1、學校代碼： 10128學 號： 201110107012 本科畢業(yè)論文（英文參考文獻及譯文）題 目：ZigBee: Wireless Technology for Low-Power Sensor Networks學生姓名：王金學 院：機械學院系 別：測控系專 業(yè)：測控技術與儀器班 級：測控11-2 指導教師：王穎 講師二 一 五 年 六 月內蒙古工業(yè)大學本科畢業(yè)論文文獻翻譯譯文ZigBee：無線技術，低功耗傳感器網絡加里萊格美國東部時間2004年5月6日上午12:00技師（工程師）們在發(fā)掘無線傳感器的潛在應用方面從未感到任何困難。例如，在家庭安全系統(tǒng)方面，無線傳感器相對于有線傳感器更易安裝。

2、而在有線傳感器的裝置通常占無線傳感器安裝的費用80%的工業(yè)環(huán)境方面同樣正確。而且相比于有線傳感器的不切實際甚至是不肯能而言，無線傳感器更具應用性。雖然，無線傳感器需要消耗更多能量，也就是說所需電池的數(shù)量會隨之增加或改變過于頻繁。再加上對無線傳感器由空氣傳送的數(shù)據(jù)可靠性的懷疑論，所以無線傳感器看起來并不是那么吸引人。一個低功率無線技術被稱為ZigBee。一個安全的網絡技術，最近通過的IEEE 802.15.4無線標準（圖1），ZigBee的承諾，把無線傳感器的一切從工廠自動化系統(tǒng)到家庭安全系統(tǒng)，消費電子產品包括進來。與802.15.4的合作下，ZigBee提供具有電池壽命可比普通小型電池的長幾年

3、。ZigBee設備預計也便宜，有人估計銷售價格最終不到3美元每節(jié)點。由于價格低，他們應該是一個自然適應于在光線如無線交換機，無線自動調溫器，煙霧探測器和家用產品。（圖1）雖然還沒有正式的規(guī)范的ZigBee存在（由ZigBee聯(lián)盟是一個貿易集團，批準應該在今年年底），但ZigBee的前景似乎一片光明。技術研究公司In-Stat/MDR在它所謂的“謹慎進取”的預測中預測，802.15.4節(jié)點和芯片銷售將從今天基本上為零，增加到2010年的165萬臺。不是所有這些單位都將與ZigBee結合，但大多數(shù)可能會。世界研究公司預測的到2010年射頻模塊無線傳感器出貨量4.65億美量，其中77是ZigBee的

4、相關。（圖2）從某種意義上說，ZigBee的光明前途在很大程度上是由于其較低的數(shù)據(jù)速率20 kbps到250 kbps的，用于取決于頻段頻率（圖2），比標稱為1 Mbps的藍牙和54 Mbps的Wi - Fi的技術數(shù)據(jù)速率低。ZigBee的不能像Wi-Fi一樣發(fā)送電子郵件和大型文件，或像藍牙一樣傳送文件和音頻。對于發(fā)送傳感器的讀數(shù)，這是典型的數(shù)萬字節(jié)數(shù)，高帶寬是沒有必要，ZigBee的低帶寬有助于它實現(xiàn)其目標和魯棒性的低功耗，低成本。由于ZigBee應用的是低帶寬要求，ZigBee節(jié)點大部分時間可以睡眠模式，從而節(jié)省電池電源，然后醒來，快速發(fā)送數(shù)據(jù)，回去睡眠模式。而且，由于ZigBee可以從睡

5、眠模式過渡到15毫秒或更少主動模式下，即使是睡眠節(jié)點也可以達到適當?shù)牡脱舆t。有人扳動支持ZigBee的無線光開關，例如，將不會是一個喚醒延遲知道前燈亮起。與此相反，支持藍牙喚醒延遲通常大約三秒鐘。一個ZigBee的功耗節(jié)省很大一部分來自802.15.4無線電技術，它本身是為低功耗設計的。802.15.4采用DSSS（直接序列擴頻）技術，例如，因為（跳頻擴頻）另類醫(yī)療及社會科學院將在保持一樣使用它的頻率過大的權力同步。ZigBee節(jié)點，使用802.15.4，是幾個不同的溝通方式之一，然而，某些方面比別人擁有更多的使用權力。因此，ZigBee的用戶不一定能夠實現(xiàn)傳感器網絡上的任何方式選擇和他們仍然

6、期望多年的電池壽命是ZigBee的標志。事實上，一些技術專家打算用小型無線傳感器創(chuàng)建大的網絡，即使功率ZigBee的電池需求很大。一個ZigBee網絡節(jié)點可以消耗額外的功率，例如，如果它試圖避免與其他節(jié)點的傳輸或與其他無線電源傳輸重疊的傳輸。那么在ZigBee 802.15.4無線電的使用實現(xiàn)CSMA / CA（載波偵聽多址接入沖突避免）技術，與ZigBee節(jié)點使用CSMA / CA是基本上采取了聽先于談話的方式，看是否有無線電通信已經展開。但是，傳感器營銷公司恩貝爾公司副總裁兼ZigBee聯(lián)盟的副主席Venkat Bahl正如所指出的，這不是一個首選的方法。“有聽意見的權力，”Bahl說，“

7、我們不喜歡這樣做。”ZigBee和802.15.4通訊的另一個選擇是指路明燈模式，通常睡覺模式醒來網絡節(jié)點定期從網絡的控制節(jié)點接收同步“燈塔”的指令。但是，也因為時間的不確定性，特別是支配節(jié)點打開，以免錯過早期一盞明燈。爭議中的通信為了盡可能節(jié)省電力，ZigBee采用一種簡單交際策略,talk-when-ready發(fā)送數(shù)據(jù)時,數(shù)據(jù)準備派遣然后就等著自動確認。兩ZigBee聯(lián)盟主席和電子802.15,talk-when-ready是“開門見山地”計劃,但卻是一種很有電力效率的策略。“我們在廣泛的分析,得出了最好的節(jié)能策略”Heile說。“我們發(fā)現(xiàn),我們在發(fā)送才離開那包東西和承認它。如果你不想讓他

8、查詢反饋信息,它只表示你接收失敗,所以重發(fā)給你。你有更好的電源管理，并確定它是否安靜，然后再確定。”幸運的是，這種當面策略導致RF干擾非常小。這主要是因為ZigBee節(jié)點具有非常低的占空比，只偶爾傳輸發(fā)送少量的數(shù)據(jù)。其他ZigBee節(jié)點，以及Wi - Fi和藍牙模塊，可以輕松應付這么小，頻繁爆發(fā)。ZigBee的通話時就緒計劃并不適合所有的目的，但是，例如，在成千上萬的微型傳感器網絡進入戰(zhàn)區(qū)下降到監(jiān)視敵方部隊調動，積蓄力量提供的仍可能是不夠的。每個網絡節(jié)點周期性地發(fā)送和反復通過網狀網絡配置中的其他節(jié)點附近多次以達到網絡控制器的大碰撞和重發(fā)的數(shù)據(jù)包數(shù)量可能會浪費功率，并顯著縮短傳感器節(jié)點的電池壽命

9、傳輸數(shù)據(jù)。如果傳感器電池非常小，功率有限，這特別成問題。雖然大氣電波訪問競爭不是一般意義上的ZigBee問題，都可以。傳感器網絡公司塵埃網絡，說是保持競爭問題，從該公司的ZigBee轉向為現(xiàn)在，塵土縱然仍是ZigBee聯(lián)盟的成員。每個ZigBee設備需要與鄰國爭奪領空， Dust產品管理總監(jiān)羅伯特說：有一些爭論，一些不可避免的低效率。為了避免ZigBee的訪問的爭奪，通信使用免費的TDMA（時分多址）技術。ZigBee的802.15.4 MAC層通過提供擔保的計劃，有點類似于TDMA的時隙，但只是作為一個可選的“超碼”那更復雜，更省電，比TDMA的有效組成部分。它減少了對功能設備來進行節(jié)能控制

10、，除了更強大的全功能設備（FFDs）在ZigBee元件提供電力的消耗。每個ZigBee網絡至少需要一個控制器作為一個發(fā)展籌資，但有大多數(shù)網絡節(jié)點的RFDs可以（圖3）。它們含有比FFDs較少的電路，很少或沒有功率消耗的內存。（圖3）ZigBee的節(jié)省，減少了相關處理仍然需要更多的權力。簡單的8位像8051處理器可以處理家務容易的ZigBee和ZigBee協(xié)議棧占用很少的內存。發(fā)展籌資的一個堆棧，例如，大概需要32字節(jié)，一個RFD的堆棧只需要4字節(jié)。從ZigBee的比較簡單的實現(xiàn)，節(jié)約了成本，自然產生。RFDs，減少漏報ZigBee的內存和其他電路元件成本，以及簡單的8位處理器和小協(xié)議棧幫助保持

11、系統(tǒng)成本。通常，一個應用程序的主處理器可以很容易地承擔了ZigBee的處理功能，額外的負載小，使得ZigBee不必要添加單獨的處理器。但是，保持ZigBee的低價格的主要策略是因為有很大的市場和高容量。ZigBee聯(lián)盟，通過一個開放的標準，并通過大力推進ZigBee設備之間的互操作性，ZigBee的預期應用非常大，如家庭與樓宇自動化應用。該聯(lián)盟目前正在為這些特殊應用努力，它預計將在今年較遲時與ZigBee規(guī)范1.0的互操作性的程序一起完成。一個有關的ZigBee家庭自動化與安全通過樂觀的原因是它的易用性。ZigBee網絡的自我形成，使消費者更容易對它們進行設置。“在居住空間，有沒有配置參與”Z

12、igBee聯(lián)盟的Heile說。“你從箱子拿一些東西，放電池進去，可能做一些簡單的按鈕操作，按下安全帶來使兩個設備并攏，按動按鈕，直到綠色燈光來，你就完成了。”ZigBee網絡還可以自行在商業(yè)和工業(yè)環(huán)境的形式，但專業(yè)安裝人員將有特別的安全工具，提供額外的控制。ZigBee是安全靈活的，Heile說，給消費者和專業(yè)用戶他們需要的。“你不必有128位公共密鑰加密的煙霧探測器，”他說，“但如果我在一幢復雜的高層辦公樓，這正是我的安全級別將有熒光燈。如果你在第五大道上的高層建筑里，你不想去安排人到街上，把你的燈關了。專利競爭ZigBee的競爭幾乎完全來自主專有技術。傳感器公司Dust，如上所述，是堅持使

13、用自己的技術，顯然的，雖然強烈的推到ZigBee舞臺上，計劃繼續(xù)提供其專有Ember Net設備。通過提供互操作性，但ZigBee的補充能力，專利產品不能。舉例說，Ember的義巴爾，互操作性允許照明系統(tǒng)的ZigBee節(jié)點的工作，在一個空調系統(tǒng)的ZigBee網絡，反之亦然。“飛利浦照明是真的對這個很興奮，”義巴爾說，“因為原來從一到建筑物的自動化系統(tǒng)的基礎設施骨干鎮(zhèn)流器生產廠家他們。”不用說，主要的半導體公司很多，尤其是那些在嵌入式系統(tǒng)公司中大都熱切期待ZigBee的投入并且大規(guī)模進入市場。飛思卡爾半導體（直到最近，摩托羅拉半導體產品部稱）已經提供ZigBee - ready技術來選擇客戶。其

14、他半導體公司，包括AMI，愛特梅爾，微芯片，飛利浦，瑞薩，都是ZigBee聯(lián)盟的成員。 ZigBee可能是緩慢滲透到無線傳感器的工業(yè)市場，但是。據(jù)對世界市場研究公司，它會需要五至七年來說服客戶在工業(yè)上的可靠性，耐用性，以及無線傳感器系統(tǒng)的安全。并顯著預測在整個世界中ZigBee將長期在工業(yè)制造上有增長，因此。到2010年，公司項目，射頻模塊，應用于工業(yè)監(jiān)控和控制得將達到1.65億臺，同比增長190萬元，在世界性預測中，在2004年。大約75的將基于ZigBee和802.15.4。最終，ZigBee的可進入各種廣泛的應用。家用電器，它可以幫助監(jiān)測和控制能源消耗。在汽車應用中，它可以提供輪胎壓力監(jiān)

15、測和遠程無鑰匙進入系統(tǒng)。也可用于ZigBee的醫(yī)療設備中，甚至在計算機外圍設備，如無線鍵盤或鼠標。值得關注的是越來越多，雖然，ZigBee的可能變成一種適合所有的技術的尺寸，并不很適合任何應用程序。一些持懷疑態(tài)度，例如，企圖使ZigBee無所不包的想法可能使ZigBee協(xié)議棧太大，ZigBee的雙重目標是非常低的功耗和非常低的成本。如果出現(xiàn)這種情況，那么ZigBee的低功耗，低數(shù)據(jù)速率利基窄，如果它是，將被證明是過于寬泛的。然后，也許我們會需要另一種無線標準，以配合我們已經有的蓬勃發(fā)展的人數(shù)。加里萊格是一家位于波士頓的自由撰稿人。他擁有電子工程學士學位，曾任編輯，EDN雜志執(zhí)行編輯。5原文Zi

16、gBee: Wireless Technology for Low-Power Sensor NetworksGary Legg 5/6/2004 12:00 AM EDT Technologists have never had trouble coming up with potential applications for wireless sensors. In a home security system, for example, wireless sensors would be much easier to install than sensors that need wiri

17、ng. The same is true in industrial environments, where wiring typically accounts for 80% of the cost of sensor installations. And then there are applications for sensors where wiring isn't practical or even possible.The problem, though, is that most wireless sensors use too much power, which mea

18、ns that their batteries either have to be very large or get changed far too often. Add to that some skepticism about the reliability of sensor data that's sent through the air, and wireless sensors simply haven't looked very appealing.A low-power wireless technology called ZigBee is rewritin

19、g the wireless sensor equation, however. A secure network technology that rides on top of the recently ratified IEEE 802.15.4 radio standard (Figure 1), ZigBee promises to put wireless sensors in everything from factory automation systems to home security systems to consumer electronics. In conjunct

20、ion with 802.15.4, ZigBee offers battery life of up to several years for common small batteries. ZigBee devices are also expected to be cheap, eventually selling for less than $3 per node by some estimates. With prices that low, they should be a natural fit even in household products like wireless l

21、ight switches, wireless thermostats, and smoke detectors.Figure 1:  ZigBee adds network, security, and application-services layers to the PHY and MAC layers of the IEEE 811.15.4 radioAlthough no formal specification for ZigBee yet exists (approval by the ZigBee Alliance, a trade group, should c

22、ome late this year), the outlook for ZigBee appears bright. Technology research firm In-Stat/MDR, in what it calls a "cautious aggressive" forecast, predicts that sales of 802.15.4 nodes and chipsets will increase from essentially zero today to 165 million units by 2010. Not all of these u

23、nits will be coupled with ZigBee, but most probably will be. Research firm ON World predicts shipments of 465 million wireless sensor RF modules by 2010, with 77% of them being ZigBee-related.In a sense, ZigBee's bright future is largely due to its low data rates20 kbps to 250 kbps, depending on

24、 the frequency band used (Figure 2)compared to a nominal 1 Mbps for Bluetooth and 54 Mbps for Wi-Fi's 802.11g technology. But ZigBee won't be sending email and large documents, as Wi-Fi does, or documents and audio, as Bluetooth does. For sending sensor readings, which are typically a few te

25、ns of bytes, high bandwidth isn't necessary, and ZigBee's low bandwidth helps it fulfill its goals of low power, low cost, and robustness.Figure 2:  ZigBee's data rates range from 20 kbps to 250 kbps, depending on the frequency usedBecause of ZigBee applications' low bandwidth r

26、equirements, a ZigBee node can sleep most of the time, thus saving battery power, and then wake up, send data quickly, and go back to sleep. And, because ZigBee can transition from sleep mode to active mode in 15 msec or less, even a sleeping node can achieve suitably low latency. Someone flipping a

27、 ZigBee-enabled wireless light switch, for example, would not be aware of a wake-up delay before the light turns on. In contrast, wake-up delays for Bluetooth are typically around three seconds.A big part of ZigBee's power savings come from the radio technology of 802.15.4, which itself was desi

28、gned for low power. 802.15.4 uses DSSS (direct-sequence spread spectrum) technology, for example, because the alternative FHSS (frequency-hopping spread spectrum) would have used too much power just in keeping its frequency hops synchronized.ZigBee nodes, using 802.15.4, can communicate in any of se

29、veral different ways, however, and some ways use more power than others. Consequently, ZigBee users can't necessarily implement a sensor network any way they choose and still expect the multiple-year battery life that is ZigBee's hallmark. In fact, some technologists who are planning very la

30、rge networks of very small wireless sensors say that even ZigBee is too power hungry for their uses.A ZigBee network node can consume extra power, for example, if it tries to keep its transmissions from overlapping with other nodes' transmissions or with transmissions from other radio sources. T

31、he 802.15.4 radio used by ZigBee implements CSMA/CA (carrier sense multiple access collision avoidance) technology, and a ZigBee node that uses CSMA/CA is essentially taking a listen-before-talk approach to see if any radio traffic is already underway. But, as noted by Venkat Bahl, marketing vice pr

32、esident for sensor company Ember Corp. and vice chairman of the ZigBee Alliance, that's not a preferred approach. "Having to listen burns power," says Bahl, "and we don't like to do that."Another ZigBee and 802.15.4 communications option is the beacon mode, in which norma

33、lly sleeping network slave nodes wake up periodically to receive a synchronizing "beacon" from the network's control node. But listening for a beacon wastes power, too, particularly because timing uncertainties force nodes to turn on early to avoid missing a beacon.In-Your-Face Communi

34、cationTo save as much power as possible, ZigBee employs a talk-when-ready communication strategy, simply sending data when it has data ready to send and then waiting for an automatic acknowledgement. According to Bob Heile, who is chairman of both the ZigBee Alliance and IEEE 802.15, talk-when-ready

35、 is an "in-your-face" scheme, but one that's very power efficient. "We did an extensive analysis that led to the best power-saving strategy in various kinds of environments from quiet to noisy," Heile says. "We discovered that, hands down, we were better off just sending

36、 the packet and acknowledging it. If you don't get an ack, it just means you got clobbered, so send it again. You wind up having much better power management than if you listen and determine if it's quiet before you talk." Fortunately, this in-your-face strategy leads to very little RF

37、interference. That's largely because ZigBee nodes have very low duty cycles, transmitting only occasionally and sending only small amounts of data. Other ZigBee nodes, as well as Wi-Fi and Bluetooth modules, can easily deal with such small, infrequent bursts.ZigBee's talk-when-ready scheme d

38、oesn't suit all purposes, however. For example, in a network of thousands of tiny sensors dropped into a war zone to monitor enemy troop movements, the power savings provided still might not be enough. With each network node sending data periodicallyand with transmissions repeated numerous times

39、 through other nearby nodes of a mesh network configuration in order to reach a network controllerlarge numbers of packet collisions and retransmissions could waste power and significantly shorten sensor node battery life. If the sensor batteries are very small and power-limited, that's especial

40、ly problematic.Although contention for airwave access isn't generally a problem for ZigBee, it can be. Sensor-network company Dust Networks, in fact, says contention issues are keeping the company from turning to ZigBeefor now, at leasteven though Dust remains a member of the ZigBee Alliance. &q

41、uot;Each ZigBee device needs to contend for airspace with its neighbors," says Dust director of product management Robert Shear, "so there's inevitably some contention and some inefficiency." To avoid ZigBee's access contention, Dust uses contention-free TDMA (time division mu

42、ltiple access) technology. ZigBee, through the 802.15.4 MAC layer, provides guaranteed time slots in a scheme that somewhat resembles TDMA, but only as part of an optional "superframe" that's more complex and less power-efficient than TDMA.ZigBee has still more power-saving tricks up i

43、ts sleeve, however. For example, it reduces power consumption in ZigBee components by providing for power-saving reduced-function devices (RFDs) in addition to more capable full-function devices (FFDs). Each ZigBee network needs at least one FFD as a controller, but most network nodes can be RFDs (F

44、igure 3). RFDs can talk only with FFDs, not to other RFDs, but they contain less circuitry than FFDs, and little or no power-consuming memory.Figure 3:  ZigBee networks can contain as many as 65,536 nodes in a variety of configurationsZigBee conserves still more power by reducing the need for a

45、ssociated processing. Simple 8-bit processors like an 8051 can handle ZigBee chores easily, and ZigBee protocol stacks occupy very little memory. An FFD stack, for example, needs about 32 kbytes, and an RFD stack needs only about 4 kbytes. Those numbers compare with about 250 kbytes for the far more

46、 complex Bluetooth technology.From ZigBee's relatively simple implementations, cost savings naturally accrue. RFDs, of course, reduce ZigBee component costs by omitting memory and other circuitry, and simple 8-bit processors and small protocol stacks help keep system costs down. Often, an applic

47、ation's main processor can easily bear the small additional load of ZigBee processing, making a separate processor for ZigBee functions unnecessary.But the main strategy for keeping ZigBee prices low is to have big markets and high volumes. The ZigBee Alliance, by making ZigBee an open standard

48、and by vigorously promoting interoperability among ZigBee devices, expects that ZigBee will be very big in applications such as home and building automation. The alliance is currently working on interoperability procedures for those particular applications, which it expects to complete later this ye

49、ar along with ZigBee Specification 1.0.One reason for optimism about ZigBee adoption for home automation and security is its ease of use. ZigBee networks are self-forming, making it easy even for consumers to set them up. "In the residential space, there's no configuration involved," s

50、ays the ZigBee Alliance's Heile. "You take something out of the box, put the batteries in, and maybe do something as simple as button-press securitybring two devices close together, push the buttons until the green lights come on, and you're done."ZigBee networks can also self-form

51、 in commercial and industrial settings, but professional installers will have tools that provide additional control, particularly for security. ZigBee security is flexible, says Heile, to give both consumer and professional users what they need. "You don't have to have 128-bit public-key en

52、cryption for a smoke detector," he says, "but if I'm in a high-rise office complex, that's exactly the level of security I'm going to have for my fluorescent light fixtures. If you're in a high-rise building on Fifth Avenue, you don't want someone going down the street

53、and turning your lights off."Proprietary CompetitionBy offering interoperability, however, ZigBee adds capabilities that proprietary products can't. For example, says Ember's Bahl, interoperability allows the ZigBee nodes of a lighting system to work with the ZigBee network of an HVAC system, or vice versa. "Philips Lighting is really excited about this," Bahl, says, "because it turns them from a ballast manufacturer into the infrastructure backbone of a building-automation system."