Research On Channel Scheduling And Routing Algorithms In Cognitive Wireless Sensor Networks

Cognitive Radio Sensor Network provides a new opportunity for the development of traditional wireless sensor networks.The spectrum resources can be fully utilized by using the cognitive ability of sensor nodes,at the same time,the communication competition is reduced and the throughput is improved.However,there are also some new problems which are mainly manifested in resource scheduling and resource overhead.It is a great challenge for the resource-constrained wireless sensor networks.This paper focus on the MAC layer,network layer and their cross-layer of cognitive radio sensor networks with cognitive characteristics.The main work is as follows:In the aspect of channel rendezvous mechanism,we propose a rendezvous algorithm based on channel usage probability.This algorithm is designed to realize channel communication scheduling between pairs of users based on MAC layer.The node state is scheduled according to the different channel hopping sequences of sending state and the receiving state.The logical channel is designed based on the channel usage probability,and then mapping to the physical channel.This algorithm realizes the full rendezvous and reduces the maximum time to rendezvous.In the aspect of channel allocation mechanism,we propose a channel scheduling algorithm based on maximum throughput.In event-driven cognitive radio sensor networks,nodes start from event trigger area and cluster among nodes of different levels.On the basis of clustering,we adopt a novel channel scheduling scheme,which gives full play on the cognitive characteristics of CRSN nodes.This mechanism ensures that different channels can be used to transmit data between the same layer nodes with competitive relationship in order to enhancing the concurrency of data transmission.The utilization of idle channel and the throughput of network are greatly improved.In the aspect of fair resource scheduling,we propose a fair channel resource scheduling algorithm based on channel rendezvous.The algorithm schedule resources fairly at the node level and channel level based on the cross-layer of MAC-network of CRSN.Firstly,we construct a multi-fork communication tree with Sink node as the root.The node selects the next hop father node to communicate in the network layer.The algorithm does not use the control channel in neither initialization process nor the specific communication process.In the process of communication,the Rendezvous mechanism in MAC layer is used to generate the sending or receiving channel hopping sequence according to the selection of subsequent nodes.The generated sequence ensures not only the fair allocation of channel resources within the node,but also the fair scheduling of the resources between adjacent nodes with the same channel competition.In the aspect of channel rendezvous routing,we propose a cross-layer clustering routing algorithm based on channel hopping sequence.The rendezvous mechanism of MAC layer in CRSN is combined with the clustering mechanism of network layer to carry out channel allocation and data transmission.The multi-level clustering method is adopted based on the direct routing clustering mechanism.The primary cluster head and the secondary cluster head communicate by the channel rendezvous mechanism.The secondary cluster head and the cluster member communicate by the optimal matching mechanism of weighted bigraph,which reduces the overhead caused by channel switching and the channel competition conflict.The results of these algorithms reduce the number of CRSN spectrum switching,prolong the lifetime of CRSN network,and improve the network throughput.This paper has important theoretical value and practical application significance for CRSN in military and civil fields such as telemedicine,home monitoring,emergency network,factory automation and so on.