Abstract:
A method for setting a periodicity and an offset in rank indicator (RI) reporting in a user equipment in a wireless communication system receives a radio resource control (RRC) signal from a base station, decodes a RI periodicity and offset configuration index, sets the periodicity and offset in accordance with said decoded periodicity and offset configuration index and reports a RI according to the set periodicity and offset. The periodicity is an integer and reporting a RI reports with equal the product of the periodicity and a period of reporting of the channel quality indicator (CQI) and the precoding matrix indicator (PMI).

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority under 35U.S.C. 119(e)(1) to U.S. Provisional Application No. 61/088,081 filed Aug. 12, 2008. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The technical field of this invention is mobile wireless telephones. 
       BACKGROUND OF THE INVENTION 
       [0003]      FIG. 1  shows an exemplary wireless telecommunications network  100 . The illustrative telecommunications network includes base stations  101 ,  102  and  103 , though in operation, a telecommunications network necessarily includes many more base stations. Each of base stations  101 ,  102  and  103  are operable over corresponding coverage areas  104 ,  105  and  106 . Each base station&#39;s coverage area is further divided into cells. In the illustrated network, each base station&#39;s coverage area is divided into three cells. Handset or other user equipment (UE)  109  is shown in Cell A  108 . Cell A  108  is within coverage area  104  of base station  101 . Base station  101  transmits to and receives transmissions from UE  109 . As UE  109  moves out of Cell A  108  and into Cell B  107 , UE  109  may be handed over to base station  102 . Because UE  109  is synchronized with base station  101 , UE  109  can employ non-synchronized random access to initiate handover to base station  102 . 
         [0004]    Non-synchronized UE  109  also employs non-synchronous random access to request allocation of up link  111  time or frequency or code resources. If UE  109  has data ready for transmission, which may be traffic data, measurements report, tracking area update, UE  109  can transmit a random access signal on up link  111 . The random access signal notifies base station  101  that UE  109  requires up link resources to transmit the UEs data. Base station  101  responds by transmitting to UE  109  via down link  110 , a message containing the parameters of the resources allocated for UE  109  up link transmission along with a possible timing error correction. After receiving the resource allocation and a possible timing advance message transmitted on down link  110  by base station  101 , UE  109  optionally adjusts its transmit timing and transmits the data on up link  111  employing the allotted resources during the prescribed time interval. 
         [0005]      FIG. 2  shows the Evolved Universal Terrestrial Radio Access (E-UTRA) time division duplex (TDD) Frame Structure. Different subframes are allocated for downlink (DL) or uplink (UL) transmissions. Table 1 shows applicable DL/UL subframe allocations. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Config- 
                 Switch-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 
       [0006]    A method for setting a periodicity and an offset in rank indicator (RI) reporting in a user equipment in a wireless communication system receives a radio resource control (RRC) signal from a base station, decodes a RI periodicity and offset configuration index, sets the periodicity and offset in accordance with said decoded periodicity and offset configuration index and reports a RI according to the set periodicity and offset. The periodicity is an integer and reporting a RI reports with a periodicity equal to the product of the RI integer periodicity and a period of reporting of the channel quality indicator (CQI) and the precoding matrix indicator (PMI). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    These and other aspects of this invention are illustrated in the drawings, in which: 
           [0008]      FIG. 1  is a diagram of a communication system of the prior art related to this invention having three cells; 
           [0009]      FIG. 2  shows the Evolved Universal Terrestrial Radio Access (E-UTRA) Time Division Duplex (TDD) frame structure of the prior art; and 
           [0010]      FIGS. 3(   a ) and  3 ( b ) together illustrate a flow chart of method  300  of operation of UE  109  in accordance with this invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0011]    With spatial multiplexing, base station (Evolved Universal Terrestrial Radio Access Node B or eNB) may send multiple data streams or layers to UEs in downlink transmission using the same frequency. The number of such layers or streams is defined as the rank. For LTE Rel-8, UE  109  needs to estimate the DL channel and report the recommended rank indicator (RI) to eNB  101 . UE  109  also must report the channel quality indicator (CQI) and the precoding matrix indicator (PMI). These indicators form a set of recommended transmission property to eNB  109 . Upon receiving this feedback from UE  109  (RI/PMI/CQI), eNB  101  performs corresponding downlink scheduling. 
         [0012]    RI, CQI and PMI are fed back from UE  109  to eNB  101  on Physical Uplink Control CHannel (PUCCH). Both RI and a combined CQI/PMI are reported periodically but with different periodicity. The RI feedback periodicity is generally M RI  times greater than the CQI/PMI periodicity. M RI  is generally an integer value. In addition, an offset between the RI reporting subframe and the CQI/PMI reporting subframe is denoted N OFFSET,RI . M RI  and N OFFSET,RI  are jointly encoded, and sent by eNB  101  to UE  109  in a Radio Resource Control (RRC) message. 
         [0013]    For periodic Rank Indicator (RI), Channel Quality Indicator (CQI) and precoding matrix indicator (PMI) reporting such as on Physical Uplink Control CHannel (PUCCH) of 3GPP (E-UTRA), RI and CQI/PMI are separately reported. These are not reported in the same subframe. The CQI/PMI reporting has a periodicity P in subframes and a reporting offset N OFFSET  in subframes which uniquely determines the reporting instances of CQI/PMI. The reporting interval of the RI reporting is an integer multiple M RI  of wideband CQI/PMI period P in subframes. Exemplary values of M RI  are (1, 2, 5, 10, 20, 40, OFF) in 3GPP E-UTRA. The RI reporting also employs a RI reporting offset N OFFSET,RI  defined relative to the CQI/PMI reporting offset N Offset . 
         [0014]    The reporting periodicity and offset for CQI/PMI are jointly encoded and semi-statically configured by higher-layer Radio Resource Control (RRC) message. The invention includes the following procedures to determine the parameters of RI reporting. 
         [0015]    In a first embodiment, the RI reporting offset and periodicity are separately encoded and semi-statically configured. This configuration is signaled to the UE  109  by a higher-layer RRC message. 
         [0016]    In a second embodiment, the RI reporting offset and periodicity are jointly encoded and semi-statically configured. This configuration can be signaled to the UE  109  by a higher-layer RRC message. 
         [0017]    In a third embodiment, a RI periodicity and offset configuration index I RI  is used to signal the RI periodicity M RI  (which is an integral multiple of the CQI/PMI periodicity P) and a RI offset N OFFSET,RI . The value of RI offset N OFFSET,RI  is specified by −I RI +n. The RI periodicity and offset configuration index I RI  is signaled in a RRC message. The quantity n is a pre-defined variable. Thus subtracting I RI  from the fixed value n uniquely determines the RI multiple offset N OFFSET,RI . The variable n is a pre-defined function of the RI periodicity M RI  and the offset configuration index I RI . In one embodiment, n is related to the maximum CQI/PMI reporting offset of 160 in 3GPP E-UTRA. In another embodiment, n is an integer multiple of the maximum CQI/PMI offset. 
         [0018]    Table 2 lists the mapping of RI Configuration Index I RI  to M RI  and N OFFSET,RI  with n determined by the range of I RI . 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 RI Periodicity and Offset 
                 Value of 
                 Value of 
               
               
                   
                 Configuration Index I RI   
                 Peridocity M RI   
                 Offset N OFFSET,RI   
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  0 ≦ I RI  ≦ 159 
                 1 
                 −I RI   
               
               
                   
                 160 ≦ I RI  ≦ 319 
                 2 
                 −I RI  + 160 
               
               
                   
                 320 ≦ I RI  ≦ 479 
                 5 
                 −I RI  + 320 
               
               
                   
                 480 ≦ I RI  ≦ 639 
                 10 
                 −I RI  + 480 
               
               
                   
                 640 ≦ I RI  ≦ 799 
                 20 
                 −I RI  + 640 
               
               
                   
                 800 ≦ I RI  ≦ 959 
                 40 
                 −I RI  + 800 
               
               
                   
                 960 = I RI   
                 OFF 
                 NA 
               
             
          
           
               
                   
                 961 ≦ I RI  ≦ 2047 
                 Reserved 
               
               
                   
                   
               
             
          
         
       
     
         [0019]      FIGS. 3(   a ) and  3 ( b ) illustrate a flow chart of method  300  of operation of UE  109  in accordance with this invention with n=160. Method  300  begins with start block  301 . Method  300  next receives the RRC in block  302  and decoded I RI  in block  303 . Method  300  proceeds to test block  304 . 
         [0020]    Test block  304  determines if I RI  is between 0 and 159 inclusive. If this is true (Yes at test block  304 ), then block  305  sets M RI =1 and N OFFSET,RI =−I RI . Method  300  the proceeds to block  319  via links C and D. If this in not true (No at test block  304 ), then method  300  proceeds to test block  306 . 
         [0021]    Test block  306  determines if I RI  is between 160 and 319 inclusive. If this is true (Yes at text block  306 ), then block  307  sets M RI =2 and N OFFSET,RI =−I RI +160. Method  300  the proceeds to block  319  via links C and D. If this in not true (No at test block  306 ), then method  300  proceeds to test block  308 . 
         [0022]    Test block  308  determines if I RI  is between 320 and 479 inclusive. If this is true (Yes at text block  308 ), then block  309  sets M RI =5 and N OFFSET,RI =−I RI +320. Method  300  the proceeds to block  319  via links C and D. If this in not true (No at test block  308 ), then method  300  proceeds to test block  310 . 
         [0023]    Test block  310  determines if I RI  is between 480 and 639 inclusive. If this is true (Yes at text block  310 ), then block  311  sets M RI =10 and N OFFSET,RI =−I RI +480. Method  300  the proceeds to block  319  via links C and D. If this in not true (No at test block  310 ), then method  300  proceeds to test block  312  via links A and B. 
         [0024]    Test block  312  determines if I RI  is between 640 and 799 inclusive. If this is true (Yes at text block  312 ), then block  313  sets M RI =20 and N OFFSET,RI =−I RI +640. Method  300  then proceeds to block  319 . If this in not true (No at test block  312 ), then method  300  proceeds to test block  314 . 
         [0025]    Test block  314  determines if I RI  is between 800 and 959 inclusive. If this is true (Yes at text block  314 ), then block  315  sets M RI =40 and N OFFSET,RI =−I RI +800. Method  300  then proceeds to block  319 . If this in not true (No at test block  314 ), then method  300  proceeds to test block  316 . 
         [0026]    Test block  316  determines if I RI  equals 960. If this is true (Yes at text block  316 ), then block  318  determines that no RI signaling will occur. Method  300  then proceeds to end block  320  which ends method  300 . If this in not true (No at test block  316 ), then I RI  is out of range and method  300  proceeds to error block  317 . 
         [0027]    Blocks  305 ,  307 ,  309 ,  311 ,  313  and  315  set M RI  and N OFFSET,RI  according to the received value of I RI . Block  319  enables RI reporting by UE  109  according to the determined values of M RI  and N OFFSET,RI . Method  300  then proceeds to end block  320  which ends method  300 .