Internet Bandwidth speed issue Fortiap

[ganesh_karale]

Hi, Customer is having FAP231F and they are having ISP with 500mbps bandwidth.

On wired network is gives speed more than 400mbps but on wifi getting speed upto 225-250mbps.

For testing purpose connected AP directly on Fortigate interface with single user connected on wifi, getting speed upto 225-250mbps only.

Channel width is 40mhz and client system is connected on 5ghz band.

Same time TP Link wifi router is providing speed upto 400mbps.

Can someone suggest to get more speed on FAP wifi.

[Stephen_G]

Hello ganesh_karale,

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.

Thanks,

[laltuzar]

Hard question to answer. Let me try to summarize as best as I can.

Depending on the client's spatial streams, SNR, channel width and WiFi amendment one wireless client can reach up to 2402Mbps PHY on 5GHz (802.11ax). For that to occur, 1024-QAM modulation must be used. In reality, this speed is unreachable, at least for "speedtest" or "real world speed" purposes. This is because this speed is negotiated and is PHY speed, no overhead traffic is taking into consideration. Most of the traffic on a WiFi environment is management and control framesm, that is overhead. As a non written rule we can say that in reality a wireless client can reach up to 1/3 or 1/2 of the PHY speed negotiated by the transmitter. This speed gets negotiated all the time, so it is almost impossible to have a completely steady speed on WiFi. Moreover, this speed will only be guaranteed on the managed network (LAN). Outside to the internet is impossible to guarantee a speed as it depends which server is being reached out, routes, hops in between, etc.

On an enterprise environment most likely you will have STAs supporting 2x2:2 and only a few supporting 3 spatial streams (ss). So on best case scenario, those clients could reach up to 2402.0 PHY and 3602.9 PHY when connected to 802.11ax on 160MHz and 2x996-tone RU and using the highest modulation the amendment permits (1024-QAM). If we divide these speeds to half (again, best case scenario), we can get the "real world speed" to internet, which is at best 1Gbps. Of course, talking about a controller environment, 1 user connected, using best modulation, zero interference, no LAN issues, etc. On real world this is hardly achieved.

On 802.11ac story changes a bit as highest speed for these devices are 1733 PHY (2ss) and 2340 PHY (3ss) speeds. Taking in consideration connection on 256-QAM modulation, 160MHz channel bonding, SGI enabled and 34 dBm SNR. Again, dividing on a half (best case scenario), an AC device connected with 3 spatial streams on highest modulation can reach up to 1150Mbps on "real world" speed. But you have to take into consideration that on real world these conditions are very rarely met. Not even on enterprise environments where there is interference everywhere. You can read this KB to get more info about real world speeds: https://community.fortinet.com/t5/FortiAP/Technical-Tip-Real-world-WIFI-performance/ta-p/246664 

To understand a bit better the real speeds and what to expect from WiFi on enterprise environments and WiFi in general, I recommend you to watch these videos from Wireless LAN Pros:

> https://wlanprofessionals.com/mcs-table-and-how-to-use-it/

> https://www.youtube.com/watch?v=x0JGjjbEJvU

> https://www.youtube.com/watch?v=QBiBPbME5tY

Basically, the less noise, the better modulation and therefore the better PHY speed.

Should you need assistance from Fortinet to improve network connectivity on your environment, please get in touch with your sales representative to quote our Professional Services. More info about this service on this link: https://www.fortinet.com/support/support-services/professional-services 

Hope it helps.