移动AdHoc网络的单信道媒体接入协议

AdHoc网络中的信道接入是一个比较复杂的问题,单信道接入协议是目前AdHoc网络中应用最广泛的,本文介绍了AdHoc网络中MAC协议需要解决的主要问题和设计要求,并列举分析了几种典型的基于CSMA/CA的由原端发起的单信道接入协议。最后总结了在MAC协议中常用的退避算法:二进制退避算法(BEB)和倍数增线性减算法(MILD),指出其中存在的问题。     

移动Ad hoc网络的单信道媒体接入协议

Ad hoc网络中的信道接入是一个比较复杂的问题，单信道接入协议是目前Ad hoc网络中应用最广泛的，本文介绍了Ad hoc网络中MAC协议需要解决的主要问题和设计要求，并列举分析了几种典型的基于CSMA／CA的由原端发起的单信道接入协议。最后总结了在MAC协议中常用的退避算法：二进制退避算法（BEB）和倍数增线性减算法（MILD），指出其中存在的问题。     

基于Ad hoc网络的退避算法研究

在移动Ad hoc网络中,无线信道由多个节点共享,合理协调多个节点访问共享信道的媒体接入控制(MAC,Medium Access Control)协议是移动Ad hoc网络的关键技术之一。退避算法在MAC协议中起着至关重要的作用。针对目前退避算法存在的问题,本文提出了一种改进算法,根据网络节点发送数据包成功与否,预测网络信道空闲或繁忙的趋势,应用趋势合理地调节退避算法中节点发送数据时退避值的大小,并通过Omnet++软件对算法进行了仿真分析对比。     

一种用于移动自组织网的多址接入动态时延退避策略

在移动Ad Hoc网络中，信道接入公平性和吞吐率是MAC协议需解决的重要问题，而IEEE802．11等协议采用的二进制指数退避算法BEB难以满足公平性要求。本文提出了一种基于对节点竞争失败次数（无效RTS）进行计数的方法估计信道争用情况，动态地分配退避计数器初值，从而实现移动Ad Hoc网络的公平多址接入。研究表明，该接入方法能够有效地反映源节点特性，接入公平性好，同时在高负荷和低负荷的情况下，都能提高网络吞吐量，提供良好的QoS保障。     

Ad Hoc网络信道接入协议

文章首先介绍了AdHoc网络特有的隐终端和暴露终端问题 ,并对可能的解决方法进行了分析。在总结了前人工作的基础上 ,将AdHoc网络信道接入协议划分成基于单信道、双信道和多信道三类。文章还介绍了几种具有代表性的单信道接入协议 ,并给出了AdHoc网络信道接入协议的发展动向     

移动Ad Hoc网络的MAC协议综述

媒体访问控制（MAC）协议能否有效地使用无线信道的有限资源．对AdHoc网络的性能起着决定性的作用。AdHoc网络中MAC协议设计的复杂性源自节点的移动性、链路的易变性和缺乏中心协调性。本文首先介绍了AdHoc网络中MAC协议的作用．说明了MAC协议的设计挑战．然后对现有的各种MAC协议进行了详尽的分类比较和分析．最后对MAC协议进行了总结和展望。     

无线数据通信网中的信道接入协议研究

信道接入协议（MAC）是无线数据通信协议的重要组成部分。由于无线信道是一个开放、共享的信道，网络节点在通信过程中存在隐终端和暴露终端问题。基于目前无线通信常用的MAC协议存在的问题，着重分析了基于扩频码的信道接入协议，该协议利用扩频码的正变特性，使得网络中各节点可以同时占用信道而互不干扰，较好地解决了信道争用问题，提高了系统效率。同时指出，在选择MAC协议时，应根据无线网络的拓扑结构及特点灵活选择，以提高网络性能。     

一种新的Ad Hoc网络的MAC协议及实现

MAC协议是无线AdHoc网络的一个重要的研究领域,特别是暴露终端和隐终端的解决尤为重要,同时网络的无组织性和多跳性也给接入带来了麻烦。首先介绍了MAC协议设计所面临的各种问题,然后叙述了一种新的在单信道下的MAC接入方法,采用了CSMA和时隙相结合的方式来提高效率,部分地解决了暴露终端和隐终端的问题,同时提高了路由效率。论述了如何在软件无线电平台以及嵌入式系统上实现这种接入方法。     

一种基于实时优化思想的多址接入协议性能分析

该文提出了一种基于慢退避和实时优化思想的碰撞减少多址接入CRMA (Collision Reduced Multiple Access)协议。CRMA协议将实时优化的思想同慢退避的思想相结合,有效地解决了IEEE 802.11协议二进制指数退避算法成功发送数据帧后没有记录网络当前繁忙程度的缺点,能够更准确地记录数据帧成功发送后高负荷网络的退避阶数,降低数据帧接入信道的碰撞概率,提高无线信道的利用率。新的多址接入协议能够与现有的IEEE 802.11协议完全兼容,具有简单、无开销、完全分布性和自适应性的特点。分析和仿真结果表明,CRMA协议较之改进前的IEEE 802.11协议和其它最新的多址接入算法能够更有效地利用网络中已有的信息,更准确地估计网络当前的竞争状态,表现出更好的网络性能。     

一种新的紫外光自组织通信网络MAC层避退算法

紫外光自组织通信网络是把紫外光与自组织网络相结合的,能够利用自组织网络的多跳特性来克服紫外光距离有限性的通信网络。为了使紫外光自组织通信网络中各个节点能够对有限的信道资源进行充分与公平的利用,需要对网络协议栈中的第二层——媒介接入控制层上的传统算法进行优化。本文以媒质接入控制层(MAC,Media Access Control)传统上采用的二进制指数退避算法为基础,以提高公平性为目的,提出了依据退避计数器值的随机选取是否合理,继而采取相应的奖励惩罚机制的新算法。研究结果表明:新算法提高了无线紫外光自组织通信网络中各节点接入信道的公平性,并在信道吞吐量和信道接入公平性之间达到了一个较好的折衷。     

A survey and qualitative analysis of mac protocols for vehicular ad hoc networks

In order to avoid transmission collisions in mobile ad hoc networks (MANETs), a reliable and efficient medium access control (MAC) protocol is needed. Vehicular MANETs (VANETs) have vehicles as network nodes and their main characteristics are high mobility and speed. Active safety applications for VANETs need to establish reliable communications with minimal transmission collisions. Only few MAC protocols designed for MANETs can be adapted to efficiently work in VANETs. In this article we provide a short overview on some MANET MAC protocols, and then we summarize and qualitatively compare the ones suited for VANETs     

Location-Aware Two-Phase Coding Multi-Channel MAC Protocol (LA-TPCMMP) for MANETs

In classical code division multiple access (CDMA) based multi-channel medium access control (MAC) protocols for mobile ad hoc networks (MANETs), numerous exchanges of neighborhood information are required for code assignment such that nodes within a two-hop separation will adopt different transmission codes and therefore avoid the hidden terminal problem (HTP). However, such expensive communication overhead for code assignment is not desirable since it will cause an under-utilization of bandwidth, energy inefficiency and longer delays, which can significantly degrade the network performance. In this paper, a novel location-aware multi-channel MAC protocol is presented for a large-scale dense MANETs based on a scalable two-phase coding scheme, where the first-phase code is used for differentiating adjacent cells and the second-phase code is employed for distinguishing nodes in one specific cell. A node knows its first-phase code from its location information and requests its second-phase code from its cell leaden. This protocol eliminates the HTP during data transmission without the periodical exchange of neighborhood information. Furthermore, the mechanism of collision resolution in the control channel is described. The performance of the proposed protocol is analyzed in terms of the control overhead and delay. The theoretical results are confirmed by extensive simulations and it is shown that the new protocol significantly outperforms the classical CDMA-based multi-channel MAC protocols     

Joint Design of Routing and Medium Access Control for Hybrid Mobile Ad Hoc Networks

Efficient routing and medium access control (MAC) are very important for Mobile Ad hoc Networks (MANETs). Most existing routing and MAC protocols consider homogeneous ad hoc networks, in which all nodes are modeled as the same, i.e., they have the same communication capabilities and characteristics. Although a homogeneous network model is simple and easy to analyze, it misses important characteristics of many realistic MANETs such as military battlefield ad hoc networks. In addition, a homogeneous ad hoc network suffers from poor performance and scalability. In many ad hoc networks, multiple types of nodes do co-exist; and some nodes have larger transmission power, higher transmission data rate, and better processing capability, are more reliable and robust than other nodes. Hence, a hybrid network model is more realistic and provides many advantages for designing better routing and MAC protocols. In this paper, we present a new routing protocol called Hybrid Routing, which is specifically designed for hybrid MANETs. In addition, a novel MAC protocol is jointly designed for hybrid MANETs. Extensive simulations demonstrate that the proposed routing MAC protocols have very good performance.

面向无人机自组网和车联网的媒体接入控制协议研究综述

随着移动通信技术的迭代更新,车联网(VANET)和无人机自组网(FANETs)已成为通信网络的重要组成部分,而媒体接入控制(MAC)协议则是移动自组织网络未来发展的核心研究内容之一.安全控制信息和用户业务信息是自组织网络最主要的两类信息,而两者不同的服务质量(QoS)需求对MAC机制的设计带来了严峻的考验.该文主要考虑...     

Intelligent medium access for mobile ad hoc networks with busytones and power control

In mobile ad hoc networks (MANETs), one essential issue is how to increase channel utilization while avoiding the hidden-terminal and the exposed-terminal problems. Several MAC protocols, such as RTS/CTS-based and busy-tone-based schemes, have been proposed to alleviate these problems. In this paper, we explore the possibility of combining the concept of power control with the RTS/CTS-based and busy-tone-based protocols to further increase channel utilization. A sender will use an appropriate power level to transmit its packets so as to increase the possibility of channel reuse. The possibility of using discrete, instead of continuous, power levels is also discussed. Through analyses and simulations, we demonstrate the advantage of our new MAC protocol. This, together with the extra benefits such as saving battery energy and reducing cochannel interference, does show a promising direction to enhance the performance of MANETs     

MANETs中智能天线和功率控制的应用

分析了MANETs中基于CDMA的MAC协议存在的问题,提出在协议中引入智能天线和功率控制技术来解决多址干扰和远-近效应等问题.对采用智能天线和功率控制技术的MAC协议的工作原理进行了阐述,并通过仿真评估了智能天线与功率控制技术结合后对网络吞吐量和节点耗能的影响.研究结果表明,在MANETs中使用智能天线和功率控制技术可以有效地提高网络的吞吐量,降低节点的能耗.     

Design and analysis of a denial-of-service-resistant quality-of-service signaling protocol for MANETs

Quality-of-service (QoS) signaling protocols for mobile ad hoc networks (MANETs) are highly vulnerable to attacks. In particular, a class of denial-of-service (DoS) attacks can severely cripple network performance with relatively little effort expended by the attacker. A distributed QoS signaling protocol that is resistant to a class of DoS attacks on signaling is proposed. The signaling protocol provides QoS for real-time traffic and employs mechanisms at the medium access control (MAC) layer, which serve to avoid potential attacks on network resource usage. The key MAC layer mechanisms that provide support for the QoS signaling scheme include sensing of available bandwidth, traffic policing, and rate monitoring, all of which are performed in a distributed manner by the mobile nodes. The proposed signaling scheme achieves a compromise between signaling protocols that require the maintenance of per-flow state and those that are completely stateless. The signaling scheme scales gracefully in terms of the number of nodes and/or traffic flows in the MANET. The authors analyze the security properties of the protocol and present simulation results to demonstrate its resistance to DoS attacks.     

A Highly Reusable Code Assignment Approach with Modified Busy Tone Signaling for CDMA-Based Ad Hoc Networks

Medium access control (MAC) protocol is among the most active topics of research in ad hoc networks. With the CDMA-based MAC protocol the code allocation plays an important role and has significant impact on the protocol performance. In this paper, we propose a distributed CDMA code assignment protocol for the mobile ad hoc networks (MANETs). The protocol is mainly composed of (1) a modified busy tone signaling mechanism that protects on-going data transmission as well as distributes code usage information, and (2) a set of specially designed code selection rules that work by taking into consideration whether relevant nodes are in the transmitting or receiving state. By combining the two proposed schemes with the conventional request-to-send (RTS)/clear-to-send (CTS) dialogue and power control mechanism, our protocol is able to increase CDMA code reusability. The simulation results indicate that the proposed protocol indeed performs better than the static and dynamic code assignment methods (either with or without power control) in terms of successful transmission rate and successful code assignment rate. And instead of sending continuously, the proposed modified busy tone mechanism only issues busy tone signal in randomly selected cycles, which may save battery energy as compared to conventional busy tone implementations. Moreover, the proposed code selection rules and the modified busy tone signaling may also be integrated into existing MAC protocols, either separately or in combination.     

无线传感器网络MAC协议的研究与改进

研究和分析了当前无线传感器网络(WSN)中介质访问控制(MAC)协议、IEEE802.11和IEEE802.15.4 MAC协议的各种性能,并结合传感网络介质访问协议(S-MAC)中低占空比休眠机制对IEEE802.15.4介质访问协议进行改进.用NS-2仿真软件对各种协议进行仿真,仿真结果表明改进后的MAC协议可大...