Enhanced robust wireless network QoS control applying adaptive modulation and macroscopic diversity combining techniques

Abstract

We propose a communication system and base station network topology. They apply a constraint-based optimal adaptive modulation algorithm and macroscopic diversity reception combining for enhanced robust wireless network QoS support of reliable broadband mobile data communication services. We extend the adaptive modulation research of S.T. Chung and A.J. Goldsmith (see IEEE Trans. Commun., vol.49, no.9, p.1561-71, 2001) in two ways. First, the lognormal shadowing channel characteristic is included in addition to Rayleigh fading. Second, a macroscopic selection diversity scheme is combined with an adaptive modulation topology to enhance the instantaneous BER and spectral efficiency performance. The results show that optimal adaptive modulation control combined with macroscopic diversity enables QoS constraint-based services to be supported more reliably over a wider range of SNR conditions. Also, the macroscopic diversity selection scheme results in a significant improvement in the spectral efficiency. Wireless data link utilization can be increased while the required BER can be supported. Macroscopic diversity combining enables the adaptive modulation to provide more robust/reliable network QoS support under time varying channel conditions (i.e., as the SNR may fluctuate). As the number of combining diversity links increase, the minimum SNR limit that supports the instantaneous BER requirements is significantly lowered, thus making the wireless networking channel QoS and supportive data rate more robust/reliable.