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Table of contents
1.
Introduction 
2.
Digital-To-Digital Conversion
2.1.
Line Coding
2.1.1.
Unipolar
2.1.2.
Polar
2.1.3.
Bipolar
2.2.
Block Coding
2.3.
Scrambling
3.
ANALOG-TO-DIGITAL CONVERSION
4.
Transmission Modes
4.1.
Parallel Transmission
4.2.
Serial Transmission
5.
Frequently Asked Questions
5.1.
What is analog to digital conversion?
5.2.
How is digital transmitted?
5.3.
How do computers use digital transmission?
5.4.
What is a digital signal?
5.5.
What is pulse amplitude modulation?
6.
Conclusion
Last Updated: Mar 27, 2024
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Digital Transmission

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Introduction 

The data must be in distinct digital form for a computer to utilize it. Signals, like data, may have both analog and digital forms. Data must first be transformed into digital form before being sent digitally. The computer can only interpret binary language, expressed in the form of 0 or 1, and it also stores data in digital form.

Computer Networks

As a result, we must transform the data into a digital format that the computer can understand. Data can be represented in two forms either analog or digital.

Following are the conversion techniques used for data conversion:

  1. Analog to digital conversion
  2. Analog to analog conversion
  3. Digital to digital conversion
  4. Digital to analog conversion

 

We need to convert our data to a digital format to store it on a computer. There are only two methods to convert data into digital form and in this blog, we'll go through digital-to-digital conversion.

Digital-To-Digital Conversion

This section describes how to transform digital data into digital signals. There are two methods to accomplish it: line coding and block coding. Line coding is required for all communications, but block coding is optional. The representation of digital information by a digital signal is known as digital-to-digital encoding.  The process of converting binary 1s and 0s created by a computer into a series of voltage pulses sent across a wire is known as digital-to-digital encoding.

The following are three approaches employed in this conversion:

  1. Line Coding
  2. Block Coding
  3. Scrambling

Line Coding

The technique of converting digital data into digital signals is called line coding. The most frequent kind of digital data is binary data. It is internally represented (stored) as 1s and 0s. Assume the data is in text, numbers, audio, or video and is stored as a sequence of bits in the computer. Line coding converts a sequence of bits into a digital signal.

On the transmitter side, digital data is encoded into digital signals, and digital data is recreated on the reception side by decoding the digital signal.

digital signal transmission

                                                                            Source 

Line Coding can be broadly classified into five categories:

  1. Unipolar
  2. Polar
  3. Bipolar
  4. Multilevel
  5. Multi Transition
     

Unipolar

Unipolar encoding techniques encode data with a single voltage level. In this scenario, high voltage is delivered to represent binary 1 while no voltage is transmitted to represent binary 0. Because there is no rest condition, it is also known as Unipolar-Non-return-to-zero. It either represents 1 or 0.

Unipolar encoding

                                          Source 

Polar

In this line scheme, the voltages are on both sides of the time axis. Consider the following illustration: the level of 0's voltage may be positive, whereas the voltage level can be negative. As a result, we employ two voltage amplitude levels in Polar NRZ encoding.

Polar NRZ is of two types:

  • NRZ-L(NRZ-level): The voltage level is most responsible for the bit's value. As a consequence, the bit value determines the signal's level.
  • NRZ-I(NRZ-Invert): The bit's value is largely affected by the voltage level change. The bit is 0 if there is no change; if there is a change, the bit will be 1.
Polar NRZ

Source 

     There will be no inversion in the above figure if the next bit is 0. However, if the following bit is 1, inversion will occur.

 

Bipolar

There are three voltage levels in the Bipolar scheme: positive, zero, and negative. One data element's voltage level is set to 0, while the voltage levels of other data elements alternate between positive and negative.

Bipolar

                                      Source 

  • Multilevel Scheme
    The mBnL (Multilevel Coding) system is another name for the scheme.
    m -> The length of the Binary pattern.
    B -> The binary data.
    n -> The length of the signal pattern.
    L -> The number of levels in the signaling.

    This scheme is available in three separate versions:
    → 2B1Q
    → 8B6T
    → 4D-PAM5
     
  • Multi Transition
    This approach requires three levels (+V, 0) and more than three transition rules to travel between the levels.
    The following are the rules:
    → There is no transition if the next bit is 0.
    → The next level will be 0 if the next bit is 1 and the current level is not 0.
    → The next level is the inverse of the previous non-zero level if the next bit is 1 and the current level is 0.
    → For lengthy 0s, this approach does not do self-synchronization.

Block Coding

Redundant bits are utilized to guarantee that the received data frame is accurate. In even-parity, for example, one parity bit is inserted to make the frame's count of 1s even. The initial number of bits is raised in this manner. It's known as Block Coding.

Slash notation, mB/nB, is used to indicate block coding.

Where n > m, an n-bit block replaces an m-bit block. Three stages are involved in block coding:

  • Division
  • Substitution
  • Combination

It is then line-coded for transmission when block coding is completed.

Also see,  Personal Area Network

Scrambling

By introducing scrambling, we may change the line and block coding. It's worth noting that scrambling, as opposed to block coding, is mostly done during the encoding process.
 

The two most frequent scrambling strategies are listed below:

  • B8ZS (Bipolar with 8-zero substitution):  In this method, the sequence 000VB0VB is used to substitute eight successive zero-level voltages. V stands for violation in this sequence, a nonzero voltage that breaks the AMI encoding rule. ACCORDING TO THE AMI RULE, the B in the above sequence denotes Bipolar, which essentially means nonzero voltage level.
     
  • HDB3 (High-Density Bipolar 3-zero): This method is more careful than B8ZS since it replaces four consecutive zero-level voltages with a sequence of 000V or B00V. The main reason for utilizing two different replacements is to maintain an equal number of nonzero pulses following each one. For this aim, there are two guidelines to follow: 1. If the number of nonzero pulses following the preceding replacement is odd, we'll use the 000V substitution pattern to level things out. 2. If the total number of nonzero pulses after the preceding replacement is even, we'll use the B00V substitution pattern to equalize the total number of nonzero pulses.

Check out this problem - Count Inversions and Basic Networking Commands

You can read related articles such as Congestion Control in Computer Networks here.

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ANALOG-TO-DIGITAL CONVERSION

Analog-to-digital conversion (ADC) is the process of converting continuous analog signals into discrete digital representations. In simpler terms, it's like translating real-world information (such as sound, temperature, or light intensity) into a language that computers can understand.

Here's how it works:

  1. Sampling: The analog signal is sampled at regular intervals. This involves taking snapshots of the signal's amplitude at specific points in time.
  2. Quantization: Each sampled value is then assigned a digital representation. This involves quantizing the sampled analog values into discrete digital values. The range of possible values depends on the bit depth of the ADC. For instance, an 8-bit ADC can represent values from 0 to 255 (2^8 - 1).
  3. Encoding: Finally, these quantized values are encoded into binary format, typically using binary numbers. Each digital value corresponds to a specific combination of bits, with each bit representing a power of two.

Transmission Modes

It decides how the data is transmitted between two computers. The data can be sent through two different modes (See Transmission Modes): 

  1. Parallel 
  2. Serial.

Parallel Transmission

Parallel Transmission

 

The binary bits are grouped into fixed-length groups. Both the transmitter and the receiver are linked in parallel by an equal number of data lines. Both computers can tell the difference between high order and low order data lines. The sender sends all of the bits on all lines at the same time. Because the number of data lines equals the number of bits in a group or data frame, a whole group of bits (data frame) is delivered in one go. The benefit of parallel transmission is fast speed, but the downside is the cost of cables, which is proportional to the number of bits transferred in parallel.

Serial Transmission

Serial Transmission

Bits are sent one after the other in a queue in serial transmission. Only one communication channel is required for serial transmission.

Serial transmission can be either asynchronous or synchronous.

  1. Serial Asynchronous Transmission
    It is so named because time is unimportant. Data bits have a distinct pattern that aids the receiver in determining the beginning and end of data bits. For example, every data byte begins with a 0 and ends with one or more 1s.
    A gap may exist between two continuous data-frames (bytes).
     
  2. Serial Synchronous Transmission
    Timing is critical because there is no system in place to distinguish start and finish data bits in synchronous transmission. There is no prefix/suffix technique or pattern. Data bits are delivered in burst mode, with no pause between bytes (8-bits). A single burst of data bits can include many bytes. As a result, time becomes critical.
    It is the receiver's responsibility to recognize and divide bits into bytes. The advantage of synchronous transmission is that it is fast and does not have the overhead of extra header and footer bits that asynchronous transmission has.
     

You can also read about the network models in computer network.

Frequently Asked Questions

What is analog to digital conversion?

Analog-to-digital conversion is the process of digitalizing an analog signal. If a person delivers a voice as an analog signal, we must digitalize it to make it less susceptible to noise. It necessitates a decrease in the number of values in an analog message to represent them digitally. The information contained in a continuous waveform is translated into digital pulses during analog-to-digital conversion.

How is digital transmitted?

Digital data is transmitted through mediums like cables or wireless signals by encoding binary information into electrical or electromagnetic signals.

How do computers use digital transmission?

Computers send and receive digital data using networking hardware and protocols, converting information into binary signals for transmission over networks.

What is a digital signal?

A digital signal is one in which data is represented as a series of discrete numbers. A digital signal can only take on one value from a limited range of potential values at any one moment. The physical amount representing the information in digital signals may be any of the following:

  • Electric current or voltage that varies
  • An electromagnetic field's phase or polarization.
  • Pressure acoustic
  • A magnetic storage medium's magnetization

What is pulse amplitude modulation?

The pulse amplitude modulation approach takes an analog signal, samples it, and then creates a sequence of digital pulses depending on the sampling results. Sampling is the process of measuring the amplitude of a signal at equal intervals.

Conclusion

This article briefly discussed digital transmission in detail, and we have also discussed the different ways it can be done.   

Recommended Readings:


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