Dynamic Spectrum Access to Improve Fairness in Tactical Networks with Mobile Base Stations

In traditional cellular networks with fixed base stations, spectrum access is static and deterministic. However, networks with mobile base stations require dynamic spectrum access so as to avoid interference caused by mobility of a mobile base station. Recently, several dynamic spectrum access schemes using cognitive radio, which opportunistically accesses available spectrums, have been proposed to address the problem. These schemes, in general, sense unused spectrums using cognitive radio functions and allocate them to mobile base stations requesting spectrum. Then, if there is no spectrum available, the mobile base station requesting spectrum bands should drop the request and wait until unused spectrums appear. This will result in significant unfairness with respect to the resource access especially when mobile base stations are densely located. We model the opportunistic spectrum access scheme with a Markov chain and show the unfairness problem. Motivated by the unfairness of the opportunistic scheme, we propose a distributed dynamic spectrum access scheme based on sharing spectrum bands in the time domain, not only to avoid interference caused by the mobility of mobile base stations, but to ensure that all mobile base stations located in the same interference range can fairly access spectrum bands at a certain period in time. The results of numerical analysis and simulation show that the proposed scheme can achieve fairness without degrading the overall network performance compared with a conventional opportunistic spectrum access scheme.