On Discrete Sufficient Statistics for Asynchronous Band-limited CDMA Systems

Abstract

The problem of generating discrete sufficient statistics for statistical signal processing in Code Division Multiple Access (CDMA) systems is considered in context of the underlying channel bandwidth restrictions. In most analyses of CDMA systems, the derivation of discrete sufficient statistics is facilitated by first relaxing the bandwidth constraints on the noise and the signaling waveforms in the corresponding continuoustime system model. The validity of this approach is evaluated. In particular, it is shown that relaxing bandwidth constraints in the above fashion can produce inaccurate discrete system models that lead to anomalous results for signal processing in asynchronous CDMA systems. This is illustrated by considering the performance analyses of conventional matched filter detection, minimum mean squared error (MMSE) detection, and delay acquisition in these systems. The role of chip-matched filtering in generating accurate discrete sufficient statistics is also explored. Th..