So while I was playing Tekken 7, a fighting game dependent on low ping, on my laptop's WiFi card, I get occassional stutters. I then decide to try using my phone as a USB tether to the laptop, only to have buttery-smooth gameplay. I was dumbfounded at this discovery. How could my phone give such latency free play?
I have implemented SQM into the router to reduce latency, but sometimes when I do a ping test to Google, a sudden spike of over 1000 ms occurs. Usually, the ping is under 60 under normal packets but occassionally rises to 70, 80, or even 100+ (and the aforementioned 1000+ ping)
Is there a possible explanation as to why this occurs? If so, is there a way to mitigate such ping spikes?
No other wifi clients than the laptop connected to the phone?
Just connect also all your other wifi devices to the phone, and then see if the connection is still latency free...
You forgot to tell us anything about your router, connection and SQM settings. (and what kind of other traffic there possible is)
You are comparing apples with oranges here, WFi is a shared, but not very well managed resource, while GSM/LTE/5G is something where the basestation has considerable control over the scheduling of all stations, allowing to harmonize them. While in wifi things like cyclic frequency scans happen, during which a station will loose access to the AP on purpose to see what else is around on other channels (and these scans in turn cause cyclic latency spikes, e.g. notoriuos for that is apples location service)...
To figure out whether SQM is making things worse you can:
a) try to connect the laptop with an ethernet cable to the router, to rule out wifi
b) Look at the output of tc -s qdisc the pk_delay/peak delay counter will tell you about how much internal latency cake observed, if that is in the range of the observed spikes SQM might be involved in your problem. Often when that happens the root cause is CPU overload, so cake will not be able to send packets in time, and both throughput tanks and latency/jitter increase.