Signaling method in an ofdm multiple access system

Abstract

A method for reducing the peak-to-average ratio in an OFDM communication signal is provided. The method includes defining a constellation having a plurality of symbols, defining a symbol duration for the OFDM communication signal, and defining a plurality of time instants in the symbol duration. A plurality of tones are allocated to a particular communication device, and a discrete signal is constructed in the time domain by mapping symbols from the constellation to the time instants. A continuous signal is generated by applying an interpolation function to the discrete signal such that the continuous signal only includes sinusoids having frequencies which are equal to the allocated tones.

1 . A communication device for use in a communications system that uses multiple tones distributed over a predetermined bandwidth to communicate data, the device comprising: 
 mapping means for receiving data symbols and mapping the symbols to prescribed time instants in a predetermined time interval to generate a discrete signal including mapped symbols, each mapped symbol corresponding to a discrete point in time;    interpolation means for receiving the discrete signal and generating a continuous signal by applying an interpolation function to the discrete signal, the interpolation function operating on the discrete signal such that a frequency response of the continuous signal includes sinusoids having non-zero values at a first set of tones, the first set of tones being a subset of said multiple tones, the non-zero value at each of said first set of tones being a function of a plurality of mapped symbols corresponding to different discrete points in time, the frequency response of the continuous signal also including zero values at a second set of tones, the second set of tones being different from said first set of tones and being another subset of said multiple tones; and    cyclic prefix means located after the interpolation means for prepending a cyclic prefix.    
   
   
       2 . The device of  claim 1 , wherein the discrete time instants are defined within the range of 0, T/N, 2T/N, . . . , T(N−1)/N, where N is a total number of time instants in the predetermined time interval.  
   
   
       3 . The device of  claim 1 , wherein the frequency tones within the first set of tones are contiguous frequency tones, and the prescribed time instants are equally spaced and uniformly distributed over one symbol duration.  
   
   
       4 . The device of  claim 1 , wherein the frequency tones within the first set of tones are equally spaced frequency tones, and the prescribed time instants are equally spaced and uniformly distributed over a fraction of one symbol duration.  
   
   
       5 . The device of  claim 4 , wherein a fraction of one symbol duration is defined by 1/L where L is the spacing between two adjacent tones in the first set of tones.  
   
   
       6 . The device of  claim 1 , wherein a total number of discrete time instants is greater than or equal to a total number of frequency tones distributed over the predetermined bandwidth.  
   
   
       7 . The device of  claim 1 , wherein the interpolation means further includes storage means for storing the predetermined interpolation functions, and an interpolation function means for retrieving the interpolation functions from the memory and applying the interpolation functions to the discrete signal to generate the continuous signal.  
   
   
       8 . The device of  claim 7 , wherein the interpolation functions comprise a matrix of precomputed sinusoidal waveforms.  
   
   
       9 . The device of  claim 7 , wherein the interpolation functions comprise continuous interpolation functions.  
   
   
       10 . A communication device for generating an OFDM signal having allocated frequency tones distributed over a predetermined bandwidth, the communication device comprising: 
 mapping means for receiving data symbols from a symbol constellation and mapping the symbols to prescribed time instants in a time domain symbol duration to generate a discrete signal of mapped symbols;    interpolation means for receiving the discrete signal and generating a continuous signal by applying an interpolation function to the discrete signal;    wherein the interpolation function operates on the discrete signal such that a frequency response of the continuous signal includes sinusoids having non-zero values at the allocated frequency tones, and zero values at frequency tones other than the allocated frequency tones; and    cyclic prefix means located after the interpolation means for prepending a cyclic prefix.    
   
   
       11 . The communication device of  claim 10 , wherein the allocated frequency tones are associated with a designated transmitter within the communication system.  
   
   
       12 . The communication device of  claim 10 , wherein the allocated frequency tones are contiguous frequency tones, and the prescribed time instants are equally spaced time instants uniformly distributed over one symbol duration.  
   
   
       13 . The communication device of  claim 10 , wherein the allocated frequency tones are equally spaced frequency tones, and the prescribed time instants are equally spaced time instants uniformly distributed over a fraction of one symbol duration.  
   
   
       14 . The communication device of  claim 10 , wherein the interpolation means includes storage means for storing the interpolation function, the interpolation means retrieving the interpolation function from the storage means and applying the interpolation function to the discrete signal to generate the continuous signal.  
   
   
       15 . A communication device for generating an OFDM signal having allocated frequency tones distributed over a predetermined bandwidth, the communication device comprising: 
 mapping means for receiving data symbols from a symbol constellation and mapping the symbols to prescribed time instants in a time domain symbol duration to generate a discrete signal of mapped symbols; and    interpolation means for receiving the discrete signal and generates a digital signal sample vector by applying an interpolation function to the discrete signal;    wherein the interpolation function operates on the discrete signal such that a frequency response of the digital signal sample vector includes sinusoids having non-zero values at the allocated frequency tones, and zero values at frequency tones other than the allocated frequency tones; and    cyclic prefix means located after the interpolation means for prepending a cyclic prefix.    
   
   
       16 . The communication device of  claim 15 , wherein the interpolation means further includes storage means for storing the interpolation function, the interpolation means retrieving the interpolation function from the storage means and applying the interpolation function to the discrete signal to generate a digital signal sample vector.  
   
   
       17 . A device including a processor configured to implement a communications method, the method comprising: 
 providing a time domain symbol duration having equally spaced time instants;    allocating a predetermined number of frequency tones to the communication device;    receiving as input data symbols to be transmitted by an OFDM communication signal;    mapping the data symbols to the equally spaced time instants in the symbol duration to generate a discrete signal of mapped symbols;    generating a continuous signal by applying an interpolation function to the discrete signal, the interpolation function operating on the discrete signal such that a frequency response of the continuous signal includes sinusoids having non-zero values at the allocated frequency tones, and zero values at frequency tones other than the allocated frequency tones; and    sampling the continuous signal at discrete time instants distributed over the time domain symbol duration, to generate a digital signal sample vector; and    prepending a cyclic prefix to the digital signal sample vector produced by sampling the continuous signal after generation of the continuous signal by applying the interpolation function.    
   
   
       18 . The device of  claim 17 , wherein the discrete time instants are defined within the range of 0, T/N, 2T/N, . . . , T(N−1)/N, where N is a total number of time instants in the symbol duration.  
   
   
       19 . The device of  claim 17 , wherein the step of allocating a predetermined number of frequency tones to the communication device further comprises allocating contiguous frequency tones to the communication device.  
   
   
       20 . The device of  claim 17 , wherein the step of allocating a predetermined number of frequency tones to the communication device further comprises allocating equally spaced frequency tones to the communication device.  
   
   
       21 . The device of  claim 17 , wherein said processor is further configured to: 
 map the data symbols to a block of complex data symbols wherein the block of complex data symbols includes odd numbered symbols and even numbered symbols;    phase rotate each even numbered symbol by π/4; and    map the block of complex data symbols to equally spaced time instants in the symbol duration to generate the discrete signal of mapped symbols.    
   
   
       22 . The device of  claim 17 , wherein the processor is further configured to: 
 prepend a cyclic prefix to the digital signal sample vector.    
   
   
       23 . A computer readable medium embodying machine executable instructions for controlling a communications device to implement a communications method, the communications method comprising: 
 providing a time domain symbol duration having equally spaced time instants;    allocating a predetermined number of frequency tones to the communication device;    receiving as input data symbols to be transmitted by an OFDM communication signal;    mapping the data symbols to the equally spaced time instants in the symbol duration to generate a discrete signal of mapped symbols;    generating a continuous signal by applying an interpolation function to the discrete signal, the interpolation function operating on the discrete signal such that a frequency response of the continuous signal includes sinusoids having non-zero values at the allocated frequency tones, and zero values at frequency tones other than the allocated frequency tones; and    sampling the continuous signal at discrete time instants distributed over the time domain symbol duration, to generate a digital signal sample vector; and    prepending a cyclic prefix to the digital signal sample vector produced by sampling the continuous signal after generation of the continuous signal by applying the interpolation function.    
   
   
       24 . The computer readable medium of  claim 23 , wherein the discrete time instants are defined within the range of 0, T/N, 2T/N, . . . , T(N−1)/N, where N is a total number of time instants in the symbol duration.  
   
   
       25 . The computer readable medium of  claim 24 , wherein the step of allocating a predetermined number of frequency tones to the communication device further comprises allocating contiguous frequency tones to the communication device.