What's new

Are STBC mandatory for 802.11n?

  • SNBForums Code of Conduct

    SNBForums is a community for everyone, no matter what their level of experience.

    Please be tolerant and patient of others, especially newcomers. We are all here to share and learn!

    The rules are simple: Be patient, be nice, be helpful or be gone!

Esurnir

New Around Here
STBC for those who don't know are "Space Time Block Code" the feature of 802.11n that is supposed to extend the range to infinity and beyound. By using "an extra" antenna per transmission (typically, 2 antenna total for a MCS 0-7) your system will transmit the same data in two different version (Alamouti code, one example using two antenna will send this : http://upload.wikimedia.org/math/e/e/4/ee4bffb7ebd93995d80d85fd8b50677f.png horizontal is the antennas, vertical is time ).

Now the thing is while capturing traffic using Airpcap (802.11g version, I need to sell a kidney for the 802.11n version), I discovered this payload to one of my probe packet sent through a Intel wifi link 5100 AGN "draft N 2.0" certified.
http://img14.imageshack.us/img14/8711/80211nhtcap.png

You'll notice two "improvement" of 802.11n are unsupported on this card :
The Low Density Parity Check coding is unsupported, it's a drop in replacement for the g convolutional coding that can be used interchangeably in .n packet, supposed to be more error resilient, but is more computing intensive isn't supported.

And those .n STBC have been sent to the garbage too...

It seems the only "mandatory" and advertised functionality of this card is the support of supperior MCS and throughput (up to 15 with 40Mhz, the 300 Mbps one). However, the "resilience/longer range" enhancement brought by 11n have been quietly rendered optional.

Is the draft mandating the support of STBC and LDPC, or has it been sent to the optional can for STA ?

P.S. I forgot to add that LDPC also permit you to increase your bitrate. And STBC is one of the two mimo mode.
 
Last edited:

Latest threads

Sign Up For SNBForums Daily Digest

Get an update of what's new every day delivered to your mailbox. Sign up here!
Top