Ad Hoc网络中一种新的基于多包接收的媒体接入控制算法

该文提出了一种新的适用于Ad hoc网络的媒体接入控制算法,该算法根据节点底层的多包接收(MPR)能力以及伪随机调度表种子,来确定最优接入概率,从而充分利用节点的MPR能力,以实现明显提高网络吞吐量目的。然后,采用一种数学分析模型对算法进行了仿真,并与分群协议进行了比较。     

移动无线ad hoc网络吞吐量的计算

在网络拓扑满足网络各种不同性能指标下,本文提出了一种新的转发策略和功率控制策略来估计ad hoc网络的吞吐量.实验结果证明:该方法能够有效的估算和提高ad hoc网络的吞吐量.     

蜂窝ad hoc网络概述

一、ad hoc网络与蜂窝网络的结合 在移动无线通信网络原有的网络构架技术中通常包括蜂窝移动通信网络和无线局域网,蜂窝移动通信网络移动终端接入固定网络是基于基站的中心接人方式,而无线局域网则要通过接入点（AP）完成终端接入固定网络,这两种网络都是单跳网络。ad hoc技术所标称的是一种有别于中心接人和单跳的特征,强调多跳和无中心接入,移动终端不仅具有主机的功能,还具有路由器的功能,使得无线移动ad hoc网络被认为是下一代移动通信系统解决方案中最有希望被采用的末端网络。     

蜂窝与ad hoc融合网络的路由算法

蜂窝网络与ad hoc网络作为两种不同性质的网络结合,可以提高系统的容量和吞吐量、扩大覆盖范围、均衡小区业务、提高用户下行传输速率等融合网络路由将不再是基于单一的蜂窝或是ad hoc网络的路由算法．而是在源和目的节点之间通过多跳、代理或是蜂窝网络建立一务最佳的路径这里将介绍几种融合网络模型的路由算法,并重点介绍其中的一种算法。     

蜂窝与ad hoc融合网络的路由算法

蜂窝网络与ad hoc网络作为两种不同性质的网络结合,可以提高系统的容量和吞吐量、扩大覆盖范围、均衡小区业务、提高用户下行传输速率等等。融合网络路由将不再是基于单一的蜂窝或是ad hoc网络的路由算法,而是在源和目的节点之间通过多跳、代理或是蜂窝网络建立一条最佳的路径。这里将介绍几种融合网络模型的路由算法,并重点介绍其中的一种算法。     

一种Ad Hoc网络收方发起的媒体接入控制算法

在结合多包接收技术以及功率控制的基础上提出了一种发射能级可控的应用于Ad Hoc网络的收方发起的媒体接入控制算法，并对其吞吐量和能耗作了分析。与RTS/CTS(request to send／clear to send)握手机制相比，在一定假设条件下，网络吞吐量有着明显的提高，与此同时，系统发射功率最多可降低60％以上     

无线ad hoc网络中多路径负载平衡性能分析

提出了一种新颖的分析模型来计算无线ad hoc网络中多路径情况下的负载。该模型考虑到多路径的数目、路由的选取方法以及网络中节点的密度等条件，能够对不同网络条件下的负载进行较好的分析与理论计算。仿真结果与理论计算有良好的一致性，结果表明在无线ad hoc网络中简单地使用多路径路由并不能有效地平衡网络负载。这一结论与目前普遍认定的结论（在无线ad hoc网络中使用多路径路由和在有线网络中使用多路径路由一样，可以很好地平衡网络负载、增加网络的吞吐量）是不一致的。     

一种应用于教学实验的多点无线通信网络的设计和研制

提出了一种基于蓝牙小区域无线接入技术，该技术适用于教学实验的多点无线通信网络的设计和研制。该无线通信网络具备移动自组织(ad hoc)网络的典型特征，并有网络结构清晰、路由算法简洁等待点。运用该多点无线通信网络而设计的无线多点组网实验具备良好的教学功能。     

一种集成ad hoc与蜂窝的4G新型网格（IACG）

在第四代移动通信系统( 4G)中,采用ad hoc网络为核心技术,以满足2 0 1 0年后市场对大容量、高带宽、无缝漫游的需求,是近一两年来全球业界提出的一种崭新的技术思路和发展方向。本文根据4G工程原则和ad hoc网络框架,构建了一种新型的集成ad hoc与蜂窝网格( Integrated Cellular and Ad hoc Grid,IACG)。在此基础上,研究提出了其容量提高方案、移动预测模型、网络动态变化中的容错设计、基于代理的可靠路由协议以及低功耗无线多层优化协议,解决了当前ad hoc网络如何在移动通信领域走向实用化的关键技术     

Ad Hoc中一种改进后退机制的基于多包接收的MAC算法

物理层多包接收技术的发展给利用物理层多包接收能力的媒体接入控制（MAC）协议的设计带来了挑战。IEEE802.11 DCF是目前WIAN最成熟的分布式MAC协议之一，对其在多包接收模型下进行性能改善将有很大的应用价值。在物理层具有多包接收能力的基础上，提出了一种改进的802.11 DCF协议，并将该协议应用于现有的基于802.11 DCF的多包接收MAC算法（MDCF），理论分析和NS-2仿真实验结果表明，该算法与IEEE 802.11 DCF和MDCF相比，在网络吞吐量和时延性能方面有很大的改善。     

Embracing interference in ad hoc networks using joint routing and scheduling with multiple packet reception

We present an approach that takes advantage of multi-packet reception (MPR) to reduce the negative effects of multiple access interference and therefore increase the capacity of an ad hoc network. We analyze the performance upper bound of joint routing and scheduling for ad hoc networks that embrace interference by using MPR. We formulate the optimization problem under a deterministic model and seek to maximize the aggregate network throughput subject to minimum rate requirements. We then propose a polynomial-time heuristic algorithm aimed at approximating the optimal solution to the joint routing and channel access problem under MPR. We show the effectiveness of our heuristic algorithm by comparing its performance with the upper bound.     

Tone Dual‐Channel MAC Protocol with Directional Antennas for Mobile Ad Hoc Networks

The directional medium access control (MAC) protocol improves the throughput of mobile ad hoc networks but has a deafness problem and requires location information for neighboring nodes. In the dual‐channel directional MAC protocol [12], the use of omnidirectional packets does not require the exact location of destination node. In this letter, we propose a tone dual‐channel MAC protocol with directional antennas to improve the throughput of mobile ad hoc networks. In the proposed MAC protocol, we use a directional CTS and an out‐of‐band directional DATA tone with a new blocking algorithm to improve the spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using the Qualnet simulator.     

Application of IEEE 802.16 Mesh Networks as the Backhaul of Multihop Cellular Networks

Cellular networks have been widely used to support many new audio-and video-based multimedia applications. The demand for higher data rate and diverse services has driven the research on multihop cellular networks (MCNs). With its ad hoc network features, an MCN can offer many additional advantages, such as increased network throughput, scalability and coverage. However, providing ad hoc capability to MCNs is challenging as it may require proper wireless interfaces. In this article, the architecture of IEEE 802.16 network interface to provide ad hoc capability for MCNs is investigated, with its focus on the IEEE 802.16 mesh networking and scheduling. Several distributed routing algorithms based on network entry mechanism are studied and compared with a centralized routing algorithm. It is observed from the simulation results that 802.16 mesh networks have limitations on providing sufficient bandwidth for the traffic from the cellular base stations when a cellular network size is relatively large.     

High throughput reactive routing in multi-rate ad hoc networks

A reactive routing algorithm for multi-rate ad hoc wireless networks is proposed. It enhances the AODV protocol and achieves higher throughput by utilising the multi-rate capability of the underlying wireless channel via the MAC delay routing metric. Simulations show that the protocol leads to a significant throughput increase over traditional ad hoc routing protocols.     

Efficient routing for wireless mesh networks using a backup path

Wireless mesh networks (WMNs) have a proven record in providing viable solutions for some of the fundamental issues in wireless networks such as capacity and range limitations. WMN infrastructure includes clusters of mobile ad‐hoc networks connected through a fixed backbone of mesh routers. The mesh network can be constrained severely because of various reasons, which could result in performance degradation such as a drop in throughput or long delays. Solutions to this problem often focus on multipath or multichannel extensions to the existing ad‐hoc routing protocols. In this paper, we propose a novel solution by introducing an alternative path to the mesh backbone that traverses the mobile ad‐hoc networks part of the WMN. The new routing solution allows the mobile nodes (MNs) to establish direct communication among peers without going through the backbone. The proposed alternative ad‐hoc path is used only when the mesh backbone is severely constrained. We also propose, for the first time in WMNs, using MNs with two interfaces, one used in the mesh backbone communication and the other engaged in the ad‐hoc network. A scheme is presented for making the MN aware of link quality measures by providing throughput values to the ad‐hoc on‐demand distance vector protocol. We use piggybacking on route reply messages in ad‐hoc on‐demand distance vector to avoid incurring additional costs. We implemented our solution in an OPNET simulator and evaluated its performance under a variety of conditions. Simulation results show that the alternative ad‐hoc path provides higher throughput and lower delays. Delay analysis show that the throughput improvement does not impose additional costs. Copyright © 2012 John Wiley & Sons, Ltd.     

CAPACITY EVALUATION OF MULTI-CHANNEL WIRELESS AD HOC NETWORKS

In this paper, the capacity of multi-channel, multi-hop ad hoc network is evaluated.In particular, the performance of multi-hop ad hoc network with single channel IEEE 802.11 MAC utilizing different topologies is shown. Also the scaling laws of throughputs for largescale ad hoc networks and the theoretical guaranteed throughput bounds for multi-channel grid topology systems are proposed. The results presented in this work will help researchers to choose the proper parameter settings in evaluation of protocols for multi-hop ad hoc networks.     

Energy-Efficient Routing Algorithms Using Directional Antennas for Mobile Ad Hoc Networks

Power consumption is an important issue in the wireless ad hoc networking environment. In this paper, we present several energy-efficient routing algorithms using directional antennas for wireless ad hoc networks. These algorithms are simple to implement and are distributed and can be applied to mobile environments. We evaluate how directional antennas improve system throughput. We study the influence of the battery recovery effect and mobility on the network throughput during a network lifetime. We also present an algorithm that exploits the broadcast nature of the wireless communication environment to improve end-to-end bit error performance for a Rayleigh fading channel.     

Energy efficient multi-channel media access control for dense wireless ad hoc and sensor networks

Traditional single-channel MAC protocols for wireless ad hoc and sensor networks favor energy-efficiency over throughput. More recent multi-channel MAC protocols display higher throughput but less energy efficiency. In this article we propose NAMAC, a negotiator-based multi-channel MAC protocol in which specially designated nodes called negotiators maintain the sleeping and communication schedules of nodes within their communication ranges in static wireless ad hoc and sensor networks. Negotiators facilitate the assignation of channels and coordination of communications windows, thus allowing individual nodes to sleep and save energy. We formally define the problem of finding the optimal set of negotiators (i.e., minimizing the number of selected negotiators while maximizing the coverage of the negotiators) and prove that the problem is NP-Complete. Accordingly, we propose a greedy negotiator-election algorithm as part of NAMAC. In addition, we prove the correctness of NAMAC through a rigorous model checking and analyze various characteristics of NAMAC—the throughput of NAMAC, impact of negotiators on network capacity, and storage and computational overhead. Simulation results show that NAMAC, at high network loads, consumes 36 % less energy while providing 25 % more throughput than comparable state-of-art multi-channel MAC protocols for ad hoc networks. Additionally, we propose a lightweight version of NAMAC and show that it outperforms (55 % higher throughput with 36 % less energy) state-of-art MAC protocols for wireless sensor networks.     

一种低时延的短波自组网优化链路状态路由协议

优化链路状态路由(Optimized Link State Routing,OLSR)协议是一种先验式路由协议,网络中的所有节点通过周期性地发送控制消息来计算全网路由信息。在短波自组织网络中,节点周期性地发送控制消息会占据大量的信道资源,大幅增加网络的控制开销,浪费短波有限的带宽资源,导致网络通信性能急剧下降。其次,受到地形地貌、天线方向和接收性能的个体差异等影响,造成无线链路不稳定,导致网络中存在非对称链路,增加了通信端到端时延。为此,提出了一种低时延的短波自组网OLSR协议。该协议在执行MPR(Multipoint Relay)选择算法时综合考虑了节点的连接度和链路可靠性,在优化MPR节点个数的同时选择链路可靠性较大的节点作为MPR节点,在进行路由选择时能够利用网络中的非对称链路。仿真结果表明,该协议能优化数据包投递成功率、吞吐量、端到端时延和网络控制开销等性能指标。     

在Ad Hoc网络中TCP-SACK性能研究及改进

在Ad Hoc网中,经常发生链路失效和路由变化。TCP把数据包的丢失归结为链路拥塞,所以TCP在Ad Hoc网中表现很差。在本文中通过应用一种新的方法,基于传输包乱序检测与响应方法,研究TCP在Ad Hoc网中的性能。通过实验结果表明,此算法解决了,提高了网络的吞吐量。