A Dual Ring Connectivity Model for VANET Under Heterogeneous Traffic Flow

Vehicular ad-hoc network (VANET) is characterized as a highly dynamic wireless network due to the dynamic connectivity of the network nodes. To achieve better connectivity under such dynamic conditions, an optimal transmission strategy is required to direct the information flow between the nodes. Earlier studies on VANET’s overlook the characteristics of heterogeneity in vehicle types, traffic structure, flow for density estimation, and connectivity observation. In this paper, we have proposed a heterogeneous traffic flow based dual ring connectivity model to enhance both the message disseminations and network connectivity. In our proposed model the availability of different types of vehicles on the road, such as, cars, buses, etc., are introduced in an attempt to propose a new communication structure for moving vehicles in VANETl under cooperative transmission in heterogeneous traffic flow. The model is based on the dual-ring structure that forms the primary and secondary rings of vehicular communication. During message disseminations, Slow speed vehicles (buses) on the secondary ring provide a backup path of communication for high speed vehicles (cars) moving on the primary ring. The Slow speed vehicles act as the intermediate nodes in the aforementioned connectivity model that helps improve the network coverage and end-to-end data delivery. For the evaluation and the implementation of dual-ring model a clustering routing scheme warning energy aware cluster-head is adopted that also caters for the energy optimization. The implemented dual-ring message delivery scheme under the cluster-head based routing technique does show improved network coverage and connectivity dynamics even under the multi-hop communication system.     

RPB-MD: Providing robust message dissemination for vehicular ad hoc networks

To improve traffic safety and efficiency, it is vital to reliably send traffic-related messages to vehicles in the targeted region in vehicular ad hoc networks (VANETs). In this paper, we propose a novel scheme, relative position based message dissemination (RPB-MD), to reliably and efficiently disseminate messages to the vehicles in the zone-of-relevance. Firstly, the relative position based (RPB) addressing model is proposed to effectively define the intended receivers in the zone-of-relevance. To ensure high message delivery ratio and low delivery delay, directional greedy broadcast routing (DGBR) is introduced to make a group of candidate nodes hold the message for high reliability. Moreover, to guarantee efficiency, the protocol time parameters are designed adaptively according to the message attributes and local vehicular traffic density. The protocol feasibility is analyzed to illustrate the robustness and reliability of RPB-MD. Simulation results show that RPB-MD, compared with representative existing schemes, achieves high delivery ratio, limited overhead, reasonable delay and high network reachability under different vehicular traffic density and data sending rate.     

ARMS-EGR—Adaptive ranking and mobile sink-enabled energy-efficient geographic routing protocol in flying ad hoc networks

Unmanned aerial vehicles (UAVs) have become widespread because of their involvement in a variety of applications. The task of designing the energy-efficient routing between UAVs has been considered a matter of great interest due to the inherent challenges of controlling the dynamics exhibited by UAVs. Energy limitations are considered the main limitations of UAVs. This research paper proposes a novel routing protocol, adaptive ranking and mobile sink (MS)-enabled energy-efficient geographic routing (ARMS-EGR) for flying ad hoc networks. In ARMS-EGR, the whole network is partitioned into cells. The cell contains cell members (CM) and cell heads (CHs). The CH works as a cluster head. Additionally, two MSs have been used to collect data captured by CM. Multihop communication on the network leads to an increase in traffic and consumes the energy of the UAVs located near the base station (BS). MSs are used for power distribution and load balancing across the network. Adaptive ranking of forwarder UAVs and CHs is performed during intracell and intercell multihop communication, respectively, using adaptive ranking. A cell with one-hop communication can directly send packets to the MS, but the ARMS-EGR routing protocol has been proposed for multihop communication. The proposed approach is simulated in NS-2.35 software. The results show that end-to-end latency and power consumption during packet transmission are greatly minimized. ARMS-EGR also demonstrates improvements in message success rates, number of alive nodes, and packet delivery ratio, making ARMS-EGR particularly suitable for flying ad hoc networks (FANETs).     

基于车联网WAVE的多跳路由连接中断预测算法

当信息源车辆与信息目标车辆之间不能通过一跳来完成信息交互时,车辆间多跳路由连接的建立是保证车联网WAVE中信息源车辆和信息目标车辆之间能够进行信息传递的关键。通过研究和分析快速多跳路由算法FMHR得知,车联网中各节点车辆之间建立起来的多跳路由连接会因各节点车辆之间的速度不匹配而时常发生通信中断,针对这一问题,试着在原有算法中增加路由连接中断的预测方法,并使用支持IEEE 802.11p的开源软件NCTUns-6.0建立相关仿真实验,结果表明,增加路由连接中断的预测方法可改善车辆之间信息传递的效率。     

A probabilistic routing algorithm based on node communication capability and message strength

In delay-tolerant networks (DTN), node connection time and message transmission time are two important influencing factors that can improve the delivery rate. In this paper, we first define a new concept called communication capability (CC) and then apply this concept to the delivery predictability formulation in Prophet and improve it. Then, in Prophet, the selection of relay nodes relies only on the delivery predictability and ignores the caching and forwarding capability of the node. Therefore, we combine delivery predictability, buffering, and forwarding capability to develop a new adaptive relay node selection strategy. Subsequently, we define two metrics called message priority (MP) and message strength (MS). The node forwards messages sequentially based on message priority and discards messages based on message strength. Finally, we present a probabilistic routing algorithm based on node communication capability and message strength (CAMS). The simulation results show that compared with traditional routing algorithms, the CAMS can effectively improve the message delivery rate, reduce the overhead ratio, and keep average hop counts low.     

Analysis and Design of Warning Delivery Service in Intervehicular Networks

This paper focuses on inter-vehicular networks providing warning delivery service. As soon as a danger is detected, the propagation of a warning message is triggered, with the aim of guaranteeing a safety area around the point in which the danger is located. Multiple broadcast cycles can be generated so that a given lifetime of the safety area is guaranteed. The service is based on multi-hop ad hoc inter-vehicular communications with a probabilistic choice of the relay nodes. The scenario we consider consists of high speed streets, such as highways, in which vehicles exhibit one-dimensional movements along the direction of the road. We propose an analytical model for the study of this service and derive performance indices such as the probability that a vehicle is informed, the average number of duplicate messages received by a vehicle and the average delay. Moreover, we use the model to discuss system design issues, which include the proper setting of the forwarding probability at each vehicle, so that a given probability to receive the warning can be guaranteed to all vehicles in the safety area. The model is validated against simulation results. Since it is very accurate, the model can be instrumental to the performance evaluation and design of broadcasting techniques in inter-vehicular networks.     

A mobicast routing protocol with carry‐and‐forward in vehicular ad hoc networks

In vehicular networks, safety and comfort applications are two quite different kinds of applications to avoid the emergency traffic accident and enjoy the non‐emergency entertainment. The comfort application drives the challenges of new non‐emergency entertainments for vehicular ad hoc networks (VANETs). The comfort application usually keeps the delay‐tolerant capability; that is, messages initiated from a specific vehicle at time t can be delivered through VANETs to some vehicles within a given constrained delay time λ. In this paper, we investigate a new mobicast protocol to support comfort applications for a highway scenario in VANETs. All vehicles are located in a geographic zone (denoted as zone of relevance (ZOR)) at time t; the mobicast routing must disseminate the data message initiated from a specific vehicle to all vehicles that have ever appeared in ZOR at time t. This data dissemination must be performed before time t + λ through the carry‐and‐forward technique. In addition, the temporary network fragmentation problem is considered in our protocol design. Also, the low degree of channel utilization is kept to reserve the resource for safety applications. To illustrate the performance achievement, simulation results are examined in terms of message overhead, dissemination success rate, and accumulative packet delivery delay. Copyright © 2012 John Wiley & Sons, Ltd.     

Efficient geocasting with multi-target regions in mobile multi-hop wireless networks

Geocasting, a variation on the notion of multicasting, is a mechanism to deliver messages of interest to all nodes within a certain geographical target region. Although several geocasting protocols have already been proposed for multi-hop wireless networks, most of these algorithms consider a “single” target region only. Here, when more than one target regions need to receive the same geocast messages, multiple transmissions need to be initiated separately by the message source. This causes significant performance degradation due to redundant packet transmissions, and it becomes more severe as the number of target regions increase. To solve this problem, we propose a basic scheme and its variations which utilize the geometric concept of “Fermat point” to determine the optimal junction point among multiple geocast regions from the source node. Our simulation study using ns-2 shows that the proposed schemes can effectively reduce the overhead of message delivery while maintaining a high delivery ratio in mobile multi-hop wireless networks.     

DirMove: direction of movement based routing in DTN architecture for post-disaster scenario

Network architecture based on opportunistic Delay Tolerant Network (DTN) is best applicable for post-disaster scenarios, where the controlling point of relief work is any fixed point like a local school building or a hospital, whose location is known to everyone. In this work, 4-tier network architecture for post-disaster relief and situation analysis is proposed. The disaster struck area has been divided into clusters known as Shelter Points (SP). The architecture consists of mobile Relief Workers (RW) at tier 1, Throw boxes (TB) at tier 2 placed at fixed locations within SPs. Data Mules (DM) like vehicles, boats, etc. operate at tier 3 that provide inter-SP connectivity. Master Control Station (MCS) is placed at tier 4. The RWs are provided with smart-phones that act as mobile nodes. The mobile nodes collect information from the disaster incident area and send that information to the TB of its SP, using DTN as the communication technology. The messages are then forwarded to the MCS via the DMs. Based on this architecture, a novel DTN routing protocol is proposed. The routing strategy works by tracking recent direction of movement of mobile nodes by measuring their consecutive distances from the destination at two different instants. If any node moves away from the destination, then it is very unlikely to carry its messages towards the destination. For a node, the fittest node among all its neighbours is selected as the next hop. The fittest node is selected using parameters like past history of successful delivery and delivery latency, current direction of movement and node’s recent proximity to the destination. Issues related to routing such as fitness of a node for message delivery, buffer management, packet drop and node energy have been considered. The routing protocol has been implemented in the Opportunistic Networks Environment (ONE) simulator with customized mobility models. It is compared with existing standard DTN routing protocols for efficiency. It is found to reduce message delivery latency and improve message delivery ratio by incurring a small overhead .