Patent Abstract:
A method of wireless communication including a plurality of fixed basestations and a plurality of mobile user equipment with each basestation transmitting to any user equipment within a corresponding cell a sounding reference signal sub-frame configuration indicating sub-frames when sounding is permitted. Each user equipment recognizes the sounding reference signal sub-frame configuration and sounds only at permitted sub-frames. Differing user equipment may have differing sounding reference signal sub-frame configurations. There are numerous manners to encode the transmitted information.

Full Description:
CLAIM OF PRIORITY 
     This application claims priority under 35 U.S.C. 119(e)(1) to U.S. Provisional Application No. 61/048,746 filed Apr. 29, 2008, U.S. Provisional Application No. 61/051,457 filed May 8, 2008 and U.S. Provisional Application No. 61/052,356 filed May 12, 2009. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The technical field of this invention is wireless communication. 
     BACKGROUND OF THE INVENTION 
       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 . 
     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. 
       FIG. 2  shows the Evolved Universal Terrestrial Radio Access (E-UTRA) time division duplex (TDD) Frame Structure. Different sub-frames are allocated for downlink (DL) or uplink (UL) transmissions. Table 1 shows applicable DL/UL sub-frame allocations. 
     
       
         
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                   
                 Switch- 
                   
               
               
                 Config- 
                 point 
                 Sub-frame number 
               
             
          
           
               
                 uration 
                 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 
               
               
                   
               
             
          
         
       
     
     SUMMARY OF THE INVENTION 
     A method of wireless communication including a plurality of fixed basestations and a plurality of mobile user equipment with each basestation transmitting to any user equipment within a corresponding cell a sounding reference signal sub-frame configuration indicating sub-frames when sounding is permitted. Each user equipment recognizes the sounding reference signal sub-frame configuration and sounds only at permitted sub-frames. Differing user equipment may have differing sounding reference signal sub-frame configurations. There are numerous manners to encode the transmitted information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects of this invention are illustrated in the drawings, in which: 
         FIG. 1  is a diagram of a communication system of the prior art related to this invention having three cells; 
         FIG. 2  shows the Evolved Universal Terrestrial Radio Access (E-UTRA) TDD Frame Structure of the prior art; 
         FIG. 3  illustrates a first example binary tree used in encoding; 
         FIG. 4  illustrates a second example binary tree used in encoding; 
         FIG. 5  illustrates a first resource sharing tree for a first set of periodicities and offsets; and 
         FIG. 6  illustrates a second resource sharing tree for a second set of periodicities and offsets. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Sounding involves exchange of signals between the base station and the connected UE. Each sounding uses a reference resource identifier selected from an available reference resource identifier map h(t, L) and a portion of the spectrum selected from an available spectrum identifier map f(t, N); where L is a group of shared parameters signaled to each UE from the group; and N is a group of shared parameters signaled to each UE from the group. Some examples utilize CAZAC sequences as the reference sequences. CAZAC sequences are complex-valued sequences with: constant amplitude (CA); and zero cyclic autocorrelation (ZAC). Examples of CAZAC sequences include: Chu sequences, Frank-Zadoff sequences, Zadoff-Chu (ZC) sequences and generalized chirp-like (GCL) sequences. CAZAC (ZC or otherwise) sequences are presently preferred. 
     In this invention each basestation  101 ,  102  and  103  transmits a sounding reference signal (SRS) to connected UEs  109 . The UE receiving the SRS then conducts sounding in accordance with the SRS sub-frame configuration. In accordance with this invention each UE may operate on a different SRS sounding sub-frame configuration. 
     The SRS sub-frame configuration is broadcast by basestation  101  in a System Information Block (SIB). This sub-frame configuration indicates which sub-frames are SRS sub-frames. Broadcast of the SRS sub-frame configuration is useful even for UEs  109  which do not transmit any SRS. SRS shouldn&#39;t collide with physical uplink shared channel (PUSCH) transmission. Thus non-SRS UEs  109  can extract some of their silent symbol periods from the SRS sub-frame configuration. These silent periods are useful for performing some measurements at UE  109 . In general each cell  107  and  108  would employ a different SRS sub-frame configuration. Ideally, basestations  101 ,  102  and  103  would select SRS sub-frame configurations to minimize cross-cell interference. 
     There are two main ways of signaling and interpreting the SRS sub-frame configuration parameters. Sub-frame configuration can be defined by two parameters: the periodicity T SFC ; and the offset Δ SFC . Both UEs  109  and basestation  101  keep a sub-frame counter C SFC  permitting UE  109  and basestation  101  to determine which sub-frames are configured for SRS transmission. A sub-frame is an SRS sub-frame if and only if Δ SFC =(C SFC )mod T SFC . The exact range of values of Δ SFC  and T SFC  need to be defined with the number of bits and encoding for each. For example, T SFC  could be selected from the set {1, 2, 3, 4, 5, . . . , 32} allowing flexible system deployment Δ SFC  could be selected from the same set. This yields maximum flexibility, but requires 10 bits of broadcast SIB signaling, which can be very costly. A reduced overhead alternative encodes and signals T SFC  first. This requires greatest integer in log 2  (T SFC ) (ceil [log 2  (T SFC )]) bits. The bits required for Δ SFC  would be either the ceil[log 2 (T SFC )] or the least integer in log 2  (T SFC ) (floor [log 2  (T SFC )]) because 0≦Δ SFC &lt;T SFC . This reduces the number of required bits for signaling Δ SFC , but only for certain scenarios where T SFC  is small. Another reduced overhead alternative hard codes a value for Δ SFC  such as zero. In that case, only T SFC  is signaled. 
     Several examples of combined T SFC , Δ SFC  coding are listed in the following tables. In these examples the SRS sub-frame configuration is encoded using either 4 or 5 bits in SIB using joint source coding in T SFC  and Δ SFC . Thus a unique 4 or 5 bit combination maps into a particular pair (T SFC , Δ SFC ). 
     Table 2 lists a 4 bit example suitable for use in frequency division duplex (FDD) systems. 
                                                               TABLE 2                       Decimal   Binary   T SFC     Δ SFC                                          0   0000   1   0           1   0001   2   0           2   0010   2   1           3   0011   5   0           4   0100   5   1           5   0101   5   2           6   0110   10   0           7   0111   10   1           8   1000   10   2           9   1001   20   0           10   1010   20   1           11   1011   20   2           12   1100   40   0           13   1101   40   1           14   1110   40   2           15   1111   Inf.   NA                        
In Table 2 a coding of decimal 15 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 3 lists another 4 bit example suitable for use in FDD systems. 
                                                               TABLE 3                       Decimal   Binary   T SFC     Δ SFC                                          0   0000   1   0           1   0001   2   0           2   0010   2   1           3   0011   5   2           4   0100   5   3           5   0101   5   4           6   0110   10   5           7   0111   10   6           8   1000   10   7           9   1001   20   8           10   1010   20   9           11   1011   20   10           12   1100   40   11           13   1101   40   12           14   1110   40   13           15   1111   Inf.   NA                        
In Table 3 a coding of decimal 15 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 4 lists a 5 bit example suitable for use in FDD systems. 
                                                               TABLE 4                       Decimal   Binary   T SFC     Δ SFC                                          0   00000   1   0           1   00001   2   0           2   00010   2   1           3   00011   5   0           4   00100   5   1           5   00101   5   2           6   00110   5   3           7   00111   5   4           8   01000   10   0           9   01001   10   1           10   01010   10   2           11   01011   10   3           12   01100   10   4           13   01101   10   5           14   01110   10   6           15   01111   20   0           16   10000   20   1           17   10001   20   2           18   10010   20   3           19   10011   20   4           20   10100   20   5           21   10101   20   6           22   10110   40   0           23   10111   40   1           24   11000   40   2           25   11001   40   3           26   11010   40   4           27   11011   40   5           28   11100   40   6           29   11101   Optional           30   11110   Optional           31   11111   Inf.   NA                        
In Table 4 codings decimal 29 and 30 are optional and not defined in this example. In Table 4 a coding of decimal 31 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 5 lists another 5 bit example suitable for use in FDD systems. 
                                                               TABLE 5                       Decimal   Binary   T SFC     Δ SFC                                          0   00000   1   0           1   00001   2   0           2   00010   2   1           3   00011   5   0           4   00100   5   1           5   00101   5   2           6   00110   5   3           7   00111   5   4           8   01000   10   0           9   01001   10   1           10   01010   10   2           11   01011   10   3           12   01100   10   4           13   01101   10   5           14   01110   10   6           15   01111   10   7           16   10000   20   0           17   10001   20   1           18   10010   20   2           19   10011   20   3           20   10100   20   4           21   10101   20   5           22   10110   20   6           23   10111   20   7           24   11000   40   0           25   11001   40   1           26   11010   40   2           27   11011   40   3           28   11100   40   4           29   11101   40   5           30   11110   40   6           31   11111   Inf.   NA                        
In Table 5 a coding of decimal 31 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 6 lists another 5 bit example suitable for use in FDD systems. 
                                                               TABLE 6                       Decimal   Binary   T SFC     Δ SFC                                          0   00000   1   0           1   00001   2   0           2   00010   2   1           3   00011   5   0           4   00100   5   1           5   00101   5   2           6   00110   5   3           7   00111   5   4           8   01000   10   3           9   01001   10   4           10   01010   10   5           11   01011   10   6           12   01100   10   7           13   01101   10   8           14   01110   10   9           15   01111   20   10           16   10000   20   11           17   10001   20   12           18   10010   20   13           19   10011   20   14           20   10100   20   15           21   10101   20   16           22   10110   40   17           23   10111   40   18           24   11000   40   19           25   11001   40   20           26   11010   40   21           27   11011   40   22           28   11100   40   23           29   11101   Optional           30   11110   Optional           31   11111   Inf.   NA                        
In Table 6 codings decimal 29 and 30 are optional and not defined in this example. In Table 6 a coding of decimal 31 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 7 lists a 4 bit example suitable for use in time division duplex (TDD) systems. 
                                                               TABLE 7                       Decimal   Binary   T SFC     Δ SFC                                          0   0000   1   0           1   0001   5   1 (a)           2   0010   5   1 (b)           3   0011   5   2           4   0100   10   0           5   0101   10   1 (a)           6   0110   10   1 (b)           7   0111   10   2           8   1000   20   0           9   1001   20   1 (a)           10   1010   20   1 (b)           11   1011   20   2           12   1100   40   0           13   1101   40   1 (a)           14   1110   40   1 (b)           15   1111   Inf.   NA                        
In Table 7 codings decimal 1, 2, 5, 6, 9, 10, 13 and 14 are encoded with respect to Uplink Pilot Transmission Slot (UpPTS) orthogonal frequency division multiplexing (OFDM) symbols. If UpPTS contains two OFDM symbols: 1(a) means the first OFDM symbol is used for SRS to determine Δ SFC ; and 1(b) means the second of OFDM symbol is used for SRS to determine Δ SFC . In Table 7 a coding of decimal 15 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 8 lists a 5 bit example suitable for use in TDD systems. 
                                                               TABLE 8                       Decimal   Binary   T SFC     Δ SFC                                          0   00000   1   0           1   00001   5   1 (a)           2   00010   5   1 (b)           3   00011   5   1 (a) + 1 (b)           4   00100   5   2           5   00101   5   3           6   00110   5   4           7   00111   10   1 (a)           8   01000   10   1 (b)           9   01001   10   1 (a) + 1 (b)           10   01010   10   2           11   01011   10   3           12   01100   10   4           13   01101   10   7           14   01110   10   8           15   01111   20   1 (a)           16   10000   20   1 (b)           17   10001   20   1 (a) + 1 (b)           18   10010   20   2           19   10011   20   3           20   10100   20   4           21   10101   20   7           22   10110   20   8           23   10111   40   1 (a)           24   11000   40   1 (b)           25   11001   40   1 (a) + 1 (b)           26   11010   40   2           27   11011   40   3           28   11100   40   4           29   11101   40   7           30   11110   40   8           31   11111   Inf.   NA                        
In Table 8 codings decimal 1, 2, 3, 7, 8, 9, 15, 16, 17, 23, 24 and 25 are encoded with respect to UpPTS OFDM symbols. If UpPTS contains two OFDM symbols: 1(a) means the first OFDM symbol is used for SRS to determine Δ SFC ; 1(b) means the second of OFDM symbol is used for SRS to determine Δ SFC ; and 1(a)+1(b) means that both OFDM symbols are used for SRS to determine Δ SFC . In Table 8 a coding of decimal 31 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA). For TDD, if the SRS sub-frame period is 1, all UL sub-frames and UpPTS can contain SRS. If UpPTS is used for short random access channel (RACH) transmission in some sub-frames, then there is no SRS. Thus basestation  101  does not assign any SRS UEs in RACH UpPTS sub-frames.
 
     Table 9 lists another 5 bit example suitable for use in TDD systems. 
                                                               TABLE 9                       Decimal   Binary   T SFC     Δ SFC                                          0   00000   1   0           1   00001   5   1 (a)           2   00010   5   1 (b)           3   00011   5   1 (a) + 1 (b)           4   00100   5   2           5   00101   5   3           6   00110   5   4           7   00111   10   1 (a)           8   01000   10   1 (b)           9   01001   10   1 (a) + 1 (b)           10   01010   10   2           11   01011   10   3           12   01100   10   6 (a)           13   01101   10   6 (b)           14   01110   10   6 (a) + 6 (b)           15   01111   20   1 (a)           16   10000   20   1 (b)           17   10001   20   1 (a) + 1 (b)           18   10010   20   2           19   10011   20   3           20   10100   20   6 (a)           21   10101   20   6 (b)           22   10110   20   6 (a) + 6 (b)           23   10111   40   1 (a)           24   11000   40   1 (b)           25   11001   40   1 (a) + 1 (b)           26   11010   40   2           27   11011   40   3           28   11100   40   6 (a)           29   11101   40   6 (b)           30   11110   40   6 (a) + 6 (b)           31   11111   Inf.   NA                        
In Table 9 codings decimal 1, 2, 3, 7, 8, 9, 12 to 17, 20 to 25, 28, 29 and 30 are encoded with respect to UpPTS OFDM symbols. If UpPTS contains two OFDM symbols: 1(a) means the first OFDM symbol is used for SRS to determine Δ SFC ; 1(b) means the second of OFDM symbol is used for SRS to determine Δ SFC ; and 1(a)+1(b) means that both OFDM symbols are used for SRS to determine Δ SFC . In Table 8 a coding of decimal 31 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 10 lists another 4 bit example suitable for use in FDD systems. Sounding reference signal sub-frames are the sub-frames satisfying └n s /2┘ mod T SFC εΔ SFC . 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 10 
               
               
                   
                   
               
               
                   
                 Decimal 
                 Binary 
                 T SFC   
                 Δ SFC   
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0 
                 0000 
                 1 
                 0 
               
               
                   
                 1 
                 0001 
                 2 
                 0 
               
               
                   
                 2 
                 0010 
                 2 
                 1 
               
               
                   
                 3 
                 0011 
                 5 
                 0 
               
               
                   
                 4 
                 0100 
                 5 
                 1 
               
               
                   
                 5 
                 0101 
                 5 
                 2 
               
               
                   
                 6 
                 0110 
                 5 
                 3 
               
               
                   
                 7 
                 0111 
                 5 
                 0, 1 
               
               
                   
                 8 
                 1000 
                 5 
                 2, 3 
               
               
                   
                 9 
                 1001 
                 10 
                 0 
               
               
                   
                 10 
                 1010 
                 10 
                 1 
               
               
                   
                 11 
                 1011 
                 10 
                 2 
               
               
                   
                 12 
                 1100 
                 10 
                 3 
               
               
                   
                 13 
                 1101 
                 10 
                 0, 1, 2, 3, 4, 6, 8 
               
               
                   
                 14 
                 1110 
                 10 
                 0, 1, 2, 3, 4, 5, 6, 8 
               
               
                   
                 15 
                 1111 
                 reserved 
                 reserved 
               
               
                   
                   
               
             
          
         
       
     
     Table 11 lists another 4 bit example suitable for use in TDD systems. Sounding reference signal sub-frames are the sub-frames satisfying └n s /2┘ mod T SFC εΔ SFC . Sounding reference signals are transmitted only in configured UL sub-frames or UpPTS. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 11 
               
               
                   
                   
               
               
                   
                 Decimal 
                 Binary 
                 T SFC   
                 Δ SFC   
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0 
                 0000 
                 5 
                 1 
               
               
                   
                 1 
                 0001 
                 5 
                 1, 2 
               
               
                   
                 2 
                 0010 
                 5 
                 1, 3 
               
               
                   
                 3 
                 0011 
                 5 
                 1, 4 
               
               
                   
                 4 
                 0100 
                 5 
                 1, 2, 3 
               
               
                   
                 5 
                 0101 
                 5 
                 1, 2, 4 
               
               
                   
                 6 
                 0110 
                 5 
                 1, 3, 4 
               
               
                   
                 7 
                 0111 
                 5 
                 1, 2, 3, 4 
               
               
                   
                 8 
                 1000 
                 10 
                 1, 2, 6 
               
               
                   
                 9 
                 1001 
                 10 
                 1, 3, 6 
               
               
                   
                 10 
                 1010 
                 10 
                 1, 6, 7 
               
               
                   
                 11 
                 1011 
                 10 
                 1, 2, 6, 8 
               
               
                   
                 12 
                 1100 
                 10 
                 1, 3, 6, 9 
               
               
                   
                 13 
                 1101 
                 10 
                 1, 4, 6, 7 
               
               
                   
                 14 
                 1110 
                 reserved 
                 reserved 
               
               
                   
                 15 
                 1111 
                 reserved 
                 reserved 
               
               
                   
                   
               
             
          
         
       
     
     For TDD, a SRS sub-frame period of 1 means that all UL sub-frames and UpPTS can contain SRS. If UpPTS is used for short RACH transmission in some sub-frames, then there is no SRS. Thus basestation  101  does not assign any SRS UEs in RACH UpPTS sub-frames. For TDD, it is not clear how to have SRS sub-frame configuration with period  2 . 
     Broadcasting both Δ SFC  and T SFC  supports flexible SRS sub-frame configuration. Different values of Δ SFC  can be assigned in different cells. Thus SRS transmission in one cell does not interfere with a neighboring cells. Because the set of UL sub-frames varies with DL/UL sub-frame configuration, Δ SFC  is needed for SRS sub-frame configuration in TDD. Note binary tree  300  illustrates in  FIG. 3  is just an example. Different trees can be used with different depths and configurations and different joint source-encodings of (Δ SFC , T SFC ). 
       FIG. 3  illustrates a manner of jointly encoding Δ SFC  and T SFC  with an efficient source code to support multiple values for the offset Δ SFC  for each T SFC  using an underlying structure.  FIG. 3  illustrates a binary tree based structure  300 . Binary tree  300  has exactly 2 x −1 nodes, where x is 4 in this example. Identifying any point on the binary tree requires exactly x bits, 4 bits in this example. A reserved codeword may be defined meaning no SRS, for example. Each node in the binary tree is assigned a mapping to a pair of (Δ SFC , T SFC ). The simplest mapping is that nodes at a certain depth are assigned a unique value of T SFC . Referring to  FIG. 3 , for node  1  T SFC =L, for nodes ( 2 ,  3 ) T SFC =2, for nodes ( 4 ,  5 ,  6 ,  7 ) T SFC =3, and for nodes ( 8 ,  9 ,  10 ,  11 ,  12 ,  13 ,  14  and  15 ) T SFC =3. Thus the depth identifies T SFC . In this example offset Δ SFC  is derived from the value of the node mod T SFC . Such code is even simpler if we consider binary values for labeled nodes. The position of the most significant 1 bit in the binary value of a node equals the value of T SFC . This is illustrated in  FIG. 3 . The remaining less significant bits identify offset Δ SFC . This same binary code can be used to encode frequency position (offset and bandwidth) of SRS. 
       FIG. 4  illustrates another embodiment of this invention. Binary tree  400  illustrated in  FIG. 4  identifies sub-frames having periodicities T SFC  of (1, 2, 4, 8, 16) ms. Each node in binary tree  400  is mapped to a pair of (Δ SFC , T SFC ). The simplest mapping assigns a unique value of T SFC  to all nodes at a certain depth.  FIG. 4  illustrates this assignment. A simple 5-bit code identifies the node. The position of most significant 1 identifies T SFC  as 2 (N-1) . The remaining bits identify the offset Δ SFC . If all 0 is signaled (00000), this identifies no SRS (infinity) or alternatively a one-shot SRS. 
     In another embodiment of the invention, the pair (Δ SFC , T SFC ) is coded jointly (source encoding) and broadcast in the SIB. In this embodiment the tree structure is not necessary. For example, if T SFC  takes on values from the set (1, 2, 4, 5, 10) ms, then there are 1+2+4+5+10=22 possible values for the combination (Δ SFC , T SFC ). Each one of these combinations is mapped to a unique number Y out 22 numbers and can be represented by 5 bits. Broadcasting the unique number identifies the (Δ SFC , T SFC ) pair. Broadcasting the unique number could be in binary. In this example, 5 bits are need to represent the 22 possible values of Y. One option maps the range of Y into T SFC . Then (Y)mod T SFC  identifies Δ SFC . 
     Suppose T SFC  can have values from the set (A 1 , A 2 , . . . , A N ) ms. There are A 1 +A 2 + . . . +A N  values for the communicated number Y. This requires ceil[log 2 (A 1 +A 2 + . . . +A N )] bits to represent. The values of T SFC  and Δ SFC  are encoded as follows. If Y is in the range 1 to A 1  then T SFC  is A 1 . If Y is in the range 1+A 1  to A 1 +A 2  then T SFC  is A 2 . If Y is in the range 1+A 1 + . . . +A K  to A 1 + . . . +A K +A K+1  then T SFC  is A K+1 . The value of Δ SFC  is determined as (Y)mod T SFC . Any remaining values of Y which do not map into (Δ SFC , T SFC ) can be used to communicate re-configuration, one-shot SRS or other options. 
     In another embodiment of the invention, the SRS sub-frame configuration may not be exactly qui-spaced. In this embodiment introduces another parameter δ SFC . Then, the SRS sub-frames are the sub-frames C SFC  for which any of the following equations hold:
 
Δ SFC =C SFC  mod T SFC  
 
1+Δ SFC   =C   SFC  mod  T   SFC  
 
2+Δ SFC   =C   SFC  mod  T   SFC  
 
δ SFC +Δ SFC   =C   SFC  mod  T   SFC  
 
The value of the parameter δ SFC  can be pre-determined and fixed. In this case the value of δ SFC  can be inferred from the cell ID. Alternatively, the value of δ SFC  can be signaled in the SIB. As a further alternative, the value of δ SFC  can be encoded jointly or separately with T SFC  and Δ SFC .
 
     In other embodiments of the invention, multiple values for T SFC , Δ SFC  and δ SFC  are possible. These values can also be broadcast via SIB. 
     RRC signaled SRS timing parameters include: duration having a range from one-shot to infinite; periodicity indicating the SRS transmission period from the UE  109 ; and sub-frame offset identifying the offset within the SRS transmission period from the UE. 
     In a first embodiment the RRC overhead for SRS timing parameters include: duration is one-shot to infinite and can be encoded in one bit; periodicity selected from (2, 5, 10, 20, 40, 80, 160, 320) ms which can be encoded in 3 bits; and sub-frame offset which must be designed according to the worst case of the longest possible periodicity thus requiring ceil [log 2  (320)] or 9 bits to encode. Thus the number of UE specific bits signaled via RRC to describe the SRS configuration in this example equals 1+3+9=13 bits. Since the cell wide sub-frame configuration is separate from the UE specific parameters listed above, there are either two possibilities. 
     The number of bits and source encoding required for UE specific parameters could depend on the actual sub-frame configuration transmitted via SIB. For example, if the sub-frame configuration notes every sub-frame is an SRS sub-frame, then 1+3+9=13 bits are required to specify the UE specific parameters. Alternatively, if the sub-frame configuration notes that every tenth sub-frame is an SRS sub-frame, then a smaller number of bits would be required to specify the UE specific parameters. This approach is more cumbersome. It likely would require a different definition of RRC configured parameters, depending on the sub-frame configuration. This would disadvantageously further complicate the specification. The number of bits required for UE specific RRC parameters can be independent of the actual sub-frame configuration transmitted via SIB. 
     The worst case sub-frame configuration is when all sub-frames are SRS sub-frames. The number of RRC configured SRS timing parameters is this worst case is 1+3+9=13 bits. 
     In the second option there are two SRS periods that are not multiples of each other and cannot be multiplexed on a common SRS (frequency) resource. Possible SRS periods are selected from the set (2, 5, 10, 20, 40, 80, 160, 320) ms. Thus, since 2 ms and 5 ms cannot be multiplexed, any given SRS resource should be shared either with periodicities selected from the set S 1  (5, 10, 20, 40, 80, 160, 320) ms or set S 2  (2, 10, 20, 40, 80, 160, 320) ms.  FIG. 5  illustrates a resource sharing tree  500  for set S 1 . Tree  500  for set S 1  illustrated in  FIG. 5  has 8 levels including node  1 . Each W is a binary tree with 5 levels. The tree for set S 1  has 1+5+10+20+40+80+160+320=636 nodes. This requires 10 bits to represent. Each node of the tree for set S 1  encodes both the periodicity and the offset. There are 5 nodes at level  2  ( 2 ,  3 ,  4 ,  5 ,  6 ). Each of these nodes has a periodicity T SFC  of 5 ms. The offset Δ SFC  increases from left to right via a one-to-one mapping from ( 2 ,  3 ,  4 ,  5 ,  6 ) to ( 0 ,  1 ,  2 ,  3 ,  4 ). This example is a simple subtraction of 2. Alternatively, it can be a mod  5  operation. At level  3 , there are 10 nodes ( 7  to  16 ) each having a periodicity of 10 ms. Offsets Δ SFC  can be derived either via subtraction or a mod  10  operation as previously described. 
     Table 12 lists the relationship between SRS periodicity T SFC  and the node index for set S 1 . The SRS periodicity T SFC  can be extracted from the node index via a look-up table and a few comparisons. The SRS offset Δ SFC  can be extracted by performing (Node_Index)mod T SFC . Thus SRS periodicity T SFC  and the SRS offset Δ SFC  are easily found from node index. 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 12 
               
             
             
               
                   
                   
               
               
                   
                 T SFC   
               
             
          
           
               
                   
                 5 ms 
                 10 ms 
                 20 ms 
                 40 ms 
                 80 ms 
                 160 ms 
                 320 ms 
               
               
                   
                   
               
             
          
           
               
                 Node 
                 2-7 
                 7-16 
                 17-36 
                 37-76 
                 77-156 
                 157-316 
                 317-636 
               
               
                 Index 
               
               
                 Range 
               
               
                   
               
             
          
         
       
     
       FIG. 6  illustrates resource sharing tree  600  for set S 2 . Tree  600  for set S 2  has 8 levels and each W is a binary tree with 5 levels. Tree  600  for set S 1  has 1+2+10+20+40+80+160+320=633 nodes. This requires 10 bits to represent. Each node of the tree encodes both periodicity T SFC  and offset Δ SFC . There are 2 nodes at level  2  ( 2 , 3 ) Each of these nodes has a periodicity T SFC  of 2 ms. Offset Δ SFC  increases from left to right in a one-to-one mapping from ( 2 , 3 ) to ( 0 , 1 ). This could be implemented by a simple subtraction of 2. Alternatively, it can be a mod  2  operation. At level  3 , there are 10 nodes ( 4  to  13 ) each having a periodicity T SFC  of 10 ms. Offsets Δ SFC  can be derived either via subtraction or a mod  10  operation as previously described. 
     Table 13 lists the relationship between SRS periodicity T SFC  and the node index for set S 2  for two alternative codings. The SRS periodicity T SFC  can be extracted from the node index via a look-up table and a few comparisons. The SRS offset Δ SFC  can be extracted by performing (Node_Index)mod T SFC . Thus SRS periodicity T SFC  and the SRS offset Δ SFC  are easily found from node index. 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 13 
               
             
             
               
                   
                   
               
               
                   
                 T SFC   
               
             
          
           
               
                   
                 2 ms 
                 10 ms 
                 20 ms 
                 40 ms 
                 80 ms 
                 160 ms 
                 320 ms 
               
               
                   
                   
               
             
          
           
               
                 Node 
                 2-3 
                 4-13 
                 14-33 
                 34-73 
                 74-153 
                 154-313 
                 314-633 
               
               
                 Index 
                   
                 7-16 
                 17-36 
                 37-76 
                 77-156 
                 157-316 
                 317-636 
               
               
                 Range 
               
               
                   
               
             
          
         
       
     
     The designation of which tree is used (set S 1  or set S 2 ) can be implicitly tied to some other system parameter. For example, set S 1  may be used for TDD and set S 2  used for FDD. This choice may be tied to some alternate system parameters, broadcast via SIB or tied to some specific values of SRS sub-frame configuration. Thus the number of required RRC signaling bits can be reduced from 13 bits to 11 bits. This is about a 15% overhead reduction. This overhead reduction carries no penalty and is achieved by employing efficient source encoding of the periodicity and sub-frame offset. This set of embodiments reduces SIB and RRC signaling overhead for parameters related to SRS timing using efficient data structures such as trees. This overhead reduction is especially important for SIB signaling due to coverage issues. 
     The RRC signaled UE specific SRS timing parameters of this invention include: duration from one-shot to infinite; periodicity T (SFC, UE)  for the particular UE  109 ; sub-frame Offset Δ (SFC, UE)  within the SRS transmission period from UE  109 . The UE  109  transmits SRS in sub-frames for which the counter C SFC  satisfies Δ (SFC, UE) =(C SFC )mod T SFC, UE . There are several methods to signal T SFC, UE  and Δ SFC, UE  to UEs  109 . 
     In a first option defining SRS RRC timing parameters the total RRC overhead for SRS timing parameters is similar to that described above: duration is one-shot to infinite and can be encoded in one bit; periodicity selected from (2, 5, 10, 20, 40, 80, 160, 320) ms which can be encoded in 3 bits; and sub-frame offset which must be designed according to the worst case of the longest possible periodicity thus requiring ceil[log 2 (320)] or 9 bits to encode. Thus the number of UE specific bits signaled via RRC to describe the SRS configuration in this example equals 1+3+9=13 bits. Since the cell wide sub-frame configuration is separate from the UE specific parameters listed above, there are either two possibilities. 
     Table 14 lists a 5 bit example suitable for use UE specific SRS sub-frame configurations. 
                                                               TABLE 14                       Decimal   Binary   T SFC     Δ SFC                                          0   00000   1   0           1   00001   2   0           2   00010   2   1           3   00011   5   0           4   00100   5   1           5   00101   5   2           6   00110   5   3           7   00111   5   4           8   01000   10   0           9   01001   10   1           10   01010   10   2           11   01011   10   3           12   01100   10   4           13   01101   10   5           14   01110   10   6           15   01111   10   7           16   10000   10   8           17   10001   10   9           18   10010   20   0           19   10011   20   1           20   10100   20   2           21   10101   20   3           22   10110   20   4           23   10111   20   5           24   11000   20   6           25   11001   20   7           26   11010   20   8           27   11011   20   9           28   11100   20   10           29   11101   20   11           30   11110   20   12           31   11111   Inf.   0                        
In Table 14 a coding of decimal 31 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 15 lists a 4 bit example suitable for use UE specific SRS sub-frame configurations. 
                                                               TABLE 15                       Decimal   Binary   T SFC     Δ SFC                                          0   0000   1   0           1   0001   2   0           2   0010   2   1           3   0011   5   0           4   0100   5   1           5   0101   5   2           6   0110   5   3           7   0111   10   0           8   1000   10   1           9   1001   10   2           10   1010   10   3           11   1011   20   0           12   1100   20   1           13   1101   20   2           14   1110   20   3           15   1111   Inf.   0                        
In Table 15 a coding of decimal 15 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA).
 
     Table 16 lists a first 3 bit example suitable for use UE specific SRS sub-frame configurations. 
     
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 16 
               
               
                   
                   
               
               
                   
                 Decimal 
                 Binary 
                 T SFC   
                 Δ SFC   
               
               
                   
                   
               
             
             
               
                   
                 0 
                 000 
                  1 
                 0 
               
               
                   
                 1 
                 001 
                 10 
                 0 
               
               
                   
                 2 
                 010 
                 10 
                 1 
               
               
                   
                 3 
                 011 
                 10 
                 2 
               
               
                   
                 4 
                 100 
                 20 
                 0 
               
               
                   
                 5 
                 101 
                 20 
                 1 
               
               
                   
                 6 
                 110 
                 20 
                 2 
               
               
                   
                 7 
                 111 
                 20 
                 3 
               
               
                   
                 8 
                 000 
                 Inf. 
                 0 
               
               
                   
                   
               
             
          
         
       
     
     In Table 16 a coding of decimal 8 indicates no SRS thus T SFC  is infinite, Δ SFC  is meaningless and not applicable (NA). 
     Table 17 lists a second 3 bit example suitable for use UE specific SRS sub-frame configurations. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 17 
               
               
                   
                   
               
               
                   
                 Decimal 
                 Binary 
                 T SFC   
                 Δ SFC   
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0 
                 000 
                 5 
                 0 
               
               
                   
                 1 
                 001 
                 5 
                 0 
               
               
                   
                 2 
                 010 
                 5 
                 1 
               
               
                   
                 3 
                 011 
                 10 
                 2 
               
               
                   
                 4 
                 100 
                 10 
                 0 
               
               
                   
                 5 
                 101 
                 10 
                 1 
               
               
                   
                 6 
                 110 
                 20 
                 2 
               
               
                   
                 7 
                 111 
                 20 
                 3 
               
               
                   
                 8 
                 000 
                 20 
                 0 
               
               
                   
                   
               
             
          
         
       
     
     In a second option, the number of bits and source encoding required for UE specific parameters could depend on the actual sub-frame configuration transmitted via SIB. For example, if the sub-frame configuration notes every sub-frame is an SRS sub-frame, then 1+3+9=13 bits are required to specify the UE specific parameters. Alternatively, if the sub-frame configuration notes that every tenth sub-frame is an SRS sub-frame, then a smaller number of bits would be required to specify the UE specific parameters. This approach is more cumbersome. It likely would require a different definition of RRC configured parameters, depending on the sub-frame configuration. This would disadvantageously further complicate the specification. The number of bits required for UE specific RRC parameters can be independent of the actual sub-frame configuration transmitted via SIB. The worst case sub-frame configuration is when all sub-frames are SRS sub-frames. The number of RRC configured SRS timing parameters is this worst case is 1+3+9=13 bits. 
     The number of bits required for UE specific RRC parameters can be independent of the actual sub-frame configuration as signaled by SIB. The worst case sub-frame configuration is when all sub-frames are SRS sub-frames. The number of RRC configured SRS timing parameters is this worst case is 1+3+9=13 bits. 
     The amount of RRC signaling overhead needed to communicate the UE specific SRS configuration can be reduced as follows. The set of SRS periods T (SFC, UE) (1) &lt;T (SFC, UE) (2) &lt;. . . &lt;T (SFC, UE) (K) has already been defined. For example, suppose this set is (2, 5, 10, 20, 40, 80, 160, 320) ms including K=8 possible SRS periods. Using this set of SRS periods, the specification can define the switch-point numbers N( 1 )&lt;N( 2 )&lt;. . . &lt;N(K)&lt;N(K +1) as follows. These numbers are defined as N( 1 )=0 and N(k +1) is recursively defined as N(k)+T (SFC, UE) (k), where integer k ranges from 1 to K. This recursion produces N( 2 )=2, N( 3 )=7, N( 4 )=17, N( 5 )=37, N( 6 )=(77), N( 7 )=(157), N( 8 )=317, N( 9 )=637 for the switching point numbers. 
     A configuration index N is signaled to UE  109  using the RRC. The UE  109  finds the unique index k for which N(k)≦N&lt;N(k+1). The sub-frame period is T (SFC, UE) =T (SFC, UE)  (k) and the offset is Δ (SFC, UE) =N−N(k). Thus if configuration index N=35 is signaled to UE  109 , UE  109  determines 17=N( 4 )≦N&lt;N( 5 )=37. Thus the derived index is k=4. UE  109  will use T (SFC, UE)  (4)=20 ms and Δ (SFC, UE) =N−N( 4 )=18. 
     Since the largest switch point is N( 9 )=637, the number of bits needed to signal the configuration is ceil[log 2 (637)]=10 bits. Including the bit which selects a duration between one-shot and infinite, a total of 11 bits are needed for UE specific SRS configuration. This reduces the number of required RRC signaling bits from 13 bits to 11 bits. This is a 15% overhead reduction. This overhead reduction carries no penalty and is achieved by employing efficient source encoding of the periodicity and sub-frame offset. 
     In a still further embodiment of the invention, basestation  101  signals the SRS configuration index to UE  109  using DL signaling. UE  109  receives the configuration index and infers the SRS sub-frame period and the offset. This jointly encodes the SRS sub-frame period and offset in the configuration index. 
     In yet further embodiment of the invention, one sub-frame carries more than one sounding reference signal (SRS). For example, in evolved-UMTS radio access (EUTRA) configurations for TDD, the sub-frame carrying the UpPTS field can carry two SRS (OFDM) symbols. When using TDD, the basestation  101  informs UE  109  which OFDM symbol should be used for SRS transmission. An additional bit may be added to signal specifically which OFDM symbol of the sub-frame should be used for SRS transmission. UE  109  infers sub-frame as before, but the additional bit informs UE  109  which OFDM symbol is used for SRS transmission. For example, if this bit is 0, the first possible SRS symbol of the signaled sub-frame is used. If this bit is 1, then the second possible SRS symbol of the signaled sub-frame is used. In other embodiments, two bits are used to signal UE  109  whether first possible OFDM symbol is used for SRS, whether second possible OFDM symbol is used for SRS, or whether both possible OFDM symbols are used for SRS. 
     In a still further embodiment a 2-bit overhead reduction can be made by signaling the SRS periodicity T SFC  and SRS offset Δ SFC  through the SRS configuration index as follows. The SRS configuration index is RRC signaled using 9 bits. UE  109  uses a look-up table to determine a range encompassing the SRS configuration index. This range is uniquely mapped to a SRS periodicity T SFC  using the same row of the look-up table. The SRS offset Δ SFC  is the SRS configuration index—begin. This same signaling type can be applied to CQI reporting. Table 18 lists an example look-up table. 
     
       
         
               
               
               
             
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 18 
               
             
             
               
                   
                   
               
               
                   
                 SRS 
                   
               
               
                   
                 Configuration 
               
               
                   
                 Index Range 
               
               
                   
                 Begin to End 
               
             
          
           
               
                 Begin 
                 End 
                 T SFC   
               
               
                   
               
             
          
           
               
                 0 
                 1 
                 2 
               
               
                 2 
                 6 
                 5 
               
               
                 7 
                 16 
                 10 
               
               
                 17 
                 36 
                 20 
               
               
                 37 
                 76 
                 40 
               
               
                 77 
                 156 
                 80 
               
               
                 157 
                 316 
                 160 
               
               
                   
               
             
          
         
       
     
     Consider the following example. A Example: SRS configuration index of 58 is signaled from basestation  101  to UE  109 . Table 18 shows that index  58  falls within the range 37 to 76. This row lists a SRS periodicity T SFC  of 40 ms. Offset SRS offset Δ SFC  is the signaled index  58  minus the range beginning of 37. 
     This invention exploits possibilities of reducing UE specific RRC signaling overhead for parameters related to SRS.

Technology Classification (CPC): 7