This article aims to describe the basic block diagram of a digital communication system. Specifically, it will cover the block diagrams for the transmitter and reception sides. I will go into great depth about each block as we work with the system.
As we can see, the transmitter and receiver are the two primary building components of a digital communication system. So, we will start with Transmitter Block.
Transmitter
Information Source & Input Transducer
If you see the Transmitter Block Diagram, the first block is information source and Input Transducer block. There might have been a variety of information sources available at the time, including discrete data, audio, video, and images. This data may be in the form of mixed digital and analog signals, or it may be analog only.
In situations where an electrical signal is lacking, such as when sound is a physical quantity not represented by an electrical signal, we must employ a transducer to transform the non-electrical signal back into an electrical signal.
Following the signal's passage through the information source and input transducer block, we can classify the signal as either digital or analog, and electrical in nature.
Source Encoding
Redundancy reduction is the fundamental function of source encoding, hence any redundant information in an electrical signal must be eliminated. It is being used to efficiently use bandwidth, and for digital data, source encoding blocks can be used to achieve data compression. There are 2 different type of Digital compression techniques:
- Huffman Coding
- Shannon Fano coding
We use the following modulation techniques for analog redundancy:
- Adaptive Delta Modulation (ADM)
- Delta Modulation (DM)
- Pulse Code Modulation (PCM)
Channel Encoding
Why is channel encoding used? By enhancing signal redundancy, it serves to give the system noise immunity. We employ a few different methods for channel encoding, including:
- Block Code
- Cyclic Code
- Convolutional Code
Digital Modulator (Transmitter Side)
Digital Modulator have two inputs one is channel encoded output which is a digital output, and we are multiplying it with the high frequency carrier signal so that we can send it by antenna. So, to send the signal to longer distances, we need to convert low frequency digital signal to high frequency analog signal which can be achieved using digital modulator. and there are various techniques to do so:
- ASK (Amplitude Shift Keying)
- FSK (Frequency Shift Keying)
- PSK (Phase Shift Keying)
- QPSK (Quadrature Phase Shift Keying)
Receiver
Digital Modulator (Receiver Side)
Electromagnetic waves from the transmitter antenna will be received by the receiver antenna, which will perform the exact opposite function of a digital modulator. In other words, the local oscillator-generated carrier signal and the antenna signal are multiplied and fed to the channel decoding.
Channel Decoding
when there is any error in the code word which we received from the transmitter, so that error will be corrected by channel decoding Block. Now, here we have only information signal, we remove the redundancy form the information signal. so, the channel Decoding will be giving the information as output after correcting the error in the signal.
Source Decoding
Source Decoding converts digital data to analog data and here whatever analog signal is there that we give it to output transducer.
Output Transducer
The output transducer receives the analog signal from the source decoder and transforms it into digital discrete signals, text, audio/video, and other signals.
Conclusion
In summary, this article has provided a comprehensive examination of the transmitter and receiver blocks, which are the fundamental components of a digital communication system. We began with the transmitter, exploring the role of the information source and input transducer in converting various forms of data into electrical signals. Next, we addressed source encoding, which is designed to reduce redundancy and optimize bandwidth utilization, and channel encoding, which is designed to improve noise immunity. We highlighted the modulation techniques used to convert low-frequency digital signals to high-frequency analog signals for transmission.
On the receiver side, we examined the demodulation process, where we convert received signals back to their original form by reversing the modulation process. We showed how channel decoding corrects errors and removes redundancy, ensuring the accuracy of the received information. Finally, we explained source decoding and the output transducer as the final stages in converting digital data back into its original analog form, ready for output as text, audio, or video.
By breaking down each block in detail, we have provided an exhaustive understanding of how digital communication systems function, from the initial data input to the final output, ensuring efficient and accurate transmission of information.
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