Mitigating Interference in the Resource Optimisation for Heterogeneous Cognitive Radio Networks

The cognitive radio network (CRN) has recently gained attention as a lead candidate for next-generation wireless communication. One major reason for this is its promise of alleviating the spectrum scarcity and/or underutilisation challenge. The ideal for achieving CRN's promise is enabling co-use of a given spectrum space by two networks - a primary and a secondary one - either simultaneously or opportunistically, under certain predefined conditions. As remarkable as the CRN's promise is, its main setback is the possibility of poor productivity when the conditions (or constraints) imposed on the users in the secondary network (called secondary users or SUs), by the primary network are stringent. One such constraint, arguably the most limiting and one that is yet to be adequately addressed, is the level of permissible interference to the primary users (PUs) when the SUs are transmitting. In this paper, a resource allocation (RA) solution for heterogeneous CRN that addresses this interference limitation is investigated. The RA is modelled to counteract the limiting effects of the PUs' permissible interference constraint by incorporating an appropriate interference mitigation scheme into the network. The RA problem developed, after reformulation as an integer linear programming problem, is solved using the Lagrangian duality technique and by a heuristic. Comparative results of average data rate and total data rate show significant improvement in the CRN's resource performance when interference mitigation in incorporated, as against when it is ignored.