Quorum-Based Asynchronous Power-Saving Protocols for IEEE 802.11 Ad Hoc Networks

This paper investigates the power mode management problem for an IEEE 802.11-based mobile ad hoc network (MANET) that allows mobile hosts to tune to the power-saving (PS) mode. There are two major issues that need to be addressed in this problem: (a) wakeup prediction and (b) neighbor discovery. The former is to deliver buffered packets to a PS host at the right time when its radio is turned on. The latter is to monitor the environment change under a mobile environment. One costly, and not scalable, solution is to time-synchronize all hosts. Another possibility is to design asynchronous protocols as proposed by Tseng et al. in [25]. In this paper, we adopt the latter approach and correlate this problem to the quorum system concept. We identify a rotation closure property for quorum systems. It is shown that any quorum system that satisfies this property can be translated to an asynchronous power-saving protocol for MANETs. Thus, the result bridges the classical quorum system design problem in the area of distributed systems to the power mode management problem in the area of mobile ad hoc networks. We derive a lower bound for quorum sizes for any quorum system that satisfies the rotation closure property. We identify a group of quorum systems that are optimal or near optimal in terms of quorum sizes, which can be translated to efficient asynchronous power-saving protocols. We also propose a new e-torus quorum system, which can be translated to an adaptive protocol that allows designers to trade hosts' neighbor sensibility for power efficiency. Simulation experiments are conducted to evaluate and compare the proposed protocols.     

Ad Hoc网络路由技术

无线自组织网络(Adhoc)是一个复杂的系统,其中路由协议是该领域中的研究热点。通过采用合理的路由技术,可使无线自组网具有更为灵活的组网方式,从而达到提升网络性能、减少网络开销等目的。通过与认知无线电(CR)技术、协同通信(CC)技术以及多输入多输出(MIMO)天线技术等物理层新技术的有效结合,可以大大改善Adhoc路由协议的性能。     

TCP Performance in IEEE 802.11-Based Ad Hoc Networks with Multiple Wireless Lossy Links

We propose a packet-level model to investigate the impact of channel error on the transmission control protocol (TCP) performance over IEEE-802.11-based multihop wireless networks. A Markov renewal approach is used to analyze the behavior of TCP Reno and TCP Impatient NewReno. Compared to previous work, our main contributions are listed as follows: 1) modeling multiple lossy links, 2) investigating the interactions among TCP, Internet Protocol (IP), and media access control (MAC) protocol layers, specifically the impact of 802.11 MAC protocol and dynamic source routing (DSR) protocol on TCP throughput performance, 3) considering the spatial reuse property of the wireless channel, the model takes into account the different proportions between the interference range and transmission range, and 4) adopting more accurate and realistic analysis to the fast recovery process and showing the dependency of throughput and the risk of experiencing successive fast retransmits and timeouts on the packet error probability. The analytical results are validated against simulation results by using GloMoSim. The results show that the impact of the channel error is reduced significantly due to the packet retransmissions on a per-hop basis and a small bandwidth delay product of ad hoc networks. The TCP throughput always deteriorates less than ~ 10 percent, with a packet error rate ranging from 0 to 0.1. Our model also provides a theoretical basis for designing an optimum long retry limit for IEEE 802.11 in ad hoc networks.     

无线Ad Hoc网络中的QoS路由协议

无线Ad Hoc网络的应用环境以及与Internet的互连都要求其必须提供一定的服务质量(QoS)保证,QoS路由技术是在无线Ad Hoc网络中实现QoS的重要方法。本文对近年来国内外在无线Ad Hoc网络中的QoS路由技术方面取得的研究成果进行了全面的概括总结和分类,对资源预留路由、多径路由和跨层优化路由3类QoS路由协议进行比较分析,并且提出了QoS路由技术亟待解决的问题和今后的发展方向。     

即时无线移动网络及相关路由协议

即时无线网络需要设置固定的路由设备,网络中的每一个移动终端都可以充当路由器,即时无线网络的路由协议包括路由表驱动型路由协议和源节点发起型路由协议。本文分别以无线路由协议和即时指令型距离向量路由协议对上述两类协议进行了详细讨论。     

Throughput Analysis of IEEE802.11 Multi-Hop Ad Hoc Networks

In multi-hop ad hoc networks, stations may pump more traffic into the networks than can be supported, resulting in high packet-loss rate, re-routing instability and unfairness problems. This paper shows that controlling the offered load at the sources can eliminate these problems. To verify the simulation results, we set up a real 6-node multi-hop network. The experimental measurements confirm the existence of the optimal offered load. In addition, we provide an analysis to estimate the optimal offered load that maximizes the throughput of a multi-hop traffic flow. We believe this is a first paper in the literature to provide a quantitative analysis (as opposed to simulation) for the impact of hidden nodes and signal capture on sustainable throughput. The analysis is based on the observation that a large-scale 802.11 network with hidden nodes is a network in which the carrier-sensing capability breaks down partially. Its performance is therefore somewhere between that of a carrier-sensing network and that of an Aloha network. Indeed, our analytical closed-form solution has the appearance of the throughput equation of the Aloha network. Our approach allows one to identify whether the performance of an 802.11 network is hidden-node limited or spatial-reuse limited     

Bandwidth Estimation for IEEE 802.11-Based Ad Hoc Networks

Since 2005, IEEE 802.11-based networks are able to provide a certain level of Quality of Service by the means of service differentiation, thanks to the IEEE 802.11e amendment. However, no mechanism or method has been standardized to accurately evaluate the amount of resources remaining on a given channel. Such evaluation would however be a good asset for bandwidth-constrained applications. In multi-hop ad hoc networks, such evaluation becomes even more difficult. Consequently, despite the various contributions around this research topic, the estimation of the available bandwidth still represents one of the main issues in this field. In this article, we propose an improved mechanism to estimate the available bandwidth in IEEE 802.11-based ad hoc networks. Through simulations, we compare the accuracy of the estimation we propose to the estimation performed by others state of the art QoS protocols, BRuIT, AAC and QoS-AODV.     

Effectiveness of Reliable Routing Protocols in Mobile Ad Hoc Networks

Due to unpredictable topology change and frequent link failure, it becomes evident major challenge to provide the stable route between source and destination in mobile ad hoc networks. Unlike previous multipath routing schemes for redundancy and unicast routing protocol utilizing the longest route expiration time measured by geographical information supported by Global Positioning System (GPS), we develop a framework to establish the most stable route based on measured frequency of link failure, available battery as well as the number of actual connections. To evaluate performance of proposed scheme, we provide practical simulation results for multipath and unicast routing protocol in terms of packet delivery ratio, control overhead, average hop length as well as end-to-end delay. Through analysis of simulation results, we demonstrate that our scheme shows better performance than general unicast routing protocol as well as similar packet delivery ratio to multipath routing protocol with less maintenance overhead. Ki-Il Kim received the M.S. and Ph.D. degrees in computer science from the Chungnam National University, Daejeon, Korea, in 2002 and 2005, respectively. He is currently with Department of Information Science, Gyeongsang National University as a faculty member. His research interests include routing for MANET, QoS in wireless network, multicast, and sensor networks. Sang-Ha Kim received the B.S. degree in chemistry from Seoul National University, Seoul, Korea, in 1980. He received the M.S. and Ph.D. degrees in quantum scattering and computer science from the University of Houston, Houston, TX, in 1984 and 1989, respectively. From 1990 to 1991, he was with the Supercomputing Center, SERI, Korean Institute of Science and Technology (KIST) as Senior Researcher. He joined Chungnam National University, Daejeon, Korea, in 1992, where he is a Professor. His current research interests include wireless networks, ad hoc networks, QoS, optical networks, and network analysis.     

移动Ad Hoc网络中的QoS路由协议研究

移动Ad Hoc网络是一种无线多跳自治系统网络，如何提供QoS保障是它面临的重要问题，其中QoS路由是一个关键技术。文章首先介绍了AdHoc网络的特点，并且介绍了其QoS保障技术。接着对当前AdHoc网络主要的路由协议进行了详细的分析与研究，并从几个方面进行了比较和分析。最后指出了Ad Hoc网络QoS路由协议中需要解决的问题和今后的研究方向。     

A Minimum Interference Cross-Layer Routing Protocol for Mobile Ad Hoc Networks

In mobile ad hoc networks (MANETs), channel contention and packet collision can seriously affect the performance of routing protocols, which will eventually affect the performance of the whole network. Besides, the arbitrary mobility of nodes makes contention and collision ever-changing and more complex. Thus, it is imperative to analyze the problem of contention and collision so as to build appropriate routes in MANETs. In this paper, by respectively predicting the durations of the contention and collision at every hop along the route, a minimum interference cross-layer routing protocol (MI-CLR) is proposed based on Random Waypoint (RWP) model. The new protocol classifies the interference in the network into two types; the first type of interference can only affect channel contention, while the other affects both channel contention and packet collision. Via taking the two types of interference together into account, we propose a new routing metric to build routes which guarantees that the established routes will not break frequently while having the minimum interference. Simulation results show that the MI-CLR protocol can significantly improve the network performance such as the average end-to-end delay, the packet loss ratio, the routing overhead and the throughput.     

Survey of Secure Routing Protocols for Wireless Ad Hoc Networks

The mobile ad hoc network is a type of wireless network characterized by mobile nodes without a centralized administration. Frequent variations of the topology and the nature of the radio links have a negative impact on the stability of the links. Indeed, the link quality deteriorates rapidly and link breaks become frequent. To overcome these problems, new forms of routing protocols are used as the MultiPath routing. In addition, routing protocols require the knowledge of the nodes neighborhood to build and manage routes. The neighbor discovery process is performed by a Hello protocol. The Hello protocol typically involves several parameters such as the packet’s period; node’s transmit power, node’s position and node’s battery level. The purpose of this paper is to change the behavior of ad hoc On demand Multi-path Distance Vector (AOMDV) routing protocol by considering the density of the nodes as well as the interference of the neighboring nodes. This selection of paths goes through two stages. In the first step, we study the impact of the neighbor discovery process to select a set of paths having a minimum number of neighboring nodes to diminish contention problems and interference rate. In the second step, the Interference Ratio (IR) metric is used to select the paths in which the nodes are surrounded by a minimum of interference. We choose for our study two proposed approaches based on AOMDV routing protocol. The first is called AOMDV_neighbor and considers the density parameter as a path metric. The second is called AOMDV_neighbor_IR which considers the interference rate (IR) between each node and its neighborhood as a path metric. We evaluate the proposed routing protocols performance under various NS2 simulation scenarios in a shadowing environment.

     

基于能量有效的Ad hoc无线网络路由协议的研究

Ad hoc是一种无固定基础设施的特殊无线网络,此网络中节点一般由电池供能,需要考虑能量有效因素来最大化网络生命周期.对各类基于能量有效的Ad hoc无线网络路由协议进行比较和分析,可以看出路由协议对能量优化有着显著作用.     

Performance Evaluation of Routing Protocols for Ad Hoc Wireless Networks

A mobile ad hoc network is a collection of autonomous mobile nodes that communicate with each other over wireless links. Such networks are expected to play an increasingly important role in future civilian and military settings, being useful for providing communication support where no fixed infrastructure exists or the deployment of a fixed infrastructure is not economically profitable and movement of communicating parties is possible. However, since there is no stationary infrastructure such as base stations, mobile hosts need to operate as routers in order to maintain the information about the network connectivity. Therefore, a number of routing protocols have been proposed for ad hoc wireless networks. In this paper, we study and compare the performance of the following routing protocols AODV, PAODV (preemptive AODV), CBRP, DSR, and DSDV. A variety of workload and scenarios, as characterized by mobility, load and size of the ad hoc network were simulated. Our results indicate that despite its improvement in reducing route request packets, CBRP has a higher overhead than DSR because of its periodic hello messages while AODV's end-to-end packet delay is the shortest when compared to DSR and CBRP. PAODV has shown little improvements over AODV.     

无线Ad hoc网络中QOS路由协议的研究

QoS保证体系在Ad hoc网络中扮演着重要的角色.在引入Ad hoc网络中QoS保证体系的基本组件和面临的新挑战之后,对其中的QoS路由协议进行了讨论,按照先应式、反应式、基于群集、利用地理位置信息、组播、多径等类别,对近几年来的各种研究成果进行了阐述和分析,并对未来的发展趋势进行了展望.     

移动自组网QoS路由协议研究

移动自组网是由一组带有无线收发装置的移动节点组成的一个多跳的临时性的自治系统。随着无线通信中多媒体业务的增加,在移动自组网中提供QoS(Quality of Sevice服务质量)保障具有越来越重要的意义,而QoS路由技术则是其中的核心技术和热点问题。文章指出移动自组网QoS路由的困难,对移动自组网典型QoS路由协议进行了详细的分析与比较,并对几种较新的移动自组网QoS路由协议进行了介绍,末了对移动自组网QoS路由协议的发展进行了展望。     

多跳无线Ad hoc网络路由协议的模拟和性能比较

文中采用随机场景的模拟方法对3种多跳无线Ad hoc网络路由协议的性能做了定量性的分析.对网络模拟器NS-2做了更进一步的拓展:增加SASR路由协议、增加AODV的MAC层虚拟HELLO机制,在此基础上对路由协议AODV,DSR和SASR进行了模拟.模拟结果显示:3种路由协议都能适应网络的拓扑结构变化,但是SASR和AODV路由协议在多跳无线Ad Hoc网络仍然具有相对的优越性.     

MR2RP: The Multi-Rate and Multi-Range Routing Protocol for IEEE 802.11 Ad Hoc Wireless Networks

This paper discusses the issue of routing packets over an IEEE 802.11 ad hoc wireless network with multiple data rates (1/2/5.5/11 Mb/s). With the characteristics of modulation schemes, the data rate of wireless network is inversely proportional with the transmission distance. The conventional shortest path of minimum-hops approach will be no longer suitable for the contemporary multi-rate/multi-range wireless networks (MR²WN). In this paper, we will propose an efficient delay-oriented multi-rate/multi-range routing protocol (MR²RP) for MR²WN to maximize the channel utilization as well as to minimize the network transfer delay from source to destination. By analyzing the medium access delay of the IEEE 802.11 medium access control (MAC) protocol, the proposed MR²RP is capable of predicting the transfer delay of a routing path and finding the best one, which has the minimum transfer delay from source to destination. The proposed MR²RP may choose a longer path but with less contention competitors and buffer queuing delay. Simulation results show that MR²RP performs the load balancing and fast routing very well, and its call blocking probability is obviously lower than that of conventional minimum-hops approach with fixed transmission rate.An erratum to this article can be found at     

Query Localization Techniques for On-Demand Routing Protocols in Ad Hoc Networks

Mobile ad hoc networks are characterized by multi-hop wireless links, absence of any cellular infrastructure, and frequent host mobility. Design of efficient routing protocols in such networks is a challenging issue. A class of routing protocols called on-demand protocols has recently found attention because of their low routing overhead. We propose a technique that can reduce the routing overhead even further. The on-demand protocols depend on query floods to discover routes whenever a new route is needed. Our technique utilizes prior routing histories to localize the query flood to a limited region of the network. Simulation results demonstrate excellent reduction of routing overheads with this mechanism. This also contributes to a reduced level of network congestion and better end-to-end delay performance of data packets.     

Performance Evaluation of IEEE 802.11 DCF in Single Hop Ad Hoc Networks

The mathematical modeling of IEEE 802.11 CSMA/CA has received considerable attention in the past few years. However there is lack of significant work considering the presence of buffer in wireless networks. Also most of the work has not followed IEEE specifications regarding inclusion of retry limits. This paper presents a new analytical model for performance evaluation of IEEE 802.11 single hop networks. The work presented here takes into consideration the presence of first order memory buffer along with the effect of traffic arrival which obeys Poisson distribution. In addition, we have considered the short retry limit to accommodate IEEE 802.11 specifications. On one hand, lack of buffering leads to high delays and under utilization of the channel. Also the absence of short retry limit tends to overestimate the throughput. By accommodating both the shortcomings, it has been proved that our model predicts the behaviour more accurately. We have been carrying out extensive simulations to validate results of our model. We have presented the performance evaluation of both the access mechanisms present in 802.11 MAC protocol.