A talk by one of our engineers at Conversocial (Luke Ross) on why WiFi is rubbish

1. Why WiFi is rubbish

2. WiFi from 30,000 feet
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Devices register with the
access point (AP)
Once registered, data is
transferred between a device
and the AP
Each device has a “time
slice” where it communicates
exclusively with the AP.
To communicate between
devices, data must be
relayed via the AP.
Note the lack of direct connections between devices

3. My 450M is better than your 100M

4. WiFi = shared bandwidth
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That 450M is shared amongst all devices
In the cabled network, the 100M link is
per-cable
WiFi: bandwidth is shared by all links
Cable: each link is independent

5. Distance matters
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The 450M assumes all devices communicate at the
maximum rate
If a device is too far away from the AP it will
communicate more slowly, just as we talk more slowly if
there is a lot of background noise
Devices that “talk slowly” will use more than their “fair
share” of time, shortening communication slots for
everyone else.
Devices that use an older WiFi standard (eg. 54M, 11M)
also slow down the network for the same reason.

6. Distance matters
Shared bandwidth; everyone is limited
by the distant device.
Only one link goes more
Slowly – the others operate
at full speed.

7. Also shared with other networks
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...that operate on your channel
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There are only 13 channels to choose from
Although they are separate networks, if they are on the same channel
they share the same bandwidth

8. Did I say 13 channels?
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To make it worse, channels extend into the
neighbouring channel – channel 2 covers
channels 1 – 3
In reality, there are only three completely
independent channels
1
2.412
2
2.417
3
2.422
4
2.427
5
2.432
6
2.437
22 MHz
7
2.442
8
2.447
9
2.452
10
2.457
11
2.462
12
2.467
13
2.472
14 Channel
2.484 Center Frequency
(GHz)

9. Sharing with ⅓ of local networks
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Did I mention that Bluetooth uses the same
spectrum, as well as some cordless phones,
wireless headphones, video senders...
A network scan in the office – can you find all the
Conversocial networks?

10. So how do big networks do it?
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Lots of APs wired together!
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… so the devices are always close to one
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… APs on different channels
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APs share a name (SSID) – handover typically
messy

11. TL;DR
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WiFi is great for light use
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...but infuriating for serious use
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Works best for everyone if we all use it lightly
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...and remember to stay close to your access
point
But: don't share your bandwidth, love your
network cable!