Toward In-Band Self-Organization in Energy-Efficient MAC Protocols for Sensor Networks

This paper presents a self-organizing medium access control (MAC) protocol framework for distributed sensor networks with arbitrary mesh topologies. The novelty of the proposed In-band self-organized MAC (ISOMAC) protocol lies in its in-band control mechanism for exchanging time-division multiple access (TDMA) slot information with distributed MAC scheduling. A fixed-length bitmap vector is used in each packet header for exchanging relative slot timing information across immediate and up to two-hop neighbors. It is shown that, by avoiding explicit timing information exchange, ISOMAC can work without networkwide time synchronization, which can be prohibitive for severely cost-constrained sensor nodes in very large networks. A slot-clustering effect, caused by in-band bitmap constraints, enables ISOMAC to offer better spatial channel reuse compared to traditional distributed TDMA protocols. ISOMAC employs a partial node wake-up and header-only transmission strategy to adjust energy expenditure based on the instantaneous nodal data rate. Both analytical and simulation models have been developed for characterizing the proposed protocol. Results demonstrate that, with in-band bitmap vectors of moderate length, ISOMAC converges reasonably quickly, that is, approximately within a four to eight TDMA frame duration. Also, if the bitmap header duration is restricted within 10 percent of packet duration, then the energy penalty of the in-band information is quite negligible. It is also shown that ISOMAC can be implemented in the presence of network time synchronization, although its performance without synchronization is just marginally worse than that with synchronization.     

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.     

一种高效可靠的无人机自组网多跳TDMA协议

设计无人机自组网媒体接入控制(Medium Access Control,MAC)协议时,需要考虑其控制开销和数据传输的可靠性。鉴于此,结合现有无线自组网多跳时分多址接入(Time Division Multiple Access,TDMA)协议和无人机自组网特点,提出了一种高效可靠的无人机自组网多跳TDMA协议。首先采用高效负载均衡的时隙请求信息上传机制,选择一个负载较小的节点转发节点时隙请求信息;然后根据相互通信的父节点删除重复节点的时隙请求信息,减少相同节点的时隙请求信息转发次数;最后通过实时更新节点时隙请求信息机制,提高节点时隙请求信息传输的可靠性。仿真结果表明,该协议在数据传输成功率、平均时延、控制开销方面优于现有协议,可较好地应用在无人机自组网中。     

采用TDMA和CSMA混合MAC协议的时隙调整算法

由于车联网(VANET)拓扑动态变化,车辆高速移动以及不同服务质量要求,制定媒体接入控制(MAC)协议面临巨大挑战。在控制信道间隔内采用基于TDMA和CSMA的混合接入协议是最有效的MAC协议之一。基于TDMA和CSMA的混合MAC协议(T-C-MAC)能够依据车辆环境调整TDMA帧长度,并能有效地传输非安全消息。为了提高T-C-MAC协议的性能,提出了一种基于三跳邻居信息的时隙调整(THSA) 算法。通过有效地调整车辆传输时隙,基于THSA的MAC（THSA-MAC）协议能够有效地实施广播服务,提高了安全消息传输率。实验数据表明,THSA-MAC有效地提高了安全消息传递率。     

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.     

无人机编队中的自主定位与动态TDMA协议应用

针对高速无人机编队,提出了一种无人机个体实现分布式自主定位的方法,为无人机编队的自主飞行控制提供位置参数。将改进后的固定TDMA协议应用于无人机编队的自主飞行控制中,增加了优先级以及竞争机制,实现了时隙的动态分配,为大业务量节点提供了负载均衡。仿真结果表明,动态TDMA协议能够显著提高分组发送的成功率、降低业务的端到端平均时延、满足无人机自主编队控制的需求。     

TC2-MAC:一种无线传感器网络自适应混合 MAC 协议

摘 要：提出了一种新的自适应混合MAC协议TC2-MAC。该协议采用了基于二叉树结构的时隙块分配策略和基于时隙约束的CSMA/CA竞争接入方式,能够为不同传感器节点或不同类型业务的差异性QoS需求提供良好支持,并能够通过灵活的信息调度机制改善信道接入公平性,提高网络效率。理论分析和仿真结果表明：与传统基于TDMA机制的MAC协议相比,TC2-MAC对网络业务流量及拓扑结构的变化均具有更好的自适应性。     

一种实时以太网介质访问控制协议的时延性能分析

本文提出一种新的基于持续竞争的实时以太网介质访问控制协议,该协议能够保证实时信号的发送有确定的最大时延.在新协议下,如果检测到冲突,实时节点并不像普通以太网节点一样停止传输,而是坚持发送竞争信号,利用信道冲突通知非实时节点或者低优先级实时节点停止传输,把信道留给高优先级的实时节点.而且该协议与普通以太网介质访问控制协议兼容,这样实时节点与普通以太网节点能共存于同一网络系统中互相通信.文中详细描述了新型以太网介质访问控制协议,分析了实时信号的发送时延,理论分析和仿真均证明了该协议是可行和有效的.     

一种双通道数据链端机的多址接入方法设计

多址接入协议提供了一种信道共享的调度机制,确保多个通信节点间公平、高效地共享相同的无线信道资源,决定了节点业务量和网络吞吐量,是数据链路层设计的重中之重。本文设计了一种利用双通道技术,将 SPMA 和 TDMA 多址接入技术有效的结合起来的方法,既保证网络运行的可靠性,又保证特殊业务对时延的要求,研究结果具有一定的工程应用价值。     

一种高效低时延的宽带电力线通信网多跳MAC协议

针对IEEE1901.1宽带电力线通信媒体接入控制(Medium Access Control,MAC)协议涉及到信标时隙利用不充分和控制开销过大等问题,提出了一种高效低时延的宽带电力线通信网多跳MAC协议(Efficient and Low Delay Multi-hop MAC,ELDM-MAC).采用基于节点层级号的信标时隙分配机制,根据邻居表和时隙分配信息计算能够提前进入到载波监听多路访问时隙(Carrier Sense Multiple Access,CSMA)的时间,减少了信标时隙的浪费,提高了信道利用率;同时采用基于拓扑信息的信标帧高效广播机制,删除不大于自身层级号的节点和大于且在两跳范围内的非子孙节点的时隙分配信息,降低了网络控制开销.仿真结果表明,ELDM-MAC协议在信道利用率、平均时延和控制开销等方面都优于IEEE1901.1 MAC协议,更适用于宽带电力线通信网络的实际应用场景.     

A novel QoS‐aware MAC protocol for voice services over IEEE 802.11‐based WLANs

With the pervasive growth in the popularity of IEEE 802.11‐based wireless local area networks (WLANs) worldwide, the demand to support delay‐sensitive services such as voice has increased very rapidly. This paper provides a comprehensive survey on the medium access control (MAC) architectures and quality of service (QoS) provisioning issues for WLANs. The major challenges in providing QoS to voice services through WLAN MAC protocols are outlined and the solution approaches proposed in the literature are reviewed. To this end, a novel QoS‐aware wireless MAC protocol, called hybrid contention‐free access (H‐CFA) protocol and a call admission control technique, called traffic stream admission control (TS‐AC) algorithm, are presented. The H‐CFA protocol is based on a novel idea that combines two contention‐free wireless medium access approaches, that is, round‐robin polling and time‐division multiple access (TDMA)‐like time slot assignment, and it increases the capacity of WLANs through efficient silence suppression. The TS‐AC algorithm ensures efficient admission control for consistent delay‐bound guarantees and further maximizes the capacity through exploiting the voice characteristic that it can tolerate some level of inconsecutive packet loss. The benefits of the proposed schemes are demonstrated in the simulations results. Copyright © 2008 John Wiley & Sons, Ltd.     

A Scalable CSMA and Self-Organizing TDMA MAC for IEEE 802.11 p/1609.x in VANETs

vehicular ad hoc networks (VANETs) have been a key topic for research community and industry alike. The wireless access in vehicular environment standard employs the IEEE 802.11p/1609.4 for the Medium Access Control (MAC) layer implementation for VANETs. However, the carrier sense multiple access (CSMA) based mechanism cannot provide reliable broadcast services, and the multi-channel operation defined in IEEE 1609.4 divides the available access time into fixed alternating control channel intervals (CCH) and service channel (SCH) intervals, which may lead to the low utilization of the scarce resources. In this paper, a novel multichannel MAC protocol called CS-TDMA considering the channel access scheduling and channel switching concurrently is proposed. The protocol combines CSMA with the time division multiple access (TDMA) to improve the broadcast performance in VANETs. Meanwhile, the dwelling ratio between CCH and SCH changes dynamically according to the traffic density, resulting in the improvement of resource utilization efficiency. Simulation results are presented to verify the effectiveness of our mechanism and comparisons are made with three existing MAC protocols, IEEE MAC, SOFT MAC and VeMAC. The simulation results demonstrate the superiority of CS-TDMA in the reduction of transmission delay and packet collision rate and improvement of network throughput.     

一种改进的数据链协作MAC协议

针对基于TDMA（时分多址）的数据链网络协议在恶劣环境下时延大、业务突发性强等缺点,提出了一种改进的数据链协作MAC协议。在原有的协议中引入协作通信的思想,节点根据协作机制,利用自身时隙进行协作转发,并进一步加入中继优先权因子改进协作机制,中继节点根据节点的繁忙程度与信道条件来判定是否协作传输。通过对网络时延性能的研究与仿真,结果表明,改进后的协作协议性能优于传统的数据链协议。     

Adaptive coordination function for IEEE 802.11 wireless LANs

Multiple access control (MAC) protocols play a significant role in wireless LANs. The IEEE 802.11 MAC protocol specifies two coordination functions that are Distributed Coordination Function (DCF) and Point Coordination Function (PCF). While both DCF and PCF are available in a wireless cell, we propose a novel access mechanism called Adaptive Coordination Function (ACF) to support various classes of traffic. The ACF superframe comprises two periods, one TDMA period designed for real-time traffic and followed by an adaptive period which adaptively employs DCF or PCF to support non-real-time traffic. In this paper, we apply the theory of M/G/1 queues to analyze the performance of adaptive period in terms of queuing delay, end-to-end delay, and saturation throughput. With our analytic model, DCF or PCF can be invoked appropriately according to the number of stations, packet arrival rate, packet payload size, and effective channel bit rate. Analytical results are derived for an extensive throughput and delay performance evaluation of both DCF and PCF.     

Location-Aware Two-Phase Coding Multi-Channel MAC Protocol (LA-TPCMMP) for MANETs

In classical code division multiple access (CDMA) based multi-channel medium access control (MAC) protocols for mobile ad hoc networks (MANETs), numerous exchanges of neighborhood information are required for code assignment such that nodes within a two-hop separation will adopt different transmission codes and therefore avoid the hidden terminal problem (HTP). However, such expensive communication overhead for code assignment is not desirable since it will cause an under-utilization of bandwidth, energy inefficiency and longer delays, which can significantly degrade the network performance. In this paper, a novel location-aware multi-channel MAC protocol is presented for a large-scale dense MANETs based on a scalable two-phase coding scheme, where the first-phase code is used for differentiating adjacent cells and the second-phase code is employed for distinguishing nodes in one specific cell. A node knows its first-phase code from its location information and requests its second-phase code from its cell leaden. This protocol eliminates the HTP during data transmission without the periodical exchange of neighborhood information. Furthermore, the mechanism of collision resolution in the control channel is described. The performance of the proposed protocol is analyzed in terms of the control overhead and delay. The theoretical results are confirmed by extensive simulations and it is shown that the new protocol significantly outperforms the classical CDMA-based multi-channel MAC protocols     

Contention-free distributed dynamic reservation MAC protocol withdeterministic scheduling (C-FD3R MAC) for wireless ATMnetworks

This paper proposes a novel MAC protocol for wireless ATM networks, which is characterized by a contention-free mechanism of the reservation request and a deterministic nature of mobile-assisted (distributed) uplink scheduling under a framework of the dynamic reservation TDMA, as discussed in the current standardization activities of ETSI Project BRAN (broadband radio access network) and the wireless ATM working group in the ATM Forum. The design objective of the proposed MAC protocol is to guarantee the real-time constraint of the real-time VBR (rt-VBR) traffic class while maximizing the multiplexing gain among all ATM traffic classes, especially with a fixed length frame. The proposed deterministic scheduling scheme for the rt-VBR traffic class lends itself to implementing the minimal configuration of control data units for reservation request as desired under the limited wireless resources. Simulation experiments using statistically multiplexed MPEG-2 video streams are performed for a 25 Mbits/s wireless ATM access link scenario. It has been shown that the proposed framework guarantees the delay constraint of rt-VBR sessions along with its cell loss rate significantly reduced, while improving the average delay performance of the nrt-VBR in the range of 10%-30% without compromising the channel utilization as compared to the DSA++ system     

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.     

无线局域网中的预约CDMA接入技术

在传统的无线ＭＡＣ接入协议（如ＡＬＯＨＡ,ＣＳＭＡ／ＣＡ,ＴＤＭＡ和ＣＤＭＡ）的基础上,重点探讨了基于码分多址的预约ＣＤＭＡ无线多址接入协议。该协议的在无线局域网接入时,无论在时间延迟还是吞吐量特性方面均比传统的无线接入协议有很大的改善。     

An improvement mechanism for heartbeat‐driven MAC synchronization in wireless body sensor network

This paper aims to improve the TDMA‐based Heartbeat‐Driven MAC (H‐MAC) protocol for WBAN. H‐MAC is designed to be used in star‐topology WBAN for time synchronization realization by using heartbeat rhythm information, instead of periodic synchronization beacons. H‐MAC therefore saves power of WBAN sensor nodes and reduces the negative effects of electromagnetic radiation on human health during the packet delivery process. To embed heartbeat rhythm information into different bio‐signals and check the peak values of wave forms can contribute to time synchronization for BSN. As the heart contracts via systole and relaxes via diastole, pulse is the number of times one's heart beats every minute and the number of pulses measured at different body parts is the same. However, blood vessels run over the whole human body and their distances away from the heart greatly vary in the same systole, leading to an imperceptible time difference and the synchronization problem. We propose to include the presently most mature method for time synchronization, Flooding Time Synchronization Protocol (FTSP), to deal with time differences.     

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.