Modeling And Performance Research Of IEEE 802.15.4 Protocol In Vehicular Scenarios

Connected vehicle is an emerging technical field which crosses multiple disciplines and industries including automotive, travel, transportation and communications, etc. By connecting vehicles with various devices, services and participants, we are able to make our mobility more enjoyable, sustainable and safe. IEEE802.15.4 protocol is applied for low-rate wireless scenario, whose production and maintenance cost is low. It can be widely used in wireless sensor networks and industrial automation. This thesis studies the performance analysis of IEEE 802.15.4 protocol in vehicular scenarios.This thesis compares the existing modeling methods of IEEE802.15.4 protocol,such as Markov chain, semi-Markov chain, queue theory, and proposes a mathematical model for vehicular scenarios, uses MATLAB to do theoretical simulation to analyze the performance of the protocol in intelligent transportation system. Based on M/G/1 queue theory, the model is applied for star topology with un-slotted CSMA/CA. According to the IEEE 802.15.4 protocol standard, the physical layer packet loss probability is considered, and so is the collision mechanism of MAC layer. Direct transmission model is applied to transmit data, and channel access process is identified by the data packet and ACK packet. After the mathematical model, MATLAB is used to obtain numerical results of the influence of the physical layer packet loss probability and collision mechanism of MAC layer to the packet loss probability and expected delay. Then analyze the performance analysis with the simulation results.Model and simulation results obtain that when the physical layer packet loss probability and collision conflict of MAC layer are within the normal range, such as 0.1 to 0.3, the system loss probability is up to 0.0265, with an average delay of up to 4.25 ms. When the density of the vehicle increases, packet loss probability also increases. Simulation results demonstrate IEEE802.15.4 protocol satisfies the performance requirements of vehicular scenarios within a certain range, and provide more specific data and references for the promotion and implementation of connected vehicles.