Incentive based scheme for improving data availability in vehicular ad-hoc networks

Vehicular networks are popular in recent years to provide low cost communication medium during mobility. Vehicular Delay Tolerant Networks (DTNs) are one of the major categories of emerging technology. DTNs work on carry and forward mechanism to deliver data to the destination. The network performance gets severely affected due to reluctance shown by selfish nodes where few nodes show no interest in forwarding others data due to lack of any personal profit. The proposed mechanism is based on coalition game theory and discusses about incentive based mechanism which provides incentive to nodes which are forwarding data to forward to destination and motivates other vehicles in the network to participate in coalition to forward data. This scheme not only encourages other selfish nodes to forward their private data and other nodes’ public data as early as possible to destination but also increases reliability in the network as more nodes show their interest in selected routing protocol. The proposed scheme outperforms in overall benefit earned by individual node and whole coalition, and increases mutual cooperation which improves availability of data in the network.     

Directed information dissemination in vehicular ad-hoc networks

In this article, we utilize the idea of multipoint relays (MPRs) found in literature (Jacquet et al. in Proceedings of IEEE INMIC, 2001), to propagate accident information in a restricted way (e.g., only backwards). We devise an algorithm to identify MPRs that are geographically situated behind a particular node using only its neighbor table, and speed information of the neighboring vehicles. With the identification of the backward MPRs, it is possible to restrict the information dissemination to vehicles behind a particular vehicular ad-hoc network (VANET) node only. This might benefit the approaching vehicles so that the driver could take preventive measures in real-time since he/she will have an indication of the severity of road conditions ahead. We assume that there exists an inter vehicular network using optimized link state routing (OLSR) where accident information can be propagated to all nodes using on-going OLSR control packets. We envision our application will run on top of existing routing protocols (e.g., OLSR), thereby resulting in very little integration effort, and retaining OLSR’s reduced network traffic advantage through the use of MPRs. We analyze our back MPR identification algorithm in a detailed manner. We also show that by using our approach the location of the accident alert instigator node could be pinpointed if a subset of the nodes in the same VANET know their geographical positions. We use VANET mobility models generated by SUMO into NS-3 for our simulations, and also perform preliminary experiments to verify the algorithm’s effectiveness. Our analysis and experiments show favorable results.     

Adaptive TDMA slot assignment protocol for vehicular ad-hoc networks

This paper proposes a novel adaptive time division multiple access (TDMA) slot assignment protocol (ATSA) for vehicular ad-hoc networks. ATSA divides different sets of time slots according to vehicles moving in opposite directions. When a node accesses the networks, it choices a frame length and competes a slot based on its direction and location to communication with the other nodes. Based on the binary tree algorithm, the frame length is dynamically doubled or shortened, and the ratio of two slot sets is adjusted to decrease the probability of transmission collisions. The theoretical analysis proves ATSA protocol can reduce the time delay at least 20% than the media access control protocol for vehicular ad-hoc networks (VeMAC) and 30% than the ad-hoc. The simulation experiment shows that ATSA has a good scalability and the collisions would be reduced about 50% than VeMAC, channel utilization is significantly improved than several existing protocols.     

Information-centric dissemination protocol for safety information in vehicular ad-hoc networks

In vehicular networks, efficient safety information dissemination is a crucial issue. Unique characteristics of such an environment like highly mobility, fast topology changing, short-lived and intermittent connectivity pose challenges for safety information dissemination. Although IEEE 802.11p is standardized as an amendment to the IEEE 802.11 for connection-based wireless communication in vehicular environments (WAVE), it is still an open topic and a challenge to efficiently handle high mobility, intermittent connectivity, and spontaneous characteristics of vehicles on the roadway during wireless communication. This paper exploits information centric networking approach to design an efficient information dissemination protocol for such a challenging environment. The protocol is designed for both communication schemes in vehicular networks including vehicles-to-vehicles and vehicle-to-road. By focusing on information object itself, instead of end-to-end connection, the proposed mechanism supports fast and efficient data dissemination among multiple content consumers and multiple content providers, removing dependence on end-to-end connection between two nodes, thus improve the overall network performance. Through experimental results over different scenarios, we show that the proposed protocol achieves a significant improvement in term of the network performance compared to the conventional approach (WAVE).     

On minimizing the system information age in vehicular ad-hoc networks via efficient scheduling and piggybacking

Recent advances in vehicular networks have enforced researchers to focus on various information dissemination techniques. Exchanging information among the vehicles is imperative due to the ever-changing network topology in vehicular networks. However, random transmitter selection in traditional CSMA based channel access mechanism limits the delay performance. Data, such as state information, is often time critical, and hence, efficient information dissemination techniques to improve delay performance are essential. In this work, we aim to minimize the average system age which is the mean number of time slots old a vehicle’s information is at all other vehicles in the network. To achieve this, we explore the benefits of simultaneous transmission along with piggybacking of information for multi-hop communication. While allowing simultaneous transmission guarantees faster dissemination of information, piggybacking facilitates dissemination of more information per transmission, thereby keeping the network more updated. We have also analysed the relationship between piggybacked information and number of vehicles in the network. Simulation results show improvement in network performance. Our analytical results are in good agreement with the simulation results.     

A preemption‐based scheduling algorithm for WiMAX networks

Several scheduling techniques were designed for the base station (BS) of IEEE 802.16e wireless interoperability of microwave access networks. However, depending on the BS scheduler alone to determine the servicing order of each connection might affect the accuracy of the scheduling process because the BS does not necessarily have enough up‐to‐date information about the current state of the connections at the subscriber station. In this paper, we propose a preemption‐based scheduling algorithm that focuses on improving the quality of service requirements of real‐time service flow classes. The proposed algorithm incorporates two schedulers, one at the BS and another one at the subscriber station. We have implemented and integrated the proposed algorithm with the network simulator NS2 using the Network and Distributed Systems Laboratory wireless interoperability of microwave access module. Simulation results have shown that the proposed approach outperforms other scheduling algorithms in terms of enhancing the throughput and the average delay of real‐time quality of service classes. Copyright © 2013 John Wiley & Sons, Ltd.     

Fast randomized algorithm for 2-hops clustering in vehicular ad-hoc networks

Vehicular Ad-Hoc Networks (VANETs) enable inter vehicle wireless communication as well as communication with road side equipment. Warning messages can be exchanged among nearby vehicles, helping to predict dangerous situations, and thus improving road safety. Such safety messages require fast delivery and minimal delay to local areas, in order for them to be effective. Therefore, a fast and efficient channel access scheme is required. A feasible solution, derived from the Mobile Ad-Hoc Networks (MANETs) field, groups nodes into smaller manageable sections called clusters. Such an approach can be beneficial for locally delivering messages under strict time constraints. In this paper, a Hierarchical Clustering Algorithm (HCA) is presented. HCA is a distributed randomized algorithm, which manages channel access by forming three hierarchy clusters. The proposed channel access scheme enables delay bounded reliable communication. Unlike other common clustering algorithm for VANETs, HCA does not require the knowledge of the vehicles’ locations. This feature guarantees accurate operation even when localization systems such as GPS are not available. The running time and message complexity were analyzed and simulated. Simulation results show that the algorithm behaves well especially under realistic mobility patterns; therefore, it is a suitable solution for channel access scheme for VANETs.     

An energy‐saving‐centric downlink scheduling scheme for WiMAX networks

This study proposes an energy‐saving‐centric downlink scheduling scheme to support efficient power utilization and to satisfy the QoS requirements. The base station considers the queue lengths of mobile stations with real‐time and non‐real‐time connections and considers their QoS requirements to determine the sleeping parameters when the mobile stations issue sleep requests. The proposed scheme appropriately reschedules the sleep‐requesting mobile station to transmit its queued packets for optimal power‐saving efficiency. The QoS requirement is considered as the constraint during traffic rescheduling. The treatment of real‐time connections generally requires a trade‐off of the delay requirement and the longer sleep window, and the non‐real‐time connections must concern the packet drop and minimum data rates when performing the energy‐centric scheduling. Two rescheduling algorithms, that is, whole and partial reschedules, are proposed and analyzed in this paper. The whole‐reschedule scheme provides improved energy‐saving performance at the cost of tolerable longer delay and computing complexity when compared with the partial‐reschedule scheme. Our simulation results indicated that both schemes not only guarantee the desired QoS but also achieve superior energy‐saving efficiency to that of traditional scheduling. Copyright © 2012 John Wiley & Sons, Ltd.     

A comprehensive survey of network coding in vehicular ad-hoc networks

Network coding is a data processing technique in which the flow of digital data is optimized in a network by transmitting a composite of two or more messages to make the network more robust. Network coding has been used in traditional and emerging wireless networks to overcome the communications issues of these networks. It also plays an important role in the area of vehicular ad-hoc networks (VANETs) to meet the challenges like high mobility, rapidly changing topology, and intermittent connectivity. VANETs consist of network of vehicles in which they communicate with each other to ensure road safety, free flow of traffic, and ease of journey for the passengers. It is now considered to be the most valuable concept for improving efficiency and safety of future transportation. However, this field has a lot of challenges to deal with. This paper presents a comprehensive survey of network coding schemes in VANETs. We have classified different applications like content distribution, multimedia streaming, cooperative downloading, data dissemination, and summarized other key areas of VANETs in which network coding schemes are implemented. This research work will provide a clear understanding to the readers about how network coding is implemented in these schemes in VANETs to improve performance, reduce delay, and make the network more efficient.     

A distributed laxity-based priority scheduling scheme for time-sensitive traffic in mobile ad hoc networks

Characteristics of Mobile Ad hoc Networks such as shared broadcast channel, bandwidth and battery power limitations, highly dynamic topology, and location dependent errors, make provisioning of quality of service (QoS) in such networks very difficult. The Medium Access Control (MAC) layer plays a very important role as far as QoS is concerned. The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. We have proposed a new MAC layer protocol that includes a laxity-based priority scheduling scheme and an associated back-off scheme, for supporting time-sensitive traffic. In the proposed scheduling scheme, we select the next packet to be transmitted, based on its priority value which takes into consideration the uniform laxity budget of the packet, the current packet delivery ratio of the flow to which the packet belongs, and the packet delivery ratio desired by the user. The back-off mechanism devised by us grants a node access to the channel, based on the rank of its highest priority packet in comparison to other such packets queued at nodes in the neighborhood of the current node. We have studied the performance of our protocol that combines a packet scheduling scheme and a channel access scheme through simulation experiments, and the simulation results show that our protocol exhibits a significant improvement in packet delivery ratio under bounded end-to-end delay requirements, compared to the existing 802.11 DCF and the Distributed Priority Scheduling scheme proposed recently in [ACM Wireless Networks Journal 8 (5) (2002) 455–466; Proceedings of ACM MOBICOM '01, July 2001, pp. 200–209].     

Adaptive load distribution approach based on congestion control scheme in ad-hoc networks

The ‘load distribution’ proposition in mobile ad-hoc networks (MANETs) is accomplishing great stimulation. This is because of the phenomenal facets it possesses including advanced network resilience, reliability and performance. Though there are other leading network layer routing protocols, but they radically utilise single-path communication paradigm, which is why they fail in achieving efficient load distribution in a network. Via this paper, we propose an efficient cross-layer adaptive load distribution approach to capitalise network’s channel utilisation and to rapidly adapt to dynamic wireless channel characteristic changes. The proposed method modifies the load balanced congestion adaptive routing (LBCAR) protocol and is developed using dynamic load distribution technique, by pioneering (i) novel parameters, which report for the availability of route pertaining to minimum traffic load and better link lifetime and also adapt according to varying available network resources; (ii) an absolute dynamic method to lessen the redundant route oscillations which further reduces the routing instabilities. The simulation results demonstrate the usefulness of the proposed method and yields better results in comparison to LBCAR and standard instead of dynamic ource outing, it is dynamic source routing (DSR) protocol.     

CCH: a clique based asymmetric rendezvous scheme for cognitive radio ad-hoc networks

Wireless Networks - Rendezvous (RDV) in cognitive radio ad-hoc networks (CRAHNs) is one of the key ways for a pair of unknown cognitive radio users to initiate communications. CRAHN is a...     

A secure and trust based on-demand multipath routing scheme for self-organized mobile ad-hoc networks

A mobile ad hoc network (MANET) is a self-configurable network connected by wireless links. This type of network is only suitable for provisional communication links as it is infrastructure-less and there is no centralized control. Providing QoS and security aware routing is a challenging task in this type of network due to dynamic topology and limited resources. The main purpose of secure and trust based on-demand multipath routing is to find trust based secure route from source to destination which will satisfy two or more end to end QoS constraints. In this paper, the standard ad hoc on-demand multi-path distance vector protocol is extended as the base routing protocol to evaluate this model. The proposed mesh based multipath routing scheme to discover all possible secure paths using secure adjacent position trust verification protocol and better link optimal path find by the Dolphin Echolocation Algorithm for efficient communication in MANET. The performance analysis and numerical results show that our proposed routing protocol produces better packet delivery ratio, reduced packet delay, reduced overheads and provide security against vulnerabilities and attacks.     

A roadside unit‐based localization scheme for vehicular ad hoc networks

Vehicular Ad Hoc Networks (VANETs), designed to ensure the safety and comfort of passengers via the exchange of information amongst nearby vehicles or between the vehicles and Roadside Units (RSUs), have attracted particular attention. However, the success of many VANET applications depends on their ability to estimate the vehicle position with a high degree of precision, and thus, many vehicle localization schemes have been proposed. Many of these schemes are based on vehicle‐mounted Global Positioning System (GPS) receivers. However, the GPS signals are easily disturbed or obstructed. Although this problem can be resolved by vehicle‐to‐vehicle communication schemes, such schemes are effective only in VANETs with a high traffic density. Accordingly, this paper presents a VANET localization scheme in which each vehicle estimates its location on the basis of beacon messages broadcast periodically by pairs of RSUs deployed on either side of the road. In addition, three enhancements to the proposed scheme are presented for the RSU deployment, RSU beacon collisions, and RSU failures. Overall, the ns‐2 simulation results show that the localization scheme achieves a lower localization error than existing solutions on the basis of vehicle‐to‐vehicle communications and is robust toward changes in the traffic density and the vehicle speed. Copyright © 2012 John Wiley & Sons, Ltd.     

EASBVN: efficient approximation scheme for broadcasting in vehicular networks

Wireless Networks - Vehicular ad-hoc networks (VANETs) suffer from dis-connectivity due to very high mobility, node sparseness, and lossy link. Thus, the broadcasting algorithms in the vehicular...     

An improved EAAP scheme for vehicular ad hoc networks

Recently, Maria Azees et al proposed an “EAAP: efficient anonymous authentication with conditional privacy‐preserving scheme for Vehicular Ad Hoc Networks.” Their scheme is mainly to solve the problem of high computation time of anonymous certificate and signature authentication, as well as the tracking problem of malicious vehicles. However, some improvements are needed in the protection of anonymous identity and the effective tracking of malicious vehicles. In this paper, our scheme realizes mutual authentication between OBU and RSU, and the RSU is authenticated without using certificate. In order to prevent the anonymous identity of the vehicles from being monitored and tracked, we use the negotiated short‐time key to encrypt the anonymous identity in the vehicle certificates. In addition, our scheme uses a new tracking method for malicious vehicles. Then, we prove the scheme through BAN logic, and it has the properties of authentication, anonymity, unlinkability, privacy protection, and traceability. Finally, we compare the computation cost and communication cost with other schemes, and the scheme has been greatly improved.     

An efficient location forwarding with shortcut scheme for position-based routing in mobile ad-hoc networks

Position-based routing protocols are considered as having better scalability and lower control overhead than topology-based routing protocols in mobile ad-hoc networks (MANETs). Since location services are the most critical part of position-based routing protocols, we present an Efficient Location Forwarding with Shortcuts (ELFS) scheme to improve the performance of location services. The ELFS scheme uses multiple virtual home regions to achieve efficient location discovery. We develop three approaches to reducing the overhead of maintaining multiple virtual home regions. The first approach, shortcut updates, uses the idea of shortcut to decrease the frequency of global updates. The second approach, adaptive broadcasting, alleviates the cost of each global update. In certain conditions, ELFS only broadcasts the messages of location update to the regions with the longest query paths. The third approach, packet forwarding with direction awareness, reduces the path lengths of messages. It can improve the cost of transmitting location information for delay-tolerant applications. With these approaches, the frequency of global broadcasting is decreased, and the overhead of location maintenance is reduced significantly. The simulation results show that the performance of ELFS is comparably fast and stable.     

Service-aware based fuzzy admission control scheme in multi-service networks

Multi-service aggregated transmission is the direction of IP network. Providing different Quality of Service (QoS) assurance for different services has become a crucial problem in future network. Admission control is a vital function for multi-service IP network. This paper proposes a novel fuzzy admission control scheme based on coarse granularity service-aware technique. Different service has discriminative sensitivity to the same QoS characteristic parameter in general. The traffic class can be perceived by the service request parameter and the proposed QoS function. And requirements of dif- ferent applications can be met by maintaining the life parameter. From simulation results, the proposed scheme shows a better QoS provisioning than those traditional fuzzy logic based methods under the same admission probability.     

基于EPON和WiMAX的三网融合方案的设计

三网融合是通信发展的必然趋势,由于国内不同地区所处的地理环境不同,在三网融合中所用到的技术也有所不同。EPON和WiMAX是目前比较成熟的两种宽带接入技术,它们有各自的优点,这两种技术相互结合则能满足不同场景下网络需求的建设,推动三网融合的快速发展。通过结合实际工程分析了不同场景下运用这两种技术建设通信网络的设计方案。