A Vehicular Ad hoc Network (VANET) is a type of wireless ad hoc network that facilitates ubiquitous connectivity between vehicles in the absence of fixed infrastructure. Mul ti-hop routing and beaconing approaches are two important research challenges in high mobility vehicular networks. Routing protocols are divided into two categories of topology-based and position-based routing protocols. In this article, we perform a comparative study among the existing routing solutions, which explores the main advantages and drawbacks behind their design. After implementing the representatives of geographical and topology routing protocols, we analyze the simulation results and discuss the strengths and weaknesses of these routing protocols with regard to their suitability to vehicular networks. Lastly, we discuss the open issues and research directions related to VANET routing protocols.

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Routing Protocols in Vehicular Ad hoc Networks: Survey and Research Challenges

Vehicular ad hoc networks (VANETs) present an intriguing platform for several applications on e.g., intelligent transportation system (ITS) and infotainment applications aspire to be the main pattern of communication among vehicles while travelling. This can significantly impact on the amount of data exchanged by vehicles, increasing the contention on communication links and thus, degrading the quality of service of these applications. So, discrimination of data becomes imperative and forwarding critical information on suitable routes becomes decisive. Hence, a quality of service (QoS)-driven mechanism is needed to handle and assign network resources according to the stringent application data traffic demands. But, VANETs high node mobility and frequent link failure, stuck a big challenge in implementing an effective policy to meet and enforce these QoS requirements. A promising way to tackle this issue is to enforce QoS at the network layer, since it is the crucial point in VANETs’ communication. So, over the years, many QoS-aware routing protocols were specifically conceived for VANETs. In this paper, we present a comprehensive survey of QoS-aware routing protocols in VANETs’ literature. We examined the protocols based on their ability to support ITS infotainment services, their multi-constraint path problem (MCP), protocol’s functionality and weakness, objectives and design challenges. This way, we outline future directions for VANETs QoS-aware protocol research.

VANETs QoS-based routing protocols based on multi-constrained ability to support ITS infotainment services

Vehicular Ad hoc Network (VANET), a subclass of mobile ad hoc networks (MANETs), is a promising approach for the intelligent transportation system (ITS). The design of routing protocols in VANETs is important and necessary issue for support the smart ITS. The key difference of VANET and MANET is the special mobility pattern and rapidly changeable topology. It is not effectively applied the existing routing protocols of MANETs into VANETs. In this chapter, we mainly survey new routing results in VANET. The authors introduce unicast protocol, multicast protocol, geocast protocol, mobicast protocol, and broadcast protocol. It is observed that carry-and-forward is the new and key consideration for designing all routing protocols in VANETs. With the consideration of multi-hop forwarding and carryand-forward techniques, min-delay and delay-bounded routing protocols for VANETs are discussed in VANETs. Besides, the temporary network fragmentation problem and the broadcast storm problem are further considered for designing routing protocols in VANETs. The temporary network fragmentation problem caused by rapidly changeable topology influence on the performance of data transmissions. The broadcast storm problem seriously affects the successful rate of message delivery in VANETs. The key challenge is to overcome these problems to provide routing protocols with the low communication delay, the low communication overhead, and the low time complexity.

Routing protocols in vehicular ad hoc networks

IOV (Internet of Vehicles) has received extensive attention recently as a part of ITS (Intelligent Transportation System). Due to various factors, such as high speed, road condition and traffic flow, the routing protocol becomes one of the important challenging problems in IOV. In this paper, we first present a mobility model at intersection and analysis it by the use of Markov method. On the basis of the mobility model, we propose a novel routing protocol in which the mobile social temporary relationship between vehicles has been considered for the urban transportation environment. Finally, the simulation results show that the packet delivery ratio and the average end-to-end delay of the proposed protocol are better than the traditional protocols.

A Novel Routing Protocol Based on Mobile Social Networks and Internet of Vehicles

Despite the huge success of the Internet in providing basic communication services, the Internet architecture needs to be upgraded so as to provide end-to-end QoS services to its customers. Currently, a user or an enterprise that needs end-to-end bandwidth guarantees between two arbitrary points in the Internet for a short period of time has no way of expressing its needs. To allow these much needed basic QoS services, we propose a single-domain edge-to-edge (g2g) dynamic capacity contracting mechanism, where a network customer can enter into a bandwidth contract on a g2g path at a future time, at a predetermined price. For practical and economic viability, such forward contracts must involve a bailout option to account for bandwidth becoming unavailable at service delivery time, and must be priced appropriately to enable ISPs manage risks in their contracting and investments. Our design allows ISPs to advertise point-to-point different prices for each of their g2g paths instead of the current point-to-anywhere prices, allowing for better end-to-end paths, temporal flexibility and efficiency of bandwidth usage. We compute the risk-neutral prices for these g2g bailout forward contracts (BFCs), taking into account correlations between different contracts due to correlated demand patterns and overlapping paths. We implement this multiple g2g BFC framework on a realistic network model with Rocketfuel topologies, and evaluate our contract switching mechanism in terms of key network performance metrics like fraction of bailouts, revenue earned by the provider, and adaptability to link failures.

Edge-to-Edge Bailout Forward Contracts for Single-Domain Internet Services

Vehicular ad hoc networks (VANETs) are a particular category of mobile ad hoc networks (MANETs) characterized by a high mobility and a reduced connectivity As a prerequisite to communication, an efficient route between network nodes must be established, and it must be adapt to the rapidly changing topology of vehicles in motion This is aim of VANET routing protocols The simulation scene was set up by means of the NS2 simulation platform in this paper The performances of ad hoc on-demand distance vector (AODV) and dynamic source routing (DSR), two classical routing protocols of MANET and VANET, are simulated and analyzed, and the conclusion that the AODV protocol is more suitable for VANET than the DSR protocol is derived

The study of routing strategies in vehicular ad-hoc networks

Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) is a promising technology for high data rate transmission in wideband wireless systems for achieving high downlink capacities in future cellular systems. In this paper subcarrier and power allocation to each user at base-station is allocated to maximize the user data rates, subject to constraints on total power and bit error rate (BER). The chow-campello algorithm has been introduced and analyzed, and a low complexity algorithm has been proposed. The simulation results show that the proposed algorithm can achieve similar performance with much lower computational complexity, which indicates that the proposed algorithm is effective when compared to the existing algorithms.

The improvement of adaptive bit and power loading algorithm with low complexity in MIMO-OFDM systems

The eigenmode decomposition of spatial channel is the preconditions of adaptive power allocations in the present MIMO-OFDM systems. These eigenmodes are generally obtained by the singular value decompositions of the channel matrix at every carrier. However, the decomposition in this way ignored the effects of space-time codes on system performance and it has great complexity for the case with a large number of carriers. A new eigenmode decomposition is proposed to integrate the space time codes in system models, which could be conducted simultaneously by many carriers with simple implementation. Numerical results show that the new eigenmode decomposition is more robust than the classical approaches.

Liu Jiancai

Papers

The study of routing strategies in vehicular ad-hoc networks

The improvement of adaptive bit and power loading algorithm with low complexity in MIMO-OFDM systems

A New Eigenmode Construction Method for MIMO-OFDM Systems