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。     

基于定向天线的非对称无线自组网中MAC协议的研究

在采用全向天线的节点与定向天线的节点混杂的非对称网络中,传统定向MAC协议将带来新的"聋"问题和隐藏终端问题.针对这些问题,设计了NCDMAC(nested circular directional MAC)协议.在该协议中,全向节点采用多跳RTS/CTS,定向节点采用循环DRTS,定向天线嵌套旋转两周,以交换握手帧.ns2模拟仿真显示,NCDMAC协议在增加一定通信时延的情况下,能够解决非对称网络下的"聋"问题和隐藏终端问题,并带来比Multi-hop MAC和Circular MAC协议更大的网络吞吐量.     

太赫兹网络场景下节点移动感知的定向MAC协议

在太赫兹无线个域网中,通常会配备定向天线以延长网络设备数据传输距离,但在使用定向天线时存在节点发现困难、动态场景下节点位置难以预知等问题.针对太赫兹网络场景,基于IEEE802.15.3c高速网络MAC协议标准以及现有太赫兹定向MAC协议,提出一种节点移动感知的定向MAC(NMA-MAC)协议.通过微微网节点位置预知算法计算节点可能移动的位置,并将位置信息通过控制帧携带给其他节点,使节点之间能够更快传递彼此的位置信息.仿真结果表明,相比IEEE802.15.3c标准协议,NMA-MAC协议的吞吐量和传输成功率分别提高13.28％和4.58％,同时控制开销降低30.86％.     

太赫兹网络场景下节点移动感知的定向MAC协议

在太赫兹无线个域网中,通常会配备定向天线以延长网络设备数据传输距离,但在使用定向天线时存在节点发现困难、动态场景下节点位置难以预知等问题.针对太赫兹网络场景,基于IEEE802.15.3c高速网络MAC协议标准以及现有太赫兹定向MAC协议,提出一种节点移动感知的定向MAC(NMA-MAC)协议.通过微微网节点位置预知算法计算节点可能移动的位置,并将位置信息通过控制帧携带给其他节点,使节点之间能够更快传递彼此的位置信息.仿真结果表明,相比IEEE802.15.3c标准协议,NMA-MAC协议的吞吐量和传输成功率分别提高13.28％和4.58％,同时控制开销降低30.86％.     

速率自适应的树状采集型MHWSN跨层MAC协议

中高速传感器节点能量严重受限,节能是中高速传感器网络（Medium and High Rate Sensor Networks,MHWSN）中MAC协议设计的首要问题。针对SMAC协议固定占空比不能适应中高速网络中多种速率混合业务传输的特点,提出了一种适应于数据采集型应用的速率自适应的MAC协议（AMAC）。AMAC协议在SMAC基础上,采用了基于跨层的速率自适应机制和交错唤醒机制,根据节点速率动态调整占空比,上层节点较下层节点延迟一段时间后激活。仿真结果表明,在数据采集树中该算法节点速率较小时,可有效降低空闲节点的占空比、减少能量消耗,节点速率较大时,调整占空比大小,减少碰撞和阻塞发生的概率,尤其在多种速率任务突发的中高速传感器网络中,能有效提高节点的数据吞吐量并降低时延。     

基于定向天线的飞行自组网定向路由协议综述

近年来,以无人机为节点的飞行自组网因其在各个领域的不同应用而受到广泛关注.为满足复杂任务的服务质量需求,飞行自组网的路由需要提供足够高的网络性能.相比于基于全向天线的全向路由,基于定向天线的定向路由能提升信道利用率,扩大通信范围,可以使飞行自组网获得更好的网络性能和服务质量.文中综述了基于定向天线的飞行自组网定向路由,分析了在飞行自组网中应用定向天线的优势和所带来的问题,而后对现有单路径定向路由和多路径定向路由从定向天线控制机制、路由算法、使用场景和优缺点等多个方面进行详细介绍,并从天线类型、控制机制、网络性能和关键参数等多方面对这些路由协议进行定性比较,最后讨论了基于定向天线的飞行自组网定向路由协议在实际应用中和未来发展中所面临的挑战.     

无线传感器网络中基于分簇的自适应MAC协议

本文分析了目前无线传感器网络中MAC协议的不足，提出一种基于分簇的自适应MAC协议(AMAC)，该协议的时间帧长度可以根据网络拓扑和负载变化自动调整。通过仿真验证，在实时性、移动性较强的无线传感器网络中AMAC协议性能优于其它MAC协议。     

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.     

WSN中基于混合天线的PEGASIS改进算法*

针对无线传感器网络面积大、节点传输距离远的特点而导致能量消耗过快容易死亡的问题,引入定向天线,设计了基于混合天线的高能效收集路由协议(EEMC)。通过定义距离阈值,在区域内构造多条短链,短链通过链头收集链内节点数据后直接与基站通信。距离阈值根据链路位置和节点死亡情况长链系数有所变化,短链间采用全向天线传输数据,链头节点通过定向天线向远处的基站发送数据。仿真结果表明,该算法大大减缓了第一个死亡节点到来的时间,节省了每轮的网络能耗。     

自适应波束天线自组网拓扑控制算法

定向天线能显著提高无线系统的性能和容量,但采用定向天线的自组网拓扑构建问题比全向天线网络复杂。拓扑控制是一种保证网络连通和性能优化的有效手段。基于自适应波束定向天线模型提出一种拓扑控制算法,确定天线的主波束朝向,调整节点的发射功率构建拓扑。算法在保证网络连通的基础上,利用主波束的高增益,降低了节点的发射功率,从而降低节点能耗;同时利用定向天线方向性强的特点,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。     

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.     

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.     

An adaptive directional MAC protocol for ad hoc networks using directional antennas

A directional antenna can bring benefits in terms of power consumption,spatial reuse,etc.To exploit the advantage of directional antennas and improve the transmission throughput highest,this paper proposes an adaptive directional MAC protocol(ADMAC).By varying the transmission strategy according to the usage of the channel,nodes can send RTS and CTS packets omni-directionally or directionally.Also,this paper proposes a calculation method of virtual carrier sensing with collision avoidance.By the method,ADMAC protocol makes more pairs of nodes transmit and receive data simultaneously without interferences than other MAC protocols for directional antennas.The paper compares the simultaneous delivering nodes and network throughput of ADMAC with DMAC,DVCS and SDMAC under different experiment parameters.The simulation results show that the throughput of ADMAC is higher than the throughput of DMAC,DVCS and SDMAC 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.     

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.     

基于IEEE 802.15.6的无线体域网自适应MAC协议

针对无线体域网MAC协议自适应性不高且能效低的问题,提出一种基于IEEE 802.15.6的无线体域网自适应MAC协议（A-MAC）。对IEEE 802.15.6的超帧结构进行改进,竞争接入阶段和非竞争接入阶段的长度根据产生各优先级数据的节点所占的比例进行调整。竞争接入阶段又被划分为三个子阶段,子阶段的长度根据数据优先级情况进行动态调整。所有节点在竞争接入阶段按照信道接入策略竞争接入信道。最后仿真结果表明,在吞吐量、能耗和网络时延方面,使用A-MAC协议的网络性能明显优于使用IEEE 802.15.6 MAC和CA-MAC协议的网络性能。     

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.     

车载自组织网络协作MAC协议研究

车载自组织网络(Vehicular Ad Hoc Network,VANET)的关键技术之一就是 设计一个高效的媒体接入控制(Medium Access Control,MAC)协议。MAC协议因对网络的吞吐量、时延和丢包率等具有重大影响而成为研究热点。针对车载自组织网络对MAC协议的特殊性要求,提出了一种基于协作方案的TDMA MAC协议,即C-TDMA MAC。该协议中,当源节点到目的节点间直接传输失败时,其邻近辅助节点利用未被预留的时隙协作重传其先前侦听到的数据包到目的节点,而不影响其它数据包的正常传输。数值分析和仿真结果表明,所提出的协议提高了数据包成功传输的概率。