is less than the maximum allowed retransmission count, WTRU102 sets or maintains the transmit state to "retransmit" and increments the retransmission counter 116 (step 214). The retransmission counter 116 is incremented each time the same data is retransmitted by WTRU102.

If the retransmission count determined in step 212 is equal to or greater than the maximum allowable number of retransmissions, the transmission of the H-ARQ process is terminated and reset to support subsequent data transmission (step 213). Optionally, the WTRU102 may set the transmission state to "restarted transmission" and restart the retransmission counter (step 216). After setting the transmission state to "restart transmission", the WTRU102 may restart the H-ARQ transmission process as "new transmission", or the WTRU102 may optionally release the H-ARQ process (step 218). ).

FIG. 3 is a flow chart relating to process 300 including method steps for carrying out CC according to the present invention. Process 300 is executed for each TTI (step 302). In step 304, WTRU102 determines if EU physical resources are allocated by node B104 and if WTRU102 can use H-ARQ processing to send data to node B104 via E-DCH108. To do. If EU physical resources are not allocated, WTRU102 will wait for EU physical resources to be allocated and data transmission will be delayed until the next TTI (step 302). If EU physical resources are allocated and H-ARQ processing is available, WTRU102 determines if the data is new data (step 306). If the data is determined to be new data in step 306, WTRU102 selects the highest priority data and transmits it (step 308). In addition, the WTRU102 selects the MCS and TBS sizes that maximize the transmission of top priority data within the permissible limits (step 310). The TBS size is selected based on the maximum MCS and TBS size signaled by node B104, the transmit power available for E-DCH108, the MCS, and the data available for transmission in buffer 112.

For each Transport CHannel (TrCH), a dedicated channel Medium Access Control (MAC-d) flow or logical channel, a list of allowed TBS sizes, retransmission limits, and allowed The transmission delay (ie, the "life span" of the MAC data) is determined. The acceptable MCS and TBS sizes are the maximum that the WTRU102 is allowed to send for the current physical resource allocation period. The configuration is either signaled from RNC106 according to Radio Resource Control (RRC) procedures or uniquely specified by the standard. The selected MCS and TBS size can be explicitly signaled (preferably from node B) or channel quality indicator (CQI) and / or TFC (Transport Format). Combination) Either that can be derived from related parameters such as indicators. The CQI can represent the maximum interference or transmit power allowed for the WTRU. Node B104 can signal this information in the first channel allocation. Alternatively, node B104 can send this information when WTRU102 requests additional EU channel allocation.

The WTRU102 then generates at least one EU MAC (MAC-e) Protocol Data Unit (PDU) based on the selected TBS size in step 312, and that MAC-e Allocate H-ARQ processing for sending PDUs. In step 314, the WTRU102 initializes the retransmission counter 116, increases the NDI, and optionally sets the lifetime timer 114 in the WTRU102. NDI is used to indicate when new data is being sent and when node B104 needs to clear the soft buffer associated with the H-ARQ process being sent. The initial value of the retransmission counter 116 may be interpreted as the transmission of new data, in which case the NDI parameter is not needed. The WTRU102 then invokes an EU transmission to node B104 that identifies the current H-ARQ process, TBS size (if node B104 is not assigned), and MCS. H-ARQ processing and MCS can be implicitly known by node B104 by the specified H-ARQ processing operation and therefore may not need to be signaled to node B104 by WTRU102.

If CC is supported, TBS size information is specified for each transmit and retransmission to node B104 unless TBS is specified by node B104 in physical channel allocation. In the case of CC, the retransmission has the same MCS and TBS as applied in the first transmission.

Returning to step 306, if it is determined that the data is not new data, it is determined whether the WTRU102 utilizes the lifetime timer 114 (step 315). If the WTRU102 uses the lifetime timer 114, process 300 proceeds to step 316 to determine if the lifetime timer 114 has expired. If the lifetime timer 114 has expired, the WTRU102 discards the data, releases (releases) the H-ARQ process (step 318), and process 300 returns to step 302. When the lifetime timer 114 is nearing expiration, the WTRU102 can optionally use a more robust MCS to increase the probability of successful transmission.

The retransmission counter 116 in WTRU102 is incremented each time the data transmission is unsuccessful and therefore does not receive an acknowledgment from node B104. If the validity period timer 114 has not yet expired, or if the WTRU102 is not utilizing the validity period timer 114, process 300 proceeds to step 320 for data retransmission. Here, the WTRU determines if the retransmission count is less than the maximum number of allowed retransmissions. If the retransmission count is less than the maximum number of allowed retransmissions, the transmit state is set as "retransmit" or "retransmit" is maintained and the WTRU102 increments the retransmission counter 116 (step 322). ), And use the same H-ARQ processing, TBS, MCS, and NDI (if not combined with the retransmission counter) (step 324). WTRU102 is then assigned to node B104 with H-ARQ processing (which can be implicitly known and may not need to be signaled to node B104), TBS size (assigned by node B104). Invokes EU transmission to identify the MCS on the associated physical control channel (if not) (step 330).

If the retransmission count is greater than or equal to the maximum number of allowed retransmissions, process 300 proceeds to step 318, discards the data, and releases the H-ARQ process. Alternatively, if it is determined in optional step 325 that the restarted transmission is allowed, the transmission state is set to "send restart" and the WTRU102 initializes the retransmission counter 116 and increases the NDI. , Assign a new H-ARQ process (step 326). If previously transmitted data stored in the soft-join buffer disrupts subsequent retransmissions, clear the soft buffer and send the H-ARQ to increase the probability of successful transmission. It is better to restart. Therefore, when the maximum number of retransmissions is reached for a particular H-ARQ process, an NDI (or initialized retransmission count) is sent and the H-ARQ transmission is restarted. Shown. When node B104 receives the increased NDI (or the default send count), node B104 clears the previously received data from the soft join buffer.

In step 328, a new H-ARQ transmission is invoked using the same TBS, and optionally a more robust MCS for the "new transmission" can be selected to increase the probability of successful delivery ( Step 328). To allow this change in MCS, TBS can be split into several independent transmissions. The previous TBS may not fit the allocated physical resources if the transmission is restarted with more redundancy (either due to MCS changes, or simply because of less puncture). .. In this case, the original transmission can be split into a plurality of independent transmissions that do not exceed the requirements. WTRU102 then tells node B the current H-ARQ process (which can be implicitly known as node B), the TBS size, and the MCS in the associated physical control channel (assigned by node B). Invoke EU transmission to identify (if not) (step 330).

FIG. 4 is a flow chart of process 400 including a method step of performing IR according to the present invention. Process 400 is executed for each TTI (step 402). In step 404, WTRU102 determines if EU physical resources are allocated by node B104 and if WTRU102 can use H-ARQ processing to send data to node B104 via E-DCH108. To do. If no EU physical resources have been allocated, the WTRU102 will wait for EU physical resources to be allocated and data transmission will be delayed until the next TTI (step 402). If EU physical resources are allocated and H-ARQ processing is available, WTRU102 determines if the data is new data (step 406). If the data is determined to be new data in step 406, WTRU102 selects the highest priority data and sends it (step 408). In addition, the WTRU102 selects the maximum TBS size and the corresponding TFC that maximizes the transmission of top 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 in step 412 and that MAC-e Allocate H-ARQ processing for sending PDUs. In step 414, the WTRU102 initializes the retransmission counter 116, increases the NDI, and optionally sets the lifetime timer 114 in the WTRU102. NDI is used to indicate when new data is being sent and when node B104 needs to clear the soft buffer associated with the H-ARQ process being sent. The initial value of the retransmission counter 116 may be interpreted as the transmission of new data, in which case the NDI parameter is not required. The WTRU102 then initiates an EU transmission to node B104 that identifies the current H-ARQ process, TBS size, and MCS on the associated physical control channel (step 430). H-ARQ processing and MCS can be implicitly known by node B104 by the specified H-ARQ processing operation. Therefore, it may not be necessary for WTRU102 to signal node B104.

Returning to step 406, if it is determined that the data is not new data, it is determined whether the WTRU102 utilizes the lifetime timer 114 (step 415). If the WTRU102 uses the lifetime timer 114, process 400 proceeds to step 416 to determine if the lifetime timer 114 has expired. If the lifetime timer 114 has expired, the WTRU102 discards the data, releases (releases) the H-ARQ process (step 418), and process 400 returns to step 402. When the lifetime timer 114 is near expiration, the WTRU102 can optionally use a more robust MCS to increase the probability of successful transmission.

The retransmission counter 116 in WTRU102 is incremented each time the data transmission is unsuccessful and therefore does not receive an acknowledgment from node B104. If the lifetime timer 114 has not expired, or if the WTRU102 is not utilizing the lifetime timer 114, process 400 proceeds to step 420 to retransmit the data, and the WTRU102 allows the retransmission count. Determine if it is less than the maximum number of retransmissions. If the retransmission count is less than the maximum number of allowed retransmissions, the transmit state is set as "retransmit" or "retransmit" is maintained and the WTRU102 increments the retransmission counter 116 and is acceptable. If so, choose a more robust MCS (step 422). In step 424, WTRU102 uses the same H-ARQ processing, TBS / TFC, and NDI.

For IR, when determining MCS and TBS sizes, support the most robust MCS, the conditions required by the data ready for transmission in WTRU102, and the transmit power available to WTRU. Take three points into account. For each retransmission, a more robust MCS can be chosen for the same TBS. Initial transmissions on less robust MCSs allow for larger TBS sizes, but this size is limited to the size that the most robust MCSs can accommodate for that same TBS. Also, to determine TBS, the transmit power to the EU available to WTRU is the most robust tolerated, even though the most robust MCS may not be required for successful transmission. MCS must be considered.

If the retransmission count is greater than or equal to the maximum number of allowed retransmissions, process 400 proceeds to step 418, discards the data, and releases the H-ARQ process. Alternatively, if it is determined in optional step 425 that the restarted transmission is allowed, the transmission state is set to "send restart" and the WTRU102 initializes the retransmission counter 116 and increases the NDI. And assign a new H-ARQ process (step 426). In step 428, the same TBS / TFC is used and the MCS is selected.

The functions and elements of the present invention have been described in a particular combination in preferred embodiments. Each function or element can be used alone without the other functions and elements of the preferred embodiment, or in various combinations with or without the other functions and elements of the invention.

The present invention has been described with preferred embodiments. It will also be apparent to those skilled in the art that other modifications within the scope of the invention, as outlined in the claims, are possible.

The present invention can be used in a wireless communication system including a wireless transmission / reception unit and node B.

100 wireless communication system 102 WTRU 104 node B 106 RNC 118 Control unit 120 transmitter 122 receiver