On the channel outage probability of multi-user CDMA systems

Like numerous other applications, novel cross-layer optimization schemes require the determination of the outage probability of fading channels. Relying on the assumption of frequency selective Rayleigh lading channels we develop a closed form expression for the probability density function of the sum of the square channel coefficients at the output of maximum ratio combining (MRC) receivers. This allows for the formulation of the channel outage probability directly in terms of the channel energy and thus enables the analytic derivation of the outage probability in multi-user CDMA systems. Moreover, low complexity lower and upper bounds are derived, which provide the means for a well fitting approximation of the exact result directly through the cumulative distribution of the channel energy as obtained at the MRC output.