WIRELESS LOCAL AREA NETWORK (WLAN)
WHAT IS WLAN?
Let’s keep simple two or more device communicate using wireless is called as WLAN. Ex: In our home mobile or laptop are connected with router as WLAN network.
But How we connect without wire?
The answer is WI-FI network adapter,
mostly every laptop as WI-FI card (NIC: Network interface card) it is responsible for WI-FI connection.
Frequency:
The number of waves that pass a fixed
place in a given amount of time.. In simple the in visible wave (for human eye) which keeps
flow to particular direction. Chill, this not a physics class. WI-FI also
produces frequency.
Note: WI-FI emit both 2.4GHz and 5GHz.
Did you know: 2.4GHz is free to use that’sthe
reason most of the device will work on
2.4GHz.
2.4GHz:
What is 2.4GHZ? It is a frequency, in wireless communications, it refers to
a wave oscillation.2.4GHz totally contain 14 channels but most of the countries
they followed 11 channels shown diagram: 2 in this 11 channels out of 3 channel
are non-overlap channel.
Non-overlap
channel:
In diagram: 2 the
blue lines are consider non-overlap but why? 2,3,4,5 lines are interact or
overlap with both channel 1 and 6. Channel 11 also follow same rules.
Most of the device works on 2.GHZ
channels for ex: Bluetooth, Micro oven etc. so there will be possible that the
frequency are collision with each other.
Note: Overlap reduce the
performance
For ex: imagine you have
four router in 2.4 GHz support only 3 channel. Imagine router A is in ‘1’ channel, router B is in ‘6’ channel,
router C is 11 if you try to connect a router D it will cause interference why?
Because it will overlap with routers.
Note: Micro oven,
Bluetooth also work on same 2.4 GHz
. You can check your home router channel:
Step1: In
windows search bar type “CMD” click enter.
Step2: type
“ipconfig” click enter
Step3: find default gateway ip address
Step 4: Copy the default gateway ip address and open browser
paste it hit enter.
Step 5: Now you are in router home page give user name and
password (you can find that on your router backside).
Note: Many routers are set up to automatically choose
what Wi-Fi channel to use; and they may not choose 1, 6, or 11.
5GHz:
Compared
with 2.4 GHz 5 GHz is more fast and it as many channels. In 5GHz diagram you
can see the bandwidth (20, 40, 80,160 MHz). What is bandwidth? Every channel
(36, 40, 1, 6, and 11) has have a width ex: imagine channel as a truck, the
truck have a width in that width packets are travel if width increased the
‘throughput’ (speed) also increased. I hope know got some idea .In 5GHz diagram
bandwidth increased the channel width also increased.
5GHz
channel classified as two type
DFS (Dynamic frequency spectrum)
NON-DFS
DFS:
Dynamic frequency spectrum channels are U-NII-2A (52 to 64) and UNII-2EXTENDED (100 to 144).
The purpose of the DFS channel is radar and military
avoidance.
Before an AP will use a channel
that may be impacted by radar, it will perform a “Channel Availability Check”
to check for radar signals on that channel. The AP will listen for 60 seconds
for the presence of radar signals. If no radar is detected, then the channel is
designated as being an “Available Channel”.
When powering up an AP that uses a DFS channel,
you will see that the 2.4GHz radio becomes available as soon as the AP has
completed its boot sequence, but the 5Ghz radio may not available for another
minute. This is due to the AP performing its channel availability check, if the
AP is trying to use a DFS-impacted 5GHz channel.
Where channels 120 – 128 are allowed for use by
Wi-Fi networks, there may be an increased channel availability check of 10
minutes. This means that the 5GHz radio is not available until 10 minutes after
the access point has booted up.
Note: wants know more about DFS: click here
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