Research On Reliability Analytical Models Of Vehicular Safety Communication And Safety Application Based On DSRC

Intelligent Transportation System(ITS)can effectively solve the traffic safety issue caused by the growing number of vehicles on the road.One of the key underlying technologies for ITS implementation is the Vehicular Ad-Hoc Network(VANET).Dedicated Short-Range Communication(DSRC)technology is utilized exclusively in the construction of VANET to provide broadcast services of safety messages for safety applications.Safety applications require reliable VANET communication,so safety communication reliability research is one of the critical research areas in VANET.The reliability metrics quantify the ability of safety messages to be successfully received by neighboring nodes.According to the IEEE 802.11 p protocol,the vehicles in the DSRC adopt the Carrier Sense Multiple Access with Collision Avoid(CSMA/CA)mechanism to access the channel,and interference caused by the hidden terminal and concurrent transmission will reduce the Signal-to-Interferenceplus-Noise Ratio(SINR)of signal,resulting in broadcast messages cannot be successfully received by neighbor nodes.The SINR distribution is vital in quantifying VANET reliability.However,it is difficult to derive.The deterministic distance-based reliability analysis model does not consider the SINR distribution,and has the characteristics of simple modeling and efficient operation,and has been widely used.The work on derivation of the SINR distribution and reliability assessment is cutting-edge research in DSRC safety communications.In this paper,the Nakagami channel fading model is used to represent the signal fading during propagation,and three different modeling methods are applied to analyze the reliability of the safety communication under the influence of interference and the channel fading,and build a reliability analysis model for DSRC safety applications by considering that the impact of the vehicle speed on the reliability of safety applications via the tolerable time of the safety application.The specific innovations and research work of the paper is as follows.First,a deterministic distance-based reliability analysis model for d-dimensional(d D,1 ≤d ≤ 3)wireless broadcast networks is proposed to address the problem that the current reliability analysis of d D wireless network broadcasts only considers the influence of channel fading but not the influence of interference.The model takes the interference caused by the hidden terminal problem into account.It is assumed that the impact of the hidden terminal problem and channel fading on reliability are independent.The reliability condisering the influence of channel fading is obtained by the Nakagami distribution.The challenge in assessing the impact of the hidden terminal problem on reliability in a d D network scenario is determining the size of the hidden terminal region that affects the reliability metrics.The model derives a closed-form expression for the size of the hidden terminal region affecting the point-to-point Packet Reception Probability(PRP),solves the size of the hidden terminal region affecting the Packet Delivery Rate(PDR)using a Monte Carlo method,and controls efficiency and accuracy through the statistical relationship between the number of sampling points and the relative error.Finally,cross-validation experiments with NS2 simulations validate the model’s adaptability to one-dimensional(1D),two-dimensional(2D),and three-dimensional(3D)network scenarios.Second,a SINR distribution probabilistic derivation-based reliability analysis model using ordered statistics is proposed to address the problem that models that use unordered statistics to derive SINR distributions are computationally inefficient and difficult to extend to2 D intersection scenarios.The model reduces the computational complexity of the SINR distribution by using ordered statistics to derive the interference distance distribution and the reception distance distribution and further reduces the computational complexity of the model by considering the more general Non-Homogeneous Poisson Process(NHPP)node distribution.At the same time,the model considers the effect of noise on reliability.In addition,the model based on the SINR probability derivation is extended to estimate reliability in a 2D intersection scenario by combining more interference regions.Finally,the efficiency and accuracy of the model are verified by cross-validation experiments with models that employ unordered statistics and with NS2 simulations.Third,aiming at the problem that the model based on the effective distance to calculate the SINR distribution may overestimate the impact of interference,the maximum interference range is introduced into the reliability evaluation framework,and a reliability analysis model based on the effective distance constrained by maximum interference range to calculate the SINR distribution is proposed.First,NS2 simulation is used to obtain the interference distance distribution,and the setting expression for the maximum interference range is given.On the one hand,the model turns the derivation of SINR distribution into a computationally efficient estimate of the likelihood of a node transmission in the effective interference range.On the other hand,to improve the evaluation accuracy,the effective interference range is constrained to the maximum interference range.By incorporating more interference regions,the model is then extended to evaluate reliability in 2D intersection scenarios.Finally,cross-validation experiments with NS2 and model comparison experiments show that the model can perform the reliability evaluation for different interference range scenarios.Fourth,a reliability analysis model for DSRC vehicular safety applications is proposed to address the problem that the existing models for evaluating the reliability of safety applications do not consider the impact of vehicle speed.The reliability of the safety application depends on the reliability of the safety message broadcast and the safety application’s tolerable time.First,the model uses Greenshields linear model to map vehicle speed to vehicle density,and then it derives the reliability of safety message broadcasting at different vehicle speeds.Next,the vehicle speed is applied to the tolerable time of the safety application to calculate the reliability of the safety application.Experiments reveal that increased vehicle speeds necessitate quicker Beacon rates to meet the safety application’s Qo S requirements.The model is useful for measuring the impact of vehicle speed on the reliability of safety applications and guiding the optimization of communication parameters at various vehicle speeds.