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

Mechanism of wireless communication - step by step:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In the above figures, it is shown that in a typical wireless communication system, the original message signal, such as audio, is first converted into an electrical signal. It is then sampled and quantized. Afterward, the quantized signal is encoded into binary numbers. Remember, to transmit the signal through a wireless medium, you modulate the binary bits using a suitable modulation scheme before transmission. On the receiving end, you first demodulate the transmitted signal, then perform source decoding and other necessary operations to retrieve the original message (in this case, the audio) signal.

The range of wireless communication may be as short as 10 meter Bluetooth connection to interplanetary communication or deep space communication. Our daily usable gadgets, like, PDAs, smartphones, computers, satellite TV, etc. - all are example of wireless communication.


History of Wireless Communication:

First wireless conversation occurred in 1880 when Graham Bell and Tainter invented first photophone. It was a telephone that sent audio over a beam of light.Wireless telegraphy system was being developing by Marconi in 1894.Jagadish Chandra Bose invented millimeter wave communication during 1894 - 1896. Which was operating at very high frequencies up to 60 GHz. The work done on millimeter wave by Jagadish Chandra Bose and Lebedev may be dated back to 1890's.The true wireless revolution began in 1990's. Then digital wireless systems was pretty much developed. Then we see commercial usage of computer network, cellular network, mobile phones, laptops, etc.


Modern Wireless Communication Process:

Fig: Process of wireless communication

Wireless communication is a method of communication in which the transmitter and receiver communicate over the air or free space. Between the transmitter and the receiver, there is no wiring for wireless communication. The communication path, which is air or free space in this case, is referred to as a channel. The electrical signal is converted by the transmitter as '0' and '1'. The electric signal then transmits via the channel (air or free space) after a successful modulation procedure. The signal is then received by the receiver. It is practically difficult to recover the same signal that the transmitter sends. Due to attenuation or distortion, the signal becomes corrupted while travelling across the channel. A wireless communication system's fundamentals are as follows.

The following is a list of the various elements involved in the wireless communication process

1.Sender
2.Message
3.Encoding (source & channel coding)
4.Channel
5.Receiver
6.Decoding
7.Acknowlegement / Feedback


Sender:

Here, in communication process sender is who sends messages, files, audio, etc. to indented receiver. Here, sender send his message from smartphones, PCs, etc. using specific application.


Digitization of Message Signal in Communication Process (sampling + quantization):

In general, message signal's source is analogue in nature. Now, the analogue signal is turned into a digital signal (or, the original analogue signal is changed into '0' or'1' bits) by sampling and then quantization). Quantization helps to map the signal into finite levels. We convert analog signals to digital signals using the analog to digital converter (ADC).

There are also some exceptional cases where the source signal is not analog. The acquired images by radar, for example, are not analog signals because the image is a digital signal. After that, we process it and deliver it to the receivers on earth.


Source coding / encoding:

We are aware that the original message file is huge in size. Imagine how much memory is required to store a one-hour voice recording. It's likely that a few GB of memory is required. When we convert it to digital by just sampling at the very beginning of transmission procedure, it still requires a large number of memories to store. On the other hand, we always prefer to transmit a compressed signal over an uncompressed huge file if possible. So, we compress it. We use coding, also known as source coding, to compress the digitalized message signal. Source coding can reduce the size of a message signal. The message signal could be text, audio, or voice, for example. Text, voice, and audio messages can all benefit from source coding. For sending, original message without compressing it, it will take longer and result in more bit errors due to the larger file size. Popular examples of source coding are Huffman coding, LZW coding, etc.


Channel Coding in Communication Process:

After source coding, channel coding allows us to code the compressed message signal with various types of coding, such as forward error correcting (FEC) coding, so that we can recover the required message signal at the receiver terminal even if some bits are lost or distorted. Another illustration is the use of the CRC or cyclic coding technique in OFDM 4G-LTE communication to retrieve the original signal or measure the channel's status.


# Wireless channel are more prone to bit error than wired channels

Digital communication and its application and pictures


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