基于广播树的移动自组织网络合作路由协议

为了激励自组网中的自私节点使其参与网络合作,提出了一种基于VCG机制计算转发节点支付的BEC协议,此协议对LDTTO协议的支付方案进行了改进,使源节点失去作弊动机.在路由发现阶段,创建以目的节点为根的广播树,将节点拓扑信息沿广播树以单播方式发送到根节点,降低了网络控制负载开销和路由发现延迟.BEC协议引入了容错机制,通过在混杂模式下对父节点的监听来确保数据的正确传输.在BEC协议中,高度为O(lgn)的广播树,路由发现过程的消息负载为O(nlogn),低于LOTID协议的O(n2).仿真实验结果表明,与现有的几种重要协议相比,BEC协议具有更低的消息负载和网络延迟.     

GPS-free mobility metrics for mobile ad hoc networks

Efficient mobility metrics are necessary for mobile ad hoc networks to measure the impact of node mobility on performance. Normally, measuring mobility requires the use of complex localisation systems. A new mobility metric for performance measurements, the intra-vicinity dependency, is proposed. Its main novelty is that it can fully capture the relative motions between a node and its vicinity in a 2D plane, in real-time, using simple triangulation. Variants of this metric are proposed for predicting the performance of networks that follow group and random mobility models (e.g. inter-group inter-meeting times and packet delivery rate). To make the proposed mobility metrics more robust in noisy environments, a calibration method is also proposed for improving accuracy. Experimental results show that, without the help of any localisation systems, the proposed metrics enable a more accurate approximation of the average relative speed between mobile nodes/groups than existing methods. It is also shown that the proposed metrics yield excellent performance when they are used to predict the inter-group inter-meeting times for networks that follow the Rereence point group mobility model and to estimate the packet delivery rate for those that follow the Random Way Point model.     

Multi-channel medium access control protocol with channel distribution for mobile ad hoc networks

This study proposes a novel multi-channel medium access control protocol for mobile ad hoc networks that enables nodes to transmit packets in distributed channels. In our protocol, the ad hoc traffic indication message window is divided into two windows. The first window is called the deciding channel window (DCW). Source and destination nodes can negotiate with each other in deciding a channel that can be used to compete for the final data channel in the DCW. The second window is called the exchanging packet window (EPW). Pair source and destination nodes can compete to obtain a channel to transfer packets in the EPW. This mechanism can distribute pair source and destination nodes to compete for a data channel. Hence, because of this, collisions can be avoided greatly and throughput can be increased. The simulation results show that our protocol successfully exploits the use of the bandwidth of multiple channels effectively.     

Time-stepped approach for accelerated simulation of mobile ad hoc networks

Model abstraction techniques have been widely used to accelerate simulations in the context of homogeneous wired networks. However, the application of these techniques to wireless networks is rare. The authors investigate how model abstraction techniques can be applied to simulations of mobile ad hoc networks (MANETS). The authors focus on the time-stepped (TS) simulation technique and its effect on simulation accuracy, analysing the simulation error introduced and providing a formal expression. This technique is implemented in a new simulator, session level simulator (SSIM), a TS session-level MANET simulator developed in the course of this research. The results of experiments conducted using SSIM show that the TS simulation can speedup MANET simulation and improve scalability by reducing the number of events and the simulation running time. Moreover, the study on simulation error illustrates that besides the length of the time step, parameters of mobility and traffic models also have great effect on simulation accuracy.     

一种Ad Hoc网络拓扑控制算法

分析了Ad Hoc网络的性能与拓扑结构的密切相关性和网络特点,提出了一种适用于Ad Hoc网络的基于计算几何方法和功率控制技术的分布式拓扑控制算法.该算法利用天线判断邻居节点方向,构建局部网络拓扑;采用计算几何法减少邻居数,简化拓扑结构;使用对称机制保障节点间的双向连通,兼顾网络连通性;通过调整功率实现具有健壮性的网络拓扑优化控制.仿真结果表明,该算法在满足网络覆盖度和连通性的前提下,形成了优化的拓扑结构,能够节约能量,延长节点寿命,减少相互干扰,提高信道利用率,降低传输时延,增加吞吐量,改善了网络整体性能.     

Flooding-limited for multi-constrained quality-of-service routing protocol in mobile ad hoc networks

Multi-constrained quality-of-service (QoS) routing is used to find routes in a network to satisfy multiple independent QoS constraints. This problem is considered to be NP-complete, and most existing QoS routing algorithms are based on maintaining a global network state at every node. A multi-constrained, flooding-limited, QoS routing method to deal with limited available resources and minimum computation in a dynamic environment is proposed. The solution is based on decomposition of a routing area and a restriction in the exchange of routing information. It reduces the size of the control messages, restricts the amount of routing information, minimises the overhead from the flooding of control traffic and decreases the complexity of path selection. It is also proved that the flooding-limited-path heuristic can achieve very high performance by maintaining entries in each node, which indicates that the performance of the limited-path heuristic is not sensitive to the number of constraints. Simulation results show that this protocol provides better performance than other protocols, especially with regards to end-to-end delay, throughput and packet loss.     

间断连通移动有组织网络中延时有界的概率路由策略

针对间断连通移动自组织网络(ICMAN)实际应用中对消息的送达率、发送延时及开销三项重要指标的要求,本文借助于发送延时的概率模型,分析了这三项指标的相互关系,进而提出了一种综合考虑这三种指标的延时有界的概率路由策略(BDPBR),其特点是重视精确的延时指标,而非现有算法关注的消息的平均传输延时,能以给定概率保证消息的端到端发送延时.仿真结果表明,该策略能够通过调整必需发送概率(RDP)和必需传输延时(RDD)来控制消息的实际发送率和发送延时,同时可根据RDP和RDD来调整系统开销,可按用户设定的送达率与延时指标以相应的代价发送消息,适应不同的服务要求.     

支持动态带宽约束的Ad Hoc网络QoS路由协议

针对已有的Ad Hoc网络QoS路由协议不能有效支持具有动态资源需求的特性业务的问题,提出了一种路径上传输带宽可动态调整的带宽约束QoS路由协议.路由建立后,若路径上的需求带宽增加,该协议将启动升级进程,各带宽瓶颈节点根据该协议的动态前向算法求解释放时隙集合,通过释放这部分当前处于传输状态的时隙增加路径上的预留带宽:而...     

移动自组网选播路由协议ARAD

针对移动自组(ad hoc)网的特点,提出了一种适合ad hoc移动网络的选播路由协议——ARAD协议.该协议在充分考虑选播路由特点的基础上,将ad hoc按需距离矢量路由(AODV)协议的路由发现机制与动态源路由(DSR)协议的缓存源路由技术相结合,在动态变化的ad hoc网络中实现了一种高效的选播路由.模拟结果表明,在动态的网络环境下,ARAD协议能够取得良好的性能.     

Trust-based hexagonal clustering for efficient certificate management scheme in mobile ad hoc networks

The wireless and dynamic nature of mobile ad hoc networks (MANET) render them more vulnerable to security attacks. However, providing a security mechanism implicitly has been a major challenge in such an ad-hoc environment. Certificate management plays an important role in securing an ad-hoc network. Certificate assignment, verification, and revocation complexity associated with the Public Key Infrastructure (PKI) framework is significantly large. Smaller the size of the network lesser will be the certificate management complexity. However, smaller the size, large will be the overall infrastructural cost, and also larger will be the overall redundant certificates due to multiple certificate assignment at the boundary regions, that in turn affects the prompt and accurate certificate revocation. By taking these conflicting requirements into consideration, we propose the trust-based hexagonal clustering for an efficient certificate management (THCM) scheme, to bear an absolutely protected MANET Disparate to the existing clustering techniques, we present a hexagonal geographic clustering model with Voronoi technique where trust is accomplished. In particular, to compete against attackers, we initiate a certificate management strategy in which certificate assignment, verification, and revocation are carried out efficiently. The performance of THCM is evaluated by both simulation and empirical analysis in terms of effectiveness of revocation scheme (with respect to revocation rate and time), security, and communication cost. Besides, we conduct a mathematical analysis of measuring the parameters obtained from the two platforms in multiple times. Relevant results demonstrate that our design is efficient to guarantee a secured mobile ad hoc network.     

Mobile IP handoffs among multiple internet gateways in mobile ad hoc networks

In a mobile ad hoc network (MANET) with multiple Internet gateways, efficient management of mobile IP functionality supporting seamless data services is a major challenge. The inadequacy of existing mobile IP schemes applicable to MANETs motivated the search for more efficient gateway discovery/handoff schemes. A solution for mobile IP-based gateway discovery/handoff in dynamic source routing (DSR)-based MANET is formulated. Enhanced mobile IP protocol suitable for MANET environment, i.e. the mobile IP registration controller, is designed. In particular, one of the most significant contributions deals with the mobile IP handoff triggering mechanism which is adaptively assisted by the DSR route maintenance mechanism. Simulation results are provided to support the idea.     

Context sensitive trust based geographic opportunistic routing in mobile ad hoc networks

Sādhanā - Position based opportunistic routing (POR) is a stateless, robust, and reliable geographic routing protocol in Mobile AdHoc NETwork (MANET). The opportunistic routing embraces...     

基于多路径路由的自组网节点合作方法

为减小移动自组网中自私节点对网络性能的影响,提出了一种基于TORA协议的自组网节点合作方法TORA_CE。由于每个节点拥有多条通往目的节点的路径,在发现自私节点后,该方法能够快速切换路由,从而减小了数据传输过程中丢包的概率。TORA_CE具有更好的分布式特点,将自私节点引发的路由变化限制在自私节点附近较小的范围内,而且引入了共同邻居监听技术,并采用一跳信息计算节点的信誉值,提高了对自私节点的检测速度。使用NS2对TORA_CE进行了仿真,实验结果显示,与基于DSR协议的节点合作方法相比,TORA_CE能够明显提高网络的吞吐率。     

Cross-layer design for block subchannel allocation and admission control in the IEEE 802.16 OFDMA networks

The flexibility of orthogonal frequency-division multiple access (OFDMA) technology necessitates a compromise between spectrum efficiency and quality of service (QoS) in IEEE 802.16 broadband wireless networks. This article proposes a complete solution with the nice feature of adaptive modulation and a coding scheme to provide both delay and loss rate guarantees for real-time services. The proposed method first determines the subframe boundary according to the current downlink and uplink backlogs. To comply with the IEEE 802.16 standard, the proposed method then groups contiguous subchannels and allocates them to proper connections based on the current loss rate and available modulation and coding schemes for each connection. By modeling the aggregated required subchannels as a Gaussian distribution, this study develops a simple admission control algorithm by checking if there are enough resources for a new connection. Simulation results show that the proposed solution can provide QoS guarantee with high spectrum efficiency.     

Inter-vehicle mobile ad hoc network for road transport systems

Access to information services while on the move is becoming increasingly prevalent within transport systems. Whereas Internet access is now common place in trains, it still remains a challenge for vehicles, particularly when travelling through high speed motorways. Motorway vehicles equipped with wireless communication nodes form an ad hoc network have been examined by which data can be exchanged among them without the need for a pre-installed infrastructure. The main challenge with such an infrastructure-less network is developing communications and protocols that can deliver robust and reliable ad hoc communications between vehicles, when the relative speed between vehicles that can be extremely high under opposite traffic conditions. To address this opposite direction effect, a solution has been presented by minimising the effect of opposite traffic on routing packets. Firstly, a router direction index is introduced to enhance the performance of ad hoc on demand distance vector protocol in updating its routing table and secondly, a new queue priority mechanism is proposed which is based on cross-layer collaboration. Simulations were performed for an ad hoc network consisting of 200 vehicles driving with speeds between 90 and 120 km/h on a two-way motorway for different traffic loads sent through a Gateway adjacent to the motorway. The results obtained demonstrate a performance increase in the average data goodput and less routing overhead for the proposed solution     

On physical layer-oriented routing with power control in ad hoc wireless networks

Routing in ad hoc wireless networks does not simply consist in finding a route with shortest length (as in wired networks with virtually error-free communication links), but it requires the creation of a stable and good quality communication route to avoid any unnecessary packet loss. In this paper,we discuss physical layer-oriented routing in ad hoc wireless networks, and we analyse the potential advantages of combining the use of power control (PC) with the chosen routing strategy. More precisely, we propose a modified ad hoc on-demand distance vector (MAODV) routing protocol, with and without PC, derived from the AODV-routing protocol by considering the bit error rate at the end of a multi-hop path as the metric to be minimised for route selection. In other words, we consider routing with a physical layer-oriented quality of service criterion, and we analyse the system performance in scenarios with either strong line-of-sight (LOS) or shadowed communications. Although in a scenario with strong LOS communications there are a few cases where the MAODV-PC protocol offers the best performance, in the presence of shadowed communications the proposed physical layer-oriented strategy is not attractive.     

基于链路动态特征的自组网路由选择方法

针对在动态的移动ad hoc网络环境中失效路由的频繁重建和维护操作造成大量控制负载开销以及能量消耗的问题,提出了一种基于无线逻辑链路信息熵度量的路由稳定性计算方法.此算法通过网络运行过程中无线链路状态变化所表现出的不确定性特征来刻画网络节点的稳定程度,并在路由建立过程中选择相对稳定的无线移动节点作为数据传输的参与节点....     

Two-terminal reliability analyses for a mobile ad hoc wireless network

Reliability is one of the most important performance measures for emerging technologies. For these systems, shortcomings are often overlooked in early releases as the cutting edge technology overshadows a fragile design. Currently, the proliferation of the mobile ad hoc wireless networks (MAWN) is moving from cutting edge to commodity and thus, reliable performance will be expected. Generally, ad hoc networking is applied for the flexibility and mobility it provides. As a result, military and first responders employ this network scheme and the reliability of the network becomes paramount. To ensure reliability is achieved, one must first be able to analyze and calculate the reliability of the MAWN. This work describes the unique attributes of the MAWN and how the classical analysis of network reliability, where the network configuration is known a priori, can be adjusted to model and analyze this type of network. The methods developed acknowledge the dynamic and scalable nature of the MAWN along with its absence of infrastructure. Thus, the methods rely on a modeling approach that considers the probabilistic formation of different network configurations in a MAWN. Hence, this paper proposes reliability analysis methods that consider the effect of node mobility and the continuous changes in the network's connectivity.     

Fair power control for wireless ad hoc networks using game theory with pricing scheme

Resource allocation in wireless ad hoc networks is usually modelled in a non-cooperative game theoretic framework with the objective of maximising individual utility. However, the selfishness of autonomous users under such framework may lead to throughput unfairness which only benefits certain users. To alleviate this unfairness problem, the authors propose a payment-based power control scheme using game theory where each user announces a set of price coefficients that reflects different compensations paid by other users for the interference they produce. Users who generate higher interference are required to pay more by transmitting at a lower power to give other users a fairer chance of sharing the throughput.Without any incentive to play fairly, users could misbehave by broadcasting high price coefficients to force other users to transmit at a lower power. The authors treat this problem casting it into a price game which resembles a Prisoner's Dilemma game. Users who play this game iteratively will behave cooperatively and broadcast the price coefficients truthfully. Together with analytical proof, the proposed approach is shown to converge to Nash equilibrium where at this point it is able to provide a fairer throughput share among users at the expense of a slight loss in total throughput.     

Wireless ad hoc networks [Editorial]

Wireless communication technologies are undergoing rapid advancements. The last few years have experienced a steep growth in research in the area of wireless ad hoc networks.