Exploration of adaptive beaconing for efficient intervehicle safety communication

Abstract

ne of the major goals of vehicular ad hoc networks (VANETs) is to support traffic safety. Cooperative awareness applications require frequent and low-delay information exchange among vehicles, including data such as current position, movement, and acceleration. This is realized by broadcasting socalled (single-hop) beacon messages. As a result, every vehicle is aware of other vehicles within a certain range. Beaconing is also the basic supporting process that enables geographic routing and message dissemination. However, this also requires a significant amount of bandwidth. The higher the frequency and thus the accuracy, the higher the bandwidth consumption.The first phase of research on VANETs has set the boundary conditions in terms of basic communication protocols and routing paradigms. Communication in VANETs will be based on IEEE 802.11p. Message dissemination and routing are based on geocast principles. Beaconing takes place on a single communication channel (commonly referred to as the control channel) that is shared by all nodes.However, it has also been shown in [1] that the limited bandwidth of the wireless channel has a severe impact on the efficiency of the communication. This means that if the beacon rate is fixed, channel load may increase too much in scenarios with high vehicle density. High channel utilization increases the information loss as packets are received erroneously, which is especially observed at large distances between sender and receiver.Simply reducing the beacon rate is not a suitable solution because it reduces the information quality at the same time. The error between the real position of a vehicle and the last known position retrieved from a beacon increases as the beacon rate is reduced. This results in position inaccuracies, which may disturb correct operation of active safety applications, which rely on accurate and up-to-date information.Currently, there is no final recommendation for a particular static beacon rate. No upper boundary in terms of maximum channel load has been specified. Furthermore, no requirements from the different applications have yet been clearly defined. As a consequence, even minimum and maximum beacon rate are hard to derive as these two boundaries have to satisfy all imaginable road traffic situations.In this article we pave the way for further enhancements of beaconing algorithms for the second phase of research on VANETs. After a short assessment of the current state of the art, we present a detailed analysis of the problem space and how different beacon rates influence 1) the offered load to the channel and 2) the resulting average and maximum accuracy of information Based on this problem evaluation, we motivate a flexible approach to control both appropriately. For this purpose, we propose a situation adaptive beaconing process that adapts the beacon rate continuously. The design space and different candidates for such an algorithm are introduced in this article. AbstractIn the future intervehicle communication will make driving safer, easier...

Beaconing Approaches in Vehicular Ad Hoc Networks: A Survey

“…Authors in [8] first studied the adaptation of beacon rate in order to find the compromise between information accuracy and bandwidth consumption. After the analysis of the parameters, which affect to the beacon rate, they proposed a scheme to adapt beacon rate according to the VANET traffic behaviour.…”

“…In short, reducing the beacon rate leads to the exchange of out-of-date information. To tackle this issue, the authors in [7], [8], [9], [10], [11] [12] considered conditional update approach in which a vehicle adapts its beacon rate based on various parameters.…”

Congestion and Awareness Control in Cooperative Vehicular Systems

“…To this aim, various rebroadcasting schemes are proposed based on different open-loop strategies: synchronous and asynchronous designs, repetition with and without carrier sensing, fixed number, and p-persistent repetition. A different perspective is reported in [37] with regard to the accuracy of the awareness information required by each vehicle. The work in [37] considers that the packet generation rate should depend on each vehicle's mobility characteristics, and those of the vehicles surrounding it, as well as the traffic context/situation.…”

“…A different perspective is reported in [37] with regard to the accuracy of the awareness information required by each vehicle. The work in [37] considers that the packet generation rate should depend on each vehicle's mobility characteristics, and those of the vehicles surrounding it, as well as the traffic context/situation. In particular, the authors propose the use of situation-adaptive beaconing to achieve adequate levels of accuracy or updated awareness information received from neighboring vehicles.…”

Location-based forwarding in vehicular networks

“…Let N i−f3 be the number of hops required after the third forwarder has forwarded the message. According to [98] (page 5), when i becomes large, N i−f3 has asymptotically the following normal distribution: 33) with N i−f3 = 0 for i ≤ f 3 and µ L3 and σ 2 L3 being the mean and variance of the distribution of the hop length L 3 , which can easily be calculated using Eq. (6.29).…”