Wireless Networks

 Nowadays, everyone and their pets use a wireless device so how does it all work? Let's take a brief look.

First off, let's only think about 2 devices in a room together that want to communicate with each other, they need to agree on 2 things:

1. Communication set,

2. Radio Frequency or channel to use.

Now if you have a third, a fourth, and a fifth, you need to ensure all the devices meet the requirements within your service set called the Basic Service Set (BSS). In order to do so, you add a device to your network and this is called the Access Point (AP). 

Once you have an Access Point serving BSS over an area, this area will now be called the Basic Service Area (BSA). You now can have communication between different devices in this area through the AP. Note that they won't be able to talk to each other directly, they need to talk through the AP.

All the devices in an 802.11 wireless area network operate only in half-duplex mode.

To distinguish your AP from other APs, you use a unique machine-readable Basic Service Set Identifier (BSSID) which is based on the radio's mac address but since humans are good with names rather than hexadecimal characters, we use non-unique human-friendly Service Set Identifier (SSID).

The devices that connect to your AP are known as 802.11 clients or stations (STA). 

Pretty soon, devices inside the network will want to communicate to devices outside the network, for this the AP is also capable of being connected to an Ethernet device upstream which then forms the Distribution System (DS). 

The AP maps each BSSID to a VLAN. Sometimes, you require multiple BSSIDs on one AP, this is possible by connecting the AP to the switch in a Trunk mode with 802.1Q tags.

Sometimes, one AP just isn't able to cover the area required so we can use multiple APs on a switched network under a single SSID, this is known as an Extended Service Set (ESS).

Another type of requirement is between just two or a group of devices, e.g. end-point devices to a printer. This can be done using Independent BSS (IBSS) also known as an ad-hoc network.

Wireless communication happens through Radio Frequency (RF). A frequency band has a contiguous range of frequencies that can be sliced up into Channels. Radio frequency range is from 3kHz to 300 GHz. The 2 commonly used frequency bands are 2.4GHz and 5GHz. Channels 1, 4, & 6 are non-overlapping for the 2.4GHz band and all channels in the 5GHz band are not overlapping.

802.11 standard was introduced in 1997 with speeds up to 2Mbps on 2Ghz band, then in 1999, 802.11b with speeds of up to 11Mbps was introduced on the same band, on the same year, came out 802.11a with 54Mbps with support for only 5Ghz. Then, in 2003, we got 802.11g with 54Mbps speed operating on 2.4GHz band. In 2009, we got 802.11n with dual-band support and speeds up to 600 Mbps. In 2013, we got 802.11ac, with 5Ghz and speeds up to 6.93Gbps.

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