Networks and Communications
Characteristics of Wireless Transmission Media
What is Wireless Transmission Media?
Wireless transmission media refers to the technologies used to send communications signals through the air. These technologies are used when it is impractical or impossible to utilise wired transmission media. Types of wireless transmission media include:
Broadcast radio is a one-way transmission medium in which a transmitter sends out a signal in all directions that is intended to be received by multiple receivers.
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In order for a transmission to reach a transmitting station to a receiving station through a communications satellite, two transmissions are involved; the uplink and the downlink. • The uplink refers to the transmission of data from the transmitting station on Earth up to the satellite. • The downlink refers to the satellite receiving the transmission and then relaying that transmission to the receiving station back on Earth Satellite transmission is conducted using a communications satellite that are set in geostationary orbit (stationary in relation to the Earth’s rotation). They operate in the microwave spectrum to transmit data. This requires line-of-sight from the satellite and the receiving station on Earth, as such, there is a limited land area on Earth that can receive satellite communications. The coverage area is referred to as the “footprint” of a satellite.
Microwave transmission is a transmission medium that requires line-of-sight between transmitting and receiving station. This limits the maximum possible distance of a single microwave transmission to around 40-50kms due to the Earth’s curvature breaking line-of-sight. This distance can be extended using repeater stations that increase the power of and retransmit a signal. Microwave line-of-sight is affected by solid objects such as; trees, buildings, birds, heavy rain, etc. The relatively high operating frequencies of microwave transmission (approx. 3GHz to 10GHz) allow for high speed and bandwidth.
A cellular network refers to a radio network that covers a large geographical area by dividing the coverage into smaller areas called cells. Each cell is served by a transceiver called base stations. These base stations communicate with devices through the use of radio waves. Cellular networks are most used with mobile devices like phones as they allow for the device to move between cells without interrupting the process of transceiving data. This process is referred to as a “handover”, where the device’s data session is transferred from one base station to another.