Patent Publication Number: US-8989123-B2

Title: Transmission diversity scheme on physical uplink control channel (PUCCH) with ACK/NACK differentiation

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/573,016 entitled “Transmission Diversity Scheme on Physical Uplink Control Channel (PUCCH) with ACK/NACK Differentiation,” filed Oct. 2, 2009, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to wireless communications and wireless communications-related technology. More specifically, the present invention relates to a transmission diversity scheme on the physical uplink control channel (PUCCH) with ACK/NACK differentiation. 
     BACKGROUND 
     Wireless communication devices have become smaller and more powerful in order to meet consumer needs and to improve portability and convenience. Consumers have become dependent upon wireless communication devices and have come to expect reliable service, expanded areas of coverage, and increased functionality. A wireless communication system may provide communication for a number of cells, each of which may be serviced by a base station. A base station may be a fixed station that communicates with mobile stations. 
     Various signal processing techniques may be used in wireless communication systems to improve efficiency and quality of wireless communication. One such technique may include using multiple antennas for multiple-input and multiple-output (MIMO) or transmit diversity (TxD). Additional gains may be realized within these channels. Benefits may be realized by providing gains within these control channels while maintaining or increasing reliability and sustaining compatibility with older equipment. Therefore, benefits may be realized by improved coding techniques. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a wireless communication system with a wireless communication device and a base station; 
         FIG. 2  is a block diagram illustrating the transmission of a message from a wireless communication device to a base station via the physical uplink control channel (PUCCH); 
         FIG. 3  is a flow diagram of a method for transmitting uplink control information (UCI) using a physical uplink control channel (PUCCH) transmit diversity scheme; 
         FIG. 4  is a block diagram illustrating data flows for transmitting uplink control information (UCI) using a format 2 PUCCH transmit diversity scheme; 
         FIG. 5  is a flow diagram of a method for transmitting uplink control information (UCI) using a format 2 PUCCH transmit diversity scheme; 
         FIG. 6  is a block diagram illustrating data flows for transmitting uplink control information (UCI) using a format 2a/2b PUCCH transmit diversity scheme; 
         FIG. 7  is a flow diagram of a method for transmitting uplink control information (UCI) using a format 2a/2b PUCCH transmit diversity scheme; 
         FIG. 8  is a flow diagram illustrating a method for receiving uplink control information (UCI) using a PUCCH transmit diversity scheme; 
         FIG. 9  is a block diagram illustrating data flows for receiving uplink control information (UCI) using a format 2 PUCCH transmit diversity scheme; 
         FIG. 10  is a flow diagram of a method for receiving uplink control information (UCI) using a format 2 PUCCH transmit diversity scheme; 
         FIG. 11  is a block diagram illustrating data flows for receiving uplink control information (UCI) using a format 2a/2b PUCCH transmit diversity scheme; 
         FIG. 12  is a flow diagram of a method for receiving uplink control information (UCI) using a format 2a/2b PUCCH transmit diversity scheme; 
         FIG. 13  illustrates various components that may be utilized in a wireless communication device; and 
         FIG. 14  illustrates various components that may be utilized in a base station. 
     
    
    
     DETAILED DESCRIPTION 
     A method for transmitting uplink control information (UCI) using a physical uplink control channel (PUCCH) transmit diversity scheme is described. A UCI is coded with a Forward Error Correction code such as a Reed-Muller code to obtain a coded UCI. The coded UCI is mapped to quadrature phase shift keying (QPSK) symbols to obtain a mapped coded UCI. A phase shift is applied to the mapped coded UCI based on an acknowledge/negative-acknowledge (ACK/NACK) to obtain a phase shifted mapped coded UCI. The mapped coded UCI is sent using a PUCCH resource on a first antenna. The phase shifted mapped coded UCI is sent using a PUCCH resource on a second antenna. 
     The UCI may include a channel quality indicator (CQI), a precoding matrix index (PMI) and the ACK/NACK. The CQI, PMI and ACK/NACK may be concatenated to obtain a concatenated UCI. Coding the UCI with a Forward Error Correction code, such as a Reed-Muller code may include joint coding the concatenated UCI. The ACK/NACK may be coded on reference symbols of the PUCCH resource of the first antenna to obtain a first set of ACK/NACK coded reference symbols. The first set of ACK/NACK coded reference symbols may be combined with the mapped coded UCI prior to sending the mapped coded UCI. 
     The ACK/NACK may be coded on reference symbols of the PUCCH resource of the second antenna to obtain a second set of ACK/NACK coded reference symbols. The second set of ACK/NACK coded reference symbols may be combined with the phase shifted mapped coded UCI prior to sending the phase shifted mapped coded UCI. The coded UCI may be twenty bits. The coded UCI may be mapped to ten QPSK symbols. The method may be performed by a wireless communication device. The wireless communication device may be configured to operate using a single or multiple antennas. The UCI may be transmitted using PUCCH format 2. The UCI may also be transmitted using PUCCH format 2a/2b. 
     A method for receiving uplink control information (UCI) using a physical uplink control channel (PUCCH) transmit diversity scheme is described. A first set of symbols is received by a first signal receiver for a first PUCCH transmission. A second set of symbols is received by a second signal receiver for a second PUCCH transmission. A first acknowledge/negative-acknowledge (ACK/NACK) estimate is estimated. A phase shift is removed from the second set of symbols based on the first ACK/NACK estimate to obtain a third set of symbols. The first set of symbols is combined with the third set of symbols to obtain a fourth set of symbols. The fourth set of symbols is decoded to obtain the UCI. 
     A differential phase shift between the first set of symbols and the second set of symbols may be computed. The first ACK/NACK estimate may be based on the differential phase shift. A second ACK/NACK estimate may be extracted from one or more reference symbols in the first set of symbols and the second set of symbols. A third ACK/NACK estimate may be a combination of the first ACK/NACK estimate and the second ACK/NACK estimate. The method may be performed by a base station configured to operate using a single or multiple antennas. Decoding may be performed using a Reed-Muller decoder, in the case where a Reed-Muller code was used to encode the UCI. The UCI may be sent using PUCCH format 2a/2b as per 3GPP TS 36.211. 
     A method for receiving uplink control information (UCI) using a physical uplink control channel (PUCCH) transmit diversity scheme is disclosed. A first set of symbols is received by a first signal receiver for a first PUCCH transmission. A second set of symbols is received by a second signal receiver for a second PUCCH transmission. A differential phase shift between the first set of symbols and the second set of symbols is computed. A first acknowledge/negative-acknowledge (ACK/NACK) estimate is estimated based on the differential phase shift. A phase shift is removed from the second set of symbols based on the first ACK/NACK estimate to obtain a third set of symbols. The first set of symbols is combined with the third set of symbols to obtain a fourth set of symbols. The fourth set of symbols is decoded to obtain a first UCI that includes a joint decoded ACK/NACK estimate. 
     It may be determined whether the first ACK/NACK estimate and the joint decoded ACK/NACK estimate differ by less than a threshold. The joint decoded ACK/NACK estimate may be selected as the ACK/NACK if the first ACK/NACK estimate and the joint decoded ACK/NACK estimate differ by less than a threshold. The first set of symbols may be decoded to obtain a second ACK/NACK estimate if the first ACK/NACK estimate and the joint decoded ACK/NACK estimate differ by more than a threshold. 
     The first ACK/NACK estimate and the second ACK/NACK estimate may be combined to obtain a third ACK/NACK estimate. A phase shift may be removed from the second set of symbols based on the third ACK/NACK estimate to obtain a fifth set of symbols. The fifth set of symbols may be combined with the first set of symbols to obtain a sixth set of symbols. The sixth set of symbols may be decoded to obtain a second UCI that includes a joint decoded fourth ACK/NACK estimate. It may be determined whether the third ACK/NACK estimate and the joint decoded fourth ACK/NACK estimate differ by less than a threshold. The joint decoded ACK/NACK estimate may be selected as the ACK/NACK if the third ACK/NACK estimate and the joint decoded fourth ACK/NACK estimate differ by less than a threshold. A fifth ACK/NACK estimate may be determined based on the first ACK/NACK estimate if the third ACK/NACK estimate and the joint decoded fourth ACK/NACK estimate differ by more than a threshold. 
     A phase shift may be removed from the second set of symbols based on the fifth ACK/NACK estimate to obtain a seventh set of symbols. The seventh set of symbols may be combined with the first set of symbols to obtain an eighth set of symbols. The eighth set of symbols may be decoded to obtain a third UCI that includes a joint decoded sixth ACK/NACK estimate. It may be determined whether the fifth ACK/NACK estimate and the joint decoded sixth ACK/NACK estimate differ by less than a threshold. The joint decoded sixth ACK/NACK estimate may be selected as the ACK/NACK if the fifth ACK/NACK estimate and the joint decoded sixth ACK/NACK estimate differ by less than a threshold. The ACK/NACK may be determined based on the number of bits in the third UCI if the fifth ACK/NACK estimate and the joint decoded sixth ACK/NACK estimate differ by more than a threshold. 
     The method may be performed by a base station configured to operate using a single or multiple antennas. Decoding may be performed using a Reed-Muller decoder for cases where a Reed-Muller code was used to encode the UCI. The UCI may be sent using PUCCH format 2 as per 3GPP TS 36.211. 
     A wireless communication device configured for transmitting uplink control information (UCI) using a physical uplink control channel (PUCCH) transmit diversity scheme is described. The wireless communication device includes a Reed-Muller encoder, a quadrature phase shift keying (QPSK) symbol mapper, a phase shifter, a first antenna, and a second antenna. 
     The Reed-Muller encoder may joint code a channel quality indicator (CQI)/precoding matrix index (PMI) and an acknowledge/negative-acknowledge (ACK/NACK). The wireless communication device may also include a first ACK/NACK reference symbol coder and a second ACK/NACK reference symbol coder. An ACK/NACK reference symbol coder may code an ACK/NACK onto one or more reference symbols of a slot. The phase shifter may apply a phase shift based on the ACK/NACK. The wireless communication device may be configured to operate using single or multiple antennas. The UCI may be transmitted using PUCCH format 2. The UCI may be transmitted using PUCCH format 2a/2b. 
     A base station configured for receiving uplink control information (UCI) using a physical uplink control channel (PUCCH) transmit diversity scheme is also described. The base station includes a first signal receiver for a first PUCCH transmission that receives a first set of symbols. The base station also includes a second signal receiver for a second PUCCH transmission that receives a second set of symbols. The base station further includes a differential phase shift computer that computes the differential phase shift between the first set of symbols and the second set of symbols. The base station also includes a phase shift estimation module that estimates a first acknowledge/negative-acknowledge (ACK/NACK) estimate based on the differential phase shift. The base station further includes a phase shift removal module that removes a phase shift from the second set of symbols to obtain a third set of symbols. The base station also includes a first combiner that combines the first set of symbols and the third set of symbols to obtain a fourth set of symbols. The base station also includes a first decoder that decodes the fourth set of symbols to obtain the UCI. 
     The base station may also include an ACK/NACK extraction module that extracts a second ACK/NACK estimate from one or more reference symbols of the first set of symbols and the second set of symbols. The base station may further include a second combiner that combines the first ACK/NACK estimate and the second ACK/NACK estimate to obtain a third ACK/NACK estimate. The phase shift removed from the second set of symbols may be based on the third ACK/NACK estimate. 
     The base station may include a second decoder that decodes a second ACK/NACK estimate from the first set of symbols. The base station may also include a second combiner that combines the first ACK/NACK estimate and the second ACK/NACK estimate to obtain a third ACK/NACK estimate. The UCI output by the first decoder may include a channel quality indicator (CQI), a precoding matrix index (PMI) and a fourth ACK/NACK estimate. The base station may further include a validation module that determines the validity of the fourth ACK/NACK estimate. 
       FIG. 1  is a block diagram illustrating a wireless communication system  100  with a wireless communication device  104  and a base station  102 . A base station  102  may be in wireless communication with one or more wireless communication devices  104 . A base station  102  may be referred to as an access point, a Node B, an eNodeB, or some other terminology. Likewise, a wireless communication device  104  may be referred to as a mobile station, a subscriber station, an access terminal, a remote station, a user terminal, a terminal, a handset, a subscriber unit, user equipment, or some other terminology. The wireless communication device may transmit data to the base station over a radio frequency (RF) communication channel. 
     A wireless communication device  104  may communicate with zero, one or multiple base stations  102  on the downlink and/or uplink  112  at any given moment. The downlink refers to the communication link from a base station  102  to a wireless communication device  104 . The uplink  112  refers to the communication link from a wireless communication device  104  to a base station  102 . 
     Communication between a wireless communication device  104  and a base station  102  may be accomplished using transmissions over a wireless link including an uplink  112  and a downlink. The communication link may be established using a single-input and single-output (SISO), multiple-input and single-output (MISO) or a multiple-input and multiple-output (MIMO) system. A MIMO system may include both a transmitter and a receiver equipped with multiple transmit and receive antennas. A MIMO system may provide improved performance if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. 
     The use of multiple antennas  110   a - b  on the wireless communication device  104  may allow transmit diversity on the uplink  112 . In transmit diversity, signals originating from the two or more independent sources that have been modulated with identical information-bearing signals may be used. Transmit diversity may help overcome the effects of fading, outages, and circuit failures. 
     In 3 rd  Generation Partnership Project (3GPP) Long Term Evolution (LTE)—Advanced, additional control feedback will have to be sent on control channels to accommodate MIMO and carrier aggregation (CA). Carrier aggregation refers to transmitting data on multiple sub-bands which are contiguously located. Both the acknowledge/negative-acknowledge (ACK/NACK) bits and other control information may be transmitted using the PUCCH. A transmit diversity format for the PUCCH may significantly enhance the ACK/NACK performance while maintaining the diversity gain on other uplink control information (UCI). The other UCI may include the channel quality indicator (CQI) and the precoding matrix index (PMI). In other words, by using a transmit diversity format for the PUCCH, the reliability of the transmission of the ACK/NACK bits on the uplink may be improved while maintaining the reliability of the transmission of other control information on the uplink. 
     In current LTE release-8 specifications, only one antenna is used. With LTE-Advanced, a wireless communication device  104  may have multiple antennas  110 . Typically, a wireless communication device  104  may use two or four antennas  110 , although other quantities of antennas  110  may be used. Transmit diversity schemes with multiple antennas  110  are being considered and are in the discussion phase. 
     Transmit diversity methods are studied separately for PUCCH and PUSCH. In the recent 3GPP meetings, it was agreed that for PUCCH, uplink single antenna port mode should be supported even with multiple antennas  110 . It was also agreed that spatial orthogonal resource transmit diversity (SORTD) may be applied for a multiple resource PUCCH. The PUCCH may use one of six formats for transmission: format 1/1a/1b or format 2/2a/2b. For format 1/1a/1b, it was agreed that the same modulated symbols are transmitted on different orthogonal resources for different antennas  110 . The PUCCH formats 2/2a/2b were left for future study. With SORTD, separate orthogonal resources may be allocated for the PUCCH. The structure of the PUCCH of each resource should be the same as release 8 to ensure backward compatibility. The PUCCH transmit diversity scheme may introduce another level of protection for ACK/NACK bits when transmit diversity is used. 
     Solutions for using the formats 2/2a/2b include simple repetition and joint coding. In simple repetition, a wireless communication device  104  may transmit the same modulated symbols on different orthogonal resources for different antennas  110 . Simple repetition has backward compatibility and is consistent with formats 1/1a/1b. In joint coding, a longer sequence of codewords is used and part of the codeword is transmitted on each antenna  110 . Joint coding achieves a coding gain but no diversity gain. Moreover, joint coding loses the backward compatibility of single antenna transmission. Joint coding is also vulnerable to antenna gain imbalance (AGI). 
     Existing transmit diversity proposals assume the same coding method for all uplink channel information (UCI) including ACK/NACK, channel quality indicator (CQI) and precoding matrix index (PMI). However, ACK/NACK requires a higher error protection than other information bits (such as CQI and PMI) during system operation. By using a combination of simple repetition and joint coding, the backward compatibility may be retained while introducing an enhancement on the more important messages such as ACK/NACK. 
     The target PUCCH performance qualities are given in Table 1 below according to 3GPP TS 36.300. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Event 
                 Target Quality 
               
               
                   
                   
               
             
            
               
                   
                 ACK miss detection (for DL-SCH) 
                 (10 −2 ) 
               
               
                   
                 DTX to ACK error (for DL-SCH) 
                 (10 −2 -10 −1 ) 
               
               
                   
                 NACK to ACK error (for DL-SCH) 
                 (10 −4 -10 −3 ) 
               
               
                   
                 CQI block error rate 
                 FFS (10 −2 -10 −1 ) 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 1, the ACK/NACK in general requires a higher reliability than the CQI. This is because the CQI is concerned with the block error rate and the ACK/NACK is concerned with the bit error rate. The NACK to ACK error should have better protection than the ACK to NACK miss detection. 
     The existing PUCCH formats cannot fully satisfy these requirements. Because ACK/NACK bits are treated equally, the NACK to ACK and ACK to NACK performances are also the same. Furthermore, with the existing schemes, the ACK/NACK performance is not sufficient. The use of carrier aggregation (CA) in LTE-A may require ACK/NACK bundling in PUCCH feedback. Thus, improvements in ACK/NACK performance may be desirable. 
     The current Release 8 PUCCH formats may not provide enough protection on the ACK/NACK. The existing PUCCH formats may be especially unable to achieve the NACK to ACK error probability. In PUCCH transmit diversity design, the unequal error protection for different types of control feedback may be considered. It is desirable to find new formats that can further differentiate the performance of ACK/NACK from other control bits, such as the CQI and the PMI. 
     In format 2, the ACK/NACK and the CQI/PMI are jointly coded. Thus, the ACK/NACK and the CQI/PMI have the same bit error rate (BER) performance. As the number of control bits increases, the ACK/NACK and CQI/PMI performance may degrade. Thus, the ACK/NACK may not get enough protection compared to the CQI/PMI. Also, the ACK/NACK performance degrades with the increase of CQI/PMI bits. 
     With normal cyclic prefix (CP) in format 2a and 2b, the ACK/NACK bits are transmitted on the four reference symbols with differential binary phase-shift keying (BPSK) and differential quadrature phase-shift keying (QPSK) respectively, i.e. the ACK/NACK bits are coded on the second reference symbol by a differential phase shift over the first reference symbol. Thus, the ACK/NACK is independent of other control bits with a simple 2× (two times) differential coding repetition redundancy. The CQI/PMI bits are coded independently to twenty bits. Thus, the CQI/PMI may have a Reed-Muller (RM) code gain with a coding rate between 1/5 and 11/20. Differential coding may have worse performance when compared with non-differential coding, e.g. QPSK performance is ˜3 dB worse than normal QPSK. Therefore, with format 2a/2b, the ACK/NACK performance may be worse than the CQI in most cases. 
     The wireless communication device  104  may send uplink  112  transmissions using either two antennas  110  or four antennas  110 . When four antennas  110  are used by the wireless communication device  104 , the four antennas  110  may be formed into two virtual antennas. Then, the same scheme used by two antennas  110  may be used by the two virtual antennas. The base station  102  may receive the uplink  112  transmissions using multiple antennas, e.g. two antennas  114   a - b , four antennas or eight antennas. 
     The wireless communication device  104  may include an uplink transmit (Tx) diversity transmission module  108 . The uplink transmit (Tx) diversity transmission module  108  may facilitate the transmission of uplink control information (UCI) from the wireless communication device  104  on the uplink  112  using multiple antennas  110 . For example, the uplink transmit (Tx) diversity transmission module  108  may select the format of the uplink  112  transmissions and apply format specific coding/mapping. The base station  102  may include an uplink transmit (Tx) diversity receiving module  106 . The uplink transmit (Tx) diversity receiving module  106  may facilitate the receiving of UCI on the uplink  112  using multiple antennas  114 . For example, the uplink transmit (Tx) diversity receiving module  106  may determine the format of a received UCI on the uplink  112  and apply techniques to improve performance of the uplink  112  transmission. 
     By differentiating the ACK/NACK from other control information, the bit error rate of ACK/NACK bits may be reduced. Thus, packet loss due to miss detection of NACK to ACK may be prevented. Furthermore, unnecessary retransmission from miss detection of ACK to NACK may be reduced. The full diversity gain of repetition on different antennas with SORTD may be maintained with negligible impact from ACK/NACK residue. 
       FIG. 2  is a block diagram illustrating the transmission of a message  218  from a wireless communication device  204  to a base station  202  via the physical uplink control channel (PUCCH)  216 . The wireless communication device  204  of  FIG. 2  may be one configuration of the wireless communication device  104  of  FIG. 1 . Likewise, the base station  202  of  FIG. 2  may be one configuration of the base station  102  of  FIG. 1 . The wireless communication device  204  may transmit the message  218  via the physical uplink control channel (PUCCH)  216  to the base station  202 . 
     The message  218  may include uplink control information (UCI)  222 . The UCI  222  may include a channel quality indicator (CQI)  224   a  and/or a precoding matrix index (PMI)  224   b . The message  218  may also include ACK/NACK  228  information. The message  218  may further include a format  220  for which the message was transmitted. For example, the message  218  may be transmitted using format 1/1a/1b or format 2/2a/2b. 
     In Release 8, the formats  220  and coding for the PUCCH  216  are defined as illustrated in Table 2. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Number of bits 
                   
                   
               
               
                   
                 Modulation 
                 per subframe, 
                 CQI/PMI 
                 ACK/ 
               
               
                 PUCCH format 
                 scheme 
                 M bit   
                 etc. 
                 NACK 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 1 
                 N/A 
                 N/A 
                 N/A 
                 1 
               
               
                 1a 
                 BPSK 
                 1 
                 N/A 
                 1 
               
               
                 1b 
                 QPSK 
                 2 
                 N/A 
                 2 
               
               
                 2 
                 QPSK 
                 20 
                 4-11 
                 0-2 
               
               
                 2a 
                 QPSK + BPSK 
                 21 
                 4-11 
                 1-2 
               
               
                 2b 
                 QPSK + QPSK 
                 22 
                 4-11 
                 1-2 
               
               
                   
               
            
           
         
       
     
     Release 8 supports only single antenna transmission on the uplink. For format 1, information is carried by the presence/absence of the transmission of the PUCCH  216  from the wireless communication device  204 . For format 1a and 1b, one or two explicit bits are transmitted with binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) modulation respectively. 
     For format 2, the uplink control information (UCI)  222  such as the channel quality indicator (CQI)  224   a  and the precoding matrix index (PMI)  224   b  along with the ACK/NACK  228  may be concatenated and joint coded with a Forward Error Correction (FEC) code such as a Reed-Muller (RM) (20, O) code to twenty bits. With extended cyclic prefix (CP), only format 2 may be used. Formats 2a and 2b are the default formats for normal CP. With format 2a/2b, the UCI  222  may be coded with an RM code to twenty bits and transmitted on PUCCH  216  symbols while the ACK/NACK  228  bits may be coded and transmitted on the PUCCH  216  reference symbols (RS). 
     A PUCCH resource is allocated within a subframe, which consists of two slots. With normal CP, each slot has seven symbols. Two of the symbols are used as reference symbols and five are used for the PUCCH  216  message. Thus, with normal CP, the PUCCH  216  has ten message carrying symbols and four reference symbols. With format 2a/2b, four reference symbols may be used for the ACK/NACK  228  and the other ten symbols may be used for the other UCI  222 . The ACK/NACK  228  may be coded with a differential phase-shift coded on the second reference symbol with the first reference symbol as a phase reference. 
     With extended CP, each slot has six symbols. One of the symbols may be used as a reference symbol and the five other symbols may be used for the PUCCH  216  message. Thus, the PUCCH  216  has ten message carrying symbols and two reference symbols. Because there is only one reference symbol in each slot, ACK/NACK coding is not possible with extended CP. Therefore, with format 2, the ACK/NACK  228  may be joint coded with the other UCI  222  (such as the CQI  224   a  and the PMI  224   b ) and transmitted in the ten message carrying symbols. The block of complex-valued symbols z(i) may be multiplied with the amplitude scaling factor β PUCCH  in order to conform to the transmit power. The block of complex-valued symbols may then be mapped in sequence starting with z(0) to the resource elements. 
     A wireless communication device  204  with multiple transmit antennas  110  may be required to behave as wireless communication devices with a single antenna port from a base station&#39;s  202  perspective in Uplink Single Antenna Port Mode. The PUCCH  216 , PUSCH or SRS transmission may be configured to enter Uplink Single Antenna Port Mode. Alternatively, the wireless communication device  204  may enter the Uplink Single Antenna Port Mode without instruction from the base station  202  in some scenarios. 
     SORTD may be the baseline for a PUCCH  216  transmit diversity scheme. Multiple resources may be allocated for each antenna  110  when there are two transmit antennas  110 . The virtual antenna concept may be used for scenarios where there are four transmit antennas  110 . Backward compatibility is important in PUCCH  216  transmit diversity design. The two options with SORTD are simple repetition and joint coding. In simple repetition, the same coded information may be transmitted on the second antenna  110   b  as on the first antenna  110   a . Simple repetition has diversity gain but no coding gain (or it could be viewed as repetition coding gain). In joint coding, a higher redundancy code may be used, and half of the codeword may be transmitted on each channel. Joint coding has coding gain but no diversity gain. Joint coding supports a larger payload but has no backward compatibility. The splitting of a codeword makes joint coding vulnerable to AGI. 
       FIG. 3  is a flow diagram of a method  300  for transmitting uplink control information (UCI)  222  using a physical uplink control channel (PUCCH)  216  transmit diversity scheme. The method  300  may be performed by a wireless communication device  104 . The method  300  of  FIG. 3  may apply to a PUCCH message  218  using format 2, format 2a or format 2b. In one configuration, the wireless communication device  104  may be a UE. The UCI  222  may be part of a PUCCH message  218 . In one configuration, the UCI  222  may include a CQI  224   a , a PMI  224   b  and an ACK/NACK  228 . The wireless communication device  104  may code  302  a UCI  222  with a Forward Error Correction (FEC) code such as a Reed-Muller code to twenty bits. The wireless communication device  104  may then map  304  the coded UCI  222  to ten QPSK symbols. Alternatively, the wireless communication device  104  may map  304  the coded UCI  222  to a different number of QPSK symbols. 
     The wireless communication device  104  may apply  306  a phase shift to the mapped coded UCI  224   a  based on an ACK/NACK  228 . The phase shift applied may depend on the format  220  of the PUCCH message  218 . The phase shifts applied to the mapped coded UCI  222  for format 2 PUCCH messages  218  with transmit diversity are shown in Table 3. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                 Joint coded control bits  
                 Phase shift on 2 nd   
               
               
                 PUCCH 
                   
                 (CQI + A/N) on 1 st  antenna 
                 antenna for 
               
               
                 format 
                 ACK/NACK bits 
                 b(0) , . . . , b(19) 
                 b(0), . . . , b(19) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 2 
                 0 
                 Same as Release-8 
                 0 
               
               
                   
                 1 
                 Same as Release-8 
                 π 
               
               
                   
                 00 
                 Same as Release-8 
                 0 
               
               
                   
                 01 
                 Same as Release-8 
                 −π/2   
               
               
                   
                 10 
                 Same as Release-8 
                 π/2 
               
               
                   
                 11 
                 Same as Release-8 
                 π 
               
               
                   
               
            
           
         
       
     
     The joint coded control bits on the first antenna  110   a  are the same as those used in LTE Release 8. The phase shifts applied to the mapped coded UCI  222  for format 2a/2b PUCCH messages  218  with transmit diversity are shown in Table 4. No phase shift coding is applied on the reference symbols between the two PUCCH transmissions. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                 ACK/NACK bits 
                 Coded control bits 
                   
               
               
                   
                 on reference 
                 (CQI/PMI) 
                 Phase shift on 2 nd   
               
               
                 PUCCH 
                 symbols 
                 b(0), . . . , b(19) 
                 antenna for 
               
               
                 format 
                 b(20), . . . , b(M bit  − 1) 
                 on 1 st  antenna 
                 b(0), . . . , b(19) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 2a 
                 0 
                 Same as Release-8 
                 0 
               
               
                   
                 1 
                 Same as Release-8 
                 π 
               
               
                 2b 
                 00 
                 Same as Release-8 
                 0 
               
               
                   
                 01 
                 Same as Release-8 
                 −π/2   
               
               
                   
                 10 
                 Same as Release-8 
                 π/2 
               
               
                   
                 11 
                 Same as Release-8 
                 π 
               
               
                   
               
            
           
         
       
     
     The wireless communication device  104  may then send  308  the mapped coded UCI  224   a  and reference symbols using a PUCCH resource on a first antenna  110   a . The wireless communication device  104  may send  310  the phase shifted mapped coded UCI  222  and reference symbols using a PUCCH resource on a second antenna  110   b . The wireless communication device  104  may send  310  the phase shifted mapped coded UCI  222  and reference symbols using the PUCCH resource on the second antenna  110   b  while concurrently sending  308  the mapped coded UCI  222  and reference symbols using the PUCCH resource on the first antenna  110   a . The ACK/NACK may be coded on the reference symbols in the same manner as in release -8 and no phase shift coding is applied on the reference symbols between the two PUCCH transmissions. 
       FIG. 4  is a block diagram illustrating data flows for transmitting uplink control information (UCI)  218  using a format 2 PUCCH transmit diversity scheme. A wireless communication device  404  may include an uplink transmit (Tx) diversity transmission module  408 . The uplink transmit (Tx) diversity transmission module  408  may include uplink control information (UCI) to be transmitted to a base station  102  via the PUCCH  216 . For example, the uplink transmit (Tx) diversity transmission module  408  may include a CQI/PMI  424  and an ACK/NACK  428 . A Forward Error Correction (FEC) coder such as a Reed-Muller (20, O) joint coder  430  may code a concatenation of the CQI/PMI  424  and the ACK/NACK  428  to twenty bits. The coder  430  may output a joint coded concatenated UCI  421 . The joint coded concatenated UCI  421  may then be mapped to ten QPSK symbols by a mapper  432 . The mapper  432  may output a mapped joint coded concatenated UCI  423 . 
     A phase shifter  434  may apply a phase shift to the mapped joint-coded concatenated UCI  423 . The phase shift may be based on the ACK/NACK  428  input. The phase shifter  434  may then output a phase shifted mapped joint-coded concatenated UCI  436  mapped to ten QPSK symbols. A PUCCH resource on a first antenna  410   a  of the wireless communication device  404  may transmit the mapped joint-coded concatenated UCI  423 . A PUCCH resource on a second antenna  410   b  of the wireless communication device  404  may transmit the phase shifted mapped joint-coded concatenated UCI  436 . 
       FIG. 5  is a flow diagram of a method  500  for transmitting uplink control information (UCI) using a format 2 PUCCH transmit diversity scheme. The method  500  may be performed by a wireless communication device  404 . The wireless communication  404  device may concatenate  502  uplink control information (UCI). The UCI may include a channel quality indicator (CQI), a precoding matrix index (PMI), and an ACK/NACK  428 . The wireless communication device  104  may then joint code  504  the concatenated UCI with a Forward Error Correction (FEC) code such as a Reed-Muller (RM) code to twenty bits to obtain a joint-coded concatenated UCI  421 . The wireless communication device  404  may then map  506  the joint-coded concatenated UCI  421  to ten QPSK symbols. 
     The wireless communication device  404  may apply  508  a phase shift to the mapped joint-coded concatenated UCI  423  based on the ACK/NACK  428 . The mapped joint-coded concatenated UCI  423  and PUCCH reference symbols may be sent  510  using a PUCCH resource on a first antenna  410   a  of the wireless communication device  404 . The phase shifted mapped joint-coded concatenated UCI  436  and PUCCH reference symbols may be sent  512  using a PUCCH resource on a second antenna  410   b  of the wireless communication device  404 . The phase shifted mapped joint-coded concatenated UCI  436  and the associated PUCCH reference symbols may be sent  512  at the same time as the mapped joint-coded concatenated UCI  423  and the associated PUCCH reference symbols. 
       FIG. 6  is a block diagram illustrating data flows for transmitting uplink control information (UCI) using a format 2a/2b PUCCH transmit diversity scheme. A wireless communication device  604  may include an uplink transmit (Tx) diversity transmission module  608 . The uplink transmit (Tx) diversity transmission module  608  of  FIG. 6  may be one configuration of the uplink transmit (Tx) diversity transmission module  108  of  FIG. 1 . The uplink transmit (Tx) diversity transmission module  608  may include uplink control information (UCI). The uplink control information (UCI) may include a channel quality indicator (CQI)/precoding matrix index (PMI)  624  and an ACK/NACK  628 . 
     An encoder  638  may receive the CQI/PMI  624 . In one configuration, the encoder  638  may be a Forward Error Correction (FEC) coder such as a Reed-Muller (20, O) coder. The encoder  638  may output a coded CQI/PMI  652 . The coded CQI/PMI  652  may then be input into a quadrature phase shift keying (QPSK) symbol mapper  640 . The QPSK symbol mapper  640  may map the coded CQI/PMI  652  to ten QPSK symbols. The QPSK symbol mapper  640  may output a mapped coded CQI/PMI  654 . 
     In one configuration, the mapped coded CQI/PMI  658  may be transmitted on one allocated PUCCH resource. Each format 2a/2b PUCCH resource may include two slots  646   a - b  with seven symbols. In each slot  646   a - b , two of the symbols may be reference symbols  648   a - b  and five of the symbols may be QPSK mapped symbols  650   a - b . A first ACK/NACK reference symbols coder  644   a  may code the ACK/NACK  628  to create reference symbols with coded ACK/NACK  648 . The reference symbols with coded ACK/NACK  648  may be coded the same way for the first slot  646   a  and the second slot  646   b . The mapped coded CQI/PMI  654  may then be multiplexed with the reference symbols with coded ACK/NACK  648  into a mapped coded CQI/PMI with ACK/NACK coded reference symbols  658  using a first multiplexer  651   a.    
     A phase shifter  642  may also receive the mapped coded CQI/PMI  654 . The phase shifter  642  may also receive the ACK/NACK  628 . Based on the ACK/NACK  628 , the phase shifter  642  may apply a phase shift to the mapped coded CQI/PMI  654 . The applied phase shift was discussed above in relation to Table 4. The phase shifter  642  may output a phase shifted mapped coded CQI/PMI  656 . A second ACK/NACK reference symbol coder  644   b  may receive the ACK/NACK  628 . The second ACK/NACK reference symbol coder  644   b  may code the ACK/NACK  628  to create reference symbols with coded ACK/NACK  648 . The phase shifted mapped coded CQI/PMI  656  may then be multiplexed with the reference symbols with coded ACK/NACK  648  into a phase shifted mapped coded CQI/PMI with ACK/NACK coded reference symbols  658  using a second multiplexer  651   b.    
     The mapped coded CQI/PMI with ACK/NACK coded reference symbols  658  may be sent using a PUCCH resource (i.e. the two slots  646   a - b ) on a first antenna  610   a  of the wireless communication device  604 . The phase shifted mapped coded CQI/PMI with ACK/NACK coded reference symbols  660  may be sent using a PUCCH resource on a second antenna  610   b  of the wireless communication device  604 . The phase shifted mapped coded CQI/PMI with ACK/NACK coded reference symbols  660  may be sent at the same time as the mapped coded CQI/PMI with ACK/NACK coded reference symbols  658 . 
       FIG. 7  is a flow diagram of a method  700  for transmitting uplink control information (UCI)  222  using a format 2a/2b PUCCH transmit diversity scheme. The method  700  may be performed by a wireless communication device  604 . The wireless communication device  604  may code  702  a channel quality indicator (CQI)/precoding matrix index (PMI)  624  with a Forward Error Correction (FEC) code such as a Reed-Muller (RM) code to twenty bits. The wireless communication device  604  may then map  704  the coded CQI/PMI  652  to ten QPSK symbols. The wireless communication device  604  may next apply  706  a phase shift to the mapped coded CQI/PMI  654 . The phase shift may be based on the ACK/NACK  628 . 
     The wireless communication device  604  may code  708  the ACK/NACK  628  on the reference symbols  648   a  of a first physical uplink control channel (PUCCH) resource for the mapped coded CQI/PMI  654 . The wireless communication device  604  may also code  710  the ACK/NACK  628  on the reference symbols  648  of a second PUCCH resource for the phase shifted mapped coded CQI/PMI  656 . The wireless communication device  604  may then combine  712  the coded ACK/NACK on the reference symbols  648  of the first PUCCH antenna  610   a  with the mapped coded channel quality indicator (CQI)/precoding matrix index (PMI)  658 . The wireless communication device  604  may also combine  714  the coded ACK/NACK on the reference symbols  648  of the second PUCCH antenna  610   b  with the phase shifted mapped coded channel quality indicator (CQI)/precoding matrix index (PMI)  656 . The wireless communication device  604  may then send  716  the mapped coded CQI/PMI with ACK/NACK coded reference symbols  658  using a PUCCH resource on a first antenna  610   a  of the wireless communication device  604 . The wireless communication device  604  may also send  718  the phase shifted mapped coded CQI/PMI with ACK/NACK coded reference symbols  660  using a PUCCH resource on a second antenna  610   b  of the wireless communication device  604 . 
       FIG. 8  is a flow diagram illustrating a method  800  for receiving uplink control information (UCI)  222  using a PUCCH transmit diversity scheme. The method  800  may be performed by a base station  102 . The method  800  of  FIG. 8  may apply to a PUCCH message  218  using format 2, format 2a or format 2b as per 3GPP TS 36.211. The base station  102  may recover two copies of the ACK/NACK  228 . One copy of the ACK/NACK  228  may be from phase shift detection and the other copy of the ACK/NACK  228  may be from the format 2/2a/2b coding. Better performance may be achieved by combining the two ACK/NACK  228  copies to obtain a more reliable ACK/NACK  228  detection. The phase shift may be removed after the detection of the ACK/NACK  228  bits. Thus, the diversity gain for other control information may remain the same as for repetition on the second antenna  110   b.    
     The base station  102  may receive  802  a first set of symbols on a first antenna  110   a . The base station  102  may also receive  804  a second set of symbols on a second antenna  110   b . The base station  102  may compute  806  the differential phase shift between the first set of symbols and the second set of symbols. Based on the differential phase shift, the base station may estimate  808  a first ACK/NACK estimate. Based on the reference symbols of the first set of symbols and the second set of symbols, the base station  102  may estimate  810  a second ACK/NACK estimate. The base station  102  may then combine  812  the first ACK/NACK estimate and the second ACK/NACK estimate to obtain a third ACK/NACK estimate. Based on the first ACK/NACK estimate, the second ACK/NACK estimate and the third ACK/NACK estimate, the base station  102  may determine  814  the ACK/NACK. 
     Based on the determined ACK/NACK, the base station  102  may remove  816  a phase shift from the second set of symbols to obtain a second set of symbols (phase shift removed). The base station  102  may then combine  818  the first set of symbols with the second set of symbols (phase shift removed). The base station  102  may decode  820  the combined symbols using a Reed-Muller (RM) decoder to obtain the CQI/PMI. The base station  102  may decode  820  the combined symbols using a Reed-Muller (RM) decoder in cases where a Reed-Muller code was used to encode the UCI. 
       FIG. 9  is a block diagram illustrating data flows for receiving uplink control information (UCI) using a format 2 PUCCH transmit diversity scheme. A base station  902  may include an uplink transmit (Tx) diversity receiving module  906 . The uplink transmit (Tx) diversity receiving module  906  of  FIG. 9  may be one configuration of the uplink transmit (Tx) diversity receiving module  106  of  FIG. 1 . The base station  902  may also include a signal receiver for the first PUCCH transmission  914   a  and a signal receiver for the second PUCCH transmission  914   b . The signal receiver for the first PUCCH transmission  914   a  may receive a first set of symbols  962   a . The signal receiver for the second PUCCH transmission  914   b  may receive a second set of symbols  962   b . The signal receivers  914  may include two or more antennas. In one configuration, the signal receivers  914  may include four or eight antennas. 
     The uplink transmit (Tx) diversity receiving module  906  may include a differential phase shift computer  964 . The differential phase shift computer  964  may compute a differential phase shift  966  between the first set of symbols  962   a  and the second set of symbols  962   b . The uplink transmit (Tx) diversity receiving module  906  may also include a phase shift estimation module  968 . The phase shift estimation module  968  may estimate a first ACK/NACK estimate  970  based on the computed differential phase shift  966 . The first set of symbols  962   a  and the second set of symbols  962   b  may be received and evaluated separately on their respective PUCCH resources. A soft output may be calculated on the log likelihood ratio (LLR) of the second set of symbols  962   b  against each phase shift version of the first set of symbols  962   a . Then the LLR of each ACK/NACK bit may be obtained. 
     The first ACK/NACK estimate  970  is approximately equivalent to a 10× differential QPSK (DQPSK) repetition code. The 10×DQPSK repetition code alone is better than the ACK/NACK performance in format 2a/2b with single antenna transmission, which is equivalent to 2×DQPSK repetitions. An ACK/NACK validation process may provide another level of protection on the ACK/NACK bits. For other information bits, the full transmit diversity gain may be maintained when the ACK/NACK is received correctly. The target bit error rate (BER) of ACK/NACK bits is very small (less than 0.0001). The PUCCH transmit diversity scheme may achieve an even lower BER. Thus, the diversity gain on control is negligible. 
     The uplink transmit (Tx) diversity receiving module  906  may further include a first decoder  972   a . The first decoder  972   a  may be a Reed-Muller decoder. The first decoder  972   a  may decode the first set of symbols  962   a  to obtain a second ACK/NACK estimate  974 . The first ACK/NACK estimate  974  and the second ACK/NACK estimate  970  may be combined using a first soft combiner  976   a  to obtain a third ACK/NACK estimate  978 . Furthermore, besides the first ACK/NACK estimate  970 , the phase shift estimation module  968  may provide the likelihoods of ACK/NACK estimation to a second most likely ACK/NACK selection module  980 . The second most likely ACK/NACK selection module  980  may then find out which ACK/NACK is to be chosen in case of an ACK/NACK validation conflict. 
     The uplink transmit (Tx) diversity receiving module  906  may include an ACK/NACK selection module  984 . The ACK/NACK selection module  984  may receive the first ACK/NACK estimate  970 , the second most likely ACK/NACK estimate  929 , and the third ACK/NACK estimate  978 . The ACK/NACK selection module  984  may then output a selected ACK/NACK estimate  986 . The ACK/NACK selection module  984  may initially select the selected ACK/NACK estimate  986  as the first ACK/NACK estimate  970 . Depending on a validation module  998  discussed below, the ACK/NACK selection module  984  may adjust the selected ACK/NACK estimate  986 . 
     The uplink transmit (Tx) diversity receiving module  906  may include a phase shift removal module  988 . The phase shift removal module  988  may receive the second set of symbols  962   b  and the selected ACK/NACK estimate  986 . Based on the selected ACK/NACK estimate  986 , the phase shift removal module  988  may remove a phase shift from the second set of symbols  962   b . The phase shift removal module  988  may output a second set of symbols (phase shift removed)  990 . 
     The uplink transmit (Tx) diversity receiving module  906  may include a second soft combiner  976   b . The second soft combiner  976   b  may receive the first set of symbols  962   a  and the second set of symbols (phase shift removed)  990 . The second soft combiner  976   b  may then combine the first set of symbols  962   a  and the second set of symbols (phase shift removed)  990  to output combined symbols  992 . The combined symbols  992  may be input into a second decoder  972   b . The second decoder  972   b  may be a Reed-Muller decoder. The second decoder  972   b  may output the CQI/PMI  994  and a joint decoded ACK/NACK estimate  996 . 
     The uplink transmit (Tx) diversity receiving module  906  may include a validation module  998 . The validation module  998  may receive the selected ACK/NACK estimate  986  and the joint decoded ACK/NACK estimate  996 . Normally, the independent estimates of the ACK/NACK should verify each other. Thus, the selected ACK/NACK estimate  986  should match the joint decoded ACK/NACK estimate  996 . If the selected ACK/NACK estimate  986  matches the joint decoded ACK/NACK estimate  996 , the joint decoded ACK/NACK estimate  996  may be output by the validation module  998  as the determined ACK/NACK  931 . 
     In rare cases when different results are obtained (i.e. when the selected ACK/NACK estimate  986  and the joint decoded ACK/NACK estimate  996  differ by more than a threshold), the ACK/NACK selection module  984  may select the third ACK/NACK estimate  978  as the selected ACK/NACK estimate  986 . The phase shift removing module  988 , second soft combiner  976   b  and second decoder  972   b  may then restart to obtain a new joint decoded ACK/NACK estimate  996 . If the results match, the validation module  998  may output the joint decoded ACK/NACK estimate  986  as the determined ACK/NACK  931 . If the results are still different, the ACK/NACK selection module  984  may select the second most likely ACK/NACK  929  as the selected ACK/NACK estimate  986 . The phase shift removing module  988 , second soft combiner  976   b  and second decoder  972   b  may then restart to obtain a new joint decoded ACK/NACK estimate  996 . If the results match, the validation module  998  may output the joint decoded ACK/NACK estimate  996  as the determined ACK/NACK  931 . 
     If the new joint decoded ACK/NACK estimate  996  still does not match the selected ACK/NACK estimate  986 , the validation module  998  may select the determined ACK/NACK  931  based on the number of bits of the CQI/PMI and the ACK/NACK, along with the second decoder  972   b  output when the selected ACK/NACK estimate  986  is the third ACK/NACK estimate  978  and when the selected ACK/NACK estimate  986  is the second most likely ACK/NACK  929 . The decision from the phase shift estimation module  968  will be more reliable when the number of information bits is large. Furthermore, with multiple orthogonal resources, the reference symbols may also be used to convey the ACK/NACK signal in format 2 with extended CP. The coding/decoding process may then be simplified and become very similar to that of format 2a/2b discussed below in relation to  FIG. 11  and  FIG. 12 . 
       FIG. 10  is a flow diagram of a method  1000  for receiving uplink control information (UCI)  222  using a format 2 PUCCH transmit diversity scheme. The method  1000  may be performed by a base station  902 . The base station  902  may receive  1002  a first set of symbols  962   a  from a signal receiver for the first physical uplink control channel (PUCCH) transmission  914   a . The base station  902  may receive  1004  a second set of symbols  962   b  from a signal receiver of a second physical uplink control channel (PUCCH) transmission  914   b . The base station  902  may compute  1006  a differential phase shift  966  between the first set of symbols  962   a  and the second set of symbols  962   b . The base station  902  may then estimate  1008  a first ACK/NACK estimate  970  using the differential phase shift  966 . The base station  902  may select  1010  the first ACK/NACK estimate  970  as the selected ACK/NACK estimate  986 . 
     The base station  902  may next remove  1012  a phase shift from the second set of symbols  962   b  based on the selected ACK/NACK estimate  986  to obtain a second set of symbols (phase shift removed)  990 . The base station  902  may combine  1013  the first set of symbols  962   a  with the second set of symbols (phase shift removed)  990 . The base station  902  may then decode  1014  the combined symbols  992  to obtain a CQI/PMI  994  and a joint decoded ACK/NACK estimate  996 . The base station  902  may compare  1016  the joint decoded ACK/NACK estimate  996  with the selected ACK/NACK estimate  986 . The base station  902  may then determine  1018  whether the joint decoded ACK/NACK estimate  996  and the selected ACK/NACK estimate  986  differ by less than a threshold. If the joint decoded ACK/NACK estimate  996  and the selected ACK/NACK estimate  986  differ by less than a threshold, the base station  902  may select  1020  the joint decoded ACK/NACK estimate  996  as the ACK/NACK  931  with great confidence. 
     If the joint decoded ACK/NACK estimate  996  and the selected ACK/NACK estimate  986  do not differ by less than a threshold, the base station  902  may next determine  1022  if the selected ACK/NACK estimate  986  is the first ACK/NACK estimate  970 . If the selected ACK/NACK estimate  986  is the first ACK/NACK estimate  970 , the base station  902  may decode  1024  the first set of symbols  962   a  to obtain a second ACK/NACK estimate  974 . The base station  902  may decode  1024  the first set of symbols  962   a  using a Reed-Muller decoder. The base station  902  may then combine  1026  the first ACK/NACK estimate  970  and the second ACK/NACK estimate  974  to obtain a third ACK/NACK estimate  978 . The base station  902  may select  1028  the third ACK/NACK estimate  978  as the selected ACK/NACK estimate  986 . The base station  902  may then remove  1012  a phase shift  966  from the second set of symbols  962   b  based on the selected ACK/NACK estimate  986 . 
     If the selected ACK/NACK estimate  986  is not the first ACK/NACK estimate  970 , the base station  902  may determine  1036  whether the selected ACK/NACK estimate  986  is the third ACK/NACK estimate  978 . If the selected ACK/NACK estimate  986  is the third ACK/NACK estimate  978 , the base station  902  may determine  1038  a second most likely ACK/NACK  929  based on the first ACK/NACK estimate  970 . The base station  902  may select  1040  the second most likely ACK/NACK  929  as the selected ACK/NACK estimate  986 . The base station  902  may then remove  1012  a phase shift  966  from the second set of symbols  962   b  based on the selected ACK/NACK estimate  986 . 
     If the selected ACK/NACK estimate  986  is not the third ACK/NACK estimate  978 , the base station  902  may determine  1042  the ACK/NACK  931  based on the number of bits in the CQI/PMI  994  and the ACK/NACK  996 . The base station  902  may also determine the ACK/NACK  929  based on the second decoder  972   b  output when the selected ACK/NACK estimate  986  is the third ACK/NACK estimate  978 . The base station  902  may further determine the ACK/NACK  929  based on the second decoder  972   b  output when the selected ACK/NACK estimate  986  is the second most likely ACK/NACK  929 . 
       FIG. 11  is a block diagram illustrating data flows for receiving uplink control information (UCI)  222  using a format 2a/2b PUCCH transmit diversity scheme. A base station  1102  may include an uplink transmit (Tx) diversity receiving module  1106 . The uplink transmit (Tx) diversity receiving module  1106  of  FIG. 11  may be one configuration of the uplink transmit (Tx) diversity receiving module  106  of  FIG. 1 . The base station  1102  may also include a signal receiver for the first PUCCH transmission  1114   a  and a signal receiver for the second PUCCH transmission  1114   b . The signal receiver for the first PUCCH transmission  1114   a  may receive a first set of symbols  1162   a . The signal receiver for the second PUCCH transmission  1114   b  may receive a second set of symbols  1162   b . The first set of symbols  1162   a  and the second set of symbols  1162   b  may be received via the PUCCH. 
     The uplink transmit (Tx) diversity receiving module  1106  may include a differential phase shift computer  1164 . The differential phase shift computer  1164  may receive the first set of symbols  1162   a  and the second set of symbols  1162   b . The differential phase shift computer  1164  may then compute the differential phase shift  1166  between the first set of symbols  1162   a  and the second set of symbols  1162   b . The uplink transmit (Tx) diversity receiving module  1106  may also include an ACK/NACK estimation module  1168 . The ACK/NACK estimation module  1168  may also be referred to as a phase shift estimation module. The ACK/NACK estimation module  1168  may receive the differential phase shift  1166 . The ACK/NACK estimation module  1168  may then estimate a first ACK/NACK estimate  1170  based on the differential phase shift  1166 . 
     If a 2-bit ACK/NACK feedback is assumed, the format 2b may be equivalent to a 2× differential QPSK (DQPSK) repetition on each antenna. Thus, the format 2b may be equivalent to an approximately 4×DQPSK repetition with two antennas. The phase shift estimation is essentially also a DQPSK demodulation. Thus, the ACK/NACK estimate from the phase shift detection is approximately equivalent to a 10×QPSK repetition code. Combined with the format 2b transmission on two antennas results in ˜14×DQPSK repetition. Thus, up to 5.4 dB (10*log 10(14/4)) gain over the simple repetition transmit diversity method. For other information bits, when the ACK/NACK is received correctly, full transmit diversity gain is maintained and there is no diversity gain when the ACK/NACK is in error. 
     The uplink transmit (Tx) diversity receiving module  1106  may include an ACK/NACK extraction module  1137 . The ACK/NACK extraction module  1137  may receive the first set of symbols  1162   a  and the second set of symbols  1162   b . The ACK/NACK extraction module  1137  may then extract the ACK/NACK from the reference symbols of the first set of symbols and the second set of symbols. The extracted ACK/NACK may be referred to as the second ACK/NACK estimate  1133 . 
     The uplink transmit (Tx) diversity receiving module  1106  may include a first soft combiner  1176   a . The first soft combiner  1176   a  may combine the first ACK/NACK estimate  1170  and the second ACK/NACK estimate  1133  to obtain a third ACK/NACK estimate  1135 . The third ACK/NACK estimate  1135  may be a more accurate estimate of the ACK/NACK and may be used as the ACK/NACK decision. The uplink transmit (Tx) diversity receiving module  1106  may include a phase shift removal module  1188 . Based on the third ACK/NACK estimate  1135 , the phase shift removal module  1188  may remove a phase shift from the second set of symbols  1162   b . The phase shift removal module  1188  may then output the second set of symbols (phase shift removed)  1190 . 
     The uplink transmit (Tx) diversity receiving module  1106  may include a second soft combiner  1176   b . The second soft combiner  1176   b  may combine the first set of symbols  1162   a  and the second set of symbols (phase shift removed)  1190 . The combined symbols  1192  may then be decoded by a decoder  1172 . The decoder  1172  may be a Reed-Muller decoder  1172 . The decoder  1172  may output the channel quality indicator (CQI)/precoding matrix index (PMI)  1194 . 
       FIG. 12  is a flow diagram of a method  1200  for receiving uplink control information (UCI)  222  using a format 2a/2b PUCCH transmit diversity scheme. The method  1200  may be performed by a base station  1102 . The base station  1102  may receive  1202  a first set of symbols  1162   a  by a signal receiver for the first PUCCH transmission  1114   a . The base station  1102  may receive  1204  a second set of symbols  1162   b  by a signal receiver for the second PUCCH transmission  1114   b . The base station  1102  may then compute  1206  a differential phase shift  1166  between the first set of symbols  1162   a  and the second set of symbols  1162   b.    
     Using the differential phase shift  1166 , the base station  1102  may estimate  1208  a first ACK/NACK estimate  1170 . The base station  1102  may also extract  1210  a second ACK/NACK estimate  1133  from the reference symbols  648  of the first set of symbols  1162   a  and the second set of symbols  1162   b . The base station  1102  may combine  1212  the first ACK/NACK estimate  1170  and the second ACK/NACK estimate  1133  to obtain a third ACK/NACK estimate  1135 . The third ACK/NACK estimate  1135  may be a more accurate estimate of the ACK/NACK and may be used as the ACK/NACK decision. 
     Using the third ACK/NACK estimate  1135 , the base station  1102  may remove  1214  a phase shift from the second set of symbols  1162   b . The base station  1102  may next combine  1216  the first set of symbols  1162   a  with the second set of symbols (phase shift removed)  1190 . The base station  1102  may then decode  1218  the combined symbols  1192  to obtain the channel quality indicator (CQI)/precoding matrix index (PMI)  1194 . The base station  1102  may decode  1218  the combined symbols  1192  using a Reed-Muller decoder  1172 . 
       FIG. 13  illustrates various components that may be utilized in a wireless communication device  1302 . The wireless communication device  1302  includes a processor  1303  that controls operation of the wireless communication device  1302 . The processor  1303  may also be referred to as a CPU. Memory  1305 , which may include both read-only memory (ROM), random access memory (RAM) or any type of device that may store information, provides instructions  1307   a  and data  1309   a  to the processor  1303 . A portion of the memory  1305  may also include non-volatile random access memory (NVRAM). Instructions  1307   b  and data  1309   b  may also reside in the processor  1303 . Instructions  1307   b  loaded into the processor  1303  may also include instructions  1307   a  from memory  1305  that were loaded for execution by the processor  1303 . The instructions  1307   b  may be executed by the processor  1303  to implement the methods disclosed herein. 
     The wireless communication device  1302  may also include a housing that contains a transmitter  1311  and a receiver  1313  to allow transmission and reception of data. The transmitter  1311  and receiver  1313  may be combined into a transceiver  1315 . A first antenna  1317   a  and a second antenna  1317   b  are attached to the housing and electrically coupled to the transceiver  1315 . Additional antennas may also be used. 
     The various components of the wireless communication device  1302  are coupled together by a bus system  1319  which may include a power bus, a control signal bus, and a status signal bus, in addition to a data bus. However, for the sake of clarity, the various buses are illustrated in  FIG. 13  as the bus system  1319 . The wireless communication device  1302  may also include a digital signal processor (DSP)  1321  for use in processing signals. The wireless communication device  1302  may also include a communications interface  1323  that provides user access to the functions of the communication device  1302 . The wireless communication device  1302  illustrated in  FIG. 13  is a functional block diagram rather than a listing of specific components. 
       FIG. 14  illustrates various components that may be utilized in a base station  1404 . The base station  1404  may include components that are similar to the components discussed above in relation to the wireless communication device  1302 , including a processor  1403 , memory  1405  that provides instructions  1407   a  and data  1409   a  to the processor  1403 , instructions  1407   b  and data  1409   b  that may reside in the processor  1403 , a housing that contains a transmitter  1411  and a receiver  1413  (which may be combined into a transceiver  1415 ), a first antenna  1417   a  and a second antenna  1417   b  electrically coupled to the transceiver  1415 , a bus system  1419 , a DSP  1421  for use in processing signals, a communications interface  1423 , and so forth. 
     As used herein, the term “determining” encompasses a wide variety of actions and, therefore, “determining” can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” can include resolving, selecting, choosing, establishing and the like. 
     The phrase “based on” does not mean “based only on,” unless expressly specified otherwise. In other words, the phrase “based on” describes both “based only on” and “based at least on.” 
     The term “processor” should be interpreted broadly to encompass a general purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine, and so forth. Under some circumstances, a “processor” may refer to an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), etc. The term “processor” may refer to a combination of processing 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 term “memory” should be interpreted broadly to encompass any electronic component capable of storing electronic information. The term memory may refer to various types of processor-readable media such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical data storage, registers, etc. Memory is said to be in electronic communication with a processor if the processor can read information from and/or write information to the memory. Memory may be integral to a processor and still be said to be in electronic communication with the processor. 
     The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may comprise a single computer-readable statement or many computer-readable statements. 
     The functions described herein may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions on a computer-readable medium. The term “computer-readable medium” refers to any available medium that can be accessed by a computer. By way of example, and not limitation, a computer-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. 
     Software or instructions may also be transmitted over a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of transmission medium. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods, and apparatus described herein without departing from the scope of the claims.