RM551E-GL does not work CA with Cell lock, upload CA only works when B3 PCC, lte_mimo_info bug

IoT Modules 5G Module
21

You always find an excuse…

The output power at the base station is the same per PRB on both B3 layers, therefore the RSRP difference on both B3 cells should not be more than 3 dB when one cell is running 1x1 SISO and the other is running MIMO.

Now it just so happens that both modems have the same PCC and CA, so here’s a comparison:

signal
signal1234×459 9.49 KB

How can the RM551E-GL measure an RSRP difference of as much as 16 dB on the same band, on two cells, one operating on SISO and the other on MIMO?

While the old RG501Q measures only 1-2 dB RSRP difference and that is correct.
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SINR BUG
But yesterday the modem switched to another sector on the same base station and the SINR values went crazy

Video:


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The moment at which the wild SINR was on all SCC cells:
signal2
signal2698×246 109 KB

Rebooting the modem solved this problem but it comes back sporadically because the power saver on the base station randomly turns off/on the cells (B3 and B1).

You seriously need to update the FW for the RM551E.

22

Dear @Tirkiz
I have sent a newer firmware to your email, please try.

1 Like
24

Dear @silvia, I received the email, thank you!

25

Hello, i have also RM551EGL00AAR01A03M8G_A0.001.A0.001 on my RM551E and problem with CA on T-mobile USA, can you send me never firmware for test, thank you

26

Dear @silvia
in the new FW, it seems that my problems are still present…
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SINR BUG
When modem changes direction or eNB - in SCC cells SINR gives wrong values (240+)


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Upload modulation
Upload modulation is still low (I assume QPSK and max 16QAM) because RM551E gives low UL speeds compared to the old RG501Q.

I didn’t feel like recording that either…
Suffice it to say that the old RG501Q on B1+B3 (20+20 MHz) gives an upload speed of 160 Mbps and the RM551E on the same cells with the same antennas and the same signal gives around 60-90 Mbps.
This is especially noticeable when I test a single cell, without CA.

It would be good if the existing AT commands could find out the UL modulation, at least for the PCC cell.
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RSRP incorrect measurement of 1x1 SISO cells
I haven’t tested it yet

27

Dear @Tirkiz
Please help to capture modem log.Do you have USB port?
Windows or Linux?

1 Like
28

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

29

The RM551E-GL struggles with CA when Cell Lock is used it only uploads CA when B3 is the PCC. Also noticing a bug in lte_mimo_info likely a firmware or modem handling issue.

30

Thanks for the detailed breakdown! It’s clear the RM551E-GL performs best with B3 as the primary band, especially for upload CA. It’s odd that UL aggregation doesn’t function consistently on other PCCs, even when QCAINFO shows otherwise. Also, the MIMO info bug after cell shutdown is definitely something Quectel should address. Great troubleshooting work!

31

Hi @silvia
sorry for the late reply, I was on the road so I couldn’t reply :slight_smile:

I’m testing the RM551E in an OpenWRT router, a Debian Linux PC (via USB) and a Windows 11 PC (via USB). Can you send me instructions for both OSes. I’ll be happy to record the modem log.

32

You want to lock the main cell (PCC) so it doesn’t change, like your old RG501Q did. Your modem now picks PCC automatically, which lowers speed sometimes. Unfortunately, there’s no easy way to lock only the PCC while letting the modem add other cells. Check with modem support for a fix.

33

I tested the RM551E on 5G-NSA with the N78 band, I commend the modem on low signal levels giving almost 500 Mbps :slight_smile:

It seems that the 5CA does not aggregate upload or aggregate PCC with N78 but this cannot be read from AT+QCAINFO
I assume that the upload aggregates PCC with N78 by MIMO info.
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However, incorrect SINR values appear in AT+QCAINFO at random intervals

+QENG="servingcell"
+QENG: "servingcell","NOCONN"
+QENG: "LTE","FDD",219,01,55A8E00,57,1300,3,5,5,7DC,-104,-14,-70,15,14,190,-
+QENG: "NR5G-NSA",219,01,343,-111,0,-12,634080,78,12,1

AT+COPS?
+COPS: 0,0,"HT HR",13

AT+QCAINFO
+QCAINFO: "PCC",1300,100,"LTE BAND 3",1,57,-104,-16,-73,9
+QCAINFO: "SCC",500,100,"LTE BAND 1",1,57,-107,-16,-82,241,0,-,-
+QCAINFO: "SCC",3600,50,"LTE BAND 8",1,57,-79,-15,-55,4,0,-,-
+QCAINFO: "SCC",6300,50,"LTE BAND 20",1,57,-86,-17,-61,253,0,-,-
+QCAINFO: "SCC",634080,12,"NR5G BAND 78",343

AT+QNWCFG="lte_mimo_info"
+QNWCFG: "lte_mimo_info",57,1300,4,1
+QNWCFG: "lte_mimo_info",57,500,2,0
+QNWCFG: "lte_mimo_info",57,3600,2,0
+QNWCFG: "lte_mimo_info",57,6300,2,0

AT+QNWCFG="nr5g_mimo_info"
+QNWCFG: "nr5g_mimo_info",343,634080,2,1
34

Dear @Tirkiz
I have sent the tool to you via Message, please check.
Please list the combination of your carrier, I will check whether it supports or not.

1 Like
35

Yes facing this issue with newer firmware some time stop working internet when restart device solve issue carrier agrecation not support properly plz solve this issue and update soon if any new firmware come plz send

36

Here is a video comparison of UL speeds, old vs new modem.
Same cells, CA, antennas and base station.

It is clearly visible that the new RM551E uses lower modulation in upload and at the time of testing UL CA did not work. UL CA works very rarely, I do not know by what principle, it does not even matter if the PCC is B3 band.

At the time of testing the modem was obviously using UL 16QAM but a good part of the time it uses UL QPSK so I have upload speeds of 5-15 Mbps.

Apparently the new RM551E does not know how to negotiate the max UL modulation and UL CA with the base station compared to the old RG501Q-EU.

37

Just so you know, the old RG501Q-EU modem gave an upload speed of up to 150 Mbps on the same B1+B3 cells (a month ago)…

…and the record is 170 Mbps in upload on the same B1+B3 cells:

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Is there anything new about this modem?

Has a new FW been released that fixes these flaws?

Is the modem available for sale or is it still in the “engineer sample” phase?

Thanks!

39

Dear @Tirkiz
No update.
Still engineer sample.

40

Croatian Telecom (219-01) has started migrating LTE B1 and B28 to NR5G N1 and N28, with some base stations getting only N1 and the rest N28 band (they will have LTE B1 band).

I found out that their Ericsson RAN supports 5CA:

  • B1+B3+B3+B20+n28 (NSA)
  • B1+B3+B3+B8+n28 (NSA)
  • B3+B3+B8+B20+n1 (NSA)
  • B1+B3+B3+B8+B20 (LTE)

However, none of your modems can support this combination.
Can you arrange this CA combination on your RM551E to be supported?

This is especially useful for rural areas that do not have B7 or N78 bands.

Thanks!

41

Dear @Tirkiz
Some combinations also need hardware to support.
Currently, this modules doesn’t support these.

1 Like