Multi-hop Vehicular Ad Hoc Networks Research Articles

Cross-Regional Transmission Control for Satellite Network-Assisted Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANETs) have attracted increasing attention in cross-regional communication. The interconnection between VANETs and satellite networks expands their communication range. To improve the transmission performance of heterogeneous networks composed of VANETs and satellite networks, this paper proposes an end-to-end transmission control scheme for satellite network-assisted VANETs, analyzes the bandwidth delay product of multihop VANETs through heterogeneous networks, and establishes a transmission control model applicable to cross-regional environments. To address the long delay and high bit error rate in heterogeneous networks, the model designs the congestion window in the slow start and congestion avoidance of the transmission scheme. The data transmission volume is increased in the slow start, and various packet losses are distinguished in congestion avoidance. The experimental results show that the scheme can achieve good transmission performance in heterogeneous networks composed of VANETs and satellite networks. The results show that VANETs data can be effectively transmitted in heterogeneous networks. Compared with the traditional transmission scheme, this simple and practical end-to-end transmission control scheme can improve speed by 83.49 kbps and reduce transmission duration time of FTP server by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.72\times 10^{3}$ </tex-math></inline-formula> s. The results of this study provide a reference for massive data transmission in heterogeneous networks of VANETs and satellite networks.

Optimization Design and Performance Analysis of Improved IEEE802.11p MAC Mechanism Based on High Mobility of Vehicle

The high-speed movement of vehicles is the core factor affecting the rapid development of vehicular ad hoc network (VANET), especially the impact of vehicle mobility on data access and transmission performance. However, the classic IEEE802.11p data access and transmission protocol are still used in the multi-hop VANET under the highway system, which is adopted in the low-speed environment. Therefore, the impact of vehicle movement on the performance of the existing network is analyzed theoretically, and it is found that the network performance will be greatly reduced with the increase of vehicle speed. In order to improve the network performance in high-speed environment, an improved network access transmission protocol is proposed. Through Markov modeling, the analytic expressions of system delay, throughput, and packet loss rate are obtained. Finally, the effectiveness of the improved mechanism is verified by comparing the simulation results of two mechanisms.

Link reliability-based multi-hop directional location routing in vehicular ad hoc network

The vehicular ad hoc network (VANET) is a self-organized and decentralized wireless ad hoc network formed by the mobile vehicles on demand to communicate the traffic-related valuable information among the vehicles. The mobile vehicles work as a node because they use to either send or receive traffic-related information in the network. The vehicles can communicate within restricted distance but mobility nature causes they frequently switch from one network to another network topology; therefore, the links among the vehicles seldom vanish. Therefore, in the multi-hop VANET delivery of the messages at the anticipated destination is problematic. In this paper, a routing mechanism namely link reliability-based multi-hop directional location routing (MHDLR) has proposed to overcome the link vanish problem. The MHDLR decides a link reliability-based next-hop node to create a strongly durable path from the source to destination. In multi-hop VANET, the inter-vehicle distance directly impacts on the connectivity of the vehicles. Therefore, to estimate the link reliability of vehicles their inter-vehicle distance and relative velocity have considered. The geometry-based localization mechanism (G-BLM) has been proposed to estimate the inter-vehicle distance of the vehicles. The performance of MHDLR has estimated for routing metrics i.e. path vanish, message broadcasting time in the group, packet delivery ratio and throughput. The simulated outcomes of the proposed model MHDLR have shown, its performance is better as compared to the existing fuzzy-logic based directional location routing (FLDLR), directional location aided routing (D-LAR) and location aided routing (LAR) protocols.

Spectral Efficiency Optimization and Interference Management for Multi-Hop D2D Communications in VANETs

D2D communications are considered as effective means to achieve vehicle-to-vehicle (V2V) communications, which can be used to improve the performance in vehicular ad hoc networks (VANETs). In this paper, we investigate the resource allocation and interference management based on clustering mechanism in the D2D communications under-laying VANETs aiming to optimize resource utilization efficiency. Firstly, given the transmission resources of intra-cluster for D2D communications, we design a vehicle clustering algorithm to improve intra-cluster resource efficiency and nullify the intra-cluster interference. Secondly, by analyzing the wireless service in VANETs, a cooperative communication scheme with optimized resource utilization is proposed to maximize intra-cluster spectral efficiency. Thirdly, when uplink spectrums are shared, an interference neutralization (IN) model is developed to manage inter-cluster interference, while each vehicle is equipped with one antenna and there is no extra antenna for interference cancellation. In accordance with the IN model, a cross-layer optimization frame for multi-hop VANETs is proposed to maximize the end-to-end throughput of multiple coexisting communication sessions. To evaluate the performance, we select the method without cooperative communication and IN as a benchmark and compare it against the method with cooperative communication only and the method with both cooperative communication and IN. The simulation results show that the method that uses cooperative communication and IN can dramatically increase the throughput. Furthermore, the throughput gains increase along with vehicle density growing in VANETs.

Reliability and energy-efficiency analysis of safety message broadcast in VANETs

Safety applications in vehicular ad hoc networks (VANETs) rely heavily on broadcast schemes for the exchange of status messages. Reliable and on-time delivery of safety messages is critical in VANETs that requires extremely efficient broadcast models. In this paper, we model the reliability of flooding used as the underlying data dissemination protocol for time-critical safety messages. We consider a multi-hop VANET and model end-to-end reliability provided by the network layer. The analytical results unleash important insights about the flooding mechanism. For instance, the reliability drops exponentially beyond a certain threshold value of packet loss probability. Secondly, the impact of hop length on reliability can be catastrophic if not handled appropriately. Keeping in view of the fact that energy-efficient protocols is a key requirement in the upcoming Internet of Vehicles (IoV), we also show that restrictive flooding is more energy-efficient than plain flooding under the same reliability constraint. We validate our theoretical findings through simulations and propose modifications to plain flooding to make it more reliable.

End-to-End Backlog and Delay Bound Analysis for Multi-Hop Vehicular Ad Hoc Networks

Vehicular ad hoc network (VANET) is able to facilitate data exchange among vehicles and provides diverse data services. Intuitively, end-to-end backlog and delay bounds are considered significant metrics to evaluate the quality of service in VANETs. In order to analyze how the multi-hop transmission impacts the delay performance, we model the multi-hop service process into a virtualized single service in a min-plus convolution form. To obtain multi-hop end-to-end backlog and delay bound, we consider the stochastic network traffic characteristics and the highly dynamic channel environment under the static priority, first in first out, and earliest deadline first scheduling policies by applying the martingale theory. The IEEE 802.11p enhanced distributed channel access mechanism is also adopted to analyze the access performance in the MAC sub-layer. With three kinds of real wireless data traces, i.e., VoIP, gaming, and UDP, we verify our algorithm by considering the double Nakagami- $m$ fading channel model among vehicles. From the simulation results, we can see that the supermartingale end-to-end backlog and delay bound are remarkably tight to the real simulation results when compared with the existing standard bounds. The effect of the number of vehicles on the highway on the end-to-end backlog and delay performance is also investigated.

A Geographical Heuristic Routing Protocol for VANETs.

Vehicular ad hoc networks (VANETs) leverage the communication system of Intelligent Transportation Systems (ITS). Recently, Delay-Tolerant Network (DTN) routing protocols have increased their popularity among the research community for being used in non-safety VANET applications and services like traffic reporting. Vehicular DTN protocols use geographical and local information to make forwarding decisions. However, current proposals only consider the selection of the best candidate based on a local-search. In this paper, we propose a generic Geographical Heuristic Routing (GHR) protocol that can be applied to any DTN geographical routing protocol that makes forwarding decisions hop by hop. GHR includes in its operation adaptations simulated annealing and Tabu-search meta-heuristics, which have largely been used to improve local-search results in discrete optimization. We include a complete performance evaluation of GHR in a multi-hop VANET simulation scenario for a reporting service. Our study analyzes all of the meaningful configurations of GHR and offers a statistical analysis of our findings by means of MANOVA tests. Our results indicate that the use of a Tabu list contributes to improving the packet delivery ratio by around 5% to 10%. Moreover, if Tabu is used, then the simulated annealing routing strategy gets a better performance than the selection of the best node used with carry and forwarding (default operation).

Cooperative Stepwise Relaying and Combining for Multihop Vehicular Wireless Communication

Vehicular ad hoc networks (VANETs) require cooperation among vehicles in exchanging information, which improves traffic efficiency and safety. Cooperative communication among these vehicles can significantly improve wireless communication performance. This paper proposes a novel cooperative scheme named cooperative stepwise relaying and combining (CSRC) for multihop VANETs, which utilizes low-order demodulations to partially demodulate high-order modulated signals cooperatively at intermediate relay vehicular nodes. Bit error rate (BER) probability is analyzed. The performance comparison among the proposed CSRC and conventional cooperative schemes is conducted through simulation and a software-defined radio testbed. The experiment results show that CSRC significantly improves the multihop VANETs' performance with cooperative communication.

Fuzzy Logic based Greedy Routing (FLGR) in Multi-Hop Vehicular Ad hoc Networks

In Vehicular Ad Hoc Network (VANET), vehicles on the road provide mainly two types of services to drivers or passengers inside vehicles, namely, safety and comfort services. Safety messages are time-critical, therefore in this paper we have proposed a novel Fuzzy Logic based Greedy Routing (FLGR) protocol which assists in delivering safety messages to the destination vehicle with minimum delay. The proposed FLGR is a multi-hop routing protocol that uses multiple metrics of neighbor vehicles to decide which neighboring vehicle will be the approximate best next-hop node for further forwarding the packets. We have used the concept of fuzzy logic that helps in decision making in VANETs. Fuzzy logic deals with reasoning that is approximate rather than fixed and exact. Fuzzy logic variables may have truth values that range in degrees between 0 and 1. The fuzzy logic inference system became important and useful when the values of the decision criteria are not only vague but uncertain in nature. FLGR is used within the communication range of the current forwarding node that employs fuzzy logic for selecting the best next-hop node in multi hop VANETs. We have used the fuzzy logic tool box of MATLAB to evaluate our protocol. Metrics such as distance, speed, direction, and position of next-hop forwarding node are put into fuzzy logic system. Thus, our protocol helps in finding the approximate best next-hop node for routing the safety messages by employing fuzzy logic. It selects the next-hop node having maximum distance, speed, and progress and minimum angular deviation of nodes towards destination from current forwarding node. Further, FLGR is more suitable for safety applications in vehicular networks.

LLA: A New Anypath Routing Scheme Providing Long Path Lifetime in VANETs

Vehicular ad-hoc networks (VANETs) are a promising solution to improve the road traffic safety, reduce the environmental pollution, or simply provide the on-board infotainment services. However, these actions are often not possible due to high mobility of vehicles causing frequent failures of VANET links. In this paper, we focus on anypath routing to improve the reliability of multihop VANET communications. In particular, the paper is the first one to address the link stability \hbox{issues and to propose} a method called Long Lifetime Anypaths (LLA) providing stable communication paths. Advantages of our \hbox{approach}, presented in comparison to the reference Shortest Anypath First (SAF) scheme, are confirmed throughout simulations.

A collaborative protocol for anonymous reporting in vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) have emerged to leverage the power of modern communication technologies, applied to both vehicles and infrastructure. Allowing drivers to report traffic accidents and violations through the VANET may lead to substantial improvements in road safety. However, being able to do so anonymously in order to avoid personal and professional repercussions will undoubtedly translate into user acceptance. The main goal of this work is to propose a new collaborative protocol for enforcing anonymity in multi-hop VANETs, closely inspired by the well-known Crowds protocol. In a nutshell, our anonymous-reporting protocol depends on a forwarding probability that determines whether the next forwarding step in message routing is random, for better anonymity, or in accordance with the routing protocol on which our approach builds, for better quality of service (QoS). Different from Crowds, our protocol is specifically conceived for multi-hop lossy wireless networks. Simulations for residential and downtown areas support and quantify the usefulness of our collaborative strategy for better anonymity, when users are willing to pay an eminently reasonable price in QoS.