Basic technology of satellite phone.

• A satellite phone or satphone is a mobile phone that sends and receives calls using satellites rather than landlines or cellular broadcasting towers.
• A satellite phone only requires a clear line of sight to the sky.
• The advantage of a satellite phone is that it can be communicated from from anywhere.
• A disadvantage of a satellite phone is a noticeable delay in conversations.
• The signal must first travel to the satellite, then to an earthbound gateway before being routed to the receiver. The receiver's response will follow the same path in reverse, taking equally long to reach the caller.
• The three main satellite networks at present are Iridium, Glodstar and Thuraya.
• Some satellite networks have partnered with cellular GSM networks to provide Internet service and email through satellite phones in addition to offering GSM roaming.
• Some satellite phones use satellites in geostationary orbit. These systems can maintain near-continuous global coverage with only three or four satellites, reducing the launch costs. The disadvantage of geostationary satellite systems is that because the satellite is so far away (approx. 22,000 miles), a comparatively large antenna system is required for signal transmission and reception.

You may want to visit the following link to know more information:
http://en.wikipedia.org/wiki/Satellite_phone