Signal processing with channel eigenmode decomposition and channel inversion for mimo systems

Abstract

Techniques for processing a data transmission at a transmitter and receiver, which use channel eigen-decomposition, channel inversion, and (optionally) “water-pouring”. At the transmitter, (1) channel eigen-decomposition is performed to determine eigenmodes of a MIMO channel and to derive a first set of steering vectors, (2) channel inversion is performed to derive weights (e.g., one set for each eigenmode) used to minimize ISI distortion, and (3) water-pouring may be performed to derive scaling values indicative of the transmit powers allocated to the eigenmodes. The first set of steering vectors, weights, and scaling values are used to derive a pulse-shaping matrix, which is used to precondition modulation symbols prior to transmission. At the receiver, channel eigen-decomposition is performed to derive a second set of steering vectors, which are used to derive a pulse-shaping matrix used to condition received symbols such that orthogonal symbol streams are recovered.

1 . In a multiple-input multiple-output (MIMO) communication system, a method for processing data for transmission over a MIMO channel, comprising:
 determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on a water pouring algorithm;   determining, based on a total available transmit power and a sum of inverse signal to noise ratios (SNRs) for the eigenmodes in the set, a total effective power to be distributed across the eignemodes in the set; and   allocating the total available transmit power to the eigenmodes in the set, wherein the transmit power allocated a given eigenmode is based on the total effective power, a cardinality of the set of eigenmodes, and the inverse SNR for the given eignmode.   
   
   
       2 . The method of  claim 1 , wherein determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on the water pouring algorithm comprises omitting, from an initial set of eigenmodes, one or more eigenmodes with transmission characteristics below a threshold value. 
   
   
       3 . The method of  claim 1 , further comprising receiving, as channel state information (CSI) from a receiver, receive noise power parameters to use in calculating the sum of the inverse signal to noise ratios (SNRs). 
   
   
       4 . The method of  claim 1 , wherein the transmit power allocated a given eigenmode is also based on a cardinality of the set of eigenmodes. 
   
   
       5 . The method of  claim 1 , further comprising obtaining the set of eigenmodes by performing channel eigen-decomposition based on an estimated channel response matrix. 
   
   
       6 . An apparatus for multiple-input multiple-output (MIMO) communications, comprising:
 logic for determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on a water pouring algorithm;   logic for determining, based on a total available transmit power and a sum of inverse signal to noise ratios (SNRs) for the eigenmodes in the set, a total effective power to be distributed across the eignemodes in the set; and   logic for allocating the total available transmit power to the eigenmodes in the set, wherein the transmit power allocated a given eigenmode is based on the total effective power, a cardinality of the set of eigenmodes, and the inverse SNR for the given eignmode.   
   
   
       7 . The apparatus of  claim 6 , wherein the logic for determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on the water pouring algorithm is configured to omit, from an initial set of eigenmodes, one or more eigenmodes with transmission characteristics below a threshold value. 
   
   
       8 . The apparatus of  claim 6 , further comprising logic for receiving, as channel state information (CSI) from a receiver, receive noise power parameters to use in calculating the sum of the inverse signal to noise ratios (SNRs). 
   
   
       9 . The apparatus of  claim 6 , wherein the logic for allocating the total available transmit power to the eigenmodes in the set is configured to allocate transmit power to a given eigenmode based on a cardinality of the set of eigenmodes. 
   
   
       10 . The apparatus of  claim 6 , further comprising logic for obtaining the set of eigenmodes by performing channel eigen-decomposition based on an estimated channel response matrix. 
   
   
       11 . An apparatus for multiple-input multiple-output (MIMO) communications, comprising:
 means for determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on a water pouring algorithm;   means for determining, based on a total available transmit power and a sum of inverse signal to noise ratios (SNRs) for the eigenmodes in the set, a total effective power to be distributed across the eignemodes in the set; and   means for allocating the total available transmit power to the eigenmodes in the set, wherein the transmit power allocated a given eigenmode is based on the total effective power, a cardinality of the set of eigenmodes, and the inverse SNR for the given eignmode.   
   
   
       12 . The apparatus of  claim 11 , wherein the means for determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on the water pouring algorithm is configured to omit, from an initial set of eigenmodes, one or more eigenmodes with transmission characteristics below a threshold value. 
   
   
       13 . The apparatus of  claim 11 , further comprising means for receiving, as channel state information (CSI) from a receiver, receive noise power parameters to use in calculating the sum of the inverse signal to noise ratios (SNRs). 
   
   
       14 . The apparatus of  claim 11 , wherein the means for allocating the total available transmit power to the eigenmodes in the set is configured to allocate transmit power to a given eigenmode based on a cardinality of the set of eigenmodes. 
   
   
       15 . The apparatus of  claim 6 , further comprising logic for obtaining the set of eigenmodes by performing channel eigen-decomposition based on an estimated channel response matrix. 
   
   
       16 . A memory unit having software codes stored therein, the software codes executable by a processor for performing operations comprising:
 determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on a water pouring algorithm;   determining, based on a total available transmit power and a sum of inverse signal to noise ratios (SNRs) for the eigenmodes in the set, a total effective power to be distributed across the eignemodes in the set; and   allocating the total available transmit power to the eigenmodes in the set, wherein the transmit power allocated a given eigenmode is based on the total effective power, a cardinality of the set of eigenmodes, and the inverse SNR for the given eignmode.   
   
   
       17 . The memory unit of  claim 16 , wherein determining a set of eigenmodes for the MIMO channel to be allocated transmission power based on the water pouring algorithm comprises omitting, from an initial set of eigenmodes, one or more eigenmodes with transmission characteristics below a threshold value. 
   
   
       18 . The memory unit of  claim 16 , wherein the operations further comprise receiving, as channel state information (CSI) from a receiver, receive noise power parameters to use in calculating the sum of the inverse signal to noise ratios (SNRs). 
   
   
       19 . The memory unit of  claim 16 , wherein the transmit power allocated a given eigenmode is also based on a cardinality of the set of eigenmodes. 
   
   
       20 . The memory unit of  claim 16 , wherein the operations further comprise obtaining the set of eigenmodes by performing channel eigen-decomposition based on an estimated channel response matrix.