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Design and Evaluation of an Efficient Guard-band-aware Multi-channel Spectrum Sharing Mechanism

Several spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed assuming no adjacent-channel interference (i.e., no interference from neighboring CR transmissions operating over adjacent channels). However, in practice, such an assumption may not hold, and guard bands are realistically needed to prevent interference from neighboring CR transmissions operating on adjacent channels. Introducing guard bands is a restrictive constraint on the effective use of the spectrum. In this work, we investigate the problem of assigning channels/powers to CR transmissions, while accounting for such a constraint. To improve spectrum efficiency and avoid unnecessary blocking of CR transmissions, we propose a novel guard-band-aware channel assignment scheme. The proposed scheme reduces the number of required guard channels for a given transmission by exploiting the benefits of utilizing adjacent channels while considering the already reserved guard channels. We analytically formulate the channel access as a joint power control and channel assignment optimization problem, with the objective of minimizing the required spectrum resource for a given CR transmission. Because the optimization problem is found to be a binary linear program (BLP), which is known to be NP-hard in general, we present a near-optimal algorithm to solve this problem based on a sequential fixing procedure, where the binary variables are determined iteratively by solving a sequence of linear programs. Simulation results are provided, which verify the accuracy of the proposed algorithm and demonstrate the significant gain achieved by being guard-band-aware.