LODMAC: Location Oriented Directional MAC protocol for FANETs

Flying Ad Hoc Network (FANET) is a novel mobile ad hoc network type where the communicating nodes are Unmanned Aerial Vehicles (UAVs). FANETs promise many new ways for both civilian and military applications. Today, traditional omnidirectional antennas are deployed on UAV nodes which result in reduced spatial reuse and limited network capacity. Alternatively, deployment of directional antennas can significantly increase the capacity, spatial reuse and communication range of FANETs. In addition, being aware of the exact locations of the neighboring nodes in a FANET is vital especially for directional ad hoc multi-UAV scenarios. In this paper, we present a novel MAC protocol, LODMAC (Location Oriented Directional MAC), which incorporates the utilization of directional antennas and location estimation of the neighboring nodes within the MAC layer. By defining a new Busy to Send (BTS) packet along with the Request to Send (RTS) and Clear to Send (CTS) packets, LODMAC effectively addresses the well known directional deafness problem. In terms of throughput, utilization, average network delay and fairness, LODMAC protocol outperforms the well-known DMAC (Directional MAC) protocol which puts LODMAC to be a robust mile-stone for the on-coming FANET MAC protocols.     

无线中继网络中基于方向天线的MAC协议

无线中继网络是指网络中的节点互相通信成为中继节点之间,中继节点之间距离很近可以形成协作分集,该文对这种网络进行了研究,引入多天线技术(MIMO)中的波束成型技术来消除信道间干扰,实现并行传输数据,分析了协作传输策略,结合协作传输策略对中继节点的功率分配进行了优化,基于合协作传输策略设计了一种基于方向天线的MAC协议.经过分析和实验仿真,基于MIMO波束成型的协作传输方法在相同情况下比其它的方法增加15％以上的信道容量.     

基于自适应波束天线的局部优化拓扑控制算法

拓扑控制有助于提高ad hoc网络的性能,采用定向天线的自组网拓扑控制比全向天线网络更为复杂。基于自适应波束定向天线模型提出一种局部区域优化的拓扑控制算法。该算法利用分簇的思想将网络划分为可重叠的多个区域,区域内节点采用最小生成树（MST）的思想确定邻居关系,通过调整节点发射功率,改变天线波束的朝向、宽度和增益来构建拓扑。算法减小了节点的平均度数,降低了节点的发射功率,从而降低节点能耗,减少了节点间干扰,提高了网络吞吐量,仿真结果表明,算法显著提高了网络性能。     

On-Demand Medium Access in Multihop Wireless Networks with Multiple Beam Smart Antennas

The paper presents a detailed discussion of various issues involved in designing a medium access control (MAC) protocol for multihop wireless networks with nodes employing multiple beam smart antennas. Multiple beam smart antennas can form several beams simultaneously and can initiate concurrent transmissions or receptions .in them, thereby increasing the throughput of the bottleneck nodes. Traditional on-demand MAC protocols for omnidirectional and single beam directional antennas based on the IEEE 802.11 distributed coordination function (DCF) mechanism cannot take advantage of this unique capability of multiple beam antennas as they do not facilitate concurrent transmissions or receptions by a node. This paper introduces a novel protocol, hybrid MAC (HMAC), which enables concurrent packet reception (CPR) and concurrent packet transmission (CPT) at a node equipped with multiple beam antennas and is backward compatible with IEEE 802.11 DCF. Simulation results show the superior performance of HMAC in most ad hoc scenarios. Moreover, in some sample topologies, the throughput of HMAC is close to the theoretical maximum. The paper also presents a wireless mesh network architecture with heterogeneous antenna technologies and illustrates the advantages of employing multiple beam smart antennas and HMAC in such networks.     

Ad hoc网络中基于定向天线的MAC协议

介绍基于定向天线的MAC协议,根据这些协议所涉及到的天线模型、发射接收模式以及使用定向天线所面临的定向隐藏终端和聋节点问题等,对Ad hoc网络中配置定向天线的相关MAC协议、问题及其解决办法进行分析比较。结果表明,基于定向天线的MAC协议能提高Ad hoc网络的整体性能。     

一种基于方向天线和时间同步机制的多信道无线网状网MAC协议

在城市小区和广阔的农村建立低成本的无线网状网,为无线终端用户提供高速的接入服务,是一项极具现实意义的工作.设计了一种适合于此类网络的MAC层协议称为Mesh-MAC,该协议建立在已有的IEEE 802.11硬件产品基础上,每两个节点之间的通信是由一对方向天线完成,通过一种全新的时间同步方案,可以实现M ESH网内高效的数据转发.仿真结果表明,与IEEE 802.11及2P协议相比,Mesh-MAC协议在吞吐量和端到端传输延时等方面,都有明显的改善.     

基于自适应定向天线的移动Ad Hoc网络MAC层数据传输机制

针对移动Ad Hoc网络中定向天线引入所带来的隐藏节点、聋节点等问题,提出一种新的MAC协议——AMAC.AMAC在使用定向天线的基础上,能够使得物理层根据环境自适应调整天线参数,克服传统定向天线存在的缺陷,大幅提高网络的吞吐量及空分复用率.与同类协议相比,数据冲突、延迟、丢失等情况将被缩小到可容忍范围.     

A MAC protocol for low-rate UWB wireless sensor networks using directional antennas

Ultra-wideband (UWB) is a key solution for wireless connectivity, characterized by ultralow power consumption and a good degree of robustness to interference and multipath fading. Evidence of its significance, is its recent use in the IEEE 802.15.4a standard. UWB technology with joint consideration of directional antennas can benefit when compared to classical omni-directional antennas from the energy conservation viewpoint, which is of fundamental concern when it comes to wireless sensor networks (WSNs). However, exploiting directionality requires new approach in the design of a medium access control (MAC) protocol to be applied. In this work, idle nodes continuously rotate their receiving beams over 360° until a predefined preamble trailer is detected. The resulting scheme is a directional ultra-wideband MAC protocol, named DU-MAC, which deals effectively with the problem of deafness and the problem of determination of neighbors’ location. Simulation-based studies will demonstrate the effectiveness of the proposed protocol in many critical parameters, such as throughput and network lifetime.     

使用定向天线的骨干无线网格网络容量研究

定向天线能够提高无线网格网络（WMN）的空间复用率,因而影响了WMN的容量。虽然目前许多文献已经提出使用定向天线的介质访问控制方案、路由协议和拓扑控制方法去提高MWN的性能,但是在理论上研究配置定向天线的MWN的容量仍然是必要的。用渐进的分析方法对使用定向天线的骨干WMN的容量进行了研究,分析了定向天线对容量的影响,并推导出网格路由器平均吞吐量上限。结果表明在接入点数量达到一定的门限时,定向天线的使用有效地增大了网络的容量。     

A directional MAC protocol with long-range communication ability in ad hoc networks

To address the problem that long-range communication capability in ad hoc networks using directional antenna is not generally utilized,a directional media access control (DMAC) protocol with long-range communication (LRC) capability in ad hoc networks is proposed.In the LRC-DMAC,the intermediate node uses a long-range orientation (LRO) algorithm to help the transmitter obtain the directional information of the receiver which is two hops away.Consequently,the long-range link between such two hops nodes can be set up.According to whether the received power information is available or not,we propose two types of LRO algorithm:without the received power information,a basic LRO obtains the approximate directional informa-tion of the long-range receiver by a geometric relationship;however,the LRO-PI can calculate the accurate directional information of the long-range receiver using the received power.Performance analysis indicates that the LRO algorithm achieves high accuracy when the relevant parameters are properly chosen.Simulation results show that the establishment of long-range links can effectively improve the network throughput and reduce the end-to-end delay.     

Efficient broadcasting in ad hoc wireless networks using directional antennas

Using directional antennas to conserve bandwidth and energy consumption in ad hoc wireless networks (or simply ad hoc networks) is becoming popular. However, applications of directional antennas for broadcasting have been limited. We propose a novel broadcast protocol called directional self-pruning (DSP) for ad hoc wireless networks using directional antennas. DSP is a nontrivial generalization of an existing localized deterministic broadcast protocol using omnidirectional antennas. Compared with its omnidirectional predecessor, DSP uses about the same number of forward nodes to relay the broadcast packet, while the number of forward directions that each forward node uses in transmission is significantly reduced. With the lower broadcast redundancy, DSP is more bandwidth and energy-efficient. DSP is based on 2-hop neighborhood information and does not rely on location or angle-of-arrival (AoA) information. Two special cases of DSP are discussed: the first one preserves shortest paths in reactive routing discoveries; the second one uses the directional reception mode to minimize broadcast redundancy. DSP is a localized protocol. Its expected number of forward nodes is O(1) times the optimal value. An extensive simulation study using both custom and ns2 simulators show that DSP significantly outperforms both omnidirectional broadcast protocols and existing directional broadcast protocols.     

适用于水声传感网络的多链路传输MAC协议

针对水声传感网络存在的高时延、低信道利用率等问题,提出一种新的多链路传输介质访问控制协议。该协议节点通过RTS/CTS握手协议交互时延信息和传输计划,实现多条链路传输数据。在汇聚节点接收多个节点的数据时,汇聚节点根据节点的时延和接收的数据帧大小规划节点之间的发送顺序,避免传输冲突造成的能量损失和低信道利用率,同时为得到最大网络吞吐量,给出最优退避窗口值的理论表达式。仿真结果表明,与RC-FAMA、S-FAMA等协议相比,该协议能有效提高水声传感网络的吞吐量,降低传输冲突,从而延长水下节点的工作时间。     

基于功率优化的Ad hoc网络定向媒质接入控制

由于无线Ad hoc网络是一种由移动终端组成、网络拓扑结构动态变化的对等、自组织、多跳网络,使得传输带宽、传输功率成为具有挑战性的任务之一。分析了目前通常采用的信道接入技术(如：全向天线;CSMA／CA和洪泛)及存在的问题;在此基础上,为保证有效利用传输带宽,提高功率利用率,给出了用于定向天线的MAC的解决方案(简称DMAC)。节点通过虚拟载波侦听来重定向,实现定向传输,使功率得到优化。     

Ad Hoc网络中具有远距离通信能力的方向性MAC协议

针对在使用方向性天线的AdHoc网络中没有合理利用远距离传输优势的问题,提出了一种支持远距离通信的方向性MAC协议.在该方向性MAC协议中,中间节点会利用一种远距离定向算法帮助发送节点获取位于两跳远的目的节点的定向信息从而建立远距离链路,这种链路的建立有助于解决局部拥塞,同时降低传输延时.本文中根据MAC层能否获得信号接收功率信息提出了两种LRO算法:基本LRO算法不使用信号接收功率信息,仅利用几何关系获得近似的远距离节点定向信息;而LRO-PI(LRO with power in for mation)算法在利用信号接收功率信息后可以进行更加准确的远距离节点定向.性能分析表明,在合理地选择相关参数后,LRO算法有着很高的定位准确性.并且仿真结果表明远距离链路的建立可以有效地提高网络的吞吐量,并且降低端到端延时.     

自组网中基于自适应波束天线的拓扑控制算法

定向天线自组网拓扑的构建问题比全向天线网络复杂.基于自适应波束定向天线模型提出一种分布式拓扑控制算法,通过调整节点发射功率,改变天线波束的朝向、宽度和增益来构建拓扑.网络中每个节点收集其邻居节点信息,采用功率控制调度策略选择最优相邻节点,并选取覆盖所有最优相邻节点的最小发射功率为此节点的发射功率.算法在保证网络连通性与无向性的同时,降低了节点的发射功率,减小了节点的平均度数,从而降低节点能耗,减少了节点间干扰,提高了网络吞吐量.仿真结果表明,算法显著提高了网络性能.     

采用方向性天线的Ad Hoc网络邻居发现策略研究

为了有效支持MAC和路由协议,对采用方向性天线的邻居发现策略进行了研究,提出了基于Hello消息的邻居发现策略(HDND),尽量通过全向天线广播两跳Heno消息发现方向性邻居,只有当节点成为孤立节点或网络可能存在网络分区时,才利用方向性天线进行扫描发现,该策略既降低了方向性天线通过扫描进行邻居发现的高代价,又解决了网络中出现的孤立节点和网络分区问题.理论分析了方向性天线的高传输能力带给分组转发性能的提高,并利用仿真验证了分析结果.     

定向天线卫星网络空间重用的带宽预留算法

基于无线网络中设计提供服务质量(quality of service,QoS)的路由协议是一项具有挑战性的工作,提出无线卫星网络中基于定向天线的服务质量保证的空间重用的带宽预留算法。卫星网络中许多音/视频会议、远程教育等重要应用,需要服务质量保证。无线网络中的定向天线技术提供了显著增加空间重用性的能力,提高无线网络中的数据传输效率。研究使用定向天线的无线卫星网络中基于时分多址的带宽预留算法,该算法给不同方向的地面终端分配相同时隙来提高带宽资源的空间重用性,提高通信效率。通过模拟实验分析研究证明,该算法在服务质量调用成功率、吞吐量和延迟方面有比较好的性能。     

一种由接收端发起的无线传感器网络MAC协议

在无线传感器网络(Wireless sensor networks,WSN)中,现有的基于接收节点发起的异步MAC层协议,在计算接收节点唤醒时刻时,多采用维持邻居节点的伪随机唤醒时间表的方法。在网络动态负载条件下,此方法不能动态地改变节点唤醒间隔,从而带来较高的数据传输冲突率及较大的数据传输延时。为了解决此问题,本文提出一种新协议HELD-MAC(High energy efficiency and　low delay MAC),保证节点之间具有不同的唤醒时间,同时能够准确预测接收端唤醒时刻,而且接收端可以根据网络负载情况动态改变唤醒间隔。同时为了减轻能量黑洞问题,协议根据节点的剩余能量,自适应地改变节点的最小唤醒间隔。通过仿真对HELD-MAC进行评估,与RI-MAC,PW-MAC等对比,在数据传输延时、能量消耗、网络吞吐量和传输碰撞方面具有较大优势。     

定向天线在Ad Hoc网络中的设计与应用

定向天线可以有效提升Ad hoc网络路由协议和接入控制的性能,但同时也带来了一些新的问题;针对隐藏终端和听不见问题,文中设计两种新的协议:SDR-MAC协议和NDDMAC协议;最后,对NDDMAC协议进行仿真,结果表明,NDDMAC总的网络吞吐量优于现有的ORTS-OCTS协议和DMAC协议,有效提升了Ad hoc网络的整体性能。     

适用于飞行自组网的闲置时隙预约TDMA协议

在飞行自组网中,固定时隙分配时分多址接入（TDMA）协议存在闲置时隙无法成功使用的问题。通过对TDMA协议引入闲置时隙预约机制,提出一种支持业务优先级传输机制的闲置时隙预约TDMA协议。采用短帧长的方式满足协同与控制业务的低时延传输需求,并利用闲置时隙预约机制允许节点使用闲置时隙传输感知业务,从而满足感知业务的高吞吐量传输性能要求。仿真结果表明,与CF-MAC和CTMAC协议相比,该协议能够在降低传输时延的同时,有效提高信道利用率和网络吞吐量。