Method and apparatus for providing antenna diversity in a wireless communication system

Abstract

Transmission schemes that can flexibly achieve the desired spatial multiplexing order, spatial diversity order, and channel estimation overhead order are described. For data transmission, the assigned subcarriers and spatial multiplexing order (M) for a receiver are determined, where M≧1. For each assigned subcarrier, M virtual antennas are selected from among V virtual antennas formed with V columns of an orthonormal matrix, where V≧M. V may be selected to achieve the desired spatial diversity order and channel estimation overhead order. Output symbols are mapped to the M virtual antennas selected for each assigned subcarrier by applying the orthonormal matrix. Pilot symbols are also mapped to the V virtual antennas. The mapped symbols are provided for transmission from T transmit antennas, where T≧V. Transmission symbols are generated for the mapped symbols, e.g., based on OFDM or SC-FDMA. Different cyclic delays may be applied for the T transmit antennas to improve diversity.

1 . An apparatus comprising: 
 at least one processor configured to select M virtual antennas to use for transmission from among V virtual antennas, to map output symbols to the M virtual antennas, and to provide the mapped output symbols for transmission from T transmit antennas, wherein M is equal to one or greater, V is equal to or greater than M, and T is equal to or greater than V; and    a memory coupled to the at least one processor.    
   
   
       2 . The apparatus of  claim 1 , wherein the at least one processor is configured to select different sets of M virtual antennas for different frequency subcarriers from among the V virtual antennas.  
   
   
       3 . The apparatus of  claim 1 , wherein the at least one processor is configured to select a set of M virtual antennas for each of a plurality of frequency subcarriers by cycling through the V virtual antennas.  
   
   
       4 . The apparatus of  claim 1 , wherein the at least one processor is configured to form a permutation matrix indicative of the M virtual antennas selected from among the V virtual antennas, to apply the permutation matrix to the output symbols, and to applying an orthonormal matrix used to form the V virtual antennas.  
   
   
       5 . The apparatus of  claim 1 , wherein the at least one processor is configured to select one virtual antenna from among the V virtual antennas for a first receiver assigned with a first set of frequency subcarriers, to select more than one virtual antenna from among the V virtual antennas for a second receiver assigned with a second set of frequency subcarriers, to map output symbols for the first receiver to the first set of frequency subcarriers of the one virtual antenna, and to map output symbols for the second receiver to the second set of frequency subcarriers of the more than one virtual antenna.  
   
   
       6 . The apparatus of  claim 1 , wherein the at least one processor is configured to apply T different cyclic delays for the T transmit antennas.  
   
   
       7 . The apparatus of  claim 1 , wherein the at least one processor is configured to scale output symbols for the M virtual antennas with M gains.  
   
   
       8 . The apparatus of  claim 1 , wherein the at least one processor is configured to transmit a first pilot on a first virtual antenna among the V virtual antennas, and to transmit a second pilot on remaining ones of the V virtual antennas.  
   
   
       9 . The apparatus of  claim 8 , wherein the at least one processor is configured to transmit the first pilot on a first set of frequency subcarriers of the first virtual antenna, and to transmit the second pilot on a second set of frequency subcarriers by cycling through the remaining ones of the V virtual antennas.  
   
   
       10 . The apparatus of  claim 1 , wherein the at least one processor is configured to transmit pilot symbols on at least one frequency subcarrier in at least one symbol period selected based on a pilot pattern.  
   
   
       11 . The apparatus of  claim 1 , wherein the at least one processor is configured to select an orthonormal matrix from among a plurality of orthonormal matrices available to form the V virtual antennas.  
   
   
       12 . The apparatus of  claim 1 , wherein the at least one processor is configured to receive feedback selecting an orthonormal matrix from among a plurality of orthonormal matrices available to form the V virtual antennas.  
   
   
       13 . The apparatus of  claim 1 , wherein the at least one processor is configured to generate orthogonal frequency division multiplexing (OFDM) symbols for the T transmit antennas based on the mapped output symbols.  
   
   
       14 . The apparatus of  claim 1 , wherein the at least one processor is configured to generate single-carrier frequency division multiple access (SC-FDMA) symbols for the T transmit antennas based on the mapped output symbols.  
   
   
       15 . The apparatus of  claim 1 , wherein the at least one processor is configured to dynamically select M based on channel conditions.  
   
   
       16 . The apparatus of  claim 1 , wherein the at least one processor is configured to dynamically select V based on channel conditions.  
   
   
       17 . The apparatus of  claim 1 , wherein an orthonormal matrix, used to form the V virtual antennas, is defined such that equal transmit power is used for the T transmit antennas.  
   
   
       18 . The apparatus of  claim 1 , wherein an orthonormal matrix, used to form the V virtual antennas, is based on a Fourier matrix or a Walsh matrix.  
   
   
       19 . The apparatus of  claim 1 , wherein an orthonormal matrix, used to form the V virtual antennas is based upon scaling a Fourier matrix or a Walsh matrix with different random phases.  
   
   
       20 . A method comprising: 
 selecting M virtual antennas to use for transmission from among V virtual antennas, wherein M is one or greater and V is equal to or greater than M;    mapping output symbols to the M virtual antennas; and    providing the mapped output symbols for transmission from T transmit antennas, wherein T is equal to or greater than V.    
   
   
       21 . The method of  claim 20 , further comprising: 
 selecting different sets of M virtual antennas for different frequency subcarriers from among the V virtual antennas.    
   
   
       22 . The method of  claim 20 , further comprising: 
 applying T different cyclic delays for the T transmit antennas.    
   
   
       23 . The method of  claim 20 , further comprising: 
 transmitting a pilot on the M virtual antennas.    
   
   
       24 . An apparatus comprising: 
 means for selecting M virtual antennas to use for transmission from among V virtual antennas, wherein M is one or greater and V is equal to or greater than M;    means for mapping output symbols to the M virtual antennas; and    means for providing the mapped output symbols for transmission from T transmit antennas, wherein T is equal to or greater than V.    
   
   
       25 . The apparatus of  claim 24 , further comprising: 
 means for selecting different sets of M virtual antennas for different frequency subcarriers from among the V virtual antennas.    
   
   
       26 . The apparatus of  claim 24 , further comprising: 
 means for applying T different cyclic delays for the T transmit antennas.    
   
   
       27 . The apparatus of  claim 24 , further comprising: 
 means for transmitting a pilot on the M virtual antennas.    
   
   
       28 . An apparatus comprising: 
 at least one processor configured to select M 1  virtual antennas to use for transmission to a first receiver from among V virtual antennas, to select M 2  virtual antennas to use for transmission to a second receiver from among the V virtual antennas, to map output symbols for the first receiver to the M 1  virtual antennas, to map output symbols for the second receiver to the M 2  virtual antennas, to provide the mapped output symbols for the first receiver for transmission on a first frequency subcarrier of T transmit antennas, and to provide the mapped output symbols for the second receiver for transmission on a second frequency subcarrier of the T transmit antennas, wherein M 1  and M 2  are each equal to one or greater, V is equal to or greater than the larger of M 1  and M 2 , and T is equal to or greater than V; and    a memory coupled to the at least one processor.    
   
   
       29 . The apparatus of  claim 28 , wherein the at least one processor is configured to apply T different cyclic delays for the T transmit antennas.  
   
   
       30 . The apparatus of  claim 28 , wherein M 1  is not equal to M 2 .  
   
   
       31 . The apparatus of  claim 28 , wherein the first and second frequency subcarriers are one frequency subcarrier, and wherein transmissions are sent to the first and second receivers using spatial division multiple access (SDMA).  
   
   
       32 . The apparatus of  claim 28 , wherein the at least one processor is configured to transmit a pilot on each virtual antenna used for transmission.  
   
   
       33 . The apparatus of  claim 28 , wherein the at least one processor is configured to generate transmission symbols for the T transmit antennas based on the mapped output symbols and using orthogonal frequency division multiplexing (OFDM) or single-carrier frequency division multiple access (SC-FDMA) modulation technique.  
   
   
       34 . An apparatus comprising: 
 means for selecting M 1  virtual antennas to use for transmission to a first receiver from among V virtual antennas, wherein M 1  is equal to one or greater and V is equal to or greater than M 1 ;    means for selecting M 2  virtual antennas to use for transmission to a second receiver from among the V virtual antennas, wherein M 2  is equal to one or greater and is also less than or equal to V;    means for mapping output symbols for the first receiver to the M 1  virtual antennas;    means for mapping output symbols for the second receiver to the M 2  virtual antennas;    means for providing the mapped output symbols for the first receiver for transmission on a first frequency subcarrier of T transmit antennas, wherein T is equal to or greater than V; and    means for providing the mapped output symbols for the second receiver for transmission on a second frequency subcarrier of the T transmit antennas.    
   
   
       35 . The apparatus of  claim 34 , further comprising: 
 means for applying T different cyclic delays for the T transmit antennas.    
   
   
       36 . An apparatus comprising: 
 at least one processor configured to map output symbols to a plurality of antennas based upon at least one mapping pattern selected from among a plurality of mapping patterns, wherein each mapping pattern indicates a specific mapping of an output symbol to the plurality of antennas; and    a memory coupled to the at least one processor.    
   
   
       37 . The apparatus of  claim 36 , wherein the at least one processor is configured to select different mapping patterns for different frequency subcarriers in a symbol period.  
   
   
       38 . The apparatus of  claim 36 , wherein the at least one processor is configured to select different mapping patterns for symbol periods.  
   
   
       39 . The apparatus of  claim 36 , wherein the at least one processor is configured to select different mapping patterns from among the plurality of mapping patterns for different frequency subcarriers or different symbol periods based on a predetermined pattern.  
   
   
       40 . The apparatus of  claim 36 , wherein the at least one processor is configured to apply a different column of an orthonormal matrix for each of a plurality of frequency subcarriers in accordance with a predetermined pattern, wherein the orthonormal matrix includes a plurality of columns for the plurality of mapping patterns.