Thursday, 20 October 2016

802.11n + 802.11ac data rates and SNR requirements


When designing a wireless network that requires very high data rates per client device, it is critical that you understand what conditions need to be met in order for the client devices to hit those rates (maybe a post for another time).

At the end of the day it comes down to one factor: A higher Signal-to-Noise Ration (SNR) will produce a higher data rate.

I have two sites bookmarked in my web browser to remind me of those requirements.

http://www.revolutionwifi.net/revolutionwifi/2014/09/wi-fi-snr-to-mcs-data-rate-mapping.html

and

http://mcsindex.com/

Both authors have obviously done an incredible amount of research to gather the data so I absolutely in no way pretend to have put together this myself. The Receive Sensitivity/RSSI requirements have been compiled from various sources and should only be used as a guide as each vendor radio will have their own specifications.

Anyway... I got tired of flicking between the two sites above so I decided to create a chart that merges the two. It has become my one stop shop for quickly determining the SNR requirements for a required throughput (I lie, there are two charts, one for 802.11n and one for 802.11ac.)

I recommend having a read of the first post. Andrew Von Nagy has done an amazing job on explaining the how MCS rates are achieved...


802.11n
 802.11ac
For those that don't have the ability to download the images in HD; I have provided a link to the original excel document - 802.11n/ac data rates and SNR requirements

I welcome all feedback!

-Brett

5 comments:

  1. Hi,
    nice blog however, I think I found a typo in it.
    The table of 802.11ac contains for 20 MHZ, for every VHT MCS index 1(SS1, SS2 and SS3) a wrong RSSI. It mentions RSSI of -97 while I expect it should be -79. Can you check and correct please? Can you also provide an xls copy of this table to me as the image is not fully HD quality.

    Kind regards,
    Tom

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    Replies
    1. Hi Tom,

      You are absolutely correct! I referred back to my original sources and it should indeed be -79 dB. Thanks for the feedback :-) I have updated the post. I have also included a link to the original Excel file. It seems I have hit a resolution and/or file size limit with the 802.11ac image.

      -Brett

      Delete
  2. where did you get the SNR data from? is your NF 7dB ...174-10*LOG10(80*10^6)-7-51

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  3. SNR=174-10*LOG10(80*10^6)(BW)-7(NF)-51(sensitivity)

    ReplyDelete