Control to shift time for sending beacon frame

dipankar Biswas onedipu at gmail.com
Sun Sep 24 12:03:50 EDT 2006


hi,

I am working in a R&D project, time driven switiching network, goal is to
forward IP packet with respect to time (UTC) along with destination IP
address [1].

Its wireless extension, I was interested, objective is to control over
sending beacon frame from AP.

I know, this work is much more hardware depended and lower MAC layer of
802.11, time synchronization functionality (TSF). Without much knowledge, I
started work with madwifi and I implemented (customized) the idea but
because of close code of HAL (hardware abstraction layer) from atheros, I
could not do following stuff.



Idea is simple: beacon frame is sending according to TSF chipset timer, host
linux kernel is getting another timer, through time-driven network,  there
may be some drift between two timer.  if the drift cross some threshold (say
1 msec), adjust beacon sending time.



In my implementation, I was able to restart beacon sending but I got a
problem, Probably because of close routine :



     1.   it was reseting TSF timer, means it starts with zero again.



   1. to initialize hardware beacon state, I had to give beacon interval
   in TU unit, but in my research, I needed to send beacon millisecond (ms)
   unit interval

( 1 TU = 1.024 ms  ~ 100 ms = 97.65625 TU )

I cannot put non-integer value as beacon interval



I want to try with HostAP driver and ultimately port to some embedded box

My question, is it possible to overcome above two problems without having
any code (or microcontroller) from vendor?



 -

/dipankar



[1]  http://ip-flow.dit.unitn.it/
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