Patent ID: 6519275
Filing Date: 2003-02-11
Classification: H04B

Abstract:
A communication system comprising:a transmitter for generating a transmitted modulated signal, said transmitter comprising: a differential encoder for receiving an input data symbol and producing a differentially encoded symbol; a memory for storing a code sequence; a shifting means for time-shifting said code sequence by a time-shift, said time-shift being determined by said differentially encoded symbol, said shifting means being coupled to said memory and generating said transmitted modulated signal; and a receiver for decoding a received modulated signal, said receiver comprising: a shift register for receiving the received modulated signal and generating time-shifted versions thereof; a correlator for determining the correlation between the time-shifted received modulated signals and a code sequence; a means for determining a time-shift that maximizes the correlation between the time-shifted received modulated signals and the code sequence; and a differential decoder for determining an output data symbol as the difference between time-shifts that maximize the correlation between successive time-shifted received modulated signals and the code sequence; and wherein said input data symbol takes one of N values and said differential encoder comprises a delay unit for storing a previous differentially encoded symbol and a modulo-N summer for summing the input data symbol with the previous differentially encoded symbol.