AU2006332854B2

AU2006332854B2 - Method and system for implementing H-ARQ-assisted ARQ operation

Info

Publication number: AU2006332854B2
Application number: AU2006332854A
Authority: AU
Inventors: Arty Chandra; Stephen E. Terry
Original assignee: InterDigital Technology Corp
Current assignee: InterDigital Technology Corp
Priority date: 2005-12-29
Filing date: 2006-12-27
Publication date: 2011-12-08
Anticipated expiration: 2026-12-27
Also published as: KR20080083714A; WO2007079085A2; EP1974492A2; IL192504A0; WO2007079085A3; KR20080080234A; JP2009522873A; TW200729815A; RU2008131049A; SG158087A1; CA2635762A1; CN101814982A; AU2006332854A1; BRPI0621173A2; TW201018130A; SG154450A1; AR058883A1

Abstract

A method and system for implementing hybrid automatic repeat request (H-ARQ)-assisted automatic repeat request (ARQ) in a wireless communication system are disclosed. When an H-ARQ negative acknowledgement (NACK)-to-positive acknowledgement (ACK) error occurs, the H-ARQ receiver sends an H-ARQ NACK-to-ACK error indicator to the H-ARQ transmitter unless a maximum retransmission limit has reached, a maximum time for delivery has expired or a lifespan of the failed packet has expired. The H-ARQ transmitter sends a local NACK to the ARQ transmitter so that the failed packet is recovered at an ARQ level. The H-ARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet before certain conditions occur. The ARQ receiver may send a status report to the ARQ transmitter for recovery of the failed packet.

Description

WO 2007/079085 PCT/US2006/049306 Express Mail Label No. EV748349925US [0001] METHOD AND SYSTEM FOR IMPLEMENTING H-ARQ-ASSISTED ARQ OPERATION [0002] FIELD OF INVENTION [0003] The present invention is related to wireless communication systems. More particularly, the present invention is related to a method and system for implementing hybrid automatic repeat request (H-ARQ)-assisted automatic repeat request (ARQ) in a wireless communication system. [0004] BACKGROUND [0005] In conventional wireless communication systems, such as wideband code division multiple access (WCDMA) Release 5/6, high speed data transmission isachieved by high speed downlink packet access (HSDPA) and high speed uplink packet access (HSUPA) technologies. To improve reliability of data transmission, H-ARQ and ARQ are implemented. [0006] Figure 1 shows a conventional wireless communication system 100. The system 100 includes a user equipment (UE) 110, a Node-B 120 and a radio network controller (RNC) 130. H-ARQ entities are located in a medium access control (MAC) layer 112 of the UE 110 and a MAC layer 122 of the Node-B 120. Packets are assigned transmission sequence numbers (TSNs) in an H-ARQ transmitter. An H-ARQ receiver receives the packets and attempts to decode the transmitted packets. If a packet is not decodable, the H-ARQ receiver sends a negative acknowledgment (NACK) back to the H-ARQ transmitter for retransmission of the failed packet. If a packet is correctly decoded, the H-ARQ receiver sends a positive acknowledgment (ACK) for the packet to the H-ARQ transmitter. Upon receiving a NACK, the H-ARQ transmitter retransmits the packet if the number of retransmissions of the failed packet is less than a predetermined maximum limit, and the allowed transmission time for the failed packet has not expired. Otherwise, the failed packet is discarded and recovered at an ARQ level. -1- WO 2007/079085 PCT/US2006/049306 [00071 ARQ entities are located in a radio link control (RLC) layer 114 of the UE 110 and an RLC layer 132 of the RNC 130. The ARQ entities handle the retransmission of the failed packet. The ARQ entities recover packets that are lost due to an NACK-to-ACK misinterpretation error at the H-ARQ level. The ARQ process in an RLC layer is quite complex with many options to perform status reporting. [00081 An H-ARQ assisted ARQ operation may be considered when both the H-ARQ and ARQ functions are co-located, such as in a universal mobile telecommunication systems (UMTS) Node-B or a long term evolution (LTE) evolved Node-B (eNode-B). (00091 Figure 2 shows an example of an H-ARQ-assisted ARQ operation proposed for third generation partnership project (3GPP) standards. A transmitter 250 includes an ARQ transmitter 252 and an H-ARQ transmitter 254. A receiver 260 includes an ARQ receiver 262 and an E-ARQ receiver 264. The H-ARQ transmitter 254 provides a local ACK or a local NACK to the ARQ transmitter 252. [0010] As shown in Figure 2, a local NACK is generated when the H ARQ transmitter 254 fails the H-ARQ transmission, (e.g., due to maximum retransmission limit). The ARQ transmitter 252 sends an ARQ protocol data unit (PDU) x to the H-ARQ transmitter 254 (step 202). The H-ARQ transmitter 254 sends the ARQ PDU x to the H-ARQ receiver 264 (step 204). The ARQ PDU x is not decodable and the H-ARQ receiver 264 sends a NACK to the H-ARQ transmitter 254 (step 206). The H-ARQ transmitter 254 retransmits the ARQ PDU x to the H-ARQ receiver 264 (step 208). The ARQ PDU x is still not decodable and the H-ARQ receiver 264 sends another NACK to the H-ARQ transmitter 254 (step 210). At such a point, it is determined that the number of retransmissions for the ARQ PDU x reaches a maximum retransmission limit (step 212). The H-ARQ transmitter 254 then sends a local NACK for the ARQ PDU x to the ARQ transmitter 252 (step 214). [00111 A local NACK may also be generated when an NACK-to-ACK error is reported from the H-ARQ receiver 264 to the H-ARQ transmitter 254. Still referring to Figure 2, the ARQ transmitter 252 sends an ARQ PDU y to -2- WO 2007/079085 PCT/US2006/049306 the H-ARQ transmitter 254 (step 216). The H-ARQ transmitter 254 transmits the ARQ PDU y to the H-ARQ receiver 264 (step 218). The ARQ PDU y is not decodable and the H-ARQ receiver 264 sends a NACK to the H-ARQ transmitter 254 (step 220). However, the NACK is misinterpreted as an ACK by the H-ARQ transmitter 254 and the H-ARQ transmitter 254 treats the ARQ PCU y as successfully transmitted. The H-ARQ receiver 264 detects an NACK-to-ACK error, (e.g., when the H-ARQ receiver 264 receives a new PDU via the same H-ARQ process while waiting for retransmission of the ARQ PDU y), (step 222). The H-ARQ receiver 264 sends a NACK-to-ACK error indicator to the H-ARQ transmitter 254 (step 224). Upon receipt of the NACK-to-ACK error indicator, the H-ARQ transmitter 254 sends a local NACK to the ARQ transmitter 252 and the ARQ PDU y is recovered at an ARQ level (step 226). [00121 As shown in Figure 2, a local ACK is generated when none of the above two events for an ARQ packet occurs during a predefined time interval. The ARQ transmitter 252 sends an ARQ PDU z to the H-ARQ transmitter 254 (step 228). The H-ARQ transmitter 254 transmits the ARQ PDU z to the H ARQ receiver 364 (step 230). The ARQ PDU z is successfully decoded and the H-ARQ receiver 264 sends the ARQ PDU z to the ARQ receiver 262 (step 232), and sends an ACK to the H-ARQ transmitter 254 (step 234). When it is determined that a NACK-to-ACK error is not reported during a predetermined time interval (step 236), the H-ARQ transmitter 254 sends a local ACK to the ARQ transmitter 252 (step 238). The ARQ transmitter 252 will discard the packet from a transmit buffer after receiving the local ACK from the H-ARQ transmitter 254. [0013] In the above example of an H-ARQ assisted ARQ system, a complex layer 2 (L2) status reporting mechanism is removed under the assumption that the NACK-to-ACK error is the only significant source of undetected packet loss. The ARQ transmitter will not be able to recover the packet for cases where the NACK-to-ACK error indicator is lost or a shared channel is lost due to a discontinuous transmission (DTX)/ACK error. Thus lossless transmission cannot be guaranteed. -3- 4 Current downlink. H-ARQ, (Release 5), does not specify the maximum number of retransmissions for a packet. Thus, the H-ARQ transmitter or receiver does not know the maximum number of transmissions for each packet. There is an assumption that the ARQ transmitter and the HARQ transmitter have the same 5 PDU size. The H-ARQ transmitter informs the ARO transmitter the segment that is lost, (not the ARQ PDU). If the ARQ PDU is retransmitted, the H-ARQ transmitter will retransmit the complete packet, not only the missing segment. It is also unclear how to recover the last packet of the H-ARQ transmission. SUMMARY 10 The present invention is related to a method and system for implementing H-ARQ-assisted ARQ in a wireless communication system. An H-ARQ receiver determines whether an H-ARQ NACK-to-ACK error occurs. When an H-ARQ NACK-to-ACK error occurs, the H-ARQ receiver sends an HARO error indicator to the H-ARQ transmitter unless the number of retransmissions of the failed 15 packet has reached a maximum retransmission limit, a maximum time for delivery of the failed packet has expired and/or a lifespan of the failed packet has expired. The H-ARQ transmitter tries to recover the failed packet. The H-ARQ transmitter sends a local NACK to the ARQ transmitter if the maximum retransmission limit has been reached, the maximum delivery time has expired or the lifespan of the 20 failed packet has expired, so that the failed packet can be recovered at an ARO level. The HARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet before certain conditions occur. Based on reception of the local NAK, the ARQ receiver may send a status report to the ARQ transmitter for recovery of the failed packet. 25 In one aspect, the present invention provides a method for implementing hybrid automatic repeat request (H-ARQ)-assisted automatic repeat request (ARQ), the method comprising: determining that an H-ARQ negative acknowledgement (NACK)-to-positive acknowledgement (ACK) error has occurred with respect to a failed packet, 30 wherein more than one packet is transmitted simultaneously and the H-ARQ NACK-to-ACK error indicator indicates H-ARQ NACK-to-ACK errors of more than one packet; 4a determining whether or not to transmit an H-ARQ NACK-to-ACK error indicator, wherein the H-ARQ NACK-to-ACK error indicator is not transmitted on a condition that any of the number of retransmissions of the failed packet has reached a maximum retransmission limit, a maximum time for delivery of the 5 failed packet has expired, or a lifespan of the failed packet has expired; and determining whether or not to transmit a local NACK. In another aspect, the present invention provides a hybrid automatic repeat request (H-ARQ) receiver for implementing an H-ARO-assisted automatic repeat request (ARO), the receiver being configured to: 10 determine that an H-ARQ negative acknowledgement (NACK)-to-positive acknowledgement (ACK) error has occurred with respect to a failed packet, wherein more than one packet is transmitted simultaneously and the H-ARQ NACK-to-ACK error indicator indicates H-ARQ NACK-to-ACK errors of more than one packet; 15 determine whether or not to transmit an H-ARQ NACK-to-ACK error indicator, wherein the H-ARQ NACK-to-ACK error indicator is not transmitted on a condition that any of the number of retransmissions of the failed packet has reached a maximum retransmission limit, a maximum time for delivery of the failed packet has expired, or a lifespan of the failed packet has expired; and 20 determining whether or not to transmit a local NACK. BRIEF DESCRIPTION OF THE DRAWINGS A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example WO 2007/079085 PCT/US2006/049306 and to be understood in conjunction with the accompanying drawing(s) wherein: [0019] Figure 1 shows a conventional wireless communication system; [00201 Figure 2 shows an example of an H-ARQ-assisted ARQ operation proposed for third generation partnership project (3GPP) standards; and [00211 Figure 3 is a signaling diagram of a process for implementing an H-ARQ-assisted ARQ operation in accordance with the present invention. [0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0023] The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components. [0024] Figure 3 is a signaling diagram of a process 400 for implementing an H-ARQ-assisted ARQ operation in a wireless communication system 300 in accordance with the present invention. The system 300 includes a transmitter 310 and a receiver 320. The transmitter 310 includes an ARQ transmitter 312 and an H-ARQ transmitter 314. The receiver 320 includes an ARQ receiver 322 and an H-ARQ receiver 324. [00251 In order to support the H-ARQ-assisted ARQ in accordance with the present invention, the following parameters are defined: e TErrorIndicator: H-ARQ error indication timer is defined as the amount of time that an H-ARQ receiver should wait for a retransmission of the failed packet before sending an HARQ error indicator. It is preferable to keep the H-ARQ error indication timer constant for the whole system for simple implementation. However, the H-ARQ error indication timer may be adjusted based on the quality of service (QoS) requirements. For example, the length of the H-ARQ error indication timer may be linked to the scheduling priority. * Naetransmissio: Maximum number of retransmissions allowed for a packet. The maximum number of retransmissions may be based on the QoS requirements, and be configured per service type. -5- WO 2007/079085 PCT/US2006/049306 * Teiivery: Maximum delivery time allowed for successful delivery of the packet after the first transmission. The maximum delivery time may be based on the QoS requirements, (e.g., a block error rate, latency, or the like), and be configured per service type. * TRecoverysyne: For synchronous H-ARQ, a time within which the H ARQ receiver expects to receive a failed packet after transmitting an H-ARQ error indicator. * TiecoveryAsyne: For asynchronous H-ARQ, a time within which the H-ARQ receiver expects to receive a failed packet after transmitting an H ARQ error indicator. The timer may be associated with the QoS requirements, and be configured per service type. For example, the length of the timer may be linked to the scheduling priority. e WHA.RQ: A window, (i.e., the number of packets), within which a failed packet should be received. If the failed packet is not received within WHARQ, it is assumed lost. [0026] The transmitter 310 and the receiver 320 may also be given with a parameter for a lifespan of a packet, (i.e., the maximum time to transmit the packet). The parameters may be provided by a central node to the H-ARQ receiver 324 and the H-ARQ transmitter 314. If the parameters are defined per service type, the parameters may be given to the H-ARQ receiver 324 and the H-ARQ transmitter 314 at the start of that service. [0027] The maximum number of retransmissions and/or the lifespan of a packet may be dynamically changed depending on the QoS requirements. The maximum number of transmissions may be indicated by either explicitly identifying the number of transmissions in the associated signaling or identifying a MAC flow that is associated with a configured maximum number of transmissions. In accordance with the first option, the number of retransmissions per packet is indicated in the associated control signaling for the first transmission. In accordance with the second option, each MAC flow may be associated with a certain number of retransmissions and by identifying the MAC flow in the associated control signaling for the first transmission, the maximum number of transmissions may be indicated. If the -6- WO 2007/079085 PCT/US2006/049306 second option is used, the identified MAC flow is translated to the maximum number of transmisisons configured by the receiver. The maximum number of retransmissions may also be known by an H-ARQ process ID if specific H-ARQ processes are dedicated to a MAC flow for a set of MAC flows. Alternatively, a flag may be set in the associated signaling to indicate last transmission. [00281 A process 400 for implementing an H-ARQ-assisted ARQ operation in accordance with the present invention is explained hereafter with reference to Figure 3. The H-ARQ transmitter 314 transmits a packet to the H-ARQ receiver 324 (step 402). If the packet is successfully received, the H ARQ receiver 324 sends the packet to the ARQ receiver 322 (not shown in Figure 3). If the packet is not successfully received, the H-ARQ receiver 324 sends a NACK to the H-ARQ transmitter 314 (step 404). After sending the NACK in step 404, the H-ARQ receiver 324 determines whether an H-ARQ NACK-to-ACK error occurs (step 406). Upon detection of the H-ARQ NACK to-ACK error, the H-ARQ receiver 324 generates, and sends, an H-ARQ NACK-to-ACK error indicator to the H-ARQ transmitter 314 (step 408). [00291 For synchronous H-ARQ transmission, the time of a H-ARQ retransmission is known to the receiver. If the H-ARQ receiver 324 receives a new packet when expecting retransmission of the failed packet, the H-ARQ receiver 324 determines that an H-ARQ NACK-to-ACK error occurs and sends an H-ARQ NACK-to-ACK error indicator unless the failed packet has been transmitted for the maximum number of retransmissions. [00301 For asynchronous H-ARQ transmission, a timer TErrornicator is set at the H-ARQ receiver 324 when the maximum number of retransmission has not been reached and the H-ARQ receiver 324 sends a NACK to the H-ARQ transmitter 314 at step 404. If the failed packet is successfully received before the timer TErrorIndicator expires, the timer TErrorindicator is reset to zero and the H ARQ NACK-to-ACK error indicator is not generated. If the H-ARQ receiver 324 does not successfully receive the failed packet before the timer TErrorIndicator expires, the H-ARQ receiver 324 determines that an H-ARQ NACK-to-ACK error occurs and sends an H-ARQ NACK-to-ACK error indicator to the H-ARQ transmitter 314 unless the number of transmissions of the failed packet has -7-.

WO 2007/079085 PCT/US2006/049306 reached the maximum retransmission limit, the maximum delivery time for the packet, (TDelivery), has expired, and/or the lifespan of the failed packet has expired. [00311 The H-ARQ NACK-to-ACK error indicator is sent from the H ARQ receiver 324 to the H-ARQ transmitter 314 to inform about a NACK-to ACK misinterpretation at the H-ARQ transmitter 314. The H-ARQ NACK-to ACK error indicator is associated with a particular H-ARQ process and a particular packet in the H-ARQ process. The H-ARQ NACK-to-ACK error indicator contains H-ARQ process identity (ID) and a TSN to identify the packet ID in the H-ARQ process. [00321 For synchronous H-ARQ, the H-ARQ process ID and the TSN may be removed since a fixed timing relationship between the failed transmission and the error report can be used to associate the H-ARQ NACK to-ACK error indicator with an H-ARQ process ID and a packet TSN. For example, if there are four (4) synchronous H-ARQ processes, the H-ARQ NACK-to-ACK error indicator may be sent after time t of receiving the packet with a TSN n for which the NACK-to-ACK error happened. [0033] An H-ARQ NACK-to-ACK error indicator packet may be independent of the H-ARQ operation. This is achieved by sending the process identity (if needed) and time offset to identify reception time of the received error. Alternatively, the H-ARQ NACK-to-ACK error indicator may be sent as a physical layer signal at a fixed time offset after the reception of the received error packet . [0034] If more than one packet may be sent simultaneously from the transmitter 310 to the receiver 320, the packets have their own cyclic redundancy check (CRC) and one H-ARQ NACK-to-ACK error indicator may be used to send NACK-to-ACK error indications for several packets. Hence, the H-ARQ NACK-to-ACK error indicator may contain multiple H-ARQ process IDs, associated packet TSNs and/or timing offset. [00351 The H-ARQ NACK-to-ACK error indicator may have its own CRC to ensure reliable transmission. This allows MAC or RLC layer signaling for -8- WO 2007/079085 PCT/US2006/049306 H-ARQ NACK-to-ACK error indication. The H-ARQ NACK-to-ACK error indicator packet may be created either at H-ARQ or ARQ level. [00361 Still referring to Figure 3, to ensure receipt of the H-ARQ NACK to-ACK error indicator, the H-ARQ transmitter 314 may send an ACK to the H-ARQ receiver 324 (step 410). The H-ARQ receiver 324 may repeatedly send the H-ARQ NACK-to-ACK error indicator until the H-ARQ receiver 324 receives an ACK from the H-ARQ transmitter 314 or radio link fails. [00371 After receiving the H-ARQ NACK-to-ACK error indicator at step 408, the H-ARQ transmitter 314 tries to recover the error at an H-ARQ level by retransmitting the failed packet unless the maximum retransmission limit has reached, the maximum delivery time has expired, and/or the lifespan of the failed packet has expired (step 412). The H-ARQ transmitter 314 may send a local NACK to the ARQ transmitter 312 so that the failed packet can be recovered at an ARQ level (step 414). Preferably, the H-ARQ transmitter 314 sends the local NACK to the ARQ transmitter 312 only if the maximum number of retransmissions has been reached, the maximum delivery time for transmission of the failed packet has expired, or the lifespan of the failed packet has expired. [0038] In the prior art, upon successful delivery of a packet, the H-ARQ receiver 324 sends an ACK to the H-ARQ transmitter 314 and the H-ARQ transmitter 314 sends a local ACK to the ARQ transmitter 312. In accordance with the present invention, the H-ARQ transmitter 314 may or may not send a local ACK to the ARQ transmitter 312 in such situation. [00391 After sending the H-ARQ NACK-to-ACK error indicator at step 408, the H-ARQ receiver 324 determines at step 416 whether the H-ARQ receiver 324 does not receive the failed packet successfully before at least one of the following conditions: 1) expiration of Tecoverysync (for synchronous H-ARQ transmission) or TaecoveryAsyne (for asynchronous H-ARQ transmission); 2) receipt of a new H-ARQ packet with a sequence number which is higher than the sequence number of the failed packet by WHARQ; -9- WO 2007/079085 PCT/US2006/049306 3) reaching the maximum number of retransmissions of the failed packet; 4) expiration of the timer TDeuivery; and 5) expiration of the lifespan of the failed packet. [0040] If at least one of the foregoing conditions occurs, the H-ARQ receiver 324 sends a local NACK to the ARQ receiver 322 (step 418). Upon reception of the local NACK, the ARQ receiver 322 may send a status report to the ARQ transmitter 312 to recover the failed packet (step 420). The mapping between an ARQ PDU and an H-ARQ PDU is not relevant as long as the H ARQ receiver 324 is able to identify the ARQ PDU that needs to be recovered. [0041] The ARQ buffer at the ARQ transmitter 312 may be emptied after receiving the status report from the ARQ receiver 322. The status report for the failed packet contains the information about successfully received packets. Alternatively, the ARQ receiver 322 may send a status report after receiving N consecutive packets successfully or expiration of a timer. Alternatively, the ARQ transmitter 312 may poll the ARQ receiver 322 after transmitting the last packet in the buffer. The reason for polling is to recover early from the NACK-to-ACK error at an H-ARQ level for the last packet. Setting the "Poll bit for the last packet" is a. configurable parameter for a data flow. [0042] In order to improve the recovery of the last packet in H-ARQ transmissions, a special small packet with a last packet indication may be sent from the H-ARQ transmitter 314 after the H-ARQ buffer is empty. The transmission of the special packet with a last packet indication ensures early recovery of the loss of the last packet at the H-ARQ level. The H-ARQ receiver 324 sends a response back to the H-ARQ transmitter 314 upon receiving the special packet. The response packet may be a new packet generated at an H ARQ level indicating the last TSN received. Alternatively, the response packet may be sent by using an H-ARQ error indication packet indicating that it is a response to the small packet. [0043] Alternatively, in order to reduce the signaling overhead, a null transmission may be sent after the last data packet in an H-ARQ -10- WO 2007/079085 PCT/US2006/049306 transmission queue to invoke the ACK check on the previous transmission. A null packet only includes control information (i.e., no payload). The H-ARQ transmitter 314 transmits the null packet after reception of an H-ARQ ACK for the last data packet in the H-ARQ transmission queue. Once the H-ARQ receiver 324 receives a null packet, the H-ARQ receiver 324 confirms reception of the last data packet as well as the null packet. If, at the H-ARQ receiver, the last packet was not successfully received and therefore a NACK was sent in response to the last packet and the maximum number of transmissions was not reached, the reception of the null packet will allow the H-ARQ receiver 324 to detect the NACK-to-ACK error. [00441 The transmitter 310 and the receiver 320 may be a WTRU, a base station or any other network entity in a WCDMA, CDMA2000 or long term evolution (LTE) of a third generation (3G) system. "WTRU" includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal data assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. "Base station" includes but is not limited to a Node-B, a site controller, an access point or any other type of interfacing device in a wireless environment. [00451 Embodiments. [0046] 1. A method for implementing H-ARQ-assisted ARQ in a wireless communication system including a transmitter and a receiver, the transmitter including an H-ARQ transmitter and an ARQ transmitter, the receiver including an H-ARQ receiver and an ARQ receiver. [00471 2. The method of embodiment 1 comprising the step of an H ARQ receiver determining whether an H-ARQ NACK-to-ACK error occurs. [00481 3. The method of embodiment 2 comprising the step of the H ARQ receiver sending an H-ARQ NACK-to-ACK error indicator to the H-ARQ transmitter when an H-ARQ NACK-to-ACK error occurs unless the number of retransmissions of a failed packet has reached a maximum retransmission limit, a maximum time for delivery of the failed packet has expired or a lifespan of the failed packet has expired. -11- WO 2007/079085 PCT/US2006/049306 [00491 4. The method as in any of the embodiments 2-3, wherein the H-ARQ NACK-to-ACK error indicator is associated with an H-ARQ process ID and the failed packet at the H-ARQ transmitter. [00501 5. The method of embodiment 4, wherein the H-ARQ NACK to-ACK error indicator includes the H-ARQ process ID and a transmission sequence number of the failed packet. [0051] 6. The method of embodiment 4, wherein the H-ARQ NACK to-ACK error indicator is sent with a fixed timing offset with respect to transmission of the failed packet. [0052] 7. The method as in any of the embodiments 3-6, wherein transmission of the H-ARQ NACK-to-ACK error indicator and transmission of the failed packet are independent. [00531 8. The method as in any of the embodiments 3-7, wherein the H-ARQ NACK-to-ACK error indicator is sent via at least one of physical layer signaling, a MAC layer signaling and an RLC layer signaling. [0054] 9. The method as in any of the embodiments 3-8, wherein more than one packet is transmitted from the H-ARQ transmitter to the H ARQ receiver simultaneously and the H-ARQ NACK-to-ACK error indicator indicates H-ARQ NACK-to-ACK errors of more than one packet. [00551 10. The method as in any of the embodiments 3-9, wherein the H-ARQ NACK-to-ACK error indicator is sent along with a CRC. [0056] 11. The method as in any of the embodiments 3-10, wherein the H-ARQ NACK-to-ACK error indicator is generated by one of the H-ARQ receiver and an ARQ receiver. [0057 12. The method as in any of the embodiments 3-11, further comprising the step of the H-ARQ transmitter sending an ACK to the H-ARQ receiver upon receipt of the H-ARQ NACK-to-ACK error indicator. [0058] 13. The method of embodiment 12, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator repeatedly if the H ARQ receiver does not successfully receive the ACK for the H-ARQ NACK-to ACK error indicator and a radio link between the H-ARQ transmitter and the H-ARQ receiver does not fail. -12- WO 2007/079085 PCT/US2006/049306 [0059] 14. The method as in any of the embodiments 3-13, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator if the H ARQ receiver receives a new packet via the same H-ARQ process assigned for the failed packet instead of retransmission of the failed packet. [0060] 15. The method as in any of the embodiments 3-14, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator if the H ARQ receiver does not receive the failed packet until an error indication timer expires, the error indication timer being set when a NACK is sent to the H ARQ transmitter. [00611 16. The method as in any of the embodiments 3-15, further comprising the step of the H-ARQ transmitter retransmitting the failed packet until the failed packet is successfully delivered unless the maximum retransmission limit has reached, the maximum delivery time has expired or the lifespan of the failed packet has expired. [00621 17. The method of embodiment 16, further comprising the step of the H-ARQ transmitter sending a local NACK to the ARQ transmitter if the maximum retransmission limit has reached, the maximum delivery time has expired or the lifespan of the failed packet has expired, so that the failed packet is recovered at an ARQ level. [0063] 18. The method as in any of the embodiments 3-17, further comprising the step of the H-ARQ receiver setting a recovery timer when the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator. [00641 19. The method of embodiment 18 comprising the step of the H-ARQ receiver sending a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet before the recovery timer expires. [0065] 20. The method of embodiment 19, further comprising the step of the ARQ receiver sending a status report to the ARQ transmitter for recovery of the failed packet. [0066] 21. The method as in any of the embodiments 3-20, further comprising the step of the H-ARQ receiver sending a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until the H -13- WO 2007/079085 PCT/US2006/049306 ARQ receiver receives a packet with a sequence number higher than a sequence number of the failed packet by a predetermined number. [0067] 22. The method of embodiment 21, further comprising the step of the ARQ receiver sending a status report to the ARQ transmitter for recovery of the failed packet. [0068] 23. The method as in any of the embodiments 3-22, further comprising the H-ARQ receiver sending a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until the number of retransmissions of the failed packet reaches a maximum retransmission limit for the failed packet. [0069] 24. The method of embodiment 23, further comprising the step of the ARQ receiver sending a status report to the ARQ transmitter for recovery of the failed packet. [00701 25. The method as in any of the embodiments 3-24, further comprising the step of the H-ARQ receiver sending a local NACK to the ARQ receiver .if the H-ARQ receiver does not receive the failed packet until a maximum time for delivery of the failed packet expires. [00711 26. The method of embodiment 25, further comprising the step of the ARQ receiver sending a status report to the ARQ transmitter for recovery of the failed packet. [00721 27. The method as in any of the embodiments 3-26, further comprising the step of the ARQ receiver sending a status report when the ARQ receiver receives a predetermined number of packets successfully. [0073] 28. The method as in any of the embodiments 3-27, further comprising the step of the ARQ receiver sending a status report when a status reporting timer expires. [0074] 29. The method as in any of the embodiments 3-28, further comprising the step of the ARQ transmitter requesting a status report from the ARQ receiver and the ARQ receiver sending a status report to the ARQ transmitter. [00751 30. The method of embodiment 29, wherein the ARQ transmitter requests the status report after transmitting a last packet. -14-- WO 2007/079085 PCT/US2006/049306 [00761 31. The method as in any of the embodiments 3-30, further comprising the step of the H-ARQ transmitter sending a small packet with a last packet indication after sending a last packet in a buffer. [00771 32. The method of embodiment 31, comprising the step of the H-ARQ receiver sending a response to the small packet, whereby a recovery of the last packet is ensured by the small packet. [0078] 33. The method as in any of the embodiments 31-32, wherein the small packet is a null transmission. [00791 34. The method as in any of the embodiments 31-33, wherein the response to the small packet is transmitted by using the H-ARQ NACK-to ACK error indicator. [00801 35. The method as in any of the embodiments 3-34, wherein parameters for the maximum retransmission limit, the maximum time for delivery of a packet and a lifespan of a packet are configured by a central controlling entity. [0081] 36. The method of embodiment 35, wherein the parameters are configured when the transmitter is active. [0082] 37. The method of embodiment 35, wherein the parameters are configured at the start of a service. [00831 38. The method as in any of the embodiments 35-37, wherein the parameters are configured dynamically depending on QoS requirement of a packet. [0084] 39. The method as in any of the embodiments 3-38, wherein the maximum retransmission limit of a packet is indicated by identifying a particular MAC flow associated with a specific maximum retransmission limit in an associated control signaling for the first transmission. [00851 40. The method as in any of the embodiments 3-38, wherein the maximum retransmission limit of a packet is explicitly indicated in an associated control signaling for the first transmission. [00861 41. A wireless communication system for implementing H ARQ-assisted ARQ. -15- WO 2007/079085 PCT/US2006/049306 [00871 42. The system of embodiment 41 comprising a receiver including an H-ARQ receiver and an ARQ receiver, the H-ARQ receiver being configured to determine whether an H-ARQ'NACK-to-ACK error occurs and send an H-ARQ NACK-to-ACK error indicator to an H-ARQ transmitter unless the number of retransmissions of a failed packet has reached a maximum retransmission limit, a maximum time for delivery of the failed packet has expired or a lifespan of the failed packet has expired. [00881 43. The system of embodiment 42 comprising a transmitter including the H-ARQ transmitter and an ARQ transmitter. [0089] 44. The system as in any of the embodiments 42-43, wherein the H-ARQ NACK-to-ACK error indicator is associated with an H-ARQ process ID and the failed packet at the H-ARQ transmitter. [0090] 45. The system as in any of the embodiments 42-44, wherein the H-ARQ NACK-to-ACK error indicator includes the H-ARQ process ID and a transmission sequence number of the failed packet. [00911 46. The system as in any of the embodiments 42-45, wherein the H-ARQ NACK-to-ACK error indicator is sent with a fixed timing offset with respect to transmission of the failed packet. [00921 47. The system as in any of the embodiments 42-46, wherein transmission of the H-ARQ NACK-to-ACK error indicator and transmission of the failed packet are independent. [00931 48. The system as in any of the embodiments 42-47, wherein the H-ARQ NACK-to-ACK error indicator is sent via at least one of physical layer signaling, a MAC layer signaling and an RLC layer signaling. [00941 49. The system as in any of the embodiments 42-48, wherein the H-ARQ transmitter and the H-ARQ receiver are configured to transmit and receive more than one packet simultaneously and the H-ARQ transmitter is configured to send the H-ARQ NACK-to-ACK error indicator indicating H ARQ NACK-to-ACK errors of more than one packet. [00951 50. The system as in any of the embodiments 42-49, wherein the H-ARQ NACK-to-ACK error indicator is sent along with a CRC. -16- WO 2007/079085 PCT/US2006/049306 [0096] 51. The system as in any of the embodiments 42-50, wherein the H-ARQ NACK-to-ACK error indicator is generated by one of the H-ARQ receiver and an ARQ receiver. [0097] 52. The system as in any of the embodiments 43-51, wherein the H-ARQ transmitter is configured to send an ACK to the H-ARQ receiver upon receipt of the H-ARQ NACK-to-ACK error indicator. [00981 53. The system of embodiment 52, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator repeatedly until the H-ARQ receiver successfully receives the ACK for the H-ARQ NACK-to-ACK error indicator. [00991 54. The system as in any of the embodiments 42-53, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator if the H ARQ receiver receives a new packet via the same H-ARQ process assigned for the failed packet instead of retransmission of the failed packet. [00100] 55. The system as in any of the embodiments 42-54, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator if the H ARQ receiver does not receive the failed packet until an error indication timer expires, the error indication timer being set when a NACK is sent to the H ARQ transmitter. [001011 56. The system as in any of the embodiments 43-55, the H ARQ transmitter retransmits the failed packet until the failed packet is successfully delivered unless the maximum retransmission limit has reached, the maximum delivery time has expired or the lifespan of the failed packet has expired. [001021 57. The system as in any of the embodiments 43-56, wherein the H-ARQ transmitter sends a local NACK to the ARQ transmitter if the maximum retransmission limit has reached, the maximum delivery time has expired or the lifespan of the failed packet has expired, so that the failed packet is recovered at an ARQ level. [001031 58. The system as in any of the embodiments 42-57, wherein the H-ARQ receiver sets a recovery timer when the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator and sends a local NACK to the ARQ -17- WO 2007/079085 PCT/US2006/049306 receiver if the H-ARQ receiver does not receive the failed packet before the recovery timer expires. [001041 - 59. The system of embodiment 58, wherein the ARQ receiver sends a status report to the ARQ transmitter for recovery of the failed packet. [001051 60. The system as in any of the embodiments 42-59, wherein the H-ARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until the H-ARQ receiver receives a packet with a sequence number higher than a sequence number of the failed packet by a predetermined number. [001061 61. The system of embodiment 60, wherein the ARQ receiver sends a status report to the ARQ transmitter for recovery of the failed packet. [00107] 62. The system as in any of the embodiments 42-61, wherein the H-ARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until the number of retransmissions of the failed packet reaches a maximum retransmission limit for the failed packet. [001081 63. The system of embodiment 62, wherein the ARQ receiver sends a status report to the ARQ transmitter for recovery of the failed packet. [001091 64. The system as in any of the embodiments 42-63, wherein the H-ARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until a maximum time for delivery of the failed packet expires. [00110] 65. The system of embodiment 64, wherein the ARQ receiver sends a status report to the ARQ transmitter for recovery of the failed packet. [00111] 66. The system as in any of the embodiments 42-65, wherein the ARQ receiver sends a status report when the ARQ receiver receives a predetermined number of packets successfully. [00112] 67. The system as in any of the embodiments 42-66, wherein the ARQ receiver sends a status report when a status reporting timer expires. [001131 68. The system as in any of the embodiments 43-67, wherein the ARQ transmitter requests a status report from the ARQ receiver and the ARQ receiver sends a status report to the ARQ transmitter. -18- WO 2007/079085 PCT/US2006/049306 [001141 69. The system of embodiment 68, wherein the ARQ transmitter requests the status report after transmitting a last packet. [001151 70. The system as in any of the embodiments 43-69, wherein the H-ARQ transmitter sends a small packet with a last packet indication after sending a last packet in a buffer and the H-ARQ receiver sends a response to the small packet, whereby a recovery of the last packet is ensured by the small packet. [001161 71. The system of embodiment 70, wherein the small packet is a null transmission. [001171 72. The system as in any of the embodiments 70-71, wherein a response to the small packet is transmitted by using the H-ARQ NACK-to ACK error indicator. [00118] 73. The system as in any of the embodiments 42-72, wherein parameters for at least one of the maximum retransmission limit, the maximum time for delivery of a packet and a lifespan of a packet are configured by a central controlling entity. [00119] 74. The system of embodiment 73, wherein the parameters are configured when the receiver is active. [00120] 75. The system of embodiment 73, wherein the parameters are configured at the start of a service. [00121) 76. The system as in any of the embodiments 73-75, wherein the parameters are configured dynamically depending on QoS requirement of a packet. [001221 77. The system as in any of the embodiments 42-76, wherein the maximum retransmission limit of a packet is indicated by identifying a particular MAC flow associated with a specific maximum retransmission limit in an associated control signaling for the first transmission. [00123] 78. The system as in any of the embodiments 42-76, wherein the maximum retransmission limit of a packet is explicitly indicated in an associated control signaling for the first transmission. [001241 79. A receiver for implementing H-ARQ-assisted ARQ. -19- WO 2007/079085 PCT/US2006/049306 [00125] 80. The receiver of embodiment 79 comprising an ARQ receiver and an H-ARQ receiver. [00126) 81. The receiver of embodiment 80 wherein the H-ARQ receiver is configured to determine whether an H-ARQ NACK-to-ACK error occurs and send an H-ARQ NACK-to-ACK error indicator to an H-ARQ transmitter unless at least one of the following has occurred: the number of retransmissions of a failed packet has reached a maximum retransmission limit, a maximum time for delivery of the failed packet has expired and a lifespan of the failed packet has expired. [00127) 82. The receiver of embodiment 81, wherein the H-ARQ NACK-to-ACK error indicator is associated with an H-ARQ process ID and the failed packet at the H-ARQ transmitter. [001281 83. The receiver of embodiment 81, wherein the H-ARQ NACK-to-ACK error indicator includes the H-ARQ process ID and a transmission sequence number of the failed packet. [00129] 84. The receiver as in any of the embodiments 81-83, wherein the H-ARQ NACK-to-ACK error indicator is sent with a fixed timing offset with respect to transmission of the failed packet. [001301 85. The receiver as in any of the embodiments 81-84, wherein transmission of the H-ARQ NACK-to-ACK error indicator and transmission of the failed packet are independent. [001311 86. The receiver as in any of the embodiments 81-85, wherein the H-ARQ NACK-to-ACK error indicator is sent via at least one of physical layer signaling, a MAC layer signaling and an RLC layer signaling. [001321 87. The receiver as in any of the embodiments 81-86, wherein the H-ARQ receiver is configured to receive more than one packet simultaneously and send the H-ARQ NACK-to-ACK error indicator indicating H-ARQ NACK-to-ACK errors of more than one packet. [00133] 88. The receiver as in any of the embodiments 81-87, wherein the H-ARQ NACK-to-ACK error indicator is sent along with a CRC. -20- WO 2007/079085 PCT/US2006/049306 [001341 89. The receiver as in any of the embodiments 81-88, wherein the H-ARQ NACK-to-ACK error indicator is generated by one of the H-ARQ receiver and the ARQ receiver. [00135] 90. The receiver as in any of the embodiments 81-89, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator repeatedly until the H-ARQ receiver successfully receives an ACK for the H ARQ NACK-to-ACK error indicator. [001361 91. The receiver as in any of the embodiments 81-90, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator if the H ARQ receiver receives a new packet via the same H-ARQ process assigned for the failed packet instead of retransmission of the failed packet. [001371 92. The receiver as in any of the embodiments 81-91, wherein the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator if the H ARQ receiver does not receive the failed packet until an error indication timer expires, the error indication timer being set when a NACK is sent to the H ARQ transmitter. [001381 93. The receiver as in any of the embodiments 81-92, wherein the H-ARQ receiver sets a recovery timer when the H-ARQ receiver sends the H-ARQ NACK-to-ACK error indicator and sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet before the recovery timer expires. [001391 94. The receiver as in any of the embodiments 81-93, wherein the ARQ receiver sends a status report to the ARQ transmitter for recovery of the failed packet. [00140] 95. The receiver as in any of the embodiments 81-94, wherein the H-ARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until the H-ARQ receiver receives a packet with a sequence number higher than a sequence number of the failed packet by a predetermined number. [001411 96. The receiver as in any of the embodiments 81-95, wherein the H-ARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until the number of retransmissions -21- WO 2007/079085 PCT/US2006/049306 of the failed packet reaches a maximum retransmission limit for the failed packet. [00142] 97. The receiver as in any of the embodiments 81-96, wherein the H-ARQ receiver sends a local NACK to the ARQ receiver if the H-ARQ receiver does not receive the failed packet until a maximum time for delivery of the failed packet expires. [001431 98. The receiver as in any of the embodiments 81-97, wherein the ARQ receiver sends a status report to the ARQ transmitter for recovery of the failed packet. [001441 99. The receiver as in any of the embodiments 81-98, wherein the ARQ receiver sends a status report when the ARQ receiver receives a predetermined number of packets successfully. [00145] 100. The receiver as in any of the embodiments 81-99, wherein the ARQ receiver sends a status report when a status reporting timer expires. [00146] 101. A transmitter for implementing H-ARQ-assisted ARQ. [00147] 102. The transmitter of embodiment 101 comprising an ARQ transmitter and an H-ARQ transmitter. [001481 103. The transmitter of embodiment 102 wherein the H-ARQ transmitter is configured to receive an H-ARQ NACK-to-ACK error indicator, and at least one of the ARQ transmitter and the H-ARQ transmitter is configured to recover a failed packet corresponding to the H-ARQ NACK-to ACK error. [00149] 104. The transmitter of embodiment 103, wherein the H-ARQ transmitter is configured to send an ACK to the H-ARQ receiver upon receipt of the H-ARQ NACK-to-ACK error indicator. [00150] 105. The transmitter as in any of the embodiments 103-104, wherein the H-ARQ transmitter retransmits the failed packet until the failed packet is successfully delivered unless at least one of the following has occurred: the maximum retransmission limit has reached, the maximum delivery time has expired and the lifespan of the failed packet has expired. [00151] 106. The transmitter as in any of the embodiments 103-105, wherein the H-ARQ transmitter sends a local NACK to the ARQ transmitter if -22- WO 2007/079085 PCT/US2006/049306 the maximum retransmission limit has reached, the maximum delivery time has expired or the lifespan of the failed packet has expired, so that the failed packet is recovered at an ARQ level. [001521 107. The transmitter as in any of the embodiments 103-106, wherein the ARQ transmitter requests a status report from the ARQ receiver. [00153] 108. The transmitter of embodiment 107 wherein the ARQ transmitter requests the status report after transmitting a last packet. [00154 109. The transmitter as in any of the embodiments 103-108, wherein the H-ARQ transmitter sends a small packet with a last packet indication after sending a last packet in a buffer, whereby a recovery of the last packet is ensured by the small packet. [001551 110. The transmitter of embodiment 109 wherein the small packet is a null transmission. [00156] 111. The transmitter as in any of the embodiments 109-110, wherein a response to the small packet is .transmitted by using the H-ARQ NACK-to-ACK error indicator. [001571 Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. The methods or flow charts provided in the present invention may be implemented in a computer program, software, or firmware tangibly embodied in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD ROM disks, and digital versatile disks (DVDs). [001581 Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more -23- 24 microprocessors in association with a DSP core, a controller, a micro controller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. A processor in association with software may be used to implement a radio 5 frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, "a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a 10 microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth@ module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) module. 15 Comprises/comprising and grammatical variations thereof when used in this specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 20 25

Claims

1. A method for implementing hybrid automatic repeat request (H-ARQ) assisted automatic repeat request (ARQ), the method comprising: determining that an H-ARQ negative acknowledgement (NACK)-to-positive 5 acknowledgement (ACK) error has occurred with respect to a failed packet, wherein more than one packet is transmitted simultaneously and the H-ARQ NACK-to-ACK error indicator indicates H-ARQ NACK-to-ACK errors of more than one packet; determining whether or not to transmit an H-ARQ NACK-to-ACK error 10 indicator, wherein the H-ARQ NACK-to-ACK error indicator is not transmitted on a condition that any of the number of retransmissions of the failed packet has reached a maximum retransmission limit, a maximum time for delivery of the failed packet has expired, or a lifespan of the failed packet has expired; and determining whether or not to transmit a local NACK. 15

2. The method of claim 1, wherein the H-ARQ NACK-to-ACK error indicator is associated with an H-ARQ process identity (ID) and the failed packet.

3. The method of claim 4 wherein the H-ARQ NACK-to-ACK error indicator includes the H-ARQ process ID and a transmission sequence number of the failed packet. 20

4. The method of claim 4 wherein the H-ARQ NACK-to-ACK error indicator is transmitted with a fixed timing offset with respect to transmission of the failed packet.

5. The method of claim 1 wherein transmission of the H-ARQ NACK-to-ACK error indicator and transmission of the failed packet are independent. 25

6. The method of claim 1 wherein the H-ARQ NACK-to-ACK error indicator is transmitted via at least one of physical layer signaling, a medium access control (MAC) layer signaling and a radio link control (RLC) layer signaling. 26

7. The method of claim I wherein the H-ARQ NACK-to-ACK error indicator is transmitted along with a cyclic redundancy chock (CRC).

8. The method of claim 1 wherein it is determined not to transmit a local NACK on a condition that the failed packet is not received before expiration of a 5 recovery timer which is set when the NACK-to-ACK indicator is transmitted.

9. The method of claim 1 wherein it is determined not to transmit a local NACK on a condition that the failed packet is not received until after a packet with a sequence number higher than a sequence number of the failed packet by a predetermined number is received.

10 10. The method of claim 1, wherein it is determined not to transmit a local NACK on a condition that the number of retransmissions of the failed packet reaches a maximum retransmission limit for the failed packet.

11. The method of claim 1, wherein it is determined not to transmit a local NACK on a condition that the failed packet is not received until after a maximum 15 time for delivery of the failed packet expires.

12 A hybrid automatic repeat request (H-ARQ) receiver for implementing an H-ARQ-assisted automatic repeat request (ARQ), the receiver being configured to: determine that an H-ARQ negative acknowledgement (NACK)-to-positive 20 acknowledgement (ACK) error has occurred with respect to a failed packet, wherein more than one packet is transmitted simultaneously and the H-ARQ NACK-to-ACK error indicator indicates H-ARQ NACK-to-ACK errors of more than one packet; determine whether or not to transmit an H-ARQ NACK-to-ACK error 25 indicator, wherein the H-ARQ NACK-to-ACK error indicator is not transmitted on a condition that any of the number of retransmissions of the failed packet has reached a maximum retransmission limit, a maximum time for delivery of the failed packet has expired, or a lifespan of the failed packet has expired; and determining whether or not to transmit a local NACK. 27

13. The receiver of claim 15 wherein the H-ARQ NACK-to-ACK error indicator is associated with an H-ARQ process identity (ID) and the failed packet.

14. The receiver of claim 18 wherein the H-ARQ NACK-to-ACK error indicator includes the H-ARQ process ID and a transmission sequence number of the 5 failed packet.

15. The receiver of claim 18 wherein the H-ARQ NACK-to-ACK error indicator is transmitted with a fixed timing offset with respect to transmission of the failed packet.

16. The receiver of claim 15 wherein transmission of the HARQ NACK-to-ACK 10 error indicator and transmission of the failed packet are independent.

17. The receiver of claim 15 wherein the H-ARQ NACK-to-ACK error indicator is transmitted via at least one of physical layer signaling, a medium access control (MAC) layer signaling and a radio link control (RLC) layer signaling.

18. The receiver of claim 15 wherein the H-ARQ NACK-to-ACK error indicator 15 is transmitted along with a cyclic redundancy check (CRC).

19. The receiver of claim 15 wherein it is determined not to transmit a local NACK on a condition that the failed packet is not received before expiration of a recovery timer which is set when the NACK-to-ACK indicator is transmitted.

20. The receiver of claim 15 wherein it is determined not to transmit a local 20 NACK on a condition that the failed packet is not received until after a packet with a sequence number higher than a sequence number of the failed packet by a predetermined number is received.

21. The receiver of claim 15 wherein it is determined not to transmit a local NACK on a condition that the number of retransmissions of the failed packet 25 reaches a maximum retransmission limit for the failed packet. 28

22. The receiver of claim 15 wherein it is determined not to transmit a local NACK on a condition that the failed packet is not received until after a maximum time for delivery of the failed packet expires.

23. The method of claim 1 substantially as hereinbefore described with 5 reference to figure 3 of the accompanying drawings.

24. The receiver of claim 15, substantially as hereinbefore described with reference to figure 3 of the accompanying drawings. INTERDIGITAL TECHNOLOGY CORPORATION WATERMARK PATENT & TRADE MARK ATTORNEYS P30591AUO0