An RSU-Coordinated Synchronous Multi-Channel MAC Scheme for Vehicular Ad Hoc Networks

IEEE 802.11p is a communication protocol which is extended by IEEE 802.11 standard, mainly used in Vehicular Ad-Hoc Networks (VANETs). VANETs generally include the Service Channel (SCH) and Control Channel (CCH). In the traditional 802.11p protocol, the length ratio between CCH and SCHs is fixed. This paper presents a variable SCH interval(VSI) multichannel medium access control (MAC) scheme under the non-saturated channel. Under this scheme, we can control the length of CCH interval and SCH interval. This paper uses three-dimensional Markov chain model to calculate the delay of WAVE service announcement (WSA) frame. We propose a VSI MAC calculation model under unsaturated condition to achieve the maximum throughput. The simulation results indicate that the proposed scheme can help VANETs increase the unsaturated throughput of SCHs and lower the transmission delay of data frames obviously.

Designing QoS-aware medium access control (MAC) scheme is a challenging issue in vehicular ad hoc networks. Proportional fairness and bandwidth utilization are among the significant requirements that should be taken into account by a MAC scheme. In this paper, a bandwidth-efficient and fair multichannel MAC protocol is proposed to address these two requirements, specifically in vehicle-to-vehicle communications. The proposed scheme is based on clustering of vehicles and exploits time division multiple access (TDMA) method alongside the carrier sense multiple access with collision avoidance mechanism to allocate DSRC-based resources in a different manner from IEEE 802.11p/IEEE 1609.4 protocols. It divides each channel into aligned dynamic-sized time frames. In each time frame, in a fully TDMA-based period, transmission opportunities are assigned to vehicles letting them have dedicated transmissions on the service and control channels. The maximum number of transmission opportunities per each frame is determined by the cluster head (CH) based on a defined optimization problem which aims at maximizing both proportional fairness and bandwidth utilization. Furthermore, the bandwidth utilization is assumed to be enhanced more through reallocation of unused transmission opportunities in each time frame, using a proposed reallocation algorithm. The proposed MAC protocol is treated as a lightweight scheme such that various types of unicast, multicast and broadcast communications are possible within the cluster without involving the CH. Evaluation results show that the proposed scheme has more than 90 % achievement in terms of proportional fairness and bandwidth utilization simultaneously, and in this case, has a considerable superiority over TC-MAC. In addition, using the proposed scheme, the satisfaction level of vehicles is preserved appropriately.

The IEEE 1609.4 [1] is a MAC extension of IEEE 802.11p [2] to support multi-channel operations. However, the IEEE 1609.4 does not allow nodes to exchange non-safety messages during the CCH interval. This paper proposes a Vehicular Enhanced Multi-channel MAC protocol (VEMMAC) for Vehicular Ad hoc Networks (VANETs). The VEMMAC adopts the IEEE 1609.4 with alternating sequences of the Control Channel (CCH) interval and the Service Channel (SCH) interval. Different from the IEEE 1609.4, the VEMMAC allows nodes to transmit non-safety messages during CCH interval and broadcast safety messages twice with each in the CCH and SCH interval. Our proposal can utilize the channel resources more efficiently than the IEEE 1609.4. The simulation results show that the proposed VEMMAC protocol achieves higher throughput for service data and is more reliable for safety messages broadcast than other protocols.

Vehicular ad hoc networks (VANETs) have recently received considerable attentions for both safety and commercial applications. In this paper, we address popular content distribution (PCD) in VANETs, in which a popular file is downloaded by a group of on-board units (OBUs) passing by a roadside unit (RSU). Due to high speeds and channel fadings, the OBUs may not finish downloading the entire file from the RSU, but only possess several content pieces. In this paper, we propose a cooperative approach using coalitional graph game to establish a peer-to-peer (P2P) network among the OBUs, in which content pieces are exchanged to complete the file downloading process. Further, we adopt cognitive radio (CR) technique for implementing vehicle-to-vehicle (V2V) transmissions. Simulation results show that the proposed algorithm enjoys a better performance in various conditions, compared to the non-cooperative approach, where OBUs randomly response to content requests from other OBUs.

Fog computing for vehicular Ad-hoc networks: paradigms, scenarios, and issues

Vehicular Ad-hoc NETwork (VANET) is a subcategory of Mobile Ad-hoc NETwork (MANET) which is one of the popular emerging research areas. On one side increase in the number of vehicles, and on the other side due to the presence of communication unit i.e. On Board Unit (OBU) in vehicles helped in the creation of a new network called as VANET. VANET is becoming so popular that it is widely used for different applications that may be safety or non-safety applications. An effective routing protocol is required for the efficient use of VANET for different applications which can optimize different generic parameters of VANET like end-to-end delay, number of hops, etc. Altough multiple paths exist between a source and a destination but the routing protocols evaluate a single path for the transmission of information packets based on parameters like shortest distance towards the destination, density of vehicles, number of hops, etc. Different swarm intelligence techniques like Ant Colony Optimization (ACO), Particle Swarm Optimization (PSO), etc. can be used in VANET to optimize the parameters used in the routing protocol. In this chapter, Ant Colony Optimization (ACO) is used to establish multiple routes between nodes which is vital in the network where network connectivity is random and is frequently changing. This also helps in the parallel transmission of packets in multi-path which reduces end-to-end delay. For this proposed work, a variation of end-to-end delay with respect to transmission distance and a number of vehicles is compared with the existing VANET routing protocol i.e. Geographic Source Routing (GSR), Anchor based Street Traffic Aware Routing (A-STAR). The comparison shows that the proposed work performs better as compared to GSR and A-STAR. To implement multi-path routes MongoDB—an open source distributed database is used and the corresponding operation on the database is implemented using node-red. Selection of effective route and intermediate hop for the transmission of emergency information is essential. The optimized route in VANET not only saves the overall transmission time but also reduces the end-to-end delay. For the optimization of route and number of hops in VANET, another swarm intelligence technique i.e. Particle Swarm Intelligence (PSO) can be used through which the transmission of emergency information with optimum delay is proposed.

In this paper, we investigate the IEEE 802.11p based Vehicular Ad-hoc Network transition between non-saturation and saturation regimes with mobile nodes. We combine vehicular traffic theory, queuing model and Markov chain to evaluate the performance of the network under spatial or networking saturation for mutiple data classes over control and service channels with different transmission rates depending on the vehicle's distance from the roadside unit (RSU). Our results show that the vehicle density growth can result in saturation of wireless medium around the RSU, further resulting in buffer overflows at on board units.

As urbanization grows and the cost of vehicle production decreases, urban traffic has become a major problem of modern life. Developing intelligent vehicles alongside standardizing inter-vehicle communications promises that this technology will be a part of future life. In this research, we propose a method in which clustering is used to gather vehicles' movements information in a vehicle ad-hoc network. This method is based on extending green wave using road-side units as a fixed agent and on board units (OBU) in vehicles as a mobile agent. This information is then transmitted to traffic lights for decision making. This algorithm evaluated using Monte Carlo simulation. The simulation results show this method has a positive effect on reducing the average waiting time and overall stop of the vehicles behind the traffic lights.

In vehicular ad hoc networks (VANETs), vehicles communicate with each other and with roadside units (RSUs) in order to enhance road safety, improve traffic management and provide infotainment services. Along with the growth of VANETs, some challenges are emerging. Although there are many research work on VANETs, cheating attacks are still not well resolved such as selective message relaying attack, faked information reporting attack and resource-consuming attack launched by selfish or malicious participants. To deal with this kind of attacks, we present two novel lightweight security mechanisms by equipped each vehicle's On-Board Unit (OBU) with a small elegant module called TrInc, which is a trusted hardware and composed of only a non-decreasing counter and a key. We observe that TrInc-based method not only can effectively resist against cheating attacks in safety- oriented, convenience-oriented, and commercial-oriented VANET applications, but also significantly defend various aspects of security and privacy in VANETs. Compared with previous works, our proposal features low communication and computation overhead, less memory requirements, and good network scalability.

Due to the high mobility of on-board units (OBUs) and the large-scale network topology frequency hopping-based anti-jamming techniques are not applicable in vehicular ad hoc networks (VANETs). In this paper, to improve the communication performance of VANETs against smart jamming, unmanned aerial vehicles (UAVs) are used. These unmanned aerial vehicles observe the ongoing OBU and UAV communication status and induce the UAV to use a specific relay strategy. The UAV relays the OBU message to another roadside unit (RSU) with a better radio transmission condition if the serving RSU is heavily jammed or interfered. The interactions between a UAV and a smart jammer are formulated using an anti-jamming UAV relay game. The UAV decides whether or not to relay the OBU message to another RSU based on the relay game, the jammer observes the UAV and the VANET strategy it chooses the jamming power accordingly. The proposed relay strategy can reduce the bit-error rate of the OBU message efficiently and increasing the benefit of the VANET Using Q-learning analysis.

Because of the space and time dynamics of moving vehicles, network connectivity is an important performance metric to affect packet delivery in Vehicular Ad Hoc Networks (VANETs). Grouping vehicles into platoons in VANETs can improve road safety, change the network connectivity, and even reduce channel access collisions. Unfortunately, network connectivity is often ignored in the design of exiting MAC protocols for VANETs. In this paper, we analyze the connectivity probability and present a connectivity-aware Medium Access Control (MAC) protocol for platoon-based VANETs. A multi-priority Markov model is presented to derive the relationship between the connectivity probability and the system saturated throughput. Based on variable traffic status and network connectivity, a multi-channel reservation scheme is adopted to dynamically adjust the length of the Control CHannel (CCH) interval and the Service CHannel (SCH) interval for the improvement of the system performance, in terms of network throughput and the priority packet transmission opportunities for platoons. As a result, some important observations to the design and analysis of such communication systems are provided. © 2015 IEEE

The current medium access control (MAC) protocol of the wireless access in vehicular environments (WAVE) system is based on IEEE 802.11 distributed coordination function (DCF) and enhanced distributed channel access (EDCA), which have drawbacks in supporting throughput-sensitive non-safety applications in vehicular ad-hoc network (VANET). In order to address the problem, we propose a novel MAC protocol, namely vehicular MESH network (VMESH), which is specifically designed for the control channel (CCH) and multiple service channels (SCHs) structure of WAVE. A synchronized and distributed beaconing scheme is employed in the VMESH protocol for the purposes of neighborhood awareness and dynamic resource reservation on SCHs. The advantages of the VMESH protocol in supporting the throughput-sensitive non-safety applications in VANET are shown through the theoretical analysis comparing to the current WAVE MAC.

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.

Vehicular Ad Hoc Networks (VANETs) and their diverse applications experience growing interest in both academic and industry. Different types of traffic packets delivered through vehicle-to-vehicle and vehicle-to-infrastructure communications are intended to improve passenger safety and comfort. In this paper, we propose a multiple priority supported Medium Access Control (MAC) protocol for VANETs based on the time slotted p-persistent channel access mechanism. The protocol differentiates the services packets into multi-priority on the Control Channel (CCH). Theoretical analysis based on Markov model is presented to optimize the transmission probabilities of the packets with different priorities, as well as the adjustable intervals of the CCH and the Services Channels (SCHs). Both analytical results and simulation experiments show that the proposed MAC protocol is able to ensure the prioritized transmission of the safety packets and also achieve optimal system performance with respect to saturated throughput.

In IEEE802.11p protocol, multiple channels are assigned to Vehicular Ad-hoc network (VANET), the licensed spectrum of 5.850GHz-5.925GHz is divided into one control channel (CCH) and six service channels (SCHs). So that the mechanism of channel access control has great influence on communication efficiency of VANETs. We propose a channel access control mechanism, which integrates channel reservation algorithm with contention-based Distributed Coordination Function (DCF) and contention-free Time Division Multiplexing Access (TDMA) to coordinate channels’ access between CCH and SCHs. The analysis results show that the proposed mechanism not only can dynamically adapt network load conditions, but gives consideration to communication efficiency both in CCH and SCHs, high throughput can be obtained even in heavy load VANETs.