Long Distance AP

[bairdc]

Wow! You guys have no idea how pleased I am with StarOS. I just brought up a 23 mile link and was able to transfer a 1.2 meg file over it at 3.5 Mbps! :D Just for reference I tried this same link a year ago with a pair of Cisco BR340s, and got 2.3 Mbps.

So Lonnie and Tony, how does it feel to know that you've made StarOS outperform Cisco stuff by about 1/3? :twisted:

Craig

[lonnie]

It feels GOOD. The best part is we needed it ourselves and it does such a nice job for us.

[tony]

I am glad to see you are happy! The distance support is nice indeed.

Out of total curiosity, have you tried this shot with regular 802.11b gear. If so, what throughput did you see with it?

Thanks!

[bairdc]

I am glad to see you are happy! The distance support is nice indeed.

Out of total curiosity, have you tried this shot with regular 802.11b gear. If so, what throughput did you see with it?

Thanks!

Yup. Before I tried the Ciscos I tried it with Orinoco cards in Linux Boxes using Ad-Hoc demo mode. The radios were auto-negotiating to 1 meg, but the actual throughput was around 256k, in spite of excellent signal. I was able to squeeze about 768k throughput out of them by turning off the auto rate negotiation, and locking them to 11 meg. That was still not satisfactory, though...

The interesting thing is that the Ciscos have a distance setting in them as well to adjust the timing issues. Obviously, though they don't do as good a job as StarOS does.

Craig

[TheBarron]

For you folks that post about the shots you make.. especially the long-distance ones, please include details! :)

What cards on each end? Amps? Antennas? How good is the LOS? etc...

[Bossman]

It would be nice to see a chart with various long distance configurations... the good ones (with Star OS) and the others. If this is not something that can be an "official" part of the star OS site, I'd be happpy to try and make the time to maintain it and provide it to the Star-OS group.

[bairdc]

For you folks that post about the shots you make.. especially the long-distance ones, please include details! :)

What cards on each end? Amps? Antennas? How good is the LOS? etc...

Link Distance: 23 miles, clear LOS
Elevation point 1: 5400 ft.
Elevation point 2: 7700 ft.
Radios: YDI short cards (OEM Agere w/o built-in antenna)
Antennas: YDI 24 dB grids
Amps: YDI 250 mw (both sides)

Signal: -47
Noise: -87
Quality: 40

Throughput: 3.5 Mbps

Hope this helps!

Craig

[tony]

We finally got our new link up and running.

54 mile link, clear LOS

Main Access Point (Feeding both 32 and 54 mile links)
AMP: Teletronics 500mW
Antenna: 24 dB gid
CPE: TT CPE w/StarOS 1.10.1 set to 54 miles
Radio: Stock Avaya
54-mile signal(q/s/n): 25 / -59 / -84

Client side (in town 54 miles away)
AMP: RF Linx (TX G=12dB, RX G=20dB), Antennafier 2400 (C Series)
Antenna: 24 dB grid
CPE: TT CPE w/StarOS 1.10.1 set to 54 miles
Radio: Avaya w/ soldered pigtail and removal internal antenna
Signal(q/s/n): 30 / -49 / -79

Throughput from client location:
Peak: 300 KBytes/sec, average: 240 KBytes/sec.

Average latency:
default 84-byte packet: 4.400ms
1500-byte packet: 11.173ms
49180-byte packet: 220.742ms

------ UPDATE (13:19 Nov 29 2002) ------
Changing the RTS Threshold to 370 increased our throughput to a consistant 330 - 350KBytes/sec

------ UPDATE (8:48 Dec 2 2002) ------
Access Point AMP is not a YDI, but rather a Teletronics 500mW

[bobbyc]

Baird, have you tried that 23 mile link without the amps? Just the 24dB antennas and OEM cards at both ends? Or is that impossible because of cable loss/antenna height?
Bob C

[bobbyc]

Tony,
Why do you think the noise floor (-79) is so high on the PTP client side? With such a directional antenna, you'd think it wouldn't be so high.
Do you blame RF linx?
Bob C

[tony]

The noise is caused by local interference from another local provider, though our SNR is more than adiquate enough to sustain a solid link.

The RF Link AMP works as advertised, and does a darn good job of it.

Thanks!

[bobbyc]

Thanks Tony, that is a very nice SNR indeed. The amp assumption came up merely because I've heard that YDI are the best for more signal and less noise amplification and I saw the discrepencies in your noise figures with different amps.
I was looking at the RFlinx website, some of their stuff looks real interesting... especially their new amp, the one that amplifies only certain channels. Kind of like a bandpass filter(?)
Bob C

[lonnie]

In this business the very idea of accurate signal reading is wishful thinking. The signal meters have never been calibrated so who is to say that -79 dB is worse than -87 dB? It just could be the way they both represent no noise.

Or since these sites are completely separate - 52 miles apart - the difference could be the local situation at each system.

The only number that makes any sense is the Signal to Noise ratio. These units have from 25 to 30 dB and that is awesome, thus we have a quite acceptable throughput.

The RFLinx selective amp is a dream come true for quite a few people. I have heard of guys using them in areas that have almost unusable signals before the tuned amp. They are quite expensive, but if they work I would say they are worth every penny.

[bairdc]

Just curious... What was the RTS Threshold set at initially, before you changed it to 370? Was it disabled?

Craig

[tony]

It was disabled (the default)

[bairdc]

That seems strange to me. On a PTP link, why would setting RTS make a difference? Since it's PTP, there is no hidden node problem, because both sides of the link (presumably) can see each other, right? It just seems counter-intuitive to me to set RTS on a PTP link. If this really works, though, I'll go back and set RTS on all my PTP links! Right now, I've got it disabled because I didn't think it would be useful on a PTP link...

Craig

[tony]

That seems strange to me. On a PTP link, why would setting RTS make a difference? Since it's PTP, there is no hidden node problem, because both sides of the link (presumably) can see each other, right? It just seems counter-intuitive to me to set RTS on a PTP link. If this really works, though, I'll go back and set RTS on all my PTP links! Right now, I've got it disabled because I didn't think it would be useful on a PTP link...

Craig

This is a PtMP link, with repeaters located at 6, 13, 32 and 54 miles. :)

Thanks!

[bairdc]

Ah, okay. That makes more sense. One question though. In the post on the equipment you use, you said it was a 24 dB dish. Are you serving all four of those repeaters off that dish? How did you get the horizontal beamwidth wide enough? Or is it actually a sector/omni?

Craig

[TheBarron]

To repeat bobby's question, as I didn't see it answered..

bairdc: Did you attempt that link without the amps?

[bairdc]

Sorry about that, I didn't see bobby's post.

Anyway, no I didn't try it without amps. Although I'd be interested to see how it would work without them. Basically, one end of this is on a very high mountain top, and we were pushing to get the link in before the snow fell. So I put the amps on it to be "on the safe side" as far as fade margin goes. I don't want to have to visit this tower in the middle of winter with 5 feet of snow if I don't have to. :D Come spring or summer, I'm thinking I'll pull the amps off and see how it acts. If it seems to be stable, I've got other places I could use the amps.

Craig

[bobbyc]

Just curious... we had a 13 mile link running cisco 350 pci cards/freeBSD at each end at 100mw each end. Later we dropped that to 30mw and saw no ill effect. 24dB grids on each end, one end has 20' lmr-400 and the other end 130' lmr-600. Now we have star-OS and a 30mw agere OEM card on the 130' end and it is still running fine talking to the cisco card... Soon we'll have Star-OS and 30mw agere on the other end as well.
I don't have any SNR figures yet, I will once the other end is a Star-OS/agere card.
If the SNR turns out being sorta low, I would like to get some inexpensive solid dishes and see if they perform better. Before we installed the hardware on each end, we did a test with laptops and orinocos. I don't remember exactly, but I think the SNR was mid/high 20's.
Bob C

[lonnie]

Are you serving all four of those repeaters off that dish? How did you get the horizontal beamwidth wide enough?
Craig

We are in a long valley and as "luck" would have, our main repeater is at one end the other repeaters are at various distances in a striaght line down the valley. Each unit simply has a 24 dB grid antenna. It doesn't get any better than that. Not sure if you know, but you can hit the back end of an ampled 24 dB grid from about 3 miles away.

[georgew]

The first time I deployed a wireless network, I started with two 24db dishes. I strapped one to a 4' fence post, aimed in the general direction of the other end of the shot. I then got in the truck and drove to a hill about 2.5 miles away, and using the other 24db dish, I got full signal strength no matter where I aimed the dish. that was with the old wavelan 802.11 stuff, no amps.



George

[bobbyc]

Tony/Lonnie, do you use RTS on your other APs with all your customers? If so, is it 350 as well?
Bob C

[lonnie]

So far we have not used RTS. I tried it on one unit today but it made no difference. Our client units are mostly the old 2 mbps cards and they do not automatically follow the AP (just Lucent cards), so we would have to have each user set their RTS - a royal pain, and we are not sure we need it so we leave it alone.

[bairdc]

Our client units are mostly the old 2 mbps cards and they do not automatically follow the AP (just Lucent cards), so we would have to have each user set their RTS - a royal pain, and we are not sure we need it so we leave it alone.

Here's an interesting thing relating to RTS/CTS. I recently picked up a Linksys WET11 for testing to see how they might work for CPE devices. In the setup for the unit, there is no RTS/CTS setting. However, in the users manual, it states that it supports RTS/CTS. So, I fired off an e-mail to Linksys tech support asking how their RTS/CTS works. They replied that the WET11 adjusts to whatever the RTS setting is on the AP, therefore there is no need to set it in the unit. This sounds like the same thing the Orinoco cards do... I e-mailed them back asking if it would only work if the WET11 is used with a Linksys AP. They said that it should work with any manufacturer's AP. Previously, I was under the impression that only Orinoco stuff did this. Apparently that's not the case.

Does anyone know if this feature where the AP hands out RTS/CTS to the client is becoming a standard thing? Is this perhaps a requirement for "wifi" certification?

Craig