Abstract:
This invention is a method of wireless communication having a communications protocol providing more downlink subframes than uplink subframes. The user equipment transmits a combination of a plurality of ACK/NAK response signals and related data. The related data could be the number of bits N of the plurality of ACK/NAK response signals or the number of detected downlink communications grants S requiring ACK/NAK response signals. This related data could be a cyclical redundancy check set of bits which may be scrambled upon the numbers N or S. Similar selections are feasible with resource elements or an index of a modulation symbol or codeword.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority under 35 U.S.C. 119(e)(1) to U.S. Provisional Application Nos. 61/033,592 filed Mar. 4, 2008, 61/035,502 filed Mar. 11, 2008 and 61/047,586 filed Mar. 24, 2008. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The technical field of this invention is wireless communications. 
       BACKGROUND OF THE INVENTION 
       [0003]      FIG. 1  shows an exemplary wireless telecommunications network  100 . The illustrative telecommunications network includes base stations  101 ,  102  and  103 , though in operation, a telecommunications network necessarily includes many more base stations. Each of base stations  101 ,  102  and  103  are operable over corresponding coverage areas  104 ,  105  and  106 . Each base station&#39;s coverage area is further divided into cells. In the illustrated network, each base station&#39;s coverage area is divided into three cells. Handset or other user equipment (UE)  109  is shown in Cell A  108 . Cell A  108  is within coverage area  104  of base station  101 . Base station  101  transmits to and receives transmissions from UE  109 . As UE  109  moves out of Cell A  108  and into Cell B  107 , UE  109  may be handed over to base station  102 . Because UE  109  is synchronized with base station  101 , UE  109  can employ non-synchronized random access to initiate handover to base station  102 . 
         [0004]    Non-synchronized UE  109  also employs non-synchronous random access to request allocation of up-link  111  time or frequency or code resources. If UE  109  has data ready for transmission, which may be traffic data, measurements report, tracking area update, UE  109  can transmit a random access signal on up-link  111 . The random access signal notifies base station  101  that UE  109  requires up-link resources to transmit the UE&#39;s data. Base station  101  responds by transmitting to UE  109  via down-link  110 , a message containing the parameters of the resources allocated for UE  109  up-link transmission along with a possible timing error correction. After receiving the resource allocation and a possible timing advance message transmitted on down-link  110  by base station  101 , UE  109  optionally adjusts its transmit timing and transmits the data on up-link  111  employing the allotted resources during the prescribed time interval. 
         [0005]      FIG. 2  shows the Evolved Universal Terrestrial Radio Access (E-UTRA) time division duplex (TDD) Frame Structure. Different subframes are allocated for downlink (DL) or uplink (UL) transmissions. Table 1 shows applicable DL/UL subframe allocations. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Configu- 
                 Switch-point 
                 Subframe number 
               
             
          
           
               
                 ration 
                 periodicity 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 0 
                  5 ms 
                 D 
                 S 
                 U 
                 U 
                 U 
                 D 
                 S 
                 U 
                 U 
                 U 
               
               
                 1 
                  5 ms 
                 D 
                 S 
                 U 
                 U 
                 D 
                 D 
                 S 
                 U 
                 U 
                 D 
               
               
                 2 
                  5 ms 
                 D 
                 S 
                 U 
                 D 
                 D 
                 D 
                 S 
                 U 
                 D 
                 D 
               
               
                 3 
                 10 ms 
                 D 
                 S 
                 U 
                 U 
                 U 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 4 
                 10 ms 
                 D 
                 S 
                 U 
                 U 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 5 
                 10 ms 
                 D 
                 S 
                 U 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 6 
                 10 ms 
                 D 
                 S 
                 U 
                 U 
                 U 
                 D 
                 S 
                 U 
                 U 
                 D 
               
               
                   
               
             
          
         
       
     
         [0006]    One interesting property of TDD is that the number of UL and DL subframes can be different. In the configurations where there are more DL subframes than UL subframes, multiple DL subframes are associated with one single UL subframe for transmission of corresponding control signal. For example, for each dynamically scheduled transmission in the DL subframes, acknowledge and non-acknowledge (ACK/NAK) bits need to be transmitted in an associated UL subframe to support proper hybrid automatic repeat request (HARQ) operation. If UE  109  is scheduled in a multiple of DL subframes all of which are associated with one single UL subframe, UE  109  needs to transmit multiple ACK/NAK bits in that single UL subframe. 
       SUMMARY OF THE INVENTION 
       [0007]    This invention is a method of wireless communication having a communications protocol providing more downlink subframes than uplink subframes. The user equipment detects within a frame a plurality of downlink communications, producing either an acknowledge (ACK) response signal or a non-acknowledge (NAK) response signal for each detected downlink communication and transmits a combination of a plurality of ACK/NAK response signals and related data from the mobile user&#39;s equipment to a base station. 
         [0008]    The related data could be the number of bits N of the plurality of ACK/NAK response signals or the number of detected downlink communications S requiring ACK/NAK response signals. The plural ACK/NAK signals could be coded after production and before transmission. The coding could include block coding, convolutional coding and turbo coding. 
         [0009]    The user equipment could produce a cyclical redundancy check set of bits of the ACK/NAK signals for transmission. The cyclical redundancy check bits could be scrambled for transmission dependent upon the numbers N or S. As an example, an even number would use a first value for scrambling and an odd number would use a second value for scrambling. Similar selections are feasible with resource elements or an index of a modulation symbol or codeword. 
         [0010]    The N bits of the plurality of ACK/NAK response signals could be compressed into M bits where 0&lt;M&lt;N. In a preferred embodiment M is predetermined. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    These and other aspects of this invention are illustrated in the drawings, in which: 
           [0012]      FIG. 1  is a diagram of a communication system of the prior art related to this invention having three cells; 
           [0013]      FIG. 2  shows the Evolved Universal Terrestrial Radio Access (E-UTRA) TDD Frame Structure of the prior art; 
           [0014]      FIG. 3  is a flow chart of the basic response of this invention; 
           [0015]      FIG. 4  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0016]      FIG. 5  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0017]      FIG. 6  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0018]      FIG. 7  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0019]      FIG. 8  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0020]      FIG. 9  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0021]      FIG. 10  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0022]      FIG. 11  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0023]      FIG. 12  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0024]      FIG. 13  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0025]      FIG. 14  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0026]      FIG. 15  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0027]      FIG. 16  illustrates an alternate embodiment of block  304  of  FIG. 3 ; 
           [0028]      FIG. 17  illustrates an alternate embodiment of block  304  of  FIG. 3 ; and 
           [0029]      FIG. 18  illustrates an alternate embodiment of block  304  of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0030]      FIG. 3  illustrates a flow chart of the basic response of UE  109 . The process starts at start block  301 . In block  302  UE  109  detects plural down link transmissions requiring response. In block  303  UE  109  generates the ACK/NAK signal for the respective down link transmissions. In block  304  UE  109  transmits the ACK/NAK signals together with uplink payload data dependent upon the ACK/NAK signals. This basic response ends at end block  304 . 
         [0031]    This invention includes techniques for the transmission of multiple ACK/NAK bits with data. Typically, the transmission of multiple ACK/NAK bits and data occurs on a data channel such as physical uplink shared channel (PUSCH) in 3GPP long term evolution (LTE). The inventive techniques are mostly applicable to TDD systems where UE  109  may need to transmit multiple ACK/NAK bits with data in a subframe. It is also feasible to use the proposed techniques in frequency division duplex (FDD) systems where UE  109  needs to transmit multiple ACK/NAK bits with data in a subframe. 
         [0032]    Without loss of generality, assume N is the number of ACK/NAK bits UE  109  needs to transmit with data in a subframe. A straightforward approach is to encode the N ACK/NAK(s) with a coding scheme. These could be block codes, convolutional codes or turbo codes. Accordingly, block  304  includes this encoding. The encoded ACK/NAK bits are transmitted on the data channel preferably closely mapped to the reference signal to obtain better channel estimates. 
         [0033]    It is possible for UE  109  to miss one of the multiple DL grants. If this occurs less ACK/NAK bits are transmitted by UE  109  while base station  101  is expecting more ACK/NAK bits. This scenario is often called ACK/NAK DTX. In these cases UE  109  needs to provide additional information to base station  101  so that base station  101  can perform ACK/NAK DTX detection to enable proper HARQ operations. One solution is for UE  109  to explicitly transmit the information on the number of ACK/NAK bits it has in the data within a subframe. Thus UE  109  explicitly transmits N to base station  101 . It is preferable that the number N is separately coded from the actual information of the multiple ACK/NAK bits. Therefore, base station  101  can decode N first. This provides sufficient information to decode the N ACK/NAK bits subsequently. However, the number N and the actual ACK/NAK bits may be jointly coded. In this case, base station  101  may need to perform hypothesis testing since it has no prior information on the number of ACK/NAK bits UE  109  is transmitting. 
         [0034]      FIG. 4  illustrates an alternate block  304  according to this embodiment. In block  401  UE  109  determines the number of bits N of the plural ACK/NAK signals. In block  402  UE  109  transmits the plural ACK/NAK signals together with this number N. 
         [0035]    Without loss of generality, assume S is the number of DL grants UE  109  detects within the time frame where multiple DL subframes are associated with a common UL subframe. It is possible for UE  109  to explicitly convey the value S to base station  101 , to facilitate ACK/NAK DTX detection at base station  101 . 
         [0036]      FIG. 5  illustrates an alternate block  304  according to this embodiment. In block  501  UE  109  determines the number S of the plural ACK/NAK signals needed for response. In block  502  UE  109  transmits the plural ACK/NAK signals together with this number S. 
         [0037]    Cyclic redundancy check (CRC) bits can be appended to the coded or uncoded ACK/NAK bits. CRC provides additional information to the receiver or base station  101  on whether the ACK/NAK bits are decoded correctly. These CRC bits may be scrambled with the value N. Thus base station  101  can implicitly derive the number of ACK/NAK bits UE  109  is transmitting. In this case, there are N possible ways UE  109  can scramble the ACK/NAK CRC bits corresponding to the different values of N. Alternatively, assuming that UE  109  missing two or more DL grants within a certain time period is unlikely, it may be sufficient to scramble the CRC bits with mod(N, 2). Thus if UE  109  is transmitting an even number of ACK/NAK bits in a subframe, it scrambles the CRC bits with a value A. Otherwise, UE  109  scrambles the CRC bits with a value B. Base station  101  can check the CRC bits after descrambling with values of A and B to determine whether a correct number of ACK/NAK bits were transmitted by UE  109  to perform ACK/NAK DTX detection. 
         [0038]      FIG. 6  illustrates another embodiment of block  304  according to one of these options. In block  601  UE  109  determines the number of bits N of the plural ACK/NAK signals. In block  602  UE  109  calculates CRC bits corresponding to the ACK/NAK signals. In block  603  UE  109  scrambles the CRC bits and the number of bits N. In block  604  UE  109  transmits the ACK/NAK signals together with the scrambled CRC bits. 
         [0039]      FIG. 7  illustrates another embodiment of block  304  according to another of these options. In block  701  UE  109  determines the number of bits N of the plural ACK/NAK signals. In block  702  UE  109  calculates CRC bits corresponding to the ACK/NAK signals. In block  703  UE  109  determines if the number of bits N is even. If this number of bits is even (Yes at block  703 ), then in block  704  UE  109  scrambles the CRC bits with a first value A. If this number of bits is odd (No at block  703 ), then in block  705  UE  109  scrambles the CRC bits with a second value B. In block  706  UE  109  transmits the ACK/NAK signals together with the scrambled CRC bits. 
         [0040]    For single data stream transmission in all scheduled DL subframes N=S. For multiple data stream transmission: 
         [0000]    
       
         
           
             N 
             = 
             
               
                 ∑ 
                 
                   i 
                   = 
                   1 
                 
                 S 
               
                
               
                 d 
                  
                 
                   ( 
                   i 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where: d(i) is the number of data streams in the ith scheduled DL subframe. It is possible to scramble the CRC bits with the value S. Thus base station  101  can implicitly determine the number of detected DL grants by UE  109 . In this case, there are S possible ways UE  109  can scramble the ACK/NAK CRC bits corresponding to different values of S. Alternatively, assuming that UE  109  missing two or more DL grants within a certain time period is unlikely, it may be sufficient to scramble the CRC bits with mod(S, 2). If UE  109  detects an even number of DL grants, it scrambles the CRC bits with value A. Otherwise, UE  109  scrambles the CRC bits with value B. Base station  101  can check the CRC bits after descrambling with value A and B to determine whether a correct number of DL grants are detected by UE  109  to perform ACK/NAK DTX detection. 
         [0041]      FIG. 8  illustrates another embodiment of block  304  according to one of these options. In block  801  UE  109  determines the number S of the plural ACK/NAK signals needed for response. In block  802  UE  109  calculates CRC bits corresponding to the ACK/NAK signals. In block  803  UE  109  scrambles the CRC bits and the number S. In block  804  UE  109  transmits the ACK/NAK signals together with the scrambled CRC bits. 
         [0042]      FIG. 9  illustrates another embodiment of block  304  according to another of these options. In block  901  UE  109  determines the number S of the plural ACK/NAK signals needed for response. In block  902  UE  109  calculates CRC bits corresponding to the ACK/NAK signals. In block  903  UE  109  determines if the number S is even. If S is even (Yes at block  903 ), then in block  904  UE  109  scrambles the CRC bits with a first value A. If S is odd (No at block  903 ), then in block  905  UE  109  scrambles the CRC bits with a second value B. In block  906  UE  109  transmits the ACK/NAK signals together with the scrambled CRC bits. 
         [0043]    ACK/NAK bundling or compression is commonly employed to reduce the resources needed for the transmission of ACK/NAK bits. Thus N ACK/NAK bits are compressed into M ACK/NAK bits, where 0&lt;M&lt;N. The compressed M ACK/NAK bits are transmitted on the data channel with proper a coding scheme such as block codes, convolutional codes or turbo codes with an optional CRC attachment as previously described. The value of M can be predetermined and thus known at base station  101  to avoid unnecessary hypothesis testing. Base station  101  will not know N a prior since UE  109  may miss one or multiple DL grants. Such misses control the number of ACK/NAK bits UE  109  transmits. UE  109  may explicitly or implicitly signal the value of N to base station  101  to enable ACK/NAK DTX detection. UE  109  may explicitly or implicitly signal S to base station  101  to enable ACK/NAK DTX detection at base station  101 . 
         [0044]      FIG. 10  illustrates an alternate block  304  according to this embodiment. In block  1001  UE  109  compresses the of the plural ACK/NAK signals to M bits. In block  1002  UE  109  transmits the compressed ACK/NAK signals. 
         [0045]    As a further alternative UE  109  may implicitly signal the number of ACK/NAK bits N or the number of detected DL grants S to base station  101  by the positions of resource elements (REs) used for ACK/NAK transmission. A resource element is a time-frequency resource. UE  109  can choose different REs for the transmission of ACK/NAK bits. Base station  101  needs to perform hypothesis testing on all possible RE locations where ACK/NAK bits can be transmitted to determine N or S. Suppose two RE regions are defined for ACK/NAK transmission. If the number of ACK/NAK bits or the number of detected DL grants is even, then a first RE region is used for ACK/NAK transmission. Otherwise a second RE region is used for ACK/NAK transmission. More than two RE regions can be defined to implicitly convey partial information on N or S. This RE region dependent ACK/NAK transmission can be applied in conjunction with ACK/NAK bundling or compression. The compressed M ACK/NAK bits are transmitted on the selected ACK/NAK RE region which is dependent on the value of N or S. 
         [0046]      FIG. 11  illustrates another embodiment of block  304  according to one of these options. In block  1101  UE  109  determines the number of bits N of the plural ACK/NAK signals. In block  1102  UE  109  selects one of a plurality of possible resource elements according to the number of bits N. In block  1103  UE  109  transmits the ACK/NAK signals using the selected resource element. 
         [0047]      FIG. 12  illustrates another embodiment of block  304  according to another of these options. In block  1201  UE  109  determines the number of bits N of the plural ACK/NAK signals. In block  1202  UE  109  determines if the number of bits N is even. If this number of bits is even (Yes at block  1202 ), then in block  1203  UE  109  selects a first resource element A. If this number of bits is odd (No at block  1202 ), then in block  1204  UE  109  selects a second resource element B. In block  1205  UE  109  transmits the ACK/NAK signals using the selected resource element. 
         [0048]      FIG. 13  illustrates another embodiment of block  304  according to another of these options. In block  1301  UE  109  determines the number S of the plural ACK/NAK signals needed for response. In block  1302  UE  109  selects one of a plurality of possible resource elements according to the number S. In block  1303  UE  109  transmits the ACK/NAK signals using the selected resource element. 
         [0049]      FIG. 14  illustrates another embodiment of block  304  according to another of these options. In block  1401  UE  109  determines the number S of the plural ACK/NAK signals needed for response. In block  1402  UE  109  determines if the number S is even. If S is even (Yes at block  1402 ), then in block  1403  UE  109  selects a first resource element A. If S is odd (No at block  1402 ), then in block  1404  UE  109  selects a second resource element B. In block  1405  UE  109  transmits the ACK/NAK signals using the selected resource element. 
         [0050]    In a yet further alternative UE  109  may implicitly signal the number of ACK/NAK bits N or the number of detected DL grants S to base station  101  by the index of the set of modulation symbols or codewords it is currently using for the transmission of ACK/NAK bits. The possible modulation symbols or codewords can be divided into two sets denoted S 1  and S 2 . If a modulation symbol or a codeword in set S 1  is used, base station  101  determines that an even number of ACK/NAK bits were transmitted by UE  109  or an even number of DL grants were detected by UE  109 . Otherwise base station  101  determines that an odd number of ACK/NAK were transmitted or an odd number of DL grants were detected. More than two sets of modulation symbols or codewords could be defined for implicit transmission of partial information of N or S values. This set dependent ACK/NAK transmission can be applied in conjunction with ACK/NAK bundling or compression. One modulation symbol or codeword within the selected set could be chosen and transmitted to convey the compressed M ACK/NAK bits. 
         [0051]    The proposed RE region dependent ACK/NAK transmission could be applied together with the modulation symbol or codeword set dependent ACK/NAK transmission and ACK/NAK bundling or compression. The transmission of multiple ACK/NAK bits could be applied for ACK/NAK transmission without any data transmission. The transmission of multiple ACK/NAK bits could be employed in either TDD or FDD systems. 
         [0052]      FIG. 15  illustrates another embodiment of block  304  according to one of these options. In block  1501  UE  109  determines the number of bits N of the plural ACK/NAK signals. In block  1502  UE  109  selects one of a plurality of possible indices according to the number of bits N. In block  1503  UE  109  transmits the ACK/NAK signals using the selected index. 
         [0053]      FIG. 16  illustrates another embodiment of block  304  according to another of these options. In block  1601  UE  109  determines the number of bits N of the plural ACK/NAK signals. In block  1602  UE  109  determines if the number of bits N is even. If this number of bits is even (Yes at block  1602 ), then in block  1603  UE  109  selects a first index S 1 . If this number of bits is odd (No at block  1602 ), then in block  1604  UE  109  selects a second index S 2 . In block  1505  UE  109  transmits the ACK/NAK signals using the selected index. 
         [0054]      FIG. 17  illustrates another embodiment of block  304  according to another of these options. In block  1701  UE  109  determines the number S of the plural ACK/NAK signals needed for response. In block  1702  UE  109  selects one of a plurality of possible indices according to the number S. In block  1703  UE  109  transmits the ACK/NAK signals using the selected index. 
         [0055]      FIG. 18  illustrates another embodiment of block  304  according to another of these options. In block  1801  UE  109  determines the number S of the plural ACK/NAK signals needed for response. In block  1802  UE  109  determines if the number S is even. If S is even (Yes at block  1802 ), then in block  1803  UE  109  selects a first index S 1 . If S is odd (No at block  1802 ), then in block  1804  UE  109  selects a second index S 2 . In block  1805  UE  109  transmits the ACK/NAK signals using the selected index. 
         [0056]    Assume for a certain bundling window of size there are T DL subframes associated with one UL subframe. The maximum number of ACK/NAK bits UE  109  may have within the bundling window is 2T. This is because there could be two DL data streams per DL subframe with multiple input multiple output (MIMO) operation. Alternatively UE  109  may be scheduled on a subset of the T DL subframes. For explicit transmission of multiple ACK/NAK bits on PUSCH, UE  109  needs to identify for which subset of DL subframes it detects DL grants. In one possible technique UE  109  always transmit 2T ACK/NAK bits on PUSCH with 2 bits reserved for each DL subframe in the bundling window. For the DL subframes that UE  109  does not detect any DL grant, then NAK or (NAK, NAK) is transmitted as the ACK/NAK bits for the corresponding DL subframes. UE  109  may reserve 1 bit per DL subframe. Thus UE  109  always transmits T ACK/NAK bits on PUSCH, one for each DL subframe. For the DL subframes in which UE  109  does not detect any DL subframe, then NAK is transmitted as the ACK/NAK bit for the corresponding DL subframes. When UE  109  has DL MIMO operation, then the multiple ACK/NAK bits are bundled or compressed into a single ACK/NAK bit per DL subframe by a logical AND operation. These multiple ACK/NAK bits such as 2T or T ACK/NAK bits can be jointly or separately coded, and transmitted on PUSCH.