Adaptive spread spectrum receiver for mobile communications

The authors illustrate the performance which can be achieved using DSP devices to process the received spread spectrum signals. A spread spectrum receiver is inherently capable of resolving the received signal into multipath components with a resolution determined by the signalling rate (often termed the chip rate). The large bandwidth of a spread spectrum signal and the channel dispersion gives rise to frequency selective fading which implies that each resolved multipath component will fade independently of the adjacent components. The receiver described comprises of two elements, the correlator and the RAKE filter. The correlator uses the same pseudo-noise (PN) code used by the transmitter in order to 'despread' the signal, and consequently resolves the multipath components. The RAKE recombines these components using an adaptive FIR filter. The correlator is effectively a filter matched to the PN signal, and the RAKE is a filter matched to the channel. >