DS-CDMA reverse link performance with a smart antenna array, fading and imperfect power control

This paper examines uplink (mobile to base station) receiver performance when an optimum combining diversity array is used at the receiver. The multi-access signals are subjected to frequency-nonselective Rayleigh multipath fading as well as lognormally distributed shadow fading and power control error (PCE) in a system employing direct sequence spread-spectrum for code-division multiple-access (DS-CDMA). The receiver consists of an antenna array of ideal isotropic sensors which feeds a bank of optimum combining array processors each of which feeds a conventional matched-filter detector. Multi-access interference from outer cells is also included in the incident signal model. The performance measures are outage probability and outage-based capacity. Results show that a roughly linear relationship exists between the number of array elements and the outage-based capacity. The slope of the capacity line is referred to in the paper as the per element capacity, the capacity increase gained by the addition of a single array element. The per element capacity degrades exponentially with increasing power control error. An approximate analysis results in a simple expression for the outage probability which allows an easy numerical solution for the per element capacity.