Abstract:
A method includes generating automatic repeat request feedback information at a first device in response to a downlink transmission from a second device; encoding the feedback information to comprise an indication of a number of streams received in the downlink transmission and transmitting encoded feedback information to the second device. Another method includes transmitting a multi-stream downlink transmission from a first device to a second device; receiving encoded hybrid automatic repeat request feedback information from the second device; decoding the received hybrid automatic repeat request feedback information at the first device; and determining from the encoding of the hybrid automatic repeat request feedback information at least a number of streams that were actually received by the device from the downlink transmission. A wireless link between the devices can be a 2×2 MIMO link. Also disclosed are memory mediums for storing program instructions to implement the methods, and apparatus including user equipment and base stations constructed to carry out the methods.

Description:
CLAIM OF PRIORITY FROM COPENDING PROVISIONAL PATENT APPLICATION 
       [0001]    This patent application claims priority under 35 U.S.C. §119(e) from Provisional Patent Application No. 60/849,497, filed Oct. 2, 2006, the disclosure of which is incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer program products and, more specifically, relate to techniques that provide feedback related to hybrid automatic repeat request. 
       BACKGROUND 
       [0003]    The following abbreviations are herewith defined: 
       3GPP third generation partnership project 
     ACK acknowledge 
     ARQ automatic repeat request. 
     CQI channel quality indication 
     DL downlink (Node-B to UE) 
     DTX discontinuous transmission 
     FDD frequency division duplex 
     HARQ hybrid ARQ 
     HSDPA high speed downlink packet access 
     HS-DPCCH high speed dedicated physical control channel 
     HS-DSCH high speed downlink shared channel 
     HS-PDSCH high speed physical downlink shared channel 
     HS-SCCH shared control channel for HS-DSCH 
     MCS modulation and coding scheme 
     MIMO multiple input multiple output 
     NACK not acknowledge, negative acknowledge 
     Node-B base station 
     UE user equipment 
     UL uplink (UE to Node-B) 
     UMTS universal mobile telephony system 
     UTRA UMTS terrestrial radio access 
       [0004]    3GPP RAN1 meeting #45 8.-12.5.2006 agreed to recommend specifying a 2×2 (dual transmit—dual receive antenna—dual code word) MIMO technique for HSDPA. 
         [0005]    As is known in the art, MIMO only provides gains in good channel conditions, and thus a single stream transmission should be applied when the channel conditions are less than what will provide an adequate MIMO dual-stream transmission. 
         [0006]    In addition to dual stream transmission the selected MIMO scheme was determined to be a dual code word system. This implies that each of the streams should have independent HARQ operation. 
         [0007]    The HSDPA delivers downlink HARQ feedback (ACK/NACKs) in the UL on a HS-DPCCH physical channel for use by a Node-B packet scheduler. Based on the provided feedback Node-B the scheduler makes decisions whether to perform re-transmissions for the failed transmission or whether to transmit a new packet for each stream separately. 
         [0008]    Referring to 3GPP TS25.212, V7.1.0 (2006-06), 3rd generation Partnership Project; Technical Specification Group Radio Access Network; Multiplexing and channel coding (FDD) (Release 7), section 4.7.1.1 describes the HARQ feedback as a 1-bit indication (ACK/NACK) that is (10,1) repetition coded. 
         [0009]    Referring to 3GPP TS25.211, V7.0.0 (2006-06), 3rd generation Partnership Project; Technical Specification Group Radio Access Network; Physical channels and mapping of transport channels onto physical channels (FDD) (Release 7), section 5.2.1.2 “HS-DPCCH” defines the HS-DPCCH channel structure for delivering the coded bits to the Node-B in the UL. 
         [0010]    As is described in section 5.2.1.2, the frame structure of the HS-DPCCH is defined in  FIG. 2A  (shown herein also as  FIG. 2A ). The HS-DPCCH carries uplink feedback signaling related to downlink HS-DSCH transmission. The HS-DSCH-related feedback signaling consists of Hybrid-ARQ Acknowledgment (HARQ-ACK) and Channel-Quality Indication (CQI). Each sub-frame of length 2 ms (3*2560 chips) consists of 3 slots, each of length 2560 chips. The HARQ-ACK is carried in the first slot of the HS-DPCCH sub-frame. The CQI is carried in the second and third slot of a HS-DPCCH sub-frame. There is at most one HS-DPCCH on each radio link. The HS-DPCCH can only exist together with an uplink DPCCH. The timing of the HS-DPCCH relative to the uplink DPCCH is shown in section 7.7 of 3GPP TS25.211. 
         [0011]    The spreading factor of the HS-DPCCH is 256. i.e., there are 10 bits per uplink HS-DPCCH slot. The slot format for the uplink HS-DPCCH is defined in Table 5A, shown herein as  FIG. 2B . 
         [0012]    There is at least one inherent potential problem in the functioning of HARQ signaling. More specifically, the HS-DSCH transmission to a UE is indicated on the HS-SCCH. The HS-SCCH signaling for MIMO also indicates the number of applied streams. If the number of streams is detected incorrectly by the UE due to some reception error, the HARQ feedback in UL will reflect this reception error. In this case the UE would provide the HARQ feedback assuming wrong number of streams/code words. The Node-B might not have a means to detect such errors correctly unless the encoding of the HARQ feedback is designed to support that. 
         [0013]    For example, if independent HS-SCCH signaling is provided for each HS-PDSCH (e.g., for each stream), the UE may detect only one HS-SCCH correctly. In such a case the UE would report a single ACK/NACK based on the detected stream. 
         [0014]    If the Node-B is unable to detect this situation where the UE erroneously assumes only a single stream being transmitted, then unnecessary higher layer re-transmissions may occur since a detection miss would be erroneously interpreted as an ACK. 
         [0015]    R1-062031, “HS-DPCCH in support of D-TxAA”, August 28th-September 1st, Qualcomm Europe, makes a proposal that assumes two independent ACK/NACKs (for each stream), or only a single ACK/NACK. However, no indication on the number of streams received is provided. 
         [0016]    Reference can also be made to 3GPP TSG-RAN WG1, MIMO R7, Teleconference, Sep. 27, 2006, R1-MIMOR7-QCOM-09, ACK/NACK coding, Qualcomm Europe, which suggests the use of two separate (5,1) repetition block codes on the first ten bits of a HS-DPCCH TTI, and possibly interleaving the two blocks of (5,1) repetition codes. 
       SUMMARY OF THE EXEMPLARY EMBODIMENTS OF THIS INVENTION 
       [0017]    The foregoing and other problems are overcome, and other benefits are realized by the use of the exemplary embodiments of this invention. 
         [0018]    In a first aspect thereof the exemplary embodiments of this invention pertain to a method, that includes generating automatic repeat request feedback information at a first device in response to a downlink transmission from a second device; encoding the feedback information to comprise an indication of a number of streams received in the downlink transmission and transmitting encoded feedback information to the second device. 
         [0019]    In a further aspect thereof the exemplary embodiments of this invention pertain to a memory medium that stores computer program instructions the execution of which results in operations that comprise generating automatic repeat request feedback information at a first device in response to a downlink transmission from a second device; encoding the feedback information to comprise an indication of a number of streams received in the downlink transmission and transmitting encoded feedback information to the second device. 
         [0020]    In another aspect thereof the exemplary embodiments of this invention pertain to an apparatus that includes a receiver configurable to receive a downlink transmission from a device; a feedback generator configurable to generate hybrid automatic repeat request feedback information in response to the received downlink transmission; an encoder configurable to encode the generated hybrid automatic repeat request feedback information to comprise an indication of a number of streams received in the downlink transmission; and a transmitter configurable to transmit the encoded hybrid automatic repeat request feedback information to the device. 
         [0021]    In a still further aspect thereof the exemplary embodiments of this invention pertain to a method that comprises transmitting a multi-stream downlink transmission from a first device to a second device; receiving encoded hybrid automatic repeat request feedback information from the second device; decoding the received hybrid automatic repeat request feedback information at the first device and determining, from the encoding of the hybrid automatic repeat request feedback information, at least a number of streams that were actually received by the device from the downlink transmission. 
         [0022]    In another aspect thereof the exemplary embodiments of this invention pertain to an apparatus that comprises a transmitter configurable to transmit a multi-stream downlink transmission to a receiving device; a receiver configurable to receive encoded hybrid automatic repeat request feedback information from the receiving device; a decoder configurable to decode the received hybrid automatic repeat request feedback information and a data processor that is coupled to said decoder and configurable by execution of computer program instructions to determine, from the encoding of the hybrid automatic repeat request feedback information, at least a number of streams that were actually received by the receiving device from the downlink transmission. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    In the attached Drawing Figures: 
           [0024]      FIG. 1  shows a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention. 
           [0025]      FIG. 2A  reproduces  FIG. 2A  of 3GPP TS25.211, V7.0.0 (2006-06), and shows the frame structure for the uplink HS-DPCCH. 
           [0026]      FIG. 2B  reproduces Table 5A of 3GPP TS25.211, V7.0.0 (2006-06), and shows the fields of the HS-DPCCH. 
           [0027]      FIG. 3  is a logic flow diagram that is descriptive of the operation of a method, and a computer program product, of the UE shown in  FIG. 1 . 
           [0028]      FIG. 4  is a logic flow diagram that is descriptive of the operation of a method, and a computer program product, of the Node-B shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Reference is made first to  FIG. 1  for illustrating a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention. In  FIG. 1  a wireless network  1  is adapted for communication with a UE  10  via a Node B (base station)  12 . The network  1  may include a network control element NCE  14 . The UE  10  includes a data processor (DP)  10 A, a memory (MEM)  10 B that stores a program (PROG)  10 C, and a suitable radio frequency (RF) transceiver  10 D for bidirectional wireless communications with the Node B  12 , which also includes a DP  12 A, a MEM  12 B that stores a PROG  12 C, and a suitable RF transceiver  12 D. The wireless link transmissions between the UE  10  and the Node-B  12  are assumed to conform to the 2×2 multi-antenna MIMO scheme, and thus there may actually be multiple transmit and receive antennas at each end of the link. The Node B  12  is coupled via a data path  13  to the NCE  14  that also includes a DP  14 A and a MEM  14 B storing an associated PROG  14 C. The PROGs  10 C and  12 C are assumed to include program instructions that, when executed by the associated DP, enable the electronic device to operate in accordance with the exemplary embodiments of this invention, as will be discussed below in greater detail. 
         [0030]    Relatedly, also shown in  FIG. 1  is a HARQ unit  10 E at the UE  10  and a packet scheduler (PS) unit  12 D and HARQ information decoder  12 F at the Node-B  12 . These units operate in accordance with the exemplary embodiments of this invention, as will be discussed below in greater detail. 
         [0031]    In general, the exemplary embodiments of this invention may be implemented by computer software executable by the DP  10 A of the UE  10  and the DP  12 A of the Node-B  12 , or by hardware, or by a combination of software and hardware. 
         [0032]    In general, the various embodiments of the UE  10  can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions. 
         [0033]    The MEMs  10 B,  12 B and  14 B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DPs  10 A,  12 A and  14 A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. 
         [0034]    In accordance with the exemplary embodiments of this invention certain information that specifies the number of streams received (and actually detected) by the UE  10  is included in the HARQ feedback to the Node-B  12 . This beneficially enables the Node-B  12  to unambiguously distinguish dual stream ACK/NACK signaling from only single stream ACK/NACK signaling in accordance with the encoding of the HARQ feedback information. 
         [0035]    To achieve this it is preferred that the UL HARQ feedback is encoded by the HARQ unit  10 E in such a way that the single stream and dual stream cases can be decoded unambiguously at the Node-B  12  by the decoder  12 F, such as by the use of separate code words, single stream and dual stream cases. 
         [0036]    As one non-limiting example of providing the HARQ feedback with code word information, effectively six code words are selected from a 10-bit long sequence to produce a code. The information fields are: A, N, AA, AN, NA, NN, i.e., all possible combinations of single stream (the first two fields) and dual stream (the remaining four fields) ACK (A) and NACK (N). 
         [0037]    To further refine the code structure, the codewords may be selected so that the probability of occurrence of undesired error events is reduced by, for example, optimizing the Hamming distances between the code words. 
         [0038]    As another non-limiting example of providing the HARQ feedback with code word information, the ACK and NACK indications for each stream are encoded by, for example, a (5,1) block code or repetition code, and DTX is used on an unused part of the message, i.e., if only single stream is received. That is, the other information field would be subject to DTX if UE  10  assumes that it has been only allocated a single stream. In this case, and by example, the code words may be: AX, NX, AA, AN, NA, NN where X indicates DTX in the bit field. 
         [0039]    With regard to the foregoing note that one suitable and non-limiting generation matrix may be simply: G=(11111). The repetition code may be quite simple, such as by repeating either the 1 or 0. The use of block and repetition codes, and codecs therefor, per se is well known, and not further described herein. 
         [0040]    As should be appreciated, by thus indicating the number of detected streams/code words in the HARQ feedback more reliable HARQ feedback signaling can be provided, thereby reducing or eliminating an occurrence of higher layer re-transmissions to the UE  10 . 
         [0041]    Based on the foregoing it should be apparent that the exemplary embodiments of this invention provide methods, apparatus and computer program product(s) to indicate a number of detected streams in HARQ feedback to the Node-B  12 . 
         [0042]    Referring now to  FIG. 3 , a method and computer program product executed by a first device operates in response to a DL transmission from a second device to generate HARQ feedback information (Block  3 A), to encode the HARQ feedback information to comprise (at least) an indication of a number of streams received in the DL transmission (Block  3 B), and to transmit the encoded HARQ feedback information to the second device (Block  3 C). 
         [0043]    In the method and computer program product, there are a maximum of two streams, and where encoding the HARQ feedback information comprises selecting a code word from a plurality of code words, e.g., from six code words: A, N, AA, AN, NA, NN, thereby providing all possible combinations of single stream and two stream ACK (A) and NACK (N) information. 
         [0044]    In the method and computer program product, there are a maximum of two streams, and where encoding the HARQ feedback information comprises using one of a (5,1) block code or a repetition code, and using DTX on an unused part of the message to provide the code word: AX, NX, AA, AN, NA, NN providing all possible combinations of single stream and two stream ACK (A) and NACK (N) information, where X indicates DTX in the bit field. 
         [0045]    In the method and computer program product of the previous three paragraphs, where the DL transmission is received from a HS-DSCH by a UE, and where the encoded HARQ feedback information is sent to a Node-B on a HS-DPCCH. 
         [0046]    In the method and computer program product of the previous four paragraphs, where a wireless link between the first and second devices comprises a 2×2 MIMO wireless link. 
         [0047]    Also disclosed is a first device comprising a HARQ unit operable in response to a reception of DL transmission from a second device to generate HARQ feedback information that is encoded to comprise an indication of a number of streams received in the DL transmission. The HARQ unit has an output coupled to a transmitter for providing the encoded HARQ feedback information for transmission to the second device. 
         [0048]    In the first device of the previous paragraph there are a maximum of two streams, and the HARQ feedback information is encoded by selecting a code word from a plurality of code words: A, N, AA, AN, NA, NN, providing all possible combinations of single stream and two stream ACK (A) and NACK (N) information. 
         [0049]    In the first device there are a maximum of two streams, and the HARQ feedback information is encoded using one of a (5,1) block code or a repetition code, and by using DTX on an unused part of the message to provide the code word: AX, NX, AA, AN, NA, NN providing all possible combinations of single stream and two stream ACK (A) and NACK (N) information, where X indicates DTX in the bit field. 
         [0050]    In the first device of the previous three paragraphs, the DL transmission is received from a HS-DSCH, and the encoded HARQ feedback information is sent to a Node-B on a HS-DPCCH. 
         [0051]    In the first device of the previous four paragraphs, a wireless link between the first and second devices comprises a 2×2 MIMO wireless link. 
         [0052]    Referring now to  FIG. 4 , a method and computer program product executed by a first device operates to receive encoded HARQ feedback information from a second device (Block  4 A), to decode the received encoded HARQ feedback information (Block  4 B), and to determine from the encoding of the HARQ feedback information at least a number of streams that were received in a DL transmission that was previously transmitted to the second device (Block  4 C). 
         [0053]    In the method and computer program product of the previous paragraph there are a maximum of two streams, and where the received HARQ feedback information is encoded by selecting a code word from a plurality of code words: A, N, AA, AN, NA, NN, providing all possible combinations of single stream and two stream ACK (A) and NACK (N) information. 
         [0054]    In the method and computer program product, there are a maximum of two streams, and where the received HARQ feedback information is encoded using one of a (5,1) block code or a repetition code, and is sent using DTX on an unused part of the message to provide the code word: AX, NX, AA, AN, NA, NN providing all possible combinations of single stream and two stream ACK (A) and NACK (N) information, where X indicates DTX in the bit field. 
         [0055]    In the method and computer program product of the previous three paragraphs, where the DL transmission is received from a HS-DSCH by a UE, and where the encoded HARQ feedback information is received by a Node-B on a HS-DPCCH. 
         [0056]    In the method and computer program product of the previous four paragraphs, where a wireless link between the first and second devices comprises a 2×2 MIMO wireless link. 
         [0057]    Also disclosed is a Node-B that comprises a receiver to receive encoded HARQ feedback information from a UE, a decoder to decode the received encoded HARQ feedback information, and a determination unit to determine from the encoding of the HARQ feedback information at least a number of streams that were received in a DL transmission that was previously transmitted to the UE (Block  4 C). 
         [0058]    The various blocks shown in  FIGS. 3 and 4  may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). 
         [0059]    The encoded code word in these various embodiments includes information on the number of code words (and the number of received streams) and HARQ ACK/NACK, and one code word is transmitted from the allowed set of code words. 
         [0060]    In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. 
         [0061]    As such, it should be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be fabricated on a semiconductor substrate. Such software tools can automatically route conductors and locate components on a semiconductor substrate using well established rules of design, as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility for fabrication as one or more integrated circuit devices. 
         [0062]    It should be noted that the terms “connected,” “coupled,” or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are “connected” or “coupled” together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be “connected” or “coupled” together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples. 
         [0063]    Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this invention. 
         [0064]    Furthermore, some of the features of the various non-limiting and exemplary embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.