IEEE 802.11 Fundamentals – Understanding the Wave

jonathan CCIE Wireless Written Leave a Comment

Ok, again I’ve been late posting but in my defence I’ve been away for a while and I’ve also attended a conference over East for a few days which scuppered my blogging plans. I know it’s not a good start but I actually have put together a number of posts into docos that I will post over the coming days. These posts will discuss radio waves and their utilisation in transporting digital data between network devices. Before we go into this we need to understand what a wave is, its key properties within the 802.11 space and how it is measured. Radio waves are a type of electromagnetic radiation that was first theorised by James Clerk Maxwell in 1864. Heinrich Hertz used this idea to create the first radio device in 1886 which was capable of sending and receiving these electromagnetic waves over the air. This radio was also able to increase the number of waves in a given time period and the speed of waves. The creation of this first radio led to the unit which measures one complete cycle/oscillation per a second to be defined as the Hertz. I hope that you now understand by what is meant by the terms MHz and GHz. MHz equals Millions of waves per a second while Ghz equals Billions of waves per a second. WiFi Slope

The wave itself mathematically takes a sinusoidal shape, commonly known as a sine wave which you can see in the picture above. I’ve already mentioned that one complete sine wave is called a “cycle or oscillation” but there are a number of other properties that we should also note. A wavelength is the distance of which it takes to complete one sine wave while frequency is how many times a complete sine wave is repeated within a second. The wavelength and frequency are closely related in that the frequency is inversely proportional to the wavelength which means that the longer the wavelength, the lower the frequency and the higher the wavelength, the higher the frequency. There are also a couple of other important properties namely amplitude and phase. Simplistically amplitude is the measure of how big a wave is, the bigger the wave the more energy it carries. In our case, we measure the amplitude from the equilibrium point to the crest or trough of the wave. Phase is a measure of the slope, angle or direction of the wave at any point in the wave cycle. There are mathematical formulas for all of these wave properties but I won’t go into these as I’m generally trying to keep my posts relatively short. The next posts will take a look at the spectrum and modulations.

 

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