On the potential of adaptive antenna combining for intersymbol interference reduction in high speed wireless LANs

The complexity of the equalizer, which is required for high speed wireless LANs, contributes considerably to the equipment cost and power-consumption. It is well known, that adaptive antenna arrays can efficiently reduce intersymbol interference. The application to WLANs introduces two severe problems: (i) the small form factor of the equipment causes strong antenna correlation (ii) to date there are no reliable broadband diversity channel models available for the indoor environment. These problems are addressed in the paper. Our main contributions are: (1) a derivation of the average probability of error of a receiver with a correlated antenna array. This provides fresh insight into the underlying degradation mechanism. (2) Realistic quantitative performance results on the basis of channel measurements rather than channel models by emulation of a coupled dipole linear antenna array. We conclude, that a compact linear dipole array with four /spl lambda//4 spaced elements provides a satisfactory tradeoff between performance and complexity for WLANs. To this end an adaptive array is a viable alternative to an equalizer.