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

IoT Modules 5G Module
1

Hello,
I am testing this modem on Croatian networks.

ATI
Quectel
RM551E-GL
Revision: RM551EGL00AAR01A03M8G

AT+QGMR
RM551EGL00AAR01A03M8G_A0.001.A0.001

Cell lock

On LTE networks, this modem is often on the primary B1 band (the base station has bands B1, B3+B3 (20+10 MHz), B20, B28)

Example:

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",219,01,24A350B,503,500,1,5,5,1068,-111,-11,-78,11,6,220,-
OK


AT+QCAINFO
+QCAINFO: "PCC",500,100,"LTE BAND 1",1,503,-110,-9,-78,3
+QCAINFO: "SCC",1300,100,"LTE BAND 3",1,503,-111,-12,-92,7,1,100,19300
+QCAINFO: "SCC",3600,50,"LTE BAND 8",1,503,-103,-10,-85,10,0,-,-
+QCAINFO: "SCC",6300,50,"LTE BAND 20",1,503,-101,-11,-81,4,0,-,-

Since I noticed that the upload speed increases only when the modem switches to B3 PCC by itself, I made a cell lock to B3 band:

AT+QNWLOCK="common/4g",1,1300,503

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",219,01,24A3502,503,1300,3,5,5,1068,-106,-8,-78,14,8,220,-

AT+QCAINFO
+QCAINFO: "PCC",1300,100,"LTE BAND 3",1,503,-105,-9,-76,9

No matter which band I lock it to, this modem does not work CA with the other available bands. Is there any solution for this?

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Upload CA only works when B3 PCC

Tested on a bad signal, no cell lock. On DL 4CA this modem gives excellent speeds (100+ Mbps) but 2CA upload only works when B3 PCC which is visible in the speeds even though QCAINFO shows that it aggregates 2CA UL on any PCC band.

When B1 is the primary band, even though QCAINFO shows that it is running 2CA UL with B3, speedtest gives an upload speed of around 5 Mbps:

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",219,01,24A350B,503,500,1,5,5,1068,-110,-11,-79,11,5,230,-

AT+QCAINFO
+QCAINFO: "PCC",500,100,"LTE BAND 1",1,503,-111,-12,-78,0
+QCAINFO: "SCC",1300,100,"LTE BAND 3",1,503,-113,-11,-95,7,1,100,19300
+QCAINFO: "SCC",6300,50,"LTE BAND 20",1,503,-101,-15,-77,4,0,-,-
+QCAINFO: "SCC",3600,50,"LTE BAND 8",1,503,-104,-10,-85,10,0,-,-

125/5 Mbps

When this modem switches to the primary B3 band by itself, then upload speeds really increase (apparently aggregating UL 2CA B3+B1):

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",219,01,24A3502,503,1300,3,5,5,1068,-104,-8,-76,15,9,190,-

AT+QCAINFO
+QCAINFO: "PCC",1300,100,"LTE BAND 3",1,503,-104,-8,-76,9
+QCAINFO: "SCC",6300,50,"LTE BAND 20",1,503,-100,-13,-78,6,0,-,-
+QCAINFO: "SCC",3600,50,"LTE BAND 8",1,503,-103,-12,-80,9,0,-,-
+QCAINFO: "SCC",500,100,"LTE BAND 1",1,503,-108,-11,-88,9,1,100,18500

112/8 Mbps

  • I once got an upload speed of up to 12 Mbps.

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AT command lte_mimo_info does not display MIMO info for low bands when the power saver on the base station shuts down some cells

When the base station shuts down the second B3 cell with EARFCN 1450, lte_mimo_info no longer shows MIMO info for the low bands. This is fixed by restarting the modem or it will fix itself when the shut down cell is turned back on.

This problem is also present on the RG501Q-EU modem (which I have).

An example when all cells are on:

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",219,01,24A3502,503,1300,3,5,5,1068,-105,-9,-75,14,8,220,-
OK

AT+QCAINFO
+QCAINFO: "PCC",1300,100,"LTE BAND 3",1,503,-105,-9,-76,8
+QCAINFO: "SCC",500,100,"LTE BAND 1",2,503,-107,-8,-80,11,1,100,18500
+QCAINFO: "SCC",1450,50,"LTE BAND 3",1,503,-105,-9,-88,12,0,-,-
+QCAINFO: "SCC",6300,50,"LTE BAND 20",1,503,-102,-11,-82,5,0,-,-
OK

AT+QNWCFG="lte_mimo_info"
+QNWCFG: "lte_mimo_info",503,1300,2,1
+QNWCFG: "lte_mimo_info",503,500,1,0
+QNWCFG: "lte_mimo_info",503,1450,1,0
+QNWCFG: "lte_mimo_info",503,6300,2,0
OK

When the power saver turns off the second B3 cell EARFCN 1450:

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",219,01,24A350B,503,500,1,5,5,1068,-80,-10,-50,23,15,160,-
OK


AT+QCAINFO
+QCAINFO: "PCC",500,100,"LTE BAND 1",1,503,-106,-8,-90,8
+QCAINFO: "SCC",1300,100,"LTE BAND 3",1,503,-105,-8,-76,9,1,100,19300
+QCAINFO: "SCC",6300,50,"LTE BAND 20",1,503,-101,-13,-79,11,0,-,-
+QCAINFO: "SCC",3600,50,"LTE BAND 8",1,503,-103,-12,-80,9,0,-,-
OK

AT+QNWCFG="lte_mimo_info"
+QNWCFG: "lte_mimo_info",503,500,2,1
+QNWCFG: "lte_mimo_info",503,1300,2,1
OK
  • AT+QNWCFG=“lte_mimo_info” only shows MIMO info for mid bands and low bands are gone
2

Dear @Tirkiz
No matter which band I lock it to, this modem does not work CA with the other available bands. Is there any solution for this?
=>You had lock only one band, so you didn’t see any CA.

For combinations, it is configured by operator, not module. If don’t want to use band1, you can configure LTE band without band1.

3

I use the RM551E-GL and RG501Q-EU modem in parallel and it aggregates all other bands on cell lock while the RM551E does not.

Do you still think it’s down to the operator configuration?

4

Dear @Tirkiz
What do you mean?RG501Q can the CA , but RM551E can’t, right?
What is cell lock?

5

Yes, on the same base station, the same operator - RG501Q when locking any cell automatically aggregates all other cells while RM551E does not aggregate :slight_smile:

I guess you know what cell lock is :smiley:
AT+QNWLOCK=“common/4g”

6

Dear @Tirkiz
AT+QNWLOCK=“common/4g”, this AT command only lock one cell. It can’t attach other cell.
Please note this.
RG501Q is a old project and EOL,I am not sure the behavior is normal or not.

7

Very strange…
Ok, is there any way to lock the desired cell that will be the PCC and the modem will aggregate all other available SCC cells itself like the good old RG501Q does (which I have for 3 years)?

Because if I use AT+QNWLOCK=“common/4g” to lock multiple cells, the modem again chooses which one will be taken as the PCC and changes it over time, which does not suit me. There are situations when it is important to me which cell should be the PCC and let the modem aggregate all other available cells itself, especially because of the power saver on the base station that turns other cells off/on.

Thanks :slight_smile:

EDIT: in the past I had lower bandwidth on B1, only B3 had the highest bw 20 MHz and since I use a large upload where the highest upload speed via the primary cell (PCC) is important to me, I always locked the old RG501Q to only B3 20 MHz and it aggregated all other available cells itself, which also gave me high download speeds and this has been great for years.

Now the operator has increased the bandwidth to 20 MHz on B1 as well, but the base station pushes everything to that B1 and when the modem uses B1 for PCC where it aggregates all other available cells (B1(PCC)+B3+B3+B20), the speeds are worse than when the PCC is B3 (B3(PCC)+B1+B3+B20).

Also since I have two B3 cells (20+10 MHz), the modem often knows to be primary on B3 10 MHz which drastically lowers the upload speed (and the download speeds are not good either) and for that reason I need to lock the PCC cell while the modem aggregates all other available cells itself.

8

The real question I am really curious about is why do you have 5G modules but I don’t see you’re connected to 5G at all? 5G would give you much higher upload speed than LTE. If you don’t have 5G signal, maybe using a parabolic 5g antenna aimed at the direction of a cellular tower that supports 5G could be the solution.

9

Hello @Semsem
I’m in a rural area, 5G is currently being rolled out, I’ll soon get N28 and N1 (25 MHz) by the end of the year. In other cities when I arrive I have the opportunity to test mmwave N257 with this RM551E (with the purchase of an N257 antenna).

Now on these 4G bands (B3(20MHz, PCC)+B1+B3+B20) I get 400/80 Mbps with 4x external Iskra P-60 directional antennas which is excellent (3 km away base station).

But with 5G NSA and LTE it’s important for me that the primary cell is B3 20 MHz since on all the others I get poor speeds due to lower bandwidth or primary cell load.

Also, the old modem does not support 4CA in combination with the future N1 band, which is why I took this RM551E.

1 Like
10

Thank you for the clarification. Have you tried to temporarily eliminate the competing frequency band (B1?) from the list of the LTE bands and test the speed? I know this is not what you are asking and is not an ideal compromise as it might reduce the overall speed but maybe not.

11

Yes, removing the B1 band is out of the question because my speed drops by 100 Mbps, depending on the load, which is why that B1 is also important to me in CA aggregation.
The best speeds are when the primary cell (PCC) is B3 20 MHz and the modem aggregates 4CA in which the B1 cell is also located.

When the primary cell is B1 and the others are in the aggregation, the speeds are worse even though now B3 and B1 have the same bandwidth.
And the results are also bad when the modem itself chooses B3 10 MHz for the primary cell, especially the upload speed.

On this old RG501Q-EU (which I still use as my main modem) I simply perform a cell lock on just one cell - B3 20 MHz and that modem automatically aggregates all other cells (4CA) including B1 and it has been working great for years and provides high speeds.

That’s why I was surprised that the same AT command on this new RM551E does not aggregate all other cells

1 Like
12

Thanks for the additional remarks. I was considering buying this RM551E module but it seems still has some serious bugs. Hopefully they address these bugs soon in firmware updates.

13

Dear @Tirkiz
We don’t have AT command to lock PCC.

14

Thank you.
I read somewhere on this forum that EU versions of modems have two radio tuners and GL versions only one radio tuner.
If that is true, it is possible that AT+QNWLOCK is applied to only one radio tuner and the second radio tuner adds the other cells to the CA and in this way on the old RG501Q-EU only the PCC lock works and it aggregates the other cells into the CA but on the RM551E-GL by locking one cell there is no CA.
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About upload speeds and upload CA
When I compare the old RG501Q-EU and the new RM551E-GL on the same external antennas (4x Iskra P-60, 12 dBi, 4x4 MIMO), the same base station and the same cells, I notice that this RM551E-GL only uses QPSK modulation in the upload.

Example on only one 20 MHz cell:
RG501Q-EU locked on only B3 20 MHz cell, without aggregation, with signal RSRP -76, RSRQ -6, RSSI -49, SINR 24 gives upload speed around 75-85 Mbps. This indicates that the old RG501Q uses max 64QAM modulation in the upload.

RM551E-GL locked to the same B3 20 MHz cell, without aggregation, with a signal of RSRP -78, RSRQ -8, RSSI -52, SINR 20 gives an upload speed of about 25 Mbps. This indicates that this RM551E uses low QPSK modulation.

Example of two aggregated cells B1+B3 or B3+B1 (20+20 MHz):
RG501Q-EU locked to only B1+B3 (20+20 MHz) gives an incredible upload speed of 165 Mbps. Obviously, it uses max 64QAM modulation on both aggregated cells.

RM551E-GL locked to the same B1+B3 cells (20+20 MHz) provides an upload speed of 70 Mbps, rarely maxing out at 100 Mbps. This suggests that it uses low QPSK and/or 16QAM modulation on both cells.

I know that the base station determines the upload modulation, but it is obvious that this RM551E has some problem or sends the base station worse signal parameters than they are, so it gets to use the lowest upload modulation.

1 Like
15

Do you test your modems on base stations that have a power saver that turns off MIMO on individual cells?

On cells EARFCN 1450 and 500, 1x1 SISO works all day, and this RM551E-GL reports it as a weaker signal by about 10 dB, which is not correct.

AT+QCAINFO
+QCAINFO: "PCC",1450,50,"LTE BAND 3",1,503,-93,-7,-65,5
+QCAINFO: "SCC",1300,100,"LTE BAND 3",1,503,-79,-7,-64,14,0,-,-
+QCAINFO: "SCC",500,100,"LTE BAND 1",2,503,-88,-8,-57,12,1,100,18500
+QCAINFO: "SCC",6300,50,"LTE BAND 20",1,503,-73,-9,-56,22,0,-,-

AT+QNWCFG="lte_mimo_info"
+QNWCFG: "lte_mimo_info",503,1450,1,1
+QNWCFG: "lte_mimo_info",503,1300,2,0
+QNWCFG: "lte_mimo_info",503,500,1,0
+QNWCFG: "lte_mimo_info",503,6300,2,0

When the cells are running MIMO (either 2x2 or 4x4) then the RSRP signal level is correct. All 4 antennas are connected (4x Iskra P-60, gain 12dBi, 4x4 MIMO).

You already fixed this issue with incorrect signal measurement on SISO cells with the old RG501Q-EU at the beginning of last year because I reported it and you released a new FW a few months later so I no longer have this issue with incorrect signal measurement on SISO cells. Now you have to fix the same on the new RM551E.

16

Dear @Tirkiz
On cells EARFCN 1450 and 500, 1x1 SISO works all day, and this RM551E-GL reports it as a weaker signal by about 10 dB, which is not correct.
=> Which parameter do you mentioned?

17

RSRP

RM551E does not correctly measure RSRP parameter on cells operating on 1x1 SISO (modem uses only one of four connected antennas).

In Croatia telecoms use power saver which turns off MIMO and cells remain on but only 1x1 SISO mode

18

Dear @Tirkiz
Sorry, from the response above, the value of RSRP is normal.

image
image891Ă—318 8.5 KB

19

I disagree, it is not normal that on a cell working on 1x1 SISO RM551E measures RSRP signal weaker up to 20 dB and the same band - compared to the old RG501Q which had the same problem and you fixed it at the beginning of last year.

And you fixed it because the old RG501Q had a habit of failing back to the 3G network when on 1x1 SISO RSRP was measured up to -120 dB even though the real RSRP is around -75 dB with external directional antennas that have clear optical visibility.

And the RM551E on the same antennas and in the same location measures RSRP signal weaker than the RG501Q.

I know that the 501Q is old but I don’t have a better modem to compare it to at the moment so I’m listing the 501Q in the comparison

image
image1234Ă—459 56.3 KB

20

Dear @Tirkiz
For these two modules, they used different PCC.