Research Of Cognitive Radio Ad Hoc Networks Based On Scale-Free Theory

In modern communication,cognitive radio has demonstrated its strong vitality.The combination of cognitive radio and self-organizing network conforms to both the characteristics of cognitive radio and the requirements of self-organizing network.Consequently,the concept of cognitive ad hoc network(CRAHNs)was born.Because of its strong adaptability,cognitive radio ad hoc networks can be used in various network scenarios,such as earthquake relief network,Internet of things,etc.Its dynamic network topology is an important factor that affects its network performance.And that is why it's necessary to study the network topology of the CRAHNs.Because the CRAHNs has a series of complex network characteristics,and scale-free network topology has perfect resistance to random attacks,the application of scale-free network theory to the topology of CRAHNs will enhance the robustness of its network topology.Based on the above analysis,the following aspects are mainly studied in this thesis:Firstly,this thesis studies the background of CRAHNs and scale-free network theory,and besides emphatically introduce the statistical characteristics of complex networks as well as the analysis of basic network models.Subsequently,this thesis has done related research on the topology of the CRAHNS based on the scale-free theory.Based on the BBV scale-free network model,combined with the limited energy and communication range of the cognitive node in CRAHNs,this thesis proposes a CRAHNS topology evolution algorithm based on weighted scale-free network in consideration of the energy consumption of the cognitive nodes and the occupancy of the primary user node.Through the simulation analysis of the algorithm,it is concluded that the topology model constructed based on this algorithm has a better ability to resist random attacks,and prolongs the network life period to a certain extent.At the same time,because of its small-world characteristics,the topology model also has a high data transmission efficiency.Then,on the basis of the above model,the CRAHNs topology model based on BBV model is improved,and a CRAHNs destructiveness optimization algorithm is proposed.Because the network resistance to deliberate attack is not strong,based on this problem,a solution is proposed:the random connection strategy of CRAHNs survivability optimization algorithm.Because of the coexistence of random edging and selective edging,the network topology model has the characteristics of both scale-free network and random network.Therefore,this model can not only well resist network failures caused by random attacks,but also improve the resistance of network to deliberate attacks to a certain extent.Then the simulation analysis of the proposed topology evolution model is carried out and finally the simulation results indicate that the newly proposed algorithm has better resistance to deliberate attacks.