Design And Optimization Of Rendezvous Strategy Based On Channel Hopping In Cognitive Radio Networks

With the rapid development of wireless communication technology,more and more de-vices are connected to the with wireless radio for data transmission.At the same time,people have higher demand for bandwidth,which makes the radio frequency band continue to be exploited and used.As a limited and non-renewable natural resource,radio spectrum will be exploited indiscriminately and will be used less and less until it is exhausted.Therefore,how to make better use of the existing spectrum resources is particularly important.At present,in the management and utilization of spectrum resources,the international common practice is to divide the radio frequency band into authorized band and unautho-rized band.However,it also leads to the unbalanced utilization of spectrum resources.In some authorized bands,the utilization rate of spectrum is very low,while in some unautho-rized bands,the communication signal is very crowded.To solve these problems,the con-cept of cognitive radio(CR)has been proposed,which can automatically sense the "blank band”around the environment for communication between nodes.The premise of com-munication is to establish a connection,which is called rendezvous in cognitive networks.Therefore,more and more attention has been paid to the design of the rendezvous strategy.So far,most of the existing rendezvous strategies are based on two nodes to study and simulate.Although most of these pair-wise rendezvous strategies can be used directly or with minor extensions to achieve rendezvous among multiple nodes,the performance is not satisfying,since these strategies are targeted to pair-wise rendezvous and do not take advan-tage of already rendezvoused nodes.And most of the rendezvous strategies mainly focus on designing channel hopping sequence.Few of them are targeted to improve performance of the rendezvous process based on existing channel hopping sequences.In addition,the switching delay of devices is also an important performance factor in some cases.So as to solve the problems of the existing methods,we propose a group-based rendezvous strategy and an optimization method based on ALOHA protocol.More details are shown as follows:(1)We propose a group-based rendezvous strategy for symmetrical and single-hop cognitive radio network.According to symmetric channel and single-hop network scenarios,we design a group-based model,which increases the diversity of a group attempting to other nodes.This strategy can accelerate the overall performance of rendezvous in a CRN region.(2)We propose an extended group-based rendezvous strategy for asymmetric and multi?hop cognitive radio network.This strategy extends the group-based model so that it can be applied to asymmetric and multi-hop network scenarios.We design an optimized decision-making algorithm in this scenario,which can reduce the total rendezvous time.(3)We propose a time slot optimization algorithm based on channel hopping and ALOHA protocol.The switching delay factor is considered in this algorithm.Also,we calculate the optimal number of time slots to rendezvous using expectation analysis and integer programming,which can improve the reliability and performance of rendezvous pro-cess.We adopt simulation experiment to simulate the rendezvous strategy and optimization scheme in this paper.Compared with the existing strategies,the Average TTR(ATTR)of our strategies is reduced.Our group based strategies have more extensive applicability and can improve the performance of rendezvous greatly.In the optimization strategy based on ALOHA protocol,the optimal number of time slots is obtained,which also has more rendezvous advantages than the random strategy.