Opportunistic Guard-band-aware Spectrum Assignment under Dynamically Varying Channel Conditions: Optimization Framework

Cognitive radio (CR) technology was proposed as a promising solution for spectrum scarcity problem. Several channel assignment mechanisms were proposed for CR networks with the objective of improving spectrum efficiency. However, most of these mechanisms did not account for the adjacent channel interference (ACI) issue. The negative effects of ACI on network performance can be prevented by adding guard bands (GB). Very few attempts have been made to design GB-aware channel assignment schemes assuming fixed rate per channel. This assumption is not realistic due to channel fading conditions. This paper, proposes an adaptive channel assignment mechanism for multi-channel multi-rate CRNs under dynamically varying channel conditions. Specifically, the channel assignment problem has been formulated as an optimization problem with the objective of minimizing the number of assigned channels and introduced GBs subject to rate demand, link-quality and interference constraints. The formulation is based on providing the appropriate per-block channel assignment with minimum size blocks, which saves more channels for potential future transmissions. Simulation results reveal that our mechanism provides significantly performance improvement compared to previous schemes of fixed rates, showing considerable improvement.