无线传感器网络MAC层节能机制研究
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摘要
作为一项正在迅速发展的技术,无线传感器网络(WSNs, Wireless Sensor Networks)技术已经得到了广泛的应用并且成了信息技术领域的研究热点之一。在WSNs的设计中,通常要考虑其节能性、延迟性、服务质量、容错性和扩展性等因素。由于无线传感器节点硬件和能量的限制,与其网络生存期密切相关的节能性显得尤为重要。研究者们设计了各种节能机制来延长WSNs的生存期。其中就包含各种网络层以及介质访问控制(MAC)子层的节能机制。而本文的研究对象正是MAC子层的节能机制。主要研究工作如下：
首先,对WSNs的能耗和其中的节能机制进行研究。在WSNs中无线传感器节点的收发器消耗了WSNs的绝大部分能量。因此研究如何减少收发器的能耗对于节省整个WSNs的能量并延长网络生存期具有重要意义。本文对WSNs中网络层和MAC层的一些协议进行了细致的分析。通过对网络层协议的研究发现,网络层协议的节能措施主要有：减少单跳的传输距离,减少总的跳数,对传输中的数据进行数据聚集等。而通过对MAC层协议的研究发现,MAC层协议的节能措施主要有：降低数据发送冲突的几率,采取周期性唤醒／休眠的调度机制,采用前导抽样技术减少空闲监听等。
接着,对休眠／唤醒调度周期同步的S-MAC (Sensor MAC,S-MAC)和休眠／唤醒调度周期异步的DPS-MAC (Dual Preamble Sampling MAC,DPS-MAC)进行研究。在分析比较二者的节能性和延迟性之后发现,虽然S-MAC调度周期同步机制带来了额外的同步开销,但是该机制有效地避免了DPS-MAC中短频闪前导带来的能耗；而DPS-MAC检测信道的方式是利用RSSI的值对信道进行两次抽样(即所谓的双前导抽样)来判断信道是否被占用,因此DPS-MAC中又不存在S-MAC每个调度周期开始时监听信道的能耗。在比较二者的优点和缺点之后,本文展示了一种结合二者优点的本地同步机制。经分析发现,这种本地同步机制比前二者更加节能。
最后,基于网络仿真平台NS2 (Network Simulator 2),对带有本地同步机制的DPS-MAC和不带本地同步机制的DPS-MAC的节能性和延迟性进行评估。节能性是用节点的收发器处于发送和接收的时间在整个仿真期间所占的比例来评价的；延迟性则是用分组的6跳传输延迟来评价的。仿真结果显示,本地同步机制可使DPS-MAC更加节能,而且加入本地同步机制后DPS-MAC的延迟性能几乎保持不变。
As a rapidly developing technology, wireless sensor networks(WSNs, Wireless Sensor Networks) have been used widespread and become one of the research hot spots in the field of information technology. In the designing of WSNs, due to the limits of wireless sensor node's power and hardware device, energy efficiency should be considered except for latency, quality of service, robustness and flexibility. Researchers have proposed all kinds of power saving schemes including many power saving schemes in network layer and MAC sublayer. And the subject of this thesis is just power saving schemes in MAC sublayer. The main works of this thesis are described as follows:
First, the energy consumption sources and some power saving schemes in WSNs are investigated. After the investigation, it's clear that the radio transceivers almost consume whole of WSNs'power. Therefore researching how to reduce the energy consumption of transceivers is very important for saving power of WSNs and prolonging lifetimes of them. The thesis has carefully analyzed some protocol in the network layer and MAC sublayer of WSNs. After the research of network protocols, it's found that the main power saving schemes in network layer are shortening the distance of one hop, reducing the number hops, converging the data during transmission. And after the research of MAC protocols, it's found that the main power saving schemes in MAC layer are making the probability of conflicts during data transmission smaller, adopting periodical wakeup/sleep schedules, using preamble sampling technology to reduce idle listening.
Then, presented is the research on S-MAC(Sensor MAC, S-MAC) wakeup/sleep schedules of which are synchronous and DPS-MAC(Dual Preamble Sampling MAC,DPS-MAC) wakeup/sleep schedules of which are asynchronous. After analyzing and comparing the energy efficiency and latency of them, it's found that although the synchronous scheme of S-MAC's schedules brings extra power consumption for synchronization, the scheme can effectively avoid the power consumption of short strobed preamble. Moreover, DPS-MAC detects channels and determines whether channels are free using RSSI to sampling channels two times(that is dual preamble sampling), so the energy consumption at the beginning of every schedule in S-MAC is not exist in DPS-MAC. After comparing advantages and drawbacks of them, the thesis presents a schemes with local synchronization, which combines the advantage of both. After analyzing,it's found that this scheme with local synchronization is more energy efficient.
At last, based on network simulation platform NS2, the energy efficiency and latency of DPS-MAC with and without local synchronization are evaluated. The energy efficiency is evaluated by the ratio of the time when the transceivers are transmitting or receiving and time of the simulated progress. And the latency is evaluated by packets'average 6 hops delay.The results of the simulation show that local synchronization schemes could make DPS-MAC more energy efficient and keep nearly the same latency.
首先,对WSNs的能耗和其中的节能机制进行研究。在WSNs中无线传感器节点的收发器消耗了WSNs的绝大部分能量。因此研究如何减少收发器的能耗对于节省整个WSNs的能量并延长网络生存期具有重要意义。本文对WSNs中网络层和MAC层的一些协议进行了细致的分析。通过对网络层协议的研究发现,网络层协议的节能措施主要有：减少单跳的传输距离,减少总的跳数,对传输中的数据进行数据聚集等。而通过对MAC层协议的研究发现,MAC层协议的节能措施主要有：降低数据发送冲突的几率,采取周期性唤醒／休眠的调度机制,采用前导抽样技术减少空闲监听等。
接着,对休眠／唤醒调度周期同步的S-MAC (Sensor MAC,S-MAC)和休眠／唤醒调度周期异步的DPS-MAC (Dual Preamble Sampling MAC,DPS-MAC)进行研究。在分析比较二者的节能性和延迟性之后发现,虽然S-MAC调度周期同步机制带来了额外的同步开销,但是该机制有效地避免了DPS-MAC中短频闪前导带来的能耗；而DPS-MAC检测信道的方式是利用RSSI的值对信道进行两次抽样(即所谓的双前导抽样)来判断信道是否被占用,因此DPS-MAC中又不存在S-MAC每个调度周期开始时监听信道的能耗。在比较二者的优点和缺点之后,本文展示了一种结合二者优点的本地同步机制。经分析发现,这种本地同步机制比前二者更加节能。
最后,基于网络仿真平台NS2 (Network Simulator 2),对带有本地同步机制的DPS-MAC和不带本地同步机制的DPS-MAC的节能性和延迟性进行评估。节能性是用节点的收发器处于发送和接收的时间在整个仿真期间所占的比例来评价的；延迟性则是用分组的6跳传输延迟来评价的。仿真结果显示,本地同步机制可使DPS-MAC更加节能,而且加入本地同步机制后DPS-MAC的延迟性能几乎保持不变。
As a rapidly developing technology, wireless sensor networks(WSNs, Wireless Sensor Networks) have been used widespread and become one of the research hot spots in the field of information technology. In the designing of WSNs, due to the limits of wireless sensor node's power and hardware device, energy efficiency should be considered except for latency, quality of service, robustness and flexibility. Researchers have proposed all kinds of power saving schemes including many power saving schemes in network layer and MAC sublayer. And the subject of this thesis is just power saving schemes in MAC sublayer. The main works of this thesis are described as follows:
First, the energy consumption sources and some power saving schemes in WSNs are investigated. After the investigation, it's clear that the radio transceivers almost consume whole of WSNs'power. Therefore researching how to reduce the energy consumption of transceivers is very important for saving power of WSNs and prolonging lifetimes of them. The thesis has carefully analyzed some protocol in the network layer and MAC sublayer of WSNs. After the research of network protocols, it's found that the main power saving schemes in network layer are shortening the distance of one hop, reducing the number hops, converging the data during transmission. And after the research of MAC protocols, it's found that the main power saving schemes in MAC layer are making the probability of conflicts during data transmission smaller, adopting periodical wakeup/sleep schedules, using preamble sampling technology to reduce idle listening.
Then, presented is the research on S-MAC(Sensor MAC, S-MAC) wakeup/sleep schedules of which are synchronous and DPS-MAC(Dual Preamble Sampling MAC,DPS-MAC) wakeup/sleep schedules of which are asynchronous. After analyzing and comparing the energy efficiency and latency of them, it's found that although the synchronous scheme of S-MAC's schedules brings extra power consumption for synchronization, the scheme can effectively avoid the power consumption of short strobed preamble. Moreover, DPS-MAC detects channels and determines whether channels are free using RSSI to sampling channels two times(that is dual preamble sampling), so the energy consumption at the beginning of every schedule in S-MAC is not exist in DPS-MAC. After comparing advantages and drawbacks of them, the thesis presents a schemes with local synchronization, which combines the advantage of both. After analyzing,it's found that this scheme with local synchronization is more energy efficient.
At last, based on network simulation platform NS2, the energy efficiency and latency of DPS-MAC with and without local synchronization are evaluated. The energy efficiency is evaluated by the ratio of the time when the transceivers are transmitting or receiving and time of the simulated progress. And the latency is evaluated by packets'average 6 hops delay.The results of the simulation show that local synchronization schemes could make DPS-MAC more energy efficient and keep nearly the same latency.
引文
[1]Alan Mainwaring et al.. Wireless sensor networks for habitat monitoring [C]. WSNA'02, September 28,2002, Atlanta, Georgia, USA.
[2]Affan A. Syed, Wei Ye and John Heidemann. Comparison and evaluation of the T-Lohi MAC for underwater acoustic sensor networks [J]. IEEE Journal of Selected Areas in Communication,vol.26,no.12,pp.1731-1743,December 2008.
[3]付耀先.面向动态数据流量的无线传感网时频混合跨层协议研究[D].上海：中国科学院上海微系统与信息技术研究所,2008.
[4]杜军朝.无线传感器网络节能介质访问控制协议与可靠路由协议研究[D].西安：西安电子科技大学,2008.
[5]Joseph Polastre, Robert Szewczyk and Alan Mainwaring. Wireless Sensor Networks for HabitatMonitoring[EB/OL]. http://www.eecs.berkeley.edu/IPRO/Summary/Old.summarie s/03abstracts/chapter6.html,2010-05-06.
[6]Wei Ye,John Heidemann and Deborah Estrin. An Energy-efficient MAC protocol for wireless sensor networks[C]. Proceedings of the IEEE Infocom,pp.1567-1576.June 2002.
[7]Joseph Polastre,Jason Hill and David Culler.Versatile low power media access for wireless sensor networks[C].SenSys'04, November3-5,2004,Baltimore,Maryland, USA.
[8]Michael Buettner,Gary V. Yee,Eric Anderson and Richard Han. X-MAC:A short preamble MAC protocol for duty-cycled wireless sensor networks[C].SenSys'06, November 1-3,2006,Boulder,Colorado,USA.
[9]CENS. Lab-on-Chip aquatic microorganism analysis [EB/OL]. http://research.cens.ucla.edu/areas/2007/Sensors/default.htm, 2010-05-06.
[10]Stefon Shelton and Hongsoo Choi. Aluminum Nitride Ultrasonic Doppler VelocitySensor[EB/OL]. http://www-bsac.eecs.berkeley.edu/project/zoom.php? urlmyprojectID=BPN467&URLnode=2,2010-05-06.
[11]Winnie Louis Lee, Amitava Datta, and Rachel Cardell-Oliver. FlexiTP: Aflexible-schedule-based TDMA protocol for fault-tolerant and energy-efficient wireless sensor networks[J]. IEEE transactions on parallel and distributed systems, vol.19,no.6,June 2008.
[12]Inwhee Joe and Hanjong Ryu. A Patterned Preamble MAC Protocol for Wireless Sensor Networks[J].2007 IEEE.
[13]Antonio G. Ruzzelli, G.M.P O'Hare and M.J. O'Grady et al.. MERLIN: Cross-Layer Integration of MAC and Routing for Low Duty-Cycle Sensor Networks[J]. Elsevier Science,14 June 2007.
[14]Texas Instruments,CC2430 PRELIMINARY Data Sheet (rev.2.01) SWRS036E.
[15]金湘亮,旷章曲,刘志碧,等.低功耗CMOS视觉传感器新结构及其SOC实现[J].微电子学,2009,39(6)：782-785.
[16]van Dam T, Langendoen K. An adaptive energyefficient mac protocol for wireless sensor networks. In:Proc. of the 1st ACM Conf. on Embedded Networked Sensor Systems (SenSys). New York:ACM Press,2003.171-180.
[17]IEEE 802.15.4-2006, "Part 15.4:Wireless LAN MediumAccess Control (MAC) and Physical Layer (PHY) Specificationsfor Low-Rate Wireless Personal Area Networks(LR-WPANs)," 2006.
[18]C. C. Enz et al., "WiseNET:An Ultralow-Power Wireless Sensor Network Solution," IEEE Comp., vol.37, no.8,Aug.2004.
[19]Heping Wang, Xiaobo Zhang, Farid Nait-Abdesselam and Ashfaq Khokhar DPS-MAC:An Asynchronous MAC Protocol for Wireless Sensor Networks[C].HiPC 2007, LNCS 4873, pp.393-404,2007.
[20]]IEEE Standard for Wireless LAN Medium Aecess Control (MAC) and Physical Layer (PHY) Specifications,ISO/IEC8802-11:1999E,1999.
[21]Chipcon, "2.4GHz IEEE802.15.4/ZigBee-ready RF Transceiver datasheet (revl.2)," Chipcon AS, Oslo, Norway,2004.
[22]NS-2Wiki.ProjectNews[EB/OL]. http://nsnam.isi. edu/nsnam/index.php/Main_Pag e,2010/04/06.
[23]徐雷鸣,庞博,赵耀.NS与网络模拟[M].北京：人民邮电出版社,2003：5-6.
[24]柯志亨.使用NOAH (NO Ad-Hoc Routing Agent)无线网路静态路由[EB/OL]. http.//140.116.72.80/-smallko/ns2/noah_st.htm,2010-05-06.
[25]胡呈欣.一种适用于流量突发的无线传感器网络的MAC协议[D].武汉：武汉理工大学,2008.
[2]Affan A. Syed, Wei Ye and John Heidemann. Comparison and evaluation of the T-Lohi MAC for underwater acoustic sensor networks [J]. IEEE Journal of Selected Areas in Communication,vol.26,no.12,pp.1731-1743,December 2008.
[3]付耀先.面向动态数据流量的无线传感网时频混合跨层协议研究[D].上海：中国科学院上海微系统与信息技术研究所,2008.
[4]杜军朝.无线传感器网络节能介质访问控制协议与可靠路由协议研究[D].西安：西安电子科技大学,2008.
[5]Joseph Polastre, Robert Szewczyk and Alan Mainwaring. Wireless Sensor Networks for HabitatMonitoring[EB/OL]. http://www.eecs.berkeley.edu/IPRO/Summary/Old.summarie s/03abstracts/chapter6.html,2010-05-06.
[6]Wei Ye,John Heidemann and Deborah Estrin. An Energy-efficient MAC protocol for wireless sensor networks[C]. Proceedings of the IEEE Infocom,pp.1567-1576.June 2002.
[7]Joseph Polastre,Jason Hill and David Culler.Versatile low power media access for wireless sensor networks[C].SenSys'04, November3-5,2004,Baltimore,Maryland, USA.
[8]Michael Buettner,Gary V. Yee,Eric Anderson and Richard Han. X-MAC:A short preamble MAC protocol for duty-cycled wireless sensor networks[C].SenSys'06, November 1-3,2006,Boulder,Colorado,USA.
[9]CENS. Lab-on-Chip aquatic microorganism analysis [EB/OL]. http://research.cens.ucla.edu/areas/2007/Sensors/default.htm, 2010-05-06.
[10]Stefon Shelton and Hongsoo Choi. Aluminum Nitride Ultrasonic Doppler VelocitySensor[EB/OL]. http://www-bsac.eecs.berkeley.edu/project/zoom.php? urlmyprojectID=BPN467&URLnode=2,2010-05-06.
[11]Winnie Louis Lee, Amitava Datta, and Rachel Cardell-Oliver. FlexiTP: Aflexible-schedule-based TDMA protocol for fault-tolerant and energy-efficient wireless sensor networks[J]. IEEE transactions on parallel and distributed systems, vol.19,no.6,June 2008.
[12]Inwhee Joe and Hanjong Ryu. A Patterned Preamble MAC Protocol for Wireless Sensor Networks[J].2007 IEEE.
[13]Antonio G. Ruzzelli, G.M.P O'Hare and M.J. O'Grady et al.. MERLIN: Cross-Layer Integration of MAC and Routing for Low Duty-Cycle Sensor Networks[J]. Elsevier Science,14 June 2007.
[14]Texas Instruments,CC2430 PRELIMINARY Data Sheet (rev.2.01) SWRS036E.
[15]金湘亮,旷章曲,刘志碧,等.低功耗CMOS视觉传感器新结构及其SOC实现[J].微电子学,2009,39(6)：782-785.
[16]van Dam T, Langendoen K. An adaptive energyefficient mac protocol for wireless sensor networks. In:Proc. of the 1st ACM Conf. on Embedded Networked Sensor Systems (SenSys). New York:ACM Press,2003.171-180.
[17]IEEE 802.15.4-2006, "Part 15.4:Wireless LAN MediumAccess Control (MAC) and Physical Layer (PHY) Specificationsfor Low-Rate Wireless Personal Area Networks(LR-WPANs)," 2006.
[18]C. C. Enz et al., "WiseNET:An Ultralow-Power Wireless Sensor Network Solution," IEEE Comp., vol.37, no.8,Aug.2004.
[19]Heping Wang, Xiaobo Zhang, Farid Nait-Abdesselam and Ashfaq Khokhar DPS-MAC:An Asynchronous MAC Protocol for Wireless Sensor Networks[C].HiPC 2007, LNCS 4873, pp.393-404,2007.
[20]]IEEE Standard for Wireless LAN Medium Aecess Control (MAC) and Physical Layer (PHY) Specifications,ISO/IEC8802-11:1999E,1999.
[21]Chipcon, "2.4GHz IEEE802.15.4/ZigBee-ready RF Transceiver datasheet (revl.2)," Chipcon AS, Oslo, Norway,2004.
[22]NS-2Wiki.ProjectNews[EB/OL]. http://nsnam.isi. edu/nsnam/index.php/Main_Pag e,2010/04/06.
[23]徐雷鸣,庞博,赵耀.NS与网络模拟[M].北京：人民邮电出版社,2003：5-6.
[24]柯志亨.使用NOAH (NO Ad-Hoc Routing Agent)无线网路静态路由[EB/OL]. http.//140.116.72.80/-smallko/ns2/noah_st.htm,2010-05-06.
[25]胡呈欣.一种适用于流量突发的无线传感器网络的MAC协议[D].武汉：武汉理工大学,2008.