Communication Technology What is Pseudo Random Number ?   You would know what a Random Number is. Even if you may not able to define explictely a random number, you would have some intuitive understanding of your own and I think it is right. What does it mean by 'Pseudo' ? If you google it or look into a dictionary, the common definition of 'Pseudo' would be 'not-genuin'.... a kind of fake. Combining these together, you would define 'Pseudo Random Number' as 'nongenuin random number' or 'kind of fake random number'.   Again by googling, I got a definition that I like (short and clear) as follows : (of a number, a sequence of numbers, or any digital data) satisfying one or more statistical tests for randomness but produced by a definite mathematical procedure.   My own definition of Pseudo Random Number is as follows : A sequence of numbers that look like random number sequence (a sequence of random numbers), but we know exactly how it is generated and we can duplicate the exact sequence if we are given a few required information.   If you are interested more in the definition, refer to the document in Reference section or google it further. I don't think I need to talk any further on the definition.       Why we talk about Pseudo Random Number in communication theory ?   In communication system, there are many cases where you want to randomize some data in a specific structure so that you can un-randomize when you want. Why do you want to randomize ? There would be several reasons For Security reason : I want to make my data hard to be recognized by somebody else For physical / electrical reason : this is especially important in digital communication. By randomizing, you can convert any data in such a way that it has almost same number of 1s and 0s with even distribution and this makes synchronization easier in electrical circuit.       What kind of Pseudo Random Number (Sequence) are used in communication system ?   There are many different types of Pseudo Random Number that are used in communication system. Usually they are named by the algorithm or properties of the sequence. Followings are some of the examples These are a few commonly used Algorithm to generate a pseudo random number. Followings are some of real application how these algorithms are used in communication system.       Reference :