Wifi技术资料(英文版)

Aircell to Boost In-flight Wi-Fi SpeedBy Stephen Lawson, IDG News Mar 10, 2011 8:30 amIn-flight Wi-Fi provider Aircell unveiled plans for its second generation of wireless links from aircraft to the Internet on Wednesday, promising higher capacity and the capability to offer its service outside the U.S.Aircell equips airliners and business jets with in-cabin Wi-Fi systems and operates a network of special cellular base stations around the U.S. to send data from the Internet to the planes and back. Its Gogo service is offered by United Airlines, Delta Air Lines, Virgin America and other commercial carriers, and the company also sells Gogo Biz for business jets.On planes where the airlines choose to upgrade the radio equipment, users should get about four times the speed with the new technology, according to Aircell. The main upgrade option, using a faster cellular technology, is scheduled to become available in the first half of 2012, the company said.Aircell's plan for a new generation of technology is the latest signal that in-flight Wi-Fi is here to stay. Aircell's services began to appear in 2008 after an earlier, satellite-based attempt to put passengers online, Connexion by Boeing, had failed to capture a strong following. But Wi-Fi is now available on many domestic flights in the U.S.Aircell, the biggest provider of these services, charges between US$4.95 and $12.95 depending on the length of the flight and the passenger's device. Facebook, airlines and other companies have sometimes offered special deals that make the service free.Business travelers are already demanding in-flight Wi-Fi, and more consumers will, especially the growing number of passengers with smartphones, said analyst Avi Greengart of Current Analysis."Connectivity is something that consumers are beginning to take for granted in other aspects of their lives," Greengart said.And, on flights just as in hotels and coffee shops, people are willing to pay for it, Tolaga Research analyst Phil Marshall said.Aircell will upgrade its cellular infrastructure from Revision A to Revision B of EV-DO (Evolution-Data Optimized), the 3G data technology for CDMA (Code-Division Multiple Access) networks. In Aircell's implementation, Revision B can increase EVDO's downstream speed from about 3.1M bps (bits per second) to 9.8M bps, according to Anand Chari, vice president of engineering. For airlines that want even more capacity, Aircell will also install satellite equipment on planes to link up with Ka-band satellites. The Ka-band system will be available in the continental U.S. in 2013 and around the world in 2015, according to Aircell.Satellite uplinks will also allow Aircell to offer services outside the continental U.S., on carriers based both in the U.S. and elsewhere. Airlines that want to provide Internet access on international flights before the Ka-band satellites become available will be able to use an existing network on the so-called Ku band, Chari said. The Ka band will be more economical, he said.Individual passengers should see better performance on their phones and laptops once the faster links are installed. Because not everyone is typically using the shared link at a given time, users are likely to get 5M bps or more, Chari said. However, there will still be limits to what they can do online on a typical flight, he added. For one thing, Aircell uses traffic engineering to make sure everyone sharing the network gets the best possible experience."If you want to sit on a plane and watch a Netflix movie, it's not going to work very well for you, because we did not build the network where everybody can watch a Netflix movie," Chari said.Aircell said in 2008 that it hoped to deploy LTE beginning in 2011 and achieve a 300M bps link from the ground to the air. However, the company doesn't yet have enough radio spectrum to use LTE, though it is working on acquiring more, Chari said. EV-DO Revision B will be a hardware and software upgrade to Aircell's existing EV-DO network, which is supplied by Chinese telecommunications vendor ZTE.EV-DO Revision B has been available for several years but was upstaged by LTE (Long-T erm Evolution), which can offer even higher speeds. Only three mobile operators in the world have deployed Revision B, according to Qualcomm, the pioneer of EV-DO. However, Aircell is better able to take advantage of the technology, Chari said. For one thing, Revision B requires a clean signal, which is harder to achieve when it has to go through walls and other obstacles, he said."We have a very unique situation: There is nothing between the aircraft and our towers," Chari said.。