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Sender, Source & Channel Coding, Channel, Receiver in wireless communication - step by step (2)


Modulation & Demodulation:

Wireless communication relies heavily on modulation and demodulation. By modulating with a high frequency carrier signal, we can convert the frequency of the original baseband signal to a very high frequency. Because, in many ways, a low frequency baseband signal is unsuitable for wireless communication. Modulation, on the other hand, increases channel capacity by delivering many data streams via a single channel at the same time. Because of this property of modulation, we employ it in wired communication as well. In a communication system, the modulation process is performed on the signal right before transmission from the antenna.


Signal Processing at receiver side for wireless communication:

To recover the signal, we perform the exact opposite on the receiver side. If we execute signal encoding on the transmitter side, we must also do signal decoding on the receiver side. If we modulate on the TX side, we must demodulate on the RX side, as indicated in the diagram above. At the end of process, receiver sends the feedback to the transmitter or sender so that sender can be informed whether the data packet is successfully received or not.


Acknowledgement / Feedback from Receiver Side in Wireless Communication:

It is essential to inform sender / transmitter that specific message / data packets have been received for reliable communication. For TCP transmission protocol sender sends a data packet to receiver. Then at receiver side it checks whether whole data packets have been transferred or not. If it received by receiver then it sends acknowledgement to transmitter. If not then whole packet is retransferred again.


Deep Dive:

If the source is analog in nature, we use the sampling and quantization approach to digitalize the signal. However, before transmission, we modulate the message signal with a high-frequency carrier signal. In fact, the signals that travel over a wireless channel are analog in nature. We typically don't need to apply modulation while using wired communication. We employ line coding techniques such as RZ, NRZ, duo binary, Manchester waveform, etc. to convert the digitalized signal into various waveforms. 

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