Why small n_prb values works worse then high values #1176

nikitos1550 · 2023-05-27T17:55:01Z

nikitos1550
May 27, 2023

Hi!

I am still trying make stable configuration for 4G base station using srsran.
My installation now is USP B210 (Chinese clone) and Zotac ZBOX M623 mini pc ( Intel(R) Core(TM) i3-10110U CPU @ 2.10GHz (4 cores) + 8GB RAM). B210 is powered via USB cable. 4 antennas are attached to B210 (looks like these https://cf.shopee.ph/file/7ab064cb5f5b95b48c47b959ecf57185 but some unknown from aliexpress, I checked them with NanoVNA and it seems ok for these used frequencies).
My B210 does not have GPSDO, but I ordered 10MHZ OCXO module from aliexpress, that can be installed to GPSDO slot (but it does not require GPS, I suppose it will be worse then normal GPSDO, but butter then now).
Ubuntu 23.04 and srsran 23.04 (last stable at the moment).

I somehow made proper simcard and it work stable.

First I used cell_search example to look what frequencies are already occupied and found free one.
I setuped dl_earfcn 1100 (DL=1980.0 Mhz, UL=1900.0 MHz), as I expect it should not interfere with existing base stations.
tx is 100db, rx is AGC or some value from 40 up to 80 (I did not see any difference at the moment).

Smartphone is located 3-5 meters away from B210.

When I setup n_prb 6, 15, 25 or even 50 I cannot get smartphone connection to b210, log is somewhat like this:

[CUT]
RACH:  tti=3551, cc=0, pci=1, preamble=8, offset=45, temp_crnti=0x13f
Disconnecting rnti=0x13b.
Disconnecting rnti=0x13c.
RACH:  tti=3571, cc=0, pci=1, preamble=15, offset=45, temp_crnti=0x140
Disconnecting rnti=0x13d.
RACH:  tti=3591, cc=0, pci=1, preamble=19, offset=45, temp_crnti=0x141
Disconnecting rnti=0x13e.
RACH:  tti=3611, cc=0, pci=1, preamble=26, offset=45, temp_crnti=0x142
Disconnecting rnti=0x13f.
RACH:  tti=3631, cc=0, pci=1, preamble=24, offset=45, temp_crnti=0x143
RACH:  tti=3651, cc=0, pci=1, preamble=28, offset=45, temp_crnti=0x144
Disconnecting rnti=0x140.
Disconnecting rnti=0x141.
RACH:  tti=3671, cc=0, pci=1, preamble=11, offset=45, temp_crnti=0x145
Disconnecting rnti=0x142.
Disconnecting rnti=0x143.
Disconnecting rnti=0x144.
Disconnecting rnti=0x145.
RACH:  tti=3821, cc=0, pci=1, preamble=17, offset=43, temp_crnti=0x146
RACH:  tti=3841, cc=0, pci=1, preamble=14, offset=43, temp_crnti=0x147
RACH:  tti=3861, cc=0, pci=1, preamble=39, offset=45, temp_crnti=0x148
RACH:  tti=3881, cc=0, pci=1, preamble=42, offset=45, temp_crnti=0x149
Disconnecting rnti=0x146.
RACH:  tti=3921, cc=0, pci=1, preamble=39, offset=45, temp_crnti=0x14a
Disconnecting rnti=0x147.
Disconnecting rnti=0x148.
RACH:  tti=3941, cc=0, pci=1, preamble=17, offset=45, temp_crnti=0x14b
Disconnecting rnti=0x149.
RACH:  tti=3961, cc=0, pci=1, preamble=16, offset=45, temp_crnti=0x14c
lte    1  14a  n/a   0    0      0    0    0   0% |   0.4    n/a    0    0      0    0    4 100%    0.0
lte    1  14b  n/a   0    0      0    0    0   0% |   0.2    n/a    0    0      0    0    4 100%    0.0
lte    1  14c  n/a   0    0      0    0    0   0% |   0.4    n/a    0    0      0    0    2 100%    0.0
RACH:  tti=3981, cc=0, pci=1, preamble=26, offset=45, temp_crnti=0x14d
Disconnecting rnti=0x14a.
RACH:  tti=4001, cc=0, pci=1, preamble=49, offset=45, temp_crnti=0x14e
RACH:  tti=4021, cc=0, pci=1, preamble=28, offset=43, temp_crnti=0x14f
Disconnecting rnti=0x14b.
Disconnecting rnti=0x14c.
Disconnecting rnti=0x14d.
Disconnecting rnti=0x14e.
Disconnecting rnti=0x14f.
[CUT]

With n_prb 100 (75 is not working with mine b210, something about freq is not consistent, I didn't dig deep)

uilt in Release mode using 23.04.0.

/home/lte/srsRAN_4G-release_23_04/srsenb/src/enb_cfg_parser.cc:1881: Force DL EARFCN for cell PCI=1 to 1100
Opening 2 channels in RF device=default with args=num_recv_frames=64,num_send_frames=64
Supported RF device list: UHD file
Trying to open RF device 'UHD'
[INFO] [UHD] linux; GNU C++ version 12.2.0; Boost_107400; DPDK_22.11; UHD_4.3.0.0+ds1-4build2
[INFO] [LOGGING] Fastpath logging disabled at runtime.
Opening USRP channels=2, args: num_recv_frames=64,num_send_frames=64,type=b200,master_clock_rate=23.04e6
[INFO] [UHD RF] RF UHD Generic instance constructed
[INFO] [B200] Detected Device: B210
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test... 
[INFO] [B200] Register loopback test passed
[INFO] [B200] Performing register loopback test... 
[INFO] [B200] Register loopback test passed
[INFO] [B200] Asking for clock rate 23.040000 MHz... 
[INFO] [B200] Actually got clock rate 23.040000 MHz.
[INFO] [MULTI_USRP]     1) catch time transition at pps edge
[INFO] [MULTI_USRP]     2) set times next pps (synchronously)
RF device 'UHD' successfully opened

==== eNodeB started ===
Type <t> to view trace
Setting frequency: DL=1980.0 Mhz, UL=1900.0 MHz for cc_idx=0 nof_prb=100
t
Enter t to stop trace.
RACH:  tti=7651, cc=0, pci=1, preamble=33, offset=0, temp_crnti=0x46

               -----------------DL----------------|-------------------------UL-------------------------
rat  pci rnti  cqi  ri  mcs  brate   ok  nok  (%) | pusch  pucch  phr  mcs  brate   ok  nok  (%)    bsr
lte    1   46   15   0    2   1.8k    8    0   0% |  10.2   13.0   32    4    23k    6    1  14%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0

               -----------------DL----------------|-------------------------UL-------------------------
rat  pci rnti  cqi  ri  mcs  brate   ok  nok  (%) | pusch  pucch  phr  mcs  brate   ok  nok  (%)    bsr
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
lte    1   46   15   0    0      0    0    0   0% |   n/a   10.0    0    0      0    0    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   46   11   0    0      0    0    3 100% |   n/a    1.9    0    0      0    0    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0

               -----------------DL----------------|-------------------------UL-------------------------
rat  pci rnti  cqi  ri  mcs  brate   ok  nok  (%) | pusch  pucch  phr  mcs  brate   ok  nok  (%)    bsr
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   46    1   0    0      0    0    0   0% |   n/a   -1.7    0    0      0    0    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   46    6   0    0      0    0    3 100% |   n/a    0.7    0    0      0    0    0   0%    0.0
RACH:  tti=3421, cc=0, pci=1, preamble=1, offset=0, temp_crnti=0x47
User 0x47 connected
lte    1   46   14   0    0      0    0    3 100% |   n/a    0.8    0    0      0    0    0   0%    0.0
lte    1   47   15   0    3   6.1k   10    4  28% |   6.7    6.1   33    1   128k   14    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   47   14   1    1    800    3    0   0% |   5.8    6.6   34    2    17k    4    0   0%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   47   15   1    0      0    0    0   0% |   2.6    5.9   34    2    17k    4    4  50%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   47   15   1    0      0    0    0   0% |   5.3    5.7   34    2   8.5k    2    0   0%    0.0
Disconnecting rnti=0x47.
lte    1   46    5   0    0      0    0    6 100% |   n/a    0.2    0    0      0    0    0   0%    0.0
RACH:  tti=7951, cc=0, pci=1, preamble=35, offset=0, temp_crnti=0x48
User 0x48 connected
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   48   15   1    2   1.5k    7    0   0% |   7.4    7.0   33    2    57k   15    1   6%    0.0
lte    1   46  n/a   0    0      0    0    0   0% |   n/a    n/a    0    0      0    0    0   0%    0.0
lte    1   48   15   1    0      0    0    0   0% |   n/a   99.9    0    0      0    0    0   0%    0.0
[CUT]

And I still cannot get net connection on smartphone, srsepc log is

[CUT]
Sending EMM Information
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
Received UE Context Release Request. MME-UE S1AP Id 20
There are active E-RABs, send release access bearers request
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_RELEASE_ACCESS_BEARERS_REQUEST
Received UE Context Release Complete. MME-UE S1AP Id 20
UE Context Release Completed.
Initial UE message: NAS Message Type Unknown
Received Initial UE message -- Service Request
Service request -- S-TMSI 0xa8c03d8
Service request -- eNB UE S1AP Id 9
Service Request -- Short MAC valid
Service Request -- User is ECM DISCONNECTED
UE previously assigned IP: 172.16.0.3
Generating KeNB with UL NAS COUNT: 8
UE Ctr TEID 0
Sent Initial Context Setup Request. E-RAB id 5 
Received Initial Context Setup Response
E-RAB Context Setup. E-RAB id 5
E-RAB Context -- eNB TEID 0x8; eNB GTP-U Address 127.0.1.1
Initial Context Setup Response triggered from Service Request.
Sending Modify Bearer Request.
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_MODIFY_BEARER_REQUEST
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
[CUT]

Last messages I cannot understand.

Before I had successful connection and used internet via this configuration from smartphone, as I remember with n_prb 25 (or 50), but I cannot reproduce this anymore. This makes me think that something is not stable or I am no taking into account something important.

I need some advices or comments on these.

nikitos1550 · 2023-05-27T18:11:07Z

nikitos1550
May 27, 2023
Author

I found the reason for no net connection, when it seems it should be, i just installed docker into my system and it affected the net configuration, after docker service disable it becomes ok.

Still can see this

UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject

What does it mean?

But I still cannot get connection with n_prb less then 100 :-(

P.S.
disabling 2 channels use make me able to get not stable, but some connection with n_prb <= 50

tm = 4
nof_ports = 2

I can think that the problem is in RF area, but I have no idea how to debug it.

0 replies

brendan-mcauliffe · 2023-06-08T10:35:10Z

brendan-mcauliffe
Jun 8, 2023
Collaborator

Hi @nikitos1550,

Can you try this set-up again, but using the base configuration shown in the app note found here. Change the frequencies as you need, but try to leave the rest as is.

While testing the set-up with this, set your logs to info mode. If you can then share those here it will be easier to give you some guidance on what might be going wrong.

I also suggest you run the following command to make sure that your PC is running in performance mode:
echo "performance" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

1 reply

nikitos1550 Jun 9, 2023
Author

Yes, I will try. I also got external GPSDO, will try with and without it.

Provide feedback

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Why small n_prb values works worse then high values #1176

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Why small n_prb values works worse then high values #1176

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