It is fairly easy to spot system that is using microwave communication by noticing satellite dishes usually located on top of the building. Those dishes are necessary for sending focused beams of energy over long distances. Focused beam is made of the lower gigahertz frequencies of the electromagnetic spectrum. These frequencies offer better throughput and performance than other wireless transmission media. There are two main types of microwave communication systems.
First one is terrestrial system. It relies on transmission through directional parabolic antennas. Signal can only travel to receiver in the line of sight. Typically it is used in scenarios where two buildings need to have a connection and cabled solution is either impossible or is not cost efficient.
Specifications of terrestrial microwave system are:
- Low gigahertz frequency of 4-6 GHz and 21-23 GHz;
- Low cost of systems with transmission distances below few hundred meters (high cost for long-distance solutions);
- Complex installation process due to line-of-sight alignment requirement. Requires technician.
- Data rates between 1 and 100 Mbps;
- Attenuation might be affected by many factors including weather, frequency, signal strength, and antenna size;
- Signal can be affected by electromagnetic field;
- Eavesdropping is easy.
Second type is satellite microwave system. It is using similar approach with only difference that one of the antennas is on a satellite 50000 km above Earth. Satellite allows to cover much wider areas than it is possible with terrestrial system. And since satellite is able to re-transmit signal to another satellite, system allows to communicate with any point on the Earth surface. However, since signal needs to travel to space and back, it generates delays even if distance on Earth between transmitter and receiver is just several kilometers. It is called propagation delay and it could be up to five seconds.
Satellite microwave system features are:
- 11-14 GHz operating frequency;
- It is very expensive solution, since one would require to lease or build and launch satellite;
- Installation is extremely difficult and require technical personnel;
- Capacity between 1 and 10 Mbps;
- Attenuation depends on weather, frequency, signal strength, and antenna size;
- Exposed to eavesdropping.