EAPRAD: A MAC protocol for Enhancing Access Probability and Reducing Access Delay in VANETs

The boost of wireless technology brings dramatic growth for Vehicular ad-hoc networks(VANETs). The effective routing and forwarding protocol is critical for the performance of VANETs thus influence the automatic driving and information distribution. The dynamic characteristic of vehicle to vehicle(V2V) communications makes it hard to maintain a reliable path between vehicles. In order to improve transmission performance in VANETs, we make full use of the Content-centric information dissemination, and there are some existing efforts on proving feasibility of content-centric network(CCN). In this paper, we propose a novel Source Selection Dynamically Network Coding-based Information Centric Network protocol (SSDNC), which introduces CCN architecture in VANET. SSDNC exploit the features of CCN to make multiple sources exist. With the application of Analytic Hierarchy Process(AHP), requested symbols can be distributed adaptively to different interfaces according to their weight. Then the forwarding decisions will be made to obtain the information that makes transmission more effective. Moreover, we take advantage of network coding (NC) to eliminate the network redundancy for the purpose of achieving higher performance. We evaluate the performance of the SSDNC using ndnSIM over NS-3 network simulator, which focused on the size of chunk, throughput and average transmission delay and compared with ICTP [1]. The result shows that the performance of our protocol is better than ICTP.

Various ongoing research efforts in Vehicular Ad hoc Network (VANET) related to safety and non-safety applications have been published in academia and industry. One of the main areas in VANET that is still lacking of significant research contributions is toward designing reliable Medium Access Control (MAC) protocols. Existing surveys on MAC protocols in VANET mostly discuss general MAC methods, that include contention-based and contention-free MAC protocols. A hybrid MAC protocol that adopts both contention-based and contention-free MAC, proposed to enhance the network performance in VANET, is fruitful to be explored further. Hence, a survey of hybrid MAC protocols for VANET is presented in this paper. The benefits and limitations of the existing hybrid MAC protocols are discussed based on their classification to provide some insights into the recent advancement of high-performance MAC protocols for vehicular networks. Finally, some open research issues are highlighted as part of future research directions that need further investigations.

Efficient content distribution is one of the emerging applications in vehicular networks. To provide scalable content distribution in vehicular networks, Chord Peer-to-Peer (P2P) overlay could be applied. Most P2P protocols, including Chord, are designed for wired-line network, and might perform poorly in mobile networks. Mobile Chord (MChord) is proposed to enhance the P2P performance over Vehicular Ad hoc Network (VANET). In addition, cross-layer design to improve MChord performance in VANET is also investigated. Extensive NS-2 simulations with vehicular mobility traces are conducted to evaluate the P2P overlay performance in VANET. MChord and its cross-layer design outperforms the original Chord in various aspects, including application layer forwarding steps, query response ratio, correct query response ratio, and application delay.

In vehicular ad hoc networks (VANETs), efficient data dissemination to a specified number of vehicles with minimum collisions and limited access delay is critical for accident prevention in road safety. However, packet collisions have a significant impact on access delay, and they may lead to unanticipated link failure when a range of diversified collisions are combined due to complex traffic conditions and rapid changes in network topology. In this paper, we propose a distributed contention-free cooperative medium access control (CFC-MAC) protocol to reduce heterogenous collisions and unintended access delay in stochastic traffic scenarios. Firstly, we develop a cooperative communication system model and cooperative forwarding mechanism to explore the optimum road path between the source and destination by identifying the potential cooperative vehicles. Secondly, we propose a vectorized trajectory estimation mechanism to suppress merging collisions by identifying the relative velocity of vehicles with different speeds in a specific time interval. Based on the case study, typical heterogeneous collisions and aggregated heterogeneous collisions at dissociated positions and associated positions are investigated. In both cases, we propose the corresponding collision-resolving mechanisms by methodically recapturing the colliding time slot or acquiring the available free time slots after identifying the access vehicles and comparing the received signal strengths. Performance analysis for collision probability and access delay is conducted. Finally, the simulation results show that the proposed protocol can achieve deterministic access delay and a minimal collision rate, substantially outperforming the existing solutions.

The Vehicular Ad Hoc Networks (VANETs) paradigm is a promising technology to enable the Internet of Vehicles (IoV) for future integration with 5G and 6G infrastructures in smart cities. However, VANET can be susceptible to wireless interference, like co-channel interference, which can cause communication quality and performance to deteriorate, threatening vehicular safety applications, including traffic management and accident prevention. Hence, VANET requires practical interference mitigation strategies, such as digital beamforming, that mitigate the signals from unwanted directions while improving the reception of signals from desired directions with adequate precision, which is helpful for VANET’s highly mobile environments. In this paper, a review of the literature on digital beamforming techniques is carried out that examines their advantages and limitations. Furthermore, an important contribution of this paper is the development of an experimental platform for a roundabout VANET based on simulations, where different digital beamforming algorithms, such as phase-shift and Minimum-Variance Distortionless-Response (MVDR), are tested. The results show that the MVDR algorithm leads to improvement due to its adaptability to ad hoc environments. Also, they show thatMVDRadaptive beamforming improves Signal-to-Interference-plus-Noise Ratio (SINR) and reduces outage event proportion compared to non-beamforming and conventional beamforming scenarios, highlighting their potential to mitigate co-channel interference in highly changing VANET environments. Therefore, adaptive digital beamforming can improve the performance and reliability of VANETs, offering the potential for advanced wireless network implementations in smart cities with 5G and 6G infrastructures.

In intelligent transportation systems, the collaboration between vehicles and the road side units is essential to bring these systems to realization. The emerging Vehicular Ad Hoc Network (VANET) is becoming more and more important as it provides intelligent transportation application, comfort, safety, entertainment for people in vehicles. In order to provide stable routes and to get good performance in VANET, there is a need of proper routing protocols must be designed. In this paper, we are working with the very well-known ad-hoc on-demand distance vector (AODV) routing protocol. The existing Routing protocol AODV-L which is based on the Link expiration time is extended to propose a more reliable AODV-AD which is based on multichannel MAC protocol. For the performance evaluation of routing protocols, a simulation tool ‘NS2’ has been used. Simulation results show that the proposed AODV-AD protocol can achieves better performances in forms of high Route stability, Packet Delivery ratio and packet loss rate than traditional AODV-L and traditional AODV.

Given the resource consumption of transmitting data packets in Vehicular Ad Hoc Network (VANET), selfish nodes might refuse to transmit messages to others just for maximizing their own profits. Therefore, the communication performance within the whole network would be affected. Along with its wide-scale implementation in many road-side applications, selfish behaviors of such nodes are witnessed to be causing serious problems and degradations in VANETs. We address the impacts of the selfish nodes in the performance of VANETs and accordingly, the credit-based method is utilized to re-implement the spirit that can provide incentive for mobile nodes to cooperate with each other and report actions honestly. The simulation results demonstrated that the system earnings would decrease due to the existence of selfish nodes, thereby also proving that the incentive mechanism can facilitate mutual cooperation among nodes.

Vehicular communications enable a variety of applications to improve road safety, driving experience, and traffic management. Many of these applications require data to be routed through multiple hops until they reach to the destination. Unfortunately, due to highly dynamic driving patterns of vehicles, it is challenging to achieve effective and time-sensitive data forwarding in vehicular ad hoc networks (VANETs). Both social- based and trajectory-assisted data forwarding strategies have been proposed to improve packet delivery performance in VANETs. The former reaches limited data delivery ratio and the latter leaks location privacy of drivers. In this paper, we propose a privacy-preserving data forwarding protocol based on personal-social behaviors of drivers to achieve highly reliable transmissions and privacy preservation for drivers in VANETs. Specifically, by observing the phenomenon that vehicles regularly visit some social spots, such as shopping malls, museums and busy intersections, we can obtain the personal-social behaviors of drivers. Based on these behaviors, the messages can be delivered to roadside units (RSUs) at the social spots frequently visited by vehicles. Later, once a vehicle visits the social spots, it can successfully retrieve the messages destined for it from the RSUs anonymously. In addition, the identities of senders are conditionally preserved and the personal-social behaviors of drivers are protected against a global adversary. Performance evaluation demonstrates its efficiency in terms of high delivery ratio and low average delay.

Vehicular Ad-hoc Networks (VANET) are considered a promising application in Intelligent Transport Systems (ITS). It is characterized by a high mobility, a high density of nodes, and a very constrained topology that require a more suitable and more reliable routing protocol. Hence, the need to optimize the current routing protocols used in Mobile Ad-hoc Networks (MANET), in order to increase their performance in VANET. Broadcast communication method remains a very important step to adapt the broadcast information to other nodes and to select the routes in better conditions. In this article, we propose a new broadcast approach based on the neighborhood broadcasting methods. Based on this solution, we present an improving Ad-hoc On-Demand Distance Vector Routing (AODV) to reduce the number of dropped packets, and minimize network overhead. The simulation shows encouraging results of our proposed approach.

Most applications in urban vehicular ad hoc networks (VANETs) rely on information sharing, such as real‐time traffic information queries, and advertisements. However, existing data dissemination techniques cannot guarantee satisfactory performance when amounts of information requests come from all around the network. Because these pieces of information are useful for multiple users located in various positions, it is beneficial to spread the cached copies around. Existing work proposed caching mechanisms and conducted simulations for validation, but there is a lack of theoretical analysis on the explicit caching effects. Because of the complex urban environment and high mobility of vehicles, quantifying the caching effects on the VANET performance is quite challenging. We present the cache coverage ratio as the metric to measure the caching effects, and theoretical analysis is given based on reasonable assumptions for urban VANETs, through which we find the affecting factors include vehicle density, transmission range, and ratio of caching vehicles. We deduce the quantitative relationship among them, which have similar forms as the cumulative density function of an exponential distribution. We also consider the impact of vehicle mobility to predict the future cache effect on surrounding roads of the caching area. We conduct intensive simulations, which verify that the theoretical analysis results match quite well with the simulated reality under different scenarios. Copyright © 2015 John Wiley & Sons, Ltd.

Contention-based medium access control (MAC) protocols for vehicular ad hoc networks (VANETs), such as IEEE 802.11p, have been revealed inefficient performance due to merging collisions, hidden terminal problems, poor resource utilization, and inconsistency in various traffic scenarios. This paper proposes a novel clustering-based contention-free MAC (CC-MAC) protocol to handle intra-cluster and inter-cluster transmission collision problems in VANETs. A cluster head (CH) assigns the time slots to the cluster members depending on their traffic demands. Inter-cluster interference among vehicles is minimized by comparing the relative offset time and reducing access delay during the slot allocation. Furthermore, a TDMA-based predetermined scheme is proposed to improve resource utilization for both control channel and service channels, and merging collisions are resolved by disjointed slot assignment. Hidden terminal problem is resolved by detecting slot assignment identification on gateway vehicles regarding the direction of the vehicle’s mobility. Simulation results show that the proposed protocol outperforms the IEEE 802.11p, STCM, and optimized CB-MAC protocols in both highway and urban traffic scenarios in terms of normalized throughput, packet delivery ratio and average end-to-end delay.

Optimization of Value of Parameters in Ad-hoc on Demand Multipath Distance Vector Routing Using Teaching-Learning Based Optimization

Vehicular ad hoc networks (VANETs) are a group of nodes that remain dynamically and randomly situated. VANETs are considered as one of the most prominent technologies for improving the efficiency and safety of modern transportation systems. However, the VANET is also subjected to attacks that will weaken the performance of vehicular communication. To enable communication inside the VANET system, a routing protocol helps to determine directions among nodes. VANET network nodes move very quickly from one place to another, and in that time DDoS attacks will occur in the VANET network. Therefore, it is important to implement DDoS attack detection-based communication level on the entire VANET system. The source node will send data or information to the destination using intermediate nodes, whenever a DDoS attack happens in the node. In this paper, an approach is proposed for detection of a DDoS attack in a VANET network by using the adapted stream region scheme. Once the attack occurs in the VANET network, all the data will be damaged or hacked by another attacker. To minimize the DDoS attack and optimize the assigned problem, the author is using packet marking based on adapted stream region (PMBASR) techniques on the network. The PMBASR techniques are used to trace back to the source node, then the node of origin used in RSU server for data request, and at the same time the data will receive a response in the network. Nevertheless, an analytical approach will use PMBASR to detect the DDoS attack and further improve the network performance. Finally, the Ns2 simulation result proves it to be a better result-oriented approach.

The vehicular ad-hoc network (VANET) is a promising technology in near future. VANET allows vehicles to communicate with each other and with roadside units (RSUs). Wireless Access in Vehicular Environment (WAVE), defined by IEEE, provides the Internet connectivity for vehicles as well as vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication. RSUs can form a wireless mesh network (WMN) as a backbone infrastructure to enhance the performance of VANET. However, WAVE supports only one-hop communications for IP packets in VANET, and existing researches do not consider the compatibility between VANET and WMN infrastructure formed by RSUs. We propose the extended WMN (ExWMN) which has the feasibility to extend WMN to VANET domain. In ExWMN, the vehicles can send IP packets to an access router by using the multi-hop capability of WMN. ExWMN uses the addressing scheme of WMN for the extended VANET domain and exploits geographical routing protocols instead of existing routing protocols of WMN due to VANET characteristics such as mobility and dynamically changing network topologies. ExWMN supports the compatibility between the extended VANET and a WMN infrastructure due to RSUs, which provide a bridging function between them. This paper presents the architecture and the detailed procedures of the ExWMN.

A new concept such as smart city was introduced in the last years where the Intelligent Transportation system (ITS ) plays a critical role to provide road safety and manage Vehicular Ad Hoc Networks (VANETs) traffic. Nevertheless, VANETs have significant constraints like nodes high mobility, intermittent connectivity, variable network density and heterogeneity. However, the different types of traffic, the different Quality of Service requirements, the need to exchange mobile data, multi-services and data diversity leads mainly to load and time constraints in this specific and stringent type of networks. The main characteristic of this kind of networks is the very changing topology that poses supplementary constraints and makes achieving QoS constraints a very challenging task. In VANET network the vehicle generated traffic will be transferred to the data center from road side unit to the base station by using Long Term Evolution (LTE) in an urban area. Despite LTE has a larger system capacity and it provides a higher transmission speed, the network performance is affected by the implemented scheduling algorithm. In this context, we study the efficiency of LTE scheduler algorithms such as Proportional Fairness, Round Robin, Priority Set Scheduler, Maximum Throughput Scheduler and Throughput to Average Scheduler and Blind Equal Throughput mainly at the road side unit using Network Simulator 3(NS3) to determinate the most suitable scheduler for VANET traffic. Results demonstrate that the round robin algorithm is more effective for volumetric VANET traffic in terms of throughput, delay, packet loss rate and fairness.