Understanding Cloaking

[Ick]

I have a very very basic understanding of what cloaking is. The way I understand it, you can run 11 AP's side by side without interference.

Could someone please give me a much more detailed explanation on what it does exactly and what the pros and cons are? I.e., is the SSID still broadcast, etc? How is it different from the "legacy" wireless channels?

I have a busy site that I need to replace a WRAP omni with a WAR4 sector, sounds like cloaking would be what I need to make the conversion with minimal interference.

[lonnie]

I have explained it a few times now. It is a modified modulation method that uses 5 MHz and 10 MHz bandwidth. In all other respects it is identical to standard and Turbo.

[go.fast]

The first thing that has to be understood is that both the AP and the CPE need to be able to "be cloaked". It doesn't work with one side only.
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The second thing that has to be understood and is probably misunderstood by many is what channels or frequency range is used in typical 802.11b

A "typical" AP set up is using Channel *1*, Channel *6* and Channel *11* as "Center Channels" for a total of 3 AP's that are not overlapping.

Each sector actually uses 5 channels each.
Channel 1 is Channels *1* ,2, 3 and the 2 before channel 1.
Channel 6 is Channels 4, 5, *6*, 7, and 8
Channel 11 is Channel 9, 10, *11*, 12, 13


So each typical sector Ap using typical Channels 1, 6, and 11 are actually using "5" channels each, including 4 channels most aren't aware of, or rather frequency they don't see listed in their selection of channels. In each set of 5 channels the two outside channels are not full channels, but rather half channels with less power creating a buffer of unused frequency between the three typical AP sectors. Thus you have about 22MHz of space for each typical AP channels.

Star-OS V3 has 2 options for cloaking, using 1/4 the typical frequency range or 1/2 the typical frequency range.

Reducing the channel size from 22MHz to 5MHz (1/4) or 10MHz (1/2) wide is called cloaking.

With 1/4 th the typical frequency range channel size, you have 11 individual seperate channels and 1/2 gives you 6 seperate individual channels. Rather than the "typical" 3 channel layout of 802.11B

This is the best I can do off the top of my head.

Maybe Lonnie or Tony can give us more details.

George



I have a very very basic understanding of what cloaking is. The way I understand it, you can run 11 AP's side by side without interference.

Could someone please give me a much more detailed explanation on what it does exactly and what the pros and cons are? I.e., is the SSID still broadcast, etc? How is it different from the "legacy" wireless channels?

I have a busy site that I need to replace a WRAP omni with a WAR4 sector, sounds like cloaking would be what I need to make the conversion with minimal interference.

[tony]

Thank you george, your explanation is correct.

In addition to the 1/2 and 1/4 bandwidth used with each channel, there is also a 1/2 and 1/4 total throughput drop with each mode (as would be expected). A 1/4 (cloaking 4x) mode in 802.11g can produce speeds > 5Mbps (more than a typical 802.11b network), except that you now have 11 (or 13 depending on country) non-overlapping channels, instead of the standard 3.

This mode has the same effect with 802.11a.

With Cloaking, instead of the card's tx power being spread over the normal 20Mhz channel, it is focused on the 5, or 10Mhz band, and thus produces higher signal levels, which is great for those long-range links.

The cloaking modes also have a higher tolerance to interference, which is good for those RF congested areas.

[go.fast]

Tony, how many MHz of unused space is there in between 1 cloaked channel and another as a buffer?

And as I understand it the 22MHHz typical 802.11b channel with has more power out the center than on the edges, creating a parabolic shape concerning power across the 22MHz width.
Are you saying that with cloaking it is the same power all the way across the 5 or 10MHz space used?

[tony]

802.11b and g uses a 20Mhz channel. As for power usage, Lonnie may be able to explain it better than myself.

[lonnie]

There is no unused space. The channels are 5 MHz wide and thus are 2.5 MHz from each side of center frequency. The normal shaping of the RF output attenuates the outer frequencies down to minimize near channel interference. My spectrum analyzer shows a very sharp shoulder (unable to put numbers to it because it is not calibrated, thus cannot be used for specs) and the actual, real world testing indicates side by side works well. Of course we have 11 channels to play with so we always give some separation so that antennas beside each other have more than 1 channel separating them.

Tony, how many MHz of unused space is there in between 1 cloaked channel and another as a buffer?

And as I understand it the 22MHHz typical 802.11b channel with has more power out the center than on the edges, creating a parabolic shape concerning power across the 22MHz width.
Are you saying that with cloaking it is the same power all the way across the 5 or 10MHz space used?

[Ick]

Thanks for all of the great info. I did not realize that the client had to be able to cloak as well, but it makes sense that it would. I'm glad I know this now, while in design mode.

[luka]

Another question: could it be possible to have different channel sizes.. ie 3 mhz or 7 mhz or so...?

[tony]

In theory, but it's not something we are planning on supporting.

[greg]

I had some lag on a 4x cloaked 3 mile 5.x connection today that has been pretty solid. I enabled the cloaking feature late last week. Today, ping times were in the hundreds and I logged into the remote client. Even getting in was sluggish. I looked at traffic for p2p but didn't notice any. I rebooted both sides but it came back up with ping times averaging >200ms. I removed the cloaking and ping times are back to averaging 5ms. Same channel, etc but seems to be running better this way.

It is raining here this morning which doesn't happen often and shouldn't be a factor?

[tony]

If the ping times are > 200ms, I would suspect your link was over capacity for 4x cloaking?

[Beebe]

Maybe your ping times are higher because when you didn't change the distance setting and your ack timing is wrong? When you move to 2x cloaking you should put in double the actual distance, and when you use 4x it should be 4x the distance.

This one had me stumped for a while today until I remembered seeing a post about it some time back.

Thanks,
Roger

[greg]

Hmmmmm. No, I didn't know that and I didn't change the distance. I thought you might be on to something but.....

Here's a flaw in that: I have one link cloaked that is 16 miles. The distance is set to 18 and has been that way for over a month without any issues at all. It's on channel 5220.

[Beebe]

Ahh, maybe I am mistaken. Reading that post from way back when again, maybe that's not what it was saying...

Using either 2x or 4x modes will also hide your AP from all other systems, and will not show up in any scan lists, etc. The distance will also be 2x and 4x that of standard modes, respectively. We will be updating the interface to support entering the distance in km and miles in the near future. Clock tick value of 8192 is the maximum distance allowed, provided by the mode and cloaking option selected.

Quote from http://forums.staros.com/showpost.php?p=25521&postcount=5

The link I was setting up was an SR9 link, so maybe the ack timing somehow works different since the signal is going through an up/down converter - maybe that was the issue I faced. Anyway when I set it to the actual distance I was getting really high ping times and poor inconsistent throughput. When I raised the distance settings it improved.

Tony, can you confirm that the same distance settings should be used whether cloaked or not cloaked? I didn't even try the link uncloaked because I wanted so much to have 4 non-overlapping 900mhz channels :) And it works great!

Thanks,
Roger

[lonnie]

Distance settings should be the same as 2.4 and 5 GHz. The one thing that kills a link for cloaking is the speed sometimes drops to 1 mbps which is very little throughput. We set a fixed rate for the client tx based on their signal. It pretty much stabilizes it and the link works great. The lag is caused by an aggressive software retry scheme that tried real hard to buffer data and keep trying to get it to go through.

[greg]

Is there a disadvantage to cloaking a 5.x signal used for backbone purposes? I've been experimenting all morning with different settings and I get my best thoughput at 1x. There appears to be a dramatic reduction between each setting. I'm testing using Utilistar's Thruput utility.

[go.fast]

There is a big diference as you have noticed. Math is pretty easy. 1x which is full 20MHz channel width is 100%, 2x which is 10MHz which is half the channel width is 50% and lastly 4x which is 25% channel width is ...25%

You might get better numbers than this, but it's a good rule of thumb.

Hope this is helpful

George

[tony]

George is correct. Cloaking will reduce the bandwidth used for the channel, but as a side effect, it will also reduce your max throughput potential by the same factor.

[David L. Vrablic]

So let me try this with a practical application and see if I got it.
I have a Mesh camera system I am bringing on line this week.
("The good lord willing and I don't break a leg")
If I have a problem out on the edge getting to some place and decide to do a point to point from the 4th radio in the box to a remote camera..
I can set that link (on both ends) to cloak at whatever x factor I need to get through some noise or "Lack of path???"
At that point hang the throughput and just be happy that I have a connection at all!?
---------------
Hows that for a real worldl example?

OOps! I forgot to say this is a 5 ghz system.
The examples for 2.4 are great but is there anything we need to watch out for in 5 Ghz band ?

Not to stray to far from the thread but I'll ask these two questions.
1. Is there any problem using cloaking on the lower indoor channels with the power turned down where it is supposed to be?
2. I have read so many things that contradict each other as regards to usage of the indoor freqs outside.
With camera systems the public spaces like malls, covered walkways, arcades and arenas sometimes the meaning of outside gets blurry.
Any comments?

[ninedd]

You can think of it as an 'anti-turbo' in some ways. :) Using 2.4 for example, normal transmissions are 20 Mhz wide, provide X throughput, and require nobody noisy on the selected channel, plus two on each side of it. Turbo, is 40Mhx wide, provides about 2X the throughput (in theory) and requires pretty much the whole 2.4Ghxz band.

2x cloaking, are only 10Mhz wide, only have 1/2X throughput, but you can use twice as many channels. 4x is only 5Mhz wide, you can use every single one of the 11 channels without self interfering, and if there already are people on 1, 6 and 11, you can select channel 4 or 9 and sometimed sneak between their noise.

Everything is a tradeoff though - going from 5 to 10 to 20 to 40Mhz channels will increase throughput, but will increase the consumption and need for clear channels.

[cephlon]

I use an atheros PCI card for surveys. If I have an AP with cloaking, will the card pick up the AP or do I need to use a WAR board w/ cloaking enabled?

[lonnie]

Youn will not see it with the laptop, which is why we coined the term cloaking.

[cephlon]

I have been playing with cloaking all day today with a 6 mile link. The signal -77 and qual 100-80. This is a CM9 to an SR2.

It seems that 2x cloaking works great. But when I switch the 4x cloaking my bandwidth is cut in half. With 2x I see about 1500 kps down. With 4x I see around 600 kps. I know that cloaking cuts down on the available bandwidth, but I assumed that was only if the link was > 5 mb.

Should I be seeing this type of bandwidth decrease? Perhaps this link is not suitable for 4x?

If I set the channel to 3 and have 2x cloaking, what are the 2 channels that are being used? 2&3 or 3&4?

[lonnie]

Cloaking cuts down on RF bandwidth and as a result it reduces the throuhgput. The X4 cloaking will still get more than a prism or orinoco card and it you can use compression it will get up to 10 mbps or almost double what you see with older 11B cards.

If you use X1 on channel 6 or 2437 MHz. This has 20 MHz RF bandwidth so the RF is 10 MHz on either side 2437, so it interferes with channels between 2427 and 2447.

If you use X2 on channel 6 or 2437 MHz. This has 10 MHz RF bandwidth so the RF is 5 MHz on either side 2437, so it interferes with channels between 2432 and 2442.

If you use X4 on channel 6 or 2437 MHz. This has 5 MHz bandwidth so the RF is 2.5 MHz on either side 2437, so it does not interfere with any channels because channels are 5 MHz apart. Of course this means it does not interfere with another X4 cloaked system but will still be seen as trouble for X2 or X1 systems, since they have the wider bandwidth.

There is no magic, just RF rules involved. You have to balance out the requirement for bandwidth and the desire for more channels and less interference.

[cephlon]

Thanks for the help. So using 2x cloaking really only gives me 4 non-overlapping channels in 2.4 ghz, instead of 3. Where as 4x will give me 11 channels.

2x cloaking:
Channel 1 = uses 1,2
Channel 4 = uses 3,4,5
Channel 7 = uses 6,7,8
Channel 10 = uses 9,10,11

Does anyone know or experienced that the CM9 or Compex cards can handle 4x cloaking better then an SR2?

[ninedd]

Does anyone know or experienced that the CM9 or Compex cards can handle 4x cloaking better then an SR2?Well, the CM9 is WAY faster than an SR2, so while the RF rules that Lonnie was explaining above will be the same, the throughput of an CM9 to CM9 link will be quite a bit faster than an SR2 to SR2 link.

For Compex, you'd have to buy the correct card, since they make both a high performance and a low performance card. The ones that Valemount sell as the High Performance cards with Compression and Fast Frames, so again - yes, a High Performance Compex-Compex link will outperform a SR2-SR2 link.

[lonnie]

2X cloaking requires 1 channel between, so your list is:
Channel 1 = uses 1,2
Channel 3 = uses 2,3,4
Channel 5 = uses 4,5,6
Channel 7 = uses 6,7,8
Channel 9 = uses 8,9,10
Channel 11 = uses 10,11

On 4X cloaking the non overlapping channels are:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11


Thanks for the help. So using 2x cloaking really only gives me 4 non-overlapping channels in 2.4 ghz, instead of 3. Where as 4x will give me 11 channels.

2x cloaking:
Channel 1 = uses 1,2
Channel 4 = uses 3,4,5
Channel 7 = uses 6,7,8
Channel 10 = uses 9,10,11

Does anyone know or experienced that the CM9 or Compex cards can handle 4x cloaking better then an SR2?

[cephlon]

Well, the CM9 is WAY faster than an SR2, so while the RF rules that Lonnie was explaining above will be the same, the throughput of an SR9 to SR9 link will be quite a bit faster than an SR2 to SR2 linke.

I assume you meant CM9 - CM9, not SR9?

[ninedd]

Yea.. CM9 is what I meant. I corrected the original post above just now. Typed it in a hurry I did... :)