[solved] em7565 256qam dl

IoT Modules MC/EM Series
1

When will we get 256QAM DL support for all mobile carriers? Why is 64QAM UL supported but 256QAM DL not?

Thank you in advance.

2

EM7565 supports 256QAM in DL, it is in the PTS.
It is up to the carriers to support 256QAM.

3

My carrier supports 256QAM and it works with other modems. This modem most certainly has a carrier whitelist for 256QAM DL.

4

How do you actually know it is not 256QAM?
How much DL data you are pushing?

I’m getting 256QAM on the callbox
LTE LL1 PDSCH Demapper Configuration
…
Transport Block Size Stream 0 = 71112 bits
Modulation Stream 0 = 256QAM

also check your signal strength with at!gstatus?

5

I am hitting exactly the limits of 64QAM for 2x15 MHz (~ 223 - 224 Mbit/s). My mobile phone gets higher speeds with the same SIM card (Galaxy S8). The Galaxy S8 (EMEA) didn’t support 256QAM in Europe either until they released a new modem firmware with Android Oreo.

My signal strength is good enough for 256QAM.

PCC RxM RSSI:  -56              PCC RxM RSRP:  -77
PCC RxD RSSI:  -62              PCC RxD RSRP:  -83
SCC1 RxM RSSI: -64              SCC1 RxM RSRP: -82
SCC1 RxD RSSI: -59              SCC1 RxD RSRP: -77
Tx Power:      -10              TAC:         ... (...)
RSRQ (dB):     -7.5             Cell ID:     ... (...)
SINR (dB):     29.8

This modem has other issues as well and Sierra doesn’t seem to care at all. EM7565 Firmware Problems with CA?

Edit: I asked my carrier whether they have a whitelist for 256QAM. The answer was a clear no.

6

Yes you signal is looking pretty good.
Let’s discuss the 256QAM issue first.

Can you tell me about your platform?
Is it Linux? PC or embedded SOC?
What drivers do you use?
How do you connect the EM7565 to your platform? Are you using a Sierra EM7565 Devkit?
Did you verify the USB version on the host side? (v3.0) lsusb -v
How do you measure throughput?

7

Arch Linux.

It’s an SBC. ODROID XU4 with USB 3.0.

Linux’ cdc_wdm, qmi_wwan and qcserial.

Yes, of course.

[root@odroid-xu4 ~]# lsusb -t 
/:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
    |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=r8152, 5000M
/:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/2p, 5000M
        |__ Port 1: Dev 3, If 0, Class=Hub, Driver=hub/4p, 5000M
            |__ Port 1: Dev 10, If 8, Class=Vendor Specific Class, Driver=qmi_wwan, 5000M
            |__ Port 1: Dev 10, If 2, Class=Vendor Specific Class, Driver=qcserial, 5000M
            |__ Port 1: Dev 10, If 0, Class=Vendor Specific Class, Driver=qcserial, 5000M
            |__ Port 1: Dev 10, If 3, Class=Vendor Specific Class, Driver=qcserial, 5000M
            |__ Port 2: Dev 4, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
            |__ Port 3: Dev 5, If 0, Class=Hub, Driver=hub/4p, 5000M
                |__ Port 4: Dev 7, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
                |__ Port 1: Dev 6, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/2p, 480M
        |__ Port 1: Dev 3, If 0, Class=Hub, Driver=hub/4p, 480M
            |__ Port 3: Dev 4, If 0, Class=Hub, Driver=hub/4p, 480M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=exynos-ohci/3p, 12M
    |__ Port 1: Dev 25, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=exynos-ehci/3p, 480M

By downloading a big file, i.e. http://bck-speedtest-1.tele2.net/ or Debian images via Torrent.

The tool I am using for measurement is vnstat. i.e.: vnstat -l -i wwan0.

8

We (Sierra) are regularly running throughput test internally (2CA and 3CA ) with a callbox and we are hitting near theoretical max in simultaneous UL and DL directions.
With 2 CA the theoretical max is 400Mbps in DL. (3CA 600Mbps)
Do you have access to 3CA in your area or only 2CA?
How about bandwidth?
223Mbps (out of 400Mbps) is pretty good on the live NTWK. How much are you expecting?
You should not be expecting the theorethical max on a live NTWK because you will not be only one attached to the cell.

9

Maybe you are right and 256QAM is already functioning. Is there an SDK or AT command to see whether 256QAM is active or not?

I think the maximum throughput for 2x15 MHz is about 300 Mbit/s and not 400 Mbit/s.

W020110117526868252994.jpg1486×628 133 KB

110*2 = 220 + 30% (256QAM) = 286 Mbit/s

Anyway, the stream issue discussed in the other thread would be more important. It’s kind of a dealbreaker. I can only get all four streams (2CA) working by causing a hand over.

10

@unknown

No there is no way to see what modulation scheme is being used, you can only see this through the DM port using Qualcomm tools since it can change very quickly.

Regards

Matt

11

I read the other thread ,but the issue description is too confusing.
What is the issue again with CA?
Please note where there is no data to be sent SCCx will be torn down to save radio resources.

Maybe open a new issue and provide a detailed problem description and logs.

12

I have reached 232 Mbit/s once (out of ~286), so I guess 256QAM is active. But the other problem is still a huge dealbreaker.