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.     

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.     

A cross-layer middleware for context-aware cooperative application on mobile ad hoc peer-to-peer network

Mobile ad hoc peer-to-peer (P2P) applications become popular for providing the file sharing, voice communicating, and video streaming services due to entertainments and disaster recovery. However, both the topology of wireless network and the overlay of P2P network are dynamic, so the middleware is proposed to integrate such architectures of service-oriented applications. Therefore, we propose context-aware cooperative application (CACA) to overcome the frequent churn and high mobility problems. CACA proposes a cross-layer middleware to integrate DHT-based lookup, anycast query, and P2P delivery via the IPv6 routing header. Through anycast query, the response delay can be shortened and the query duplication can be minimized. Via IPv6 routing header, the delivery efficiency can be improved. Through the cross-layer design, the finger table in overlay layer is combined with the routing table in network layer to heighten proximity. The simulation results demonstrate that CACA has the outstanding performances of short download delay, high playback continuity, and low signaling overhead in mobile ad hoc network.     

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.     

A link availability-based QoS-aware routing protocol for mobile ad hoc sensor networks

With more and more wireless devices being mobile, there is a constant challenge to provide reliable and high quality communication services among these devices. In this paper, we propose a link availability-based QoS-aware (LABQ) routing protocol for mobile ad hoc networks based on mobility prediction and link quality measurement, in addition to energy consumption estimate. The goal is to provide highly reliable and better communication links with energy-efficiency. The proposed routing algorithm has been verified by NS-2 simulations. The results have shown that LABQ outperforms existing algorithms by significantly reducing link breakages and thereby reducing the overheads in reconnection and retransmission. It also reduces the average end-to-end delay for data transfer and enhances the lifetime of nodes by making energy-efficient routing decisions.     

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.     

The message delay in mobile ad hoc networks

A stochastic model is introduced that accurately models the message delay in mobile ad hoc networks where nodes relay messages and the networks are sparsely populated. The model has only two input parameters: the number of nodes and the parameter of an exponential distribution which describes the time until two random mobiles come within communication range of one another. Closed-form expressions are obtained for the Laplace–Stieltjes transform of the message delay, defined as the time needed to transfer a message between a source and a destination. From this we derive both a closed-form expression and an asymptotic approximation (as a function of the number of nodes) of the expected message delay. As an additional result, the probability distribution function is obtained for the number of copies of the message at the time the message is delivered. These calculations are carried out for two protocols: the two-hop multicopy and the unrestricted multicopy protocols. It is shown that despite its simplicity, the model accurately predicts the message delay for both relay strategies for a number of mobility models (the random waypoint, random direction and the random walker mobility models).     

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.     

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.     

Improved group-based cooperative caching scheme for mobile ad hoc networks

Data caching is a popular technique that improves data accessibility in wired or wireless networks. However, in mobile ad hoc networks, improvement in access latency and cache hit ratio may diminish because of the mobility and limited cache space of mobile hosts (MHs). In this paper, an improved cooperative caching scheme called group-based cooperative caching (GCC) is proposed to generalize and enhance the performance of most group-based caching schemes. GCC allows MHs and their neighbors to form a group, and exchange a bitmap data directory periodically used for proposed algorithms, such as the process of data discovery, and cache placement and replacement. The goal is to reduce the access latency of data requests and efficiently use available caching space among MH groups. Two optimization techniques are also developed for GCC to reduce computation and communication overheads. The first technique compresses the directories using an aggregate bitmap. The second employs multi-point relays to develop a forwarding node selection scheme to reduce the number of broadcast messages inside the group. Our simulation results show that the optimized GCC yields better results than existing cooperative caching schemes in terms of cache hit ratio, access latency, and average hop count.     

基于收方参与的移动自组网TCP增强的路由协议

移动自组网多跳、动态拓扑的特性,使得路由信息易老化,源节点在路由失败后不能及时启动路由发现,造成TCP有效吞吐率随移动速度增加而下降。在DSR路由协议的基础上,提出一种新的基于接收方参与启动路由发现的新路由协议RP DSR,它通过接收方的ACK确认包启动路由发现,主动为发送方提供最新的路由信息,从而提高了自组网的TCP的性能。仿真结果表明,在节点快速移动环境中,RP DSR协议的TCP性能明显优于DSR协议。     

Scalability of routing methods in ad hoc networks

In an ad hoc network each host (node) participates in routing packets. Ad hoc networks based on 802.11 WLAN technology have been the focus of several prior studies. These investigations were mainly based on simulations of scenarios involving up to 100 nodes (usually 50 nodes) and relaxed (too unrealistic) data traffic conditions. Many routing protocols in such setting offer the same performance, and many potential problems stay undetected. At the same time, an ad hoc network may not want (or be able) to limit the number of hosts involved in the network. As more nodes join an ad hoc network or the data traffic grows, the potential for collisions and contention increases, and protocols face the challenging task to route data packets without creating high administrative load. The investigation of protocol behavior in large scenarios exposes many hidden problems. The understanding of these problems helps not only in improving protocol scalability to large scenarios but also in increasing the throughput and other QoS metrics in small ones. This paper studies on the example of AODV and DSR protocols the influence of the network size (up to 550 nodes), nodes mobility, nodes density, suggested data traffic on protocols performance. In this paper we identify and analyze the reasons for poor absolute performance that both protocols demonstrate in the majority of studied scenarios. We also propose and evaluate restructured protocol stack that helps to improve the performance and scalability of any routing protocol in wireless ad hoc networks.     

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.     

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.     

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.     

Learning-TCP: A stochastic approach for efficient update in TCP congestion window in ad hoc wireless networks

In this work, we attempt to improve the performance of TCP over ad hoc wireless networks (AWNs) by using a learning technique from the theory of learning automata. It is well-known that the use of TCP in its present form, for reliable transport over AWNs leads to unnecessary packet losses, thus limiting the achievable throughput. This is mainly due to the aggressive, reactive, and deterministic nature in updating its congestion window. As the AWNs are highly bandwidth constrained, the behavior of TCP leads to high contentions among the packets of the flow, thus causing a high amount of packet loss. This further leads to high power consumption at mobile nodes as the lost packets are recovered via several retransmissions at both TCP and MAC layers. Hence, our proposal, here after called as Learning-TCP, focuses on updating the congestion window in an efficient manner (conservative, proactive, and finer and flexible update in the congestion window) in order to reduce the contentions and congestion, thus improving the performance of TCP in AWNs. The key advantage of Learning-TCP is that, without relying on any network feedback such as explicit congestion and link-failure notifications, it adapts to the changing network conditions and appropriately updates the congestion window by observing the inter-arrival times of TCP acknowledgments. We implemented Learning-TCP in ns-2.28 and Linux kernel 2.6 as well, and evaluated its performance for a wide range of network conditions. In all the studies, we observed that Learning-TCP outperforms TCP-Newreno by showing significant improvement in the goodput and reduction in the packet loss while maintaining higher fairness to the competing flows.     

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.     

TCP-aware network coding with opportunistic scheduling in wireless mobile ad hoc networks

This paper presents a scheme that employs TCP-aware network coding with opportunistic scheduling to enhance TCP throughput in wireless mobile ad hoc networks. Specifically, it considers a TCP parameter, congestion window size, and wireless channel conditions simultaneously to improve TCP throughput performance. Evaluation of this scheme is carried out by using ns2 simulations in different scenarios. The results show that the proposed scheme gives approximately 35% throughput improvement in a high mobility environment and about 33% throughput increase in no or low mobility environment as compared to traditional network coding with opportunistic scheduling. This paper also proposes a new adaptive-W (i.e., adaptive Waiting time) scheme whose objective is to adaptively control waiting time of overheard packets that are stored in a buffer to achieve tradeoff between throughput and overhead.     

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.     

一种新的多路径自组网路由算法

传统的单路径路由使自组网路由性能一直不能获得太大的突破。因此,设计有效的和稳定的多路径路由成为最受关注的问题。为此提出了一种新的多路径路由算法,其在路由发现阶段使用了一种新的多路径转发策略。在基于稳定性因子的基础上,该算法计算路径间海明距离并据此选择多条相似的稳定不相交多路由,从而进一步提高该路由算法的性能。模拟结果显示,与经典的多路径路由相比较,该算法是一个有效的多路径自组网路由算法。