segunda-feira, 1 de fevereiro de 2016

Wi-Fi - User numbers

There is no “hard limit” on the number of users. The more users, the slower the connection becomes. This is because they all poll the AP randomly so you get stronger signals overwhelming weaker ones and the AP has to try to make sense of it all. The generally recognized limit for public AP’s is 25-30.
What happens when 35 people attach? Their service generally slows to a crawl.
30 to 35 users is not an absolute hard limit. You can assign perhaps 50 casual users and have little contention. More than 35 actively connected users and you’ll start to see degraded service as the compete.
With a Rocket for non-Ubiquiti client radios, the maximum that Ubiquiti specifies is 50. For Ubiquiti clients using AirMax (PtmP), it’s about 150.
Useful formula: for all client traffic / 10 -%.
So if you have 40 client which provides 1 MB. The theoretical value of the network will be 40 * 1 MB = 40 MB and the average is 10% full – 4 MB
Different factors that effect user experience.
  1. In all cases the data rate available from the access point is limited to some maximum. It may be the limit of the Internet provider, or it may be the total combined data rate for all clients. Of course the lower of these two values is the limit.
  2. If clients are all to be provided a 10Mbps rate, an access point may be able to support only five or six clients (assuming the Internet source can also provide this rate).
  3. Regardless of the total data rate, the radio is also limited to a maximum number of clients. This is due to memory limitations; a Rocket has twice the memory of most other Ubiquiti radios, so it can handle 50 clients instead of 35 for the others.Naturally if the Rocket services 50 clients, the combined data rate is in the range of 50Mbps, or 1Mbps each, distributed evenly.
Your choices with Ubiquiti radios are about 35 users, or –with double the RAM (Rocket) –about 50 users (non AirMax)
The only difference between Rocket and lesser ‘M’ series radios is that it has
twice the RAM. Otherwise virtually the same radio.
Every AP (including Cisco, Aruba, etc, etc, etc) can only really handle 30 (ish) active users. This is a limitation of the 802.11 protocol. They can also only handle 10-15 HEAVY users per AP. Again, it effects all vendors
As a tip, on a campus, you typically want to run your APs on low power to limit the distance between clients on an AP. Google “Hidden Node” to learn more. Also, make sure to not space APs too close together or you get interference, collisions and the “Exposed Node” issue. This effects all vendors, though some handle it a smidge better than others.

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