Satellite Internet communications can be affected by moisture, and, implicitly, by any forms of precipitation, like snow or rain. The signal path between the satellites used and the ground stations or end users may be subject to alterations. The interference of rain with the signal path is called “rain fade”.
Such effects are less important on the lower frequency bands “L” and “C”, but are significant to the higher frequency bands “Ku” and “Ka”. In tropical areas, where heavy rain is frequent, satellite Internet services use mainly the “C” band, with circular polarization. Satellite communications using the “Ka” band have special techniques to avoid the effects of precipitations:
- Rain margins;
- Reduced bit rates;
- Adaptive uplink power control.
They are the extra requirements for the communication link, necessary to compensate for the signal degradation caused by moisture and precipitation. These requirements are extremely important for any system that operates at frequencies exceeding 10 GHz.
There is a way to reduce the time during which a loss of satellite Internet service is signaled. It consists of increasing the satellite communication dish size, in order to allow more satellite signal to be captured on the downlink and provide a significantly stronger uplink signal.
To put it in other words, the overall channel gain and the signal-to-noise ratio can be improved using a larger parabolic reflector, which means increased antenna gain. This technique tolerates a greater signal loss caused by rain, without a significant drop of the signal-to-noise ratio below a minimum threshold required by successful communication.
However, increased antenna sizes for satellite Internet access is not the actual tendency. On the contrary, modern dish antennas are fairly small, and this is supposed to reduce the rain margin or determine an increase of the necessary satellite downlink power, as well as an increase of the cost. Therefore, it is often preferable to build more expensive satellites, while the consumer antennas become smaller and less expensive, instead of increasing the size of the consumer antenna and reduce the cost of the satellite.
In order to achieve larger rain margins and decrease the cost per bit by needing less power from the satellites, large commercial dishes are used, with sizes between 3.7 and 13 meters in diameter.
Satellites generally utilize photovoltaic solar power. For this reason, no expense is needed for energy, but, when more powerful satellites are involved, they require larger and more powerful electronics and solar panels and, in most cases, larger transmitting antennas. The larger these satellite Internet components are, the costlier the materials used are.
The weight of the satellite is also in question, because the launch costs of a satellite on its orbit are directly proportional with the satellite’s weight. The launching rocket has specific payload limits, according to the size of the satellite, and making it larger will require more complex mechanisms necessary to fold some satellite parts, like solar panels or high-gain antennas.
Using a more powerful rocket for launching is a more expensive alternative, because it would have a larger payload. There always has to be a balance between performance and cost, because excessively increased manufacturing and launching costs for the satellites will affect the final cost of the services provided to the end users.
The latest DVB-S2 carriers, providing RCS feedback, are meant to allow a dynamic alteration of the modulation method, depending on the rain problems that might appear at the receipt site. This is expected to allow substantially increased bit rates when the sky conditions are normal, which means clear sky, allowing an overall reduction of the costs per bit.
To find out more about how rain and snow can affect the satellite Internet transmission conditions, visit this site.