Wireless Wierdness

Situation;
Wireless Router and several Range Extenders installed in a 30 room hotel.
All working on Channel 3.
Suddenly, Channel 3 disappears(?) and the router / repeaters cannot be seen.
Tried a couple of Wireless 'sniffer' programs with no luck at all.

Solution;
Moved every device to Channel 8 and all working again.

For testing purposes, I moved some units back to Channel 3 and they disappeared again.

Does anyone have any ideas as to what might be going on?

Sounds like interference on channel 3 from non-wifi devices (analogue transmitters possibly?) without a spectrum analyser it is very difficult to say.

Don't have a spectrum analyser but, it must be a very 'tight' monster signal before it kills one channel completely and doesn't affect any others. I can't even 'see' a device if I'm standing right next to it.

My suspicion is that it may be a microwave cooker, given the likely spread of WPAs in a 330-room hotel, although of course, they are not on continuously.

If it is such, possibilities are in-

Kitchen/s

Bar - for snack meals

Bedroom - possibly temporarily with a guest (I have seen small microwave cookers, about one-third of the usual volume.)

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Externally, remote monitoring equipment, possibly on a public utility.

Has anyone any idea of the frequencies used by (temporary) traffic lights for example?

I think that microwave cookers are out. It's a 30 room hotel, not 330 and, the problem started on Saturday and has been continuously present since.
It's as if a 'black hole' has appeared in the spectrum.

Have you got inSSIDer installed? It may show the signal there even if unusable. They also do a Spectrum Analyser - although not free.

You have only stated that you have tested channels 3 and 8.

Have you tested other channels?

Also I do not know that it is interference, that was a speculation based upon the information you gave and assumptions based on my own knowledge and experiences.

If you have further information on the channels that do, and do not work that would help narrow down the possibility's.

Also you say an access point and range extenders. Are they passive signal repeaters, wireless access points (with cabled connections to the network) or active wifi repeaters (eg WDS)?

Have you tested different channels for throughput?

Has anything changed recently (new building or road works in the area, new network devices, or software/firmware upgrades)?

Don't have inSSIDer installed but, I havea couple of others (NetStumbler etc.)

Will download a copy.

The only channel affected is Ch 3, all others are working.

Apart from the main router, all devices are active WiFi Repeaters (Not allowed to use wires athe the 'boss' "doesn't want to see any wires"

Throughput on every channel (except 3) seems to be 'normal' and, to the best of my knowledge, there has been no new building etc going on in the area.

There are, however, a number of other wireless networks in the vicinity and, all are 'visible'.

There is, as far as I can see, no other network using either ch3 or ch8 (which is why I chose them)

Completely baffled by the whole thing.

The latest version is no longer FREE but the older Version2 is perfectly good.

Be wary, Colin

I suspect that Netstumbler atc will be similar to inSSIDer in that the latter only responds to WiFi transmissions; but there may be other, non-WiFi transmissions on apparently "clear" Channels.

So those apparently clear Channels could in fact be the worst to attempt to use.

As has been said, only a Spectrum Analyser or similar would be able to provide the necessary information, if that is the case.

======================

Not too sure of the workings of WiFi Repeaters.

If they simply "receive and relay" the primary (router) source, could it be that those Channels have failed in that primary source; or that the swamping is close to it, preventing it using those Channels, so not being made available to to the repeaters?

I suspect an external(?) source.

This morning, I replaced the router with a new one and, in order to test it, switched all the repeaters off.

The new router would NOT work on ch3 but worked fine on a wide selection of others.

Brought the old router home with me and, guess what, it is fine on all channels.

Just have no idea as to what is going on.

FWIW, the hotel is situated very close to a harbour. Is it possible that there may be some ship borne interference that is causing the problem?

Edited by deleted (Thu 05-Jun-14 15:46:33)

Anything nearby using a Video sender? (remote cameras / security systems).
Wireless Alarms? (Car alarms use the 2.4GHz band, but some home/business wireless alarms also utilise the same band).
DECT phones don't but some foreign (US ??) wireless phones/baby monitors use the 2.4GHz band.

Wireless doorbell system? Wireless Dumb waiter ?

Ch 3 has a centre freq of 2.422GHz (2.411 to 2.433) which isn't specifically tied to any other types of equipment by design as far as I know.

Definitely in need of a spectrum analyser as most if not all the available software apps won't tell you about something that isn't meant to be there. (i.e. it won't pop up say Microwave), it will just say "nothing on Channel 3"

You don't have one of those wireless bluetooth headsets permanently on and every time you go to investigate the fault and get within 2 ft of the base station, it hops away to a different frequency...

It would drive me potty too not knowing... .

Chris

In reply to a post by colin020:

FWIW, the hotel is situated very close to a harbour. Is it possible that there may be some ship borne interference that is causing the problem?

Any way you can check if something new arrived in the harbour on Saturday and is still there?

Especially if it's sporting some odd-looking aerials, maybe.

In reply to a post by shinerweb:

(i.e. it won't pop up say Microwave)

Unless some evil-minded so-and-so has used that as their SSID� now there's a thought

Without a receiver or spectrum analyser, it is rather difficult.

One way would be to take the router around the hotel boundaries, noting any location where Channel 3 does work.

As Bill Ford has implied, it seems a fair likelihood that this would be away from the harbour

It would be a bit of a trauchle, particularly having power for the router - unless you have a 12v to 230 Volt Inverter and a car or such-like for the 12 V DC.

If you do try this route, let us know the results, either way. Could be interesting.

The Spectrum Analyser extension of inSSIDer would help; but at a cost.

If you know of any Radio Amateurs in your area, one may have a portable Spectrum Analyser.

In reply to a post by eckiedoo:

it seems a fair likelihood that this would be away from the harbour

One thing occurs to me- if it is a boat and it's not UK-registered it might not be subject to our wireless rules and could be using a fair bit of power� which could explain why the routers can see nothing at all on that frequency.

Routers can usually stand a certain amount of non-network interference before they give up completely.

In reply to a post by billford:

In reply to a post by eckiedoo:

it seems a fair likelihood that this would be away from the harbour

One thing occurs to me- if it is a boat and it's not UK-registered it might not be subject to our wireless rules and could be using a fair bit of power� which could explain why the routers can see nothing at all on that frequency.

Routers can usually stand a certain amount of non-network interference before they give up completely.

No, a boat/ship normally has to abide by UK rules when within territorial waters. Not easy to police but teh part of OFCOM that was teh Radio Communications Agency will come down hard on them.

In reply to a post by MHC:

Not easy to police but teh part of OFCOM that was teh Radio Communications Agency will come down hard on them.

But not until (and if) they catch 'em� still worth a check, I'd say.

It certainly is.

I used to deal with the RCA and had to call them out on a few occasions to look at interference. One of the Technicians that came lived in Lymington and said he would often run his detection equipment at home and during the summer would be paying a visit to a boat around twice a week.

In reply to a post by shinerweb:

Anything nearby using a Video sender? (remote cameras / security systems).
Wireless Alarms? (Car alarms use the 2.4GHz band, but some home/business wireless alarms also utilise the same band).

Wireless doorbell system? Wireless Dumb waiter ?

Chris

In all honesty, it could be any of the above but, I do not have access to other premises to find out and, I suspect that the 'wrong' approach might cause even more bother.

In reply to a post by billford:

In reply to a post by colin020:

FWIW, the hotel is situated very close to a harbour. Is it possible that there may be some ship borne interference that is causing the problem?

Any way you can check if something new arrived in the harbour on Saturday and is still there?

Especially if it's sporting some odd-looking aerials, maybe.

Entirely possible. It is a very busy harbour that has a lot of fishing vessels, oil related traffic, passenger ferries, cruise liners etc. passing through on a daily basis.

Nightmare to 'investigate' that lot.

In reply to a post by colin020:

Entirely possible. It is a very busy harbour that has a lot of fishing vessels, oil related traffic, passenger ferries, cruise liners etc. passing through on a daily basis.

Nightmare to 'investigate' that lot.

Sounds more like a port than a harbour, but I see your point

Strangely just had the same problem. I run a village wifi system which feeds 12 houses. This morning all houses lost connection so I thought no problem switch to the backup mast, still no joy. I was just about to get the ladders out so I could get on the roof to change the Engenius antenna unit when I remembered this thread. I changed the channel from 1 to 4 and everything started working.

The system has run quite happily for four years so why this should suddenly happen is a complete mystery. I am just glad I read these forums.

WiFi 2.4Ghz is shared with so many devices that easy enough for problems to arise, or get channel clashes from other wifi networks

That raises the possibility that your problem and Colin's problem may be caused by an adjacent hotel, group of houses etc, have set up a similar Community WiFi system., if they are on FIXED WiFi Channels.

Compare such situations with the typical domestic set-up, with Channel Hopping to avoid such clashes.

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Or I wonder if it is a domestic installation where the user has somehow locked on to a fixed channel?

agkq62

Sorry to hear of your problem but, glad that it's not just me...

Edited by deleted (Sun 08-Jun-14 10:42:43)

In reply to a post by eckiedoo:

Compare such situations with the typical domestic set-up, with Channel Hopping to avoid such clashes.

--------------------------------

Or I wonder if it is a domestic installation where the user has somehow locked on to a fixed channel?

Would channel hopping work with repeaters?

Also, if I cannot 'see' the interfering signal, would the router/repeaters be able to see it and jump channel?

Evening Colin

I don't know if the WAPs are capable of Channel Hopping; but logically, I suspect that they are semi-locked, requiring direct intervention by the person in charge, ie you, to specifically change each WAP.

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A hotel I stay at when down South "on business", with many more bedrooms than yours, is my main experience of such WiFi.

Last year when installed, it had three WAPs, all set to a single channel; and relatively poor coverage.

I suspect the poor coverage was because of likely widespread locations, over two distinct major blocks.

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This year, there are 10 WAPs, 9 being apparently of one type.

They were set to three different channels, 3, 7, 11 with the tenth being addituional on one of those.

I do not know if those Channel allocations were geographically grouped, 3,3,3,7,7,7,11,11,11,...; or if the ran along the lines of 3, 7, 11,3, 7, 11 ...

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Thinking about it and hopefully someone working on that type of installation may be able to answer the following.

I suspect, no matter how grouped, they are channel-fixed.

If you think of several guests using WiFi in a localised area, it could cause disruption if for some reason, that WAP jumped channel.

With several running, each with several guests using each one, there could be spectrum pandemonium.

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Thinking further, I must observe that installation in more detail; and also pay more attention when at airports etc. (Should be there imn about 2 weeks.)



Anyone with direct experience of installing and setting up such systems?

Edited by deleted (Sun 08-Jun-14 18:35:52)

Bad systems are as follows. They put a router into a room, they then put a wireless repeated in another room, another wireless repeater in another room etc. They do not link they up with a cable and use all the same channel on every device. This is bad. It means every device is on the same channel causing huge cross-talk but also wirelessly repeating the signal will half the available bandwidth and multiple repetitions will worsen this more.

A good system will be as follows. All APs will connect to a main AP with a cable.
There will be 1 AP on channel 1, another on 6 and another on 11. This avoids cross talk. Using channels such as 2,3,4 and 5 is generally a bad move. This is because by default users nearby will have routers on AUTO which will choose channels 1, 6 or 11. Channel 3 overlaps with channel 1 and 6 so using 3 you would get interference from both channel 1 and channel 6 routers nearby on AUTO. This is why big deployments use 1 6 and 11 generally only.

Better systems will dynamically change... For instance
Aruba networks which is used across most university campuses and probably airports will dynamically adjust the setup. So 1 router will be on channel 1, another on 6, another on 11. If the router on channel 1 begins to get interference it will dynamically change channels to say channel 11. If then both routers on channel 11 can see one another the output power of the routers may be reduced to avoid crosstalk and/or if this reduces the coverage too much the original router on channel 11, which may not experience interference on channel 1 may switch to that channel now. So it's dynamically changing.

These networks also run 5Ghz and 2.4Ghz on the same SSID. In a typical home this causes issues as the 2.4 Ghz will always be much stronger signal than the 5Ghz. In a good network setup the 2.4 Ghz signal will have limited power output and the 5Ghz signal will have a much higher power output. This means that the 5Ghz signal will appear around the same strength / perhaps just slightly stronger most of the time and encourage devices to hop onto this.

In an airport or somewhere busy there will be lots of routers all on 1, 6 and 11. They will all be outputting very little and covering a small area. If one does get interference there's always another one nearby but the setup should dynamically change things. There's generally multiple APs in a dense area just to handle the sheer volume of users.

Bit of a pain but the only real way to get a perfect wireless network is to use good deployment which is extremely expensive.

The best way to do it on the cheap is to fix a router on channel 1, another on channel 6, another on channel 11. Then the next on 1, then 6, then 11 etc... Keep them close together and keep the output power down on each router. If say channel 1 does end up blocked out people will still be in coverage of another AP on 6 or 11 hopefully. It's unlikely that channel 1 will always remain blocked out too. By using the entire spectrum you can mitigate some of the potential issues.

Using channel 3 by definition isn't a great idea as it's in the middle of commonly used 1 and 6. You'd be better just using 1 or the other.

Edited by ukhardy07 (Mon 09-Jun-14 00:38:37)

Thanks very much for that explanation and information.

I for one have certainly gained a lot from it, although I don't own or work in a hotel or other multi-WAP location.

The hotel I was describing is one of a very well known small chain; another of which I stay at occasionally is very well known, appearing frequently on TV Sports.

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Regarding the power levels of the two bands, it is only with my recent upgrade to FTTC, 40/10, that I have had access to it, here at home - never used it otherwise.

With that FTTC upgrade, I took 8 inSSIDer measurements in the jouse and another two in the garden, using the original Bright Box 1 (2.4 only), the new Bright Box 2 (2.4 & 5), and running CONNECTIFY on my main HP Pavilion.

The averaged, rounded results were-

-52 db ~ BB1 2.4

-51 db ~ BB2, 2.4
-61 db ~ BB2, 5

-64 db ~ Tower CONNECTIFY, 2.4

At some time, I must try to get the range of the two Bands, particularly on the BB2.

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Again my thanks, i trust that others appreciate the range of information you have given.

Edited by deleted (Mon 09-Jun-14 07:15:40)

At last I have carried out a range test, comparing the two WiFi Bands, from the BB2 only.

Unfortunately, this can only be readily done in one direction, out to the front.

The 5 GHZ Signal "disappeared" at about 20 Metres Range, -97db, through two concrete walls from the router.

The 2.4 GHz Signal was also still present, at the same distance, -80 db; and through the same two concrete walls.

I would have to go out on to a road etc to get the eventual disappearing point for the 2.4 GHz Band.

Edited by deleted (Fri 22-Aug-14 12:38:42)

The 5 GHZ Signal "disappeared" at about 20 Metres Range, -97db, through two concrete walls from the router.

In reality the signal disappeared a lot sooner. At -97db it wouldn't have been usable anyway, if you tried to connect it would have failed no doubt. Even at -85db it's generally unusable / a lot lot slower.

Agreed

But balancing the laptop on one hand trying to observe the inSSIDer display in sunlight and wind, was difficult enough, so the "disappearing" distance was the more easily observed.

At least now I have a more clearly defined comparison between the two bands, for my circumstances.