Successive interference cancelation and strongest users detectors for randomly spread DS-CDMA

Abstract

We consider here the problem of multi-user detection for randomly spread direct-sequence (DS) coded-division multiple access (CDMA) over flat fading channels. The analysis is focused on the case of many users, and large spreading sequences such that their ratio, which is the system load, is kept fixed. Spectral efficiency of practical linear detectors such as match-filter and decorrelator employing successive interference cancellation (SIC) at the receiver is derived. This is used to extend the notion of strongest users detectors for SIC receivers. The strongest users detectors system design relies on an outage approach where each user transmits in a single layer (fixed rate). This constraint is relaxed here, and the concept is combined with a broadcast approach, providing higher achievable rates.