An improved bound on the performance of maximum-likelihood multiuser detection receivers in Rayleigh fading

In this correspondence, a new bound on the performance of multiuser receivers in fading channels is presented. The bound is based on a novel criterion for decomposability of error sequences. A constructive method to find the set of indecomposable error sequences under the new criterion is presented. Although the presentation is in the context of a narrow-band multiuser system, the improved bounds can be applied directly to code-division multiple-access (CDMA) multiuser systems over flat-fading channels. A modified bound is also developed for multipath-fading channels. Several examples demonstrate the improved tightness of the new bound, relative to previous results.