外文翻譯-基于無線傳感器網(wǎng)絡(luò)的智能家居系統(tǒng)設(shè)計(jì)

1、A Simple Energy Model for Wireless Microsensor TransceiversAbstract This paper describes the modelling of shortrange transceivers for microsensor applications. A simple energy model is derived and used to analyze the transceiver battery life. This model takes into account energy dissipation during t

2、he start-up, receive, and transmit modes. It shows that there is a significant fixed cost in the transceiver energy consumption and this fixed cost can be driven down by increasing the data rate of the transceiver.I. IntroductionWireless microsensor networks can provide short-range connectivity with

3、 significant fault tolerances. These systems find usage in diverse areas such as environmental monitoring, industrial process automation, and field surveillance. As an example, Table I shows a detailed specification for a sensor system used in a factory machine monitoring environment.The major chara

4、cteristics of a microsensor system are high sensor density, short range transmissions, and low data rate. Depending on the application, there can also be stringent BER and latency requirements. Due to the large density and the random distributed nature of these networks, battery replacement is a dif

5、ficult task. In fact,a primary issue that prevents these networks to be used in many application areas is the short battery life. Therefore, maximizing the battery life time of the sensor nodes is important. Figure 1 shows the peak current consumption limit when a 950mAh battery is used as the energ

6、y source. As seen in the figure, battery life can vary by orders of magnitude depending on the duty cycle of each operation. To allow for higher maximum peak current, it is desirable to have the sensor remain in the off-state for as long as possible.However, the latency requirement of the system dic

7、tates how often the sensor needs to be active. For the industrial sensor application described above, the sensor needs to operate every 5ms to satisfy the latency requirement.Assuming that the sensor operates for 100s every 5ms,the duty cycle is 2%. To achieve a one-year battery life, the peak curre

8、nt consumption must be kept under 5.4mA, which translates to approximately 10mW at 2V supply.This is a difficult target to achieve for sensors that communicate at giga-Hertz carrier frequencies. There has been active research in microsensor networks over the past years. Gupta 1 and Grossglauser 2 es

9、tablished information theoretic bounds on the capacity of ad-hoc networks. Chang 3 and Heinzelman 4 suggested algorithms to increase overall network life-time by spreading work loads evenly among all sensors. Much of the work in this area, especially those that deal with energy consumption of sensor

10、 networks, require an energy model 5. This paper develops a realistic energy model based on the power consumption of a state of the art Bluetoothtransceiver 6. This model provides insights into how to minimize the power consumption of sensor networks and can be easily incorporated into work that stu

11、dies energy limited wireless sensor networks. The outline of this paper is as follows. Section II derives the transceiver model. Section III applies this model to analyzing the battery life time of the Bluetooth transceiver.Section IV investigates the dependencies in the model and shows how to modif

12、y the design of the Bluetooth transceiver to improve the battery life. Section V shows the battery life improvement realized by applying the results in Section IV. Section VI summarizes the paper.II. Microsensor Transceiver ModellingThis section derives a simple energy model for low power microsenso

13、rs. Figure 2 shows the model of the sensor node.It includes a sensor/DSP unit for data processing, D/A and A/D for digital-to-analog and analog-to-digital conversion, and a wireless transceiver for data communication. The sensor/DSP, D/A, and A/D operate at low frequency and consume less than 1mW. T

14、his is over an order of magnitude less than the power consumption of the transceiver. Therefore, the energy model ignores the contributions from these components. The transceiver has three modes of operation: start-up, receive, and transmit. Each mode will be described and modelled.A. Start-up ModeW

15、hen the transceiver is first turned on, it takes some time for the frequency synthesizer and the VCO to lock to the carrier frequency. The start-up energy can be modelled as follows:where P LO is the power consumption of the synthesizer and the VCO. The term t start is the required settling time. RF

16、 building blocks including PA, LNA, and mixer have negligible start-up time and therefore can remain in the off-state during the start-up mode. B. Receive Mode The active components of the receiver includes the low noise amplifier (LNA), mixer, frequency synthesizer, VCO, intermediate-frequency (IF)

17、 amplifier (amp), and demodulator (Demod). The receiver energy consumption can be modelled as follows:where P RX includes the power consumption of the LNA,mixer, IF amplifier, and demodulator. The receiver power consumption is dictated by the carrier frequency and the noise and linearity requirement

18、s. Once these parameters are determined, to the first order the power consumption can be approximated as a constant, for data rates up to 10s of Mb/s. In other words, the power consumption is dominated by the RF building blocks that operate at the carrier frequency. The IF demodulator power varies w

19、ith data rate, but it can be made small by choosing a low IF.C. Transmit ModeThe transmitter includes the modulator (Mod), frequency synthesizer and VCO (shared with the receiver), and power amplifier (PA). The data modulates the VCO and produces a FSK signal at the desired data rate and carrier fre

20、quency. A simple transmitter energy model is shown in Equation (3). The modulator consumes very little energy and therefore can be neglected.P LO can be approximated as a constant. P PA depends on additional factors and needs to be modelled more carefully as follows:where is the PA efficiency, r is

21、the data rate, d is the transmission distance, and n is the path loss exponent. PA is a factor that depends on E b /N O , noise factor F of the receiver, link margin L mar , wavelength of the carrier frequency , and the transmit/receive antenna gains G T ,G R :From Equations (3) and (4), the transmi

22、tter power consumption can be written as a constant term plus a variable term. The energy model thus becomesIII. Bluetooth TransceiverHere we demonstrate how the above model can be used to calculate the battery life time of a Bluetooth transceiver 6. This is one of the lowest power Bluetooth transce

23、ivers reported in literature. The energy consumption of the transceiver depends on how it operates. Assuming a 100-bit packet is received and a 100-bit packet is transmitted every 5ms, Figure 3 showsthe transceiver activity within one cycle of operation.The transceiver takes 120s to start up. Operat

24、ing at 1Mb/s, the receiver takes 100s to receive the packet. The transceiver then switches to the transmit mode and transmits a same-length packet at the same rate. A 10s interval, t switch , between the receive and the transmit mode is allowed to switch channel or to absorb any transient behavior.

25、Therefore, the energy dissipated in one cycle of operation is simplyBoth the average power consumption and the duty cycle can be found From Figure 3. Knowing that the transceiver operates at 2V, the life time for a 950mAh battery is calculated to be approximately 2-months.IV. Energy OptimizationThe

26、microsensor system described in Section I requires a battery life of one year or better. Although the Bluetooth transceiver described in the last section falls short of this requirement, it serves as a starting point for making improvements. This section examines E op in detail and suggests ways to

27、increase the battery life by considering both circuit and system improvements.A. Start-up Energy The start-up energy can be a significant part of the total energy consumption, especially when the transceiver is used to send short packets in burst mode. For the Bluetooth transceiver, E start accounts

28、 for 20% of E op .The start-up energy becomes negligible if the following condition is held true:For the receive/transmit scheme shown in Figure 3, the right hand-side of Equation (8)is evaluated to be approximately 450s. To keep E start an order of magnitude below E op , it is desirable to have a s

29、tart-up time of less than 45s. Cho has demonstrated a 5.8GHz frequency synthesizer im-plementation with a start-up time under 20s 7.B. Power AmplifierThe PA power consumption is given bywhere is the power efficiency and P out is the RF output power. P out can be determined by link-budget analysis. F

30、or a Bluetooth transceiver, the required P out is 1mW 8.This enables a maximum transmission distance of 10 meters, which is adequate for microsensor applications. Note that P out is small as compared to P LO . The Bluetooth transceiver discussed in Section II has a maximum RF output power of 1.6mW a

31、nd a PA power consumption of 10mW, so the efficiency is at 16%. At frequencies around 2GHz, the PA efficiency can vary from 10% 9 to 70% 10 depending on linearity, circuit topology, and technology. Since FSK signal has a constant envelope, nonlinear PAs can be used so that better efficiency can be a

32、chieved. As will be shown in the next section, PA efficiency has a significant impact on the battery life.C. Data RateAssuming a packet of length L pkt is transmitted at dat rate r, then the transmit time isThe transmitter energy consumption can be re-written asEquation (12) shows that the contribut

33、ion of the fixed cost P LO can be reduced by increasing the data rate. The energy per bit, E bit , is defined as E op divided by the total number of bits received and sent during one cycle of operation. Assuming a packet of length L pkt is received and a packet of the same length is transmitted, E b

34、it can be found by dividing Equation (7) by 2L pkt . Substituting the appropriate expressions for E start , E rx , and E tx and re-arranging the terms, we getThe first term in Equation (13) is the start-up energy cost. The second term is the PA energy cost. The third term is the cost of the rest of

35、the transceiver electronics during the transmit and receive modes. Note that this term is divided by the data rate r. Figure 4 shows E bit as a function of data rate. The two solid curves have start-up time 120s and PA efficiencies 10% and 70%, respectively. The two dotted curves have start-up time

36、20s and efficiencies 10% and 70%, respectively. At low data rate, E bit is dominated by the fixed cost (the 3rd term in Equation (13). At high data rate, the start-up energy and the PA energy dominates, so in order to increase battery life, good circuit design techniques need to be applied to minimi

37、ze the start-up time and to maximize the PA efficiency.Figure 5 shows the impact of PA efficiency on the battery life at a data rate of 10Mb/s. At t start = 120s, the startup energy is so large that the battery life is limited to 7month even if the PA reaches 100% efficiency. At t start =20s, the ba

38、ttery life is much improved. The PA efficiencyneeds to be higher than about 30% to have a 1-year or better battery life. This is certainly achievable as discussed previously in the PA section.V. Performance ImprovementThere are three apparent results from the previous section. First, the data rate s

39、hould be increased to reduce the fixed cost. Second, the start-up time should be minimized. Third, PA efficiency should be maximized. Figure 6 shows the transceiver activity for a transceiver that has 20s start-up time and 10Mb/s data rate. The power consumption of the electronics are kept the same

40、as in the Bluetooth transceiver except for the PA. The maximum RF output power is set at 10mW to accommodate the higher data rate, and the PA efficiency is assumed to be 50%. The switching time is kept at 10s, although this is a conservative since the switching time is likely to be shorter for a fas

41、ter frequency synthesizer. The E op of this transceiver is 8x lower than that of the Bluetooth transceiver. The battery life-time extends from 2-months to approximately1.3 years.VI. ConclusionThis paper describes the modelling of short-range transceivers for wireless sensor applications. This model

42、takes into account energy dissipation during the start-up, transmit, and receive modes. This model is first used to analyze the battery life of a state of the art Bluetooth transceiver, and then it is used to optimize E op . This paper shows that the battery life can be improved significantly by inc

43、reasing the data rate, reducing the start-up time, and improving the PA efficiency. Increasing the data rate drives down the fixed energy cost of the transceiver. Reducing the start-up time decreases the start-up energy overhead. Improving the PA efficiency lowers the energy per bit cost of the PA.一

44、個簡單的能量無線微傳感器的接收機(jī)模型摘要本文描述了微傳感器的近程的收發(fā)器的造型的應(yīng)用程序。一個簡單的能量模型推導(dǎo)并用于分析收發(fā)機(jī)的電池壽命。這個模型考慮能量耗散在啟動期間,接收和傳輸模式。這表明有一個收發(fā)器能耗的重要固定成本和固定成本可以驅(qū)動下通過增加數(shù)據(jù)收發(fā)器的速度。I.我的介紹無線微傳感器網(wǎng)絡(luò)可以提供短程連接與重大故障公差。這些系統(tǒng)在多樣化的環(huán)境監(jiān)測等領(lǐng)域,找到使用工業(yè)過程自動化,和現(xiàn)場監(jiān)測。作為一個例子,我表顯示了一個詳細(xì)的規(guī)范傳感器系統(tǒng)在工廠使用機(jī)器監(jiān)控環(huán)境。微傳感器系統(tǒng)的主要特點(diǎn)是傳感器密度高、短距離傳輸和低數(shù)據(jù)率。這取決于應(yīng)用程序,也可以嚴(yán)格的誤碼率和延遲要求。由于大密度和隨機(jī)的這

45、些網(wǎng)絡(luò)的分布式特性,電池更換是一項(xiàng)艱巨的任務(wù)。事實(shí)上,一個主要的問題,防止這些網(wǎng)絡(luò)使用在許多應(yīng)用領(lǐng)域是短的電池壽命。因此,傳感器節(jié)點(diǎn)的電池壽命時(shí)間最大化是非常重要的。圖1顯示了峰值電流消耗限制在950 mah電池作為能量來源。在圖中可以看到,電池壽命可以通過數(shù)量級變化取決于每個操作的工作周期。允許更高的最大峰值電流,是理想的傳感器保持盡可能的斷開狀態(tài)。然而,系統(tǒng)的延遲要求規(guī)定頻率傳感器需要活躍。對于上述工業(yè)傳感器應(yīng)用,傳感器需要操作每5女士來滿足延時(shí)要求。假設(shè)傳感器運(yùn)作100年s每5 ms,占空比為2%。達(dá)到一年的電池壽命,峰值電流消耗必須保持在5.4,這意味著大約有10 mw 2 v供應(yīng)。這

46、是一個很難實(shí)現(xiàn)的目標(biāo)在giga-Hertz傳感器通信的載波頻率。有積極的研究在微傳感器網(wǎng)絡(luò)在過去的幾年中。Gupta 和Grossglauser建立了信息理論界限自組網(wǎng)的能力。Chang 和 Heinzelman建議的算法來提高整體網(wǎng)絡(luò)壽命通過傳播工作負(fù)載均勻地在所有傳感器。在這一領(lǐng)域的大部分工作,特別是那些處理傳感器網(wǎng)絡(luò)的能量消耗,需要一個能量模型。本文發(fā)展一個現(xiàn)實(shí)的能源模型基于能耗最先進(jìn)的藍(lán)牙收發(fā)器。這個模型提供了見解如何最小化的功耗傳感器網(wǎng)絡(luò),可以很容易地納入工作,研究能源有限的無線傳感器網(wǎng)絡(luò)。本文的概述如下。第二節(jié)收發(fā)器模型。第三節(jié)該模型適用于分析藍(lán)牙收發(fā)器的電池壽命時(shí)間。第四部分調(diào)查

47、中的依賴關(guān)系模型,并展示了如何修改藍(lán)牙收發(fā)器的設(shè)計(jì)來提高電池壽命。第五部分顯示了電池壽命的改進(jìn)實(shí)現(xiàn)了應(yīng)用結(jié)果第四節(jié)。第六部分總結(jié)了紙。II.微傳感器收發(fā)器造型本節(jié)源于一個簡單的低功耗微傳感器能量模型。圖2顯示了傳感器節(jié)點(diǎn)的模型。它包括一個傳感器/ DSP數(shù)據(jù)處理單元,D / a和a / D數(shù)模和模數(shù)轉(zhuǎn)換,并為數(shù)據(jù)通信無線收發(fā)器。傳感器/ DSP、D / A和A / D操作在低頻率和消費(fèi)不到1兆瓦。這是在一個數(shù)量級小于收發(fā)器的功耗。因此,能源模型忽略了這些組件的貢獻(xiàn)。收發(fā)器有三種操作模式:啟動,接收和傳輸。每個模式都將被描述和建模。A. 啟動模式收發(fā)器是第一次打開時(shí),它需要一些時(shí)間和頻率合成器V

48、CO載波頻率鎖定。啟動能量可以參照如下:在P LO的功耗是合成器VCO。術(shù)語t開始所需的穩(wěn)定時(shí)間。射頻構(gòu)件包括PA、低噪聲放大器和混頻器的啟動時(shí)間可以忽略不計(jì),因此可以保持在斷開的啟動模式。B. 接收模式接收機(jī)的活性成分包括低噪聲放大器(LNA)、攪拌機(jī)、頻率合成器VCO,中頻放大器(如果)(amp),和解調(diào)器(解調(diào))。接收方能源消耗可以參照如下:在P RX包括低噪聲放大器的功耗、攪拌機(jī)、中頻放大器、解調(diào)器。接收機(jī)功耗是由載波頻率和噪聲和線性度的要求。一旦確定這些參數(shù),對一階功耗可以近似為一個常數(shù),為數(shù)據(jù)率10 Mb / s。換句話說,能耗由射頻積木在載波頻率。如果解調(diào)器功率隨數(shù)據(jù)速率,但它可

49、以小如果通過選擇低。C. 傳送方式發(fā)射機(jī)包括調(diào)制器(Mod),頻率合成器VCO與接收機(jī)(共享),和功率放大器(PA)。數(shù)據(jù)調(diào)整VCO的移頻鍵控信號并產(chǎn)生所需的數(shù)據(jù)率和載波頻率。一個簡單的發(fā)射機(jī)能源模型方程(3)所示。調(diào)制器消耗很少的能量,因此可以忽略不計(jì)。P LO可以近似為一個常數(shù)。P PA取決于其他因素,需要更仔細(xì)地建模如下:在巴勒斯坦權(quán)力機(jī)構(gòu)效率,r是數(shù)據(jù)速率,d是傳輸距離,n是路徑損耗指數(shù)。PA是一個因素,取決于E b / N O,接收機(jī)的噪聲系數(shù)F,鏈接保證金L mar,載波頻率的波長,和發(fā)送/接收天線收益G T G R:從方程(3)和(4),發(fā)射機(jī)功率消耗可以寫成一個常數(shù)項(xiàng)和一個變量。因此成為能量模型III. 藍(lán)牙發(fā)接器在這里我們將演示如何使用上述模型計(jì)算藍(lán)牙收發(fā)器的電池壽命時(shí)間6。這是一個最低的功率藍(lán)牙收發(fā)器報(bào)告文學(xué)。收發(fā)器的能源消耗取決于它是如何運(yùn)行的。假設(shè)收到一個100位的包和一個100位的數(shù)據(jù)包傳輸每5 ms,圖3顯示了收發(fā)機(jī)的活動在一個循環(huán)操作。收發(fā)機(jī)需要120s啟動。操作在1 mb / s,接收機(jī)需要100s接收數(shù)據(jù)包。收發(fā)器然后切換到傳播模式和傳播長度相同包以同樣的速度。10s間隔,t開關(guān),允許接