RM500U-EA (RM500UEAAAR03A11M2G) - Is newer firmware available?

IoT Modules 5G Module
, ,
1

Hello everyone,

I am using a Quectel RM500U-EA integrated in a ZBT Z8105AX-2SIM router.

Current modem firmware:



RM500UEAAAR03A11M2G

I have spent quite a bit of time troubleshooting an issue where the modem achieves very low throughput despite having what appears to be an excellent LTE radio connection.

Some observations:

  • Operator: Telia Sweden

  • LTE Band 3

  • RSRP around -79 dBm

  • SINR around 22 dB

  • Stable connection

  • Ethernet interface to the router is 1 Gbps Full Duplex

  • APN configuration verified

  • Power saving disabled

  • Tested multiple LTE cells using QNWLOCK

During active traffic:

  • AT+QCAINFO always reports only a PCC

  • No SCC carriers are ever established

  • AT+QENG="servingcell" always reports the NR5G-NSA section as all zeros

I’ve also tested different LTE cells (PCI 360 and PCI 27) with nearly identical results.

At this point I’m beginning to wonder if this could be related to the modem firmware rather than the network or router.

I’ve noticed several users here mentioning that Quectel has provided newer firmware versions directly through support.

My questions are:

  1. Is RM500UEAAAR03A11M2G the latest firmware available for the RM500U-EA?

  2. Are there any known issues related to Carrier Aggregation or NSA operation in this firmware?

  3. Would it be possible to obtain a newer firmware version for testing if one exists?

I’d really appreciate any advice or guidance.

Thank you!

2

Dear @oddname
I have sent to your email, please check.

3

My router now has the newst fw, modem also newest FW (i might need more to try, experimentals etc.

But I have really bad speeds. The 5G frequency and channles used makes no sense for me using telia here in Sweden. My smartphone selects better bands etc. I suspect there is a issue with FW, most likely Carrier Aggregation since it does not seem to be used at all currently.

With smartphone I get, 170Mbit, with router using RM500U-EA 4Mbit… same spot, exact same carrier and simcard. So what could be the issue? Signal strenghts etc matching quite nicely besided channels etc. and CA.

5

I am troubleshooting a Quectel RM500U-EA modem and would greatly appreciate your assistance. I have spent considerable time investigating this issue and have ruled out many of the obvious causes, but I am now at a point where I believe deeper modem knowledge is required.

Hardware

  • Module: Quectel RM500U-EA

  • Firmware: RM500UEAAAR03A13M2G_01.302.01.302

  • Router: ZBT Z8105AX

  • Operator: Telia Sweden

  • Network: 5G NSA

Problem description

When the system was first installed, performance was very good.

Without any hardware changes, the throughput gradually became significantly worse.

The following have not changed:

  • Same physical location

  • Same router

  • Same modem

  • Same firmware

  • Same antennas

  • Same SIM subscription

  • Same operator

The modem now frequently selects:

  • LTE Band 20 + NR n28

  • LTE Band 8 + NR n3

When forcing LTE Band 3, radio quality becomes extremely poor:

  • RSRP ≈ -114 dBm

  • RSRQ ≈ -19 dB

  • SINR ≈ -18 dB

With automatic band selection, the modem generally avoids Band 3.

The modem initially performed well in this exact location, making me question whether this is related to modem behaviour, network changes, or an RF issue.

Antenna testing

To eliminate the antenna as a variable, I have tested with:

  • Original LTE antennas supplied with the router

  • External 4x4 MIMO antenna

Both configurations produce very similar behaviour.

Comparison with a smartphone

A smartphone using the same operator, tested at the same location, generally achieves considerably higher throughput than the router.

This makes me wonder if there is either:

  • an RF hardware issue,

  • modem configuration issue,

  • or a difference in how the modem selects LTE anchor cells.

Questions

  1. Is there any known issue with the RM500U-EA regarding LTE anchor selection or EN-DC behaviour on European LTE/5G NSA networks?

  2. Is there any method to influence LTE anchor selection beyond the documented AT+QNWPREFCFG commands?

  3. Does the modem maintain any persistent neighbour-cell history, mobility history, or other internal information that can be reset?

  4. Are there any engineering or diagnostic AT commands that expose:

  • individual RF chain measurements

  • MAIN/DIV/MIMO1/MIMO2 receive levels

  • per-chain RSRP

  • per-chain SINR

  • antenna diversity status

  • MIMO stream status

I would like to verify that all four RF receive chains are operating correctly.

  1. Is there any command that can report whether all four antenna ports are active and functioning normally?

  2. Are there any engineering commands for checking RF calibration or detecting an internal RF hardware fault?

  3. Is there a newer firmware available that improves:

  • LTE cell selection

  • NSA anchor selection

  • RF performance

  • Carrier Aggregation behaviour

Available information

I can provide any requested modem logs, including:

  • AT+QENG="servingcell"

  • AT+QCAINFO

  • AT+QENDC

  • AT+QNWINFO

  • AT+QNWPREFCFG

  • firmware information

  • additional engineering logs if required.

Any guidance or recommended diagnostic procedure would be greatly appreciated.

Thank you for your time and support.

Best regards,

6

Unexpected anchor behaviour.

My observations

The modem consistently selects:

  • LTE Band 8 as the LTE anchor (PCC)

  • NR n3 as the secondary carrier

Even though a smartphone placed next to the router, using the same operator, connects differently and achieves noticeably higher throughput.

The smartphone typically uses:

  • LTE Band 3

  • Multiple LTE component carriers (CA)

  • 5G NSA

while the RM500U remains on a much simpler B8+n3 combination.

Hardware / setup

  • Quectel RM500U-EA

  • Latest public firmware (01.302.xx)

  • External 4x4 MIMO antenna

  • Sweden (Telia)

  • Same location, same antennas, same time as the smartphone comparison

I’ve also tested another operator (Comviq/Tele2), where the modem immediately selected B3 + n78 and performance improved significantly.

What I’m trying to determine

I’m not trying to prove there’s a firmware bug—I’m simply trying to understand whether this behaviour is common.

If you’re in Europe (especially Sweden, Norway, Denmark, Finland, Germany, etc.) and have an RM500U, RM520N or another recent Quectel modem, I’d really appreciate if you could share:

  • Country

  • Operator

  • Modem model

  • Firmware version

  • AT+QCAINFO

  • AT+QENG="servingcell"

  • Typical download speed

  • If possible, a comparison with a smartphone at the same location

I’m especially interested in cases where:

  • the modem prefers B8 even though B3 is available,

  • or where the modem appears to use fewer LTE component carriers than a smartphone on the same network.

The more data points we collect from different operators and countries, the easier it will be to determine whether this is operator-specific, firmware-related, or simply expected behaviour.

Thanks in advance!

I think I might be on to something!

7

Dear @oddname
Thanks for your information.
As you mentioned, the signal of B3 is poor, so module will choose other combinations.
Mobile phone and RM500U has different RF hardware, so there will have difference.

You can try to lock the same combinations with mobile phone and check result.