Design And Implementation Of Bluetooth Mesh Relay Feature

Bluetooth Mesh network is a multi-to-many,non-centered wireless AD hoc network proposed by Bluetooth Special Interest Group.Bluetooth Mesh network extends the communication coverage and enhances the robustness of the network through the relay feature.However,in the environment of high density of network nodes,relay forwarding will produce redundant packets,aggravate message collision,and further cause serious problems such as network load.Therefore,it is necessary to design and implement a suitable relay forwarding mechanism to solve the problem of redundant packets and message collisions.Based on the above problems,an optimized TTL(Time To Live)processing mechanism is introduced and a delay counting mechanism is designed in the forwarding process of Bluetooth relay feature in the thesis.The optimization of TTL processing mechanism is to process the TTL field of the packet based on the heartbeat packet and Hops value,limit the direction of packet forwarding and reduce invalid forwarding.The delay forwarding and counting mechanism is to introduce random delay time to stagger the forwarding time between nodes,and conduct statistics on consistent packets within the delay time.The number of statistics is compared with the pre-set threshold value k,so as to determine whether the packet can be forwarded.And an adaptive dynamic threshold value k scheme is introduced.Through the above mechanism,the redundant data packets and message collisions are reduced,and the performance of Bluetooth Mesh network is improved.The relay feature based on the Nordic mesh protocol stack,and uses the hardware platform based on the nRF52832 system for test.30 nRF52832 Bluetooth nodes are selected to carry out multi-hop test on the relay feature under the premise of networking,and the performance of Bluetooth Mesh network is tested.The test results show that compared with the Nordic companies Mesh stack,the packet transmission overhead is reduced by 25.3%,and the average end-to-end delay is increased by less than 12%,which reaches the expected design target.The research results are valuable for the application and extension of Bluetooth Mesh.