Method and device for controlling h-arq processing by adjusting data transmission parameters dynamically

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 to data between WTRU and node B. It relates to a method and an apparatus for assigning and releasing the processing of a hybrid-automatic repeat request (H-ARQ) used to control a transfer.

In 3rd generation cellular systems, adapted to incorporate into Enhanced Uplink (EU) operation designed to provide lower transmission delay times, higher throughput, and more efficient use of physical resources. 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. The 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 scheme is that the data received in the failed transmission can be soft-coupled to subsequent re-transmissions 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 in 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. Based on the response information received from node B, WTRU is enhanced uplink dedicated on the enhanced uplink (EU). Data is transmitted to node B and retransmitted 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 will send 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, "successful transmission" when an acknowledgment (ACK) message is received from node B, and 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 state is "new transmission", the first H-ARQ process is assigned. If the transmission state 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 transmission state is "transmission 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 WTRU 102 transmits data by the transmitter 120 through the E-DCH 108 and receives feedback from the node B 104 by the receiver 122 through the downlink (DL) signaling channel 110. If node B104 fails to decrypt the data transmitted by WTRU102, node B104 either sends a NACK message to WTRU102 via DL signaling channel 110 or does not send a response (which is interpreted as NACK by WTRU102). ). 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. The RNC 106 controls the overall operation of data transfer that occurs between node B104 and WTRU102, including the allocation of radio resources. The WTRU 102 is transmitted by a data buffer 112 for storing E-DCH data, an arbitrary data lifetime timer 114 used to determine if expired data needs to be discarded, and a WTRU 102. To determine if data that has not been received by node B104 should be retransmitted, H-ARQ transmission should be terminated, or optionally restarted. Includes the retransmission counter 116 used. The buffer 112, the lifetime timer 114, and the retransmission counter 116 are controlled by the controller 118. The 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 a process 200 including a 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 WTRU 102 tracks the course of what time the response to the data transmission between the WTRU 102 and the node B104 is expected, and the periodicity of the H-ARQ retransmission is predetermined. In the asynchronous H-ARQ operation, the WTRU 102 transmits data and waits for feedback for a predetermined time period.

After the WTRU 102 activates the H-ARQ processing and retransmission counter 116, the WTRU 102 transmits data to the node B 104 via the E-DCH 108 during the TTI at that time (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 state to "successful transmission", releases H-ARQ processing, and retransmits the retransmission counter 116 for subsequent data transmission. Invoke (step 208).

In step 206, if WTRU102 receives a NACK message or does not receive any response, WTRU102 determines whether the retransmission count indicated by the retransmission counter 116 is less than or equal to the maximum allowed number of retransmissions. Is determined (step 212).

In step 212, if the determined retransmission count is less than the maximum allowed retransmission count, WTRU 102 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 WTRU 102.

When 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 correspond to the subsequent data transmission (step 213). Optionally, the WTRU 102 may set the transmission state to "restarted transmission" and restart the retransmission counter (step 216). After setting the transmission state to "restart transmission", WTRU102 may restart the H-ARQ transmission process as "new transmission", or WTRU102 may optionally release the H-ARQ process (step 218). ).

FIG. 3 is a flow chart relating to a process 300 including a method step for carrying out CC according to the present invention. Process 300 is executed for each TTI (step 302). In step 304, WTRU102 determines whether EU physical resources are allocated by node B104 and whether 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 waits for EU physical resources to be allocated and data transmission is 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 it is determined in step 306 that the data is new, the WTRU 102 selects and transmits the highest priority data (step 308). In addition, 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 the E-DCH 108, 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 "lifespan" of the MAC data) is determined. The acceptable MCS and TBS sizes are the maximum that WTRU102 is allowed to transmit for the physical resource allocation period at that time. The configuration is either signaled from the RNC 106 according to the Radio Resource Control (RRC) procedure 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 may send this information when WTRU102 requests additional EU channel allocation.

The WTRU 102 then generates at least one EU MAC (MAC-e) Protocol Data Unit (PDU) based on the selected TBS size in step 312, and its MAC-e Allocate H-ARQ processing for PDU transmission. In step 314, the WTRU 102 initializes the retransmission counter 116, increases the NDI, and optionally sets the lifetime timer 114 in the WTRU 102. 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 invokes the current H-ARQ process, TBS size (if not assigned by node B104), and EU transmission identifying the MCS to node B104. The 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 transmission and retransmission to node B104, unless TBS is specified by node B104 in the 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 WTRU 102 uses the validity period timer 114 (step 315). If the WTRU 102 utilizes the validity period timer 114, process 300 proceeds to step 316 to determine if the validity period timer 114 has expired. If the validity period timer 114 has expired, the WTRU 102 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 WTRU 102 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 WTRU 102 is not using the validity period timer 114, process 300 proceeds to step 320 for data retransmission. Here, WTRU determines whether the retransmission count is less than the maximum number of permissible 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 WTRU 102 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 by H-ARQ processing (which can be implicitly known and may not need to be signaled to node B104), TBS size (node B104). (If not), and initiate EU transmission identifying the MCS on the associated physical control channel (step 330).

When the retransmission count becomes equal to or greater than the maximum number of allowable retransmissions, the 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 "transmission restart" and the WTRU 102 initializes the retransmission counter 116 and increases the NDI. , Allocate 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 transmit 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 transmit count set to the initial value), 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 the MCS, the TBS can be split into several independent transmissions. If the transmission was restarted with more redundancy (either due to MCS changes, or simply because of less puncture), the previous TBS may not fit the allocated physical resources. .. In this case, the original transmission can be split into a plurality of independent transmissions that do not exceed the requirements. The WTRU102 then tells node B the current H-ARQ process (which can be implicitly known as node B), the TBS size, and the MCS (assigned by node B) on the associated physical control channel. Invokes EU transmission to identify (if not) (step 330).

FIG. 4 is a flow chart of the process 400 including the method step of carrying out the IR according to the present invention. Process 400 is executed for each TTI (step 402). In step 404, WTRU102 determines whether EU physical resources are allocated by node B104 and whether 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 waits 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 it is determined in step 406 that the data is new, the WTRU 102 selects the highest priority data and transmits it (step 408). In addition, 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 WTRU 102 then generates at least one MAC-e PDU based on the selected TBS size in step 412 and its MAC-e Allocate H-ARQ processing for PDU transmission. In step 414, the WTRU 102 initializes the retransmission counter 116, increases the NDI, and optionally sets the lifetime timer 114 in the WTRU 102. 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 WTRU 102 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). The 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 WTRU 102 utilizes the validity period timer 114 (step 415). If the WTRU 102 utilizes the validity period timer 114, process 400 proceeds to step 416 to determine if the validity period timer 114 has expired. If the validity period timer 114 has expired, the WTRU 102 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 WTRU 102 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 WTRU 102 is not using the validity period timer 114, process 400 proceeds to step 420 for data retransmission, and WTRU 102 allows retransmission counts. 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 WTRU 102 increments the retransmission counter 116 and is acceptable. If so, select a more robust MCS (step 422). In step 424, WTRU102 uses the same H-ARQ treatment, TBS / TFC, and NDI.

With respect to IR, when determining the MCS and TBS size, it must correspond to 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. The first transmission on a less robust MCS allows for a larger TBS size, but this size is limited to the size that the most robust MCS can accommodate for that same TBS. Also, to determine the TBS, the transmit power to the EU available by WTRU is the most robust allowed, 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 "transmission restart" and the WTRU 102 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