Cross-layer Design In Cognitive Relay Network

With the evolvement of wireless communication and the explosive growth of wireless service,the embarassment between the scarce spectrum bands and the demand for networks with higher data rate and wider bandwidth has been aggravated and the problem needs to be tackled immediately.Cognitive radio emerges as a promising way to solve the problem,which improves the spectrum utilization by allowing cognitive network to use the authorized spectrum without affecting primary system's communication.By monitoring the operation status of network devices,quality of wireless channels,and changing requirement of user's application,cognitive radio can learn,decide and adjust the operational parameter to achieve adapatibility.However,the traditional layered protocol stack is not that flexible and far from satisfying the requirement.To deal with the problem,the new architecture with much more flexibility and adapatability has to be studied,which means that the layered architecture has to be broken and the boundaries between different layers need to be blureed.Therefore,cross-layer design that permits parameters exchange in non-adjacent layers is put forward.Relaying is a prevailing technology in the next generation wireless communication system.It will play an important role in not only the traditional cellular network but also the multi-hop network.By deploying relays,the system throughput can be enhanced and the coverage of existing network can be extended.Besides,relay can help deploy the temporary communication network.Based on the advantages of cognitive radio and relaying technique,the disseratation will work on cross-layer resource allocation algorithm for cognitive relay networks.Specifically,the paper makes contributions in the following aspects:1.For dual-hop cognitive relay network,relays are introduced into traditional cellular network.The users make the transmission mode selection from either base station or relays based on the available spectrum bands in cellular bands and cognitive bands,the fading effect in wireless channels and the outage probability for data service.What is more,the transmit power is allocated to maximize the spectrum utilization.In view of the optimization objective,a cross-layer algorithm that consists of three stages is proposed,which includes transmission mode selection,relay selection and power allocation,respectively.2.For multi-hop cognitive relay network,the power saving issue is investigated.The cognitive source tranmists to the cognitive destination via multi-hops.To guarantee the end-to-end outage probability between source and destination,the best relay path has to be established and the minimum power needs to be allocated for power saving's purpose.Further,to make sure that the primary system's communication is not interfered,a power budget for each cognitive relay is calculated.Based on these assumptions,the joint Lagrange-dual method based power allocation and objective oriented relay selection algorithm is proposed.3.Architecture for the multi-hop cognitive relay network mentioned in Chapter 3 is proposed.To support the scenario and proposed algorithm,the system architecture is put forward.Detailed function for cognitive node is given and modulars that should be included are demonstrated as well.Finally,from the time scequence's point of view,the signalling process that includes the information exchange is designed to support the mentioned function.