A Study On SPMA Access Protocol For Unmanned Aerial Vehicle Ad Hoc Networks

An UANET is an ad hoc network established by using UAV as nodes in the network.It has a higher task coverage area,more flexible task execution methods,and good scalability than a single UAV.Capabilities are widely used in various military and civilian scenarios.The Statistical Priority-based Multiple Access is adopted as a MAC layer protocol for prioritizing upper data.It is applied in the wireless network with higher requirements on communication quality(like Aviation Ad hoc networks).It prioritizes the upper-layer services by set a threshold to mark the busyness of the channel,learns the current channel load situation through periodic load statistics,determines which priority services can access the channel,and which priorities need to be backed out of the channel.SPMA plays a vital role in ensuring the success rate of first data transmission between nodes,reducing delay,improving channel utilization and system throughput.Based on the in-depth study of the SPMA protocol,this thesis proposes two improved statistical priority multiple access protocols for UAV ad hoc networks to address the problems of the SPMA protocol.The main contents are as follows:1.When the channel load control unit is too large,channel load level may be less than the actual channel load capacity when there is a large amount of traffic,resulting in the waste of channel resources.The back-off time of multiple statistical cycles makes the load control mechanism inflexible and causing idle part of the channel carrying capacity.Setting the full load threshold corresponding to less than 100% of the first packets sent success rate,causes some data packets to be retransmitted,which reduces the system throughput to a certain extent and increases the data end-to-end Delay.Fine-grained Statistical Priority Multiple Access protocol with high channel utilization is proposed.The FSPMA protocol contains three improvement mechanisms: First,the packet load-based channel load control mechanism is used to refine the channel load control unit,thereby efficiently using channel resources,improving channel utilization and system throughput.Secondly,a back-off time setting mechanism based on a single statistical cycle is adopted,so that the system can control the channel access load in time.According to the channel load level calculated,so that the available channel resources can be used in time,and the back-off access channel can be ended in a timely manner at a suitable time.Finally,the full-load threshold optimization mechanism uses an optimized channel full-load threshold determination mechanism to find a unit cycle channel load level closer to 100% of the transmission success rate,thereby improving the transmission success rate,reducing collisions,and delays.The effectiveness of the FSPMA protocol is analyzed theoretically.Simulation results show that the protocol has improved in channel utilization,system throughput,end-to-end delay and data transmission success rate.2.Aiming at the problem that the calculation process of the full-load threshold test is slow,which causes a large increase in system control overhead and an increase in queuing delay,the channel full-load threshold cannot be adaptively adapted to the drone flight environment change.A Low-Delay Threshold Adaptive Access Protocol for UANET is proposed.The LDTA protocol includes two improved mechanisms: First,based on the fast retransmission and fast recovery mechanism,the unicast packet transmission success rate calculated using the ACK message enables the full load threshold to be quickly determined,and the fast convergence of the full load threshold enables the full load The threshold determination time is shortened to reduce the overall delay,so that the system can enter the data transmission state as soon as possible.Second,through the calculation of the unicast packet data transmission success rate and the number of unicast packets sent in multiple statistical cycles,to determine whether the channel carrying capacity of the current network environment has changed,and calculate the transmission success rate within a statistical period,and then the full load threshold is adaptively changed according to the success rate.The self-adaptive full-load threshold keeps the transmission success rate of the system from decreasing when the channel carrying capacity is changed,improves channel utilization,system throughput,and reduces latency.The effectiveness of the LDTA protocol is analyzed theoretically,and simulation results show that the protocol has some improvements in data transmission success rate,channel utilization,and data end-to-end delay.Finally,the full text research work is summarized,and the future research on the SPMA access protocol of the UAV ad hoc networks is briefly described.