坐飞机想用Wi-Fi？这些方法就能搞定

机上Wi-Fi已经越来越普及，相关技术也在一直进步，以满足日益增多的需求。

在此介绍两个在飞机上使用Wi-Fi的方法，一种要借助专门的地面手机信号塔，另一种要利用通信卫星。

但飞机上的Wi-Fi究竟如何发挥作用呢？作为全球最大空中互联网服务供应商之一，Gogo既利用地面信号塔，也依靠全球人造通信卫星，服务的航空公司包括达美航空、美国联合航空、阿拉斯加航空和维珍航空等。负责外联和公关的Gogo副总裁史蒂夫·诺兰向我们解释了服务运行的具体情况。

手机信号塔怎样实现机上互联网服务？

第一种实现机上Wi-Fi的方法是地面手机信号塔，工作原理跟向手机提供Wi-Fi网络类似。

具体来说就是将大型信号塔指向天空，向飞过的飞机传输Wi-Fi。无线服务商向手机提供信号时，信号塔则定向地面。由于航空公司的信号塔向天空发射信号，覆盖范围会更广。

“无线电波的覆盖范围是个锥形体，”诺兰说，“信号塔距离地面很近，所以发射范围不会很大，想实现覆盖就需要更多塔。向天空传输信号时覆盖范围会大得多。”

人造卫星怎样实现机上互联网服务？

如果使用人造卫星提供Wi-Fi，飞机可以通过机身上部的天线接收信号。人造卫星运用的频率和手机信号塔不同，不但提供的上网速度更快，而且在水域也可以实现联网。

越来越多航空公司接受了这种新技术。据诺兰介绍，虽然业内有其他网络提供商竞争，已有1600架飞机将选用Gogo的人造卫星技术。

捷蓝航空自2013年起提供机内联网服务FlyFi，今年1月成为首家实现空中免费高速上网的航空公司。捷蓝航空的发言人表示，提供FlyFi服务的人造卫星由ViaSat和Thales等公司制造，目前美国境内各航线均已实现覆盖。

机上Wi-Fi在任何地方都可以用吗，是否包括海洋上空？

飞行途中能否用Wi-Fi取决于航空公司选用哪种服务。比如诺兰提到，Gogo的空对地技术利用手机信号塔实现Wi-Fi时，只在陆地上空才能接收到信号。使用人造卫星提供Wi-Fi能在跨海时联网，不过覆盖范围不够全，信号可能偶尔中断。此外飞机途径地球两极时也会收不到信号。

机上Wi-Fi网速有多快？

诺兰说，因为供应商和使用服务不同，机上Wi-Fi的速度也会有差别。Gogo的空对地服务利用手机信号塔时，整架飞机共享9 Mbps的下载网速，而人造卫星提供的Wi-Fi可为每位乘客提供15 Mbps的网速。捷蓝航空的发言人称，在信号覆盖范围内，FlyFi可实现人均网速12到20 Mbps。对比来看，美国互联网服务商Xfinity和Fios提供的宽带网速在10 Mbps到500 Mbps之间。（财富中文网）

译者：Pessy

审稿：夏林

As in-flight Wi-Fi becomes more common, the technology has been changing to meet growing demand.

There are two methods for bringing Wi-Fi to planes. One uses special ground-based cell towers, while the other uses satellites.

But how exactly does Wi-Fi work on planes? One of the biggest providers of inflight internet, Gogo, uses both ground-based towers and satellites around the world, which service airlines including Delta, United, Alaska Airlines and Virgin Air. Here, Steve Nolan, vice president of communications and public relations for Gogo, explains how these services work.

How do cell towers power in-flight internet?

Ground-based cell towers, which was the first method of delivering in-flight Wi-Fi, are similar to the same towers that deliver Wi-Fi to cell phones.

The large towers project wireless service by pointing toward the sky, delivering Wi-Fi to planes flying overhead. In contrast, towers used by wireless providers direct coverage toward the ground. Turning the coverage toward the sky allows airline towers to have a larger coverage area.

"If you think about how a radio wave works, it goes out like a cone," Nolan said. "So you need many more ground towers because they're closer to the ground and the beam doesn't wide out as much. When it points upwards, it widens into a much larger space."

How do satellites power in-flight internet?

With satellite powered-Wi-Fi, planes connect to the internet using an antenna mounted on top of the plane. Besides using a different frequency than cell towers, satellite-powered service also allows planes to provide faster service and can be used over water.

This new technology has been embraced by more and more airliners. According to Nolan, 1,600 planes are committed to installing Gogo's satellite technology, though other companies also offer the service.

JetBlue, which became the first airline to offer free high-speed internet on all of its planes in January, has been offering its FlyFi service since 2013. A JetBlue spokesperson said the company uses satellites from companies including ViaSat and Thales for its FlyFi service, which is offered on its flights within the U.S.

Can you use plane Wi-Fi anywhere (including oceans)?

Where you can get Wi-Fi while flying depends on the service your airline uses. For example, Gogo's air-to-ground technology uses cell towers and only works when above land, according to Nolan. Their satellite Wi-Fi can work overseas, though there can be gaps in coverage. The service also will not work over the North and South poles.

How fast is in-flight Wi-Fi?

In-flight Wi-Fi speeds vary based on the provider and the service used. According to Nolan, Gogo's air-to-ground service, which utilizes cell towers, gives customers 9 Mbps for the entire aircraft and satellite offerings provide 15 Mbps per person. JetBlue's FlyFi has speeds ranging between 12 and 20 Mbps per person when within the coverage area, according to a JetBlue spokesperson. In contrast, U.S. internet providers Xfinity and Fios offer internet speeds ranging from 10Mbps to 500 Mbps.