Codebook Method for a Multiple Input Multiple Output Wireless System

Abstract

A method for wireless encoding includes encoding wireless multiple input and multiple output signals in accordance with a codebook being one of a discrete codebook restricting elements of codebook entries to be within a predetermined finite set of complex numbers and a constant amplitude codebook including each entry in its codebook having equal column norm and equal row norm. In a preferred embodiment the digital codebook further includes restricting elements of a finite set in the discrete codebook to be in the form of k a +jk b for a base-k computer and the constant amplitude codebook further includes being obtained through a series of successive householder transformations. In a preferred embodiment the codebook is configured as one of a constrained codebook in which the codebook is configured for multiple scenarios and a discrete codebook.

1 . A base station used in a multi-rank beamforming wireless communication system, the base station comprising:
 a precoding unit to precode a signal in accordance with a codebook comprising a plurality of codebook entries per rank, the codebook restricting elements of codebook entries to be within a predetermined finite set of complex numbers, and each entry in the codebook having both equal column norm and equal row norm; and   a transmission unit to transmit the precoded signal to a mobile terminal,   wherein the wireless communication system has at least 4 transmission antennas.   
     
     
         2 . The base station as in  claim 1 ,
 wherein the predetermined finite set consists of numbers in a form of 2 a +j2 b , where a and b are positive integers.   
     
     
         3 . The base station as in  claim 1 ,
 wherein the predetermined finite set consists of numbers in a form of k a +jk b , where a and b are positive integers.   
     
     
         4 . The base station as in  claim 1 ,
 wherein the codebook is obtained through a series of successive householder transformations.   
     
     
         5 . The base station as in  claim 4 ,
 wherein, for 4 transmit antenna communication, the codebook comprises a set of 4 by 1 vectors where elements of each vector are taken from a set of complex numbers in a form of {1, e 2πja     1   , e 2πja     2   , . . . , e 2πja     g   }, and the first element of each vector is 1, where a 1 , . . . , and a g  are complex numbers.   
     
     
         6 . The base station as in  claim 1 ,
 wherein the codebook is configured for multiple scenarios.   
     
     
         7 . The base station as in  claim 6 ,
 wherein the multiple scenarios comprise a different set of channel statistics.   
     
     
         8 . The base station as in  claim 7 ,
 wherein the codebook comprises a union set configuration wherein a union of the set of all channel realizations is taken for all scenarios and the codebook is configured for such union set.   
     
     
         9 . The base station as in  claim 6 ,
 wherein the codebook is obtained through a successive approach wherein the codebook is configured of a smaller size for one scenario.   
     
     
         10 . The base station as in  claim 6 ,
 wherein the codebook is obtained through a successive approach wherein the codebook is configured with fixing designed entries and expanding the codebook by:   adding more entries to the codebook;   configuring new entries responsive to a new scenario and considering a constraint on fixed entries;   fixing all configured entries;   adding more entries; and   configuring the more entries responsive to a next scenario until all scenarios are accounted for.   
     
     
         11 . The base station as in  claim 10 ,
 wherein the codebook is obtained through optimization of the number of codebook entries that are added in each step, and depends on the order in which the scenarios are treated, picking at each step the scenario which requires a smaller codebook for a given performance with respect to other remaining scenarios.   
     
     
         12 . The base station as in  claim 1 ,
 wherein the predetermined finite set of complex numbers consists of {1, −1, j, −j}.   
     
     
         13 . The base station as in  claim 1 ,
 wherein the predetermined finite set of complex numbers consists of {1, −1, j, −j, 1+j, 1−j, −1+j, −1−j}.   
     
     
         14 . The base station as in  claim 1 ,
 wherein the predetermined finite set of complex numbers consists of {±1, ±2, ±j, ±2j, ±1±j, ±1±2j, ±2, ±j, ±2±2j}.   
     
     
         15 . The base station as in  claim 1 ,
 wherein the predetermined finite set of complex numbers consists of {e 2πja     1   , e 2πja     2   , e 2πa     3   , e 2πja     4   }, where a 1 , a 2 , a 3 , and a 4  are complex numbers.   
     
     
         16 . The base station as in  claim 1 ,
 wherein the predetermined finite set of complex numbers consists of {1, −1, j, −j, a(1+j), a(1−j), a(−1+j), a(−1−j)}, where   
       
         
           
             
               a 
               = 
               
                 
                   1 
                   
                     2 
                   
                 
                 . 
               
             
           
         
       
     
     
         17 . A user equipment used in a multi-rank beamforming wireless communication system, the user equipment comprising:
 a receiving unit to receive from a base station a signal precoded in accordance with a codebook comprising a plurality of codebook entries per rank,   wherein the codebook restricts elements of codebook entries to be within a predetermined finite set of complex numbers and each entry in the codebook has both equal column norm and equal row norm, and   wherein the wireless communication system has at least 4 transmission antennas.   
     
     
         18 . A method implemented in a multi-rank beamforming wireless communication system, the method comprising:
 transmitting from a base station to a user equipment a signal precoded in accordance with a codebook comprising a plurality of codebook entries per rank,   wherein the codebook restricts elements of codebook entries to be within a predetermined finite set of complex numbers and each entry in the codebook has both equal column norm and equal row norm, and   wherein the wireless communication system has at least 4 transmission antennas.