Adaptive reception of wireless CDMA signals using empirical detection

The channel characteristics of practical code division multiple access (CDMA) systems are usually unknown and difficult to model accurately. Type-based receivers, without assuming any a priori model, extract signals successfully from background noise. In this paper, we develop type-based receivers that address two major issues in CDMA signal reception: multiple access interference and multipath fading. We first present the type-based receiver with interference suppression capability, assuming the knowledge of the code and timing of the intended user only. We then show that equal-gain combining (EGC) of type-based statistics is the asymptotically optimal technique for diversity empirical detection. Compared with maximal ratio combining of matched filter outputs, the diversity receiver with EGC of type-based statistics assumes less channel knowledge and yields competitive detection performance in Gaussian noise and better performance in Laplacian noise