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I want to use IEEE802.11 WiFi in infrastruture mode to communicate in both directions between an access point and several stations.
The amount of traffic between the stations and the access point is not very high and thus should not cause significant delays due to collisions between my stations and the access point in the CSMA/CA protocol.
However, the problem is that this setup could be operated in environments with several other WLANs present independent of my setup and not under my control. There could be heavy traffic in those WLANs and it is not predictable, which channels in the 2.4GHz band they will use, nor according to which of IEEE 802.11b/g/n they will operate. They may not even leave any free channel to use for relatively undisturbed transmission for my setup. Therefore, naturally I expect that my devices will contend with those other devices and will be subject to frequent collisions and thus increased delay times due to the backoff mechanism in the CSMA/CA protocol.
My goal is to have the least possible delay times for the WiFi traffic in my setup to have best possible performance. Ideally there would be a real-time guarantee for one request-response message exchange cycle between a station and an access point.
Is there any good way to reduce delay times by avoiding collisions with traffic from other WLANs (switching to 5GHz is not an option btw.)?
As far as I understand I will not be able to profit from a IEEE802.11e QoS implementation such as EDCA, since those only manage channel access within my WLAN. However, within my WLAN all messages have equal priority. Did I understand this correctly?
In case I am in the wrong stack exchange, please let me know!
I think you misunderstood 802.11 QoS. It lets you mark some traffic as higher priority (VO/VI) , allowing your clients to use shorter inter-packet wait times when sending that traffic, which means they get on the air sooner / more often than any normal priority (BE) or low priority (BK) traffic from ANY network in radio range. – Spiff – 2018-01-17T21:44:57.240
Ok, thanks for the hint. If I understand you correctly, this actually means that IEEE802.11e would help in my scenario to reduce delays caused by any other network in radio range. On the other Hand, if the other Networks would use 802.11e QoS and mark high priority traffic, I could suffer from even worse delays. Do I underand this correctly? – oh.dae.su – 2018-01-17T22:07:35.450
Yes, marking your latency-sensitive traffic as VO should definitely help you, and Yes, if you leave your latency-sensitive traffic marked as BE and someone else in radio range has VO traffic, their VO traffic will make your BE latency worse. – Spiff – 2018-01-17T22:13:28.817