Recent analysis of linear multiuser receivers for DS-CDMA signals
has considered signal-to-interference (SIR) performance in large
systems with each user employing random spreading sequences.
Unfortunately, it is only in the special case of the received powers
of all users being equal that a resulting integral equation for
SIR has an explicit solution with demonstrable approximation
accuracy for finite-sized systems. This paper presents an
alternative approach to calculating the SIR performance of MMSE
receivers which relies primarily on the law of large numbers, and
provides an estimate for SIR that is valid for arbitrary
distributions of received interferer powers.