Adaptive algorithm for a cholesky approximation

Abstract

Data is detected on a plurality of received communications channels in a CDMA wireless communication system. A solution for estimating data of the received communication signals is modeled using a linear system requiring a matrix inversion. Columns or rows of an approximate Cholesky factor are determined. A difference between the determined columns or rows is determined. If the determined difference is less than a threshold, subsequent columns or rows are determined by previously determined columns or rows. The data of the received communication signals is estimated using the approximate Cholesky factor, and the estimate is used to detect data received on the plurality of channels.

What is claimed is:  
     
         1 . A method for detecting data in a code division multiple access (CDMA) wireless communication system, the method comprising: 
 receiving a plurality of communication signals;    modeling a solution for estimating data of the received communication signals using a linear system requiring a matrix inversion;    determining columns or rows of an approximate Cholesky factor;    determining a difference between the determined columns or rows;    if the determined difference is less than a threshold, determining subsequent columns or rows by repeating previously determined columns or rows;    estimating the data of the received communication signals using the approximate Cholesky factor; and    using the data estimate to detect data received on a plurality of received communications channels.    
     
     
         2 . The method of  claim 1  further comprising using the approximate Cholesky factor is used to determine the spread data of the received communications in a user detection process comprising one of SUD or MUD, using one of ZF or MMSE data detection approaches.  
     
     
         3 . The method of  claim 1  further comprising repeating previously determined columns or rows, if a number of previously determined columns or rows exceeds an upper limit.  
     
     
         4 . The method of  claim 1  wherein the linear system is modeled using a minimum mean square error approach.  
     
     
         5 . The method of  claim 1  wherein the linear system is modeled using a zero forcing approach.  
     
     
         6 . The method of  claim 1  wherein the approximate Cholesky factor is lower triangular.  
     
     
         7 . The method of  claim 1  wherein the approximate Cholesky factor comprises a plurality of K by K blocks and K is a number of the received signals.  
     
     
         8 . The method of  claim 6  wherein the approximate Cholesky factor is determined by columns.  
     
     
         9 . The method of  claim 7  comprising using block columns of a multiple equal to one or more L blocks in length where L is the longest length of intersymbol interference.  
     
     
         10 . The method of  claim 1  comprising determining an error between normalized blocks of the columns or rows.  
     
     
         11 . The method of  claim 1  comprising comparing a first determined block of a newly determined column or row to a corresponding block of a previously determined column or row, prior to determining subsequent blocks of the newly determined column or row.  
     
     
         12 . A user equipment comprising: 
 an antenna for receiving a plurality of communication signals transmitted in a CDMA format;    a data estimation device for estimating data of the received communication signals using a linear system requiring a matrix inversion; for determining columns or rows of an approximate Cholesky factor; for determining a difference between the determined columns or rows; if the determined difference is less than a threshold, for determining subsequent columns or rows by repeating previously determined columns or rows; for estimating the data of the received communication signals using the approximate Cholesky factor; and using the estimate to detect data received on a plurality of received communications channels.    
     
     
         13 . The user equipment of  claim 12  wherein the data estimation device uses the approximate Cholesky factor to determine the spread data of the received communications in a user detection process comprising one of SUD or MUD, using one of ZF or MMSE data detection approaches.  
     
     
         14 . The user equipment of  claim 12  wherein: 
 the data estimation device further includes a circuit function for repeating previously determined columns or rows, if a number of previously determined columns or rows exceeds an upper limit.  
 
     
     
         15 . The user equipment of  claim 12  wherein: 
 the data estimation device further includes a circuit function for repeating previously determined columns or rows, if a number of previously determined columns or rows exceeds an upper limit; and  
 the data estimation device compares a first determined block of a newly determined column or row to a corresponding block of a previously determined column or row, prior to determining subsequent blocks of the newly determined column or row.  
 
     
     
         16 . The user equipment of  claim 12  wherein the approximate Cholesky factor is lower triangular.  
     
     
         17 . The user equipment of  claim 12  wherein: 
 the approximate Cholesky factor comprises a plurality of K by K blocks and K is a number of the received signals;  
 the approximate Cholesky factor is determined by columns; and  
 the block columns comprise a multiple equal to one or more L blocks in length and L is the longest length of intersymbol interference.  
 
     
     
         18 . A base station comprising: 
 an antenna for receiving a plurality of communication signals;    a data estimation device for estimating data of the received communication signals using a linear system requiring a matrix inversion; for determining columns or rows of an approximate Cholesky factor; for determining a difference between the determined columns or rows; if the determined difference is less than a threshold, for determining subsequent columns or rows by repeating previously determined columns or rows; for estimating the data of the received communication signals using the approximate Cholesky factor; and using the estimate to detect data received on a plurality of received communications channels.    
     
     
         19 . The base station of  claim 18  wherein the data estimation device uses the approximate Cholesky factor to determine the spread data of the received communications in a user detection process comprising one of SUD or MUD, using one of ZF or MMSE data detection approaches.  
     
     
         20 . The base station of  claim 18  wherein: 
 the data estimation device further includes a circuit function for repeating previously determined columns or rows, if a number of previously determined columns or rows exceeds an upper limit.  
 
     
     
         21 . The base station of  claim 18  wherein: 
 the data estimation device further includes a circuit function for repeating previously determined columns or rows, if a number of previously determined columns or rows exceeds an upper limit; and  
 the data estimation device compares a first determined block of a newly determined column or row to a corresponding block of a previously determined column or row, prior to determining subsequent blocks of the newly determined column or row.  
 
     
     
         22 . The base station of  claim 18  wherein the approximate Cholesky factor is lower triangular.  
     
     
         23 . The base station of  claim 18  wherein: 
 the approximate Cholesky factor comprises a plurality of K by K blocks and K is a number of the received signals;  
 the approximate Cholesky factor is determined by columns; and  
 the block columns comprise a multiple equal to one or more L blocks in length and L is the longest length of intersymbol interference.