Intersymbol interference equalization with adaptive antenna arrays: on the impact of combiner imperfections

In high speed digital mobile communication systems (e.g. wireless LANs) adaptive antennas are a key technology to low cost/low power systems, because they can replace the computationally demanding (temporal) equalizer. To this end it is very important however to understand the impact of combiner imperfections on the performance, because any over-specification will increase hardware cost and power consumption. The main contribution of the paper is a new analysis of the impact of combiner imperfections on the worst case signal to noise plus intersymbol interference ratio (SINR). This analysis provides deep insight into the degradation mechanism. We give an exact analytical expression for the worst case SINR of a zero forcing combiner and an extremely tight approximate bound for the minimum mean squared error combiner. The analysis serves as starting point to optimize the combiner for robustness