Everyone thanks for coming back to another chapter for Wi Fi fundamentals with location and analytics. This course will help you to muster the air. One of the key topics in Wi Fi understanding is frequencies. It is the medium where your network operates. And although it seems as if it comes as a second nature to your deployment, the choice between the right frequency the channel and its width is crucial to a lasting good experience. Wi Fi operates mostly under the 2.4 gigahertz band and the five gigahertz band.
The reason is regulation. Wi Fi is aimed at us within the isn bands, an unlicensed spectrum that enables users to access directly A spectrum without the need for the regulation and restrictions. The Aysen ban the industrial, scientific and medical bands are reserved the worldwide for the use of radio frequency energy for industrial, scientific and medical purposes. By choosing the right frequency, you're actually saying, This is the highway where my data will travel, the width of the roads, the faster it is, but hey, there still can be traffic jams if not planned, right. Let's see which highways and roads are around. I'm using Wi Fi Explorer, a free great tool for Mac users.
We can see the SSID is the name of the wireless networks and there is their signal strength, their rssi and even the signal to noise ratio, the difference between the signal strength and the noise around and that the right there is the frequency band. And guess what, most of the networks, at least where I live operate under the 2.4 gigahertz band. The channel number varies, but the width stays mostly the same 20 megahertz. Let's go back and understand what we had just seen. So what are we up to today, we will look at the different techniques used to spread the signals, your Wi Fi signals in the air, we will look at the good old 2.4 gigahertz band, which is still used today as you've just seen widely in access points and just about any Wi Fi product. There are some symptoms related directly to the 2.4 gigahertz band and we will understand them.
We will also look at the five gigahertz band which is for the last couple of years became the standard. The five gigahertz band is the highway with an unlimited roads. And we will look at DFS and TPC built in mechanism that helps our network in different five gigahertz situations. We will start with the 2.4 gigahertz band which is probably the most widely used and let's understand some key terms. The 2.4 gigahertz frequency band starts from 2.4 gigahertz up to 2.5 gigahertz. The band is actually a small section of the spectrum frequency.
It is divided into portions each five megahertz wide in Wi Fi we use channels which are actually aggregated portions, the band is divided into 13 channels each is 20 to 22 megahertz wide. We represent channels by their center frequency. So for example, channel six which is a 20 megahertz wide channel, an aggregated channel is represented as 2437 megahertz, that is its peak frequency. And as you can see it is actually spreading all over starting from the fourth up to the a4 portion of the band. So, if we have 13 channels occupying that band, you will see that only three are not overlapping. So, we have our white fi signal sent in the 2.4 gigahertz frequency band to the air and how it is being spreaded over the band.
Well as you will see, it is also a crucial criteria. The way they spread can be seen as a truck and as a racing car. The first spread spectrum technology that was used for many years in standards as 802 11 B was DSS. This assess is like a truck. If a channel is a road in our highway, then this assesses a truck that occupies the road from one side to the other. The signal is spread over a range of frequencies.
In the latest Wi Fi technologies, we use OSPF OFDM is like a racing car. We don't just send the signal over the entire spectrum of DSS rather it is being splitted to sub carriers 50 to narrow bandwidth chunks, each on a different frequency. OFDM is key to my mom, which is a topic we will deal in another video signals are sent in parallel and over a much longer time. Sending so much subcarrier makes decoding the signal much more reliable. Even if the signal as we know degrades over distance, you have a lot more signal that can be recovered. The 2.4 gigahertz frequency band is narrow and so it has its own symptoms as co channel interference and more.
More In the next chapter