[LINK] Senator Coonan on 7:30 Report

[Saliya Wimalaratne]

On Tue, Jun 19, 2007 at 11:10:27AM +1000, Richard Chirgwin wrote:
> Jan Whitaker wrote:
> 
> Sal: Timing is an issue for mobile base stations because it's part of 
> the decision of which base station your phone logs into. It doesn't come 
> into play in a single point-to-point connection such as WiMax for last 
> mile connections.

Hi Richard, 

actually, it does :) All the common (WiMax included) WLAN protocols
use CSMA/CA - the timing element means that there is a 'maximum distance'
that the protocol will work well at. Beyond this distance, insufficient
time slot length is allocated for ACKS so that collisions go up and 
throughput goes down. 

It's generally acknowledged that timing setting needs to be the same on 
both ends of the link - and, as I said, I don't think that any of the 
WLAN protocols allow for dynamic negotiation of this timing. There is
hardware (e.g. Mikrotik) out there that does dynamic negotiation; but
I believe that this is a vendor-specific enhancement to their products.

For a better explanation than mine, have a look at:

http://madwifi.org/wiki/UserDocs/LongDistance#ACKtimeoutandSlottime

Regards,

Saliya