Performance Research On Channel Access Strategy With Heteogeneous Transmission In Discrete-time Domain

Wireless spectrum has been under pressure due to an increasing demand from a large scale wireless applications and mobile-data traffic, wireless spectrum becomes a type of increasingly rare nature resource. With limited spectral resource, dynamic spectrum allocation policy which is oriented to cognitive radio networks have been widespread concerned, to solve the low utilization problem of the wireless spectrum. For centralized cognitive radio networks, combining discrete-time domain queueing modeling, this paper has made theoretical research on the performance and system optimization of master-slave channel access strategy with heterogenous transmission.Firstly, in order to improve the throughput of second user packets and reduce the channel switch overhead, several slots constitute a super-slot. Let primary user packets operate on the super slot unit of time, a channel access strategy with super-slot time structure(SSTS-CAS) is proposed.Secondly, based on the SSTS-CAS strategy, considering the imperfect sensing results of secondary users, a priority queueing model with possible collision is established. Further taking account of the delay of the interrupted secondary user sensed the channel state, arrived at the available channel and exchange the shake hands message, a discrete-time queueing model which secondary user packets can resume the interruption is established at the boundary of a super-slot.Thirdly, for the purpose of decreasing the potential interference to primary users and using the pieces of spectrum effectively, secondary users divide a slot into several mini slots by strength their own equipment. In this way, an secondary user packet can arrive and transmit in mini slots, combining the dispose procedure of the conflict packets, a channel access strategy with mini-slot time structure(MSTS-CAS) is proposed. Considering the character that the disorder channel can’t immediately recover, a queueing model with channel resilience at the boundary instant of a slot is established.Finally, by applying the method of a matrix geometry solution, the stationary probability distribution of three models is given. Combine numerical experiments with analysis and simulation, the tradeoff between the different performance metrics is investigated. By constructor the functions of system reward and cost, the SSTS-CAS and MSTS-CAS strategy are optimization respectively.