Wifi Concepts

 

Wifi Signals

The main ISM or the Industrial Scientific and Medical bands used for carrying Wifi Signals are

2.4 Ghz

5 Ghz

Ref : https://www.electronics-notes.com/articles/connectivity/wifi-ieee-802-11/channels-frequencies-bands-bandwidth.php

These 2 bands are split into smaller frequency bands called channels. The frequency range for each channel is called the channel width. ( 20MHz, 40MHz, 80MHz)

2.4 Ghz

The 2.4GHz frequency band, covers a frequency range from 2400 MHz to 2500 Mhz which is 100MHz range. This 100 Mhz range is divided into 14 channels , with each channel 20MHz wide. There is a gap of 5MHz between adjacent channels.


 The adjacent channels overlap in frequency. Overlapping channels cause interference during transmissions Only 3 channels can be active at a time. There are many groups of non-overlapping wifi channels, ie 1, 6 , and 11, 2,7, and 12

This is used by 802.11b, 802.11g and 802.11n

5GHz Band


The 5GHz frequency band, covers a frequency range from 5725 MHzto 5875 MHz which is 150MHz range. There are 24 non overlapping channels in the 5GHz band. This is used by 802.11a, 802.11n and 802.11ac

Many devices like microwaves , baby monitors, cordless phones bluetooth devices use the 2.4GHz band. So 2.4 GHz band is more susceptible to interference. Since 5 GHz has non overlapping channels , it is less susceptible to interference.

2.4 Ghz covers a longer distance, but more susceptible to noise. Since lower frequency signals have lower attenuation, so signals travel a longer distance. 5GHz offers better performance in terms of throughput, due to non overlapping channels , less susceptible to noise. However , in terms of coverage , lesser distance than 2.4GHz.

20MHz and 40MHz

40MHz channel has higher throughput than 20MHz channel. But 40 MHz channel reduces the number of non overlapping channels, so more interference.

802.11n introduced the concept of channel bonding where 2 adjacent channels can be combined to create one wider 40 Mhz channel.

5GHz 20 Mhz channel

For maximizing the amount of non overlapping channels, prefer 20 MHz channel over 40 Hz channel. In areas of dense deployments where interference is higher, 20MHz channel better.

5GHz 40 MHz channel

By using 40MHz channel, better throughput can be achieved. Non overlapping channels are available even after using 40 Mhz channel.


 


 


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