Lina Zhu

LSGO: Link State aware Geographic Opportunistic routing protocol for VANETs

Robust and efficient data delivery in vehicular ad hoc networks (VANETs) with high mobility is a challenging issue due to dynamic topology changes and unstable wireless links. The opportunistic routing protocols can improve the reliability of routing by making full use of the broadcast characteristics and assist in data transmission through additional backup links. In this paper, we propose a Link State aware Geographic Opportunistic routing protocol (LSGO) which exploits a combination of geographic location and the link state information as the routing metric. The LSGO aims to improve the reliability of data transmission in a highly dynamic environment, which selects the forwarders and prioritizes them based on the vehicle’s geographic location and the link’s quality. We compare the performance of LSGO with GpsrJ + which removes the unnecessary stop at a junction and greedy traffic aware routing protocol (GyTAR) using network simulator ns-2. The simulation results show that it opens more nodes to participate in the opportunistic data forwarding and increases a connection’s throughput while using no more network capacity than traditional routing. In the simulation, compared with other two protocols, when the number of vehicles and the average vehicle velocity increase, LSGO’s packet dropping rate is reduced and the network throughput is improved.

A Three-Dimensional Scenario Oriented Routing Protocol in Vehicular Ad Hoc Networks

In realistic Vehicular Ad hoc NETworks (VANETs), due to the existence of three-dimensional (3D) scenarios, such as the viaduct, tunnel and ramp, the distribution of vehicles is non-planar. However, existing routing protocols in VANETs are mainly analyzed and designed based on ideal plane scenarios. We call them plane-based routing protocols. In this paper, we focus on routing issues in 3D scenarios of VANETs. Through analysis, we demonstrate that applied in 3D scenarios, the plane-based routing protocols suffer a series of severe problems, i.e., hop count increases and delivery ratio decreases. To address the issues, we propose a Three-dimensional scenario oriented Routing (TDR) protocol for VANETs. Utilizing three-dimensional information, TDR establishes a route hop by hop and transmits packets as far as possible to the optimal immediate neighbor node which is located on the same plane with the current forwarding node. In the end, a comparison between TDR and the existing protocol GPSR is conducted on the network simulator NS2. The results show that TDR has higher delivery ratio but lower end-to-end delay and average hops.

A link state aware geographic routing protocol for vehicular ad hoc networks

In vehicular ad hoc networks (VANETs), the communication links are inherently unstable due to vehicles’ mobility and various impairment of radio signal. Existing geographic routing protocols often choose the next hop according to the greedy forwarding, regardless of the link’s quality and transmission reliability. The successful packet delivery rate is decreased in non-ideal communication links. Consequently, the reliability of data transmission is worse and the network throughput is declined. In this paper, we propose a routing protocol called link state aware geographic routing protocol (LSGR) for VANETs. In LSGR, a routing metric called expected one-transmission advance (EOA) is contrived to improve the greedy forwarding algorithm by explicitly incorporating the link state and packet’s advance. Routing with the EOA metric, one can improve the transmission efficiency by diminishing transmission failures. Simulation results show that LSGR can achieve a higher throughput and packet delivery rate than the geographic routing protocols that adopt the traditional greedy forwarding.

A vehicle density and load aware routing protocol for VANETs in city scenarios

Due to the characteristics of Vehicular Ad Hoc Networks (VANETs), i.e. highly dynamic network topology, large network size and non-uniform node distribution, it is a great challenge to develop a routing protocol to ensure efficient data transmission. In this paper, we propose a Vehicle Density and Load Aware routing protocol for VANETs called VDLA. VDLA adopts sequential selection of junctions to construct the route. The selection is based on the real-time vehicle density, the traffic load of the corresponding road segment and the distance to the destination. The network information is collected by a decentralized mechanism. Through factoring in these metrics, the packets are avoided being sent to roads where network is disconnected and the network load is balanced to mitigate network congestion. Thereby VDLA can improve the efficiency of data transmission. By virtue of the information collected at every junction, the decision about which junction the packet should forward to is made before the junctions to reduce the unnecessary hops. In the simulation, we compare VDLA with GPCR, one of the most widely used routing protocols in VANET. The results show the superiority of VDLA in terms of average end to end delay and packet delivery ratio over GPCR.

Hello scheme for vehicular ad hoc networks: analysis and design

In vehicular ad hoc networks (VANETs), essentially the information of one-hop neighbors is important for data delivery. In a general way, each node broadcasts short packets, i.e., hello packets, to indicate its appearance and establishes a neighbor table for storing neighbor information through receiving others’ hello packets. As a popular approach, it is named as a hello scheme. Determining the validity of the neighbor table, a hello scheme is vital to routing protocols in VANETs. However, a hello scheme with high accuracy and low overhead is severely challenged due to the highly dynamic topology and restricted vehicle mobility in VANETs. To address the issue, it is crucial to optimally configure two key parameters, called as hello interval (HI) and timeout interval (TI), respectively. In this article, a probability model of the hello scheme for VANETs is proposed. It is used to analyze factors affecting the two key parameters. Depending on derivation results, an effective local information-based adaptive hello scheme (LAH) is proposed subsequently. It utilizes the local information, i.e., the variation of neighbor table and received hello packets, to adjust HI and TI adaptively. According to different TI adjustment algorithms, four variants of LAH are designed as LAH-I, LAH-L, LAH-1, and LAH-2. In the end, a comparison between LAH schemes and existing three solutions is conducted to evaluate the performance. Results verify that the proposed LAH schemes are capable of obtaining higher accuracy of neighbor table and lower overhead.

Performance of Routing Protocols in Very Large Scale Wireless Sensor Networks

With deployment of thousands or even tens of thousands of sensors in a wireless sensor network (WSN) feasible, the scalability of routing protocols has drawn a lot of attention. Routing protocols in ad hoc networks, such as Ad hoc On-demand Distance Vector (AODV) protocol and its enhanced versions provide one option for the routing design in a large scale WSN. Combining the strengths of AODV with link layer feedback (AODV-LLF) and AODV/Jr, an efficient routing protocol named AODV with Route Identification and RREP Capturing (AODV-RIRC) is proposed to scale up the network scope. AODV-RIRC reduces route search times and thus cut down the control overhead effectively. In our work, based on MIRAI-SF platform, simulations are implemented to prove the scalability of AODV-RIRC when applied to a large scale network with nodes up to 10000, and meanwhile to reveal the potential problems of ad hoc routing protocols when they are applied to a large scale WSN. The simulation results verify that AODV-RIRC outperforms the AODV family protocols in terms of control overhead, energy consumption, and route building time etc.

Connectivity-Sensed routing protocol for vehicular ad hoc networks: analysis and design

With the fast development of vehicular ad hoc networks (VANETs), various VANET applications, especially safety and infotainment service, have stronger requirements for reliable network connectivity. Intermittent connectivity has become a thorny problem in VANETs, which causes unreliable vehicle to vehicle (V2V) connection due to high vehicle mobility. In this paper, we have studied the network connectivity using a stochastic analysis model and then we prove average intervehicle distance influences VANET connectivity greatly. Based on our analysis, we propose a connectivity-sensed routing protocol (CSR) for VANETs in urban scenario. CSR utilizes vehicle distribution information collected by intersection infrastructure to help vehicles select a road not only with progress to destination but also with better network connectivity. Moreover, simulation results demonstrate that the CSR protocol achieves much lower end-to-end delay, higher delivery rate, and higher throughput than traditional routing protocols.

An effective routing protocol for intermittently connected vehicular ad hoc networks

Vehicular ad hoc network (VANET) is suffering from intermittent connectivity problems due to vehicles mobility, which challenge routing protocols. To address the issue, we propose a novel strategy called Reactive Pseudo-suboptimal-path Selection routing protocol (RPS). It is different from existing solutions which rely on vehicles physical movement to carry packets in intermittent connectivity scenarios. RPS gives the recently passed intersection a chance to select a new path from suboptimal-path unilaterally determined by local knowledge. Thus it improves the probability of transmission through wireless channels. A comparison between RPS and current protocols is presented and results show that the proposed RPS has higher packet delivery ratio and lower end-to-end delay.

Scalable Cluster-based Routing in Large Wireless Sensor Networks

Large control overhead is the leading factor limiting the scalability of wireless sensor networks (WSNs). Clustering network nodes is an efficient solution, and Passive Clustering (PC) is one of the most efficient clustering methods. In this letter, we propose an improved PC-based route building scheme, named Route Reply (RREP) Broadcast with Passive Clustering (in short RBPC). Through broadcasting RREP packets on an expanding ring to build route, sensor nodes cache their route to the sink node, which reduces the total route search times and thus the control overhead. Simulation results are also provided to show the efficiency of the proposed RBPC in terms of reduced overhead and energy consumption, and it is also shown that RBPC outperforms AODV/PC in the delivery ratio.

Dynamic Overlay-Based Scheme for Video Delivery over VANETs

As a technical method over VANETs, video delivery has the potential power to enhance the application experience associated with traffic safety, management and infotainment. The experience of user is seriously affected by the quality of the video display. Therefore, Quality of Experience (QoE) enhancement for video delivery in VANETs is an important issue. However, the high mobility and dynamic nature of VANETs cause the dynamic topology which poses a significant challenge for video delivery. In this paper, we propose a user-oriented cluster-based solution called CDOV (Cluster and Dynamic Overlay based video delivery over VANETs), which combine the novel clustering algorithm and the dynamic overlay structure into a novel structure. Simulation results show that CDOV scheme for video delivery over VANETs significantly reduces the startup delay and increases the delivery rate compared with the gossiping-based scheme.