【導(dǎo)讀】最近幾年，無線局域網(wǎng)開始在市場中獨(dú)霸一方。越來越多的機(jī)構(gòu)發(fā)現(xiàn)無線局域網(wǎng)是傳統(tǒng)有線局域網(wǎng)不可缺少的好幫手，它可以滿足人們對移動、布局變動和自組網(wǎng)絡(luò)的需求，并能覆蓋難以鋪設(shè)有線網(wǎng)絡(luò)的地域。無線局域網(wǎng)是利用無線傳輸媒體的局域網(wǎng)。就在前幾年，人們還很少使用無線局域網(wǎng)。原因包括成本高、數(shù)據(jù)率低、職業(yè)安全方面的顧慮以及需要許可證。隨著這些問題的逐步解決，無線局域網(wǎng)很快就開始流行起來了。在20世紀(jì)80年代后期出現(xiàn)的無線局域網(wǎng)早期產(chǎn)品都是作為傳統(tǒng)有線局域網(wǎng)替代品而問世的。無線局域網(wǎng)可以節(jié)省局域網(wǎng)纜線的安裝費(fèi)用，簡化重新布局和其他對網(wǎng)絡(luò)結(jié)構(gòu)改動的任務(wù)。但是，無線局域網(wǎng)的這個動機(jī)被以下一系列的事件打消。大多數(shù)老建筑中已經(jīng)鋪設(shè)了足夠的3類電纜，而許多新建筑里則預(yù)埋了5類電纜。因此，用無線局域網(wǎng)取代有線局域網(wǎng)的事情從來沒有發(fā)生過。在以上這些情況下，無線局域網(wǎng)向人們提供了一個有效且更具吸引力的選擇。

　　

【正文】 transmission power is very low. Communications speed in 250Kbit ~ between 10Mbit/SEC. In 250Kbit/SEC transmission speeds can ensure as munication 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 transmission dominant.Ultrawideband (UWB) technology is initially applied to develop the radar oriented, it is generally thought that it belongs to a kind of carrierless munications technologies. February 2002, the United States the FCC formally its suspension. Currently ultrawideband (UWB) technology is being integrated into the family cinema and portable products, mainly used for video and audio signal of wireless transmission. Ultrawideband (UWB) since when published has been regarded as bluetooth technology substitute, and other wireless technologies such as WLAN, bluetooth etc pared ultrawideband (UWB), with low power waste, high bandwidth and low plexity, the advantages of low cost, can pletely satisfy short family entertainment application requirements. ultrawideband performance characteristics.Uwb wireless munication is a very different to the traditional technology of wireless munication 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 antijamming performance UWB signal, the launch will be weak radio pulse signal scattered on the broad 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 a, IEEE b and bluetooth,pared to the same code speed conditions, the UWB has a strong antijamming.2) transmission rate is high UWB with very wide frequency bandwidth for highspeed 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 megabit per second, is expected to 100 times higher than bluetooth, also can prep above IEEE and IEEE . 3) with very wide bandwidth UWB use of bandwidth in 1GHz above, up to a few ji hz and can and current narrowband munication system working at the same time and not interfere with each other. This in frequency resource of increasingly scarce today opened up a new timedomain 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 (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 lasted for a very short time, is in monly ns ~ ns between, have very low accounted for empty factor, the system power consumption can be done very low, in high speed munications system when consume only for hundreds of muon W ~ dozens mW. At the same time because ultra wideband (UWB) technology of spread spectrum signal processing is relatively large, even if the gain USES low gain omnidirectional antenna with emission, also can use less than 1mW launch power realization thousands of meters of munication. 6) good safety UWB safety performance in two aspects: one is to adopt the 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 pletely submerged in noise, be intercept probability is small, be detection probability is low, with traditional receiver cannot receive.2 Wi Fi Wi Fi technology introduction Wi Wireless Fidelity, Wireless Fi (highfidelity) is a kind of Wireless munication protocol, official name is b. Wi Fi is Ethernet a wireless expand, Wi Fi network can use to interconnect puter links on the Internet. Wi Fi network in no license and 5 gigabit bandwidth management, Hz radio data rate can reach 11Mbps ( b) ~ 54Mbps ( a), or include the above two bands of products. If the user is located in an access point theoretically around certain region, can with highest 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 problems. 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 send 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 telemunication, CNC, mobile are very 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. Wi Fi technical superiority 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) wider LAN coverage Based on bluetoot