Research On User-centric Service-oriented Spectrum Handoff And Channel Selection

In the cognitive radio network,various services require different QoS,and the match between user services and channel characteristics will affect the quality of communication.On the other hand,secondary users also have different delay requirements.Some services are delay-sensitive such as video conferencing and others are non-delay-sensitive such as text messages.Therefore,it is of great importance to set different priorities for secondary users with different service types,so that the QoS of delay-sensitive services can be improved.This thesis studies the service-oriented channel selection and spectrum handoff mechanism in cognitive radio networks.The main contents are as follows:1.Current research on channel selection in heterogeneous cognitive radio networks does not fully consider the diversity of spectrum resources,resulting in mismatching between secondary users' service type and the allocated channel.To solve this problem,a service-oriented channel selection scheme is proposed.Firstly,according to the different requirements of services,a channel selection matching parameter S is designed,which takes into account the differences of users as well as the interference to the primary networks caused by secondary users.S is used to characterize the match of the overall channel selection results,and S is used as the objective function.Further,the improved efficient genetic algorithm is used to optimize the S to maximize the channel selection matching degree.Simulations are conducted from three aspects: the number of algorithm iterations,the probability of occurrence of the primary users and the number of secondary users.Simulation results suggest that the proposed algorithm can allocate appropriate channel resources to a group of secondary users based on their service without causing much interference to the primary network,thus the satisfaction of the system is improved.2.In order to meet the different delay requirements of SUs and improve the channel utilization,a PRP M/G/m queuing theory spectrum handoff model based on classified secondary user is proposed.Firstly,according to the different delay requirements of the service,secondary users are classified into delay-sensitive and non-delay-sensitive users.The delay-sensitive users have higher priority to access the channel.Secondly,PRP M/G/m queuing theory is adopted to establish the spectrum handoff model.At the same time,the extended data delivery time of secondary users with different priorities is deduced and analyzed.Then the adaptive spectrum handoff strategy for secondary users is proposed.Simulation results show that the proposed model can reduce the handoff delay as well as the extended data delivery time,which can effectively ensure the QoS of high-priority secondary users and improve the overall performance.