Linear and Decision Feedback Equalization Structures for Asynchronous DS-CDMA under ICI
Phil Schniter · 2004
: This paper formulates an asynchronous short-code DS-CDMA system operating under interchip interference (ICI) as a generalization of the fractionally-spaced equalization problem. The model permits straightforward derivation of finite-length MMSE chip-rate linear equalization structures as well as multiuser versions of the DFE. The performance of various equalization structures is compared and observations made. 1 Introduction First, we develop a model for an asynchronous DS-CDMA system that operates under the presence of inter-chip interference. In uplink transmission (i.e., mobile to base station) the chiprate signals asynchronously generated by individual mobiles each see the effect of a different chip-rate FIR channel. In the downlink channel (i.e., base station to mobile), the user signals are generated synchronously and propagate through the same ICI channel on their way to a given mobile. Chip-rate linear filters can be employed at the receivers to estimate the transmitted symb...