Routing

One solution: inter satellite links (ISL)

• Reduced number of gateways needed.

• Forward connections or data packets within the satellite network as long as possible.

• Only one uplink and one downlink per direction needed for the connection of two mobile phones.

Problems

• More complex focusing of antennas between satellites.

• High system complexity due to moving routers.

• Higher fuel consumption.

• Thus shorter lifetime.

Iridium and Teledesic planned with ISL.

Other systems use gateways and additionally terrestrial networks.

Reference model for satellite access

Protocol architecture

IP interworking

Communication Satellites

A Communication Satellite can be looked upon as a large microwave repeater.

It contains several transponders which listens to some portion of spectrum, amplifies the incoming signal and broadcasts it in another frequency to avoid interference with incoming signals.

Satellite Signals

Used to transmit signals and data over long distances.

• Weather forecasting.

• Television broadcasting.

• Internet communication.

• Global Positioning Systems.