New Nonlinear Detector for Interference Cancellation in Spread Spectrum Overlay Systems

Overlaying spread spectrum systems on narrowband services has been proposed as a way to take greater bandwidth efficients with respect to sparsely narrowband systems. It is shown that, the performance of both narrowband and spread spectrum systems in a overlay situation significantly degraded by each other. This paper presents a new nonlinear detector which enhances the performance of narrowband considerably. In our approach we use maximum likelihood (ML) as maximum entropy, which are two optimal criteria. Computer simulation results show that the proposed detector has much better performance than the conventional matched filter. The estimated narrowband signal can be subtracted from received signal in the spread spectrum receiver to enhance its performance