Explain about hamming error correcting code, Computer Engineering

Assignment Help:

Q. Explain about Hamming error correcting code?

Richard Hamming at Bell Laboratories worked out this code. We will only introduce this code with help of an illustration for 4 bit data. Let's presume a 4 bit number b4, b3, b2, b1.  In order to create a simple error detection code which detects error in one bit only we can just add an odd parity bit.  Though if we want to find which bit is in error then we may have to employ parity bits for different combinations of these 4 bits in such a way that a bit error can be recognized uniquely.  For illustration we can create four parity sets as below

Source Parity                            Destination Parity

b1, b2, b3                                                        P1                                            D1

b2, b3, b4                                                        P2                                            D2

b3, b4, b1                                                        P3                                            D3

b1, b2, b3, b4                                                  P4                                            D4

Now very interesting phenomenon can be noticed in above displayed parity pairs.  Assume data bit b1 is in error on transmission then it will cause alteration in destination parity D1, D3, D4.

ERROR IN                                                     Cause change in Destination Parity 

(One bit only)

b1                                                                                             D1, D3, D4

b2                                                                                             D1, D2, D4

b3                                                                                             D1, D2, D3, D4

b4                                                                                             D2, D3, D4

Figure: The error detection parity code mismatch

So by simply comparing parity bits of source and destination we can recognize that which of four bits is in error. This bit then can be complemented to eliminate error. Please note that even source parity bit can be in error on transmission but under assumption that just one bit (irrespective of data or parity) is in error it would be detected as just one destination parity would be different. What should be length of error detection code that detects error in one bit? Before responding this question we have to look in comparison logic of error detection. Error detection is done by comparing two ‘i’ bit error detection and correction codes fed to comparison logic bit by bit (see figure below). Let’s have comparison logic that produces a zero if compared bits are same or else it generates a one. Consequently if similar Position bits are similar then we obtained zero at that bit Position however if they are dissimilar that is this bit position may point to an error then this Particular bit position would be marked as one. This way a matching word is built. This matching word is ‘i’ bit long so can signify 2i values or combinations.


Related Discussions:- Explain about hamming error correcting code

Displays a format of floating-point number, Q. Displays a format of floatin...

Q. Displays a format of floating-point number? A floating binary number +1010.001 in a 16-bit register is able to be represented in normalised form (presuming 6 bits for expone

How can we send data to external programs, How can we send data to external...

How can we send data to external programs? Using SPA/GPA parameters(SAP memory). Using EXPORT/IMPORT data (ABAP/4 memory)

Define hex directive, Q. Define HEX directive? HEX: HEX directive enabl...

Q. Define HEX directive? HEX: HEX directive enables the coding of hexadecimal values in body of the program. That statement directs assembler to treat tokens in source file wh

Types of software - computer architecture, Types of software: A layer ...

Types of software: A layer structure is described where Operating System is located on generally used software systems on desktops   System software System sof

Define parity bit and list its types, Define parity bit and List its types....

Define parity bit and List its types. The most common error detection code used is the parity bit. Parity bit is a extra bit contained with a binary message to make the total n

What is digital switch, Digital switch It is a device that handles digi...

Digital switch It is a device that handles digital signals formed at or passed by a telephone company's central office and sends them across the company's backbone network.

Smli firewalls are different from the conventional, SMLI firewalls are diff...

SMLI firewalls are different from the conventional The SMLI firewalls are different from the conventional "stand in" proxies in a way that the stand-in proxies are used for th

What is expansion swap, What is Expansion swap? At the time when any pr...

What is Expansion swap? At the time when any process needs more memory than it is currently allocated, the Kernel performs Expansion swap. To do this Kernel reserves enough spa

Make a generalize program to performs r-ary subtraction, Q. Make a genera...

Q. Make a generalize program that performs r-ary subtraction on two numbers using (r-1)'s and r's complement? Use input and output files.

Basic need of search engines, Q. Basic need of Search Engines? Search E...

Q. Basic need of Search Engines? Search Engines are programs which search the web. Web is a big graph with pages being the nodes and hyperlinks being the arcs. Search engines c

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd