Survey over VANET Routing Protocols for Vehicle to Vehicle Communication
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paper_title: CarTALK 2000: safe and comfortable driving based upon inter-vehicle-communication

paper_content:

CarTALK 2000 is a European Project focussing on new driver assistance systems which are based upon inter-vehicle communication. The main objectives are the development of cooperative driver assistance systems on the one hand and the development of a self-organising ad-hoc radio network as a communication basis with the aim of preparing a future standard. As for the assistance system, the main issues are: a) assessment of today's and future applications for co-operative driver assistance systems, b) development of software structures and algorithms, i.e. new fusion techniques, c) testing and demonstrating assistance functions in probe vehicles in real or reconstructed traffic scenarios. To achieve a suitable communication system, algorithms for radio ad-hoc networks with extremely high dynamic network topologies are developed and prototypes tested in the vehicles. Apart from technological goals, CarTALK 2000 actively addresses market introduction strategies including cost/benefit analyses and legal aspects, and aims at the standardisation to bring these systems to the European market. CarTALK 2000 started in August 2001 as a three-years project which is funded within the IST Cluster of the 5th Framework Program of the European Commission.
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paper_title: A highly adaptive distributed routing algorithm for mobile wireless networks

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We present a new distributed routing protocol for mobile, multihop, wireless networks. The protocol is one of a family of protocols which we term "link reversal" algorithms. The protocol's reaction is structured as a temporally-ordered sequence of diffusing computations; each computation consisting of a sequence of directed link reversals. The protocol is highly adaptive, efficient and scalable; being best-suited for use in large, dense, mobile networks. In these networks, the protocol's reaction to link failures typically involves only a localized "single pass" of the distributed algorithm. This capability is unique among protocols which are stable in the face of network partitions, and results in the protocol's high degree of adaptivity. This desirable behavior is achieved through the novel use of a "physical or logical clock" to establish the "temporal order" of topological change events which is used to structure (or order) the algorithm's reaction to topological changes. We refer to the protocol as the temporally-ordered routing algorithm (TORA).
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paper_title: GPSR: greedy perimeter stateless routing for wireless networks

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We present Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless datagram networks that uses the positions of routers and a packet's destination to make packet forwarding decisions. GPSR makes greedy forwarding decisions using only information about a router's immediate neighbors in the network topology. When a packet reaches a region where greedy forwarding is impossible, the algorithm recovers by routing around the perimeter of the region. By keeping state only about the local topology, GPSR scales better in per-router state than shortest-path and ad-hoc routing protocols as the number of network destinations increases. Under mobility's frequent topology changes, GPSR can use local topology information to find correct new routes quickly. We describe the GPSR protocol, and use extensive simulation of mobile wireless networks to compare its performance with that of Dynamic Source Routing. Our simulations demonstrate GPSR's scalability on densely deployed wireless networks.
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paper_title: Geographic routing in city scenarios

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Position-based routing, as it is used by protocols like Greedy Perimeter Stateless Routing (GPSR) [5], is very well suited for highly dynamic environments such as inter-vehicle communication on highways. However, it has been discussed that radio obstacles [4], as they are found in urban areas, have a significant negative impact on the performance of position-based routing. In prior work [6] we presented a position-based approach which alleviates this problem and is able to find robust routes within city environments. It is related to the idea of position-based source routing as proposed in [1] for terminode routing. The algorithm needs global knowledge of the city topology as it is provided by a static street map. Given this information the sender determines the junctions that have to be traversed by the packet using the Dijkstra shortest path algorithm. Forwarding between junctions is then done in a position-based fashion. In this short paper we show how position-based routing can be aplied to a city scenario without assuming that nodes have access to a static street map and without using source routing.
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paper_title: Connectivity-Aware Routing (CAR) in Vehicular Ad-hoc Networks

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Vehicular ad hoc networks using WLAN technology have recently received considerable attention. We present a position-based routing scheme called Connectivity-Aware Routing (CAR) designed specifically for inter-vehicle communication in a city and/or highway environment. A distinguishing property of CAR is the ability to not only locate positions of destinations but also to find connected paths between source and destination pairs. These paths are auto-adjusted on the fly, without a new discovery process. "Guards" help to track the current position of a destination, even if it traveled a substantial distance from its initially known location. For the evaluation of the CAR protocol we use realistic mobility traces obtained from a microscopic vehicular traffic simulator that is based on a model of driver behavior and the real road maps of Switzerland.
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paper_title: A routing strategy for vehicular ad hoc networks in city environments

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Routing of data in a vehicular ad hoc network is a challenging task due to the high dynamics of such a network. Recently, it was shown for the case of highway traffic that position-based routing approaches can very well deal with the high mobility of network nodes. However, baseline position-based routing has difficulties to handle two-dimensional scenarios with obstacles (buildings) and voids as it is the case for city scenarios. In this paper we analyze a position-based routing approach that makes use of the navigational systems of vehicles. By means of simulation we compare this approach with non-position-based ad hoc routing strategies (dynamic source routing and ad-hoc on-demand distance vector routing). The simulation makes use of highly realistic vehicle movement patterns derived from Daimler-Chrysler's Videlio traffic simulator. While DSR's performance is limited due to problems with scalability and handling mobility, both AODV and the position-based approach show good performances with the position-based approach outperforming AODV.
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paper_title: A-STAR: A Mobile Ad Hoc Routing Strategy for Metropolis Vehicular Communications

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One of the major issues that affect the performance of Mobile Ad hoc NETworks (MANET) is routing. Recently, position-based routing for MANET is found to be a very promising routing strategy for inter-vehicular communication systems (IVCS). However, position-based routing for IVCS in a built-up city environment faces greater challenges because of potentially more uneven distribution of vehicular nodes, constrained mobility, and difficult signal reception due to radio obstacles such as high-rise buildings. This paper proposes a new position-based routing scheme called Anchor-based Street and Traffic Aware Routing (A-STAR), designed specifically for IVCS in a city environment. Unique to A-STAR is the usage of information on city bus routes to identify an anchor path with high connectivity for packet delivery. Along with a new recovery strategy for packets routed to a local maximum, the proposed protocol shows significant performance improvement in a comparative simulation study with other similar routing approaches.
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paper_title: A cluster-based directional routing protocol in VANET

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Vehicular Ad-hoc Network (VANET) is a new application of Mobile Ad-hoc Network (MANET) in the field of Inter-vehicle communication. As the high mobility of vehicles, some traditional MANET routing protocols may not fit the VANET. In this paper, we propose a cluster-based directional routing protocol (CBDRP) for highway scenarios, in which the header of a cluster selects another header according to the moving direction of vehicle to forward packets. Simulation results shows the CBDRP can solve the problem of link stability in VANET, realizing reliable and rapid data transmission.
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paper_title: A New Cluster Based Routing Protocol for VANET

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With the development of vehicles and mobile Ad Hoc network technology, the Vehicle Ad hoc Network (VANET) has become an emerging field of study. It is a challenging problem for searching and maintaining an effective route for transporting some data information. In this paper the authors designed a new routing protocol for VANET based on the former results, called CBR (Cluster Based Routing). Compared with other routing protocols, the new one has obvious improvement in the average routing overhead and small average end to end delay jitter with the increase of vehicles number. The real-time traffic applications require data transmission delay time to be relatively stable, small average end to end delay jitter with the increase of vehicles number just meets the real-time application needs.
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paper_title: Emergency Broadcast Protocol for Inter-Vehicle Communications

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The most important goal in transportation systems is to reduce the dramatically high number of accidents and fatal consequences. One of the most important factors that would make it possible to reach this goal is the design of effective broadcast protocols. In this paper we present an emergency broadcast protocol designed for sensor inter-vehicle communications and based in geographical routing. Sensors installed in cars continuously gather important information and in any emergency detection raise the need for immediate broadcast. The highway is divided in virtual cells, which moves as the vehicles moves. The cell members choose a cell reflector that behaves for a certain time interval as a base station that handle the emergency messages coming from members of the same cell, or close members from neighbor cells. Besides that the cell reflector serves as an intermediate node in the routing of emergency messages coming from its neighbor cell reflectors and does a prioritization of all messages in order to decide which is the first to be forwarded. After this the message is forwarded through the other cell reflectors. Finally the destination cell reflector sends the message to the destination node. Our simulation results show that our proposed protocol is more effective compared to existing inter-vehicles protocols
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paper_title: Broadcasting in VANET

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In this paper, we report the first complete version of a multi-hop broadcast protocol for vehicular ad hoc networks (VANET). Our results clearly show that broadcasting in VANET is very different from routing in mobile ad hoc networks (MANET) due to several reasons such as network topology, mobility patterns, demographics, traffic patterns at different times of the day, etc. These differences imply that conventional ad hoc routing protocols such as DSR and AODV will not be appropriate in VANETs for most vehicular broadcast applications. We identify three very different regimes that a vehicular broadcast protocol needs to work in: i) dense traffic regime; ii) sparse traffic regime; and iii) regular traffic regime. We build upon our previously proposed routing solutions for each regime and we show that the broadcast message can be disseminate efficiently. The proposed design of the distributed vehicular broadcast (DV-CAST) protocol integrates the use of various routing solutions we have previously proposed.
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paper_title: Parameterless Broadcasting in Static to Highly Mobile Wireless Ad Hoc, Sensor and Actuator Networks

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In a broadcasting task, source node wants to send the same message to all the other nodes in the network. Existing solutions range from connected dominating set (CDS) based for static networks, to blind flooding for moderate mobility, to hyperflooding for highly mobile and frequently partitioned networks. The only existing protocol for all scenarios is based on some threshold parameters (which may be expensive to gather) to locally select between these three solution approaches. Here we propose a new protocol, which adjusts itself to any mobility scenario without using any parameter. Unlike existing methods for highly mobile scenarios, in proposed method, two nodes do not transmit every time they discover each other as new neighbors. Each node maintains a list of two hop neighbors by periodically exchanging 'hello' messages, and decides whether or not it is in CDS. Upon receipt of the first copy of message intended for broadcasting, it selects a waiting timeout and constructs two lists of neighbors: neighbors that received the same message and neighbors that did not receive it. Nodes not in CDS select longer timeouts than nodes in CDS. These lists are updated upon receipt of further copies of same packet. When timeout expires, node retransmits if the list of neighbors in need of message is nonempty. 'Hello' messages received while waiting, or after timeout expiration may revise all lists (and CDS status) and consequently the need to retransmit. This provides a seamless transition of protocol behavior from static to highly mobile scenarios. Our protocol is compared to existing solutions. It was shown to be superior to all of them in number of retransmissions and reliability.
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paper_title: An evaluation of inter-vehicle ad hoc networks based on realistic vehicular traces

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Vehicular ad hoc networks (VANETs) using WLAN tech-nology have recently received considerable attention. The evaluation of VANET routing protocols often involves simulators since management and operation of a large number of real vehicular nodes is expensive. We study the behavior of routing protocols in VANETs by using mobility information obtained from a microscopic vehicular traffic simulator that is based on the on the real road maps of Switzerland. The performance of AODV and GPSR is significantly in uenced by the choice of mobility model, and we observe a significantly reduced packet delivery ratio when employing the realistic traffic simulator to control mobility of nodes. To address the performance limitations of communication pro-tocols in VANETs, we investigate two improvements that increase the packet delivery ratio and reduce the delay until the first packet arrives. The traces used in this study are available for public download.
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paper_title: DECA: Density-aware reliable broadcasting in vehicular ad hoc networks

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Reliable broadcasting in vehicular ad hoc networks is challenging due to its unique characteristics including intermittent connectivity and various vehicular scenarios (car traffic is possibly very dense in urban areas or very sparse on highways). In this paper, we propose a new reliable broadcast protocol which is suitable for such characteristics. To address the issue of various vehicular scenarios, our protocol performs periodic beaconing to gather local density information of 1-hop neighbors and uses such information to adapt its broadcast decision dynamically. Specifically, before broadcasting each message, a node selects a neighbor with the highest density. Upon the reception of the broadcast message, each node checks if it is the selected neighbor. If so, it is responsible for rebroadcasting the message immediately. Otherwise, it stores the message for possible rebroadcasting. To address the issue of intermittent connectivity, message information in beacons is used to discover new neighbors, which have not yet received the message. Simulation results show that, in both highway and urban scenarios, our proposed protocol outperforms other competing solutions in terms of reliability, overhead and speed of data dissemination.
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paper_title: Reliable geographical multicast routing in vehicular ad-hoc networks

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Vehicular ad-hoc networks (VANETs) offer a large number of new potential applications without relying on significant infrastructure. Many of these applications benefit from multi-hop relaying of information, thus requiring a routing protocol. Characteristics unique to VANETs (such as high mobility and the need for geographical addressing) make many conven tional ad hoc routing protocols unsuitable. Also, some envisioned applica tions have end-to-end QoS requirements. In this paper we propose a new multicast routing protocol specifically designed for VANETs. Its purpose is to provide a routing service for a future reliable transport protocol. We eval uate its performance using realistic network and traffic models. It is shown that it is possible to implement a reliable multicast routing protocol for VANETs.
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paper_title: DTSG: Dynamic time-stable geocast routing in vehicular ad hoc networks

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Vehicular ad hoc networks (VANETs) have emerged as an area of interest for both industry and researches because they have become an essential part of intelligent transportation systems (ITSs). Many applications in VANET require sending a message to certain or all vehicles within a region, called geocast. Sometimes geocast requires that the message be kept alive within the region for a period of time. This time-stable geocast has a vital role in some ITS applications, particularly commercial applications. This study presents a novel time-stable geocast protocol that works well even in too sparse networks. Moreover, since commercial applications sometimes make it necessary to change the duration of the stable message within the region, the dynamic nature of a geocast protocol should allow this time to be extended, reduced, or canceled without any additional cost. Therefore, we call it a dynamic time-stable geocast, DTSG, protocol. It works in two phases (the pre-stable period and the stable period), and the simulation results show that it works well in its performance metrics (delivery ratio and network cost). In addition, these results validate the protocol prediction of its performance metrics. Moreover, with the informed time of zero, all the intended vehicles will be informed as soon as they enter the region. The fact that the protocol is independent of the networks' density, the vehicles' speed, and the vehicles' broadcasting range, makes it more robust than others that fail in sparse networks or in high-speed nodes.
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Title: Survey over VANET Routing Protocols for Vehicle to Vehicle Communication

Section 1: Introduction
Description 1: Write about the emergence of VANET technology, its applications, and the motivations behind studying VANET routing protocols.

Section 2: Overview Of Routing Protocols
Description 2: Explain the challenges due to highly dynamic topology in VANET, and classify the routing protocols into different categories: Topology based, Position based, Cluster based, Geocast based, and Broadcast based.

Section 3: Topology Based Routing Protocol
Description 3: Describe the working mechanism of topology-based routing protocols, including proactive (table-driven) and reactive (on-demand) routing, along with their pros and cons.

Section 4: Position Based Routing Protocol
Description 4: Explore how position-based routing utilizes geographic positioning for routing decisions. Discuss various protocols such as GPSR, GPCR, CAR, GSR, A-STAR, and STBR, including their strengths and weaknesses.

Section 5: Cluster Based Routing Protocol
Description 5: Discuss cluster-based routing where nodes are grouped into clusters for scalable communication. Describe protocols like HCB, CBDRP, CBLR, CBR, and LORA-CBF, and their respective advantages and disadvantages.

Section 6: Broadcast Based Routing Protocol
Description 6: Explain broadcast routing protocols which use flooding techniques for message dissemination. Detail protocols such as BROADCOMM, EAEP, DV-CAST, SRB, PBSM, PGB, UMB, V-TRADE, and DECA, with their benefits and drawbacks.

Section 7: Geocast Based Routing Protocol
Description 7: Outline Geocast routing protocols aimed at targeted communication within a geographic area. Highlight protocols like IVG, ROVER, and DTSG, along with their practical implications.

Section 8: Conclusion
Description 8: Summarize the comparative analysis of various VANET routing protocols and emphasize the necessity of further research to develop more robust and efficient protocols for vehicular communication.
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