Method and apparatus for performing digital communications

Abstract

A wired and wireless communication method, and more particularly a method and apparatus for reducing a PAPR (Peak to Average Power Ratio) in an OFDM (Orthogonal Frequency Division Multiplexing) system. A transmitter of the OFDM system designates, as a coset leader, a vector capable of minimizing a PAPR in a general standard array of (n, k) linear block codes and transmits a sequence having a minimum PAPR by adding each coset leader to an n-bit codeword corresponding to k-bit information and producing U (≦2 n-k ) number of vectors. Then, a receiver of the OFDM system can easily recover an original transmission signal using a syndrome of a received vector if the receiver identifies information of the syndrome and the coset leader. Subsequently, the OFDM system can be designed irrespective of the number of carriers, i.e., N, and enhance the system's performance by increasing a value of U. Moreover, the OFDM system different from the conventional SLM (Selective Mapping) system does not have to transmit, to the receiver, information indicating which signal has been selected.

1 . An OFDM (Orthogonal Frequency Division Multiplexing) receiver, comprising: 
 an N-point DFT (Discrete Fourier Transform) circuit for transforming a signal produced by sampling a received baseband OFDM signal into a signal x=(x 0 , x 1 , . . . , x N-1 ) consisting of N number of samples through N-point DFT;    an m-ary signal demapper for producing an n-bit binary vector r=(r 0 , r 1 , . . . , r n-1 ) in response to the signal x outputted from the N-point DFT circuit; and    an adder for receiving a syndrome of the binary vector r=(r 0 , r 1 , . . . , r n-1 ) produced using a parity-check matrix H for an (n, k) code and thereby producing a coset leader e i , performing a modulo-2 addition of the binary vector r and the coset leader e i , and producing an n-bit codeword c.    
   
   
       2 . The OFDM receiver as set forth in  claim 1 , further comprising: 
 an ECC (Error-Correcting code) decoder connected to an output terminal of the m-ary signal demapper.    
   
   
       3 . A method for decoding an OFDM (Orthogonal Frequency Division Multiplexing) signal in an OFDM system for dividing an entire signal frequency band into N number of sub-channels which do not overlap and performing frequency division multiplexing, comprising the steps of: 
 (a) transforming a signal produced by sampling a received baseband OFDM signal into a signal x=(x 0 , x 1 , . . . , x N-1 ) consisting of N number of samples in a frequency domain through N-point DFT (Discrete Fourier Transform);    (b) allowing an m-ary signal demapper to produce an n-bit binary vector r=(r 0 , r 1 , . . . , r n-1 ) in response to the signal x;    (c) producing a syndrome of the binary vector r using a parity-check matrix H for an (n, k) code and producing a coset leader e i ; and    (d) producing an n-bit codeword c by performing correction through a modulo-2 addition of the binary vector r and the coset leader e i , and producing a k-bit information block from the codeword c.    
   
   
       4 . The method as set forth in  claim 3 , wherein the step (b) comprises the step of: 
 producing the n-bit binary vector r through an ECC (Error-Correcting code) decoder connected to an output terminal of the m-ary signal demapper.