Unbounded/Unguided Transmission Media in Networks
For data to move from one place to other it needs a medium to travel. A simple analogy would be for a person to travel from point A to point B; he can use a Car, Bus, Plane, bike etc. These are mediums through which travel is possible.
With the help of transmission media electronic signals from the computer are sent to one another. The signals used by computers are binary pulses, either 1 or 0.
There are two types of transmission media, namely:
- Bounded/Guided Transmission
- Unbounded/Unguided Transmission Media
In this article we will discuss about Unbounded/Unguided Transmission.
In Unguided or Unbounded transmission the source and destination does not have any physical connection between them. Data is sent through air which does not make it bound to a channel this known as unbounded. It is also known as Wireless media as no wires are involved in this communication.
Below are the types of Unbounded Media:
- Microwave: In this type of communication the sender is required to be in the receiver. It energy is focused on having energy in a beam and it travels in straight line. Antennas are used which are aligned for transmitting and receiving.
Any obstructions like building can obstruct microwaves from travelling. An example of microwave technology is Bluetooth.
The frequency used here is higher than that of radio waves. Types of microwaves are:
a) Terrestrial Microwave: The wireless signals can be transmitted few miles. The antennas used are parabolic and need to be pointing to each other. Low gigahertz is used in this type of communication. Signals from one antenna can be repeated to another antenna in order for the data to reach from source to destination.
b) Satellite Microwave: This type of communication requires sending the relay station in space, thus to be prevented from atmosphere. The signals from Satellite are used across the world. These satellites are placed in space with the use of Rockets and Space shuttles. Being place above a very high distance from the equator, and is place in such a way that the rotation of each and the satellite matches thus always maintain a point of sight and thus looks stationary when seen from the earth.
The orbit where it is place is known as geo-synchronous orbit, which means both rotating similarly making it look stationary. It is very expensive and can cause complexity in launching it. In case of bad weather, some disruption in signal can occur.
- Radio Transmission: The transmission frequency used here is about 10 kHz – 1GHz range. Multicast communications are usually done using radio transmission. These waves are propagated using one of the following:
a) Troposphere: This portion is close to the earth’s atmosphere. In this region we can see wind, air planes, clouds etc.
b) Ionosphere: This layer is below space and above the troposphere and the region is filled with electrical particles that are charged.
Radio waves can be either:
- Short waves
- Very High Frequency ( VHF)
- Ultra High Frequency (UHF)