Study Of Routing And Transmission In Cognitive Radio Networks

Cognitive radio networks (CRNs), enabling dynamic spectrum access, can improve spectrum utilization significantly and thus attract many researchers’interests. Routing and transmission are key technologies in CRNs. The topic of this thesis comes from the National Natural Science Foundation of China and the topic plays an important role in both theory and practice.This thesis makes the following innovative contributions, based on the comprehensive study of the principles of routing algorithms and transmission schemes in CRNs.For the CRNs with fast varying spectrum availability, we propose a multi-channel spectrum aware opportunistic routing algorithm. The proposed scheme does not depend on pre-setup routes and it fully exploits the benefits of multiple channels. Moreover both packets forwarding and overhearing are used. Also network coding is exploited to enhance the network throughput. Simulation results show that the proposed scheme delivers good end to end performance in CRNs.We propose a random linear coded scheme for batch transmission in single hop CRNs with lossy channels, which can be considered as an alternative to retransmission. The proposed scheme can blur packet information and make the transmission more efficient than that in ARQ based schemes. The batch delay is derived theoretically. The analysis is further validated by simulations. The coded scheme requires less ACK message and thus it is less dependent on feedback channels.Combining opportunistic routing strategy and network coding, we further design and analyze the batch transmission in two hop CRNs. The scheme exploits both packet forwarding and overhearing. The scheme broadcasts different packets over multiple available channels. We derive the batch delay. Simulation results show the good performance of our scheme. The analysis here is helpful to protocol design in CRNs.For single transceiver CRNs with quasi-static spectrum, we propose a maximum flow-segment (MFS) based channel assignment and routing algorithm. We introduce the definition of MFS and the procedure to build MFS. The MFS based channel assignment minimizes the number of channel switches and it is integrated into the routing algorithm with an efficient channel information dissemination method. Simulation results show that the MFS scheme can reduce end to end delay and achieve high and stable throughput.