A cross-layer multi-hop cooperative network architecture for wireless ad hoc networks

In this paper, a novel decentralized cross-layer multi-hop cooperative network architecture is proposed and presented. This cross-layer architecture introduces a new cooperative flooding scheme and two decentralized opportunistic cooperative forwarding mechanisms based on randomized coding, and a Routing Enabled Cooperative Medium Access Control (RECOMAC) protocol that enables cooperative forwarding, while incorporating physical, medium access control (MAC) and routing layers. RECOMAC employs randomized coding to realize cooperative diversity, so that relay selection and actuation mechanisms are alleviated and the MAC costs are reduced. The coded packets are routed in the network via the proposed cooperative forwarding schemes, which opportunistically form cooperative sets within a region, not needing a prior route to be established. Essentially, in the RECOMAC architecture, the routing layer functionality is submerged into the MAC layer to provide seamless cooperative communication, while the messaging overhead to set up routes, select and actuate relays is reduced. We evaluate the performance of RECOMAC in terms of network throughput, delay and MAC and routing overhead, in comparison to the conventional architecture based on the well-known IEEE 802.11 MAC and Ad hoc On Demand Distance Vector (AODV) routing protocols. RECOMAC is shown to provide quite significant improvement by an order of magnitude difference in all investigated performance metrics, under a variety of scenarios, considering different network sizes, static and mobile scenarios and networks with multiple flows.     

Cost-effective mobile ad hoc networks management

As there are more and more mobile devices in use, different mobile networking models such as ad hoc or mesh are attracting a large research interest. Self-organizing mobile ad hoc networks (MANET) allow devices to share their services and resources without any central administration or Internet support. In this respect they can become the backbone of the wireless grid or the gateway to existing grids. To achieve these goals, MANET management must be as effective as that of wired networks. This is, however, a challenging task due to network features like mobility, heterogeneity, limited resources of hosts and feeble communication. This paper presents a set of simple, cost-effective and resilient procedures for the basic tasks of MANET creation and management.     

Triangle-based routing for mobile ad hoc networks

Routing protocols for Mobile ad hoc networks (MANETs) have been studied extensively in the past decade. Routing protocols for MANETs can be broadly classified as reactive (on-demand), proactive, hybrid and position-based. Reactive routing protocols are attractive because a route between a source and a destination is established only when it is needed. Such protocols, unlike proactive protocols, do not have high overhead for route maintenance and are especially suitable for networks in which not all nodes communicate frequently. One problem with existing reactive routing protocols is the propagation of redundant route request messages during route discovery. In this paper, we present a low-overhead reactive routing protocol which reduces propagation of redundant route request messages. We also compare its performance with the well-known reactive routing protocol AODV.     

An evolutionary computation approach for designing mobile ad hoc networks

This paper presents the topological design of ad hoc networks in terms of distances among static nodes and speeds of mobiles nodes. Due to the complexity of the problem and the number of parameters to be considered, a genetic algorithm combined with the simulation environment NS-2 is proposed to find the optimum solution. More specifically, NS-2 provides the fitness function guiding the genetic search. The proposed framework has been tested using a railway scenario in which several static and mobile nodes are interacting. Results show the feasibility of the proposed framework and illustrate the possibility of genetic approach for solving similar application scenarios.     

A clique-based secure admission control scheme for mobile ad hoc networks (MANETs)

Wireless mobile ad hoc networks (MANETs) do not have centralized infrastructure and it is difficult to provide authentication services. In this paper, we apply Certificate Graph (CG) and identity-based security in designing an admission control scheme for MANETs. We first use one-hop message exchange to build CG at each mobile node. Then we select maximum clique nodes in CG as distributed Certificate Authorities (CAs). We use identity-based key agreement from pairings to protect each session. Then we prove the security by Canetti–Krawczyk (CK) model-based analysis. We demonstrate the effectiveness and feasibility of our protocol through computer simulations.     

Location aware, dependable multicast for mobile ad hoc networks

This paper introduces dynamic source multicast (DSM), a new protocol for multi-hop wireless (i.e., ad hoc) networks for the multicast of a data packet from a source node to a group of mobile nodes in the network. The protocol assumes that, through the use of positioning system devices, each node knows its own geographic location and the current (global) time, and it is able to efficiently spread these measures to all other nodes. When a packet is to be multicast, the source node first locally computes a snapshot of the complete network topology from the collected node measures. A Steiner (i.e., multicast) tree for the addressed multicast group is then computed locally based on the snapshot, rather than maintained in a distributed manner. The resulting Steiner tree is then optimally encoded by using its unique Pr

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u" height="11" width="9">fer sequence and is included in the packet header as in, and extending the length of the header by no more than, the header of packets in source routing (unicast) techniques. We show that all the local computations are executed in polynomial time. More specifically, the time complexity of the local operation of finding a Steiner tree, and the encoding/decoding procedures of the related Prüfer sequence, is proven to be O(n²), where n is the number of nodes in the network. The protocol has been simulated in ad hoc networks with 30 and 60 nodes and with different multicast group sizes. We show that DSM delivers packets to all the nodes in a destination group in more than 90% of the cases. Furthermore, compared to flooding, DSM achieves improvements of up to 50% on multicast completion delay.     

A scalable publish/subscribe system for large mobile ad hoc networks

Since nodes that compose mobile ad hoc networks (MANETs) does not have any prior knowledge about other nodes in many cases, the publish/subscribe communication paradigm that has the decoupling and asynchrony properties can be useful to share information between nodes. Existing publish/subscribe services for MANETs can be categorized into document flooding (DF), destination-based routing (DBR), and content-based routing (CBR). Although those approaches may work well when the size of network is small, all of them suffer from the performance decline as the size of the network increases. In this paper, we compare those approaches, and then propose a scalable publish/subscribe communication scheme in large MANETs by combining DF and CBR hierarchically. Our approach is to cluster all nodes in networks and to exploit CBR and DF for the intra- and inter-cluster communication, respectively. By using this approach, we can effectively utilize benefits of both approaches. Then, we present performance evaluation results which validate our idea with respect to system performance and scalability.     

Improving routing distance for geographic multicast with Fermat points in mobile ad hoc networks

In mobile ad hoc networks (MANETs), each node has the ability to transmit, receive, and route packets, and also moves through the field either randomly or in accordance with a pre-planned route. For enhancing the performance of MANETs, reducing the routing distance is a primary concern. For either ad hoc or static networks, the problem of minimizing the overall routing distance during multicasting is NP-complete. Therefore, it is difficult to determine an optimal solution. This paper presents an efficient geographic multicast protocol, designated as GMFP, based on the use of Fermat points. The objective of GMFP is to improve the overall routing distance for multicast tasks. Through a series of simulations, it is shown that GMFP outperforms the conventional Position-Based Multicast protocol and FERMA protocol in terms of the total routing distance, the packet transmission delay, the packet delivery ratio, and the node energy consumption. The performance improvements provided by GMFP are apparent as the scale of the network topology increases.     

Contention-aware data caching in wireless multi-hop ad hoc networks

This paper studies a challenging problem of cache placement in wireless multi-hop ad hoc networks. More specifically, we study how to achieve an optimal tradeoff between total access delay and caching overheads, by properly selecting a subset of wireless nodes as cache nodes when the network topology changes. We assume a data source updates a data item to be accessed by other client nodes. Most of the existing cache placement algorithms use hop counts to measure the total cost of a caching system, but hop delay in wireless networks varies much due to the contentions among these nodes and the traffic load on each link. Therefore, we evaluate the per-hop delay for each link according to the contentions detected by a wireless node from the MAC layer. We propose two heuristic cache placement algorithms, named Centralized Contention-aware Caching Algorithm (CCCA) and Distributed Contention-aware Caching Algorithm (DCCA), both of which detect the variation of contentions and the change of the traffic flows, in order to evaluate the benefit of selecting a node as a cache node. We also apply a TTL-based cache consistency strategy to maintain the delta consistency among all the cache nodes. Simulation results show that the proposed algorithms achieve better performance than other alternative ones in terms of average query delay, caching overheads, and query success ratio.     

MobiCache: Cellular traffic offloading leveraging cooperative caching in mobile social networks

Offloading cellular traffic through mobile social networks has arisen as a promising way for relieving cellular networks. Prior studies mainly focused on caching data in a number of pre-selected helpers. However, such a strategy would fail when mobile users enter and leave the target area over time. In this paper, we examine the research decisions and design tradeoffs that arise when offloading cellular traffic in such a dynamic area of interest, referred to as a MobiArea, and we design an offloading framework, MobiCache, for maximizing cellular operators’ revenues and minimizing the overhead imposed on mobile devices. On the user side, we propose a content floating-based cooperative caching strategy that caches data in geographical floating circles, instead of selected helpers in previous studies, to cope with the dynamics. A geographical routing scheme is designed for delivering data and queries towards floating circles. We also develop a cache replacement scheme to improve caching cost-effectiveness inside floating circles. On the operator side, query history and feedback are maintained for cellular operators to optimize framework parameters that maximize their revenues. Extensive trace-driven simulations show that, compared with a state-of-the-art scheme, MobiCache offloads up to 52% more traffic with 15% shorter delay and 6% less forwarding cost.     

Privacy addressing and autoconfiguration for mobile ad hoc networks

Allowing truly spontaneous and infrastructureless networking, mobile ad hoc networks (MANETs) are the future of wireless networks. However, most autoconfiguration proposals for MANETs lack privacy support, namely anonymity or pseudonymity and unlinkability aspects, which has become important considerations in many practical applications. This paper presents a novel privacy extension approach (PEA) for MANETs, which prevents eavesdroppers from identifying a particular mobile node by its address. In addition to privacy concerns, our scheme also brings some performance benefits, e.g., reducing the possibility of address conflict when the merging of separately configured networks occurs.     

Dynamic backup routes routing protocol for mobile ad hoc networks

Mobile Ad Hoc Networks (MANETs), which provide data networking without infrastructure, represent one kind of wireless networks. A MANET is a self-organizating and adaptive wireless network formed by the dynamic gathering of mobile nodes. Due to the mobility of mobile nodes, the topology of a MANET frequently changes and thus results in the disability of originally on-the-fly data transmission routes. The dynamic properties of MANETs are therefore challenging to protocol design. To cope with the intrinsic properties of MANETs, Dynamic Backup Routes Routing Protocol (DBR²P), a backup node mechanism for quick reconnection during link failures, is proposed in this paper. DBR²P is an on-demand routing protocol and it can set up many routes to reach a destination node in a given period. Even when a link fails, those routes from the source node to the destination node can be analyzed to obtain backup routes to sustain quick reconnection. The information of backup routes can be saved in a specific on-the-route node and enables backup routes to be found immediately in situation regarding disconnection. As a result, DBR²P could more thoroughly improve the quality of routing protocol than those proposed in the past.     

End-to-end support for statistical quality of service in heterogeneous mobile ad hoc networks

In heterogeneous mobile ad hoc networks (MANETs), different types of mobile devices with diverse capabilities may coexist in the same network. The heterogeneity of MANETs makes end-to-end support for quality of service (QoS) guarantees more difficult than in other types of networks, not to mention the limited bandwidth and frequent topology changes of these networks. Since QoS routing is the first step toward achieving end-to-end QoS guarantees in heterogeneous MANETs, we propose a QoS routing protocol for heterogeneous MANETs. The proposed protocol, called virtual grid architecture protocol (VGAP), uses a cross-layer approach in order to provide end-to-end statistical QoS guarantees. VGAP operates on a fixed virtual rectilinear architecture (virtual grid), which is obtained using location information obtained from global positioning system (GPS). The virtual grid consists of a few, but possibly more powerful, mobile nodes known as ClusterHeads (CHs) that are elected periodically. CHs discover multiple QoS routes on the virtual grid using an extended version of the open shortest path first (OSPF) routing protocol and an extended version of WFQ scheduling policy that takes into account the wireless channel state. Moreover, VGAP utilizes a simple power control algorithm at the physical layer that provides efficient energy savings in this heterogeneous setting. Simulation experiments show that VGAP has a good performance in terms of packet delivery ratio, end-to-end packet delay, call blocking probability, and network scalability.     

A stable weight-based on-demand routing protocol for mobile ad hoc networks

A mobile ad hoc network (MANET) consists of a set of mobile hosts that can communicate with each other without the assistance of base stations. In MANETs, the high mobility of mobile nodes is a major reason for link failures. In this paper, we propose a stable weight-based on-demand routing protocol (SWORP) for MANETs. The proposed scheme uses the weight-based route strategy to select a stable route in order to enhance system performance. The weight of a route is decided by three factors: the route expiration time, the error count, and the hop count. Route discovery usually first finds multiple routes from the source node to the destination node. Then the path with the largest weight value for routing is selected. Simulation results show that the proposed SWORP outperforms DSR, AODV, and AODV-RFC, especially in a high mobility environment.     

Certification-based trust models in mobile ad hoc networks: A survey and taxonomy

A mobile ad hoc network is a wireless communication network which does not rely on a pre-existing infrastructure or any centralized management. Securing the exchanges in such network is compulsory to guarantee a widespread development of services for this kind of networks. The deployment of any security policy requires the definition of a trust model that defines who trusts who and how. There is a host of research efforts in trust models framework to securing mobile ad hoc networks. The majority of well-known approaches is based on public-key certificates, and gave birth to miscellaneous trust models ranging from centralized models to web-of-trust and distributed certificate authorities. In this paper, we survey and classify the existing trust models that are based on public-key certificates proposed for mobile ad hoc networks, and then we discuss and compare them with respect to some relevant criteria. Also, we have developed analysis and comparison among trust models using stochastic Petri nets in order to measure the performance of each one with what relates to the certification service availability.     

Adaptive TCP congestion control and routing schemes using cross-layer information for mobile ad hoc networks

Compared with traditional networks, ad hoc networks possess many unique characteristics. For example, ad hoc networks can drop a packet due to network events other than buffer overflow. Unfortunately, the current layered network architecture makes it impossible to pass the information specific to one layer to other layers. As a result, if a packet is lost due to reasons other than buffer overflow, TCP adversely invokes its congestion control procedure. Similarly, the routing algorithm may misinterpret that a path is broken and adversely invoke the route recovery procedure.This study addresses the limitations of the current layered network architecture by adopting a cross-layer protocol design for TCP and routing algorithms in ad hoc networks. The objective of this approach is to enable the lower-layered ad hoc network to detect and differentiate all possible network events, including disconnections, channel errors, buffer overflow, and link-layer contention, that may cause packet loss. Using the information exploited by lower layers, the upper layer-3 routing algorithm, and the layer-4 TCP can take various actions according to the types of network events. Simulation results demonstrate that the combination of the cross-layer optimized TCP and routing algorithms can effectively improve the performance of TCP and DSR, regardless of whether it is in a stationary or a mobile ad hoc network.     

Efficient implementations of all-to-all broadcasting in mobile ad hoc networks

In order to ease the challenging task of information dissemination in a MANET, we employ a legend: a data structure passed around a network to share information with all the mobile nodes. Our motivating application of the legend is sharing location information. Previous research shows that a simplistic legend performs better than other location services in the literature. To realize the full potential of legend-based location services, we propose three methods for the legend to traverse a network and compare their performance in simulation. Two of our proposed methods are novel, and the third is an improvement on an existing method. We also evaluate several general improvements to the traversal methods, and describe our way of making the legend transmission reliable. The result is a simple, lightweight location service that makes efficient use of network resources. Beyond using the legend as a location service, we discuss several implementation aspects of providing an efficient all-to-all broadcast operation, including legend reliability, preventing duplicate legends, using a legend in dynamic networks, and working with non-synchronized clocks. We also provide pseudocode for our legend traversal methods to aid implementation.     

A distributed fault identification protocol for wireless and mobile ad hoc networks

This paper considers the problem of self-diagnosis of wireless and mobile ad hoc networks (MANETs) using the comparison approach. In this approach, a network (MANET) consists of a collection of n   independent heterogeneous mobile or stationary hosts interconnected via wireless links, and it is assumed that at most σ$\sigma$ of these hosts are faulty. In order to diagnose the state of the MANET, tasks are assigned to pairs of hosts and the outcomes of these tasks are compared. The agreements and disagreements between the hosts are the basis for identifying the faulty ones. The comparison approach is believed to be one of the most practical fault identification approaches for diagnosing hard and soft faults. We develop a new distributed self-diagnosis protocol, called Dynamic-DSDP, for MANETs that identifies both hard and soft faults in a finite amount of time. The protocol is constructed on top of a reliable multi-hop architecture. Correctness and complexity proofs are provided and they show that our Dynamic-DSDP performs better, from a communication complexity viewpoint, than the existing protocols. We have also developed a simulator, that is scalable to a large number of nodes. Using the simulator, we carried out a simulation study to analyze the effectiveness of the self-diagnosis protocol and its performance with regards to the number of faulty hosts. The simulation results show that the proposed approach is an attractive and viable alternative or addition to present fault diagnosis techniques in MANET environments.     

移动自组网的动态编址问题

作为实现移动自组网自动配置的一个关键问题,综述了节点地址的自动配置的最新进展,描述了设计移动自组网动态地址配置协议所面临的问题,对该问题研究开展以来所提出的各种主要方法和协议进行了详细对比、分析和分类阐述,为进一步的研究提出了新的建议。     

ad hoc网络具有撤销机制的密钥管理方案

分析了现有ad hoc网络基于身份的密钥管理方案,针对用户密钥泄漏,异常等情况,提出了一种具有密钥撤销机制的密钥管理方案,并在此基础上给出了用户签名方案。在文本中,用户可以通过注销泄漏密钥,防止攻击者用窃取的密钥伪造用户签名,即使攻击者成功伪造了用户签名,用户还可以通过系统签名注销消息来证明伪造的签名无效。方案在门限密码学的基础上以完全分布化方式建立系统密钥,具有良好的容错性,能抵御网络的主动和被动攻击。和以往的方案相比具有更高的安全性。