Wireless coverage and latency

[chrisz]

Hello, we have 4 MR34 access points throughout the main office. Two on the first floor and two on the second floor. 

I find from time to time that the speed of the wireless is just less than acceptable yet I have a good connection to the AP. 

We have a daily average of 130 users on the APs. The table below is from a weekly report.

Is that # of clients very high for an MR34?

  Model Usage # Clients

1	MR34	1.74 TB	141
2	MR34	559.73 GB	103
3	MR34	103.33 GB	128
4	MR34	92.72 GB	145

Should I look at adding more APs to the office space? Can I create a space that is too densely populated where the APs signals cause too much noise adversely affecting the connections?

[PhilipDAth]

I think that is excessive.  Once you get more than 50 users for AP you should expect the performance to suck.  If a customer tells me they want a good experience I trend to use an AP per 20 to 25 users.

[MAG]

 Hi Chrisz,

It all depends on how intense is the workload that the users put on each AP.

It might be ok to connect  150 users if the barely use bandwidth, but since you said that sometimes you noticed a a decreased speed i would say that you should consider  adding more AP to evenly spread the workload.

The connection to the AP is just a link that depends on the strength of the signal, then the speed on that link is determined by that signal but also by the client equipment specs.

Under Network-wide/client /signal you can check the strengh of the signal in db that in general must be higher that 20db.

Legacy clients can affect very badly to the overall performance/throughtput.

Hope it helps.

Best

Miguel Angel

[CKilinski]

How many concurrent clients do you have on these APs? If those numbers are concurrent then you definitely need to get more, but if there are only 15-25 clients then it depends on their usage at any given time.

[chrisz]

If I look at concurrent clients right now it ranges from 19 - 36 depending on the access point.

[Sameh_Sackla]

You need to take into consideration a couple of things: 1-No of concurrent users vs total users (as this will impact BW and AP resources) 2-BW required per user (as this will impact how many users per AP) There is a good article to calculate the number of APs needed if you want to do proper capacity planning: https://documentation.meraki.com/MR/Deployment_Guides/High_Density_Wi-Fi_Deployment_Guide_(CVD)#Capa... Thanks

[HardWaire]

Very nice documentation ! I’m deploying Meraki AP for a building of 17 floors and this déployment guide is a good read !

Tx for sharing

[LeoG]

Good to know this helps you. I would also recommend for such a large deployment (17 floors) to plan the deployment using a tool like Airmagnet or Ekahau (there are more but these are the ones I've worked more with) because signal tends to leak between floors and the channel planning and transmit power needs to take that into account, and these tools are very good to simulate it, and after the deployment, they are also good for validating the whole deployment.

[LeoG]

The major problem with having many concurrent users on an AP is the contention window each end device has to go through for actually being able to transmit something into the air. 

This is usually solved by:

- Deploying more APs.

- Reducing the effective cell size by reducing the transmit power and increasing the minimum bitrate.

- Placing the APs nearby the end devices.

If you want to see if the issue is related to channel utilization, you can look at Wireless > RF Spectrum which will tell you the actual utilization of the channels you are using.

Additionally, if you think this may be due to cells being too large and frames collisions, you can capture a monitor mode PCAP nearby one of the APs.

Here we have a really good document on how to do this monitor mode captures:

https://documentation.meraki.com/MR/Monitoring_and_Reporting/Capturing_Wireless_Traffic_from_a_Clien...

Alternatively, I would recommend Airtool by Adrian Granado's if you're using a MacOS device to do the captures.

After taking the PCAP, apply this filter on Wireshark: (wlan.fc.retry == 1) which will show retries percentage.

As a guideline, anything above 10% is usually not acceptable in most designs. We have a really good KB for channel deployment best practices.

https://documentation.meraki.com/MR/WiFi_Basics_and_Best_Practices/Channel_Planning_Best_Practices

Hope it helps 

[chrisz]

Thank you. I'm going to soak all this in and review.