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中國(guó)礦業(yè)大學(xué)2009屆本科生畢業(yè)設(shè)計(jì)（論文） 第17頁(yè)
翻譯部分
英文原文
Coal Face Wireless Sensor Network Physical Layer Design Based On UWB Technology
Abstract
In order to guarantee the safety of coal face production, it is necessary to monitor and surveillance face Shearer, scraper transport planes, hydraulic support, transport machines, broken machines etc . At present, it is difficult for the cable transmission mode to adapt to changes in the work site of the coal face. Transmission lines are often damaged and snapped for various factors, we use wireless sensor network (WSN), which is flexible to be placed and extensible, to resolve this problem. This paper discuss the design of the WSN transceiver for coal face with UWB technology. This kind of transceiver has some useful advantage such as low cost, low power consumption, simple structure, easy to implement the design of the hardware, no need to estimate the coal face Channel characteristics. However, detection efficiency is slightly lower, but the error rate can meet the requirement.
1. Introduction
Coal face must face the complicated geological conditions and poor working conditions. In order to ensure the safety of production in the coal face, it is necessary to monitor real-time the face Shearer, scraper transport machine, hydraulic support, reprint machine, broken machines and other large equipments. In addition, we must monitor the ground pressure, gas, carbon monoxide, dust and other environmental parameters. At the same time, mobile voice and image communications is required. At present, the signal monitored and derived from the coal face is transmitted by cable. As the face is moving constantly and the going of the coal mining process, all kinds of large-scale iron and steel equipments in the coal face need to be boosted circularly and continually. The shape of the space is constantly changing with the change of the relative position of the equipments. Correspondingly, communication in cable is difficult to be applicable with the working scene changing, so transmission lines is damaged or snapped frequently ,and the coal face mobile voice and image communication is impossible .All these issues cause many latent trouble to the Safety of the production. We think wireless sensor network (WSN) is feasible to implement monitoring and surveillance to the coal face, for it has some useful characters of placing flexibly, expanding simply, moving easily and self-organization.
2. WSN architecture in the coal face
The sensor network system structure of the mining Coal face is shown in Figure 1. In this Figure, the sensor nodes send the information of acquistion through one or more jumps to the cluster node, the base station (sink node) is responsible for the collection of data, and transmit them to task management node through up-slot network, task management Node is responsible for the integrated process the data and also issued instruction to sensor networks. The tunnel of coal face is a limited space. Bracket, shearer, transport and other large metal equipments are layout and coal, rocks and other media is a non-uniform restricted space, which all make the transmission channel more complex, fading and multi-path phenomena more serious in the transmission of wireless sensor nodes signal. These are different from sensor networks on the ground. Therefore,
the design of transceiver node of it is particularly important. At present, there are three main technologies of the physical layer in wireless sensor networks: narrow-band modulation technology, spread spectrum technology and ultra-wideband (UWB) technology. While UWB technology possesses some attractive advantages such as low power spectrum density, low-complexity system, Low sensitivity to the channel fading, better security and so on. Considering the advantages and the characteristics of coal face naturally, we have adopted Impulse radio ultra-wide band (IR-UWB) technology, and the reasons are followed: 1) UWB technology consumes lower power and has lower power spectrum. Low power consumption, low-cost and small size are the most important feature of wireless sensor network nodes. Narrow-band modulation technology, spread spectrum modulation technology generally use sine carrier , IF and RF circuits exist in the systems, so consuming more power than the UWB technology with no carrier. Transmission medium in the coal face is non-uniform, which leading to more transmission loss than wireless communications systems on the ground. Therefore low power consumption becomes particularly important. In the coal face, as WSN node presents zonal distribution, nodes just need to communicate with neighbor-nodes. The WSN system based on UWB, consuming lower transmission power, can meet the requirements and avoid the interference with each other in the narrow-band communications node. In addition, the low power consumption and high penetrating power help to design safe equipment and transmit disaster relief signal. 2) Strong anti-interference ability. In the coal face, electrical and mechanical equipment has narrow distribution. When equipment starts or stop, electrical sparkle may cause a lot of electromagnetic interference. So good anti-interference capability is strongly required in the wireless communication. 3) Good Anti-interference to multi-path ability. Coal face has some inherent characters, such as narrow space, more types of media, a multi-path intensive channel, while IR-UWB can be applied to this complicated environment with its advantages: narrow Pulse width, small pulse duration ratio, high multi-path resolution, strong anti-multi-path and fading Capacity. 4) Simple structure. The characters of IR-UWB, such as no modulation and up/down conversing frequency, simple transmitter structure, lower power consumption, make it more acceptable. According to the complexity of the node and power consumption into considerations, IR-UWB technology is very applicable to the design of the wireless sensor network physical layer. Therefore, compared to narrow-band modulation technology, spread spectrum technology, the wireless communication system based on the UWB technology present a good performance on the energy consumption, robustness, anti-multi-path and anti-noise, and so on.
The modulation of IR-UWB are mainly PAM (OOK), PPM and BPM (Bi-Phase Modulation), but the presence of lines spectrum in PAM and PPM not only make ultra-wideband pulse signal difficult to meet a certain spectrum Requirements, but also reduce the power utilization, thereby it increases energy consumption. Several IR-UWB signals in the frequency spectrum are shown in Figure 2 and Figure 3 . As WSN system requires low power consumption, PAM modulation often use OOK method, which has simple structure. But OOK has poor performance on the BER(Bit Error Rate), anti-noise performance of BPM modulation such as anti-Jitter noise is better. ISI would be intensified if we adopted PPM under the conditions of intensive multi-path environment in the coal face. Therefore, we use BPM forms in the transceiver system of the coal face.
A. The design of transmitting system
The transmitter which adopts BPM forms is shown in Figure 4. The signal distortion, interference and noise brought by the special environment in coal face need encoded protection through channel coding interweave module. Data rate of the original information is lower, which make it difficult to meet the requirements of FCC in the absence of modulation. We need to use spread spectrum code transform the original information which has a larger duration ratio into a smaller duration ratio (nanosecond). Then we can generate BPM pulse signal through the pulse formation circuit, which can meet the requirement of FCC. Finally use filters to optimize BPM signal further to enlarge the spectrum and send it out from the antenna.
The system uses Gaussian pulse to be the form of UWB signal. If a wave transmitted is the first order derivative Rayleigh pulse, the signal after sending out through the antenna is transformed to be the second order derivative of the Gaussian pulse in ideal circumstances. In addition, the lower the order of the Gaussian pulse is, the farther the signal can be sent under the same data rate. Here we select the Gaussian doublet, whose hardware circuit is relatively easy to implement and consume lower energy. Although interference of narrow-band communication system is exist in the ground wireless communications, the higher order of the Gaussian is , the better Gaussian narrow pulse shape. But we do not need to consider interference to the other narrow-band communications in the coal face, for so far, wireless communications systems is basically non-existent in the mine's coal face. A second Gaussian pulse shape can be expressed as:
Here, is used to express the pulse width, Suppose that the input signal is , each bit is expressed by and its cycle is .After the channel encoder, every bit of the sequence kare repeated by N times. The code duration time is , so each bit is composed by N pulse width. If we suppose the pseudo-random sequence of sensors node k is , the length of the sequence is N, the duration of the code slice is The sequence of can be replaced by and the .The time coordinate of i-th bit in the frame date stream sent by sensor node k is .
when when .We can think in practical application.
When N=1, the UWB waves and waveform sent are shown in the Figure 5. Waveform in the Figure from the top to the end is the UWB waveform (the waveform of code “0” and the waveform “1”); the waveform generated when several code are send out; UWB waveform when get through band-pass filter.
B. The design of receiver system
The recerver structure is shown in figure 6. The signal received through the receiving antenna will go through the low noise amplifier and filter. Then the amplitude of the signal will be detected using tunnel diodes peak detector. Then we can get a pulse waveform which own longer code duration time when the signal detected after passing through high-pass filter and pulse stretch circuit. The last step is sample and judge.
In this design, we make use of the characters of the negative resistance region of tunnel diode. In this region, the current decreases as the voltage is increased. This negative resistance results in a very fast switching time. After detected by the tunnel and passed through high-pass filter and comparator, the signal can be stretched and delayed by RS latch. We can directly sampling and judge the signal, for the width of the signal we get is wider than we first received .The kind of the receiver is different from the method we previously used. Such as, literature 555 tell the technology about relevant receiver. As we know, the general complexity of the relevant receiver, which own integrator circuit and need precision clock, is much higher. Sometimes, general relevant receiver need matching filter according to channel model parameters, which can be required by channel estimation. Because channel characteristics under the mine well are extremely complex, the possibility to use channel estimation is small. In addition, the receiver does not need ADC conversion devices, for the comparator has fixed the position of the code “0”and”1”.Furthermore, the code stretched has a relative longer duration time, which do not need higher judgment pulse precision. Therefore, in the whole, the receiver does not need complicated channel estimation and ADC conversion devices, which make the energy-consumption and complexity much lower. But we can not ignore the disadvantage of this kind of receiver; it has bigger signal fading, lower detection efficiency.
C. Anti-noise performance of BPM
The propagation environment of the coal face belongs to dense multi-path. And the theoretical channel model we referred to is proposed by combining Saleh-Valenzu channel model, which is the foundation, and the characteristic of the coal face under the mine. Suppose the discrete pulse response is, r(t) is the signal received by one node. Then , .
The distance between receiver and transmitter is about 5-8 meters, which can satisfy the requirement of the distribution of the nodes in the coal face. The code duration time is 25ns, the duration time of GASSION waves is80ps. Under this conditions , we can get the curve, just as shown in the Figure 8.
In fact, when we carried out the experiment of BER test, the performance shown in Figure 8 is not easy to be seen because of the complexity of the channel character. According to the research result, the performance of anti-noise became abnormal, such as the fading of the signal is not in proportion to the distance and the amount of the path increase and decrease in a large scale.
Because the relevant coefficient of transmitted waves of the BPM is passive relevance when we adopted relevant receiver, the performance of anti-noise of BPM in relevant receiver is superior to PPM and OOK. Take the structure simplification of the receiver and the special character of the coal face into consideration, BPM is preferable in the whole，ever if the receiver we discussed in this paper is not superior to the relevant receiver on the anti-noise performance.
3. Conclusion
Because of the limited space of a non-uniform medium and the complicated channel character in the coal face, the choice of the model we send and receive the signal is extremely important. Taking into account that BPM do not have discrete spectrum when “0” and ”1” emerged in a same probability, if not, the amount of discrete spectrum is small, which is attractive to WSN system, for the low energy consumption is strongly required. Therefore, the communication mode can be used in the coal face. The Gaussian doublet, which can meet the requirement of FCC, is used to send the source signal. Take the complexity of the transmission channels, the receiver use non-coherent receiving method, use tunnel diode to detect signal, execute sampling and judgment after the signal go through the comparator and stretch circuit. This Method does not need channel estimation and ADC circuits, higher pulse sampling accuracy, which together decides the probability to simplify the structure of the receiver greatly. However, the method of receiving has a greater attenuation and bad anti-noise performance than the traditional relevant receiver. But let’s takes every important factor into consideration, the receiving method is suitable for the special environment of the coal face.
中文譯文
采煤工作面無(wú)線傳感器網(wǎng)絡(luò)物理層設(shè)計(jì)UWB技術(shù)
摘要
為了保證安全生產(chǎn)的工作面，監(jiān)測(cè)和監(jiān)視采煤機(jī)，刮板運(yùn)輸機(jī)，液壓支架，運(yùn)輸機(jī)械，破碎機(jī)等是必要的。目前，它是很難的電纜傳輸模式，以適應(yīng)變化的工作場(chǎng)所的采煤工作面。因?yàn)楦鞣N各樣的因素輸電線路被損壞和折斷，我們使用無(wú)線傳感器網(wǎng)絡(luò)（無(wú)線傳感器網(wǎng)絡(luò)） ，可以靈活的放置和可擴(kuò)展性來(lái)解決這一問(wèn)題。本文討論了設(shè)計(jì)中的無(wú)線傳感器網(wǎng)絡(luò)收發(fā)工作面與UWB技術(shù)。這種收發(fā)器有一些有用的優(yōu)勢(shì)，如成本低，能耗低，結(jié)構(gòu)簡(jiǎn)單，易于實(shí)現(xiàn)的設(shè)計(jì)，硬件，無(wú)需估計(jì)工作面通道的特點(diǎn)。然而，探測(cè)效率略低，但錯(cuò)誤率能滿足要求。
1 、導(dǎo)言
采煤工作面必須面對(duì)復(fù)雜地質(zhì)條件和工作條件差等問(wèn)題。為了確保安全生產(chǎn)的工作面，以監(jiān)測(cè)實(shí)時(shí)面對(duì)采煤機(jī)，刮板運(yùn)輸機(jī)械，液壓支架，轉(zhuǎn)載機(jī)，破碎機(jī)和其他大型設(shè)備是必要的。此外，我們必須監(jiān)測(cè)地面的壓力、天然氣、一氧化碳、灰塵及其他環(huán)境參數(shù)。同時(shí)，移動(dòng)語(yǔ)音和圖像通信是必需的。目前，信號(hào)監(jiān)測(cè)來(lái)自于采煤工作面的電纜。由于面臨正在持續(xù)不斷的煤炭開(kāi)采過(guò)程中，各種大型鋼鐵設(shè)備的采煤工作面需要推動(dòng)和不斷循環(huán)。空間的形狀是不斷變化在設(shè)備相對(duì)位置變化的同時(shí)。相應(yīng)地，通訊電纜是難以適用于不斷變化的工作場(chǎng)景，使輸電線路損壞或終結(jié)頻繁和使采煤工作面的移動(dòng)語(yǔ)音和圖像通信不可能。所有這些問(wèn)題都造成許多潛在安全生產(chǎn)的麻煩。我們認(rèn)為無(wú)線傳感器網(wǎng)絡(luò)（無(wú)線傳感器網(wǎng)絡(luò)）是可行的實(shí)施監(jiān)測(cè)和監(jiān)督的工作面，因?yàn)樗蟹胖渺`活，擴(kuò)展簡(jiǎn)單，移動(dòng)方便，自主調(diào)節(jié)等一些有用的特性。
2 、無(wú)線傳感器網(wǎng)絡(luò)體系結(jié)構(gòu)中的采煤工作面
傳感器網(wǎng)絡(luò)系統(tǒng)結(jié)構(gòu)的采礦工作面是如圖1所示。圖形中，該傳感器節(jié)點(diǎn)發(fā)送的信息的采集，通過(guò)一個(gè)或多個(gè)跳躍的群集節(jié)點(diǎn)，基站（匯節(jié)點(diǎn)）負(fù)責(zé)數(shù)據(jù)的收集，并傳輸給任務(wù)管理節(jié)點(diǎn)，通過(guò)了插槽網(wǎng)絡(luò)，任務(wù)管理節(jié)點(diǎn)負(fù)責(zé)綜合處理數(shù)據(jù)，并對(duì)傳感器網(wǎng)絡(luò)發(fā)出指示。隧道工作面是一個(gè)有限的空間。支架，采煤機(jī)，運(yùn)輸和其他大型金屬設(shè)備的布局和煤，巖石和其他媒體是一個(gè)非均勻受限制的空間，這一切使傳輸通道更加復(fù)雜，傳輸無(wú)線傳感器節(jié)點(diǎn)的信號(hào)衰退和多路徑的現(xiàn)象較為嚴(yán)重。這些是傳感器網(wǎng)絡(luò)在地面上不同的。因此，收發(fā)器的設(shè)計(jì)節(jié)點(diǎn)來(lái)說(shuō)尤其重要。目前，有三個(gè)主要技術(shù)的物理層的無(wú)線傳感器網(wǎng)絡(luò)：窄帶調(diào)制技術(shù)，擴(kuò)頻技術(shù)和超寬帶（ UWB ）技術(shù)。雖然UWB技術(shù)具有一定吸引力的優(yōu)勢(shì)，如低功率譜密度，低復(fù)雜系統(tǒng)，低靈敏度的頻道衰落，更好的安全性，等等?？紤]到工作面的優(yōu)勢(shì)和特點(diǎn)，我們已經(jīng)采用脈沖無(wú)線電超寬帶公司（ IR - UWB ）技術(shù)，原因是： 1 ） UWB技術(shù)消耗低功耗和低功率譜。低功耗，低成本和小尺寸是最重要的特點(diǎn)，無(wú)線傳感器網(wǎng)絡(luò)節(jié)點(diǎn)。窄帶調(diào)制技術(shù)，擴(kuò)頻調(diào)制技術(shù)，通常使用正弦載波，中頻和射頻電路中存在的系統(tǒng)，所以消耗更多的功耗比UWB技術(shù)。傳輸介質(zhì)在采煤工作面是不統(tǒng)一的，這導(dǎo)致比無(wú)線通信系統(tǒng)在地面上更多的傳輸損耗。因此，低功耗變得尤為重要。在采煤工作面，作為無(wú)線傳感器網(wǎng)絡(luò)節(jié)點(diǎn)呈現(xiàn)帶狀分布，節(jié)點(diǎn)只需要溝通鄰近節(jié)點(diǎn)。在無(wú)線傳感器網(wǎng)絡(luò)系統(tǒng)基礎(chǔ)上的UWB ，消費(fèi)較低的傳輸能量，能滿足要求，并避免干擾對(duì)方在窄帶通信節(jié)點(diǎn)。此外，低功耗和高穿透力幫助設(shè)計(jì)安全設(shè)備和傳輸救災(zāi)信號(hào)。 2 ）強(qiáng)大的抗干擾能力。在采煤工作面，電力及機(jī)械設(shè)備已分布較窄。當(dāng)設(shè)備啟動(dòng)或停止，電器火花可能會(huì)導(dǎo)致大量的電磁干擾。因此，良好的抗干擾能力是強(qiáng)烈需要在無(wú)線通信中應(yīng)用。3 ）良好的抗干擾多路徑的能力。采煤工作面有一定的內(nèi)在特征，如狹窄的空間，更多類型的媒體，多路密集的通道，而紅外UWB可以適用于這一復(fù)雜的環(huán)境與發(fā)揮自己的優(yōu)勢(shì)：窄脈沖寬度，脈沖持續(xù)時(shí)間的比例小，高多路徑?jīng)Q議，較強(qiáng)的抗多徑和衰落能力。 4 ）結(jié)構(gòu)簡(jiǎn)單。紅外超寬帶，如沒(méi)有調(diào)制和上/下變頻頻率，發(fā)射器結(jié)構(gòu)簡(jiǎn)單，能耗更低等特征，使其更加可以接受。根據(jù)復(fù)雜的節(jié)點(diǎn)和能耗納入考慮，紅外、UWB技術(shù)是非常適用于設(shè)計(jì)無(wú)線傳感器網(wǎng)絡(luò)物理層。因此，相比窄帶調(diào)制技術(shù)，擴(kuò)頻技術(shù)，無(wú)線通信系統(tǒng)基于UWB技術(shù)目前在能源消耗，強(qiáng)度，抗多徑和抗噪聲等等方面有著良好表現(xiàn)。
調(diào)節(jié)紅外UWB的主要是脈沖幅度放大調(diào)制（ OOK ） ， PPM和BPM（雙相位調(diào)制） ，但存在的脈沖幅度放大調(diào)制和PPM不僅使超寬帶脈沖信號(hào)難以滿足一定的頻譜要求，還減少用電，從而增加能源消耗。幾個(gè)紅外超寬帶信號(hào)的頻譜如圖2和圖3 所示。由于無(wú)線傳感器網(wǎng)絡(luò)系統(tǒng)需要低功耗，脈沖幅度放大調(diào)制經(jīng)常使用OOK調(diào)制方法，它結(jié)構(gòu)簡(jiǎn)單。但是OOK一直表現(xiàn)不佳的誤碼率（誤碼率） ，抗噪性能的BPM調(diào)制如反抖動(dòng)噪聲更好。工業(yè)標(biāo)準(zhǔn)將會(huì)加強(qiáng)，如果我們通過(guò)手冊(cè)的情況下，密集多徑環(huán)境的采煤工作面。因此，我們使用BPM形式收發(fā)器系統(tǒng)的工作面。
A、傳輸系統(tǒng)的設(shè)計(jì)
變送器采用的BPM形式如圖4所示。信號(hào)失真，干擾和噪音所帶來(lái)的特殊環(huán)境工作面需要編碼保護(hù)信道編碼交織模塊。數(shù)據(jù)傳輸速率的原始資料較低，這使得它在未模塊化時(shí)難以滿足FCC的要求。我們需要利用擴(kuò)頻碼轉(zhuǎn)換的原始資料，由較大的時(shí)間比轉(zhuǎn)換到一個(gè)較小的時(shí)間比率（納秒） 。然后，我們可以通過(guò)脈沖形成電路產(chǎn)生脈沖信號(hào)的BPM，可滿足要求FCC的要求。最后使用過(guò)濾器來(lái)優(yōu)化BMP進(jìn)一步放大信號(hào)的頻譜，并把它從天線發(fā)送出去。
該系統(tǒng)使用的高斯脈沖形式的UWB信號(hào)。如果波傳播的是一階導(dǎo)數(shù)的Rayleigh脈沖信號(hào)發(fā)出后，在理想的情況通過(guò)天線轉(zhuǎn)化為二階導(dǎo)數(shù)的高斯脈沖。此外，較低的順序高斯脈沖是，在更遠(yuǎn)的信號(hào)可以發(fā)送出相同的數(shù)據(jù)速率。在這里，我們選擇高斯雙，其硬件電路比較容易執(zhí)行和降低能源消耗。雖然干涉窄帶通信系統(tǒng)中存在地面無(wú)線通信，高階的高斯是更好地高斯窄脈沖形狀。但是，在采煤工作面我們并不需要考慮干擾其他窄帶通信，迄今為止，無(wú)線通信系統(tǒng)基本上在礦采煤工作面不存在的。第二高斯脈沖形狀可以表示為：
在這里是用來(lái)表示脈沖寬度，假設(shè)輸入信號(hào)是，每個(gè)位表示其周期。通道編碼后，每一個(gè)位的序列重復(fù)了N次。代碼持續(xù)時(shí)間，所以每比特由N脈沖寬度組成。如果我們假設(shè)的偽隨機(jī)序列的傳感器節(jié)點(diǎn)K是，長(zhǎng)度為N的順序，時(shí)間的長(zhǎng)短碼片序列可被和替代。時(shí)間坐標(biāo)的i-th框架傳感器節(jié)點(diǎn)K發(fā)出的。
當(dāng)當(dāng)，我們可以認(rèn)為在實(shí)際應(yīng)用中當(dāng)N = 1 時(shí)， UWB波和波形傳送顯示如圖5 。波形圖中從頂部到底的超寬帶波形是UWB波形（波形的代碼“ 0 ”和波形“ 1 ” ） ; 當(dāng)幾個(gè)代碼發(fā)送波形產(chǎn)生; 通過(guò)帶通濾波器獲得UWB脈沖。
B、接收系統(tǒng)的設(shè)計(jì)
接收結(jié)構(gòu)見(jiàn)圖6 。通過(guò)接收天線將通過(guò)低噪聲放大器和濾波器收到信號(hào)。然后振幅的信號(hào)將被檢測(cè)隧道二極管峰值檢測(cè)器查處。然后我們就可以得到一個(gè)長(zhǎng)持續(xù)時(shí)間代碼的脈沖波形 ,這個(gè)信號(hào)檢測(cè)經(jīng)過(guò)高通濾波和脈沖伸展的電路。最后一步是取樣和判斷。
在這個(gè)設(shè)計(jì)里，我們使用字符的負(fù)阻區(qū)的隧道二極管。在這一區(qū)域，目前的下跌是由于電壓增加。這種消極抵抗的結(jié)果導(dǎo)致非?？斓那袚Q時(shí)間。經(jīng)過(guò)檢測(cè)隧道和通過(guò)高通濾波器和比較器，信號(hào)可以延伸和延時(shí)遙感門(mén)閂。我們能直接取樣和判斷信號(hào)，因?yàn)樾盘?hào)的寬度，我們得到的比我們第一次收到更廣泛。接收的種類不同于我們以前使用的方法。例如，文獻(xiàn)555告訴有關(guān)接收器的技術(shù)。正如我們所知，一般相關(guān)接收器的本身集成的電路、精確時(shí)鐘的復(fù)雜性是要高得多。有時(shí)，一般要求信道估計(jì)有關(guān)接收機(jī)需要匹配濾波器據(jù)信道模型參數(shù)。由于地下煤層通道特性極其復(fù)雜，使用信道估計(jì)的可能性就很小了。此外，接收不需要的ADC轉(zhuǎn)換設(shè)備，因?yàn)楸容^器有固定的位置代碼“ 0 ”和“ 1 ” 。此外，拉伸的代碼有一個(gè)相對(duì)較長(zhǎng)的持續(xù)時(shí)間，這并不需要較高的判斷脈沖精度。因此，整體而言，接收器并不需要復(fù)雜的信道估計(jì)和ADC轉(zhuǎn)換裝置，使能源消耗和復(fù)雜性大大降低。但是，我們不能忽視的缺點(diǎn)是這種接收機(jī)有更大的信號(hào)衰減，較低的檢測(cè)效率。
C、BPM的抗噪聲性能
采煤工作面的傳播環(huán)境屬于密集多徑型。我們提到的信道模型的理論被建議和Saleh-Valenzu的渠道模式相結(jié)合，這是礦井采煤工作面的基礎(chǔ)和特征。假設(shè)離散脈沖響應(yīng)為，r(t)是所收到的信號(hào)的一個(gè)節(jié)點(diǎn)。那么, .
接收器和發(fā)射器之間的距離約5-8米，可滿足節(jié)點(diǎn)在采煤工作面的分布要求。代碼持續(xù)時(shí)間是25ns ，持續(xù)時(shí)間的GASSION波是80ps 。根據(jù)這一條件，我們可以得到的曲線，正如圖8中所示.
事實(shí)上，當(dāng)我們進(jìn)行了實(shí)驗(yàn)的誤碼率測(cè)試，因?yàn)槊簩油ǖ缽?fù)雜性的特點(diǎn)性能如圖8是不容易看到的。根據(jù)研究結(jié)果，抗噪聲性能變得異常，如衰落的信號(hào)和距離和路徑數(shù)額的大規(guī)模增加和減少不成比例的。
因?yàn)楫?dāng)我們采用相關(guān)的接收器，BMP傳輸波的相關(guān)系數(shù)為被動(dòng)關(guān)聯(lián)，高性能的抗噪聲的BPM相關(guān)接收機(jī)優(yōu)于PPM和OOK 。考慮到結(jié)構(gòu)簡(jiǎn)化的接收器和以及特殊性質(zhì)的采煤工作面，即使我們?cè)诒疚挠懻摰慕邮掌鞑粌?yōu)于有關(guān)接收機(jī)的抗噪聲性能，BMP從整體上看是較合適。
3 、結(jié)論
由于有限的空間的非均勻介質(zhì)和復(fù)雜的通道性質(zhì)的采煤工作面，我們發(fā)送和接收的信號(hào)的模式選擇是非常重要的。考慮到的BPM沒(méi)有離散頻譜時(shí)， “ 0 ”和“ 1 ”出現(xiàn)在相同的概率，如果沒(méi)有，離散頻譜的數(shù)額就小，對(duì)能耗低的強(qiáng)烈要求是無(wú)線傳感器網(wǎng)絡(luò)系統(tǒng)具有的吸引力。因此，通信方式可用于采煤工作面。利用高斯分布來(lái)發(fā)送信號(hào)的來(lái)源可滿足地層校正要求。采取復(fù)雜的傳輸信道，使用非相干接收的方法，使用隧道二極管檢測(cè)信號(hào)，信號(hào)經(jīng)過(guò)比較和伸展電路進(jìn)行取樣和執(zhí)行判斷。這種方法不需要信道估計(jì)和ADC電路，脈沖采樣精度較高，這些決定了簡(jiǎn)化接收機(jī)的結(jié)構(gòu)的可能性很大。然而，該方法比傳統(tǒng)的相關(guān)接收器得到了更大的衰減和壞的抗噪性能。但是讓我們考慮進(jìn)每一個(gè)重要的因素，接收方法適用于特殊環(huán)境的采煤工作面。