Arch Linux

wtx

Member

Registered: 2014-06-09

Posts: 82

802.11 preamble

Hello,

I'm writing wifi driver for Linux and I've got some problems with it.

I'm using time division transmission schema (30 ms in one direction and 5 ms in the opposite one). For my scheduler I need to know how much time will take transmission of one frame by given bitrate.

At the moment I'm using following formula:

frame_duration = skb->len * 1000000 * 8 / (bitrate * 1024) + 144

where:

bitrate is in kbit per second, skb->len is measured in bytes and frame_duration in microseconds.

I know that there is also 802.11 preamble which I should take into account - and at the moment I assume that it takes 144 microseconds.

I'd like to ask if I computing the frame transmission time correctly, and if not - what am I doing wrong?

Anyone knows how long are the 802.11 preambles in microseconds for several available bitrates?