EAP225 - very low signal strength - measuring 4m from AP
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I have been trying to troubleshoot this signal strength issue with my EAP225s. I have two of them installed with a distance of 9m between them; no walls or structures in-between. Both APs are backed by a cat7 cable from the PoE ports on a TP-Link SG1008P switch. The cable lengths are less than 20m. I also tried to use the PoE adapter, but the signal strength remained low.
Even with the measuring device (a macbook pro laptop running netspot) placed equidistant between the two APs, at a distance of 4m, with clear line of sight to both APs, the maximum RSSI was just -45, as shown in the image below. (The 4 SSIDs with a tick on the checkbox are mine)
The picture changes drastically when I move just 3 metres into a room, with a brick wall separating the APs from the laptop. Please find the image from Netspot below.
- The strength from one of the APs drops down to -61 (n) and -76 (ac). This AP is about 8m from the laptop with a brick wall in-between.
- The strength from the other AP drops down to roughly -54. I am practically right under this AP (2m), but a brick wall is in-between.
I have been trying to play around with the signal strength dBm in the Omada SDN. Since the APs are not too far away, I tried reducing the dBm. But it had no effect.
I am not sure if these signal strength numbers are to be expected. In the NetSpot screenshots above, you would have noticed that there are some other SSIDs which are coming from other apartments which have a better RSSI than mine in my own apartment. Different channel, so it doesn't really borther me. But the question of signal strength remains.
When I did a "survey" on NetSpot, it showed a uniformly "mid level" signal throughout my house, including right below the APs.
Because of the bad signal strengths, the wifi performance is very poor, especially on the "802.11n" SSID. I am not sure what I should do to improve the signal strength. Any suggestions are welcome. Thanks!
Hey Anjan
There may be some confusion over the stats you have got so far, hopefully i will be able to clarify these for you.
These screenshots are showing the a mix of seperate things. Lets start with the LEVEL (SNR) column and shows your Signal to Noise Ratio,
SNR is how "clean" the airway is when compared to background noise, ideally you want as clean a signal as possible. Things like reflection of the signal from mirrors, metals or other APs will reduce this. The lower SNR the less "speed %" you will get from your WiFi. SNR ranges from 0 to 100, an excellent signal is around 50 SNR and with that you should be able to get the full "speed" of your wireless, normally SNR of around 30/40 is considered good. I have only ever seen 60 SNR in lab test and perfect scenarios. You are getting SNR of 42-50 which is very good
Next lets look at the Signal, this is the actual Signal Strength measured in -Db
As mentioned you are never going to get a perfect signal, as soon as you interduce a medium there is some loss. For that reason signal ranges from -30 to -90 with -40 to -70 being the range you are looking for (excellent to poor) once you hit -75 low lower its dead signal.
Signal strengthis freatly affected by lots of things, the biggest being walls.. when I do site surveys you can generally predict signal based on the plans. Take an AP and start at -40db, for every wall add -8 to -30db depending on the wall constuction.. here are the general loss expectations.
-8 stud wall with electric cables
-12 solid wall (single brick)
-20 Concrete or Breeze block
-30 Extra heavy or twin skin walls (cavity inbetween)
I can only guess the wall you are going through is breeze block or concrete cinder, liekly load bearing. If that is the case a drop from -45 to -70ish is not unexpected. When planning if we come accross these walls they are classed as terminators, namely you need another AP on the other side. Sorry but this may be the case, the chimney in my house has the same effect and pretty much the same Db loss.
Lastly and arguably the most important.. the channel width. OK so this is split into 20mhz blocks, you can add these together into sections to increase the WiFi throughput. In 2.4ghz range these are 20/40 in 5Ghz 20/40/80/160
Take a 300mbps N class card on 2.4Ghz - with 20Mhz bandwidth this will get 150mbps, 40mhz will get 300mbps (in theory) An AC card connected at 866mbps when using 80mhz will drop to ~430 on 40mhz, ~210mbps on 20mhz.. you get the idea. Fundamentally for "speed" you want this as wide as you can get.. however! the wider you increase this the more chance of interfernce of some type.
You have seen that channels 36 40 44 48 etc are available for 5Ghz, each of these are 20mhz wide.. if you set for 80mhz you will use ALL of those channels... namely faster speeds. The article you mentioned about reducing to 20mhz is more for capacity, say in a school where you need 100 devices in one room with 4 access points.. reduce the channel to 20mhz and fit 4 on different channels rather than 1 flooding the whole thing. capacity over speed basically... At home dont worry about this :)
The reason i advised to force 80mhz is to get as much speed as possible, yes you will interfere partially with others but thats their issue... 70% of 866mbps is better than 100% of 200mbps.. Only thing this this could potentially reduce signal strengh as you are flooding the place in wifi.. (-5Db at a guess).. however its worth it.
Ok to answer your questions..
- The attenuation I experience when I am just one wall away got me worried. Approximately -75dBm just 8m away, with one wall in between. If the wall is cinder block / breeze then thats likely and not suprising..sorry -30Db
- Also, seeing neighbours' networks from very far away with a higher strength than mine also got me worried. Depending on the direction this will be possible.. someone from next door though a single wall / window and not breeze may have this. Its just the way it is..
- And on the NetSpot survey, the colour scale they show puts -45dBm bang in the "mid-range average strength" category. This is showing SNR and not signal strength... ideally you want to be close as possible to middle (50 or so)
- I changed it back to 80 MHz, but no difference in signal strength. It wont, channel width is for speed /capacity and not signal.
Sorry that was a lot of info.. basically if you have -75Db signal strength you need another access point to cover that area. try to maintain -45 to -65 in most parts. I have 2x APs on either side of my chimney for the same reason..
SNR (the green map) is fine all round so you dont need to worry.. there is no apparent interferance so your wifi should be clean (reduces retries, drops)
Stick to 80mhz on 5G wifi, this will give you as fast as possible... no reason to drop this down.. on the 2.4ghz however its so congested in general sometimes 20mhz is useful, personally I just leave it auto..
Look into doing IPERF3 tests, these will give you the actual rate your wifi is going in mbps, on a 80mhz channel 5Ghz AC wireless card I would expect this to be around 300/350mbps.. below is one I done recently using the EAP245 with a AC1200 card so its a bit faster than what the EEAP225 will get
Hope this all helps and good luck
Phil
Hey Anjan
-45db is a good signal strength with -60 to -70 being the normal, clients should only start considering roaming to another AP if the signal approaches -80db
However I do notice that your SNR is quite high and the channel width on the 5GHZ is 20mhz, I would expect this to be 80mhz. Being on 20 will greatly limit the speed you recieve, could well be the auto setting is not appropiate for your airspace.
To address this hop onto the device via the controller and set the channel to force 80mhz then retest this. Also set the power back to HIGH or if you really want to custom set it go 16, higher isnt always better..
ideally you are better using something like IPERF3 to test the speeds on WiFi, I would expect 300/350mbps on a 5ghz with 80mhz channel as a good average. You will never get the 866mbps that the device claims to be connected at
Remember signal strength isnt the be all and end all. I have plenty of customers with poor signal strength but its a clean of interference therefore works fine. Your signal strength doesnt seem bad at all if honest.
Hey Anjan
There may be some confusion over the stats you have got so far, hopefully i will be able to clarify these for you.
These screenshots are showing the a mix of seperate things. Lets start with the LEVEL (SNR) column and shows your Signal to Noise Ratio,
SNR is how "clean" the airway is when compared to background noise, ideally you want as clean a signal as possible. Things like reflection of the signal from mirrors, metals or other APs will reduce this. The lower SNR the less "speed %" you will get from your WiFi. SNR ranges from 0 to 100, an excellent signal is around 50 SNR and with that you should be able to get the full "speed" of your wireless, normally SNR of around 30/40 is considered good. I have only ever seen 60 SNR in lab test and perfect scenarios. You are getting SNR of 42-50 which is very good
Next lets look at the Signal, this is the actual Signal Strength measured in -Db
As mentioned you are never going to get a perfect signal, as soon as you interduce a medium there is some loss. For that reason signal ranges from -30 to -90 with -40 to -70 being the range you are looking for (excellent to poor) once you hit -75 low lower its dead signal.
Signal strengthis freatly affected by lots of things, the biggest being walls.. when I do site surveys you can generally predict signal based on the plans. Take an AP and start at -40db, for every wall add -8 to -30db depending on the wall constuction.. here are the general loss expectations.
-8 stud wall with electric cables
-12 solid wall (single brick)
-20 Concrete or Breeze block
-30 Extra heavy or twin skin walls (cavity inbetween)
I can only guess the wall you are going through is breeze block or concrete cinder, liekly load bearing. If that is the case a drop from -45 to -70ish is not unexpected. When planning if we come accross these walls they are classed as terminators, namely you need another AP on the other side. Sorry but this may be the case, the chimney in my house has the same effect and pretty much the same Db loss.
Lastly and arguably the most important.. the channel width. OK so this is split into 20mhz blocks, you can add these together into sections to increase the WiFi throughput. In 2.4ghz range these are 20/40 in 5Ghz 20/40/80/160
Take a 300mbps N class card on 2.4Ghz - with 20Mhz bandwidth this will get 150mbps, 40mhz will get 300mbps (in theory) An AC card connected at 866mbps when using 80mhz will drop to ~430 on 40mhz, ~210mbps on 20mhz.. you get the idea. Fundamentally for "speed" you want this as wide as you can get.. however! the wider you increase this the more chance of interfernce of some type.
You have seen that channels 36 40 44 48 etc are available for 5Ghz, each of these are 20mhz wide.. if you set for 80mhz you will use ALL of those channels... namely faster speeds. The article you mentioned about reducing to 20mhz is more for capacity, say in a school where you need 100 devices in one room with 4 access points.. reduce the channel to 20mhz and fit 4 on different channels rather than 1 flooding the whole thing. capacity over speed basically... At home dont worry about this :)
The reason i advised to force 80mhz is to get as much speed as possible, yes you will interfere partially with others but thats their issue... 70% of 866mbps is better than 100% of 200mbps.. Only thing this this could potentially reduce signal strengh as you are flooding the place in wifi.. (-5Db at a guess).. however its worth it.
Ok to answer your questions..
- The attenuation I experience when I am just one wall away got me worried. Approximately -75dBm just 8m away, with one wall in between. If the wall is cinder block / breeze then thats likely and not suprising..sorry -30Db
- Also, seeing neighbours' networks from very far away with a higher strength than mine also got me worried. Depending on the direction this will be possible.. someone from next door though a single wall / window and not breeze may have this. Its just the way it is..
- And on the NetSpot survey, the colour scale they show puts -45dBm bang in the "mid-range average strength" category. This is showing SNR and not signal strength... ideally you want to be close as possible to middle (50 or so)
- I changed it back to 80 MHz, but no difference in signal strength. It wont, channel width is for speed /capacity and not signal.
Sorry that was a lot of info.. basically if you have -75Db signal strength you need another access point to cover that area. try to maintain -45 to -65 in most parts. I have 2x APs on either side of my chimney for the same reason..
SNR (the green map) is fine all round so you dont need to worry.. there is no apparent interferance so your wifi should be clean (reduces retries, drops)
Stick to 80mhz on 5G wifi, this will give you as fast as possible... no reason to drop this down.. on the 2.4ghz however its so congested in general sometimes 20mhz is useful, personally I just leave it auto..
Look into doing IPERF3 tests, these will give you the actual rate your wifi is going in mbps, on a 80mhz channel 5Ghz AC wireless card I would expect this to be around 300/350mbps.. below is one I done recently using the EAP245 with a AC1200 card so its a bit faster than what the EEAP225 will get
Hope this all helps and good luck
Phil