Noncoherent Spread Spectrum Receiver with Joint Detection and Synchronization using modified Matched FIR Filters

Abstract

A noncoherent direct sequence spread spectrum DPSK receiver (DPSK-DSSS) is presented. The receiver is designed to operate in heavy multipath environment with a high number of multipath components and variable fade rates. Asynchronous despreading of the received signal by two complementary modified matched FIR filters is followed by a joint data detection, and bit synchronization. Data detection is based on the nonlinear postdetection diversity combining of the two FIR filter outputs. Bit synchronization is achieved by estimating the moment of the combined nonlinear weighted matched filter outputs over a window. The receiver is insensitive to various power delay profiles with severe multipath components. Fast synchronization within several databits is achievable which results in low delay of the datastream and fast startup. The performance of the receiver is evaluated using the discrete channel model proposed by Saleh et. al 11] using parameters extracted from measurements made in a large factory hall [2]. The variation of the BER performance is less than 2 dB over a range of different multipath channels assuming a delay spread of 1/10 the databit time.