The Key Technology Research Of Multi-hop Wireless Networks Based CR

Cognitive radio (CR) technology could realize channel multiplexing in terms of time, frequency and spatial domain because of its higher spectrum utilization. CR uses the way of opportunistic spectrum access, and makes full use of limited spectrum resources for dynamic spectrum sharing. The bandwidth and frequency restrict the development of wireless communications, CR technology which represents the new development of communication has great prospect in the future. In this dissertation, we mainly study dynamic spectrum allocation technique in CR networks, which achieves the highly-efficient utilization of spectrum resource, decreases packet collision rate in the networks, thus increases communication reliability.In this dissertation, we emphasize on the application of dynamic spectrum allocation in CR based wireless multi-hop network, this problem could be regarded as the optimization problem with constraint conditions. The objective of this problem is to make full use of frequency, and the factors such as interference avoidance, justification, algorithm complexity as well as communication overhead should also be considered simultaneously. In addition, achievable capacity of CR based multi-hop network is analyzed in this dissertation. The main contributions are listed as follows:1) Combine CR technology and wireless multi-hop network, the authorized nodes could set up a relay link between itself and the receiver to make sure data could be transmitted by multi-hop relays. We mainly consider the network with random authorized nodes and cognitive nodes, and a QoS guaranteed channel allocation is proposed according to the relay transmission of dynamic spectrum allocation nodes, and the multi-hop relay nodes are selected by the upper and lower power thresholds of transmitted nodes. In the proposed algorithm, the QoS of cognitive node is measured in terms of channel allocation intervals as well as channel utilization periods.2) Introduce Multiple-input-multiple-output (MIMO) technology into CR multi-hop networks. A CR based multi-hop network model is constructed in the dissertation. In this model, we discuss the capacity of CR multi-hop networks with QoS requirement, and the approximate expression of the capacity of CR based multi-hop networks is derived in detail. It is indicated that, with the increasing of CR relay numbers, the achievable capacity improves obviously under the constrained SNR. Meanwhile, the proposed scheme could obtain higher capacity gain in the low SNR region.