Performance Evaluation of ETSI GeoNetworking for Vehicular Ad Hoc Networks

The Geo Networking protocol provides single-hop and multi-hop communication in vehicular ad hocnetworks based on IEEE 802.11p/ITS-G5. It has been standardized by the ETSI Technical Committee ITS as part of its Release 1 set of specifications and is expected to be deployed in the next years. This paper presents a performance evaluation of the Geo Networking protocol in its recently published version. Our study assesses the performance of the broadcast forwarding algorithms for multi-hop packet transport that are used to disseminate information in geographical areas for road safety and traffic efficiency applications.

From the algorithms specification in the standard, we derive six variants with different combinations of protocol mechanisms with increasing complexity and assess their performance in terms of reliability, latency, and overhead. The algorithms are evaluated in a reference freeway scenario with bidirectional road traffic and a realistic trace-based mobility model with varying vehicle density. The obtained results indicate that the combination of contention-based and greedy forwarding shows the best overall performance; further functional improvements have a limited performance gain in the studied scenario.

A traffic flow theory based density adopted emergency message dissemination scheme for vehicular ad hoc networks

In traffic safety applications for vehicular ad hoc networks (VANETs), emergency messages have to be disseminated quickly and extensively in order to inform as many vehicles as possible in a short period of time. Hence, the broadcast storm problem is prone to occur. In the past, several approaches have been proposed to solve the problem. Among them, we find counter-, distance-, location-, cluster-, and probabilistic-based schemes. In this paper, we analyze existing protocols and present a novel scheme that is designed to mitigate the broadcast storm problem, reduce the end-to-end latency in real urban scenarios, and deal with the faults that occur during transmission.

The proposed routing protocol assigns a density adopted dynamic back-off time based on traffic flow theory to vehicle. It ensures the dissemination of the emergency message onto every part of the road, and when there is no relay vehicle, the emergency message will be re-transmitted. We use the Groove Net simulator to demonstrate that the proposed scheme has a low collision probability, low overhead and a short end-to-end latency.

Sensing capacity of Cognitive Radio Mobile Ad Hoc Networks

This paper addresses a Cognitive Radio Mobile Ad Hoc Network (CRMAHN) where the licensed users (Primary users – PUs) are mobile nodes. In this scenario, the non-licensed users (Secondary Users – SUs) may opportunistically use the PUs’ band when it is available. Because the availability of the band is determined by the spectrum sensing adopted by each SU, this work characterizes the transmission capability of the SUs (Sensing Capacity) through the characterization of the cases when the SUs sense the spectrum as being vacant. Admitting that PUs are mobile, the SUs must declare the band as being used when the PUs within their sensing region use the band.

Contrarily to other works, our main contribution is the assumption that PUs may also be detected active when they are located outside the SUs’ sensing region, which may frequently occur in CRMAHNs. This effect, known as Spatial False Alarm (SFA), is taken into account through the probability of detection of the PUs located outside the SU’s sensing region, which is derived in this work. Finally, it is shown that SFA degrades the sensing capacity of CRMAHNs, when the number of mobile PUs increases and/or the level of activity of the PUs also increases.

A Street-centric Routing Protocol Based on Micro Topology in Vehicular Ad hoc Networks

In a vehicular ad hoc network (VANET), high mobility and uneven distribution of vehicles are important factors affecting the performance of routing protocols. The high mobility may cause frequent changes of network topology, while the uneven distribution of vehicles may lead to routing failures due to network partition, and even high density of vehicles may cause severe wireless channel contentions in an urban environment. In this paper, we propose a novel concept called the micro topology (MT), which consists of vehicles and wireless links among vehicles along a street as a basic component of routing paths and even the entire network topology.

We abstract the MT model reflecting the dynamic routing-related characteristics in practical urban scenarios along streets, including the effect of mobility of vehicles, signal fading, wireless channel contention and existing data traffic. We first analyze the end side-to-end side routing performance in an MT as a basis of routing decision. Then we propose a novel Street-centric Routing Protocol based on Micro Topology (SRPMT) along the streets for VANETs. Simulation results show that our proposed SRPMT protocol achieves higher data delivery rate and shorter average end-to-end delay compared with the performance of the GPSR and GyTAR.

MAC-CPI-A protocol that prevents collisions at MAC layer in Ad Hoc networks

Collisions due to interference at MAC layer limit the throughput of Ad Hoc networks using IEEE 802.11 protocol at medium and high load conditions. The proposed MAC layer MAC-CPI-A (Collision Prevention due to Interference) protocol prevents collisions due to interference completely. In the proposed protocol every node refrains from beginning its transmission if any node within its maximum interference range' is currently engaged in a data transfer.

The maximum interference range’ for all nodes is pre-computed as a function of average distance between a transmitter and its receiver, the minimum acceptable Signal to Interference and Noise Ratio (SINR), path loss exponent, the carrier sensing range of a receiver and the maximum noise around a receiver. If the sudden change in signal received by a node is more than a significant' value defined by the maximum interference range’, then the node infers that another node within its maximum interference range' has begun its transmission. A scheme for generation of a new signal indicating a sudden increase or decrease in received signal of greater than significant’ value has been detailed.

Design and development of peer to peer web caching technique for mobile Ad-Hoc networks: A review

In this paper we analyze one technique for web caching in MANET. MANET stands for Mobile Ad HocNetwork which is an evolving concept. There are many emerging researches focused on MANET aspects such as routing and caching. Among them, the lack of efforts done on MANET web caching is acknowledged. As the node in MANET is moving, the web caching is difficult task.

The paper reviews the traditional web caching techniques to improve the performance of MANET. In previous techniques, Better Approach to Mobile Ad-Hoc (B.A.T.M.A.N.) is a web caching protocol which is implemented for MANET. The overall performance of B.A.T.M.A.N. is more time consuming. The proposed technique improves the performance of web application in MANET by reducing internet bandwidth. Also preserves the energy consumption. This peer to peer web caching concept purely focused on web applications in MANET.

Community-Based Bus System as Routing Backbone for Vehicular Ad Hoc Networks

Low delivery latency and high delivery ratio are two key goals in the design of routing schemes in Vehicular Ad Hoc Networks (VANETs). The existing routing schemes utilize real-time information (e.g., Geographical position and vehicle density) and historical information (e.g., Contacts of vehicles), which usually suffer from a long delivery latency and a low delivery ratio. Inspired by the unique features of bus systems such as wide coverage, fixed routes and regular service, we propose to use the bus systems as routing backbones of VANETs. In this work, we present a Community-based Bus System (CBS) which consists of two components: a community-based backbone and a routing scheme over the backbone.

We collect real traces of 2515 buses in Beijing and build a community-based backbone by applying community detection techniques in the Beijing bus system. A two-level routing scheme is proposed to operate over the backbone. The proposed routing scheme performs sequentially in the inter-community level and the intra-community level, and is able to support message delivery to both mobile vehicles and specific locations/areas. Extensive experiments are conducted on the real trace data of the Beijing bus system and the results show that CBS can significantly lower the delivery latency and improve the delivery ratio. CBS is applicable to any bus-based VANETs.

Cooperative Data Scheduling in Hybrid Vehicular Ad Hoc Networks: VANET as a Software Defined Network

This paper presents the first study on scheduling for cooperative data dissemination in a hybrid infrastructure-to-vehicle (I2V) and vehicle-to-vehicle (V2V) communication environment. We formulate the novel problem of cooperative data scheduling (CDS). Each vehicle informs the road-side unit (RSU) the list of its current neighboring vehicles and the identifiers of the retrieved and newly requested data. The RSU then selects sender and receiver vehicles and corresponding data for V2V communication, while it simultaneously broadcasts a data item to vehicles that are instructed to tune into the I2V channel.

The goal is to maximize the number of vehicles that retrieve their requested data. We prove that CDS is NP-hard by constructing a polynomial-time reduction from the Maximum Weighted Independent Set (MWIS) problem. Scheduling decisions are made by transforming CDS to MWIS and using a greedy method to approximately solve MWIS. We build a simulation model based on realistic traffic and communication characteristics and demonstrate the superiority and scalability of the proposed solution. The proposed model and solution, which are based on the centralized scheduler at the RSU, represent the first known vehicular ad hoc network (VANET) implementation of software defined network (SDN) concept.

Comparison between AODV and DSDV routing protocols in mobile Ad-hoc Network (MANET)

Mobile Ad-hoc Networks (MANETs) have been investigated deeply during the recent years due to their success in both civilian and military applications. MANETs are formed dynamically by an autonomous system of mobile nodes that are connected via wireless links without using an existing fixed network infrastructure or any centralized administration. The nodes organize themselves randomly and are free to move anytime, anywhere; thus, the network’s wireless topology may change hastily and arbitrarily.

In this paper, a comparison between two well-known routing protocols have been evaluated. The two routing protocols are Ad-hoc On-demand Distance Vector AODV and Destination-Sequenced Distance-Vector DSDV. The simulation results show that AODV routing protocol has performed better than DSDV routing protocol in term of throughput, delivery ratio.

Cognitive Radio-Aware Transport Protocol for Mobile Ad Hoc Networks

With the proliferation of new wireless service, scarce wireless resources is expected to become a critical issue. For this reason, cognitive radio mobile ad hoc networks (CogMANET) are being developed as a promising solution to this problem. However, in CogMANET, channel switching is inherently necessary whenever a primary user with a license appears on the channel. Allowing secondary users to choose an available channel from among a wide spectrum range thus enables reliable communication in this context, but communication characteristics such as bottleneck bandwidth and RTT will change with channel switch.

In response to this change, TCP has to adaptively update its congestion window (cwnd) to make an efficient use of the available resources. For this purpose, TCP CRAHN was proposed for CogMANET. In this paper, TCP CRAHN is first evaluated in cases where bottleneck bandwidth and RTT drastically change. Based on these results, TCP CoBA is proposed to further improve the throughput of the above use cases. TCP CoBA updates the cwnd based upon the available buffer space in the relay node upon channel switch, as well as other communication characteristics. Through simulations, we show that compared with TCP CRAHN, TCP CoBA improves the throughput by up to 200 percent.