【正文】 limit the signaltonoise ratios in these channels and thus the transmission range. In our recent work in [6], we have argued that it is now being feasible to achieve high data rates over large transmission ranges in mobile optical wireless munications using camera receivers through a concept what we call ”visual MIMO”. In this concept, optical transmissions by an array of light emitting devices are received by an array of photodetector (pixels) elements of a camera. The pixels in a camera can essentially be viewed as an array of highly directional receive elements. Such a structure allows allows reducing interference and noise from other light sources in the channel. Such a system offers a degree of freedom in selecting and bining a subset of the receiver elements that receive a strong signal from the transmitter and thus achieve large SNRs. This may be very similar to the antenna selection in RFMIMO but will incur lesser overhead and nonplex processing at the camera receiver as the processing can be done in software using image processing and puter vision algorithms [6]. However, the tradeoffs in the visual MIMO system, are a limited receiver sampling frequency and strong lineofsight (LOS) requirements. We already showed in [6] that usingvisual MIMO it is possible to achieve considerable data rates over large transmission ranges with just a single transmitting element. Using MIMO techniques such as ”multiplexing” to send independent streams of bits using the multiple elements of the light transmitter array and recording over a group of camera pixels can further enhance the data rates. On the other hand the system could send the same information on all the transmit elements of the array and use diversity bining at the camera to achieve large transmission ranges due to the SNR gain. Though the multiplexing and diversity techniques are similar in concept to those in RF MIMO systems [11]the visual MIMO channel with very different characteristics attributes certain unique behavior to the MIMO gains in these systems.In visual MIMO the perspective distortions in the visual channel dominate over some of the important properties of a RF wireless channel such as distance based attenuation and multipath fading. Though perspective distortions in visual channels are primarily distance dependent visual MIMO channels induce perspective distortions in the image even if the transmitter and receiver are aligned at an angle with respect to each other. Two images which are clearly separated in the image plane may look overlapped when viewed from an angle. Such distortions can depreciate the signal quality and the detection capability leading to errors and thus reduction in the data rates. Further lens blur (typically due to focus imperfection or jerks while capturing the image) also can significantly depreciate the image quality and thus reduce the information capacity. In this paper we will detail how MIMO techniques such as multiplexing and diversity are characterized based on the effect of perspective distortions in the visual MIMO channel. Based our channel model we will derive the analytical channel capacity of the visual MIMO channel and using the same we illustrate the significance of parameters such as distance, viewing angle and blur in characterizing multiplexing and diversity in visual MIMO.This paper is structured as follows。Linux 內(nèi)核是支持 WIFI 無線網(wǎng)絡(luò)通信的，但是需要對其進(jìn)行配置，才能使用。本文選用 Ateml 公司的工業(yè)級 ARM 芯片 AT91SAM9G45，該處理器 BootLoader 和 Kernel 需要使用 Ateml 公司的 SAMBA 軟件通過 USB 口進(jìn)行燒寫，而 Rootfs 是通過網(wǎng)口進(jìn)行燒寫。Linux 操作系統(tǒng)至少具有三部分：BootLoader（引導(dǎo)系統(tǒng)）、Kernel（內(nèi)核）、Rootfs（根文件系統(tǒng)）。Linux 是一個跨平臺的操作，它適應(yīng)于多種處理器，到目前為止，它可以支持幾十種處理器，所以它的移植性非常好。Linux 的內(nèi)核小、執(zhí)行效率高，非常容易裁剪定制，其系統(tǒng)內(nèi)核最小只有約幾百 KB。 嵌入式 Linux 是在 Linux 的基礎(chǔ)演變而成的，專門應(yīng)用于嵌入式設(shè)備中。本文設(shè)計的系統(tǒng)所使用的 WIFI 無線網(wǎng)卡是 TOTOLINK 公司的 N200UA，這款 WIFI無線網(wǎng)卡的優(yōu)點(diǎn)在于外置天線，我們可以根據(jù)需要選用特殊形狀以及高增益的天線。兩路 USB 接口控制芯片，選用雙 USB 電源開關(guān)芯片 SP2526A2USB 和兩片 USB控制芯片 USBLC62P6 為系統(tǒng)提供兩路 USB 接口，一路用于與無線模塊進(jìn)行通信，一路用于測試數(shù)據(jù)的有限讀取。動態(tài)存儲器，選用 National Semiconductor 公司 64M DDR2 存儲器，工作溫度在系統(tǒng)中使用兩片，總?cè)萘窟_(dá) 128M，大幅提高 ARM 處理器的運(yùn)算效率。將 ARM 作為節(jié)點(diǎn)的主控制器可全面提高節(jié)點(diǎn)性能。而且易擴(kuò)展，傳輸可靠，組網(wǎng)便捷。WIFI技術(shù)傳輸速率快，采用直接序列擴(kuò)頻技術(shù)，提供很高的傳輸速率，具有高移動性，在無線局域網(wǎng)覆蓋范圍內(nèi)，地理位置的限制進(jìn)行任意移動，各個節(jié)點(diǎn)可以不受覆蓋范圍廣，WIFI 的覆蓋范圍半徑在 150m，但通過中繼能實(shí)現(xiàn)幾千米的通信距離。 WIFI 全稱 Wireless Fidelity[14]，又稱 標(biāo)準(zhǔn)，是由一個名為“無線以太網(wǎng)相容聯(lián)盟”（Wireless Ethernet Compatibility Alliance, WECA）的組織所發(fā)布的業(yè)界術(shù)語，中文譯為“無線相容認(rèn)證”。傳感器模塊通過傳感器觸頭感知外界信息，獲取傳感數(shù)據(jù)；無線通信模塊通過天線與其他節(jié)點(diǎn)通信完成數(shù)據(jù)交換。接收數(shù)據(jù)觀察者一般為終端計算器或者其它監(jiān)控設(shè)備，甚至是連接外部世界的萬維網(wǎng)，數(shù)據(jù)采集觀察者通過主動查詢或者被動接收的方式分析無線傳感器網(wǎng)絡(luò)的數(shù)據(jù)信息，并最終完成數(shù)據(jù)的分析、應(yīng)用。覆蓋環(huán)境感知對象是指節(jié)點(diǎn)判定為價值有效的監(jiān)測目標(biāo)，可以是監(jiān)測區(qū)域的聲音、光線、溫度、震動等等，節(jié)點(diǎn)傳感器通過數(shù)據(jù)采集、轉(zhuǎn)化為系統(tǒng)可以識別的信息資源，并最終上傳給接收數(shù)據(jù)觀察者。無線傳感器網(wǎng)絡(luò)節(jié)點(diǎn)是無線傳感器網(wǎng)絡(luò)最基本、最核心的組成部分，網(wǎng)絡(luò)節(jié)點(diǎn)主要集成相應(yīng)微型傳感器、數(shù)字信號處理器、無線通信模塊等功能單元。第16周 準(zhǔn)備答辯。第10周～第12周 調(diào)試測試 電路調(diào)試 軟件調(diào)試。第5周～第6周 擬定系統(tǒng)方案，進(jìn)行系統(tǒng)總體設(shè)計。進(jìn)行基于RT3070芯片的網(wǎng)卡驅(qū)動移植，最后設(shè)計WIFI的驅(qū)動程序，進(jìn)行WIFI聯(lián)網(wǎng)。 選用ARM芯片AT91SAM9G45作為處理器， 選用AD7492作為A/D轉(zhuǎn)換器，選用FIFO CY7C4261作為緩存器，F(xiàn)PGA芯片選用XC3S500E， WIFI 芯片選用 RT3070。然后設(shè)計 WIFI 無線傳感器節(jié)點(diǎn)的硬件結(jié)構(gòu)。3. 采取的研究路線首先查閱大量關(guān)于無線傳感器的相關(guān)文獻(xiàn)，選用WIFI技術(shù)作為無線傳感器網(wǎng)絡(luò)的通信技術(shù)。?通信協(xié)議依然廣泛，網(wǎng)絡(luò)協(xié)議標(biāo)準(zhǔn)化較低。 3）目前技術(shù)存在的問題 ?無線傳感器網(wǎng)絡(luò)即便節(jié)點(diǎn)靈活，可減硬件成本，但依然受有限能量的制約，優(yōu)勢未能充分發(fā)揮。加州大學(xué)伯克利分校研究了傳感器網(wǎng)絡(luò)的數(shù)據(jù)查詢技術(shù),提出了實(shí)現(xiàn)可動態(tài)調(diào)整的連續(xù)查詢處理方法和管理傳感器網(wǎng)絡(luò)上多查詢方法,并研制了一個感知數(shù)據(jù)庫系統(tǒng)TinyDB。麻省理工學(xué)院已經(jīng)著手研究超低功耗無線傳感器網(wǎng)絡(luò)的問題,試圖解決超低功耗無線傳感器系統(tǒng)的方法和技術(shù)問題。加州大學(xué)洛杉肌分校開發(fā)了一個無線傳感器網(wǎng)絡(luò)和一個無線傳感器網(wǎng)絡(luò)模擬環(huán)境,用于考察傳感器網(wǎng)絡(luò)各方面的問題。國家對傳感器網(wǎng)絡(luò)的研究也非常重視,國家自然科學(xué)基金委員會從2003年起開始設(shè)立了無線傳感器網(wǎng)絡(luò)相關(guān)研究課題,國家的“863”項目、國家自然科學(xué)基金項目、各省區(qū)的自然科學(xué)基金項目的課題中都有相當(dāng)?shù)谋壤沁M(jìn)行無線傳感器網(wǎng)絡(luò)研究的。除此之外，國家 863 計劃、973 計劃也對無線傳感器網(wǎng)絡(luò)的研究進(jìn)行了相關(guān)規(guī)劃。WIFI 無線傳感器網(wǎng)絡(luò)具有傳輸速率快、組網(wǎng)便捷等優(yōu)點(diǎn)。功耗小，電池供電，網(wǎng)絡(luò)節(jié)點(diǎn)一般都能工作3年左右，甚至更長。組網(wǎng)不需要任何固定的網(wǎng)絡(luò)設(shè)備，傳感器節(jié)點(diǎn)通過分布式網(wǎng)絡(luò)協(xié)議形成自組織網(wǎng)絡(luò)，能夠自動調(diào)整來適應(yīng)節(jié)點(diǎn)的變化，網(wǎng)絡(luò)中的節(jié)點(diǎn)可以快速、自動的組成一個獨(dú)立的網(wǎng)絡(luò)。能根據(jù)實(shí)際情況設(shè)計無線傳感器網(wǎng)絡(luò)的規(guī)模，有利于應(yīng)用范圍的擴(kuò)展。將來人們將通過遍布周圍的傳感器網(wǎng)絡(luò)直接感知客觀世界，極大的改變?nèi)藗冋J(rèn)識世界、改造世界的能力。而傳感器技術(shù)在科技發(fā)展中卻舉足輕重。長春理工大學(xué)畢業(yè)設(shè)計任務(wù)書題目名稱：基于WIFI的無線傳感器采集系統(tǒng)設(shè)計 學(xué)生姓名：華丹陽 起止日期：~題目要求(包括主要技術(shù)參數(shù)):1． 題目內(nèi)容：設(shè)計基于WIFI技術(shù)的傳感器信息采集系統(tǒng)，實(shí)現(xiàn)數(shù)據(jù)信息的網(wǎng)絡(luò)發(fā)布2． 具體要求及技術(shù)參數(shù)： ； ； 。 指導(dǎo)教師簽字 系主任簽字 年 月 日 開題報告本課題研究