Lighting a Fire Under Satellite Broadband
...
...
...
ViaSat, however, does most of the back-and-forth work for the subscriber’s computer in advance. When an Exede subscriber accesses a website, ViaSat’s ground network preassembles it and beams it up in a tight package, reducing lag time to the half-second minimum. The company calls this system AcceleNet. Not only does it speed a subscriber’s Web experience, it conserves bandwidth on the satellite by sending the Web page in a single shot.

AcceleNet is powered by five large data-processing centers located in Dallas, Denver, Fort Worth, Salt Lake City, and Seattle; each has 100 to 200 blade servers. The data centers handle security and other traditional Internet service provider tasks, but much of their processing power is devoted to AcceleNet.

It’s no coincidence that the data-processing centers and the 20 Earth-based transmitters that connect them to the satellite are all in the western half of the United States, which has a drier climate. Previous satellite broadband services tended to lose their signal in wet weather (a phenomenon known as rain fade), and the problem was most pronounced for satellites using the highest frequencies. ViaSat-1 transmits on the relatively high-frequency Ka-band—uplinking at 28.1 to 30 gigahertz and downlinking at 18.3 to 20.2 GHz—parts of the spectrum that are susceptible to rain fade.

But subscribers aren’t limited to the American West. To overcome wet weather, ViaSat has equipped every subscriber’s modem with an adaptive transmitter that optimizes its signal in real time. The transmitter constantly measures signal quality and reengineers the waveform it transmits. ViaSat’s earth-based transmitter modems use the same process.

“ViaSat is good at [adaptive modems],” says Keith Barker, president and chief executive officer of the Questiny Group, an engineering consultancy specializing in wireless communications technology. “Bringing this technology to the Ka-band satellite market will be a competitive advantage, but likely not a sustainable one,” he says. That may be bad news for ViaSat but good news for satellite broadband users who want more bandwidth and competition in the market."