Routing Optimizations In Cognitive Radio Networks

The cognitive radio network with combining the cognitive radio technology and wireless multi-hop networks has resolved rare spectrum resource and low utilization rate. However, because the spectrum opportunity (SOPs) of cognitive user is dynamic, once the authorized user or transmission performance degradation occurs, cognitive user must switch to a new available frequency band. Which make the routing strategy in the cognitive radio network face many challenges.In this paper, we has studied the whole process that sending the data flows to the destination node in-depth, around the route to find optimal algorithms and scheduling strategy to ensure that inter-node communication in the network with dynamic spectral characteristics and self-organizing can be more stable. Research results obtained by the following aspects:1. According to variability of topology in the multi-hop network and dynamic spectrum features in the cognitive networks, we present a new perspective of flood-based in some angle routing optimization strategy. Under the premise of knowing the location information of source and destination node, broadcasting the routing requests information is no longer in all directions, but along the established direction. Through the NS2 simulation, the improved routing algorithm does significantly reduce the end-to-end delay and packet loss rate.2. After the route is established, as each hop in the routing used for transmission essentially is the available frequency bands allocated by the MAC layer. Once the primary user appears, the band has become unavailable. At this time, if there are other available spectrum bands, the first strategy is directly switching to another available based idle channel; it also can make use of the capability of reconfiguration, the design with ACK-based optimization is represented. The node can adaptively adjust to the most suitable channel to continue communication. And if there are no other available spectrum bands, the idea that in the context of keeping the whole basic routing unchanged, the receiver node select a replacing node in its neighborhood to connect the transmitter node with next hop node, location adjusting the link to avoid the routing reestablished.In summary, firstly, routing optimization algorithm is proposed in this paper; secondly, for the dynamic spectrum, communication frequency is directly switching to another available channel or location adjusting to ensure uninterrupted transmission at the same time, reducing the end to end delay. In order to enhance the overall network performance, the joint between the layers is the future direction of development in cognitive radio networks.