HK1103562A - Method and apparatus for overhead reduction in an enhanced uplink in a wireless communication system - Google Patents

Description

Method and apparatus for reducing system overhead in an enhanced uplink in a wireless communication system

Priority requirements according to 35 U.S.C. § 119

This application is filed on 35 U.S.C. § 119(e) 5/2004, entitled "Technique for Overhead Reduction in Enhanced Uplink (EUL)", assigned to the assignee of the present priority of U.S. provisional patent application No. 60/568,623, which is hereby expressly incorporated by reference.

Technical Field

The present application relates generally to communication systems, and more particularly, to an apparatus and method for transmitting data with less data overhead in a wireless communication system.

Background

As wireless communications become more prevalent, the demand for system resources increases. As third generation mobile communication systems (3G) become more widely accepted, the demand for many new types of high bandwidth wireless data services is expected to grow significantly. 3G air interface standards, such as WCDMA, tend to increase demand for scarce bandwidth by popularizing a number of bandwidth-intensive wireless services, such as wireless transmission of multimedia, wireless email, internet access, video streaming, image transmission, and switched gaming. Currently, wireless systems tend to reach capacity limits during peak usage times in densely populated areas, and the demand for bandwidth is expected to increase. System designers are continually looking for ways to transmit data more efficiently to meet the ever-increasing demand for bandwidth. Ironically, as system usage approaches capacity limits, the incidence of dropped wireless calls actually increases due to competition between simultaneously transmitted signals, requiring additional wireless resources to retransmit the lost data.

High Speed Downlink Packet Access (HSDPA) is an advancement of the WCDMA standard that streamlines downlink communications to wireless users. Another aspect of the increase in radio demand is the transmission from the radio user to the base station, i.e. the uplink. High speed uplink transmission is being investigated by another WCDMA technology, the Enhanced Uplink (EUL) project. The purpose of EUL is to enhance high speed data uplink access. Although the EUL standard is a step forward in the correct direction, there is still room for improvement in the efficiency of wireless uplink transmissions.

Disclosure of Invention

In one aspect, the present invention provides a method in a wireless communication system. The method includes forming data into an unidentified data packet for transmission; and transmitting the non-identification data packet. The non-identification packets are transmitted according to a prearranged transmission scheme that allows identification of the non-identification packets upon receipt based on instances (instances) during which the non-identification packets are transmitted.

In another aspect, the present invention provides a wireless communication system. The system includes an encoder for encoding data into an unidentified data packet; and a transmit circuit for transmitting an initial transmission of the non-identification data packet. The system also includes receiver circuitry for receiving a signal including a NACK associated with the initial transmission; and a processor comprising logic organized to control retransmission of said data sent in response to receipt of said NACK. The retransmission is sent according to a pre-arranged transmission scheme.

In yet another aspect, the present invention provides a mobile station. The mobile station includes means for encoding data into an unidentified data packet; means for transmitting an initial transmission of the non-identifying data packet; means for receiving a signal comprising a NACK associated with the initial transmission; and a processor module for controlling retransmission of the data in response to receiving the NACK. The retransmission is sent at a predetermined number of instances after the initial transmission to allow the retransmission to be associated with the initial transmission.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

FIG. 1 illustrates an exemplary wireless network architecture that may be used to implement embodiments of the present invention;

FIG. 2 illustrates some details of a wireless User Equipment (UE) and a node B base station in a wireless network;

fig. 3 illustrates a representation of an uplink signal transmitted from a wireless UE to a node B and then to an RNC, wherein the UE uplink transmission to the node B does not include packet identification information;

figure 4 illustrates the data flow between components in a wireless system between a user equipment and a component of a radio network subsystem;

FIGS. 5A and 5B together are a flow chart illustrating the operation of a node B receiving a UE signal and retransmitting the signal to the RNC; and

fig. 6 is a flowchart illustrating an operation of transmitting a signal from a UE to a node B and retransmitting lost or corrupted data from the UE.

Detailed Description

Fig. 1 depicts a typical wireless network architecture 100 that supports mobile stations and client devices in various embodiments of the invention. The system described is a wide-standby code division multiple access (WCDMA) system, however, embodiments of the present invention may also be used with CDMA2000, GSM/GPRS or other such wireless systems and protocols. The wireless system typically comprises a core network 150, one or more radio network subsystems (RNS 140) and a wireless user equipment 110. The RNSs 140 include one or more of each radio network controller (RNC130) connected to the base stations 120 (node B). Depending on the details of this embodiment, node B120 may take other forms, may be called other names, or have common aspects with other systems, such as a Base Transceiver Station (BTS) or a Base Station System (BSS). In some implementations, the radio network controller, labeled RNC130 in the figure, may take other forms, called other names, or have the same aspects as other systems, such as a Base Station Controller (BSC), a Mobile Switching Center (MSC), or a Serving GPRS Support Node (SGSN). The SGSN is typically a core network entity handling packet switched connections and the MSC is a core network entity handling circuit switched connections. Fig. 1 depicts a wireless user equipment (UE110) which may have many different names, such as a cellular phone, a mobile station, a wireless handset, and so on. The scope of the present invention covers these and other such systems, names, terms and implementations for components of similar types of wireless systems.

The wireless network depicted in the figure is exemplary only and may include any system that allows communication over the air between components that may be connected in the manner described for wireless system 100 in fig. 1. The UE110 may include many different types of wireless devices, including one or more cellular telephones, wirelessly connected computers, PDAs (personal digital assistants), pagers, navigation devices, music or video content download units, wireless gaming devices, inventory control units, or other similar types of devices that communicate wirelessly over an air interface. Cellular or other wireless communication services may communicate using a carrier network over data links or other network links through a fixed network 150, which may be any of the following: the Public Switched Telephone Network (PSTN), the internet, an Integrated Services Digital Network (ISDN), one or more Local Area Networks (LAN) or Wide Area Networks (WAN) or Virtual Private Networks (VPN), or other such networks.

The wireless system 100 controls messages or other information sent through the RNS 140 to the UE110, typically as data packets. Each RNC130 is typically connected to one or more node B120 base stations. In the case where more than one node B120 is associated with a certain UE110, all node bs 120 in this active set of the UE110 may have the same notation of E-DCH frame number so that data packets transmitted to and from two different node bs 120 involved with the UE110 through Soft Handover (SHO) can be correctly interpreted and correctly ordered. The RNC130 may be viewed as operating within the wireless system 100 in a manner similar to the normal switching node of a landline network, such as a PSTN or ISDN. RNC130 typically includes logic (e.g., a processor or computer) to manage and control wireless UE 110. This logic of the RNC130 manages and controls some functions of the wireless UE110 registered at the node bs associated with the RNC130, such as call routing, registration, authentication, location update, handover, and/or coding schemes. The RNC130 is connected to the node B120 via a network configured for data transfer and/or voice information, typically via a network of fixed communication lines in a manner similar to the interconnection of the network 150.

Communications transmitted to and from each of the RNC130 and node B120 components are typically conducted over the landline network, which may include portions of the internet and/or PSTN. Upstream, the RNC130 may be connected to multiple networks, such as those mentioned above, e.g., PSTN, internet, ISDN, etc., allowing the customer and UE110 devices to access a wider communications network. In addition to voice transmission, data may be transmitted to the client device via SMS or other OTA methods known in the art. The subsystem RNS 140, including the RNC130, controls the radio link between the node B120 and the UE 110. Each node B120 has one or more transmitters and receivers to transmit information to UE110 or receive information from UE 110.

Node B120 wirelessly broadcasts data messages or other information to UE110 using over-the-air (OTA) methods known to those skilled in the art. For example, the wireless signals between the UE110 and the node B120 may be based on any of several different technologies, including but not limited to CDMA (code division multiple access), TDMA (time division multiple access), FDMA (frequency division multiple access), OFDM (orthogonal frequency division multiplexing), and any system using a hybrid coding technique, such as GSM, or other similar wireless protocols used in communication or data networks.

Fig. 2 illustrates some details of UE110 and node B120. Node B120 includes an encoder/decoder 125 that encodes information to be transmitted and decodes received information using an appropriate encoding protocol or scheme. The node B includes receiver/transmitter circuitry 127 for wirelessly receiving non-identifying data packets from the UE110 and for transmitting the data packets to the RNC130 (which may be transmitted over landline). Node B120 also includes a processor 121 that contains circuitry or other logic that is capable of performing or controlling the processes and operations in wireless communications, particularly the processes or operations described herein. For example, processor 121 includes logic organized to identify that an unidentified retransmission is associated with a previously received initial transmission based on a predetermined number of retransmissions received after the initial transmission failed.

The node B120 may also include a memory 123 for storing various protocols, routines, procedures or software for use in conducting the wireless communications described herein. For example, memory 123 may store one or more transmission schemes, protocols, or policies for communicating with UE 110. These transmission schemes, strategies and protocols include information related to: timing for retransmission due to lost or corrupted data, redundancy version coding (if any), and any coding scheme or protocol used for transmission and reception of wireless communications. This information may also be stored in the memory of the RNC130 and communicated to the node B120 as needed or when periodic updates and system maintenance are performed. As shown in fig. 2, an embodiment of UE110 typically includes a processor or other logic 107, memory 109, and encoder/decoder circuitry 111 that implement functions similar to those of the corresponding parts of node B120. For example, encoder circuitry 111, or other circuitry similar to UE110, may be configured to encode, or encapsulate data into non-identifying packets for transmission to node B120. Each UE110 also has an antenna 113, receiver/transmitter circuitry 115, and other circuitry known to those skilled in the art for wireless information reception and transmission.

The wireless system 100 may include information in a Home Location Register (HLR) and a plurality of Visitor Location Registers (VLRs) for call routing and roaming. The centralized HLR typically contains administrative information for each UE110 registered in the wireless system 100, as well as current location information for that UE 110. The VLR stores selected management information from the centralized HLR for call control and provision of registered subscriber services for each UE110 currently under control of the RNC 130. Each RNC130 typically has a VLR associated with it, often stored in the memory of the RNC 130. Other registers may be used for authentication and security in wireless network 110, such as an Equipment Identification Register (EIR) and an authentication center (AuC).

UE110 includes logic labeled as processor 107 in fig. 2. In practice, this logic may be configured as follows: one or more processing circuits executing resident configured logic, a microprocessor, a Digital Signal Processor (DSP), a microcontroller, a combination of these, or other similar hardware, software, and/or firmware, is configured to perform at least the operations described herein, e.g., the operations of UE110 described in fig. 6. UE110 may include a registered Subscriber Identity Module (SIM) or other such circuitry that identifies UE110 so that it can make and receive calls, and receive other registered services, in the terminal. The International Mobile Equipment Identity (IMEI) of UE110 stored in the SIM card uniquely identifies this particular UE 110. The SIM card may also have an International Mobile Subscriber Identity (IMSI) for registering subscribers for system identification, a copy of the key from the AuC register for authentication, and other information about security, identification, and communication protocols. UE110 often has one or more software applications installed or downloaded, such as games, news, stock monitors, and the like.

Depending on the transmission conditions of the channel, bit errors may cause interruptions, which need to be addressed for seamless wireless communication. The probability that a frame contains bit errors is a function of the channel bit error rate and, in this case, the amount of data or the frame length. Wireless system 100 has one or more mechanisms for detecting transmissions that are prone to bit errors and/or recovering from transmissions that have bit errors, such as automatic repeat request (ARQ) and/or Forward Error Correction (FEC). Although conventional implementations of EUL require a significant amount of system overhead that consumes valuable bandwidth resources, embodiments of the present invention can reduce the system overhead associated with EUL, thereby increasing the overall system performance of processing uplink transmissions.

ARQ uses a feedback channel that allows the receiver to send information back to the transmitter related to transmission success or failure. Typically, ARQ schemes rely on an out-of-band feedback channel, although some ARQ schemes may also be implemented with in-band feedback. ARQ may be explicitly implemented using a negative acknowledgement (NACK, sometimes denoted NAK) to request retransmission. ARQ may also be implemented implicitly using an Acknowledgement (ACK) in conjunction with a timeout rule. Upon receipt of the transmission signal from the UE110, the node B120 may be configured to send an ARQ signal providing feedback on the transmission in the form of an ACK or NACK. For example, in a system with explicit out-of-band ARQ feedback, if data from UE110 is corrupted or lost before it is received by node B120, node B sends a NACK back indicating that UE110 should retransmit the failed transmission.

The retransmission is performed according to a prearranged transmission scheme that sends the retransmission a predetermined number of instances (number of slots) after the instance of the failed initial transmission. In general, the prearranged transmission scheme schedules retransmission in the next set of instances, occupying the same relative positions in this instance (e.g., the third instance, the fourth instance, etc. in this set). The NACK may be repeated for each failed retransmission up to a predetermined number of times, i.e. up to the number of allowed repeat attempts, or until this instance has been received without error, in which case a positive Acknowledgement (ACK) is sent. Error recovery comes into play in the case where the retransmission itself contains data errors, but the error-free instance is produced by soft combining two or more transmissions/retransmissions.

Embodiments use a hybrid arq (harq) protocol to recover from bit errors received in a transmission instance. In addition to ARQ acknowledgement feedback techniques, HARQ systems also increase the use of FEC. This technique has the potential to improve the throughput of the system because FEC enables the system to detect and correct bit errors in addition to ARQ feedback needed for retransmission. The FEC scheme implements an FEC code using parity bits, or redundant bits. Thus, FEC schemes add a measure of redundancy to the transmitted data in a manner that allows the receiver to detect and correct errors that occur in the transmission channel. This technique enables the transmitted signal to be less susceptible to noise without increasing the signal power. Thus, this technique can reduce the number of retransmissions required, thereby improving throughput performance, but requires more complex transmitter and receiver designs to implement FEC. The use of FEC in HARQ systems can reduce the Bit Error Rate (BER) or increase the data throughput for a given transmit output power. The BER value for a particular ARQ scheme will be determined by tracking the rate of undetected errors (i.e., bit errors that would occur regardless of whether an ARQ scheme is present). However, BER is not a reliable measure of the performance of a particular ARQ scheme, since the BER value should go to zero if the ARQ scheme is valid. The use of FEC in HARQ systems can reduce the Frame Error Rate (FER) (similar to BER, a frame-based error metric). Data throughput rate is another metric that is often used to measure the effectiveness of a particular HARQ scheme. The data throughput rate can be measured as the average number of encoded data bits that the receiver correctly receives during the time that the transmitter transmits one bit. The throughput rate measured with bits/channel can be considered with the retransmission overhead of the HARQ scheme. The theoretical throughput limit of an ARQ scheme is the maximum transmission capacity of the channel. The HARQ system has a lower throughput limit than the ARQ system.

Since the HARQ technology was originally proposed, it has become more and more complex, and many different types of HARQ have been implemented. The type I HARQ system is an improvement of the ARQ system in that the type I HARQ adds FEC redundancy to each transmitted frame and then performs a de-FEC function in the receiver to estimate the bits in the frame. Cyclic Redundancy Check (CRC) calculations can detect the presence of errors in the received data. The FEC encoding/decoding and CRC calculation are repeated for each retransmission request. Doing so reduces the theoretical throughput to a rate no greater than the FEC code used. The type I HARQ system may use the same code for error detection and error recovery. The type II HARQ scheme uses a form of incremental redundancy that adaptively changes the number of added parity bits in the data retransmission instance. Type II HARQ systems have the ability to dynamically change the new increase in their throughput when channel conditions change. This adaptation makes such systems particularly useful in applications with fluctuating channel conditions, such as mobile and satellite packet data, where there is a feedback channel and latency due to retransmission delays is acceptable. The initial transmission of a type II HARQ packet consists of payload information bits and CRC bits. Incremental redundant parity bits are added to increase the chance of recovering the discarded data transmission if errors are detected that require retransmission.

The retransmission from UE110 to node B120 may be soft combined with the initial transmission in an effort to recover from the received error. Since the retransmission is combined with the previous transmission (including the previous retransmission), the coding scheme used for the initial transmission and the retransmission should be rate-compatible. Sometimes no bit error is detected at the node B. This situation would warrant an RLC retransmission error recovery scheme in which a NACK is sent upstream from node B120. However, RLC retransmissions cause significant delays. To avoid RLC retransmission delays, the UE can initiate a new round of transmission of the same packet if an erroneous packet is received after the last retransmission. That is, in some embodiments, MAC layer retransmission is enabled to avoid RLC retransmission, thereby shortening delay.

Providing incremental redundancy in retransmissions (e.g., in a type II HARQ scheme) requires encoding the retransmitted data in a different but still compatible manner than the initial transmission. In this way, the initial transmission and retransmission can be soft combined to increase the chance of error recovery. In an EDGE system, backward compatibility can be achieved by maintaining the same RLC/MAC (radio link control/medium access control) architecture as used in GSM that uses blocks belonging to the same "family" for retransmission. For example, information in a transmission using one MCS-9 radio block code may be combined with a retransmission using two MCS-6 radio block codes, or may be combined with a retransmission using four MCS-3 radio block codes. Data encoded using MCS-9, MCS-6, or MCS-3 may be soft combined because the schemes are from the same family and have a 1-2-4 code rate relationship. Transmissions encoded using schemes from different MCS families may also be combined, as long as bit stuffing is used to compensate for different block sizes.

In addition to HARQ, EUL may be implemented with some other new uplink functionality including, for example, node B controlled scheduling and shorter Transmission Time Interval (TTI) lengths. This may require the establishment of new MAC functions, which may be included in MAC-e (a new MAC entity). The purpose of MAC-E is to cover HARQ and scheduling functions and therefore relevant protocol details and issues should be considered, such as Transport Format Combination (TFC) selection, number of enhanced uplink dedicated channel (E-DCH) transport channels and location of the re-ordering entity.

One aspect of HARQ is that it supports out-of-sequence data delivery. Since Radio Link Control (RLC) relies on sequential delivery, reordering is performed at the Medium Access Control (MAC) layer before data is delivered to the RLC. The re-ordering entity may be located in either the node B120 or the RNC130 of the radio system 100 shown in fig. 1. For downlink communications, the HSDPA reordering entity is typically located in the node B120 close to where coordination is performed, since the choice of the number of Protocol Data Units (PDUs) to be put in a single packet depends on the coordinated data rate. However, for uplink communications, there is no need to place a re-ordering entity in the coordinating node B120. Thus, there is little benefit to putting the re-ordering entity into the node B120, as opposed to putting it in the RNC 130. In fact, since a soft handover from the node B120 to the next must occur, it may in fact be necessary to place a re-ordering entity for uplink communication in the RNC 130. Placing the re-ordering entity in the RNC130 will allow selective combining before re-ordering, and will most likely reduce the re-ordering delay due to waiting for sequential data. Another reason for putting the uplink re-ordering entity in the RNC130 is that the buffering requirements can be reduced. Due to the benefits of buffer multiplexing, reordering in the RNC130 can alleviate the high buffering requirements in case of reordering in the node B120.

As discussed above, placing HARQ in the node B120 allows for fast retransmission of data that was in error when received. The downlink retransmission scheme employed in HSDPA can be similarly used for the uplink of the enhanced dedicated channel (E-DCH) in EUL, one difference being that synchronous HARQ is employed in EUL as opposed to asynchronous HARQ used in HSDPA. Depending on the specific details of this implementation, synchronous HARQ operation for uplink transmissions may provide benefits such as reduced control channel overhead, less buffering requirements, reduced delay variation, better load prediction, or simplified logging and coordination mechanisms. Thus, if synchronous HARQ with deterministic redundancy version sequences is supported, the overhead requirements can be reduced by ignoring tags or other packet identification information, such as HARQ process IDs and new data indicator bits. In some embodiments, a redundancy version (RID) may be the only relevant signaling required.

Fig. 3 illustrates a representation of an uplink signal transmitted from wireless UE110 to node B120 and then to RNC130, where the UE uplink transmission to the node B does not include packet identification information. As used herein, the term packet identification information refers to a coded Transmission Sequence Number (TSN), or tag, that is used to identify a particular packet. In conventional systems, in-band control information about the queue ID is used to reorder the buffer containing the payload and the TSN is used to identify the sequence of packets. In other words, conventional uplink systems use in-band queue IDs and TSNs in a manner similar to their use in HSDPA downlink transmissions. In contrast, embodiments of the present invention implemented with synchronous HARQ may omit the TSN, transmit non-identification packets, and thus reduce system overhead. Based on the synchronous HARQ timing, the node B120 may append a tag (e.g., E-DCH frame number) once a packet is successfully received. This tag is attached when a packet is decoded correctly and is ready to be sent to the RNC. Thus, by combining the label with each packet sent by the node B120 to the RNC130, reordering can be performed in the RNC130 based on the label.

The horizontal axis in fig. 3 represents time, and examples (which may be called time slots in some systems) are labeled t 0 to t 14 in the figure. The value of time in the figure is arbitrary; t-0 to t-14 may be relabeled as t-750 to t-764 without affecting the description herein. In fig. 3, a lower case "t" along the horizontal axis represents the actual time of the instance, e.g., the transmission time. In the figure, the capital "T" at the node B indicates the notation of the node B of the E-DCH frame number that should be associated with the received packet in this example. If the data packet received at the node B is a retransmission (e.g., 306), the retransmitted data packet 306 should be associated with the node B's token at the time of the initial failed transmission 304. Thus, 306 receives the E-DCH frame number tag T2 because 306 is a retransmission of the failure 304 that occurred at T2.

Above the time axis are three boxes representing packets at various points in the wireless system: at the UE, then at the node B, and finally at the RNC. These three blocks are used to represent data packets at UE110, node B120, and RNC130 of fig. 1 that are ready for transmission to the next component in wireless system 100. Within each box is written a representation of the overhead packet identification information to be transmitted with each packet during this instance or transmission. For example, the data packet 301 to be transmitted at time t-0 is unidentified, and therefore, for transmitting this data packet from the UE to the node B, the data packet 301 does not contain any data packet identification information. Thus, the boxes of packet 301 are empty in the figure. Only payload information is sent for transmission of data packet 301 from the UE to the node B. Once the packet sent at time T-0 is received without error at the node B, the packet is appended with packet identification information T-0 at 302 before transmitting it to the RNC. The packet identification information T-0 indicates that the node B expects the packet 302 to be initially transmitted at time T-0. Various embodiments may use different formats for additional packet identification information at the node B, as long as the format is suitable for indicating the time or order of the sequence of packets (or packets initially transmitted if the packets are identified as retransmitted, e.g., 306).

If the node B has expected a retransmission of a previously failed transmission, the node B will append a marker from the moment the failed transmission was started. For example, an erroneous data packet 302 transmitted at time t-2 is received at the node B, as indicated by an "X" at 304. Since the data packet 304 received by the node B contains errors, the node B transmits a NACK back to the UE instead of forwarding the failed data packet down to the RNC. According to one prearranged transmission scheme, after sending the NACK, the node B may expect retransmission of the failed data packet 304 a predetermined number of instances (5 instances in this example) after the failed initial transmission. As shown in fig. 3, five instances after the failed transmission (304), at time t-7, the node B receives a retransmission of the data packet (306). The various embodiments of the present invention are implemented in a synchronous system, so that retransmission can be scheduled to occur after a predetermined number of instances, followed by the corresponding instance of the next set of instances. In the example shown in fig. 3, the retransmission occurs after five instances. The retransmission of the failed packet 303 sent at time t-2 is scheduled to occur at time t-7, denoted as packet 305 in the figure. Packet 303 is in the third instance of the first set of packets in fig. 3 and packet 305 is in the third instance of the second set of packets. Thus, 305 is in the same relative position of the instances in the group after 303. Having determined that the retransmission resulted in the receipt of such data without error, node B marks the packet with packet identification information T2 (which may be the result of a soft combination of 303 and 305) at 306 because node B expects a retransmission of packet 303, which was initially sent at time T2 at time T7. After appending the packet identification information T-2 to this packet, the node B transmits this packet to the RNC. This packet 311 is put back in the correct order, at the time of receipt at the RNC, into the position indicated by the dashed line.

If the transmission of the data packet fails twice, a second retransmission of the data packet will be sent after the initial transmission of both sets of instances. For example, the initial transmission 307 fails and the retransmission 308 fails after the NACK signal, whereupon the data packet 309 is retransmitted in response to the NACK signal. Since this system is a synchronous system, the node B has already expected a retransmission of the packet that failed at time t 3 (packet 307) at the five following instances of the failed packet at time t 8, or at the fourth instance in the group following the failed packet that also failed at the fourth instance in its group. Since the packet at time t-8 is also corrupted, the node B sends a NACK signal and then expects a second retransmission of the failed packet during time t-13, five more instances later (in the fourth instance of the next group). When the transmission of the data packet 309 at time T-13 results in correct reception of the data (at 310), the node B appends the data packet identification information T-2 to the data packet 310 and transmits it to the RNC. With regard to NACK errors, as discussed above, NACK errors are handled by the RLC. In the case where a NACK error occurs and a NACK is erroneously interpreted as an ACK at the UE, the RLC will determine the missing data packet and will issue a retransmission request from the RLC.

Upon receipt in the RNC, the packets are reordered according to their packet identification information appended at the node B. By ordering the data packets on the basis of their time stamps as determined by the pre-arranged transmission scheme, the RNC is able to put the received data packets in their correct order. For example, retransmitted packets with appended packet identification information T-2, T-3, and T-9 (311, 312, and 313, respectively) are reordered into the correct order as indicated by the dashed lines. It is noted that the data packets retransmitted after a NACK (e.g., 305, 308, 309) may be encoded in the same manner as the originally transmitted data packets they are involved in, or they may be encoded into incremental redundancy versions using a compatible encoding scheme.

Fig. 4 illustrates the data flow between the components in a wireless system comprising a user equipment UE110 and the components of the radio network subsystem (node B120 and RNC 130). UE110, node B120 and RNC130 may be arranged in the manner shown in fig. 1. In various embodiments disclosed herein, UE110 transmits non-identifying packets of data 401 that do not contain any packet identifying information attached to or embedded in the packet. Once the data packets are received by the node B120 without error, the node B120 can transmit the data packets 403 to the RNC130, at which time the data packets have been appended with data packet identification information.

The packet identification information appended 403 is based on a pre-arranged transmission scheme and the instance or time slot in which packet 401 was received. Based on this prearranged transmission scheme and whether a predetermined number of instances have previously received an error-free data packet at the node B, the node B120 knows whether to expect an initial transmission of new data or a retransmission of previously received corrupted data. Packet 403 illustrated in FIG. 4The additional packet identification information is T_ID. Referring back to the previous figures, FIG. 3, T of packet 306_IDIs T-2, which means 306 (received at time T-7) is a retransmission of the data (packet 303) originally transmitted at T-2.

Data flow and T as in FIG. 4_IDThe use of additional packet identification information in the embodiments disclosed herein is described as being different from the tags used in conventional systems. In conventional systems, the uplink packet 401 sent from the UE to the node B would additionally include packet identification information. That is, a conventional data packet transmitted from a UE will have a payload of data, and also require an additional amount of overhead dedicated to identifying the data packet, e.g., including pkt in the data packet in addition to the data_IDWherein pkt_IDIndicating conventional packet identification information appended to the packet transmitted from the UE. Pkt included in a legacy packet_IDMay be a packet number or other identifying information such as a HARQ process ID, a queue ID, or a Transmit Sequence Number (TSN). Various embodiments of the present invention reduce overhead on uplink transmissions from UE110 to node B120 by omitting packet identification information and instead sending non-identification packets without any identification tags or other packet identification information. Then, upon receipt of the non-identification packet at node B120, node B's control logic can append the packet identification information to the non-identification packet received from UE 110. The additional packet identification information may take the form of an E-DCH frame number tag.

Fig. 5A and 5B together are a flow chart illustrating the operation of receiving a UE signal and retransmitting the signal to an RNC at a node B in various embodiments of the present invention. The UE, node B and RNC may be UE110, node B120 and RNC130 in fig. 1. The method starts at 501 and proceeds to 503 where 503 the node B receives an unidentified data packet from the UE. As used herein, an "unidentified" packet is a packet without an identification tag or other packet identifying information attached to it, such as the packet number, E-DCH frame number, HARQ process ID, queue ID, TSN, or other type of data intended for identifying the packet. Upon receipt of the non-identifying packet at the node B, the method proceeds to 505 where, based on the previously occurring operations, the node B determines whether it is expecting a retransmission of previously corrupted data or an initial transmission of a new data packet, according to a prearranged transmission scheme.

By using a prearranged transmission scheme, the node B can determine whether the received unidentified data packet is a retransmission or an initial transmission of a new data packet. If a NACK is sent in response to a corrupted packet received a predetermined number of HARQ instances before, the node B will expect that the corrupted packet will be retransmitted a predetermined number of HARQ instances after. In the synchronous wireless system 100, a prearranged transmission scheme may be implemented to send retransmissions in corresponding instances (e.g., time slots) in the next set of instances. For example, as shown in fig. 3, the node B receives a corrupted data packet 304 in the HARQ instance at time t-2. Thus, according to the prearranged transmission scheme, the node B expects retransmission of data in 304 packets that failed a predetermined number of instances later (five instances later). After five instances, at time t-7, node B receives the packet labeled 306 in the figure. Since node B has expecting a retransmission of the previously failed packet, node B appends packet identification information T2 to packet 306, indicating 306 that the packet was a retransmission of the 303 packet originally sent at time T2. According to the prearranged transmission scheme in the embodiments of the present invention, the node B retransmits the corrupted data packet after expecting a predetermined number of HARQ instances or in a corresponding instance of the next set of instances in the synchronous system. If there are five instances in each group, as shown in the example of fig. 3, then the node B would expect a retransmission after receiving five instances of the failed packet.

If retransmission is expected, the method follows the "yes" branch from 505 to 507 where it is verified whether the received data packet was a retransmission of a previously sent packet containing errors or corrupted packet, i.e., for some reason, the data was not correctly received and decoded at the node B. The verification of the retransmitted data packet in the node B may be performed by: either by an error detection procedure or by comparing the data received in the data packet considered to be retransmitted with the data of the previously corrupted data packet. If retransmission is expected, the node B may assume that the newly received packet has the same contents as the failed one of the previous corresponding examples (although in the case where the contents are an incremental redundancy version, it may be encoded in a different manner). Some embodiments may be configured to use the timing of the packets as a purpose of reordering the packets, and then provide an indication of new data, such as a new data indication, to prevent ambiguity: it is simply a new initial transmission or retransmission of the data packet.

If no retransmission is expected in the instance of received data in 505, the method proceeds down the "no" branch from 505 to 509, where an error detection is performed on the new packet deemed to have been initially transmitted from the UE. Error detection typically involves a Cyclic Redundancy Check (CRC) of the data in the packet, but may be performed with another redundancy check, such as a checksum or Frame Check Sequence (FCS), or by using an Error Correction Code (ECC), such as a hamming code, Reed-Solomon code, Reed-Muller code, binary Golay code, convolutional code, turbo code, or other similar type of error detection or error detection/correction code known to those skilled in the art. In some embodiments, verification 507 may be performed in the same manner or in conjunction with error detection performed in 509.

Once error detection and/or verification has been completed in 507 and 509, the method proceeds to 511 where it is determined whether an error exists in the packet. If no errors are found, the method follows the "no" branch to 513 where an ACK signal is transmitted back to the UE acknowledging receipt of the data packet. In some embodiments, no ACK is transmitted back to the UE and the block is ignored 513. The method proceeds from 513 (or from 511 directly if no ACK is sent) to 521 where additional packet identification information is appended, embedded or associated with the non-identification packet received from the UE. The packet identification information may be in the form of an E-DCH frame number. In alternative embodiments, the packet identification information may take any of several forms, such as a packet number, a HARQ process ID, a queue ID, a Transmit Sequence Number (TSN), or a notation of a node B that may represent the original transmission time that should be associated with the packet received in this example, or other similar type of data suitable for identifying the packet.

If it is determined in block 511 that an error does exist in the packet, the method follows the yes branch to 515. If the data packet is a retransmission at 515, the method proceeds to 517 where the received retransmission data packet is combined with the corresponding initial transmission previously received and retransmissions intervening therebetween. The data may be combined using any number of techniques, including selective combining, soft combining, selective soft combining, or a combination thereof. It is possible that little or no data from the previously received initial transmission is suitable for combining with the retransmitted data packet. In this case, any data suitable for combining will be combined — that is, data will generally be combined if the combination of data can increase the chance of decoding the data packet without error. Once the data from the retransmitted data packets are combined at 517, the method proceeds to 519 where a determination is made as to whether the data can be decoded without error. If the combined data is found to contain errors or is still corrupted 519, then the method follows the no branch to 529. If, however, the combined data is found to be error free 519, the method proceeds to 521 as per the yes branch.

In block 521, once the label or packet identification information has been added to the packet in 521, the method proceeds to 523 where the node B transmits the packet with overhead data for identification to the RNC. The tag or packet identification information represents the E-DCH frame number of the first subpacket associated with the transmission. At this point, the operation of processing the packet has been completed, except for some operations that may be considered housekeeping operations. The method proceeds from 523 to 525 and if the packet is a retransmitted packet, the method proceeds from 525 to 527, following the yes branch. At 527, the data associated with the retransmitted packet that has been saved is discarded. The discarded data may include an initial transmission and subsequent retransmission (if any) from the previous corresponding instance. In some embodiments, rather than explicitly discarding data, the data may simply be overwritten with new data (see block 531), in which case the operations of block 527 need not be performed. Returning to block 525, if the transmitted packet is not retransmitted, the method proceeds from 525 to 535 according to the "no" branch.

Returning to block 515, if the packet was originally transmitted, rather than being retransmitted, the method follows the "no" branch to 531 where the data is stored in the node B for future use in combination with subsequent retransmissions. Once the data has been stored in 531, the method proceeds to block 533 where a NACK is sent from the node B back to the UE. In response to this NACK, the UE will send a retransmission of the corrupted packet in the corresponding instance in the next set of instances (after a predetermined number of instances). Upon completion of the NACK transmission, the method proceeds from 533 to 535 where it is determined whether the communication has ended, that is, whether the telephone call, wireless upload of data, or other wireless communication from the UE has ended.

Returning to block 519, if the combined data is found to contain errors or is corrupted 519, the method proceeds to 529 according to the "no" branch. In block 529, it is determined whether another retransmission is attempted. Typically, the system will be configured to send no more than a predetermined number of retransmissions before dropping the data packet. Once the maximum number of retransmissions has been attempted, if the packet is still unable to be decoded without errors, the data associated with the packet (e.g., the initial transmission and all subsequent retransmissions) is discarded and no further retransmissions are attempted for the packet. A counter or other logic in the node B may be used to keep track of the number of retransmissions and whether the maximum number has been reached. If, at block 529, it is determined that the predetermined maximum number of retransmissions has been reached, no further retransmissions are attempted, the method proceeds to block 527 along the "no" branch, the stored data is discarded, and the method proceeds to block 535. If, on the other hand, in block 529, it is determined that another retransmission is to be attempted, the method proceeds from 529 to 531 according to the yes branch, where data from the current packet is stored for soft combining with future retransmissions. Once a NACK has been sent per block 533, the method proceeds to 535.

At 535, a determination is made as to whether the communication is complete. If the wireless link is still on and there are more packets to transmit, the communication has not yet ended, and the method follows the "no" branch to 537. At 537, it is determined whether the next packet has been received in the next instance. If the next packet has been received, the method follows the "yes" branch from 537 to block 503 again. If, at block 537, the next packet has not been received, the method proceeds to 539 to await the next transmission. From 539, the method loops back to 537 where it is again determined whether the next packet has been received. Returning to 535, if it is determined that the transmission has ended, the method proceeds to 541 as per the yes branch. For example, if a party to a telephone call hangs up the telephone, or a wirelessly connected computer is disconnected, or the link is torn down, the transmission may be considered to have ended, and the method follows the "no" branch from 535 to 541, where the method ends.

Fig. 6 illustrates operations in a UE to transmit a packet to a node B in various embodiments of the invention. The method starts at 601 as soon as information to be transmitted to the node B is obtained at the UE. Such information may include encoded voice information to be wirelessly transmitted in a cellular telephone call. The data may also include an uplink from the UE for one of many available wireless multimedia services, such as wireless internet access, video streaming, image transmission, wireless email, interactive gaming, and the like. Once data is obtained for transmission from the UE to the node B, the method proceeds from block 601 to 603 where a determination is made as to whether a NACK exists, which NACK has been received from the node B indicating that the received data packet was in error and should be retransmitted. If there is no NACK and there is no need to retransmit the data packet, the method proceeds from 603 to 605 for the initial transmission of the data packet, according to the no branch. In 605, data ready for initial transmission to the node B is formed into a data packet. Data packets transmitted from a UE to a node B on the uplink according to embodiments of the present invention do not contain packet identification information, i.e., they are unidentified. The uplink data packet from the UE then does not include the E-DCH frame number, HARQ process ID, queue ID, Transmission Sequence Number (TSN), or other such system overhead data used to identify the data packet in conventional systems. Packing the data in block 605 may entail sequentially extracting the data and encoding the data for further transmission, as well as such other operations as are well known to those of ordinary skill in the art. Once the data has been packed in 605, the method proceeds to block 607. At 607, the next available packet in the communication is transmitted to the node B. Once the data packet has been transmitted, the method proceeds to 609 where the data of the transmitted data packet is stored in the UE for use in the future in which case the data packet must be retransmitted.

Returning to block 603, if a NACK exists, then retransmission will occur in place of the initial transmission, and the method follows the yes branch to 611 where the stored packet associated with the NACK is encoded for retransmission. To increase the chance of error recovery at the node B, the retransmission may be sent as a redundant version of the data packet encoded in a manner compatible with the initial transmission. This allows soft combining of the retransmission with the initial transmission. For example, in an EDGE system, retransmission from the GSM block that originally transmitted the same "family" can be soft combined with the first data packet. For example, the retransmit packet encoded with MCS-9 is compatible with MCS-6 and MCS-3 transmissions. Once the retransmission has been encoded 611, the method proceeds to 613 where the retransmission is sent, and then to 609 where the retransmitted data is saved. In some embodiments, the initial data packet may continue to be saved, and there may be no need to save the retransmitted data packet at all. In these embodiments, block 609 after 617 is ignored and the method proceeds directly to 615.

In block 615, a determination is made whether a NACK has been received for a previously transmitted data packet. If a NACK has been received, the method proceeds from 615 to 617 on the "NACK" branch, where data from the packet associated with the NACK is queued for retransmission. If there are no NACKs in block 615, the method follows the "one and no" branch to 619. Embodiments of the present invention may be implemented in terms of either explicit or implicit ARQ structures. Fig. 6 depicts an explicit ARQ, where a NACK is sent back from the node B, requesting an uplink retransmission from the UE. Although not shown in the figure, an ACK may be sent back in addition to or instead of a NACK, acknowledging receipt of the data packet without error. Embodiments implemented with implicit ARQ rely on acknowledgments of receipt in the node B with no errors with ACKs, combined with a timeout rule to indicate that retransmission is required if no ACK for a data packet is received within a predetermined length of time.

If, at block 619, a NACK is not received within a predetermined length of time from the transmission of a given data packet, assuming that no retransmission is required, the method proceeds from 619 to 621 where the data stored for the previously transmitted given data packet is discarded. In embodiments using ACKs, receipt of an ACK at the UE for a given data packet will result in the saved data being discarded. In some embodiments, rather than explicitly discarding or deleting saved data, it may instead be overwritten with new data. When the saved data is discarded at 621, the method proceeds to block 623. Similarly, returning to block 619, if a predetermined time (or a predetermined number of instances) has not elapsed since the transmission of a given data packet, then that data packet is not discarded and the method follows the "no" branch to 623.

In block 623, a determination is made as to whether the end of the communication has been reached. If it is determined that the communication has ended, the method proceeds along the YES branch to 629 where the process ends. If it is determined at 623 that the communication has not ended, the method proceeds along the "no" branch to 625. In block 625, a determination is made as to whether data is available in the UE for transmission on the uplink. If data is available, the method follows the yes branch and loops back to block 603 to perform the process of transmitting data from the UE to the node B. If at 625 it is determined that no data is available for retransmission, the method proceeds along the "no" branch to 627. Some situations may use default rules to avoid hanging while waiting for data. For example, in the NACK error case in the last subpacket (where NACK is mistaken for ACK), or if the UE cannot support the same data rate as the failed subpacket. In block 627, the UE waits for data to be transmitted and then loops back to block 625 again to check if data has been obtained. Returning to 623, if it is determined that the communication has ended, the method proceeds along the yes branch to 629, where the process ends.

The drawings are provided to illustrate the present invention, to enable the invention to be practiced, and to explain the principles of the invention. Some of the operations used to practice the invention, which are illustrated in method blocks in the figures, may be performed in an order different than that shown in the figures. For example, in fig. 5A, the ACK may be sent (513) after the packet identification information (521) is appended. This is merely an example; other operations depicted in the figures may be performed in an order different than that shown. Further, those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill in the art would appreciate that the various illustrative logical blocks, modules, circuits, and algorithm routines described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, firmware, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Those of ordinary skill in the art will appreciate that the described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described herein in connection with the disclosed embodiments may be implemented as follows: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, computer, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The operations of a method, routine or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An tangible storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. The storage medium may also be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. The processor and the storage medium may reside as discrete components in a user terminal.

Various modifications to the embodiments described and discussed above will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other embodiments without departing from the spirit and scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

In describing various embodiments of the present invention, specific terminology is employed for the purpose of illustration and for the purpose of clarity. However, the invention is not limited to the specific terminology so selected. Each specific term includes equivalent terms known to those skilled in the art, as well as equivalent techniques that operate in a similar manner to accomplish a similar purpose. Accordingly, this description is not intended to limit the invention. The object of the invention is to be protected broadly within the scope of the following claims.

Claims (20)

1. A method in a wireless communication system, comprising:

forming the data into an unidentified data packet for transmission; and

transmitting the non-identification data packet, wherein the non-identification data packet is transmitted according to a pre-arranged transmission scheme so as to be identifiable upon receipt of the non-identification data packet based on instances during which the non-identification data packet is transmitted.

2. The method of claim 1, further comprising:

receiving a NACK indicating a transmission failure of the non-identifying data packet.

3. The method of claim 2, further comprising:

if the initial transmission of the data fails, sending an unidentified retransmission of the data;

wherein said retransmission is sent a predetermined number of instances after said initial transmission in accordance with said pre-arranged transmission scheme.

4. The method of claim 3, wherein the wireless communication system is a synchronous system.

5. The method of claim 3, wherein said instance during which said non-identifying data packet is transmitted is one of a plurality of instances arranged into a plurality of groups, each of said plurality of groups comprising said predetermined number of instances; and

wherein the relative position of the initial transmission in the first set of instances corresponds to the relative position of the retransmission in the second set of instances.

6. The method of claim 2, wherein the wireless communication system conforms to a WCDMA protocol and includes a node B;

wherein the user equipment transmits an unidentified data packet of said data to said node B; and

wherein the node B transmits the NACK.

7. A wireless communication system, comprising:

an encoder for encoding data into an unidentified data packet;

a transmit circuit for transmitting an initial transmission of the non-identifying data packet;

a receiver circuit for receiving a signal including a NACK associated with the initial transmission; and

a processor comprising logic to control retransmission of the data in response to receiving the NACK;

wherein the retransmission is sent according to a pre-arranged transmission scheme.

8. The wireless communication system of claim 7, wherein the retransmission is sent a predetermined number of instances after the initial transmission in accordance with the pre-arranged transmission scheme.

9. The wireless communication system according to claim 7,

wherein the wireless communication system conforms to a WCDMA protocol and comprises a node B transmitting the NACK; and

wherein said wireless communication system comprises a wireless device comprising said transmit circuitry to transmit said initial transmission of said non-identification data packet.

10. The wireless communication system according to claim 7,

wherein the wireless communication system is a synchronous system.

11. A method of operating in a wireless communication system, the method comprising:

receiving an unidentified initial transmission of a data packet transmitted wirelessly through the wireless communication system;

identifying the initial transmission based on instances during which the initial transmission was received in accordance with a pre-arranged transmission scheme;

performing an error detection to determine whether the initial transmission is corrupted; and

appending data packet identification information to the data packet upon determining that the initial transmission is not corrupted.

12. The method of claim 11, wherein the packet identification information is appended at a base station and represents an E-DCH frame number of the initial transmission; and

wherein the wireless communication system is a synchronous system.

13. The method of claim 12, further comprising:

and transmitting the data packet added with the data packet identification information to a radio network controller upstream.

14. The method of claim 11, further comprising:

transmitting a NACK upon determining that the initial transmission is corrupted;

receiving an unidentified retransmission of the data transmitted in the initial transmission in response to the NACK; and

associating the retransmission with the initial transmission based on instances during which the retransmission was received in accordance with the pre-arranged transmission scheme.

15. The method of claim 14, wherein the instance is one of a plurality of instances arranged in a plurality of groups, each of the plurality of groups including a predetermined number of the instances; and

wherein the relative position of the initial transmission in the first set of instances corresponds to the relative position of the retransmission in the second set of instances.

16. The method of claim 11, wherein the unidentified initial transmission of the data packet is received at a base station; and

wherein the wireless communication system conforms to a WCDMA protocol.

17. A wireless communication system, comprising:

a receiver circuit for wirelessly receiving an unidentified initial transmission data packet;

a decoder for decoding the initial transmission received by the receiver circuit;

transmit circuitry to transmit a signal including a NACK associated with the initial transmission when the initial transmission is corrupted; and

a processor comprising logic to identify a retransmission as associated with the initial transmission based on the retransmission received a predetermined number of instances after the initial transmission.

18. The wireless communication system according to claim 17,

wherein said wireless communication system is compliant with a WCDMA protocol and comprises a base station including said receiver circuitry for receiving said unidentified initial transmission data packet.

19. The wireless communication system of claim 18, wherein the base station is a node B for appending packet identification information to the initial transmission to indicate an E-DCH frame number of the initial transmission when the initial transmission is error free; and

wherein the wireless communication system is a synchronous system.

20. A mobile station for operating in a wireless communication system, the mobile station comprising:

means for encoding data into an unidentified data packet;

means for transmitting an initial transmission of the non-identifying data packet;

means for receiving a signal comprising a NACK associated with the initial transmission; and

a processor module for controlling retransmission of the data in response to receiving the NACK;

wherein the retransmission is sent after a predetermined number of instances of the initial transmission to associate the retransmission with the initial transmission.