Introduction to Physical layer | networking
In OSI network model Physical layer is the lowest layer, which is the only layer that deals with the physical connectivity between two communicating bodies. It is concerned with the transaction of raw bits over some communication medium or channel. The design should make sure that when one end sending signal ‘HIGH’ i.e. 1-bit other end or receiver receiving as ‘HIGH and ‘LOW’ for ‘LOW’ i.e. 0-bit signal.
Types of medium
The medium can be classified mainly into two categories.
- Guided Media: Guided media means the signal is transferred by physical media like copper wire, optical fiber, etc. The signal is guided or controlled flow of signal and remained inside the physical media.
- Unguided Media: Unguided media means no control over the flow of the signal. No physical medium is needed for the propagation of the signal, generally uses Electromagnetic waves for transmission. example: radio waves.
In a network, nodes are connected through network links. Based on links communication can be classified as
- Simplex: In simplex type, communication takes place in one direction only. For example Television(T.V.) & Radio broadcasting.
- Half-duplex: In half-duplex, communication takes place in one direction at a time and time-sharing fashion. Like, from node 1 data is being transferred to node 2 that time data from node 2 cannot flow to node 1 simultaneously. For example, walkie-talkie used in the earlier days.
- Full-duplex: In full-duplex, communication takes place in both directions simultaneously. For example, talking on a telephone.
based on the connection between nodes in the network, links can be further classified as
- Point to Point: In this communication type, only two nodes are connected to each other. when one node is transmitting data then that can only be received by another node in the network, none other than that can receive the same.
- Multi-Point: In this communication type, the transmitted signal can be received by all nodes, this is a kind of sharing communication and also known as broadcast.
problems during transmission
Generally, there are two types of problems associated with the transmission of signals,
- Attenuation: Attenuation means a reduction in something, here for signal its reduction or degradation of the quality of the signal. Due to many causes like long-distance data transmission using wire. To improve the quality of the signal, signal-amplifier are used in a regular interval of distance.
- Noise: Unwanted distortion in actual signal is known as noise. Some random signals present in the medium, due to interference, the actual signal gets disrupted a little bit.
Bandwidth is the count of numbers of bits that can be transmitted in a second in the communication channel. In other words, it is the width of the frequency spectrum.