On the use of learning automata in the control of broadcast networks: a methodology

Due to its fixed assignment nature, the well-known time division multiple access (TDMA) protocol suffers from poor performance when the offered traffic is bursty. In this paper, an adaptive TDMA protocol, which is capable of operating efficiently under bursty traffic conditions, is introduced. According to the proposed protocol, the station which is granted permission to transmit at each time slot is selected by means of learning automata (LA). The choice probability of the selected station is updated by taking into account the network feedback information. The system which consists of the LA and the network is analyzed and it is proven that the choice probability of each station asymptotically tends to be proportional to the probability that this station is not idle. Although there is no centralized control of the stations and the traffic characteristics are unknown and time-variable, each station tends to take a fraction of the bandwidth proportional to its needs. Furthermore, extensive simulation results are presented, which indicate that the proposed protocol achieves a significantly higher performance than other well-known TDMA protocols when operating under bursty traffic conditions.     

一种短波地空网MAC协议设计与仿真

针对传统TDMA固定分配方案在节点间业务量动态变化时,存在着信道利用率较低的问题,设计了一种基于全局时隙转让的短波地空网动态TDMA协议（TDMA protocol based on Whole Timeslot Transfer,WTT-TDMA）,以可靠性较高的地面节点作为控制中心,实现时隙分配可控下的动态利用。提出了全局时隙转让算法（Whole Timeslot Transfer algorithm,WTT-ALG）,地面节点根据时隙评估过程后生成的节点时隙请求数,按需协调全局空闲时隙的转让,重新分配节点业务时隙数。利用OPNET平台进行仿真建模,并与HFTP协议和TDMA协议作了对比分析。仿真结果表明,WTT-TDMA相比HFTP协议和TDMA协议,在消息投递率、平均时延和吞吐量方面具有更优异的性能。     

无线传感器网络流量自适应混合MAC协议

提出一种应用于无线传感器网络的流量自适应混合介质访问控制协议(THMAC)。结合TDMA与CSMA的优势,通过预测机制跟踪网络负载和冲突变化情况,在不同负载下选择合适的信道访问方式,实现CSMA与TDMA的自适应混合,在降低数据冲突概率的同时尽力保持较高的信道利用率。仿真结果表明,THMAC在多竞争节点的情况下,能够有效降低数据冲突率,维持较高的吞吐率。     

太赫兹无线个域网高时隙利用率跨PAN数据传输协议

针对现有跨PAN数据传输机制存在的业务量分布不均衡造成的时隙浪费、协调超帧开始时刻不明确、超帧统一机制所需控制开销较大等问题,提出了一种高时隙利用率太赫兹无线个域网跨PAN数据传输机制HTSU-PAN（high time slot utilization cross PAN data transmission protocol for Terahertz wireless personal area network）。该协议通过采用隐式TDMA时隙分配、基于无beacon的空闲时段启用以及基于网桥节点超帧统一这三种新机制,有效提高时隙利用率,降低数据传输时延从而提升网络吞吐量。     

短波地空网中一种动态TDMA协议设计与仿真*

针对传统TDMA网络节点间业务量不均匀时,会造成信道资源严重浪费的问题,设计了一种基于邻居时隙调动的短波地空网动态TDMA协议(TDMA protocol based on neighbour timeslot remove,NTR-TDMA),以可靠性较高的地面节点作为控制中心,实现时隙分配可控下的动态利用。提出了邻居时隙调动算法(neighbour timeslot remove algorithm,NTR-ALG),地面节点根据时隙估计过程后生成的节点时隙请求数,调动相邻业务时隙节点间的空闲时隙,重新划分节点业务时隙界限。利用OPNET平台进行性能仿真,并与HFTP协议和TDMA协议作了对比分析。仿真结果表明,NTR-TDMA相比HFTP协议和TDMA协议,在消息投递率、平均时延和吞吐量方面具有更优异的性能。     

Hybrid TDMA with heuristic traffic shaping: An efficient bandwidth allocation approach for heavy loaded LANs

Hybrid TDMA (Time Division Multiple Access) with heuristic traffic shaping (HyTDMA/HTS) is a new collisionless MAC protocol for efficiently managing the traffic of a heavy loaded broadcast LAN. The protocol employs techniques that enable it to perform better than both fixed assignment protocols like TDMA as well as dynamic bandwidth allocation protocols like LTDMA. HyTDMA/HTS can smoothly operate in diverse traffic environments of very high loads and bursty traffic, and it can still maintain maximum shared medium utilization while maintaining low packet delay times. Built into the protocol is also a simple yet effective heuristic mechanism that regulates the traffic of hosts flooding the network with an excessive number of packets larger than the average.     

基于无线传感器网络的混合MAC协议

结合载波侦听多路访问(CSMA)与时分多址(TDMA)的工作方式,提出一种基于无线传感器网络的混合介质访问控制(MAC)协议。引入快速冲突解决算法,对CSMA模式下的SMAC协议进行改进,使其争用窗口可以随着网络流量变化而动态改变,从而完成CSMA模式与TDMA模式的平滑切换。OMNeT++平台上的仿真结果表明,该协议能提高信道利用率,延长网络生命周期。     

TDMA网络的时隙同步技术

TDMA(时分多址接入)协议是利用时间的正交性实现信道共享,网内各个站点按照时隙方式工作,不存在发生碰撞和相互竞争问题。TDMA网络是一种同步网络。必须有统一的时间基准,各站点的时隙必须与时间基准同步。因此,时隙同步技术是TDMA网络协议的关键技术。     

水声传感器网络中基于改进时分多址技术的MAC协议

海洋信道信号传输条件恶劣,水声传感器网络(UASN)的媒体访问控制协议（MAC）要能可靠且有效的工作面临极大的挑战。针对水下分组转发高传输延时和延时的起伏特性,提出了一个利用改进时分多址技术的媒体访问控制协议(W-MAC)。W-MAC通过简化的信号传输同步过程,利用“延缓时间”作为节点的实际数据传送时间,采用具有睡眠策略的监测时间来避免数据碰撞等一系列措施,使W-MAC协议在适应复杂的水下信号传送环境的同时,把能量开销限制在一个合理的水平。仿真实验表明,在水声信道条件下该协议可有效地改善网络性能。     

Enhanced MAC protocol to support multimedia traffic in cognitive wireless mesh networks

With the advanced physical layer techniques such as multiple-input and multiple-output (MIMO) and orthogonal frequency-division multiplexing (OFDM), transmission real-time 2D/3D contents and applications becomes more and more necessary in wireless networks for the amazing growing in demand of customers. However, the low efficiency of medium access control (MAC) protocol degrades the performance of real-time traffic greatly in multihop, wireless and mobile environment. Focusing on supporting real-time multimedia traffic in cognitive wireless mesh networks (WMNs), an enhanced MAC protocol is proposed. And the contribution of this paper is twofold: (1) An efficient carrier sense multiple access with collision avoidance (CSMA/CA) compatible time division multiple access (TDMA)-like MAC protocol called T-MAC is proposed, which aims to improve the system performance by allocating more channel access time in centralized manner and decreasing overhead. (2) An optimal adaptive scheduling scheme is proposed to support real-time multimedia applications and guarantee QoS for different priority traffic, which aims to find the optimized schedule among all possible sequences of concurrent transmissions by minimizing the occupied resources. Detailed simulation results and comparison with IEEE 802.11e MAC scheme show that the proposed T-MAC can effectively improve quality of service (QoS) for multimedia traffic in terms of throughput, end-to-end delay and packet loss rate, which also manifests that T-MAC is an efficient multimedia applications transmission scheme for mobile terminals and MAPs in cognitive WMNs.     

基于DSA的无线传感器网络自适应MAC协议研究

针对工业监测用无线传感器网络高可靠和低功耗的要求,基于TDMA协议提出了一种动态时隙分配(DSA)的自适应介质访问控制(DSA-MAC)协议,通过估计链路质量动态调整节点的时隙长度,提高数据传输的可靠性。该协议中加入了基于接收信号强度指示(RSSI)的自适应功率调整机制,实现网络的低功耗要求。利用CC2530硬件平台实现DSA-MAC协议,并在工业现场进行测试,结果表明:该协议提高了数据传输率并降低了网络能耗,能够适应工业环境的应用需求。     

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。     

A Cross-Layer Approach to Multichannel MAC Protocol Design for Video Streaming Over Wireless Ad Hoc Networks

This paper presents a cross-layer design for a reliable video transmission over wireless ad hoc networks based on multichannel MAC protocol with TDMA. First, we conduct a study of the multichannel MAC protocol through Markov chain model. Based on this study, two novel cross-layer modules are adopted for the design of multichannel MAC protocol. First, we adopt maximum latency rate (MLR) as the channel quality metric. Unlike the traditional MAC design based on network allocation vector (NAV), MLR is implemented to provide differentiated traffic so that the channel with smaller MLR time is initiated for higher priority traffic. Second, we adopt two congestion-aware metrics, namely MAC utilization and queue length of MAC layer, to improve the congestion-aware routing protocols with AODV and DSR. These two novel modules allow the proposed MAC protocol design to achieve high performance video transmission over wireless ad hoc networks. Experimental results show that the proposed scheme outperforms the state-of-the-art schemes under multichannel environments in wireless ad hoc networks for as much as 3.6 dB in PSNR. Such significant performance enhancement confirms that the cross-layer approach is very effective for multichannel MAC protocol design.     

流量自适应的无线传感器网络簇内通信算法*

提出了一种流量自适应的无线传感器网络簇内通信算法。该算法根据各传感器节点所需传送的数据量来给各节点分配长度不等的时隙,使其能在所分配的时隙内有效地传送完所有的数据,减少节点空闲时和节点从睡眠到活跃状态来回切换时所消耗的能量。不同长度的时隙构成了不同长度的帧,整个簇生存期由不同长度的帧构成。仿真实验证明该算法相对于传统TDMA算法和BMA算法既节省了能量,又提高了信道利用率。     

Link-level traffic scheduling for providing predictive QoS in wireless multimedia networks

A set of centralized burst-level cell scheduling schemes, namely, First Come First Served with Frame Reservation (FCFS-FR), FCFR-FR+, Earliest Deadline First with Frame Reservation (EDF-FR), EDF-FR+, and Multitraffic Dynamic Reservation (MTDR), are investigated for transmission of multiservice traffic over time division multiple access (TDMA)/time division duplex (TDD) channels in wireless ATM (WATM) networks. In these schemes, the number of time slots allocated to a virtual circuit (VC) during a frame-time is changed dynamically depending on the traffic type, system traffic load, the time of arrival (TOA)/time of expiry (TOE) value of the data burst and data burst length. The performances of these schemes are evaluated by computer simulation for realistic voice, video and data traffic models and their quality-of-service (QoS) requirements in a wireless mobile multimedia network. Both the error-free and the correlated fading channel conditions are considered. Simulation results show that the EDF-FR+ and MTDR schemes outperform the other schemes and can provide high channel utilization with predictive QoS guarantee in a multiservice traffic environment even in the presence of bursty channel errors. The EDF-FR+ scheme is found to provide better cell multiplexing performance than the MTDR scheme, Such a scheme would be easy to implement and would also result in a power conservative TDMA/TDD medium access control (MAC) protocol for broadband wireless access. Burst-level cell scheduling schemes such as EDF-FR+ can be easily adapted as MAC protocols in the emerging differentiated services (DS) enhanced wireless Internet protocol (IP) networks.     

A Learning Automata-Based Cognitive Radio for Clustered Wireless Ad-Hoc Networks

In current wireless networks, the radio systems are regulated by a fixed spectrum assignment strategy. This policy partitions the whole radio spectrum into a fixed number of radio ranges, each exclusively assigned to a specific user. Such a spectrum assignment strategy leads to an undesirable condition under which some systems only use a small portion of the allocated spectrum while the others have very serious spectrum insufficiency. The learning automata-based cognitive radio which is proposed in this paper is a highly potential technology to address the spectrum scarcity challenges in wireless ad hoc networks. This paper proposes a learning automata-based dynamic frame length TDMA scheme for slot assignment in clustered wireless ad-hoc networks with unknown traffic parameters, where the intra-cluster communications are scheduled by a TDMA scheme, and a CDMA scheme is overlaid on the TDMA to handle an interference-free inter-cluster communication. In this method, each cluster-head is responsible for a collision-free slot assignment within the cluster and determines the input traffic parameters of its own cluster members. It then takes these traffic parameters into consideration for an optimal channel access scheduling in the cluster. The medium access control layer in each cluster is based on a time division multiple access (TDMA) scheme, in which each host is assigned a fraction of the TDMA frame proportional to its traffic load. The simulation experiments show the superiority of our proposed slot assignment algorithm over the existing methods in terms of the channel utilization, control overhead, and throughput, specifically, under bursty traffic conditions.     

交通监控中基于模糊聚类的无线传感网MAC协议

针对交通监控中突发数据实时性问题,提出一种基于模糊聚类的媒体访问控制（FC-MAC）协议。该协议采用时分多址（TDMA）和改进的载波监听多路访问冲突避免（CSMA/CA）交替工作的方式,既保证了普通周期数据的传递,又增强了突发数据的实时性。在CSMA/CA阶段,提出模糊聚类分析的方法,根据因素向量聚类簇内节点,使节点突发数据具有不同的优先级,优先级高的突发数据更早接入信道完成传输;同时,根据该协议的时隙分配策略,提出一种基于分层随机延迟的方法,减少同一时段内竞争接入Sink节点的簇头数量,降低簇头节点之间因退避而产生的数据延迟。仿真结果表明：FC-MAC在能量消耗上介于混合型Z-MAC协议与调度型S-LMAC协议之间;在突发数据平均时延减少的情况下,网络吞吐量比Z-MAC提高了11.2%,比S-LMAC提高了21.3%,并且对网络业务流量具有更好的适应性。     

一种采用时隙对准方式的TDMA自组网同步协议

通过对TDMA方式下的同步协议STS和TISS进行研究,提出一种基于时隙对准方式的TDMA自组网同步协议MFSS。该协议以工作周期为自组网节点之间同步的标准,在节点初入网时采用双向交互和时隙对准方法,消除了传输时延误差和初始时间偏差,从而实现了快速初始同步;随后通过监测过程保证了节点之间产生的时钟漂移误差可自适应控制,同时减小了重新同步带来的开销。仿真结果证明,相比于STS协议和TISS协议,MFSS协议在同步收敛速度、同步精度以及同步开销上都取得了更好的性能。     

大型发电机在线监测的无线传感器网络时间同步设计

准确的时间同步是实现传感器网络自身协议运行、数据融合、TDMA调度、协同睡眠、定位等的基础.本文首先剖析了大型发电机在线监测的无线传感器网络的体系结构,在比较性地分析已有无线传感器网络时间同步协议、机制和算法的基础上,提出了一种适用于电气设备在线监测的时间同步方案,此方案结合外同步和内同步,在进行同步的过程当中采用单向广播同步和线性回归结合的方法,最后用仿真软件NS对算法进行了仿真对比,结果证明该算法适合于监测网络的要求.     

DSMAC:一种适于无线多媒体传感器网络的信道接入协议

多媒体传感器网络作为一种多媒体信息获取和处理方式,已在军事、民用及商业领域中显示出广阔的应用前景.信道接入协议能否高效地使用无线信道是保证无线多媒体传感器网络通信的最关键的因素之一.分析支持多媒体业务传输的无线传感器网络信道接入协议的要求,提出适于多媒体传感器网络提供区分服务的信道接入协议--DSMAC(different service medium access control),对实时业务与非实时业务实现了区分服务,在信道接入帧内的随机竞争期实现突发业务及时接入,支持突发多媒体业务实时传输,并提出了多信道簇间传输方式,避免了隐终端冲突.最后,对协议的服务区分、实时性、吞吐量以及能量有效性等性能进行了仿真实验,验证了其优良性能.