【正文】 from the point of view of network security and QoS mechanisms, WiMax, and 3G technology in this respect have done quite good, perfect, the rest there is a big problem.Wireless technology and ProspectsAt present, with a high transfer rate, high bandwidth, high reli。 WiMax, technology, 3G technology, LMDS technology, MMDS technology, trunking munication belongs to the metropolitan area network access technology, coverage 1km to 54km ranging from satellite munications, pointtopoint microwave belongs to the WAN technology, typically used for the construction of munication backbone network.Transfer rate from the point of view, pointtopoint microwave and satellite munication belongs to the trunk transmission technology, different rate changes, while the rest of the technology are access technology, the only 3G technology minimum access speed is only 384k, while the The rest of the technology are the dozens of M or even hundreds of M the rate.Point of view, WiFi technology, WiMax technology of WMN, the 3G technology using the latest modulation technique OFDM modulation, the rest of the technology were not using OFDM technology.Antenna technology from the point of view, only the 3G and WiMax technology uses MIMO technology, while others were not using MIMO technology to WiMax, and 3G technology to support nonlineofsight transmission。 wireless router (WR)。s outer space.4 wireless power technology prospectsWireless power transmission as a stateoftheart technology is generally used in special occasions, has broad application prospects. to difficult to set up lines or dangerous areas supply electricityThe mountains, forests, deserts, islands and other land stations often encountered in the erection of power lines difficult problem, and work in these areas, border posts, radio navigation, satellite monitoring stations, astronomical observation points need to live and work in electricity, The wireless transmission can supplement the lack of electricity. In addition, wireless transmission technology can give nomadic and other dispersion village transformer power supply and to for the exploitation of radioactive minerals, the robotpowered logging.Fourth, the wireless technology is integratedThe plementary nature of wireless munications technology is being increasingly clear. This was reflected in the different access technologies have different coverage, different application areas, different technical characteristics, different access rates. Solve the WAN seamless coverage and mobility needs of strong roaming 3G, WLAN, to resolve the more highspeed data access in the middle distance, UWB can achieve close ultrahighspeed wireless access. 1 IntroductionPower Communication Network39。s Long Island Wardenclyffe tower, is a plex electromagnetic oscillator, conceived it to be able to power transmission to any corner of the world, Tesla use of this tower to achieve the resonance of the Earth and the ionosphere.In May 2001, the French National Centre for Scientific Research 皮格努萊特 microwave wireless transmission of electrical energy to light up the 40m outside a 200W light bulb. Subsequently, in 2003 built on the island of 10kW experimental microwave transmission equipment, has begun to frequency close to 1km Grande Basang Village for pointtopoint wireless power.In 2005, the City University of Hong Kong Department of Electronic Engineering, Professor Xu Shuyuan successfully developed a wireless battery charging platform , but its use still want products and charger contacts.In October 2006, Japan exhibited a wireless power transmission system. The output power of this system is 7V, 400mA, send and receive coil spacing is 4mm, the transmission efficiency of 50% for the phone to fast charge.In June 2007, the Massachusetts Institute of Technology assistant professor of physics the Marin 索爾賈希克 research team within a short distance wireless power transmission. They give a 60 cm diameter coil is energized, and 6 feet (about meters) outside the connection in another coil 60 watt light bulb lit up. The principle of this Marin called WiTricity technology magnetically coupled resonance.In September 2008, the papers published by the North American Electric Workshop, they have been successful in Nevada Lightning Laboratory 800W power with a wireless way of transmission to 5m far distance.In October 2009, Nara, Japan, plugin hybrid bus wireless charging experiment. Powered coil buried in the concrete charge, the car onto the charge, the vehicle coil at the powered coil will be able to start charging.3 the basic principles of wireless power transmission of electromagnetic induction shortrange transmissionThe phenomenon of electromagnetic induction is the most significant discoveries in electromagnetism, one of which shows the linkages and transformation between the electric and magnetic phenomena. Electromagnetic induction is the basic principles of electromagnetism, the transformer is to use the basic principle of electromagnetic induction to work. Magnetic coupling to transfer energy between the basic principles of electromagnetic induction distance power transmission shown in Figure 1, the transmitting coil L1 and the receiving coil L2. The coil L1 through the alternating current, the current in the surrounding medium, the formation of an alternating magnetic field, the EMF generated in the coil L2 can supply to the mobile device or to charge the battery. of electromagnetic coupling resonance mediumrange transmissionThe mediumrange wireless power transmission is the radio frequency electromagnetic wave or nonradiative resonant magnetic coupling form of power transmission. It is based on electromagnetic resonance coupling principle, the use of nonradiative magnetic field to achieve efficient power transmission. Electronics theory, when an alternating current through the conductor, the conductor around the formation of alternating electromagneti