[HOW TO] Diagnose Wireless Issues

Iccz

Distinguished Member
There have been a lot of questions regarding the stability of wireless connections over the last few months/years. Because of this I figured it would be helpful to many if we had a thread that outlined the starting points for diagnosing wireless issues, I will also include some background information which you may or may not wish to read - it will not essentially help problem solving but it might help understanding.
At present this thread is only dealing with Windows software. If any Mac users are reading this and wish to offer input then please let me know.
Also please let me know if anything needs correcting or editing in any of these posts. Thanks.

The biggest problem is that wireless networking has become very common as well as popular and along with this has come the expectation that it will just work, sadly this is not always the case. For wireless networking to work, and to work well there are a number of requirements that must be met.

Background information.

As I said I will share a little background on the key points to wireless networking and the technologies involved, reading this part will mean that you will be on the same page as me when explaining things further on, but as I said before it's not essential reading.

There are 3 main types of wireless networking that you should know about, they are: B, G and N. Wireless networking usually communicates in the 2.4, 3.6 and 5 GHz frequency bands but mostly 2.4. Most networks offer 11 channels but sometimes you can get up to 14. The channels are divisions of the 2.4 GHz range, these channels overlap each other though. Channel 1 uses the lowest frequency and it increases along with the channel number - there are 3 main channels which do not overlap with each other these are 1, 6 and 11 - because of this these are the three most used channels.

The range of wireless networking equipment should never be taken at face value, the figures that are specified are generally perfect world and they do not give for the various types of interference which almost all users will have such as Electromagnetic interference (EMI), Walls and channel bleed to name some.

Wireless security is not something I plan on covering here but I figure it's worth mentioning that WEP security is easily hacked and some versions of WPA can also be hacked - contrary to what appears to be popular belief that WPA is 100% safe.

Common problems.

There are a number of common problems that get raised and they are:
1) Connected but not working - usually this is a case of not actually having network access.
2) Unable to connect - usually this is a case of configuration, passwords are case sensative and sometimes you might have WPA2 instead of WPA1.
3) Slow network - usually this is down to interference, low signal strength or access point saturation.
4) Intermittent connection - this is usually down to the same points as above but mostly interference.

Free tools for testing.

I will be going into detail on how to use inSSIDer after this post and may include details for the other apps at some point in the future.

Windows Tools.

inSSIDer - This is a tool that many members here will mention if someone has a wireless issue.

Chanalyzer - This is a tool brought to you by the same people who make inSSIDer, this app gives you visualisations of your wireless landscape.

Xirrus Wi-Fi Inspector - This is a tool which is very similar to inSSIDer but provides a different layout, the information is similar but some people prefer to use a different layout.

Ekahau HeatMapper - Slightly more advanced is HeatMapper which can provide you with a good site audit of signal strength and access points on a graphic map of your site. Not really very useful for home use but worth mentioning.

Mac Tools.

KisMAC - A free Wi-Fi scanner app, often recommended here for Mac users.

AirRadar - Used to be free but now I believe it is an app you buy, old versions may still be free although I do not know.
 
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Iccz

Distinguished Member
Using inSSIDer.

I am going to assume that you have downloaded and installed inSSIDer and are ready to run the program.

Depending on the version of the software you may see a different screen to that of which I have screenshots for at the moment, I will try and update according to any new versions shortly, but the information within should be the same.

So here is the first screen we should see:



The first thing you should look at is at the top, before scanning you will see the drop down menu with network adapters, for this you obviously need to select your wireless network adapter, then click the Start button. Once you have done that you should start to get something that looks a little like what I have posted.

First you see a list of surrounding networks with details of them, then under that you get 2 graphs, the line graph on the left shows historic data for your signal strength and the one on the right shows current strength for all selected networks.
If you do not wish to see all of the surrounding networks in the graphs you can untick them with the boxes in the list view.

List view.

Okay so now you have a load of information on the screen but you don't really know what it is or what you should do with it...

The columns:

1) MAC Address - This is the physical address of the router/access point, it is a unique address that identifies the device. This is of little importance to our diagnosis.
2) SSID - This is the name of the network broadcast by the device - this helps you identify your network.
3) Channel - This is the channel that you are using.
4) RSSI - Received Signal Strength Indication note that the Wikipedia article conflicts with the information within inSSIDer, don't worry about this. This column is signal strength, the lower the number the stronger the signal; -48 is stronger than -93. Signal strength ranges between around -30 and -100.
5) Security - This shows what security type is being used, WPA, WEP, WPA2 and so on.
6) Network Type - Does what it says on the tin, not an important factor here.
7) Speed - Shows what speed the device is showing - most will be set to Automatic speed but some may be forced to certain speeds.
8) First/Last Seen - Again, self explanatory, these signal when you first and last saw the network while scanning.

I have put 3 of the above in bold as these are the ones which we will concentrate on, these are: SSID, Channel and RSSI.

First you need to ensure you are looking at your network, so you will need to look at the SSID to find that, once you have located that then look at your Channel and compare it to what the surrounding networks are using, if there are a lot of networks on the same Channel as you then you might be better off changing your channel to a different one. As previously mentioned try stick to 1, 6, and 11 as these have no overlap with each other. You can usually change these settings very easily in your router configuration page - if you get stuck then someone will help you providing you state the make and model of your device.
Also you will want to look at the RSSI column - if you have connection problems in certain areas of your house try running the scan and checking the RSSI in various areas and see how your signal drops or changes in different places.

If you are asking for help with wireless problems after this, please include details of your testing so that whoever is helping you can see that you have tried the basics and can then try and figure out what might be the problem based on your results.
 
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Chaihana Joe

Active Member
Thanks for starting this, Iccz, and I really hope this thread takes off.

As a wireless user with Windows, OSX, and Android clients as well as games consoles (big family), we get all sorts of connectivity problems. Trouble is, it's hard to know where to start with diagnosing the source of the problems.

I'll be trying all the tools you mention there, but it would be good to have some recommended websites covering the theory and any top tips (possibly including DHCP which seems to be implicated in our setup).
 

Iccz

Distinguished Member
Thanks for starting this, Iccz, and I really hope this thread takes off.

As a wireless user with Windows, OSX, and Android clients as well as games consoles (big family), we get all sorts of connectivity problems. Trouble is, it's hard to know where to start with diagnosing the source of the problems.

I'll be trying all the tools you mention there, but it would be good to have some recommended websites covering the theory and any top tips (possibly including DHCP which seems to be implicated in our setup).
Thanks for the input, Joe.
I will definitely be adding some links with more information at some point, I just wanted to get the thread up and running as a starting point, I'm sure the more technical members will throw some corrections and changes my way to help it become a more complete guide :thumbsup:
 

beerhunter

Novice Member
1. As a wireless user with Windows, OSX, and Android clients as well as games consoles (big family), we get all sorts of connectivity problems. Trouble is, it's hard to know where to start with diagnosing the source of the problems.

2. I'll be trying all the tools you mention there, but it would be good to have some recommended websites covering the theory and any top tips (possibly including DHCP which seems to be implicated in our setup).
1. Use inSSIDer or kisMac on a PC that supports them to eliminate Channel Conflict. Fixing it for one set of devices fixes it for all.

2. DHCP problems will,affect wired as well as wireless devices equally. The rule of thumb for amateurs is to leave DHCP to run you IP addressing unless you know what you are doing. More amateurs get themselves into trouble using fixed addressing than get themselves out.
 

Chaihana Joe

Active Member
Thanks beerhunter.

1. Use inSSIDer or kisMac on a PC that supports them to eliminate Channel Conflict. Fixing it for one set of devices fixes it for all.
The laptop I'm running inSSIDer on may be particularly insensitive, but it can only see our own router. My Nokia tablet on the other hand can often see half a dozen. Thing is, even if inSSIDer did show all these SSID's, I'm not sure how best to avoid overlap. Iccz's notes suggest using channels 1, 6 or 11 as these don't overlap. But IIUC it is only true that these channels don't overlap each other - they do overlap the in between channels. Channel 6, for example, overlaps every channel from 2 through 10 (source: Wikipedia). It seems there is no chance of completely avoiding overlap.

2. DHCP problems will,affect wired as well as wireless devices equally. The rule of thumb for amateurs is to leave DHCP to run you IP addressing unless you know what you are doing. More amateurs get themselves into trouble using fixed addressing than get themselves out.
Why so? This was going to be my next tactic. Surely it is straightforward to map a dedicated IP address to each MAC address. Can you expand on what the pitfalls are?
 
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Iccz

Distinguished Member
The laptop I'm running inSSIDer on may be particularly insensitive, but it can only see our own router. My Nokia tablet on the other hand can often see half a dozen. Thing is, even if inSSIDer did show all these SSID's, I'm not sure how best to avoid overlap. Iccz's notes suggest using channels 1, 6 or 11 as these don't overlap. But IIUC it is only true that these channels don't overlap each other - they do overlap the in between channels. Channel 6, for example, overlaps every channel from 2 through 10 (source: Wikipedia). It seems there is no chance of completely avoiding overlap.
The point about 1, 6 and 11 is that they do not overlap each other so are not going to conflict with each other, these are the 3 channels that are set to default values on most gear, 6 is usually the default but sometimes 1 or 11 are used too. The point is if you neighbours all use 6, then using 2 will not avoid it, but it will include anything from neighbours using 1... where as if you move to 1 you are just contesting with those on channel 1 (or perhaps someone if they are on another channel in between - which is not likely).
 

beerhunter

Novice Member
I'm not sure how best to avoid overlap. Iccz's notes suggest using channels 1, 6 or 11 as these don't overlap. But IIUC it is only true that these channels don't overlap each other - they do overlap the in between channels. Channel 6, for example, overlaps every channel from 2 through 10 (source: Wikipedia).
You are absolutely correct and I was going to ask that the sticky be reworded.

They way to use the tools is to do a survey in the rooms where you will be using WiFi, at different times of day. Once you know what is going on locally, set your router to a channel that not only is not is use but is at least two channels away from any that are. (I'd like a pound for every time that I have keyed that on these forum.)

If you can't find that happy place, then you may need to think of using 802.11n in the 5 gHz band, (Until that fills up. :D), or wired Ethernet, or HomePlugs.
 

Iccz

Distinguished Member
You are absolutely correct and I was going to ask that the sticky be reworded.
As above, I'm open to suggestions. All I have ever read on the subject specifies these 3 channels as "non-overlapping" although a closer look seems to make 1, 7 and 13 non-overlapping in Europe - but I don't believe this is always the case. I have changed it so that it reads they do not overlap with each other for now, but any other suggestions are welcome :thumbsup:
 

Chaihana Joe

Active Member
It looks like my neighbours favour the lower order channels, so I have moved to 11 (though I have a Netgear DGN1000, which also uses channel 7 when I select channel 11). It's possible that things have improved, though too early to say with confidence.

I hope you can also expand on the issue of hard coded IP addresses as a solution to possible DHCP problems. Beerhunter suggested this was best avoided, though I am still tempted and would like to know what the pitfalls might be.
 

beerhunter

Novice Member
I hope you can also expand on the issue of hard coded IP addresses as a solution to possible DHCP problems.
DHCP will manage your IP Addressing perfectly well and whether one uses DHCP or Fixed Addressing has no effect on WiFi connectivity because that is done further down the stack.

The pitfalls of Fixed Addressing are that one needs to ensure that any Fixed Addresses are not within the DHCP Server's Address Pool and keep a record of the IP Addresses that one has allocated (the DHCP Server does that for DHCP) so as not to give two devices the same addresses. (These things often get overlooked, especially as new devices are brought into the house and added to the network.)

I let DHCP do the work more than 99% of the time, using Fixed Addressing only in extremis.
 

Kristian

Well-known Member
I agree with Beerhunter about DHCP use for the home/SOHO, especually as you can reserve addresses in the home routers.

The pitfalls of Fixed Addressing are that I let DHCP do the work more than 99% of the time, using Fixed Addressing only in extremis.
Another pit fall of static addresses is that the DHCP service also gives out DNS server info (amongst other info), so if you change the DNS servers you use, or your ISP does (DHCP to your router's WAN interface), these changes are not propagated to the static devices and you'll have to change these yourself.
 

Chaihana Joe

Active Member
OK, having moved from channel 5 to channel 11 and given it a few days, I'd say that we're getting disconnects pretty much as often as before the change.

What I hadn't twigged before, is that Homeplug connected devices are losing their connections at the same time as devices using wireless connections.

For a bit, this made me think the router was a source of the problems. The router is a Netgear DGN1000, which we bought recently to replace a Netgear DG834. We made this change because we thought the DG834 might be faulty - we were having the same connection dropouts. But it seems unlikely that both routers are faulty in the same way.

So now I'm thinking there may be a problem with the wiring on the far side of the router. Which takes us well off topic for a thread devoted to wireless issues. But thanks for your help, anyway guys.

Perhaps another thread on fault finding beyond the router/modem is called for?
 

mickevh

Distinguished Member
...Iccz's notes suggest using channels 1, 6 or 11 as these don't overlap. But IIUC it is only true that these channels don't overlap each other - they do overlap the in between channels. Channel 6, for example, overlaps every channel from 2 through 10 (source: Wikipedia). It seems there is no chance of completely avoiding overlap.
That may be a reference to the "40MHz" AKA "channel-bonded" modes available in 802.11N.

The 2.4GHz band channel numbers - 1 through 13 - are just "labels" for a particular set of radio frequencies. These frequencies are 5MHz apart. C14 is a bit of an oddity and IIRC not available in Europe, so lets ignore that one.

So the channel numbers are essentially a shortcut to avoid having to remember what the actual radio frequencies are - C6 is easier to remember that 2.437GHz. Wiki's article contains the actual numbers for anyone interested.

Wifi transmissions don't use a "single" radio frequency like music radio stations (hence the "bell curves" InSSIDer sometimes draws are somewhat inaccurate.)

Wifi uses a "set" of 50 or so radio frequencies 0.3125 apart spaced out over 10MHz (ish) either side if the nominal centre frequency. Hence, a wifi radio "tuned" to C6 is also transmitting in the frequencies denoted as C4,C5,C6,C7,C8. Again, Wiki's 802.11 article illustrates this quite nicely. These are known as "20MHz" channels as used by 802.11 A/B/G.

802.11 N, in addition to 20MHz channels, allows "40MHz" channels, basically doubling(ish) the number of sub carriers which thence means the radio transmissions extend even further either side of the nominal centre frequency. So using 40MHz mode tuned to C6, the radio is transmitting sub carriers in the range C2 thru C10.

This is why 40MHz mode 802.11N can be a bit of a pain in the 2.4GHz waveband - 40MHz modes are taking up a lot of the available frequency spectrum and given the ever increasing number of wifi devices in the world, it's getting hard to find that much spectrum all to yourself (or at least, sufficiently free of interference to be reliable) unless you live in the middle of a large field.

For this reason, some people restrict their 2.4GHz "N" to use only "20MHz" channels to get a more reliable connection, albeit with a penalty of lower link rate.

EDIT 2015: The "AC" Wi-Fi protocol extends the "channel bonding" ideal even further by availing 80MHz and 160MHz "wide" channels. The details of how the "extra" channels are placed above/below the nominal channel are a little complex, so I won't describe them here, but doubtless Google is your friend for anyone that really wants to know.
 
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beerhunter

Novice Member
Just a quick point about how 'good' the WiFi is on ISP supplied routers.

Many people post on these forums asking for a recommendation for a new router because the ISP supplied one is "rubbish". Their problem is usually caused by the classic channel conflict and so using inSSIDer or Kismac will help solve it without the need for new kit.

As evidence for this point of view: most of the subscribers around me (deepest Hampshire) use the ISP supplied router, including lots of BT Home Hub 1.0/1.5s & 2.0s. WiFi problems around here are unknown. (I mean that literally.) I refuse to believe that the ISPs send us all the good kit and supply the "rubbish" to the more populated areas. Which must mean that the reason for our better WiFi performance is simply that our houses are further away from each other and thus interference.
 
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Iccz

Distinguished Member
Just a quick point about how 'good' the WiFi is on ISP supplied routers.

Many people post on these forums asking for a recommendation for a new router because the ISP supplied one is "rubbish". Their problem is usually caused by the classic channel conflict and so using inSSIDer or Kismac will help solve it without the need for new kit.

As evidence for this point of view: most of the subscribers around me (deepest Hampshire) use the ISP supplied router, including lots of BT Home Hub 1.0/1.5s & 2.0s). WiFi problems around here are unknown. (I mean that literally.) I refuse to believe that the ISPs send us all the good kit and supply the "rubbish" to the more populated areas. Which must mean that the reason for our better WiFi performance is simply that our house are further away from interference.
Couldn't agree more, there seems to be a lot of users spending money on new modem/routers when they don't need to. The main reason I see people buying them is because they believe the wireless or connection will be better with a different one. I can understand if someone requires features that are not provided on the ISP provided one but otherwise it seems like a waste of money. Generally wireless issues can be solved quickly and easily.
I think there are a lot of people who believe that a "known brand" like Netgear, D-Link or Belkin will be better because of the name and because it's going to cost money, I disagree - no ISP will provide duff kit as that would increase support calls and in turn their operating costs.
 

charleyfarley

Standard Member
This is a nice sticky and one that i expect thousands to visit and learn from. Good work chaps :thumbsup:

I hadn't had any problems with my broadband connection until i recently installed an old AppleTV. It works fine wirelessly most of the time but since installing i have seen a fair few dropped signals on my 2wire HG1800... however, in my limited experience i sense interference and not hardware, this thread adds confidence to my convictions. Thank you :D

Is there a simple to follow instruction for Kismac somewhere?
 

p9ul

Distinguished Member
I currently use a wireless connection to my router (Orange/Wanadoo Livebox) for everything in my house - (PC, Laptop, 360, PS3, DSi, iPhone x2) would this guide be beneficial to me to see if I could make any improvements?

My main area of concern is the connections to my game consoles (in another room to the router), can tinkering with the channel settings improve things like connection speeds or ping?

For info - I live on a housing estate in a rural area (about 3.5mb DL speeds at best) and my kit will usually "see" 4 or 5 of the neighbours networks. My router is also quite old dating from 2005, it does not support wireless N and I wonder if upgrading would be beneficial.
 
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Iccz

Distinguished Member
It certainly wont harm to have a look, Paul.

The software is free and it only takes 10 minutes to do a full scan and get a feel for what is happening, so I would say give it a shot and see how your results look - if there are a lot of neighbouring networks sharing the same channel you can try changing your wireless channel and see if you notice any difference. You can always change back if not. You have nothing to lose :)
 

p9ul

Distinguished Member
I ran inSSIDer last night and channels don't seem to be a problem for me - mine was using 1 whereas all my neighbours were on 9.

my signal strength didn't look to clever though - it was rated at about -64. Can I improve this somehow?
 

mickevh

Distinguished Member
You mentioned you're concerned with gaming and ping time (latency.) In a typical home network, I would think the quality of your broadband service would have a (much) bigger influency on online gaming than the wifi performance. You may be looking in the wrong place (wifi) if you're getting laggy gaming.

To improve wifi signal strength all you can really do is move closer to the AP's, either by moving your clients closer to the AP, of putting up more AP's closer to the clients.

However, before throwing money at the problem, I'd try setting up a PC cabled to your network somewhere and run some continuous ping against your (wifi) gamestations wherever it is you typically use them and see what the response is like. If such local ping times are good (ie not involving the broadband link) then you can infer that wifi isn't the cause of any gaming issues, and you should look to the broadband service instead.
 

evilbunny

Standard Member
Sorry to have to say this, but:

Using inSSIDer.

[...]
4) RSSI - Received Signal Strength Indication note that the Wikipedia article conflicts with the information within inSSIDer, don't worry about this. This column is signal strength, the lower the number the stronger the signal; -48 is stronger than -93. Signal strength ranges between around -30 and -100.
This is a common mathematical error: the numbers quoted are all negative, so -48 is bigger than -93, not smaller. :p Think of it this way: if you start with a suitably large number, such as 200, and subtract 48, you'll end up with a larger result than if you subtract 93.

Seems to be a good post otherwise.
 

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