ISO Open Systems Interconnection (OSI) model is one of the most widely read about topic in the area of systems connectivity. The OSI layer consists of 7 layers, viz Application, Presentation, Session, Transport, Network, Datalink, and Physical. Each of these layers have been explained in detail. Relationship between OSI model and network devices has been given.

The article provides a detailed procedure for noise figure measurements. Noise figure measurement is one of the most important parameter in the receive chain of the satellite - to - ground station link. The signals received at the antenna are very weak and requires a low noise amplifier to keep the noise below the threshold level.