Rain fade

Satellite communications is affected by moisture and rain in the path of signal. The effects are less at lower frequencies, L and C band, but become quite severe at higher frequencies, Ku and Ka band. For satellite internet services in tropical areas with heavy rain, C band (4/6 GHz) with circular polarisation is popular. At Ka band (19/29 GHz) special techniques such as large rain margins, adaptive uplink power control and reducing bit rates during rain are applied.

The amount of time for which service is lost is reduced by increasing the size of the dish so as to gather more of the satellite signal on the downlink and producing a more intense transmission on the uplink.

Modern consumer-grade dish antennas tend to be fairly small, which reduces the rain margin or increases the required satellite downlink power and cost.

Large commercial dishes 3.7m to 13m diameter are used to achieve large rain margins and also to reduce the cost per bit by requiring far less power from the satellite.

Modern download DVB-S2 carriers, with RCS feedback, are intended to allow the modulation method to be dynamically altered, in response to rain problems at a receive site. This allows the bit rates to be increased substantially during normal clear sky conditions, thus reducing overall costs per bit.

Latency

Latency is the delay between requesting data and getting a response, or in the case of one-way communication, between the actual moment of broadcast and the time actually received at the destination. Compared to ground-based communication, all satellite communications experience high latency due to the signal having to travel 35,000 km (22,000 miles) out into space to a satellite in geostationary orbit and back to Earth again.

The signal delay can be as much as 500 milliseconds to 900 milliseconds, which makes this service unusable for applications requiring real-time user input, such as online games or remote surgery. This delay can be very unpleasant with interactive applications, such as VoIP, videoconferencing, or other person to person communication. The functionality of live interactive access to a distant computer can also be subject to the problems caused by high latency. These problems are more than tolerable for just basic email access and web browsing and in most cases are barely noticeable.

There is no simple way to get around this problem. The delay is primarily due to the speed of light being 299,792.458 km/second (186,262.397 miles per second) in a vacuum. Even if all other signaling delays could be eliminated it still takes the electromagnetic wave 233 milliseconds to travel from ground to the satellite and back to the ground, a total of 70,000 km (44,000 miles) to travel from the source to the destination. 140,000 km (88,000 miles) for a round trip (user to ISP, and then back to user).Factoring in normal delays from other network sources gives a typical connection latency of 500–700 ms. This is far worse latency than even most dial-up modem users' experience, at typically only 150–200 ms total latency.