Electronics > Beginners

Wifi Bandwidth - what am I missing?

(1/2) > >>

paulca:
So a normal Wifi channel is 20Mhz wide.  A higher rate channel is 40Mhz wide.

However the data rates supported on those channels (on 2.4Ghz) are 54Mbps and 108Mbps.

I missing something, but if memory serves me right, "bandwidth" is originally, literally that, the width of the band.  Now if I have a 20Mhz bandwidth, then surely my maximum data rate is 20Mhz/2 = 10Mbps.

What am I missing?

IanB:
1 MHz ≠ 1 Mbps

Paul Rose:
Nyquist formula in a noise free channel:

Rate = 2 * Bandwidth * log2( Number of Signal Levels )

There are lots of resources out there.  Here is one at random:

https://witestlab.poly.edu/blog/nyquist-formula-relating-data-rate-and-bandwidth/

TK:
It is the modulation scheme (64 QAM for 802.11g) what gives you 54Mbps with WiFi.  802.11n / 802.11ac can do 256QAM modulation.  Cable Modem uses similar modulation schemes to achieve 1Gbps. 

IDEngineer:

--- Quote from: TK on September 24, 2018, 07:58:00 pm ---It is the modulation scheme (64 QAM for 802.11g) what gives you 54Mbps with WiFi.  802.11n / 802.11ac can do 256QAM modulation.  Cable Modem uses similar modulation schemes to achieve 1Gbps.

--- End quote ---
Exactly this. Modulation decouples you from a strict "bandwidth to bitrate" relationship. Spend a little time Googling modulation schemes - then think about how you'd craft a receiver to decode some of the dense constellation ones in real time.  :o

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod