FWA515 does not reconnect to N78 automatically after temporary band loss

adrianf0 · 1:48AM

Hello,

I am experiencing an issue with the Zyxel FWA515 router.

The device randomly loses access (often during the night) to the N78 band and switches to the much slower N1 band. This might happen because the carrier temporarily disables N78.

However, when N78 becomes available again, the router does not reconnect to it automatically. In many cases the band is not even detected on the CellWanStatus page. The connection remains on N1 until the router is rebooted.

After rebooting the router, it immediately reconnects to fast N78 and the connection returns to normal.

I have observed this issue with both firmware versions available on the website:

V1.60(ACPZ.0)C0
V1.50(ACPZ.0)C0

Steps to reproduce

Router connects normally using NR5G-NSA with N78 band.
The network appears to temporarily disable N78 (this is my hypothesis).
The router falls back to N1.
When N78 becomes available again, the router does not reconnect to N78 automatically.
In some cases, N78 is not even shown in the CellWanStatus page.
After rebooting the router, it reconnects to N78 immediately.

Expected behavior

The router should automatically reconnect to N78 when the band becomes available again.

Actual behavior

The router remains connected to N1 until the device is rebooted.

Additional information

Operator: Swisscom
Country: Switzerland
Access Technology: NR5G-NSA

The issue typically appears during the night (approximately 00:00–06:00) when N78 seems to disappear temporarily.

I also tried enabling the Network Monitoring feature on the router to see if it would recover the connection automatically when N78 becomes available again, but this did not resolve the issue. The router still remains connected to N1 until it is rebooted.

Manual band selection and disabling N1 is not an acceptable workaround for me, because it reduces bandwidth. Carrier aggregation between N78 and N1 would no longer be possible.

For comparison, as I am evaluating 5G modems for my home network (FWA515 is one of the candidates), I tested the same SIM card in a Mercusys MB520-5G router placed in the same physical location. That device maintains a stable connection with N78 band.

Connection details (when the device works normally)

Module Information

IMEI 3569929********
Module SW Version QuectelT830R22A02_OWT2305_BETA20250527_xx.001.xx.001

SIM Status

SIM Card Status Available
IMSI 2280159********
ICCID 894101**************
PIN Protection Disable
PIN Remaining Attempts 3

IP Passthrough Status

IP Passthrough Enable Enable
IP Passthrough Mode Dynamic

Cellular Status

Cellular Status Up
Access Technology NR5G-NSA
Operator Swisscom
PLMN 22801
Data Roaming Disable
TAC 1112

NR5G-NSA Information

Band N78
RFCN 640704
UL Bandwidth (MHz) 100
DL Bandwidth (MHz) 100
RSSI (dBm) -96
RSRP (dBm) -108
RSRQ (dB) -11
SINR (dB) 9

Service Information

Band B20
RFCN 6300
UL Bandwidth (MHz) 10
DL Bandwidth (MHz) 10
Cell ID 17890818
Physical Cell ID 227
RSSI (dBm) -93
RSRP (dBm) -104
RSRQ (dB) -11
SINR (dB) 1

SCC Information #1

Band B3
RFCN 1301
DL Bandwidth (MHz) 20
RSSI (dBm) -100
RSRP (dBm) -119
RSRQ (dB) -17
SINR (dB) -12

SCC Information #2

Band B7
RFCN 3100
DL Bandwidth (MHz) 20
RSSI (dBm) -108
RSRP (dBm) -125
RSRQ (dB) -18
SINR (dB) -2

NR5G SCC Information #1

Band N1
RFCN 425310
DL Bandwidth (MHz) 20
RSSI (dBm) -94
RSRP (dBm) -117
RSRQ (dB) -22
SINR (dB) -11

If needed, I can also provide logs or additional diagnostics.