Research And Improvement Of Guaranteed Time Slot Allocation Mechanism In Wireless Sensor Networks

In recent years,the Internet of things develop very fast,related technology of wireless sensor network has been improved greatly and gradually applied to people's production and life.IEEE802.15.4 protocol is a set of standards specially designed for low rate wireless personal area networks,and is widely used in wireless sensor networks.In the IEEE802.15.4 protocol,a guaranteed time slot(GTS)mechanism is provided,which service the time and frequency sensitive data stream specially.According to the IEEE802.15.4 protocol,In the beacon mode,the PAN coordinator allocate GTS in first come first service(FCFS)scheduling policy for devices that made GTS request.However,the GTS allocation method of FCFS has the problems that poor faimessthe,delay requirement is hard to be guaranteed and the scalability of the nodes is low ect.In order to achieve the optimization of the protocol performance,it needs to be improved.According to the problems of requirement of node delay and fairness,this paper proposes a quickly multiple priority GTS allocation mechanism QMPGAS.The allocation strategy is implemented by the SGAP model to achieve the optimal allocation of GTS.The parameters in the SGAP model are the GTS length that request as well as priorities that related to the delay requirements and previous distribution status.The priority of the device node is dynamically changed based on previous allocation status of the device node and the priority of all GTS requests in this super frame.In this way,we can make the device nodes that have not been allocated in the past can have a high priority in this frame which is a good guarantee of fairness.In this paper,the quick multilevel GTS allocation schedule is simulated by MATLAB,the results of delay and fairness are observed and analyzed.Simulation results show that,the fast multilevel GTS allocation method proposed in this paper can improve the fairness of node distribution,and compared with the standard GTS distribution method,the time delay is also reduced.In view of the problem of low scalability,this paper proposes a SSGAS GTS allocation scheme based on time slot sharing.According to the GTS data length that devices requested,do complementation and rounding operation respectively,then grouping the device nodes on the basis of calculation result of rounding operation,within each packet performe knapsack algorithms and filter out the nodes that satisfy the conditions to achieve multiple nodes sharing for multiple time slots in a superframe,so as to improve the utilization of bandwidth,and enhance the scalability of the standard.In this paper,the GTS slot sharing allocation schedule is simulated by MATLAB,the bandwidth utilization and the node throughput in each super frame are observed.By analyzing the simulation results,we can know that,the bandwidth utilization is improved and the number of nodes allocated in each super frame is increased.