Hi all,
We are WISP and we install all new outdoor WLAN nodes with MT hardware now AND we are changing some existent APs (LANCOM) to MT due to HW damage etc …
we have seen some special quality Problems, which we cannot understand. Maybe someone knows an answer but it seems to be an SW problem within MT drivers i think.
We use a lot of COMPEX WP54ag and also a lot of MT-clients in our network. If we change the LANCOM AP against MT-AP with latest firmware (V3.14rc1 too) we did see significant packet loss to our COMPEX outdoor clients at same sttings. We had 0% packet loss prior the swap. the loss is 4-10% with MT-APs depending on the packet size, distance etc … we tried different encryption settings with no difference.
only the following settings did solve most problems:
- the WLAN settings on the MT-AP to a maximum of 24MBit (!!!) did solve the packet loss problem. Its interesting that its exactly 24MBit and it doesn’t mainly differ on signal quality distance etc …
- the ack-timeout goes with dynamic settings up to 408us automatically (if none MT clients are involved). its not 100% clear for me why, because i thought, that MT-AP can dynamically assign the ack-timeout on AP side also with non MT clients. calculation of right timeout should be possible - i think. also detection of right speed. The high assigned ack-timeout doesn’t make any problems on shorter (i think up to 5km) distance. which i would understand, because higher acc should only take more time on packet retry if lost. BUT: on high distances (?!?!!?) it makes great troubles if we dont set manually. We had to set the value to e.g. 150us for app. 18km and after that it did work correctly with very few packet loss !
also interesting detail which we have seen in the past:
- MT-clients have better delay time if the WLAN settings are at a maximum of 24MBit (??). No packet loss, but delay time much more stable. This is best to see in smokeping graphs.
- The last WLAN driver improvements of MT did solve some problems (WPA2 connect, more stable dlelay time, fewer packet loss on some links, fewer disconnects), but not all …
- We have also seen, that MT-clients have more problems to MT-APs than to LANCOM APs, if the signal quality is few (!). On connections MT-APs to MT-clients the result is better in most cases, if we change to nstreme. But we can do this only if we have only MTs at this antenna … (hey! - it would be very GREAT (!) if the clients in station mode could detect nstreme automatically, its hard job to change all clients manually and than the AP:)
So best result is still:
LANCOM AP and COMPEX clients or MT-clients with 24MBit speed setting.
summary:
I like MT much ! its really a great solution and MT has a great support team. I know a lot of big companies which have very bad possibilities (and willing) to solve such problems as described here.
Is it possible to solve these problems ? I would be very very happy 
i am willing to spend all time needed and sending reports to help solving these problems.
If someone is interested in, see also topic: http://forum.mikrotik.com/t/outdoor-performance-problems-on-standard-mode-with-v3-x-ptp/23333/1
This describes our seen problems on PTP links, maybe these problems have the same source (timing problems inside WLAN driver, don’t know ?!?!?).
Thanks for help !
DieterK