[HOW TO] Diagnose Wireless Issues

mickevh

Distinguished Member
The short answer is, there's not much you can do. The Wi-Fi airwaves don't "belong" to anyone and anyone can use them any way they want to as long as they don't exceed the mandated maximum transmit power. (Legend has it that in the US, an apartment building owner tried to mediate the channel plan for his residents, but got sued by some ambulance chasing lawyer who asserted that the landlord could not do so because the airwaves didn't "belong" to him.)

All you can do is try to find a channel that has the biggest signal margin (difference between your Wi-Fi and any others using the same channel.) There are more channels available in the 5GHz waveband (and the transmit power falls off faster,) so there's a better chance of finding a less polluted or even clear channel for you 5GHz kit (and better chance of finding the "fat" channels N & AC need for their faster speeds.) However, not all kit is 5GHz capable.

SSID's are not "channels" as such, they are just a named "set" of devices (and happen to be using a particular radio channel.) It's not at all unusual for Wi-Fi AP's to offer multiple SSID's - almost all enterprise kit does it and as you've observed increasingly SOHO gear is doing it to avail "main" and "guest" networks and ISP's are trying to build their own large scale "public hotspot" services by using all their subscribers to offer an "public hotspot" SSID. But each SSID isn't tuned to a separate radio channel, they can all use the same one and hence you can observe their RSSI as the same or similar.

Then, in big installations, we would deploy multiple AP's (sometimes hundreds on big sites) and advertise the same SSID's out of all of them - we don't use different SSID's for each AP. So again it's not unusual to see the same SSID out of different AP's on different channels. If you were to visit some of the big deployments I've done, you'd find most of the campus had locations where you could find my SSID's on all channels because you'd be very likely to be "in range" of multiple AP's all tuned differently (say 1,6,11.) Sounds like you are seeing something like that with your "joes" SSID's - probably 2 AP's tuned to different channels advertising the same SSID(s.)

I'm not surprised the FCC and ISP haven't intervened, as nothing your have described is "wrong" - Wi-Fi is "just like that" I am afraid.
 
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avsnoob

Novice Member
The short answer is, there's not much you can do. The Wi-Fi airwaves don't "belong" to anyone and anyone can use them any way they want to as long as they don't exceed the mandated maximum transmit power. (Legend has it that in the US, an apartment building owner tried to mediate the channel plan for his residents, but got sued by some ambulance chasing lawyer who asserted that the landlord could not do so because the airwaves didn't "belong" to him.)

All you can do is try to find a channel that has the biggest signal margin (difference between your Wi-Fi and any others using the same channel.) There are more channels available in the 5GHz waveband (and the transmit power falls off faster,) so there's a better chance of finding a less polluted or even clear channel for you 5GHz kit (and better chance of finding the "fat" channels N & AC need for their faster speeds.) However, not all kit is 5GHz capable.

SSID's are not "channels" as such, they are just a named "set" of devices (and happen to be using a particular radio channel.) It's not at all unusual for Wi-Fi AP's to offer multiple SSID's - almost all enterprise kit does it and as you've observed increasingly SOHO gear is doing it to avail "main" and "guest" networks and ISP's are trying to build their own large scale "public hotspot" services by using all their subscribers to offer an "public hotspot" SSID. But each SSID isn't tuned to a separate radio channel, they can all use the same one and hence you can observe their RSSI as the same or similar.

Then, in big installations, we would deploy multiple AP's (sometimes hundreds on big sites) and advertise the same SSID's out of all of them - we don't use different SSID's for each AP. So again it's not unusual to see the same SSID out of different AP's on different channels. If you were to visit some of the big deployments I've done, you'd find most of the campus had locations where you could find my SSID's on all channels because you'd be very likely to be "in range" of multiple AP's all tuned differently (say 1,6,11.) Sounds like you are seeing something like that with your "joes" SSID's - probably 2 AP's tuned to different channels advertising the same SSID(s.)

I'm not surprised the FCC and ISP haven't intervened, as nothing your have described is "wrong" - Wi-Fi is "just like that" I am afraid.
ok thnks , i just meant by seeing the same ssid name twice for each band running on 2 different channels means that the person has 2 wifi AP's their own wifi router and the ISP issued cable modem which has it's own wifi AP built into it ,the techs here are not too bright they come in and install their cable modem with it's built in wifi AP ,put it in bridge mode and connect it to the customers own wifi router so now they have 2 wifi routers operating right next to each other
instead of asking them which wifi AP they want to use, the answer is obvious if they have their own wifi router they would only be using that , the cable company likes to keeps it's customers ignorant of the fact that leaving on 2 wifi AP's next to each other will cause interference for them and the neighbors they also mainly (i think) want to keep them ignorant about the existence and details of their public "xfinity" hotspot ,it is a walled off open guest channel for anyone with a subscription to that that same ISP to use ,they just log in with their account information
on their device then their device will jump to any of those open hotspots it finds ,most customers are either not aware of the public hotspot channel being turned on by default or do not realize that when it is in use it used their bandwidth , probably not such a big deal for downloading but the up speed is pretty low at least the bottom tier and mid tier packages
they do not want people requesting the hotspot be turned off

anyways went out and bought a fancy new high end router it has been 2 days so far no problems ,my old router was a linksys e3000 with 6 internal antennas the new one has 3 external ,not sure how name internal if any

so maybe it was the router causing issues?
but my question now is this ,i have though of flashing the old linksys e3000 with DDWRT
and setting it up as a repeater to extend my network but if that router has some problem with it
then will it cause problems for the client devices i have already set up and connected tot he main router? like will i get drops if those devices decide to connect to the e3000 instead of directly to the main router?
say the devices i have connected now all work fine with no issues connected to the main router
is there a way to tell them to only connect to the main router and never to the repeater ?
i mainly want the repeater to cover the yard and the garage for using cellphones in the yard and maybe for a sonoff wifi switch for the exterior lights on the garage and maybe an old phone running and IP camera app
 

mickevh

Distinguished Member
A modem is a very simple device that does little more than terminate the line and convert the data stream from one format to another (e.g. DOSIS to ethernet or whatever.) It would be highly unusual for a modem to include things like Wi-Fi Access Points and ethernet switches. Such things are usually (and also incorrectly) called "routers," though they are to hell and back different to what an IT professional would know as a router. In the UK, some of the ISP's are rebranding their "routers" to things like HomeHub" and "Superhub" and so forth.

Also, in the UK, some of these "SuperHubs" etc have a "modem only" mode which defeats all but one of the ethernet ports, suppresses the AP and disables the routing functions, etc.

In the "Using Two Routers Together" FAQ pinned in this forum, there's a block diagram that describes (roughly) the internals of a typical SOHO "router" (AKA SuperHub, homeHub, etc.) albeit one without a modem stage.

Having multiple Wi-Fi AP's physically close to each other is not particularly a problem as long as they are not tuned to the same or similar radio channels. The situation isn't fundamentally any different to the process of channel planning for more distant devices. Even when they are physically close and tuned to the same channel, the Wi-Fi protocols have some "good neighbour" mechanisms that kick in when the RSSI's get above certain thresholds to try and prevent them tripping over each other.

By way of examplar, when equipping something like a function room or a meeting hall (or in my case lecture theatre) where one expects there to be many devices, we often deploy multiple AP's to reduce the contention ratios (number of clients per AP) even though a single AP would adequately "cover" the physical space. Though even so, we'd tend to space them out a bit unless there was no other choice. Typically in that scenario, we'd also "fix" the channel plan rather than let it auto-tune.

If you want to use your old router as a second AP, there's a few hoops to jump through in order to get it working. It's described in the aforementioned "Using Two Routers Together" FAQ. Though IIRC we don't delve into channel planning in that FAQ (and SOHO gear doesn't "talk" to each other to automatically devise a channel plan as a "managed" enterprise system would.)

The only way to ensure devices don't hop between your AP's (or "roam" as we usually call it in the business) is to give them different SSID names. In that case, your clients will never roam until they completely loose connection with the incumbent whence the clients will "start from scratch" as if you'd just powered them on.

Or to put it the other way around, if you do want to have your clients roam automatically, the SSID's, passphrases must be the same. Even then, beware of "Big Wi-Fi Myth Number 2" that clients are always "hunting for the best signal" - in fact they do not and some need it to get pretty grotty before they consider roaming.

A lot of client devices create a kind of "profile" for each Wi-Fi SSID they have ever used and sometimes these profiles are maintained in an list in order of preference. You could have a look at your clients and see if they have such and will allow you to manipulate the order of the list (e.g. Windows avails this.)

One "trick" you can use to prevent a client joining a particular SSID is to let it find it and form such a profile then do things like, demote the profile to the lowest ranking and/or "corrupt" the profile so that it will never succeed in making a connection - e.g. make sure the passphrase is invalid. Some clients will allow you to determine whether a particular profile is used automatically or require manual intervention (again Windows as the e.g.) there is a setting in each profile (on by default) to "automatically connect when network is in range" or words to that effect, so simply just untick it.
 
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_Dragon_

Active Member
I'm in a flat above a business, My router is in the hallway I can see the business below has two routers one is named Ext, As the business shuts at 5pm would it be best to have my router on 6 also? My thinking would be as they shut at 5pm then there would be no activity on the router.

If I use a app on my phone it shows the channels is clear when in the hallway where my router is but if i move into the living room then I pick up loads as I'm on the main road with lots of businesses and flats. So I'm not sure what channel I should be picking, channel 11 is clear in the hallway but its not if I go into the living room.
 

mickevh

Distinguished Member
Look for the channel that yields the greatest "margin" (difference) compared to any others on or near the same channel. ie, the greatest difference between them.

Incidentally, just because there's no-one in session with your neighbours router dosen't mean it isn't doing anything - witness the fact that you can see it advertising itself (typically ten times a second) with your sniffer. There's also plenty of other "management" traffic broadcast by (all) Wi-Fi devices that you average freebie sniffer doesn't report - for example you don't see any reports from client devices (some of the paid for sniffers report clients - maybe get of of a trial version if you want to scare yourself! :D )

However, when there is no-one else around, there will probably be less competition for some "air time" meaning you might experience better throughput, but that's really dependent on how busy your neighbour's network usage is.

In urban environments these days, there is practically no chance of finding a completely clear channel all to yourself in the 2.4Ghz waveband. Paradoxically in the 5GHz waveband, the signal strength drops off with distance faster which means you are more likely to find clear channels as the neighbour's transmissions are more readily blocked (and/or curtailed) by "stuff" (walls, doors, air,) - and there's more channels available to choose from.
 

_Dragon_

Active Member
Cheers looks like channel 11 is the best then even though the apps all say 1 is better than 11, when I look at the graph you can clearly see channel 1 has lots going on.
 

_Dragon_

Active Member
I have discovered something as Channels 1 6 11 are the ones to use without any overlapping, Why would channel 1 make the wifi signal on the tv drop its signal bars? put it to channel 6 or 11 and it goes back up.
 

mickevh

Distinguished Member
There's many potential reasons, some of which we couldn't determine without proper spectral analysis tools (that's tools that look at the actual radio waves, not just the data emerging from a Wi-Fi NIC.) Even then, Wi-Fi is fickle and can still leave us scratching our heads wondering what's going on and uttering "but it should be working" - Wi-Fi's "just like that." :D

But to give a flavour of the sort of things that could be going on (in no particular order and this is not an exhaustive list...)

The radio frequencies Wi-Fi uses are not dedicated to Wi-Fi, other things use them such as Bluetooth, baby monitors, microwave ovens, car alarms, video senders, etc.

The effects of reflections, retractions, destructive/constructive interference, scattering, etc. could be particularly bad on C1.

Some devices' "bar" meters do not report signal strength (RSSI) but instead report signal "quality" which is not at all the same thing. Some (in an attempt to aid users) report some sort of notional "how good the service is going to be" which doesn't have any definition based on actual measurable physical values. Best not to assume that the meter is reporting RSSI - check it out to be sure.

Sometimes with Wi-Fi one has to be a bit "zen" about it and not over think it - if you find something that works, go with and do not worry too much about what is not working (much as so doing offends my OCD.) :D
 
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_Dragon_

Active Member
So what do you do when you have interference with your wifi and it affects your speed so much you can't use your phone or ipad, can you buy a adapter so you can use ethernet?
 

mickevh

Distinguished Member
Unless your client device offers such as an ethernet adapter, then a Wi-Fi Access Point is the Wi-Fi-to-ethernet bridge.

If you suspect interference, one first needs to prove it - it's no use "just assuming." That might need some tools that cost quite a lot of money and the surveys can be very time consuming to complete which is probably not worth the effort and expense for most SOHO users.

You could try using changing radio channels and see if that avoids the interference source - though the dynamic nature of the RF environment Wi-Fi uses may mean that doesn't work for long, if at all.

You could try deploying additional AP's closer to the locale where you use your clients. Such is generally the most effective solution. Even then it's not guaranteed; Wi-Fi is inherently unreliable and fickle, not least because no-one "owns" the transmission medium (the radio airwaves) and they are available for anyone to do pretty much anything they like with so long as they remain within permitted maximum transmission power. Essentially, eveyone just has to "play nice" together, though of course just because they should, doesn't mean they do. Ultimately, you may just have to be a bit "zen" about it.
 

psychopomp1

Well-known Member
So what do you do when you have interference with your wifi and it affects your speed so much you can't use your phone or ipad, can you buy a adapter so you can use ethernet?
If you router & clients support them (many 3rd party routers do), try the higher powered (~ 1 watt) 5ghz DFS channels - they are numbered around 120. These are perfectly legal channels in Blighty, however they are also radar channels so your router will automatically kick you off these if it detects any conflict - so probably not a good idea to use them if you live near an airport/airfield.
 

_Dragon_

Active Member
Unless your client device offers such as an ethernet adapter, then a Wi-Fi Access Point is the Wi-Fi-to-ethernet bridge.

If you suspect interference, one first needs to prove it - it's no use "just assuming." That might need some tools that cost quite a lot of money and the surveys can be very time consuming to complete which is probably not worth the effort and expense for most SOHO users.

You could try using changing radio channels and see if that avoids the interference source - though the dynamic nature of the RF environment Wi-Fi uses may mean that doesn't work for long, if at all.

You could try deploying additional AP's closer to the locale where you use your clients. Such is generally the most effective solution. Even then it's not guaranteed; Wi-Fi is inherently unreliable and fickle, not least because no-one "owns" the transmission medium (the radio airwaves) and they are available for anyone to do pretty much anything they like with so long as they remain within permitted maximum transmission power. Essentially, eveyone just has to "play nice" together, though of course just because they should, doesn't mean they do. Ultimately, you may just have to be a bit "zen" about it.
I'm in a flat above a business I'm pretty sure the interference I'm getting is from their equipment, it doesn't happen all the time, It's a pain because they have now decided to open up later and now work some weekends, When the interference happens my speed drops right down something they have definitely blocks out the signal. I don't think it's because everyone is on the same channel when it comes to Ap's

If you router & clients support them (many 3rd party routers do), try the higher powered (~ 1 watt) 5ghz DFS channels - they are numbered around 120. These are perfectly legal channels in Blighty, however they are also radar channels so your router will automatically kick you off these if it detects any conflict - so probably not a good idea to use them if you live near an airport/airfield.
Maybe I should be thinking about getting a 5ghz router but the thing is does mobile phones and ipads work on 5ghz.

I am in the process of hard wiring everything I can it just leaves the mobile phones/ipad.
 

psychopomp1

Well-known Member
Maybe I should be thinking about getting a 5ghz router but the thing is does mobile phones and ipads work on 5ghz.
Most new-ish smartphones and most (if not all) ipads support the 5ghz band.
 

mickevh

Distinguished Member
I'm in a flat above a business I'm pretty sure the interference I'm getting is from their equipment, it doesn't happen all the time, It's a pain because they have now decided to open up later and now work some weekends, When the interference happens my speed drops right down something they have definitely blocks out the signal. I don't think it's because everyone is on the same channel when it comes to Ap's
This is exactly the symptoms one would expect if they are using the same radio channels as you. Wi-Fi is fundamentally a "only one thing at a time can transmit" technology. There more things in the area, the more data they transmit, the more contention there is for some "air time."

Some people make the error of thinking that the only thing that matters with regard to air time contention is stuff that's Associated with your AP - but that's not the case, the air time contention rules are based on what can hear what, not what's in session with which AP.

I live in flats, whilst my router and my neighbours may not be able to "hear" each other, when we are both sat on our respective sofa's either side of our party wall, both our client device can hear each other very well and have to play nice together, which means if we're both busy fiddling, it hits both of our "speeds." The only mitigation available is to try and use different non-interfering radio channels.

The 5GHz radio penetrates "stuff" (walls, doors, air,) less well which in such situations can be actually beneficially as we are less likely to hear each other. Contrary to popular belief, "more power from the router" is not the universal cure all for Wi-Fi interference - not least because it does nothing about transmissions from the clients to the AP's.

It's simplest to think of it in terms of sound: If you are getting bleed through from the neighbours conversation (and remember the "only thing at a time can talk" rule) then one party in my conversation shouting louder will cause the neighbours to shout louder in response then we get onto a huge arms race. The better solution is for us all to talk less loudly and move closer together in our respective properties. Same for Wi-Fi - more AP's closer to the client and/or better radio channel planning and management is the solution.

Channel interference is particularly bad in the 2.4GHz waveband because the radio transmissions penetrate further and there's very few channels to choose from (than 5GHz) hence the suggestion to try 5GHz.

Maybe I should be thinking about getting a 5ghz router but the thing is does mobile phones and ipads work on 5ghz.
Their products of the last few years do - Apple publish some data on what wavebands, protocols, speeds, etc. their kit supports.
 
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_Dragon_

Active Member
Thanks, I actually think it's something electrical interfering using the 2.4ghz band rather than something they are using through wifi, first I thought it was a microwave but it can't be as it happens alot and it goes on for ages. Sometimes you hear a rumbling sound which makes me think its a appliance of some sort.

Biggest mistake I made was saying yes to this flat, The agency said it will be nice as they shut at 5pm and don't work weekends, that was right but six months later it all changed. they became loud and now work late and even weekends.
 
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mickevh

Distinguished Member
It's not unknown, esp. in the 2.4GHz band - video sender, baby monitors, car alarms, (my favourite,) etc. use the same frequency band.

The Wi-Fi rules about air time contention take this into account. Wi-Fi is "listen before talk" protocol and the standards lay down criteria about how "quiet" other transmissions need to be before they can be disregarded, (there's almost always some level of background "noise" - again think of it in terms of sound,) - IIRC that threshold is a bit higher for non-Wi-Fi devices than Wi-Fi ones.

@psychopomp1 - DFS, ah what fun - one of my jobs was in central London and our AP's used to go nuts whenever Heathrow was on westerly ops. and the planes were being vectored over us! :D
 

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