SDMAC: Selectively Directional MAC protocol for wireless mobile ad hoc networks

Using directional antennas in wireless mobile ad hoc networks can greatly improve the transmission range as well as the spatial reuse. However, it will also cause some problems such as deafness problem and hidden terminal problem, which greatly impair the network performance. This paper first proposes a MAC protocol called Selectively Directional MAC (SDMAC) that can effectively address these problems and significantly improve the network throughput. Then two improvements on SDMAC are proposed. The first one is to improve the network throughput by scheduling the packets in the queue (a scheme called Q-SDMAC), thus the head-of-line (HOL) blocking problem can be addressed. The second one is to relax the assumption that each node knows the relative directions of its neighboring nodes and use caches to buffer those relative directions (a scheme named Q-SDMAC using cache). Extensive simulations show that: (1) SDMAC can achieve much better performance than the existing MAC protocols using directional antennas; (2) The network throughput can be significantly improved by scheduling the packets in the queue; (3) Using caches can still achieve high network throughput when nodes are moving; and (4) Network throughput decreases when directional antennas have side lobe gain.

Adding sense of spatial locality to routing protocols for mobile ad hoc networks

Recently, there has been an increasing interest in mobile ad hoc networks. In a mobile ad hoc network, each mobile node can freely move around and the network is dynamically constructed by collections of mobile nodes without using any existing network infrastructure. Compared to static networks, it faces many problems such as the inefficiency of routing algorithms. Also, the number of control packets in any routing algorithm increases as the mobile speed or the number of mobile nodes increases. Most of the current routing protocols in ad hoc networks broadcast the control packets to the entire network. Therefore, by reducing the number of control packets, the efficiency of the network routing will be improved. If we know where the destination is, we can beam our search toward that direction. However, without using global positioning systems, how can we do this? Define the range nodes as the 1‐hop or 2‐hop neighbors of the destination node. In this paper, we propose using the range nodes to direct our searches for the destination. It can be combined with the existing routing protocols to reduce the control overhead. We show through simulations that AODV and DSR combined with the range node method outperforms the original AODV and DSR routing protocols in terms of control packets overhead. We also show that the delay introduced in find range nodes is insignificant. Copyright © 2006 John Wiley & Sons, Ltd.     

车载自组网的现状与发展

简要介绍了车载自组网的发展历史、特点和应用领域。使用分析和比较的方法，讨论各种无线通信技术用于车载自组网的优缺点，并针对车载自组网的应用及特性提出搭建车间通信系统的设计思想和突破方向。为了便于读者跟踪国外先进的研究成果，还介绍了一些在这一领域比较活跃的研究机构以及他们的主要工作。     

Localized energy efficient routing in mobile ad hoc networks

We consider the problem of localized energy aware routing in mobile ad hoc networks. In localized routing algorithms, each node forwards a message based on the position of itself, its neighbors and the destination. The objective of energy aware routing algorithms is to minimize the total power for routing a message from source to destination or to maximize the total number of routing tasks that a node can perform before its battery power depletes. In this paper we propose new localized energy aware routing algorithms called OLEAR. The algorithms have very high packet delivery rate with low packet forwarding and battery power consumption. In addition, they ensure good energy distribution among the nodes. Finally, packets reach the destination using smaller number of hops. All these properties make our algorithm suitable for routing in any energy constrained environment. We compare the performance of our algorithms with other existing energy and non‐energy aware localized algorithms. Simulation experiments show that our algorithms present comparable energy consumption and distribution to other energy aware algorithms and better packet delivery rate. Copyright © 2006 John Wiley & Sons, Ltd.     

An efficient MAC protocol with cooperative retransmission in mobile ad hoc networks

In emerging wireless networks, cooperative retransmission is employed to replace packet retransmission between a pair of sender and receiver with poor channel condition. A cooperative MAC protocol which utilizes such benefit is proposed in this paper to improve the network performance in mobile ad hoc networks. In the proposed protocol, relay nodes between sender and receiver are used if the sender cannot communicate with the receiver reliably. Furthermore, the receiver may also stop forwarding the received data frame if the frame is received by the next‐hop receiver on the route to the final destination node. Simulation results show that the proposed protocol outperforms previous works in terms of increased transmission reliability and reduced delay time. Copyright © 2010 John Wiley & Sons, Ltd.     

Quality of service provisioning in ad hoc wireless networks: a survey of issues and solutions

An ad hoc wireless network (AWN) is a collection of mobile hosts forming a temporary network on the fly, without using any fixed infrastructure. Characteristics of AWNs such as lack of central coordination, mobility of hosts, dynamically varying network topology, and limited availability of resources make QoS provisioning very challenging in such networks. In this paper, we describe the issues and challenges in providing QoS for AWNs and review some of the QoS solutions proposed. We first provide a layer-wise classification of the existing QoS solutions, and then discuss each of these solutions.     

Contention-based forwarding for mobile ad hoc networks

Existing position-based unicast routing algorithms which forward packets in the geographic direction of the destination require that the forwarding node knows the positions of all neighbors in its transmission range. This information on direct neighbors is gained by observing beacon messages each node sends out periodically.

Due to mobility, the information that a node receives about its neighbors becomes outdated, leading either to a significant decrease in the packet delivery rate or to a steep increase in load on the wireless channel as node mobility increases. In this paper, we propose a mechanism to perform position-based unicast forwarding without the help of beacons. In our contention-based forwarding scheme (CBF) the next hop is selected through a distributed contention process based on the actual positions of all current neighbors. For the contention process, CBF makes use of biased timers. To avoid packet duplication, the first node that is selected suppresses the selection of further nodes. We propose three suppression strategies which vary with respect to forwarding efficiency and suppression characteristics. We analyze the behavior of CBF with all three suppression strategies and compare it to an existing greedy position-based routing approach by means of simulation with ns-2. Our results show that CBF significantly reduces the load on the wireless channel required to achieve a specific delivery rate compared to the load a beacon-based greedy forwarding strategy generates.     

The diameter of mobile ad hoc networks

With the prevalence of mobile devices, it is of much interest to study the properties of mobile ad hoc networks. In this paper, we extend the concept of diameter from static ad hoc network to mobile ad hoc network, which is the expected number of rounds for one node to transmit a message to all other nodes in the network, reflecting the worst end‐to‐end delay between any two node. Specifically, we investigate the diameter of identically and independently mobility model in cell‐partitioned network and random walk mobility model in two‐dimensional torus network, achieving the boundary , when (k=Ω(n)), and O(k log2k), respectively, where n is the number of nodes and k is the number of cells of network and especially under random walk mobility model . A comparison is made among the diameter of mobile ad hoc networks under identically and independently mobility model, random walk mobility model and static ad hoc network, showing that mobility dramatically decreases the diameter of the network and speed is an essential and decisive factor of diameter. Copyright © 2016 John Wiley & Sons, Ltd.     

Performance of dead reckoning‐based location service for mobile ad hoc networks

A predictive model‐based mobility tracking method, called dead reckoning, is developed for mobile ad hoc networks. It disseminates both location and movement models of mobile nodes in the network so that every node is able to predict or track the movement of every other node with a very low overhead. The basic technique is optimized to use ‘distance effect’, where distant nodes maintain less accurate tracking information to save overheads. The dead reckoning‐based location service mechanism is evaluated against three known location dissemination service protocols: simple, distance routing effect algorithm for mobility (DREAM) and geographic region summary service (GRSS). The evaluation is done with geographic routing as an application. It is observed that dead reckoning significantly outperforms the other protocols in terms of packet delivery fraction. It also maintains low‐control overhead. Its packet delivery performance is only marginally impacted by increasing speed or noise in the mobility model, that affects its predictive ability. Copyright © 2004 John Wiley & Sons, Ltd.     

Robust position-based routing for wireless ad hoc networks

We consider a wireless ad hoc network composed of a set of wireless nodes distributed in a two dimensional plane. Several routing protocols based on the positions of the mobile hosts have been proposed in the literature. A typical assumption in these protocols is that all wireless nodes have uniform transmission regions modeled by unit disk centered at each wireless node. However, all these protocols are likely to fail if the transmission ranges of the mobile hosts vary due to natural or man-made obstacles or weather conditions. These protocols may fail because either some connections that are used by routing protocols do not exist, which effectively results in disconnecting the network, or the use of some connections causes livelocks. In this paper, we describe a robust routing protocol that tolerates up to roughly 40% of variation in the transmission ranges of the mobile hosts. More precisely, our protocol guarantees message delivery in a connected ad hoc network whenever the ratio of the maximum transmission range to the minimum transmission range is at most .     

Medium access control protocols for wireless mobile ad hoc networks: issues and approaches

In this article, a comprehensive survey of the medium access control (MAC) approaches for wireless mobile ad hoc networks is presented. The complexity in MAC design for wireless ad hoc networks arises due to node mobility, radio link vulnerability and the lack of central coordination. A series of studies on MAC design has been conducted in the literature to improve medium access performance in different aspects as identified by the different performance metrics. Tradeoffs among the different performance metrics (such as between throughput and fairness) dictate the design of a suitable MAC protocol. We compare the different proposed MAC approaches, identify their problems and discuss the possible remedies. The interactions among the MAC and the higher layer protocols such as routing and transport layer protocols are discussed and some interesting research issues are also identified. Copyright © 2003 John Wiley & Sons, Ltd.     

Localized power‐aware alternate routing for wireless ad hoc networks

In this paper, we design a localized power‐aware alternate routing (LPAR) protocol for dynamic wireless ad hoc networks. The design objective is to prolong the lifetime of wireless ad hoc networks wherein nodes can adaptively adjust their transmission power based on communication ranges. LPAR achieves this goal via two phases. In the first phase, energy draining balancing is achieved by identifying end‐to‐end paths with high residual energy. The second phase is designed to effectively reduce the power consumed for packet forwarding. This is achieved by iteratively performing adaptive localized power‐aware alternate rerouting to bypass each (potentially) high‐power link along the end‐to‐end path identified in the first phase. Further, the design of LPAR enables nodes to collect their neighborhood information ‘on‐demand’, which can effectively reduce the overhead for gathering such information. LPAR is suitable for both homogeneous and non‐homogeneous networks. Simulation results demonstrate that LPAR achieves improved performance in reducing protocol overhead and also in prolonging network lifetime as compared with existing work. Copyright © 2008 John Wiley & Sons, Ltd.     

移动分布式无线网络中具有QoS保证的UPMA协议

该文基于有效竞争预约接入、无冲突轮询传输的思想提出了支持节点移动性、多跳网络结构和服务质量(QoS)的依据用户妥善安排的多址接入(UPMA)协议。它大大提高了信道的使用效率,保证了发送节点能快速接入信道,同时,最大程度地保证所有实时业务的时延和带宽要求。最后,我们考察了它对Internet数据业务的支持性能。     

自组网路由协议综述

自组网路由协议用于监控网络拓扑结构变化,交换路由信息,定位目的节点位置,产生、维护和选择路由,并根据选择的路由转发数据。本文综述了自组网路由协议研究方面的一些最新工作,描述了设计自组网路由协议所面临的问题,并着重对该研究开展以来所提出的各种主要协议进行了对比、分析和分类阐述,为进一步的研究提出了新的课题。     

Mobility assessment on‐demand (MAOD) routing protocol for mobile ad hoc networks

In ad hoc wireless networks, the high mobility of hosts is usually a major reason for link failures. The general ‘shortest path’ based routing protocols may not lead to stable routes. In this paper, we propose a mobility assessment on‐demand (MAOD) routing protocol to select a stable route in order to enhance system throughput and performance. An error count parameter is used to judge whether a host is highly mobile. The proposed MAOD routing protocol is an on‐demand routing protocol similar to dynamic source routing (DSR). The difference between MAOD and DSR is in the path selection method. Because MAOD takes the mobility of hosts into consideration, it will select a more stable and reliable path than DSR. In comparison, DSR only considers whether this route is a shortest path or not. Finally, the system performance is analyzed by using the global mobile simulation (GloMoSim) simulator. We can observe that MAOD routing protocol outperforms DSR routing protocol especially in the high mobility environment. Copyright © 2004 John Wiley & Sons, Ltd.     

低开销的MANET网络按需路由协议

针对简单泛洪效率低的问题,提出了一个限制洪泛的高效的路由广播算法,通过Euclidean距离来限制路由发现过程中请求分组被转发的次数;研究了减少路由维护开销,并降低路由发现的频率的方法,提出了一个基于节点高度的路由修复与优化算法,该算法使用节点监听来对链路断裂的路由进行修复与优化.基于限制泛洪的高效的路由广播算法和路由修复优化算法,提出了一种新的低开销的MANET网络按需路由协议LOOR(low overhead on-demand routing).仿真结果表明,新协议增强了路由的顽健性,减少了路由跳数,降低了路由发现的频率,提高了数据分组递送率,并显著地降低了路由控制开销.     

A survey on congestion control for mobile ad hoc networks

Congestion control is a key problem in mobile ad hoc networks. The standard congestion control mechanism of the Transmission Control Protocol (TCP) is not able to handle the special properties of a shared wireless multi‐hop channel well. In particular, the frequent changes of the network topology and the shared nature of the wireless channel pose significant challenges. Many approaches have been proposed to overcome these difficulties. In this paper, we give an overview over existing proposals, explain their key ideas and show their interrelations. Copyright © 2007 John Wiley & Sons, Ltd.     

Exploring the performance of TCP vegas in mobile ad hoc networks

Recent research efforts in mobile ad hoc networks have concentrated on examining the behaviour of TCP Reno over various ad hoc routing protocols and have suggested a number of extensions to improve its performance. TCP Vegas, which takes a proactive approach to congestion avoidance, has not so far been examined as a viable alternative to TCP Reno in wireless environments and no effort has been made to analyse its performance over routing protocols for MANETs. This paper evaluates using extensive simulation experiments the performance behaviour of TCP Vegas over a proactive (destination sequenced distance vector) and two reactive (dynamic source routing and ad hoc on demand distance vector) routing protocols and compares it against that of TCP Reno. Copyright © 2004 John Wiley & Sons, Ltd.     

Supporting multicasting in mobile ad‐hoc wireless networks: issues,challenges, and current protocols

The basic philosophy of personal communication services is to provide user‐to‐user, location independent communication services. The emerging group communication wireless applications, such as multipoint data dissemination and multiparty conferencing tools have made the design and development of efficient multicast techniques in mobile ad‐hoc networking environments a necessity and not just a desire. Multicast protocols in mobile ad‐hoc networks have been an area of active research for the past couple of years. This paper summarizes the activities and recent advances in this work‐in‐progress area by identifying the main issues and challenges that multicast protocols are facing in mobile ad‐hoc networking environments, and by surveying several existing multicasting protocols. This article presents a classification of the current multicast protocols, discusses the functionality of the individual existing protocols, and provides a qualitative comparison of their characteristics according to several distinct features and performance parameters. Furthermore, since many of the additional issues and constraints associated with the mobile ad‐hoc networks are due, to a large extent, to the attribute of user mobility, we also present an overview of research and development efforts in the area of group mobility modeling in mobile ad‐hoc networks. Copyright © 2001 John Wiley & Sons, Ltd.     

无线自组织网中VoIP性能研究

目前,VoIP技术及其业务迅速发展,在无线自组织网络中有广泛的应用,有必要对于VoIP在无线自组网中的传输进行分析研究。利用NS-2作为仿真工具对G.711编码标准下多跳无线自组织网中VoIP的传输进行仿真,使用802.11MAC层协议和AODV路由层协议。实验结果表明,无线自组织网络环境下VoIP系统性能(包括丢包率、时延等)受到多跳影响。