Overview of Wireless LAN/ Wi-Fi / IEEE802.11

As the competition in businesses/corporates is increasing, every minute counts and hence the demand for more productivity, faster response, lower costs is constantly increasing. No doubt, Wired LAN is used most commonly in almost all business / corporate offices, however, if the employer/employee wants to access the even when not present with the traditional desktops, it was not possible. And such kind of demands gave raise to the concept of Wireless LANs.

IEEE 802.11 is the Wireless LAN standard from IEEE (Institute of Electrical and Electronics Engineers) . 802.11 Wireless LAN is commonly referred to as "Wi-Fi" (Wireless Fidelity).

In Wireless LANs, computers, workstations, laptops etc., communicate data with each other using radio waves or infra red light as the transmission medium. Radio transmission (in the 2.4 GHz licencese-free ISM band) is more popular.

Benefits of Wireless LANs:
-> Since, it is not required to use cables or wires to connect to, you can access the required information while moving between floors of your office.
-> Since, it is possible to access information from anywhere (of course, in the vicinity of the coverage area), it is possible for employees to access the key applications and respond quickly to customer queries. Thus, increasing productivity.
-> It is easy to set up since, cables installation is not required
-> Easily add new network elements.
-> Since, wireless networks eliminate or minimize wiring, cost of wiring is eliminated or reduced.
-> Due to the advances in wireless technology, provides robust security protection.

This is just a very brief overview. I will be adding further technical details in another post soon.

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Data communicaitons - CRC Error Detection code

We know that as the data is transmitted, there will be errors introduced, resulting in the change of one or more bits in the transmitted frame. Hence, it is necessary to detect any errors in the transmitted datat to make that what was transmitted is what is received. For this purpose there are many Error detection schemes viz., Parity Check, Cyclic Redundancy Check (CRC) have come up.

CRC is the most commone and one of the most powerful error-detecting codes.

CRC can be described as follows:
"Given a k-bit block of bits, the transmitter generates an n-bit sequence known as a "frame check sequence (FCS)", so that the resulting frame, consisting of (k+n) bits is exactly divisible by some predetermined number". Then, the receiver divides the incoming frame by that number, and, if there is no remainder, then assumes that there is no error".

There are 3-ways for implementing CRC viz.,
1) Modulo 2 arithmetic
2) Polynomials
3) Digital logic

Out of these, Polynomial representation is mostly used. In this representation, CRC generator is represented by an algebraic polynomial with binary coeffecients. Most commonly used polynomials are CRC-8, CRC-10, CRC-16, CRC-CCIIT and CRC-32. The numbers 8, 10, 16, and 32 refer to the FCS. CRC-CCIIT also results in 16 bit FCS.

CRC-32 is used in IEEE-802 (LAN).

I will be adding more details on CRC soon. Please, keep checking for new articles.

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