I have been using router with UPS for some years and never had any problem. But recently facing a strange issue.
Normally my SNR with 8MB connection stays within 17.5-19.5 db with around 970KB/s download and 128KB/s (SNR: 21db) upload. This is on ONU number.
During loadshedding (on UPS) the SNR for downstream drops to 13.5-14.5 range and download speed drops to < 30KB/s but upload stays at 128KB/s with no change in SNR.
In both cases the ping stays the same at about 30ms.
I did tests across the board with all mobile devices and PC. Resetting the router. WiFi on/off. The results are the same.
I am using TP-Link W8961 Modem/Wifi router for last 1 year or so. But only recently this problem has become a major issue as I can't even browse when on UPS. UPS itself is very stable 3KVA/2x170 Amp hour batteries. Also the WiFi performance of this router is very poor.
If anyone else has experience like this and found a solution please share, or any suggestions are welcome. I haven't tested the PTCL router yet which I will do next time loadshedding happens to rule out if router needs replacement.