无线传感器网络中一种动态节能的MAC协议

媒体访问控制(MAC)协议是无线传感器网络的关键协议之一,它对无线传感网络的运行和性能具有重要的影响.针对基于簇的TDMA机制存在问题,文中提出了一个动态节能的DE-MAC协议,该协议能够根据簇成员节点数目和通信负载动态地分配成员节点的时隙,减少节点的空闲侦听时间.仿真结果表明,DE-MAC协议能够有效地提高信道的利用率和网络能量有效性.     

无线传感器网络能量高效混合MAC算法

针对无线传感器网络MAC协议中存在的能耗问题,提出了能量高效的无线传感器网络混合MAC(EEH-MAC)算法,采用基于TDMA机制的时槽系数动态调整簇内节点的时槽大小来降低数据的传输时延;同时,对部分不需要数据传输的节点不分配时槽来减少能耗;按簇内节点剩余能量系数形成时槽分配顺序来减少状态转换的能耗;在簇头之间采用CSMA/CA机制的随机分配策略进行通信.仿真结果表明,EEH-MAC协议能有效减少能耗并延长网络生命周期.     

分簇无线传感器网络动态时隙分配MAC协议

为降低大规模无线传感器网络的平均能耗,提出了一种基于动态分配的调度型无线传感器网络MAC协议（SDC-MAC）。该协议簇间使用FDMA方式分配无线信道,簇内通过TDMA方式给各个节点分配可变长的时隙。随着簇结构的变化,簇头通过时隙分配通知,对簇内节点的时隙分配进行动态调整,簇成员节点则根据控制信息进行休眠和唤醒。仿真结果显示,该算法有效地降低了网络的平均能耗,当网络流量高时还可降低平均数据包时延。     

混合多址接入的无线传感器网络设计及实现

针对实际应用中无线传感器网络多区域分布、任务多元化的特点,为解决簇间通信的相互干扰,提出一种改进的FD-MA/TDMA混合机制的无线传感器网络.簇间采用FDMA避免干扰,簇内节点采用TDMA实现睡眠调度.此外,在TDMA机制中分配监测时隙,如有突发情况,簇内节点可通过CSMA竞争与簇头节点实现通信,以此增加上报的公平性.对系统进行了工程实现验证,测试证明达到预期效果.     

一种基于预约的无线传感器网络MAC协议

无线传感器网络要求的能量高效,低延时,使得MAC协议的设计充满挑战。近来已经提出了很多基于簇的MAC协议,为减少冲突在簇内部采用TDMA方式来协调簇内各个节点的传输。提出了一种在采用簇结构的基础上,使用预约方式来发送数据的R-MAC（Reservation-MAC）协议。当争用节点少的时候,采用随机争用方式来预约数据的发送;在争用节点多的时候,采用时隙争用方式来预约数据的发送。分析表明,R-MAC能够有效地降低能耗和减少延迟。     

一种混合多址接入的无线传感器网络设计及实现

针对实际应用中无线传感器网络多区域分布、任务多元化的特点,为解决簇间通信的相互干扰,提出一种改进的FDMA/TDMA混合机制的无线传感器网络。簇间采用FDMA避免干扰,簇内节点采用TDMA实现睡眠调度。此外,在TDMA机制中分配监测时隙,如有突发情况,簇内节点可通过CSMA竞争与簇头节点实现通信,以此增加上报的公平性。对网络系统进行了工程实现验证,测试证明达到预期效果。     

DEAMC:一种分布的,节能的,自适应的动态的分簇无线传感器网络协议

分簇结构的无线传感器网络可以更容易的进行数据融合,可以减少网络能量消耗,增加网络的健壮性,因此分簇算法被广泛的用在无线传感器网络中.但现存的算法不能满足网络拓扑变化较大、较频繁的网络.针对移动性较大的无线传感器网络,提出了DEAMC,一种分布的、节能的、自适应的、动态的分簇协议.根据DEAMC,剩余能量越多,成为簇头的可能性越大,且簇头均匀分布.DEAMC用是一种TDMA协议,利用TDMA可以减少能量消耗,延长网络的寿命.DEAMC是一种FDMA协议,利用FDMA可以避免信号碰撞.     

一种基于分簇的无线传感器网络MAC协议

本文提出了一种基于分簇结构的无线传感器网络MAC协议.在基于层次式路由协议的分簇网络结构中,通过综合基于竞争和基于时分复用协议的优缺点,将时间划分为交替的随机访问和调度访问两个阶段,在随机访问阶段簇内节点采用CSMA/CA实现无线信道共享.在调度访问阶段,节点根据簇首分配的时隙实现数据无冲突通信.在簇与簇之间采用FDMA避免信道干扰实现网络的扩展.分析和仿真结果表明本协议在能量效率、时间同步和网络扩展上都有所改进.     

无线传感器网络MAC层协议的分析比较

无线传感器网络是一种由大量廉价微型传感器节点组成,并通过无线通信方式形成的多跳自组织网络,可用于对其部署区域的某些物理量进行智能监测。由于传感器节点数目较大,MAC协议是保证无线传感器网络高效通信的关键网络协议之一。另一方面,因为传感器节点受到电源能量有限、通信能力有限、计算和存储能力有限等现实条件的限制,传感器网络中的MAC协议又具有一些独特之处。对无线传感器网络MAC协议的研究现状进行较全面的考察,分析比较其中的几种典型MAC协议,并提出了该领域的发展趋势和未来工作的一些思路。     

混合型分簇MAC协议在无线传感器网络中的实现

针对当前MAC协议的研究大多停留在软件仿真阶段的问题,设计一种适用于两层无线传感器网络的混合型MAC协议,并利用节点实现硬件仿真。簇内采用门限服务方式,各节点接到唤醒通知后,依据簇头发布的轮询列表,按照顺序发送数据,实现无冲突通信。簇间采用随机多址接入,各簇头随机争用信道,向汇聚节点发送数据。基于Z-Stack进行协议设计,最后利用CC2530节点搭建无线传感器网络,实现该协议。实验结果表明,使用该协议的系统能够正确运行,吞吐量和平均时延、平均排队队长的实验值与理论值一致。     

A cluster-based power-efficient MAC scheme for event-driven sensing applications

In developing an architecture for wireless sensor networks (WSNs) that is extensible to hundreds of thousands of heterogeneous nodes, fundamental advances in energy efficient communication protocols must occur. In this paper, we first propose an energy-efficient and robust intra-cluster communication bit-map assisted (BMA) MAC protocol for large-scale cluster-based WSNs and then derive energy models for BMA, conventional TDMA, and energy efficient TDMA (E-TDMA) using two different approaches. We use simulation to validate these analytical models. BMA is intended for event-driven sensing applications, that is, sensor nodes forward data to the cluster head only if significant events are observed. It has low complexity and utilizes a dynamic scheduling scheme. Clustering is a promising distributing technique used in large-scale WSNs, and when combined with an appropriate MAC scheme, high energy efficiency can be achieved. The results indicate that BMA can improve the performance of wireless sensor networks by reducing energy expenditure and packet latency. The performance of BMA as an intra-cluster MAC scheme relative to E-TDMA depends on the sensor node traffic offer load and several other key system parameters. For most sensor-based applications, the values of these parameters can be constrained such that BMA provides enhanced performance.     

Minimizing inter-cluster interference by self-reorganizing MAC allocation in sensor networks

This paper presents a Self-Reorganizing Slot Allocation (SRSA) mechanism for TDMA based Medium Access Control (MAC) protocols in wireless sensor networks. With TDMA, a node can achieve significant energy savings by remaining active only during allocated slots for transmissions and receptions. In multi-cluster networks, it is often necessary for nodes to use either CDMA or FDMA for preventing interference across neighbor clusters. The goal of this paper is to provide an alternative design that can reduce inter-cluster TDMA interference without having to use spectrum expensive CDMA or FDMA. The primary contribution of this paper is to demonstrate that with adaptive slot allocation, it is possible to reduce such interference under low loading conditions, which is often the case for sensor networks with monitoring applications. The second contribution is to design a feedback based adaptive allocation protocol that can significantly reduce those interferences without relying on any global synchronization mechanisms. We present the design of SRSA and provide a simulation based characterization of the protocol in comparison with TDMA-over-CDMA, TDMA with random slot allocation and CSMA MAC protocols. The results indicate that with moderate cluster overlapping and low traffic loading, SRSA can significantly reduce inter-cluster TDMA interference while delivering TDMA-over-CDMA like energy efficiency, at the cost of higher delivery latency. Assuming its low complexity and narrow-band operation, SRSA can be an ideal sensor MAC protocol for applications that can tolerate relatively larger delivery latency but not frequent packet drops. This work was partially supported by a grant from National Science Foundation (SCI-0438271) Tao Wu received B.E. degree in automatic control and M.S. degree in pattern recognition from University of Electronic Science and Technology of China, Chengdu, China in 2001 and 2004 respectively. He is currently a Ph.D. student in electrical and computer engineering at Michigan State University. His research interests include wireless sensor networks and distributed computing. Subir Biswas is an Associate Professor and the director of Networked Embedded and Wireless Systems laboratory at the Electrical and Computer Engineering Department of Michigan State University. Subir received his Ph.D. from University of Cambridge and he held various research positions in NEC Research Institute, Princeton, AT&T Laboratories, Cambridge, and Tellium Optical Systems, NJ. He has published over 50 peer-reviewed articles in the area of wireless network protocols, and a co-inventor of 4 U.S. patents. Subir’s current research interests include the broad area of wireless data networking, low-power network protocols, application-specific sensor networks and wireless network security. He is a senior member of IEEE and a fellow of Cambridge Philosophical Society.     

CCA-Embedded TDMA enabling acyclic traffic in industrial wireless sensor networks

A growing trend in the automation industry is to use wireless technologies to reduce cable costs and deployment time, unlock stranded information in deployed devices and enable wireless control applications. The WirelessHART protocol is the first open and interoperable industrial wireless sensor network standard, which proposes a combination of time division multiple access (TDMA) and channel hopping as a medium access control (MAC) protocol. TDMA is a schedule-based protocol, which is suitable for predictable cyclic traffic. However, for burst acyclic traffic, TDMA degenerates into an inefficient slotted ALOHA. In this article, we propose a complementary mechanism to TDMA, CCA-Embedded TDMA, which can be applied to improve the transmission efficiency and system stability of TDMA-based systems such as the WirelessHART protocol. A Markov model is proposed to evaluate the efficiency of system throughput and expected delay of CCA-Embedded TDMA. Furthermore, we show by analytical and simulation results that our proposed CCA-Embedded TDMA scheme can increase the throughput by 100% and reduce the expected delay by 75% for a common scenario. We also implement CCA-Embedded TDMA into an embedded system as a part of the WirelessHART MAC protocol. The experimental results verify the efficiency of CCA-Embedded TDMA and its backward compatibility with the WirelessHART protocol.     

Cluster Based Routing Protocol for Mobile Nodes in Wireless Sensor Network

Mobility of sensor nodes in wireless sensor network (WSN) has posed new challenges particularly in packet delivery ratio and energy consumption. Some real applications impose combined environments of fixed and mobile sensor nodes in the same network, while others demand a complete mobile sensors environment. Packet loss that occurs due to mobility of the sensor nodes is one of the main challenges which comes in parallel with energy consumption. In this paper, we use cross layer design between medium access control (MAC) and network layers to overcome these challenges. Thus, a cluster based routing protocol for mobile sensor nodes (CBR-Mobile) is proposed. The CBR-Mobile is mobility and traffic adaptive protocol. The timeslots assigned to the mobile sensor nodes that had moved out of the cluster or have not data to send will be reassigned to incoming sensor nodes within the cluster region. The protocol introduces two simple databases to achieve the mobility and traffic adaptively. The proposed protocol sends data to cluster heads in an efficient manner based on received signal strength. In CBR-Mobile protocol, cluster based routing collaborates with hybrid MAC protocol to support mobility of sensor nodes. Schedule timeslots are used to send the data message while the contention timeslots are used to send join registration messages. The performance of proposed CBR-Mobile protocol is evaluated using MATLAB and was observed that the proposed protocol improves the packet delivery ratio, energy consumption, delay and fairness in mobility environment compared to LEACH-Mobile and AODV protocols.     

ETPS-MAC: Energy Traffic Priority Scheduling-based QoS-aware MAC protocol for hierarchical WSNs

The evolution of the wireless sensor network (WSN) in recent years has reached its greatest heights and applications are increasing day by day, one such application is Smart Monitoring Systems (SMSs) which is in vision of implementation in every urban and rural areas. The implementation of WSN architecture in SMS needs an intelligent scheduling mechanism that efficiently handles the dynamic traffic load without sacrificing the energy efficiency of network. This paper presents a centralized TDMA scheduling based medium access control (MAC) protocol, called Energy Traffic Priority Scheduling MAC (ETPS-MAC) that accommodates variable traffic load while maintaining Quality-of-Service (QoS) assurance in hierarchical WSNs. The ETPS-MAC protocol employs priority scheduling algorithm which considers two factors for assigning priority, the energy factor and the traffic load factor to avoid packet buffering and maintains minimum data packet delay in case of high traffic load. Moreover, a novel rank-based clustering mechanism in FPS-QMAC protocol prolongs the network lifetime by minimizing the distance between the cluster head (CH) and the base station (BS). Both analytical and simulation models demonstrate the superiority of the ETPS-MAC protocol in terms of energy consumption, transmission delay, data throughput and message complexity when compared with the existing TDMA based MAC protocols.     

The problem of medium access control in wireless sensor networks

In this article we revisit the problem of scheduled access through a detailed foray into the questions of energy consumption and throughput for MAC protocols in wireless sensor networks. We consider a static network model that rules out simultaneous transmission and reception by any sensor node and consequently requires partitioning of nodes into disjoint sets of transmitters and receivers at any time instant. Under the assumption of circular transmission (reception) ranges with sharp boundaries, a greedy receiver activation heuristic is developed relying on the network connectivity map to determine distinct receiver groups to be activated within disjoint time intervals. To conserve limited energy resources in sensor networks, the time allocation to each receiver group is based on the residual battery energy available at the respective transmitters. Upon activating each receiver group separately, the additional time-division mechanism of group TDMA is imposed to schedule transmissions interfering at the non-intended destinations within separate fractions of time in order to preserve the reliable feedback information. The two-layered time-division structure of receiver activation and group TDMA algorithms offers distributed and polynomial-time solutions (as required by autonomous sensor networks) to the problems of link scheduling as well as energy and throughput-efficient resource allocation in wireless access. The associated synchronization and overhead issues are not considered in this article.     

A schedule‐based medium access control protocol for mobile wireless sensor networks

Recent advances in body area network technologies such as radio frequency identification and ham radio, to name a few, have introduced a huge gap between the use of current wireless sensor network technologies and specific needs of some important wireless sensor network applications such as medical care, disaster relief, or emergency preparedness and response. In these types of applications, the mobility of nodes can occur, leading to the challenge of mobility handling. In this paper, we address this challenge by prioritizing transmissions of mobile nodes over static nodes. This is achieved by using shorter contention windows in reservation slots for mobile nodes (the so‐called backoff technique) combined with a novel hybrid medium access control (MAC) protocol (the so‐called versatile MAC). The proposed protocol advocates channel reuse for bandwidth efficiency and management purpose. Through extensive simulations, our protocol is compared with other MAC alternatives such as time division multiple access and IEEE 802.11 with request to send/clear to send exchange, chosen as benchmarks. The performance metrics used are bandwidth utilization, fairness of medium access, and energy consumption. The superiority of versatile MAC against the studied benchmark protocols is established with respect to these metrics. Copyright © 2012 John Wiley & Sons, Ltd.