I had a resync at approx. quarter past midnight. I had investigated it since I have been having some weird spikes recently, some that have knocked out connectivity. In this case, nothing prior to the resync - just 1 as the Retrain Reason.
What I did notice was a sizeable increase in downstream attainable, going from 347 Mbps to 383 Mbps.
Before:
Max: Upstream rate = 67849 Kbps, Downstream rate = 347559 Kbps
Bearer: 0, Upstream rate = 50016 Kbps, Downstream rate = 335116 Kbps
Link Power State: L0
Mode: G.fast Annex A
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 4.7 8.8
Attn(dB): 31.5 0.0
Pwr(dBm): 0.0 4.0
After:
Max: Upstream rate = 67037 Kbps, Downstream rate = 383312 Kbps
Bearer: 0, Upstream rate = 49976 Kbps, Downstream rate = 328995 Kbps
Link Power State: L0
Mode: G.fast Annex A
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 6.9 9.1
Attn(dB): 29.2 0.0
Pwr(dBm): 0.0 4.1
10% would be a lot if no variables had changed, so there must have been a reason - and there was:
Before*:
Discovery Phase (Initial) Band Plan
US: (368,1927)
DS: (368,1927)
Medley Phase (Final) Band Plan
US: (368,1808)
DS: (368,1674)
After:
Discovery Phase (Initial) Band Plan
US: (348,1802)
DS: (342,1666)
Medley Phase (Final) Band Plan
US: (348,1800)
DS: (342,1666)
It seems they have adjusted the Band Plan for Downstream so it starts 1345.5 kHz lower, and 1035 kHz lower for the Upstream (this is based on 51.75 kHz spacing). The initial plans have changed, too; the Downstream is 13506.75 kHz less at higher frequencies, and Upstream is 6468.75 kHz less.
If we look back to end of May this year, ISPreview had posted some news
here about G.fast co-existence. While options have been considered to improve speed and coverage, it seems reducing the start point for G.fast to approx. 17.7 MHz is what has been taken - at least for now.
19.044 ((368 * 51.75)/1000 - previous G.fast start point, in MHz) minus 1.3455 equals 17.6985 MHz, which is only a little above 17.664 MHz (bandwidth for VDSL 17a). While I could be a little bit off, this would still suggest that the start point has been reduced.
In conclusion, it seems Openreach may be now rolling out these changes nationwide to improve coverage (and bring existing users a speed boost). I am not aware of the exact changes made, so I am going on the information I have from my own connection and comparing historical data.
If anyone has access to their G.fast stats, it would be appreciated if you could take a look to see whether your connection has been subject to these changes yet.
*This was not directly before the resync since DSLstats had not been logging pbParams, but these stats are still applicable having checked bitloading from the last snapshot.Edits:
22/08/2019, 12:48: Clarified some information, fixed a mistake.