Optimal receiver filter design with applications in IS-2000 CDMA systems

In this paper, we propose two approaches to design optimized receiver filters that maximize the signal to interference plus noise ratio of the received signal. The first approach is based on optimizing an MMSE criterion, and provides a closed form analytic solution for the filter coefficients; the second approach is based on the numerical solution of a convex optimization. We introduce the new design methods by their application in IS-2000 CDMA systems. The transmitter plus shaping filter of the CDMA systems (IS-95, IS -2000) is a 48-tap FIR filter (known as IS-95 filter) defined in the standards. The received signal using the matched IS-95 filter has a signal to inter chip interference ratio (SIR) around 16 dB. In 3G and beyond 3G CDMA systems (1XEV-DO, 1XEV-DV), higher SIR of the received signal is required so that high order modulation schemes can be applied to achieve high data transmission throughput. Simulations and lab experiments demonstrate that the receiver filters designed using our methods can significantly improve the system performance by reducing the inter chip interference in comparison to the matched IS-95 filter. The new methods can also be applied in designing short tap length receiver filters in order to reduce the power consumption at the mobile units.