- Infrared (Point-to-Point) Links
- Microwave Radio
- Satellite Communications
- Point-to-Multipoint Systems
- Summary
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Satellite Communications
This discussion would not be complete without a brief overview of satellite communications. Since Katrina, the satellite industry has looked in a big way at disaster recovery. When a widespread disaster occurs, as with Katrina, a major earthquake, or the Christmas 2004 tsunami in the Indian Ocean, satellite might be the only show going in the immediate aftermath.
It really pays to check out the advantage if you live in a region prone to such disasters. Also, like the previous technologies discussed above, satellite communications have taken leaps and bounds over the last few years in terms of feature richness.
There are a few disadvantages. Satellite is essentially microwave radio aimed upward—it uses essentially the same frequencies. As such, the same rules hold true regarding the tendency to wash out in heavy rains.
There are also two times every year when the satellite receiver will be aimed directly at the sun—right around the spring or fall equinox. At that time there will be a brief outage. These outages can be planned for, however, because the service provider will know precisely when they will occur.
With regard to equipment, satellite has metamorphosed from 16-foot dishes in years past to pizza pan dishes that fit on the side of a building. In fact, the case of global position systems (GPS) and freight-tracking technologies, equipment often fits in your hand. (Consider how handy it might be to have GPS in the aftermath of a tsunami or hurricane when all the street signs and landmarks have literally been washed away!)
Before using satellite, consult with the vendor on propagation delays. It still takes about a quarter of a second to get to a satellite and back because of the limitation of the speed of light. This might have a noticeable performance delay depending on the data protocol you are using.
If these delays exist, however, they can often be compensated for by the satellite provider or through the use of various outboard technologies. Nobody can increase the speed of light, but it is possible, for instance, to send more data before expecting a response, thereby increasing performance.
Companies such as Direct PC (I think they are called HughesNet now) actually use satellite for Internet access, so obviously the performance issue some of the latency issue, have been addressed.