基于预约调度的无线传感器网络的MAC协议*

提出了一种基于预约调度的用于无线传感器网络的MAC协议--SSMAC.该协议采用分布式竞争接入和预约调度发送,提供高能量效率的信道接入和支持QoS业务的传输,较好地解决了隐藏终端和暴露终端问题.仿真结果表明SSMAC协议在保持节能的同时,在降低媒体接入时延、提高报文投递成功率和提供QoS保障上较TRAMA协议性能有很大的提高.     

A multi-layer experimental study of multimedia and QoS communication in wireless mesh networks

A significant issue in Mesh networks is to support multimedia transmissions while providing Quality of Service (QoS) guarantees to mobile users. For real-time multimedia streaming, unstable throughput or insufficient bandwidth will incur unexpected delay or jitter, and it remains difficult to provide comprehensive service guarantees for a wireless mesh environment. In this paper, we target the problem of providing multimedia QoS in wireless mesh networks. We design and implement a campus test-bed for supporting multimedia traffic in mobile wireless mesh networks, and investigate in detail some possible improvements on a number of layers to enable multimedia transmission over wireless networks with QoS support. We first study a number of improvements of some existing routing protocols to support multimedia transmissions. Some new admission control and rate control mechanisms are studied and their performance gains are verified in our experiments. In our new cross-layer adaptive rate control (CLARC) mechanism, we adaptively change the video encoder’s output bit rate based on the available network bandwidth to improve the quality of the received video. We also design a mobile gateway protocol to connect the MANET to Internet and a wireless LAN management protocol to automatically manage WLAN to provide some QoS.     

一种QoS保证的WMSNs实时路由协议

为了满足无线多媒体传感器网络(WMSNs)对数据的实时性要求,本文提出了一种QoS保证的WMSNs实时路由协议(WMSNRR).该协议在路由选择时,充分考虑两跳节点的转播速率及剩余能量等信息.同时,还采用了一种基于缓存队列长度和节点收发数据率的控制方法,区分业务进行拥塞控制.仿真结果表明,在节点非均匀分布的情况下,该协...     

多个无线传感器网络中节能MAC协议设计

在无线传感器网络中,媒体访问控制(MAC)层协议影响着整个网络的性能。根据无线传感器网络对节点能耗和时延的要求,本文提出了一种基于跨层设计的节能MAC协议。利用物理层、MAC层和路由层之间的信息交互,在保证可靠通信的基础上,实现在一个监听/睡眠周期内数据多跳传输,缩短数据传输时延,并且有效控制网络数据传输的冗余度,降低冗余节点能量消耗。性能分析和仿真结果表明,节能MAC协议能够有效地降低网络时延并且减少节点能耗。     

基于竞争允许TDMA的无线传感器MAC层协议

无线传感器网络在许多重要领域有着广泛的应用，而传感网的媒体访问控制子层(MAC)协议对传感器网络的运行和性能具有重要影响。该文概述了目前存在的传感网MAC协议的设计思想，在SMAC协议的基础上，将TDMA和CSMA两种思想结合起来并与SMAC协议同步机制相统一，提出了一个新的基于竞争允许TDMA的无线传感器网络MAC协议。模拟结果显示，与SMAC协议相比，该协议在数据包延迟、能量消耗及数据包的接收率等性能上有很大提高。     

一种基于簇的无线传感器网MAC协议

MAC协议对无线传感网络的运行和性能具有重要的影响。为此,分析了基于簇的无线传感器网络的MAC协议,针对它们存在的缺陷,提出了一种新的基于簇的MAC协议(C-MAC)。该协议能够根据簇成员节点数目和通信负载动态地改变TDMA帧的长度,减少节点的空闲侦听时间,提高信道的利用率,从而延长网络的生命周期。模拟结果显示,该协议在数据包延迟、能量消耗和数据包接收率等性能上有很大提高。     

A new MAC protocol design based on TDMA/FDD for QoS support in WATM networks

Several wireless networking solutions have been developed to provide different types of services for various end user applications. Currently, wireless networking infrastructures are not suitable for multimedia applications each requiring a different QoS support with various traffic parameters. Due to the success of ATM technology in the wired network, WATM concept and related researches are of importance in the information technology area. Main objective of WATM, which promises seamless transmission of different traffics such as voice, data and video over wireless medium, is to implement high bit rate and QoS guaranteed data transfer, already well achieved by ATM technology over wired medium. To support QoS guaranteed data transfer over error-prone and low bandwidth wireless medium, an effective MAC protocol must be designed and utilized. In this paper, a new TDMA/FDD based MAC protocol, maintaining QoS requirements of real-time wireless multimedia applications, is proposed. The main contribution of this study is the new guarantee-based scheduling algorithm used in the proposed MAC to support required level of QoS guarantee for all multimedia traffic types in wireless medium. Computer modeling and simulation of the new approach providing CBR, VBR, ABR and UBR ATM services are realized using OPNET Modeler. Simulation results are also presented together with comparisons those of a WATM counterpart which uses PRMA/DA MAC protocol.     

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.     

Providing MAC QoS for multimedia traffic in 802.11e based multi-hop ad hoc wireless networks

Ad hoc wireless networks with their widespread deployment, now need to support applications that generate multimedia and real-time traffic. Video, audio, real-time voice over IP, and other multimedia applications require the network to provide guarantees on the Quality of Service (QoS) of the connection. The 802.11e Medium Access Control (MAC) protocol was proposed with the aim of providing QoS support at the MAC layer. The 802.11e performs well in wireless LANs due to the presence of Access Points (APs), but in ad hoc networks, especially multi-hop ones, it is still incapable of supporting multimedia traffic.One of the most important QoS parameters for multimedia and real-time traffic is delay. Our primary goal is to reduce the end-to-end delay, thereby improving the Packet Delivery Ratio of multimedia traffic, that is, the proportion of packets that reach the destination within the deadline, in 802.11e based multi-hop ad hoc wireless networks.Our contribution is threefold: first we propose dynamic ReAllocative Priority (ReAP) scheme, wherein the priorities of packets in the MAC queues are not fixed, but keep changing dynamically. We use the laxity and the hop length information to decide the priority of the packet. ReAP improves the PDR by over 28% in comparison with 802.11e, especially under heavy loads. Second, we introduce Adaptive-TXOP (A-TXOP), where transmission opportunity (TXOP) is the time interval during which a node has the right to initiate transmissions. This scheme reduces the delay of video traffic by reducing the number of channel accesses required to transmit large video frames. It involves modifying the TXOP interval dynamically based on the packets in the queue, so that fragments of the same packet are sent in the same TXOP interval. A-TXOP is implemented over ReAP to further improve the performance of video traffic. ReAP with A-TXOP helps in reducing the delay of video traffic by over 27% and further improves the quality of video in comparison with ReAP without A-TXOP. Finally, we have TXOP-sharing, which is aimed at reducing the delay of voice traffic. It involves using the TXOP to transmit to multiple receivers, in order to utilize the TXOP interval fully. It reduces the number of contentions to the channel and thereby reduces the delay of voice traffic by over 14%. A-TXOP is implemented over ReAP to further improve the performance of voice traffic. The three schemes (ReAP, A-TXOP, and TXOP-sharing) work together to improve the performance of multimedia traffic in 802.11e based multi-hop ad hoc wireless networks.     

支持多媒体业务的新型无线多跳网络MAC协议*

提出了一种单信道无线多跳网络同步媒体接入控制协议—M-TDMA。基于信道预约,协议采用分类调度机制以满足多媒体业务中各类业务的服务质量需求。协议采用信道使用列表（CUL）、预约控制时隙、划分竞争期和非竞争期等措施维护预约信道,降低分组冲突率,提高信道使用率。分析结果表明,协议在保证分组传输可靠性的同时,传输时延较低,能够较好地支持多媒体业务的服务质量需求。     

QS-Sift:一种基于服务质量和空间相关性的无线传感器网络MAC协议

在大规模、稠密无线传感器网络中传输的数据大都具有高度的空间相关性．近年来，国内外学者提出通过在网络中筛选出一部分节点来发送数据以降低能量开销．本文在网络节点的筛选策略方面开展研究，基于Vuran等人提出的理论模型比较分析了三种节点筛选策略．数值实验结果表明传输低质量的监测数据意义不大，因为它们几乎不能降低甚至反而会增加在数据汇集端的重建失真（QoS）．基于此结论，本文提出了一种新型的分布式、能量高效MAC协议-QS-Sift，该协议赋予监测数据质量高的节点在接入信道时的高优先权，并抑制低质量监测数据的传输．以此进一步降低需要发送监测数据的节点数量，从而降低网赂能耗．模拟实验结果表明QS-Sift能够以较低的网络能耗、传输时延提供更好的QoS．     

无线传感器网络MAC协议的性能改进研究

在无线传感器网络中,MAC协议决定着网络的信道分配,对网络的性能有很重要的影响。目前已研究出多种S-MAC协议,其中S-MAC协议是一种典型的无线传感器网络MAC协议,但此协议存在一定缺陷,无法更好地适应传感器网Jj络多变的特点。针对该问题,在S-MAC协议的基础上,结合了自适应退避窗口和根据节点队列长度预测流量的思想,提出了一种新的协议-Q-MAC协议,并达到了较为理想的预测效果。经NS2仿真验证,此协议在平均延迟、吞吐量、能量消耗方面较S-MAC协议有了显著提高。     

DLD-MAC:一种区分服务的低时延传感器网络MAC协议

针对现有无线传感器网络MAC协议不能提供区分服务和传输时延较大的问题,在经典多跳传输协议DW-MAC的基础上,提出了一种具有区分服务功能的低时延MAC协议—DLD-MAC(Diffserv-based Low-Delay MAC)。其基本思路是让高优先级数据选择更小的竞争窗口,以降低时延和能耗。Markov建模分析表明,DLD-MAC能对不同优先级的业务流进行很好的服务区分,而且相较于传统的无线传感器网络MAC协议,其在时延性能上有显著优势,能更有效地保障服务质量。     

一种基于大规模网络分解和协调的WSNs MAC协议

针对树状拓扑的大规模传感器网络中存在的节点能量和传输效率问题,提出了一种基于大规模网络分解和协调的无线传感器网络(WSNs)MAC协议。该协议在路由信息的基础上对网络进行再一次分解,并采用了与之相适应的节点接入算法。实验结果表明:该协议总体能耗低、传达率高且具有一定的自适应性,同时网络时延并没有因为分层而增加。该协议对大规模无线传感器网络有良好的适用性。     

无线传感器网络中采用预约机制的MAC协议改进

提出一种基于信道预约的MAC协议CR-MAC(channel-reservation MAC),该协议是在S-MAC（sensor-MAC）协议基础上进行的改进。当有数据需要发送时,首先以基于竞争的方式发送和接收信道预约信息,实现信道的按需分配;信道预约完成后各节点按照预约好的时间片进行激活,以时分复用的方式传输数据。CR-MAC协议能够有效地减少节点的空闲侦听和串音干扰,从而降低能量消耗和传输延时。     

Wireless MediaNets: application-driven next-generation wireless IP networks

Thanks to the explosive creation of multimedia contents, the pervasive adoption of multimedia coding standards and the ubiquitous access of multimedia services, multimedia networking is everywhere in our daily lives. Unfortunately, the existing best effort IP network infrastructure, originally designed with little real-time QoS requirement, has started to suffer from performance degradation on emerging multimedia networking applications. This inadequacy problem is further deepened by the prevalence of last/first-mile wireless networking, such as Wi-Fi, mobile WiMAX, and many wireless sensors and ad-hoc networks. This can be evidenced by more and more fragmentation of application-driven IP-based networks, such as for power grid distribution, networked security surveillance, intelligent transportation communication, and many other sensor networks. To overcome the QoS challenges, the next generation wireless IP networks have to be architected in a top-down manner, i.e., application-driven layered protocol design. More specifically, based on the application media data, compression schemes are applied, the subsequent Network, MAC- and PHY-layered protocols need to be accordingly or jointly enhanced to reach the optimal performance. This is the fundamental concept behind the design of Wireless MediaNets. In this survey paper, I will address the QoS challenges specifically encountered in video over heterogeneous wireless broadband networks and address several application-driven Wireless MediaNet solutions based on effective cross-layer integration of APP and MAC/PHY layers. More specifically, the congestion control for achieving airtime fairness of video streaming to maximize the link adaptation performance of Wi-Fi, the minimum latency event-driven data exchange for distributed wireless ad-hoc sensor networks, and the opportunistic multicast of scalable video live streaming over mobile WiMAX.     

Ant-based routing for wireless multimedia sensor networks using multiple QoS metrics

In wireless sensor networks, most routing protocols consider energy savings as the main objective and assume data traffic with unconstrained delivery requirements to be a given. However, the introduction of video and imaging sensors unveils additional challenges. The transmission of video and imaging data requires both energy efficiency and QoS assurance (end-to-end delay and packet loss requirements), in order to ensure the efficient use of sensor resources as well as the integrity of the information collected. This paper presents a QoS routing model for Wireless Multimedia Sensor Networks (WMSN). Moreover, based on the traditional ant-based algorithm, an ant-based multi-QoS routing metric (AntSensNet) is proposed. The AntSensNet protocol builds a hierarchical structure on the network before choosing suitable paths to meet various QoS requirements from different kinds of traffic, thus maximizing network utilization, while improving its performance. In addition, AntSensNet is able to use a efficient multi-path video packet scheduling in order to get minimum video distortion transmission. Finally, extensive simulations are conducted to assess the effectiveness of this novel solution and a detailed discussion regarding the effects of different system parameters is provided. Compared to typical routing algorithms in sensor networks and the traditional ant-based algorithm, this new algorithm has better convergence and provides significantly better QoS for multiple types of services in wireless multimedia sensor networks.     

一种基于空间相关性的无线传感器网络MAC协议

在大规模无线传感器网络中传输的监测数据具有较大的空间相关性,数据的传输存在一定冗余.如何有效的减少冗余数据的传输来改善网络性能成为一个重要的研究课题.本文以环状空间相关性模型为基础,从节点的筛选策略研究入手,提出一种能量高效的无线传感器网络MAC协议SEMAC.SEMAC协议采用信号强度优先的节点选择算法和冲突避免机制...     

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。     

Ant based Pareto optimal solution for QoS aware energy efficient multicast in wireless networks

Most of the group communication technologies support real-time multimedia applications such as video conferencing and distributed gaming. These applications require quality-of-service (QoS) aware multicast routing protocol to deliver the same data stream to a predefined group of receivers. Since nodes in wireless networks are severely energy constrained due to finite battery source, hence it is of paramount importance that QoS aware multicast routing protocol be energy efficient. Transmission power control is one of the methods used to save energy. In this method, the nodes dynamically adjust the transmission power so that energy consumption in the tree is minimized. However, reduction in the transmission power increases the number of forwarding nodes in the multicast tree. This negatively impacts the QoS in terms of propagation delay, delay jitter, and packet loss etc. In wireless networks, there is a trade-off between the energy consumption and the QoS guarantees provided by the network. We unify these requirements into a multiobjective framework referred to as Energy Efficient QoS Multicast Routing (E²QoSMR). The goal is to simultaneously optimize the total power consumption and the QoS parameters in the multicast tree. We extend two algorithms based on metaphor of swarm intelligence for finding an energy efficient multicast tree satisfying the QoS guarantees. Extensive simulations have been conducted to validate the correctness and efficiency of the algorithms. The simulation result of the algorithms is compared with the nondominated sorting genetic algorithm, NSGA-III. The experimental results are consolidated by statistical analyses that demonstrate the ability of the algorithms to generate the Pareto optimal solution set.