Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

correction error and, Lecture notes of Computer Science

Mekelle UniversityComputer Science

about correction errors related to computer correction

Typology: Lecture notes

2020/2021

Uploaded on 08/14/2023

kibrom-kebede
kibrom-kebede 🇪🇹

4 documents

1 / 9

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Error Detection And Correction in
Computer Network
We offer you a brighter future with FREE online coursesStart Now!!
An error occurs when the output information does not match the input
information. Digital signals suffer from noise during transmission, which can
create errors in binary bits travelling from one system to another. That is, a 0
bit may become a 1 bit, or a 1 bit may become a 0.
Many factors, including noise and cross-talk, can contribute to data corruption
during transmission. The top layers are unaware of real hardware data
processing and work on a generic picture of network architecture. As a result,
the top levels anticipate error-free transmission between the systems.
Most programs would not work normally if they received incorrect data. Voice
and video applications, for example, may be unaffected and continue to work
normally despite occasional problems.
Error detectionis the detection of errors caused by noise or other impairments
during transmission from the transmitter to the receiver.
Error correctionis the detection of errors and reconstruction of the original, error-
free data.
Error Detection:
When a message is sent, it may be jumbled by noise or the data may be
damaged. To avoid this, we employ error-detecting codes, which are bits of
extra data appended to a digital message to assist us detect whether an error
occurred during transmission.
Error Detection Techniques:
pf3
pf4
pf5
pf8
pf9

Partial preview of the text

Download correction error and and more Lecture notes Computer Science in PDF only on Docsity!

Error Detection And Correction in

Computer Network

We offer you a brighter future with FREE online courses Start Now!! An error occurs when the output information does not match the input information. Digital signals suffer from noise during transmission, which can create errors in binary bits travelling from one system to another. That is, a 0 bit may become a 1 bit, or a 1 bit may become a 0. Many factors, including noise and cross-talk, can contribute to data corruption during transmission. The top layers are unaware of real hardware data processing and work on a generic picture of network architecture. As a result, the top levels anticipate error-free transmission between the systems. Most programs would not work normally if they received incorrect data. Voice and video applications, for example, may be unaffected and continue to work normally despite occasional problems.

Error detection is the detection of errors caused by noise or other impairments

during transmission from the transmitter to the receiver.

Error correction is the detection of errors and reconstruction of the original, error-

free data.

Error Detection:

When a message is sent, it may be jumbled by noise or the data may be damaged. To avoid this, we employ error-detecting codes, which are bits of extra data appended to a digital message to assist us detect whether an error occurred during transmission.

Error Detection Techniques:

  1. Simple Parity Check:  One extra bit is transmitted in addition to the original bits to make the number of 1s even in the case of even parity or odd in the case of odd parity.  While creating a frame, the sender counts the amount of 1s in it. If even parity is utilised and the number of 1s is even, one bit with the value 0 is added. In this manner, the number of 1s remains even. If the number of 1s is odd, a value 1 is added to make it even.  The receiver just counts how many 1s are in a frame. If the number of 1s is even and even parity is utilised, the frame is regarded as uncorrupted and approved. Even if the number of 1s is odd and odd parity is utilised, the frame is not damaged.  The receiver can identify a single bit flip in transit by counting the number of 1s. However, when more than one bit is incorrect, it is extremely difficult for the receiver to identify the problem.
  2. Two-Dimensional Parity Check: For each row, parity check bits are calculated, which is identical to a basic parity check bit. For each column, parity check bits are computed and

If the result is 0, the data is accepted; otherwise, it is rejected.

  1. Cyclic Redundancy Check: CRC is an alternative method for determining whether or not a received frame includes valid data. The binary division of the data bits being delivered is used in this approach. Polynomials are used to generate the divisor. The sender divides the bits that are being transferred and calculates the remainder. The sender inserts the remainder at the end of the original bits before sending the actual bits. A codeword is made up of the actual data bits plus the remainder. The transmitter sends data bits in the form of codewords.

The receiver, on the other hand, divides the codewords using the same CRC divisor. If the remainder consists entirely of zeros, the data bits are validated; otherwise, it is assumed that some data corruption happened during transmission. Error Correction: Error Correction codes are used to detect and repair mistakes that occur during data transmission from the transmitter to the receiver. There are two approaches to error correction:

  1. Backward Error Correction: When a backward mistake is detected, the receiver requests that the sender retransmit the complete data unit.
  2. Forward Error Correction:

Number of data bits = 7 Thus, number of redundancy bits = 4 Total bits = 7+4 = 11 Redundant bits are always placed at positions that correspond to the power of 2, so the redundant bits will be placed at positions: 1,2,4 and 8. Redundant bits will be placed here: Thus now, all the 11 bits will look like this: Here, R1, R2, R4 and R8 are the redundant bits. Determining the parity bits: R1:

We look at bits 1,3,5,7,9,11 to calculate R1. In this case, because the number of 1s in these bits together is even, we make the R1 bit equal to 0 to maintain even parity. R2: We look at bits 2,3,6,7,10,11 to calculate R2. In this case, because the number of 1s in these bits together is odd, we make the R2 bit equal to 1 to maintain even parity. R4: