Modulation is the process by which some characteristics of signal known as “Carrier Signal” is varied in accordance to the instantaneous value of the another signal known as “Message Signal”.
Methods of Modulations are:
It suffers from tolerance which occurred in its analog components. Here, short term drifts are caused due to variation in the filter and VCO components.
Multiplexing is defined as the process in which a number of message signals are combined together to form composite signals so that they can be transmitted through the common channel.
Types of multiplexing:
In analog modulation bandwidth required is low while in digital modulation due to higher bit rate, higher channel bandwidth are required.
Their are three basic types of communication system, which are-
1) Simplex Communication System:
Here, the communication system that is capable of transmitting information through, called simplex transmission system. In simplex type, one unit is equipped with a transmitter and the other side is equipped with only one receiver but communication is done only one way by transmitter.
For Example: T.V. broadcast system.
2) Half-Duplex Communication System:
Here, the communication system that is capable of transmitting information in both directions but the flow is only one way at a given time that why it is known as half-duplex. In HDX type, one unit is equipped with transmitter as well receiver at one end and a transmitter-receiver at the other end but information can’t flow simultaneously in both the directions.
For Example: Walkie-Talkie”
3) Full Duplex Communication System:
Here the flow of communication takes place in both the direction simultaneously. Full-duplex Ethernet connections work on the principles of full-duplex where data packets are received and sent simultaneously at a given time.
For Example: Phone
Communication is the process by which data is either transferred or received from one place to another via communication channel.
According to the mode of communication, it is divided into
1) Line Communication: In this mode of communication, the medium of transmission is a pair of conductors called transmission lines. Both the Tx and Rx are connected via a wire or line.
2) Wireless or Radio Communication: In this mode, a message is transmitted through a open medium as in space by electromagnetic wave which are known as radio waves.
Companding is the term derived from the combination of two terms
COMPANDING= COMPRESSION + EXPANDING
In the process of Companding, the weak signals are amplified and strong signals are attenuated before applying them to a uniform quantizer.