如今大多数互联网的运作方式很简单, three-part process: The internet service provider (ISP) gets the internet signal via fiber from a collection of data servers, 把信号转移到中央电台, 或中心, 然后将其分发给个人用户的调制解调器.
前两部分是最容易完成的, while the third — getting the signal to those modems — is the tricky part. 最后一段通常被称为“最后一英里”,以及许多没有足够互联网服务的家庭, it’s that last mile (or multiple miles) from the hub that makes the difference.
如果你考虑电缆或光纤isp, 他们需要一名技术人员出来为每个地点布线, 然后连接到本地集线器. 因为大多数家庭已经完全有线了, 将一个社区的所有家庭连接起来相对简单. If your home is not in a populated area where it makes economic sense for the ISP to serve you with short runs from the hub to your home, 就没那么简单了. 在电缆或光纤的情况下，这可能意味着它们根本不为你服务. 电话公司的DSL, 他们可能会为你服务, 但是离最近的中央车站越远, 服务越差.
And that’s why satellite internet became a way to bridge the digital divide for people outside the cable and fiber zone and for those 生活在偏远和农村地区. Satellite ISPs like Viasat work in essentially the same three-step fashion, 但不是一个中央车站, the internet signal is delivered via fiber to a large antenna (called an “earth station”) on the ground, 然后通过无线电波将信号传送到我们的卫星上.
在这个模型中, 卫星的功能就像中央办公室一样, “最后一英里”更像是22英里,300英里——我们的卫星轨道的高度. The signal comes back down to your home or office and is captured by an antenna (dish) outside your home that’s aligned with the satellite. 从那里, the signal goes into a cable through a hole in the wall that connects to a modem — just like any other ISP.
光谱 & spot beams One of the questions we often hear when talking to new customers is whether they can use the same dish they already have for satellite TV. 这是个好问题，但答案是肯定的“不”.” The main reason for this is that satellite TV only goes in one direction, broadcasting video signals from the satellite to the home with no “return flight.“互联网信号必须是双向的, 由于来回的信号不像视频那样广播, 移动所有这些数据需要更大的带宽. 也, fixed antennas like the ones used for internet and TV all point at different satellites, so it’s not like a TV antenna that can receive different stations on the ground.
That leads to another interesting thing about how we deliver internet via satellite. While the video satellites can broadcast one way in a very large beam that can cover an entire continent, 这样做对互联网来说是对带宽的浪费. 想想一个广播电台，比方说，97.3. If you’re within 50 or so miles of that, you’ll get your local station at that frequency. 在下一个州，你的岩石站在97号.3号可能是一个乡村车站, because the distance has allowed for a re-use of that portion of the radio spectrum.
Our satellites receive the Ka band of the radio spectrum near 30 GHz and transmit near 20.2ghz，我们将信号部署在所谓的“点波束”中.” These are aimed at specific areas on the ground and they overlap (see illustration). If we’re using the same part of the spectrum for this, then how does that work?
This illustration shows how one-way beams from a video satellite differ from the spot beams Viasat uses to deliver internet with a two-way beam.
答案是我们用不同的偏振来分解波段. In case you’re not an electrical engineer, just think of it as different colors. 在一个单点光束内, 我们可以用许多不同的颜色来传递信号, 重复使用相同的频谱. Viasat has dedicated quite a bit of effort over the past decade to improving how we do this, and it’s resulted in a highly efficient use of the radio spectrum we’re allocated. This in turn allows us to deliver more bandwidth to all of those modems out there.
As we’ve increased the power of our satellites, we’ve also had to up our game on the ground. 就像更多的信号塔意味着更好的智能手机覆盖范围一样, more of those earth stations adds up to a stronger network for our satellite service. 同时, moving the processing functions into the cloud has allowed us to create smaller, 比以前更便宜的地面站. 这样一来，再多建几个这样的帐篷就更经济了.
恐怖主义风险保险法案的
We’ve touched on all the main components of how we deliver satellite internet, but there’s one more to mention because it’s something you actually see on your home. 许多人所说的“菜”实际上是两种不同的东西. The dish itself is just a reflector: a piece of stamped steel aimed at the satellite that works to focus the signal read by the TRIA. This is the metal box at the end of the arm that’s connected via cable to your modem.
“TRIA” is an acronym for “transmit-receive integrated assembly” but all you need to know is that it’s essentially a radio that can send and receive. 恐怖主义风险保险法案的 also has a powerful amplifier in it to enable it to push a signal back to the satellite in orbit. Along with your modem, the TRIA is the real workhorse at your location — not the larger dish.
调制解调器, 顺便说一下, serves as the interface between the radio signals received via the TRIA and your computer or router. 它还做其他事情, like authentication to ensure you’re a member of the network and modulate and demodulate the signal.
Even if the basics of how the signal gets to you from the satellite are relatively simple, it does involve a great deal of complex technology to make it all possible. 这是我们Viasat不断改进的一项技术. Our goal is to make high-speed internet access possible just about anywhere on earth in the next few years, 希望这有助于解释卫星是如何做到的.
For a more visual overview of how satellite internet works, take a look at this short video.