Research On Multi-hop TDMA Access Protocol For Unmanned Aerial Vehicle Ad Hoc Network

The unmanned aerial vehicle(UAV)Ad Hoc network is a kind of multi-hop network with UAVs as network nodes,which has better adaptability and scalability and is widely used in a variety of military and civilian scenarios.The time division multiple access(TDMA)protocol that makes the packet collision,delay and bandwidth occupation controllable through clear time slot division is widely used in airborne Ad Hoc network as a way of accessing the node channel,which plays a crucial role in data transmission delay of the node,packet success rate and access efficiency.In this thesis,based on the existing multi-hop TDMA protocols and combining characteristics for UAV Ad Hoc network,two improved multi-hop TDMA protocols for UAV Ad Hoc network are proposed.The main research contents are as follows:1.To deal with the problems such as the redundancy control overhead caused by nodes broadcasting time slot allocation message,the repeated forwarding of nodes time slots request message,the influence of the failure of nodes time slots request message transmission to the time slot request,and the number of nodes time slot requests and the topology relationship which are not updated in time,an efficient and low-delay multi-hop TDMA protocol for UAV Ad Hoc network(ELDM-TDMA)is proposed.The ELDM-TDMA protocol includes four improvement mechanisms: Firstly,the time slot allocation information of unnecessary nodes is reduced by using a topology-based simplifying time slot allocation message,thereby shortening the length of control frame and reducing the control overhead.Secondly,the mechanism of information uploading of time slot request which is load-balanced and efficient is adopted.The mechanism selects a node with a smaller load to forward its time slot request information,after that,according to the parent nodes communicating each other,the time slot request information of nodes can be deleted,forwarding times of the time slot request information of the same node are reduced.Then,the mechanism of one-hop nodes secondary allocation of data slots is adopted,when nodes do not send the slot request information successfully,one-hop nodes around the master node allocate collision-free data slots to neighbor nodes without affecting the slot allocation and frame length of the entire network.Finally,The mechanism of updating node time slot request information in time is adopted,which can improve the reliability of data transmission by updating the number of node time slot requests and the topology relationship in real time.The validity of ELDM-TDMA protocol is theoretically analyzed.The simulation results show that the protocol has some improvement in success rate of data transmission,data average delay,control overhead and network throughput.2.To deal with the problems such as the inflexible frame structure of the existing multi-hop TDMA protocol,the single and unfair scheduling strategy and the insufficient use of data slots,time-slot optimization based multi-hop TDMA protocol for UAV Ad Hoc network(TO-TDMA)is proposed.The TO-TDMA protocol includes three improvement mechanisms: Firstly,the length of protocol frame is shortened dynamically by adjusting the length of protocol adaptively,which can reduce the data delay when the network load is heavy.Then,the mechanism of Multi-dimensionally scheduling allocation sequence of node time slot is adopted,which effectively combines multi-dimensional metrics to determine the scheduling sequence of node time slot,and improves the fairness and stability of time slot scheduling.Finally,the mechanism of dynamically using redundant data slots is adopted,this mechanism enables nodes to fully utilize redundant data slots to transmit data frames jointly and improve utilization of time slot.Simulation results show that the TO-TDMA protocol can improve network related performance effectively.Finally,we summarize the whole thesis text and briefly describe the future research direction of the TDMA protocol for UAV Ad Hoc network.