Hi all

we are running several access points in a small town and currently have around 50 clients.

Over the last few weeks we have been experiencing interfearance issues (i think). The problem is that all appears good but clients report slow browsing speeds.
I have checked everything!!!!!!
Average signal strenght is around -70 and SNR is over 20 for most clients.
What I have noticed is that although the TX is usually 11mbps, the RX is very often 1mbps. Although I cannot pinpoint or confirm the interfearance, at times of the day all seems fine and at others it's impossible to browse. The CCQ can vary greatly. For example we have a client connected and -66 with an SNR of 34 but the TX CCQ goes up and down from 10 to 50%. I cannt see the RX CCQ as it is not MT CPE but I guess it's not much better.

Even on antennas with only 2 or 3 clients connected and no one downloading anything. Yet if I connect with my laptop at short range I can browse and do anything.
What I think the problem may be is that B can only handle 11mbps theoretical and about 5-6 mbps actual speed. When the TX or RX falls back to 1mbps, the actual speed is much lower than that hence dropping packets and creating a low speed connection.
BTW all clients are set to 96k/256k if that matters.

I thought of 2 possible solutions:
1) increase the B basic rate to 2mbps for both the MT router and each client CPE (non MT). Hopefully this would increase the minimum communication speed.
2) switch to G onlys seen that the basic rate is 6mbps. and set all CPE for G only and 6mpbs minimum.

I am aware that switching to G will limit my range. But I much rather have better connections at shorter range that moaning clients at any range.

Also I know that B can handle 200 packets per second. Can anybody tell me how many G can handle? I am thinking about our VOIP clients and the congestion sometime is created by torrents.

Any advice would be great

Thanks

David

Sounds like you may have interference have you done any scans and are your aps using omis? If you using omis you pick up crap from all over and it can be a big problem. Move to sectors if possible.

If many of the clients do not have clean radio (no freznel zone intrusion) you may be seeing problems due to reflections, from fixed or moving objects like cars. But with out knowing your lay out it hard to say.

In general b should do a better with interference as the modulation type are lower and they need less signal to noise to operate. If you try g you may want to disable the highest modulation (like 54,48,36).

Erik

David, did you find solution to your question?

I have simular problem...Signal OK, low RX rate ( @ 1Mbps)...

Hi

Thanks for the input.

3 of our access points are omnis and we just installed 2 x 90 degree sectors.

We have switched 4 clients to the sectors and 3 report good links with max allowed transfer rates while the other was perfect at first and the complaint again that browsing was slow.

Fresnel may have something to do with it as we are in a bit of a funny position. Half way up a hill and the antennas are on the roof of a small commercial centre, so not particularly high, but then again they all used to work fine up to a few weeks ago.

We have tried all different channels with no difference and the links are all stable with good SNR......I am banging my head on the wall !!!!

Would anyone else agree or disagree on switching to G disabling the higher rates ?

Thanks

David

Hi David,

Im running almost 300 clients in G mode only all the client ar spreaded in diffrent towers ,but in the city we are using H-pol antennas only,this is for all the vertikal inteferens from home AP.
But i have seen similar problems like you have , but the i switched over to G mode 10 Mhz mode in 2.4 ghz then the problem was gone.

//Rickard

Hi Rickard

thenks for the info.

I was thinking of using H antennas but opted to stay with V.....maybe I should have gone for it.

I will try and switch one of our antennas to G only and re-configure the CPE's to match and see what happens.

Does anyone know if G will handle more packets per second than B ?

Thanks

David

Which radio card do you use?

I had similar problems last week at one of our site. I istalled this site on december 29. Clients near the tower 400m max was browsing fast in b mode. COnnection very stable; tested with bwtester. Ack timeout was ok for the distance 30, 100% CCQ and the rates were 11/11 mbps. The clients that were far from the tower could barely browse. Rates was 1/11mbps, ccq ~10 and the ack timeout was between 300 and 400. This client is at 1km from the tower.

I switched the ap in G mode. The two clients within 400m could barely browse, rates 6/54mbps, ccq between 5 and 15 and ack timeout of 408. The client that was far had astonishing results! Rates was 54/54mbps all the time, ccq of 100 and ack timeout of 56.

I know that is not "noise". It is in a rural environment, LOS for the 3 clients are perfect and depending of the rates, I was able to obtain great results, but not for everyone at the same time. I did try B/G but results were awful for everyone. I ran snooper and the band was almost clear. It is the "cleanest" of all my sites.

I switched the SR2 with a good old NL-2511 (prism 2.5 chipseet) and now everyone is happy. The ping time is great for everyone (3-5ms), everyone can max it's 3mbps queue, one even managed to make his ip phone works even if there were no QOS. At every other site I'm using atheros chipset (CM9 and SR2), but I did'nt have the time to test other radio. The prism lack a lot of great feature compared to the atheros, but it works...

Run a ping test to the CPE, if you see high latency or sporadic latency that is usually a good indication of interference.

Hi Biggs

we switched from cm9 cards to SR2 about a month ago all seemed ok to start with, but the antenna with the most problems still has a cm9.

We only have a few clients over 1 km the great majority are at about 600m range

I will do dome ping tests

Thanks

David

Run a ping test to the CPE, if you see high latency or sporadic latency that is usually a good indication of interference.

Having just fought a sizable layer 3 problem for 2 days that existed in an environment in which there were no layer 2 issues, as an alternative, I would suggest starting with the layer 2 information provided by MikroTik Router OS in order to know the basics about what's going on or what might be going on.

IOW, don't assume it is a layer 2 problem.

Layer 2 for a particular subscriber can be seen in Winbox with

wireless/registration/double click on desired association/click on statistics tab.

We would have saved a lot of time and provided better customer service had we not made the assumption it was a layer 2 problem.

best regards/ldv