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Encoding vs Modulation

Encoding and Modulation are two techniques used to provide the means of mapping information or datainto different waveforms such that the receiver (with the help of an appropriate demodulator and decoder)can recover the information in a reliable manner. Encoding is the process by which the data is convertedinto digital format for efficient transmission or storage. Modulation is the process of converting information(signals or data) to an electronic or optical carrier, so that it can be transmitted to comparatively largedistance without getting affected by noise or unwanted signals.What is Encoding?Encoding is mainly used in computers, and the process includes arranging a sequence of characterssuch as letters, punctuation, numbers and certain other symbols into a specialized format for the purposeof efficient transmission and storage. This is a common operation done in most wireless communicationsystems.Generally, encoded data can be easily reversed by using the technique called decoding. ASCII (AmericanStandard Code for Information Interchange, pronounced ASK-ee) is the encoding scheme widely used bycomputers for text files. Here, all the characters are encoded using numbers. For example, A isrepresented using number 65, B by number 66, etc. ASCII is also used to represent all the uppercaseand lowercase alphabetic characters, numerals, punctuation marks, and other common symbols.Unicode, Uuencode, BinHex, and MIME are among other popular encoding methods available.Manchester encoding is a special form of encoding used in data communications, where the transitions of

high and low logic states are represented by binary digits (bits). Also, numerous types of encodingschemes are used in radio communications. At times, the term encoding is confused with encryption.Encryption is a process where the character of a text is altered to conceal its content, whereas encodingcan be done without intentionally concealing the content. Other typical encoding techniques includeUnipolar, Bipolar and Biphase encoding.What is Modulation?Modulation can be simply defined as a way of facilitating the transfer of information over a certainmedium. For example, sound generated from our lungs, transmitted through the air can only travel for alimited distance depending on the amount of power we consume.In order to extend the distance, a proper medium is required such as phone line or radio (wireless). Thisconversion process of voice to travel in such a medium is known as modulation. Modulation can bedivided into two sub categories based on the modulation process.1. Continuous Wave Modulation

2. Pulse Code Modulation (PCM)Continuous wave modulation basically uses following techniques for modulating a signal.

Amplitude modulation (AM)

Frequency modulation (FM)

Phase modulation (PM)Pulse Code Modulation (PCM) is used mainly to encode both digital and analog information in the binaryformat. Radio and television broadcast stations typically use the above mentioned AM or FM. Most radiocompanies who use two way radios use FM.More complex modulation techniques available are Phase Shift Keying (PSK) and Quadrature AmplitudeModulation (QAM). Phase Shift Keying uses the phase modulation, and QAM uses amplitude modulation.Optical signals on fiber are modulated using an electromagnetic current applied to alter the intensity of alaser beam.What is the difference between Encoding and Modulation?

Modulation is about changing a signal, whereas encoding is about representing a signal. Encoding is about converting digital or analog data to digital signal, whereas modulation is aboutconverting digital or analog data to an analog signal. Encoding is used to ensure efficient transmission and storage, whereas modulation is used to send th esignals to a long way. Encoding is mainly used in computers and other multimedia applications, whereas modulation is used incommunication mediums such as telephone lines and optical fibers. Encoding is about assigning different binary codes according to a particular algorithm, but modulation isabout changing the properties of one signal value according to certain properties (Amplitude, Frequency,or Phase) of another signal.

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