Field Measurements of High Speed Qam Wireless Transmission Using Equalization and Real-time Beamforming

This paper reports on field measurements of indoor high speed (10 Mbps to 30 Mbps) wireless data communications realized with a flexible M-QAM prototype featuring a real-time adaptive equalizer and a high speed real-time adaptive beamformer (smart antenna array). The wireless testbed operates at a carrier frequency of 2.44 GHz, transmits 1 or 10 mW of power in a 5 MHz band and delivers 10, 20 or 30 Mbps by changing the constellation size between 4-, 16and 64-QAM, respectively. An extensive set of measurements, 7560 trials in all, were carried out using different equalizer and beamformer configurations. The results underscore the dramatic potential for a system that optimally combines equalization with adaptive beamforming. For example, an improvement of 43% (from 48% with equalization only to 5% with combined equalization and beamforming) was observed in the outage performance (uncoded BER of 10) of a 20 Mbps system operating in between 2 rooms. The same 20 Mbps system operating within a single room showed an outage of 2% (BER=10) with combined equalization and beamforming, 16% with beamforming only, 33% with equalization only, and 95% with simple demodulation. Additional field measurements at 10 Mbps and 30 Mbps presented in this paper corroborate this trend.