National Transportation Statistics (Annual Report, 1983)

Given the bandwidth assignment for dedicated short range communications for use in vehicular ad-hoc network (VANET) and the expected introduction of equipment in the next few years, we elaborate on how VANET can support infotainment services. We define an architectural model for the integration of VANETs and cellular networks, according to a push mode paradigm where VANETs are used primarily to disseminate service announcements and general interest messages. Cooperation with cellular network is addressed by comparing architecture alternatives. A set of information dissemination protocols for VANETs is compared via simulations on a real urban map. Some results from a lab testbed based on IEEE 802.11p boards are presented along with an application developed for Android operating system to demonstrate the concept of the paper.

Infotainment services based on push-mode dissemination in an integrated VANET and 3G architecture

With intervehicle communications becoming a more and more popular research topic recently, the medium access control layer of the vehicular network has also received a considerable amount of attention. However, this increased interest has not always translated into a careful analysis of the properties exhibited by the MAC protocol when used by vehicular safety applications. This article tries to fill this gap by providing a comprehensive discussion on a number of important characteristics of the link layer in vehicular communications.

Properties of the MAC layer in safety vehicular Ad Hoc networks

Majority of research contributions in wireless access in vehicular environment (WAVE)/IEEE 802.11p standard focus on life critical safety-related applications. These applications require regular status update of vehicle’s position referred to as beaconing. Periodic beaconing in vehicle to vehicle communication leads to severe network congestion in the communication channel. The condition worsens under high vehicular density where it impacts reliability and upper bound latency of safety messages. In this paper, WAVE compliant enhancement to the existing IEEE 802.11p protocol is presented which targets prioritized delivery of safety messages while simultaneously provisioning the dissemination of nonsafety messages. Proposed scheme relies on dynamic generation of beacons to mitigate channel congestion and inefficient bandwidth utilization by reducing transmission frequency of beacons. Through the use of clustering mechanism, different beaconing frequencies and different data transmission rates are assigned to prioritize vehicular mobility. Through extensive simulation results, the performance of the proposed approach is evaluated in terms of a wide range of quality of service (QoS) parameters for two different transmission ranges. Results show that the proposed protocol provides significant enhancement and stability of the clustered topology in vehicular ad hoc network over existing standard and other protocols with similar applications.

/pdf/adaptive-beaconing-in-mobility-aware-clustering-based-mac-3dq36qivb3.pdf

Adaptive Beaconing in Mobility Aware Clustering Based MAC Protocol for Safety Message Dissemination in VANET

The invention discloses a rapid broadcasting method MCAB (Multi-candidates-based adaptive Broadcast Algorithm) based on position information in a vehicular network. The method solves the problems that in a VANET, transmission of the broadcast information is greatly delayed and reliability is poor. According to the method, a plurality of vehicles are taken as candidate transmitting vehicles to reduce source point retransmittsion frequency, meanwhile the vehicles can select a broadcast mechanism which is adopted in a self-adaptive mode according to positions of the vehicles including crossings or road segments, accordingly the broadcast method has great flexibility, time delay is reduced and reliability is guaranteed. According to the method, broadcast is divided into crossing broadcast and single road segment broadcast, when the vehicles are located on the crossings or the road segments, absolute position information of the vehicles must be obtained in advance, so the fact that all the vehicles are provided with GPS navigation systems is required. The method is adopted based on the premise that the position information, the moving direction, the current speed, the accelerated speed, road segment IDs and other information can be obtained through the GPS navigated systems.

Rapid broadcasting method based on position information in vehicular network

Although ultra wideband (UWB) is a promising wireless technology for the future due to its high data rate, low power consumption, and low cost, its worldwide acceptance is conditioned by coexistence issues because of the frequency overlap with other wireless standards such as WiMax. In many countries, a detect and avoid (DAA) scheme has been promoted as a means to mitigate interference and it is now regarded as an indispensable solution for commercialization of UWB. A detailed specification for DAA can be determined by analyzing co-channel interference for a victim receiver. This paper presents a quantitative interference analysis using desired to undesired (D/U) signal power ratio as well as verification results using an equipment-based WiMax testbed. Finally, the D/U ratio results were used to determine minimum keep-out distance and the sensing threshold level for DAA in a UWB device.

Interference Analysis and Sensing Threshold of Detect and Avoid (DAA) for UWB Coexistence with WiMax

Vehicular Ad-hoc Network(VANET) enables a wireless communication between vehicles to improve driver's safety. For the safety, a message including safety-related information is broadcast between vehicles and forwarded for farther vehicles. VANET poses challenges that broadcast attempts from many vehicles cause collisions between packets and result in packet drops. Many researches have concentrated on removing collisions in those excessive broadcasts. These approaches lead one vehicle to be selected as a rebroadcast vehicle. However, it makes difficult to forward the safety message to all directions at intersections. In this paper, we suggest an efficient way to broadcast a safety message to all directions at an intersection with a short delay and without a collision. Our simulation results show a coverage improvement of as much as 70% and a delay reduction of as much as 100msec.

Fast broadcast at the intersection in VANET

Vehicular Ad-hoc networks (VANETs) provide a way for a vehicle to deliver various types of information to users or drivers in other vehicles. Distributing a large amount of information such as multimedia messages in a single control channel makes the control channel easily congested. Transmitting multimedia messages through multi-channel to avoid this congestion becomes a feasible solution. However, low-connectivity in a low vehicle density in multi-channel poses unique challenges and can produce connection failure if this issue is not carefully addressed. In this paper, a network coding technique with divide-and-deliver is introduced to solve this unique challenge for delivering multimedia contents through multiple service channels in a low vehicle density. Through the rigorous analytical derivation and extensive simulation, we show the proposed scheme significantly improves reliability with minimum usage of the control channels in a typical VANETs environment.

Efficient safety message forwarding using multi-channels in low density VANETs

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Papers

Interference Analysis and Sensing Threshold of Detect and Avoid (DAA) for UWB Coexistence with WiMax

Fast broadcast at the intersection in VANET

Efficient safety message forwarding using multi-channels in low density VANETs