Cognitive Radio Ad Hoc Networks Dynamic Spectrum Access

This paper applied the dynamic spectrum access technology to Ad Hoc network.Firstly, the dynamic transmission power control to the transmitters of the cognitiveradio links is accomplished by an iterative algorithm, which the power and cost ofspectrum utility lost are constrained with each other; the signal-to-interference plusnoise ratio to the signal received are changed as the iteration progressing, so as toadjust the transmission rate of the links to use the spectrum rationally. Secondly, inorder to reduce the interference among the links, an access screening mechanism isproposed. The interference probability distribution is used to describe the uncertaintyof the interference of a cognitive radio link. The information entropy corresponding tothe interference probability is calculated to determine the adaptive interferencethreshold required in the access screening mechanism. The cognitive link with highinterference can be stopped accessing to the spectrum. Finally, the simulation resultsshow that the algorithm above can reduce the total interference of the networkeffectively.However, in the cognitive radio Ad Hoc network, the characteristics of theavailable spectrum are determined by the usage of primary users, and the availablespectrum will be different at each user because of the mobility. So it is necessary toconsider the multi-spectrum access in the network with the existence of primary users.On the basis of the Dynamic Channel Access strategy, this paper proposed aCognitive Channel Access to MAC layer strategy. Firstly, the idle spectrum forcognitive radio users to access is detected by the spectrum detection technology.Secondly, the strategy finds the common available channels between the cognitiveradio users who wanted to communicate with each other, and calculates the sum ofcommon channel utilization by the channel state list, which is maintained by each user.Finally, select the channel with minimum channel utilization sum for datatransmission. The simulation results show that the strategy can make the cognitiveradio users to take full advantage of the unlicensed spectrum, and improve thethroughput of the overall network.