AP infrastructure using PS2 - ext

[Otto]

Hello,

I am looking to use the PS2-ext as our access point platform. How many concurrent cpe's would a sing PS2-ext be able to support when it is in AP mode.

We will be throttling the bandwidth to 256kbps for most cpe's. Some business users will be on 512kbps.

I know there are probably better solutions out there on the AP side but we are in a small town in a developing country and we like the simplicity of AirOS and standardising our AP''s and CPE's to one supplier. This will allow us to keep less stock and our techs will require less training. (we order our gear from the US and it often takes 3 weeks to get here via FedEX!)

At this point I am thinking of deploying a cluster of 3 PS2-ext connected to 15dbi 3 x 120 deg VPOL sector antenna. How many CPE's could this realistically support if they are throttled to 256kbps?

Best Regards

Otto Melzig

[WHT]

The general consensus is the UBNT line will start chocking past 30 to 35 active connected clients....the bandwidth isn't really the limiting factor, its the processing overhead.

[Otto]

I have read this on another thread regarding the Nanostation. Does it apply to the Powerstation as well? I was under the impression that they had a different processor.

I am also a bit confused what would constitute an active session. A CPE that is switched on? Or a subscriber that is actually transmitting or receiving?

A lot of our users will be using a webmail service that we will host at our NOC. They may be composing an email for a few minutes during which time they will not be transmitting or receiving.

[Otto]

What else could we use that is a little bit more scalable but still easy to deploy?

[rconaway]

Have you considered putting up NS5's also? We are doing that for an installation where the tower will be handling about 150 users. 3 NS2's and 3 NS5's. Another idea would be Routerstation with the appropriate cards.

In our experience, the packet collisions based on overhead are the limiting factor in 2.4GHz. I have AP's with 47 users on them who barely send 3 emails a day and their average speed is 2.6Mbps down. Other times I get AP's with 12 users but somebody is doing video conferencing or streaming and then here come the phone calls to tech support that the system is slow (that gets fixed tomorrow when I throw 20 nanos and PS5's at the situation).

Once utilization starts going up, it starts causing more packet collisions. The system starts slowing down llogarithmically and then performance suffers. That's when you want polling. If you have light email users, 35 is probably not a problem at 256K. You could probably handle more. If you have heavy users downloading movies all day, 5-10 users will take you down. That's when you start capping monthly maximums on MB usage. Those customers will really love you.

However, this assumes that your Internet bandwidth exceeds your radio capacity. If you don't have 30Mbps on your internet access, this is a moot discussion. For the record, I'm feeding my tower of 6 live AP's with three 5Mbps/1Mbps DSL lines into a Peplink 300. The radios are far faster than my egress point so it doesn't really matter.

[Otto]

We are doing this in a town where the only other alternatives are:

- average of 30kbps dial up at $100 a month plus $1.5 an hour (if you are lucky enought to have a landline)
- VSAT with an upfront investment of $10,000 and $1000 a month

We will be hosting a lot of stuff locally, web mail, local forums, a digital library. Other web sites will be cached. Our bandwidth to the internet will be highly contended.

We want to make the service a little cheaper than dial - up but access to the internet will not be broadband - we will be throttling each session to 64kbps on the proxy server. Access to local resources should be at 256kbps to 512kbps.

I am not sure if 5.8Ghz is legal where we are. From what I have read so far the best solution will be to add access points at diverse geographical locations with a backhaul to our NOC.

We might start with a 3 x 120 deg vpol sector at the NOC using 3 ps2-ext - hopefully this will scale to around 100 CPE's. Then we will add NS2 AP with a NS5 backhaul to areas that have a high concentration of users.

How does that strategy sound?

Thanks for all your help!

[rconaway]

I understand. I think I would look at a slightly different solution then. The key point is that if you don't know if 5.8GHz is legal (and assuming that all 5GHz frequencies are illegal), then you can't use an NS5 for backhaul later. Also, do you know if you have 14 2.4GHz channels or 11?

[Otto]

Our regulator, Pangtel is still working on regulations governing the use of the 2.4Ghz ISM spectrum. No regulations or guidelines have been released at this point in time.

So I assume we can use all 14 channels and while there are no restrictions on power we obviously have to use common sense, especially around urban areas.

[rconaway]

Then this is my suggestion. I would use channels 1,6,11 for your 3 antennas, all on vertical polarity. I would use Bullet2 HP's if you could wait, NS2's if you can't. Assuming you can't use 5.8GHz, then Channel 14 becomes your backhaul. I would use 2 radios for backhaul on 14, one on horizontal polarity, the other on vertical. You need to isolate them from a signal standpoint putting them on either side of a building, or building some structure between them.

If you have other licensed or unlicensed frequencies, then you have more options.

[Otto]

I have just had a chat with Joe who works for our regulator, PANGTEL and he has kindly sent me a draft of the proposed regulations:

2.4Ghz appoved by the board today

5.8Ghz has been recommended but not yet approved

900Mhz is already widely in use but is NOT approved and interferes with our mobile phones

maximum power 1 watt with 6dbi directional gain antenna. If antenna prvides more gain then the transmit power has to be reduced by the same amount. So for Bullet2 HP with a 24dbi grid we would need to reduce the transmit power by 18dbm?

[Otto]

I should add that in PNG we are quite negotiable on rules. So if the regulator says that 5.8Ghz has been proposed for approval then I think we would get the nod to start using it now.

It would be just a matter of catching up with the regulator for a cup of coffee and letting them know what we are up to. So we can use NS5 / Bullet5 for backhaul!

[WHT]

If Papua New Guinea if just starting to from their telecom and radio licensing formats, I'd suggest they take a look at the U.S. FCC's Part 15 rules and regs.

[rconaway]

"maximum power 1 watt with 6dbi directional gain antenna. If antenna prvides more gain then the transmit power has to be reduced by the same amount. So for Bullet2 HP with a 24dbi grid we would need to reduce the transmit power by 18dbm?[/quote]

Otto, you are jumping around here. You originally stated 3 sector antennas. The PS2 is fine for that running 22dBm. The Bullet 2HP however, reduces loss in the cable for the recieve side. Set it to 22dBm and figuring connector loss, it's about right.

As for the clients, just use PS2's and set the power to the appropriate level.

[Otto]

Everything except ISM has been very tightly regulated for many years. 2.4Ghz has mushroomed in the capital Port Moresby because our monopoly phone company, Telikom has dragged it's heels. It has taken them over 5 years to deploy ADSL. So the ISP's have just gone ahead and deployed 2.4Ghz everywhere.

Now the ISP's in Port Moresby have a significant investment in wireless infrastructure and they have a vested interest that the regulations are not too tight. PANGTEL our regulator have also promised not to take any enforcement action in the ISM band but rather engage in consultations with all stakeholders.

But we are in a provincial town and no one has deployed anything apart from indoor access points at the office. All our 2.4Ghz channels are free - a site survey using a NS2 with an omni antenna shows nothing!

[rconaway]

You have my suggestions, good luck. I will post a picture of our multi-radio tower after we install it tomorrow.

[Otto]

Thanks.

We will use the 3 x 120deg VPOL sector with 3 ps2-ext, since the Bullet HP is not yet available.

For additional access point we will use NS2 and NS5 for the backhaul.

The Bullet2 HP with a 24dbi grid was just an example I was using to try to calculate the maximum power we are allowed to use. In any case the BulletHP is not available and I think the 400mw PS2-ext is enough power anyway.

[rconaway]

I understand. Good luck.

[nithra]

Hi

Thanks for sharing!!

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