Multi-symbol detection for biorthogonal signals over Rayleigh fading channels

A new practical coherent detection scheme for biorthogonal signals, which uses multi-symbol observation interval, is proposed and its performances are analyzed and simulated. The technique jointly estimates both the demodulated data and the channel from received signal only while reducing computation complexity by an approximate maximum-likelihood sequence estimation rather than symbol-by-symbol detection as in previous noncoherent detection. The scheme achieves performance close to that of ideal coherent detection with perfect channel estimates when select the appropriate observation symbol interval N in the given symbol alphabet size M. What is particularly interesting is that the required average signal-to-noise ratio per bit gamma(b) can be reduced by as much as 1.4 dB and the capacity can be increased by as much as 38% when we use this system in the CDMA cellular reverse link.