Topology Control And Spectrum Assignment In Cognitive Radio Network

With the explosion of novel wireless applications,the increasing growth of spectrum requirement has outpaced available spectrum resources.Cognitive Radio Network(CRN)has emerged as a promising solution to address the above dilemma by dynamically sharing spectrum among users.The topology control algorithm and the spectrum assignment are both the key technologies to improve the efficiency of the spectrum.Since primary users(PUs)has priority for the licensed spectrum,secondary users(SUs)must vacate the spectrum when it is reclaimed by the PUs,which will result in the partition of the CR network and harm interference to PUs.The interference among SUs will also cause network performance degradation.In particular,when multiple SUs access the same channel,the nearby simultaneous transmissions will introduce severe interference.To avoid such interference or decrease the influence of these interference,we need to ensure the connectivity of the network and minimum the interference during the channel assignment.In order to decrease these influence to the network performance,we propose the following algorithms to construct robust topology in CRN.(1)At first,we classified and summarized the existing channel assignments,and we gathered the suggestion for the improvement of these algorithms.(2)We proposed the improved CTCA(Centralized Topology Control Algorithm)to maintain the connectivity of the CRNs under the consideration of PUs.In particular,we combine power control and channel assignment to construct a bi-channel connected and conflict-free topology with the minimum number of required channels.Note that,the local spanning tree may be not connected after deleting nodes,we utilize the improved MPH algorithm to make it connected,which philosophy is to give priority to the link on these nodes who have the large path weights,and it's been proved that the improved MPH algorithm can achieve connecting the network while reducing the cost.(3)In addition,we present a k-dominating CDS algorithm to increase the robust of the network.In particular,we will utilize k-dominating sets construction algorithm to build a larger domination of dominating set(DS),and then connect DS by maximizing the lifetime of link,finally we will tailor the size of CDS.Theoretical analysis reveals that our algorithm has higher dominated degree and lower time complexity compared with the C-MLCDS algorithm.The simulation results also verified the superiority of the proposed algorithm.