Design and analysis of routing and associated transmission schemes in cognitive radio networks

Cognitive radio networks (CRNs) have emerged as an exciting technology to improve spectrum utilization and provide more available bandwidth. In CRNs, cognitive radio (CR) users dynamically access the unused spectrum granted to primary users. Such an opportunistic manner of spectrum access brings unique challenges for efficient communications between CR users. Much of the work on CRNs has focused on the PHY and MAC layer. However, routing design, as a key aspect of networking technologies, plays an important role in improving end-to-end performance for efficient communications between CR users in multi-hop CRNs. In CRNs, primary users' activities result in varying available channel sets for different CR users. Such spatial and temporal variations of channel (spectrum) availability have large impacts on routing design. In this thesis, we first propose a multi-channel spectrum aware opportunistic routing algorithm for multi-radio CRNs with fast varying spectrum availability. In the proposed algorithm transmitters broadcast packets on multiple channels of CR links in order to reduce link delay and end-to-end delay. Additionally, the algorithm does not need a pre-setup route, and takes advantages of the broadcast nature of wireless transmission to overcome the unreliable link due to radio fading. The proposed algorithm delivers low delay and is able to support high traffic load. We then propose a random linear coded scheme for efficient batch transmission over multiple channels between a single-hop communication pair in CRNs. The proposed scheme represents a key component in the network coding based opportunistic routing architecture of this thesis. We develop theoretical analysis and derive batch delays for the proposed scheme and two multi-channel ARQ based schemes. We further extend the analysis to different batch transmission schemes, combined with different routing strategies, in a two-hop CRN. We derive network performance measures of the schemes in terms of batch delay, which provide in-sights into the data transmission capability in multi-channel CRN environment. The proposed scheme is less dependent on feedback channel and reduces batch delay significantly. Finally, we consider a single transceiver multi-channel multi-hop CRN, which is a more practical scenario for low cost implementation. We propose a channel assignment and routing scheme, which minimizes the number of channel switches along a ow. We derive an efficient channel information dissemination algorithm that integrates the channel assignment scheme into the on-demand routing protocol and reduces the routing overhead. The proposed scheme achieves lower end-to-end delay, and higher and more stable throughput.