The performance of an optimum digital matched filter detector using structured code sequences for CDMA applications

The paper presents a study of the application of the noncoherent digital matched filter (DMF) detector, with multibit quantisation of the input signal and impulse response, to a digital correlator receiver used in CDMA applications with `structured code´ sequences. The use of structured code sequences with an optimum matched filter produces small crosscorrelation magnitudes. However, such an optimum filter requires a multilevel impulse response and its implementation as a DMF detector requires that the impulse response be quantised and digitised, thereby increasing the filter complexity. In the present study an optimum DMF detector with structured code sequences is evaluated and compared with an equivalent analogue matched filter detector using the signal to noise ratio (SNR) at the correlator output as a performance measure. The results are used to identify the minimum amount of input signal and impulse particular load-sharing response quantisation required in order to reduce circuit complexity while maintaining an acceptable system performance