Error detection in Data comunication

1. WELCOME

2. DETECTION

3. Presented By
Anika Ohab
ID:142-15-3568
Abul Hasnath
ID:142-15-3532
Shahinur Rahman
ID: 142-15-3606
Umme Habiba
ID: 142-15-3677

4. Introduction
kinds
redundancy
Block coding
Parity check
LRC
CRC
checksum
Contents

5. ERROR DETECTION
In networking, error detection refers to the
techniques used to detect noise or other
impairments introduced into data while it is
transmitted from source to destination.
Error detection minimizes the probability of
passing incorrect frames to the destination,
known as undetected error probability

6. Types of Error
Error
Burst
Error
Single-
Bit Error
If the signal is carrying binary encoded data,
such changes can alter the meaning of the data.
These errors can be divided into two types-

7. In a single-bit error, only one bit in the
data unit has changed.
Note:
Single-Bit Error

8. A burst error means that 2 or more bits
in the data unit have changed.
Note:
Burst Error

9. Error detection uses the concept of
redundancy, which means adding
extra bits for detecting errors at the
destination.
Redundancy

10. Redundancy

11. Popular techniques are:
Block Coding
Parity Check
LONGITUDINAL REDUNDANCY
CHECK
Cyclic Redundancy Check (CRC)
Checksum

12. Block coding
Data
Words
Code
Wards
00 000
01 011
10 101
11 110
k=2,n=3

13. Simple Parity Checking
Even Parity:1 is added
to the block if it
contains an odd
number of 1’s and 0 is
added if it contains an
even number of 1’s.

14. Even-parity concept

15. Two-dimensional parity

16. Simple parity check can detect all
single-bit errors. It can detect burst
errors only if the total number of
errors in each data unit is odd.
Note:

17. LONGITUDINAL REDUNDANCY CHECK
LRC
LRC 10101010
Data plus LRC
11100111 11011101 00111001 10101001
10101001
00111001
11011101
11100111
11100111 11011101 00111001 10101001 10101010

18. CRC encoder and decoder

19. The last error detection method we discuss here is
called the checksum. The checksum is used in the
Internet by several protocols although not at the
data link layer.
However, we briefly discuss it here to complete
our discussion on error checking.
Checksum

20. We can make the job of the receiver easier if
we send the negative (complement) of the sum,
called the checksum.
In this case, we send (7, 11, 12,0,6, -36). The
receiver can add all the numbers received
(including the checksum).
If the result is 0, it assumes no
error; otherwise, there is an error.
Checksum

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