Point coordinator functions / HostAP

Dave Edwards Dave.Edwards at abicom-international.com
Fri Mar 14 09:36:34 EST 2003

Hi Folks,

The Intersil Prism 2 chipset does not support PCF under hostap. The 
firmware blocks the CF frame types so it is impossible to either send or 
receive a CF-POLL.

I suspect the Prism 2.5 and Prism 3 firmware does exactly the same.

Sony have implemented a PCF mode using modified AP firmware from 
Intersil. However, I suspect that they had large pockets to achieve this.

Another issue here, associated with the Prism 2 chipset is it's appaling 
IO performance. If you implement a PCF like protocol then you will 
shortly discover that it can take upto 200uS to read/write a frame of 
data, which gives you an interframe gap of the order of 400uS + 
Interrupt latency + Processing delay! Since the PCF standard specifies a 
PIFS frame spacing, you will quickly see that it's impossible to achieve.

Outside of this, you will also need to generate PCF beacons from the 
radio. At present there is no way to do this.

My apologies for being a PITA but I've spent the past few months looking 
at this


Andrew Langrick wrote:

>>I am looking for an implementation of the PCF MAC layer access 
>I am a final year student at the University of Bristol and I am working 
>in the area of quality of service for 802.11 networks.  I aim to 
>implement the PCF for the Host AP package. I have not been working on 
>this for very long and so have not made alot of progress.
>>Do you know any available AP products that implement this access 
>method ?
>I have done some online research into this but I have not found any 
>products that implement the PCF. 
>I could do with some help. Is there anyone with a good knowledge of the 
>source code who could advise me on some aspects of this? I would be 
>very grateful for any help.
>Andrew Langrick
>HostAP mailing list
>HostAP at shmoo.com

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