1、超寬帶技術與其它短距離無線通信技術的比較隨著個人通信消費電子產業的迅猛發展，短距離無線通信領域的各種新技術、新方法層出不窮，朝著更快、更方便、更安全有效等方面進行發展。新的技術在 Intel 接入、信息家電、移動辦公、工業化等各個領域得到了廣泛的運用。其中，超寬帶（Ultra Wide Band，UWB）技術是在 20世紀90 年代以后發展起來的一種具有巨大發展潛力的新型無線通信技術，被列為未來通信的十大技術之一 。1 超寬帶無線通信 1.1 超寬帶技術簡介 UWB（Ultra Wideband，超寬帶）技術是目前正被廣泛研究的一種新興無線通信技術，現在已經成為高速無線個人網 （WPAN）的首

2、選技術。UWB是指信號帶寬大于 500MHz或者是信號帶寬與中心頻率之比大于25% 的通信技術。與常見的通信方式使用連續的載波不同，UWB 中使用的無線信號中心頻率為 4.1GHz，帶寬為 1.4GHz，頻譜范圍很寬，但是發射功率非常低。通信速度在250Kbit10Mbit/秒之間。在 250Kbit/秒的傳輸速度下可確保 30m的通信距離。在短距離（13m 以下）有很大優勢，最高傳輸速度可達 1Gb/S。而傳統的窄帶技術在長距離、低速傳輸具有優勢。 超寬帶（UWB）技術最初是面向雷達應用來開發的，一般認為它屬于一種無載波通信技術。2002 年 2 月，美國聯邦通信委員會（FCC）正式將其解禁

3、。目前超寬帶（UWB）技術正被整合進家庭影院和便攜式產品，主要用于視頻和音頻信號的無線發送。寬帶（UWB）自問世后一直被看作是藍牙技術的替代品，與其他無線技術如 WLAN 、藍牙等相比，超寬帶（UWB）具有低功耗、高帶寬、低復雜度、低成本的優點，完全可以滿足短距離家庭娛樂應用需求。 1.2 超寬帶性能特點。超寬帶無線通信是一種與傳統技術有很大不同的無線通信技術。它能夠實現無線局域網LAN 和個人區域網PAN 中無線接口的互聯和接入。UWB具有以下特點： 1）抗干擾性能強 UWB信號，在發射時將微弱的無線電脈沖信號分散在寬闊的頻帶中，輸出功率甚至低于普通設備產生的噪聲。接收時將信號能量還原出來，

4、在解擴過程中產生擴頻增益。因此，與 IEEE 802.11a、IEEE 802.11b 和藍牙相比，在同等碼速條件下，UWB具有更強的抗干擾性。 2）傳輸速率高 UWB 以非常寬的頻率帶寬來換取高速的數據傳輸，并且不單獨占用現在已經擁擠不堪的頻率資源，而是共享其他無線技術使用的頻帶。其數據速率可以達到幾十兆比特每秒到幾百兆比特每秒，有望高于藍牙100倍，也可以高于IEEE 802.11a和 IEEE 802.11b。 3）帶寬極寬 UWB 使用的帶寬在 1GHz 以上，高達幾吉赫茲，并且可以和目前的窄帶通信系統同時工作而互不干擾。這在頻率資源日益緊張的今天開辟了一種新的時域無線電資源。 4）頻

5、譜利用率高，系統容量大 因為不需要產生正弦載波信號，可以直接發射沖激序列，因而 UWB系統具有很寬的頻譜和很低的平均功率，有利于與其他系統共存，從而提高頻譜利用率，帶來了極大的系統容量。 5）功率低 UWB系統使用間歇的脈沖來發送數據，脈沖持續時間很短，一般在0.20ns1.5ns 之間，有很低的占空因數，系統耗電可以做到很低，在高速通信時系統的耗電量僅為幾百 W幾十 mw。同時由于 UWB系統信號的擴頻處理增益比較大，即使采用低增益的全向天線發射，也可使用小于 1mW 的發射功率實現幾千米的通信。 6）安全性好 UWB 安全性表現在兩方面：一方面是采用跳時擴頻，接收機只有已知發送端擴頻碼時才

6、能解出發射數據；另一方面是系統的發射功率譜密度極低。有用信息完全淹沒在噪聲中，被截獲概率很小，被檢測的概率也很低，用傳統的接收機無法接收。 2 Wi-Fi 2.1 Wi-Fi技術簡介 Wi-Fi（Wireless Fidelity,無線高保真）也是一種無線通信協議，正式名稱是IEEE802.11b。 Wi-Fi 是以太網的一種無線擴展，Wi-Fi 網絡可以使用來互連電腦鏈接上互連網。Wi-Fi 網絡在無執照的 2.4 和 5 千兆 Hz 的無線電頻帶經營，數據速率可達 11Mbps（802.11b）54Mbps（802.11a），或包含以上兩條頻帶的產品。理論上只要用戶位于一個接入點四周的一定

7、區域內，就能以最高約 11Mb/s 的速度接入Web。但實際上，如果有多個用戶同時通過一個點接入，帶寬被多個用戶分享。 由于 Wi-Fi 使用電波作為傳送媒介， 資料包被截取的可能性高， 這成為用戶所擔心問題。現在 Wi-Fi 產品利用WED（Wired Equivalent Privacy）技術作資料加密之用。然而，其保密的效能卻倍受質疑，支援新一代加密方式的 Wi-Fi 產品亦相繼出現。雖然 Wi-Fi 在數據安全性方面比藍牙技術要差一些，但在電波的覆蓋范圍方面卻略勝一籌，可達 100 m 左右。 Wi-Fi 可以提供熱點覆蓋、低移動性和高數據傳輸速率， 無線接入和高速傳輸是Wi-Fi 技

8、術的主要特點。國內的電信、網通、移動都非常關注 Wi-Fi 技術的發展和應用。基于熱點的接入服務曾經一度被看成是對3G的巨大沖擊， 但Wi-Fi技術傳輸距離短和信號穿透能力差的特點同樣也是不可克服的。 2.2 Wi-Fi技術的優勢 近幾年，WAP 的數量呈迅猛增長，無線網絡的方便與高效使其得到迅速的普及。無論是無線城市的建設，還是企事業單位局域網的開通，還是手機的 Wi-Fi 功能，都與Wi-Fi 技術自身的優勢是分不開的： 1）較廣的局域網覆蓋范圍 基于藍牙技術的電波覆蓋范圍非常小，半徑大約只有 15m，而 Wi-Fi 的半徑則可達100 m，可以覆蓋整棟辦公大樓； 2）傳輸速度快 Wi-F

9、i 技術傳輸速度非常快，可以達到 11Mbps（802.11b）或者 54Mbps （802.11a），適合高速數據傳輸的業務； 3）無需布線 Wi-Fi 最主要的優勢在于不需要布線，可以不受布線條件的限制，因此非常適合移動辦公用戶的需要。在機場、車站、咖啡店、圖書館等人員較密集地方設置“熱點” ，并通過高速線路將因特網接入上述場所。用戶只要將支持無線 LAN的筆記本電腦或PDA拿到該區域內，即可高速接入因特網； 4）健康安全 IEEE802.11規定的發射功率不可超過 100 毫瓦，實際發射功率約 6070毫瓦，而手機的發射功率約 200毫瓦1瓦間，手持式對講機高達5瓦。與后者相比，Wi-F

10、i 產品的輻射更小。 3 結論 每一種無線通信方式都有其獨特之處，超寬帶技術傳輸速率高，Wi-Fi 技術覆蓋范圍廣。隨著無線通信技術的發展，人們對高速短距離無線通信的要求越來越高，超寬帶技術、Wi-Fi 技術都有著廣泛的發展前景。1 UWB technology and other short-range wireless communications technology is comparedAs personal communication consumer electronics industry in the rapid development, short-range wirele

11、ss communication field of all kinds of new skills ,art, new methods to emerge in endlessly, toward faster and more convenient and more safe and effective etc. The new technology in the development of the Intel access, information home appliances, mobile office, industrialization and other fields has

12、 been widely used. Among them, ultra-wideband (UWB) Wide Band, the mk-ultra technology is in after 1990's developed a kind of with high potential new wireless communication technology, it was listed as one of the ten future communication technology.1 uwb wireless communication 1.1 ultra-wideband

13、 technology introduction UWB (the mk-ultra Wideband, ultra-wideband) technology is currently has been widely studied a new wireless communication technology, it has become a high-speed wireless personal nets (WPAN first choice of the technology. UWB refers to the signal bandwidth than 500MHz or is t

14、he signal bandwidth and center frequency ratio is more than 25% of communications technologies. With the common use of continuous carrier communication mode is different, use of UWB wireless signals center frequency 4.1 GHz, bandwidth of 1.4 GHz, spectral range is very wide, but transmission power i

15、s very low. Communications speed in 250Kbit between 10Mbit/SEC. In 250Kbit/SEC transmission speeds can ensure as communication distance. In short (13m below) a has great advantage, highest transmission speed can reach 1Gb/S. While the traditional narrowband technology in long distance, low speed tra

16、nsmission dominant.Ultra-wideband (UWB) technology is initially applied to develop the radar oriented, it is generally thought that it belongs to a kind of carrierless communications technologies. February 2002, the United States the FCC formally its suspension. Currently ultra-wideband (UWB) techno

17、logy is being integrated into the family cinema and portable products, mainly used for video and audio signal of wireless transmission. Ultra-wideband (UWB) since when published has been regarded as bluetooth technology substitute, and other wireless technologies such as WLAN, bluetooth etc compared

18、 ultra-wideband (UWB), with low power waste, high bandwidth and low complexity, the advantages of low cost, can completely satisfy short family entertainment application requirements. 1.2 ultra-wideband performance characteristics.Uwb wireless communication is a very different to the traditional tec

19、hnology of wireless communication technology. It can realize the wireless LAN LAN and personal regional network PAN wireless Internet and access interface. UWB has the following features:1) strong anti-jamming performance UWB signal, the launch will be weak radio pulse signal scattered on the broad

20、band, output power and even lower than ordinary equipment of the noise. Received will signal energy reduction out, in the solution enlarge produced during spread spectrum gain. Therefore, and IEEE 802.11 a, IEEE 802.11 b and bluetooth,compared to the same code speed conditions, the UWB has a strong

21、anti-jamming.2) transmission rate is high UWB with very wide frequency bandwidth for high-speed data transmission, and not alone occupy now already crowded frequency resource, but sharing other wireless technology using frequency band. The data rate can reach dozens megabit per second to hundreds of

22、 megabit per second, is expected to 100 times higher than bluetooth, also can prep above IEEE 802.11a and IEEE 802.11b . 3) with very wide bandwidth UWB use of bandwidth in 1GHz above, up to a few ji hz and can and current narrowband communication system working at the same time and not interfere wi

23、th each other. This in frequency resource of increasingly scarce today opened up a new time-domain radio resources. 4) spectrum is high efficiency, the system of large capacity Because it does not need to produce sine carrier signal that can be directly launch impulse sequence, thus ultra wideband (

24、UWB) technology has a wide spectrum and very low average power, which is beneficial to coexist with other systems, so as to improve the frequency spectrum utilization rate, which brings a lot of system capacity. 5) low power Ultra wideband (UWB) technology use intermittent pulses to send data, pulse

25、 lasted for a very short time, is in commonly 0.20 ns 1.5 ns between, have very low accounted for empty factor, the system power consumption can be done very low, in high speed communications system when consume only for hundreds of muon W dozens mW. At the same time because ultra wideband (UWB) tec

26、hnology of spread spectrum signal processing is relatively large, even if the gain USES low gain omni-directional antenna with emission, also can use less than 1mW launch power realization thousands of meters of communication. 6) good safety UWB safety performance in two aspects: one is to adopt the

27、 jump spread spectrum, receiver only known the sender spread spectrum yards to work out emission data; On the other hand is the transmission power spectral density is extremely low. Useful information completely submerged in noise, be intercept probability is small, be detection probability is low,

28、with traditional receiver cannot receive.2 Wi - Fi 2.1 Wi - Fi technology introduction Wi - Wireless Fidelity, Wireless Fi (high-fidelity) is a kind of Wireless communication protocol, official name is IEEE802.11 b. Wi - Fi is Ethernet a wireless expand, Wi - Fi network can use to interconnect compu

29、ter links on the Internet. Wi - Fi network in no license 2.4 and 5 gigabit bandwidth management, Hz radio data rate can reach 11Mbps (802.11 b) 54Mbps (802.11 a), or include the above two bands of products. If the user is located in an access point theoretically around certain region, can with highe

30、st about 11Mb/s faster access Web. But in fact, if there are multiple users at the same time through a point access, bandwidth by multiple users to share. Because Wi - Fi use waves as transmission medium, material package to be intercepted tall, this be the possibility of users are worried about pro

31、blems. Now Wi - Fi product use Wired Equivalent without (WED) technology data encryption purposes. However, its performance is highly confidential scepticism, support the new generation encryption method Wi - Fi products also arise. Although Wi - Fi in data security than bluetooth technology will se

32、nd some, but in waves coverage was slightly better, can amount to 100 m or so. Wi - Fi may provide hot coverage, low mobility and high speed of data transmission, wireless access and transmission with high speed is Wi - Fi technical main characteristics. Domestic telecommunication, CNC, mobile are v

33、ery concerned Wi - Fi technology development and application. Based on the hotspot access service once considered the huge impact on 3G, but Wi - Fi technology transmission distance is short and signals penetrate the characteristics of poor ability also insurmountable. 2.2 Wi - Fi technical superior

34、ity In recent years, the number of WAP at a rapid pace, wireless network convenience and efficient make its rapid popularization. Whether wireless urban construction, or business unit of LAN opening, or mobile phones Wi - Fi function, all with Wi - Fi technical advantages of itself is not divided: 1

35、) wider LAN coverage Based on bluetooth radio coverage is very small, radius, and only about 15m Wi - Fi radius criterion of up to 100 m, can cover whole building office building, 2) transmission speed Wi - Fi technology transmission is very fast, can achieve 11Mbps (802.11 b) or 54Mbps (802.11 a), suitab