A study on non-coherent reception of M-ary spread-spectrum signals in the presence of carrier frequency offset

In this paper, we deal with the reception of M-ary spread-spectrum (M-ary/SS) signals in the presence of the carrier frequency-offset. The influence of frequency-offset on reception of M-ary/SS signals is investigated and it is shown that frequency-offset may degrade the symbol-error-rate performance remarkably, yet, the influence has a distinctive property. Making use of this property, we propose a new scheme that can mitigate the influence of the frequency-offset. The scheme is based on the assignment of the two distinctive Hadamard codes to in-phase and quadrature components of the transmitted signal. The selection of the set of Hadamard codes and the power ratio of the in-phase and quadrature component of the transmitted signal is evaluated in terms of symbol-error-rate and carrier frequency offset. As a result we found that the scheme shows the satisfactory symbol-error-rate in the presence of carrier frequency offset up to a half of symbol rate.