Efficient Peak Cancellation Method for Reducing the Peak-To-Average Power Ratio in Wideband Communication Systems

Abstract

An efficient peak cancellation method for reducing the peak-to-average power ratio in wideband communication systems uses repeated clipping and frequency domain filtering to achieve a desired peak-to-average power ratio for wideband code division multiple access and orthogonal frequency division multiplexing signals. The maximum magnitude of the filtered pulse is determined by a scaling factor which permits eliminating several iterations while still achieving convergence to the targeted peak-to-average power ratio, thereby reducing computational load and saving hardware resources. This results in improved performance in terms of error vector magnitude, adjacent channel leakage ratio and peak-to-average power ratio.

1 . A method for reducing peak-to-average power ratio in wideband communication systems using multiplexing modulation techniques comprising the steps of:
 (a) clipping a baseband input signal;   (b) subtracting the baseband input signal from the result of said step (a);   (c) noise shaping the result of step (b);   (d) scaling the result of the said step (c); and   (e) subtracting from the result of step (d) the delayed baseband input signal.   
   
   
       2 . The method of  claim 1  wherein steps (a) to (e) are iterated until a desired clipping level is achieved. 
   
   
       3 . The method of  claim 1  wherein the clipping step includes using at least one of a group comprising an amplitude calculator, a comparator, a lookup table, a multiplier, a constant and a multiplexer. 
   
   
       4 . The method of  claim 1  wherein the noise shaping step is performed by converting the digitally clipped signal to a frequency domain signal, filtering by at least one finite impulse response filter, reconverting the filtered frequency domain signal to the baseband signal, and combining to yield an output signal. 
   
   
       5 . The method of  claim 1  wherein said step (c) is performed by converting the digitally clipped signals for multi-carrier such as WCDMA to frequency domain signals by (ω n ), filtering by finite impulse response filters, reconverting the filtered frequency domain signals to the baseband signals, and combining the signals. 
   
   
       6 . The method of  claim 1  wherein said step (d) is performed by scaling in accordance with the following equation: 
     
       
         
           
             
               α 
               
                 ( 
                 i 
                 ) 
               
             
             = 
             
               
                 max 
                  
                 
                   ( 
                   
                      
                     
                       p 
                       m 
                       
                         ( 
                         i 
                         ) 
                       
                     
                      
                   
                   ) 
                 
               
               
                 max 
                  
                 
                   ( 
                   
                      
                     
                       pf 
                       n 
                       
                         ( 
                         i 
                         ) 
                       
                     
                      
                   
                   ) 
                 
               
             
           
         
       
     
     wherein α (i)  is a scaling factor at i-th iteration, p n  the clipped signal or peak cancellation signal, and pf n  the output signal of the noise shaper. 
   
   
       7 . The method of  claim 1  further comprising iterating steps (a) to (e) until a desired clipping level is achieved, and wherein the number of iterations needed to converge to the desired PAPR level is reduced by applying a scaling factor. 
   
   
       8 . The method of  claim 6  wherein applying a scaling factor reduces computational load for reducing PAPR. 
   
   
       9 . The method of  claim 6  wherein applying a scaling factor reduces hardware implementation complexity arising from the number of iterations. 
   
   
       10 . The method of  claim 6  wherein error vector magnitude is significantly improved. 
   
   
       11 . The method of  claim 6  wherein adjacent channel leakage ratio is significantly improved. 
   
   
       12 . The method of  claim 6  wherein peak-to-average power ratio is significantly improved. 
   
   
       13 . The method of  claim 1 , further comprising the step of compensating for errors by combining power amplifier output with the signal resulting from step (d) through an additional digital-to-analog converter and an upconverter.