Measuring IEEE 802.11p Performance for Active Safety Applications in Cooperative Vehicular Systems

Abstract-In this paper, we present a measurement study of application layer performance in IEEE 802.11p vehicular networks. More specifically, our focus is on active safety applications, which are based on the exchange of beacon messages containing status information between close-by vehicles. We consider two performance metrics relevant to active safety applications: the first is application-layer goodput, which can be used to optimize congestion control techniques aimed at limiting the beaconing load on the wireless channel; the second is the beacon reception rate, which is useful to estimate the level of situation awareness achievable onboard vehicles. Our measurements were conducted using a prototypal, 802.11p compliant communication device developed by NEC, in both stationary and mobile V2V scenarios, and disclosed several useful insights on 802.11p application-level performance. To the best of our knowledge, the ones presented in this paper are the first application-level measurements of IEEE 802.11p based vehicular networks reported in the literature

A Measurement-based Study of Beaconing Performance in IEEE 802.11p Vehicular Networks

Active safety applications for vehicular networks aims at improving safety conditions on the road by raising the level of "situation awareness" onboard vehicles. Situation awareness is achieved through exchange of beacons reporting positional and kinematic data. Two important performance parameters influence the level of situation awareness available to the active safety application: the beacon (packet) delivery rate (PDR), and the packet inter-reception (PIR) time. While measurementbased evaluations of the former metric recently appeared in the literature, the latter metric has not been studied so far. In this paper, for the first time, we estimate the PIR time and its correlation with PDR and other environmental parameters through an extensive measurement campaign based on IEEE 802.11p technology. Our study discloses several interesting insights on PIR times that can be expected in a real-world scenarios, which should be carefully considered by the active safety application designers. A major insight is that the packet inter reception time distribution is a power-law and that long situation awareness black-outs are likely to occur in batch, implying that situation awareness can be severely impaired even when the average beacon delivery rate is relatively high. Furthermore, our analysis shows that PIR and PDR are only loosely (negatively) correlated, and that the PIR time is almost independent of speed and distance between vehicles. A third major contribution of this paper is promoting the Gilbert-Elliot model, previously proposed to model bit error bursts in packet switched networks, as a very accurate model of beacon reception behavior observed in real-world data

Evaluation study of IEEE 1609.4 performance for safety and non-safety messages dissemination

The IEEE 1609.4 was developed to support multi-channel operation and channel switching procedure in order to provide both safety and non-safety vehicular applications. However, this protocol has some drawback because it does not make efficient usage of channel bandwidth resources for single radio WAVE devices and suffer from high bounded delay and lost packet especially for large-scale networks in terms of the number of active nodes. This paper evaluates IEEE 1609.4 multi-channel protocol performance for safety and non-safety application and compare it with the IEEE 802.11p single channel protocol. Multi-channel and single channel protocols are analyzed in different environments to investigate their performance. By relying on a realistic dataset and using OMNeT++ simulation tool as network simulator, SUMO as traffic simulator and coupling them by employing Veins framework. Performance evaluation results show that the delay of single channel protocol IEEE 802.11p has been degraded 36% compared with multi-channel protocol

SDDV: scalable data dissemination in vehicular ad hoc networks

An important challenge in the domain of vehicular ad hoc networks (VANET) is the scalability of data dissemination. Under dense traffic conditions, the large number of communicating vehicles can easily result in a congested wireless channel. In that situation, delays and packet losses increase to a level where the VANET cannot be applied for road safety applications anymore. This paper introduces scalable data dissemination in vehicular ad hoc networks (SDDV), a holistic solution to this problem. It is composed of several techniques spread across the different layers of the protocol stack. Simulation results are presented that illustrate the severity of the scalability problem when applying common state-of-the-art techniques and parameters. Starting from such a baseline solution, optimization techniques are gradually added to SDDV until the scalability problem is entirely solved. Besides the performance evaluation based on simulations, the paper ends with an evaluation of the final SDDV configuration on real hardware. Experiments including 110 nodes are performed on the iMinds w-iLab.t wireless lab. The results of these experiments confirm the results obtained in the corresponding simulations

Performance of CAM based Safety Applications using ITS-G5A MAC in High Dense Scenarios

ETSI ITS-G5 is the current vehicle-to-vehicle communication technology in Europe, which will be standardized by ETSI TC ITS. It is based on IEEE 802.11p and therefore uses a CSMA/CA scheme for Media Access Control (MAC). In this paper we analyze the performance of CAM based safety applications using the ETSI ITS-G5 MAC technology in a challenging scenario with respect to MAC issues: A suitable freeway segment with 6 lanes in each direction. The freeway scenario is thoroughly modeled and implemented in the well known ns-3 simulation environment. Based on this model, the paper shows the performance of CAM based safety applications under MAC challenging conditions. Therefore we provide a set of simulation results resting upon a particular performance metric which incorporates the key requirements of safety applications. Finally we analyze two concrete example scenarios to make a point how reliable CAM based safety applications are in high dense traffic scenarios

Agile Calibration Process of Full-Stack Simulation Frameworks for V2X Communications

Computer simulations and real-world car trials are essential to investigate the performance of Vehicle-to-Everything (V2X) networks. However, simulations are imperfect models of the physical reality and can be trusted only when they indicate agreement with the real-world. On the other hand, trials lack reproducibility and are subject to uncertainties and errors. In this paper, we will illustrate a case study where the interrelationship between trials, simulation, and the reality-of-interest is presented. Results are then compared in a holistic fashion. Our study will describe the procedure followed to macroscopically calibrate a full-stack network simulator to conduct high-fidelity full-stack computer simulations.Comment: To appear in IEEE VNC 2017, Torino, I

Multihop Beaconing Forwarding Strategies in Congested IEEE 802.11p Vehicular Networks

Abstract?Multi-hop propagation of situational information is a promising technique for improving beaconing performance and increasing the degree of situational awareness onboard vehicles. A possible way of achieving this is by piggyback information on the beacon packets that are sent periodically by each vehicle in the network, as prescribed by the DSRC and ETSI standards. However, prescribed limitations on beacon size imply that only information about a very small number of surrounding vehicles can be piggybacked in a beacon packet. In most traffic situations, this number is well below the typical number of vehicles within transmission range, implying that multi-hop forwarding strategies must be devised to select which neighboring vehicle?s information to include in a transmitted beacon. In this paper, we designed different multi-hop forwarding strategies, and assessed their effectiveness in delivering fresh situational information to surrounding vehicles. Effectiveness is estimated in terms of both information age and probability of experiencing a potentially dangerous situational-awareness blackout. Both metrics are estimated as a function of the hop distance from the transmitting vehicle, and in presence of different level of radio channel congestion. The investigation is based on extensive simulations whose multi-hop communication performance is corroborated by real-world measurements. The results show that network-coding based strategies substantially improve forwarding performance as compared to a randomized strategy, reducing the average information age of up to 60%, and the blackout probability of up to two orders of magnitude.We also consider the effect of multi-hop propagation of situational information on the reliability of a forward collision warning application, and show that network-coding based propagation yields a factor three improvement of reliability with respect to arandomized forwarding strategy, and even higher improvements with respect to the case of no propagation

Understanding Vehicle-to-Vehicle IEEE 802.11p Beaconing Performance in Real-World Highway Scenarios

Periodic exchange of situational information (beacons) is at the basis of most active safety applications in vehicular environments. Despite its fundamental role in raising the level of "situational awareness" onboard vehicles, very little is known to date on beaconing performance in a real vehicular environment. This paper analyzes the results of two measurement campaigns that have been designed with the purpose of disclosing beaconing performance in a variety of vehicular links, for what concerns vehicle configuration (tall/short), line-of-sight conditions (LOS/NLOS), as well as single-hop or two-hop propagation of the information reported in the beacons. For the first time, beaconing performance is characterized in terms of not only the packet (beacon) delivery rate (PDR), but also in terms of the packet (beacon) inter-reception (PIR) time. The latter metric has been suggested in the literature as more accurately measuring the level of "situation awareness" onboard vehicles than the traditional PDR metric. This paper also presents a simulation-based analysis aimed at estimating the benefit of multi-hop propagation of situational information beyond the second hop of communication. The analysis of the data collected in the measurement campaigns as well as the simulation-based analysis disclose a number of interesting insights which might prove useful in the design of active safety applications. Finally, another major contribution of this paper is promoting the Gilbert-Elliot model, previously proposed to model bit-error bursts in packet switched networks, as a very accurate model of beacon reception behavior observed in real-world scenarios

Multihop Beaconing Forwarding Strategies in Congested IEEE 802.11p Vehicular Networks

Multi-hop propagation of situational information is a promising technique for improving beaconing performance and increasing the degree of situational awareness onboard vehicles. However, limitation on beacon size prescribed by standardization bodies implies that only<br> information about 3-4 surrounding vehicles can be piggybacked in a beacon packet. In most traffic situations, the number of vehicles within transmission range is much larger than 3-4, implying that multi-hop forwarding strategies must be devised to select which neighboring<br> vehicle\u27s information to include in a transmitted beacon. In this paper, we investigate the effectiveness of different multi-hop forwarding strategies in delivering fresh situational information to surrounding vehicles. Effectiveness is estimated in terms of both average information age<br> and probability of experiencing a situational-awareness blackout of at least 1 sec. Both metrics are estimated as a function of the hop distance from the transmitting vehicle, and in presence of different level of radio channel congestion. The investigation is based on extensive simulations<br> whose multi-hop communication performance is corroborated by real-world measurements. <br> The results show that network-coding based strategies substantially improve forwarding performance as compared to a randomized strategy, reducing the average information age of up to 60%, the blackout probability of up to two orders of magnitude.<br> We also consider the effect of multi-hop propagation of situational information on the reliability of a forward collision warning application, and show that network-coding based propagation yields a factor three improvement of reliability with respect to a randomized forwarding strategy, and even higher improvements with respect to the case of no propagatio