Matched Spread Spectrum Techniques

The design of matched direct-sequence spread spectrum (DS-SS) signals for transmission through slowly fading dispersive channels is considered in this paper. For large processing gains, these signal overcome the channel dispersion and minimize the effect of intersymbol interference (ISI). The matched signals are on the form of quaternary phase modulated (QPM) signals with constant envelopes. Their base-band equivalent are on the form of combined codes with outer components which are the usual spreaded data codes of DS-SS signals and inner components which are binary codes that are matched to the channel impulse response.