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

In this paper, the proposed communication system and base station network topology apply a constraint-based optimal adaptive modulation algorithm and macroscopic diversity reception combining scheme to support enhanced robust wireless network quality of service (QoS) support for broadband reliable mobile data communication services. The research of this paper extends the adaptive modulation research of [2] by two aspects. First, the lognormal shadowing channel characteristic which are common for mobile communication channels is included in addition to the Rayleigh fading characteristic. Second, a macroscopic selection diversity scheme is combined with the adaptive modulation topology to enhance the instantaneous BER and spectral efficiency performance. The results show that the optimal adaptive modulation control system combined with the macroscopic diversity technology enables QoS constraint-based services to be supported more reliably over a wider range of signal-to-noise ratio (SNR) conditions. Additionally, the results show that by applying the macroscopic diversity selection scheme, a significant improvement in the spectral efficiency is obtained. The analysis illustrates that the wireless data link utilization can be increased while the required instantaneous bit error rate (BER) can be supported. The macroscopic diversity combining scheme 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.