Adaptive antenna arrays and equalization techniques for high bit-rate QAM receivers

Adaptive antenna arrays provide wireless communication systems with larger service capacity and higher link quality through frequency reuse and cochan nel-interference rejection. In practice, the propagation environment is non ideal with shadowing, severe stationary, and fast multipath fading. In this paper, the combination of adaptive antenna arrays and equalization techniq ues is employed to achieve reliable high-bit-rate wireless communications i n a multipath, multiinterferer environment. A low-complexity receiver struc ture is investigated for the feasibility of portable wireless communication s applications. The performance of the proposed receiver is analyzed in bot h outdoor and indoor multipath conditions. The simulations show that, altho ugh the adaptive beamformer is capable of canceling long-delayed multipath reflections in the outdoor environment within its degrees of freedom, the a daptive equalizer is mandatory to compensate for the residual of the outdoo r environment or the short-delayed multipath reflections of the indoor envi ronment to achieve a high-quality link and a high data rate. The digital ci rcuits of the proposed receiver are estimated to perform 50 billion operati ons per second (GOPS) of digital signal processing functions, and the gate count is estimated to be 100,000 for a custom integrated circuit implementa tion.