build 4G 20MHz in Rpi 5

[faratell]

I have been using the Raspberry Pi 5 to run the srsRAN eNodeB. It works fine with a bandwidth of 15 MHz, but when I switch to a bandwidth of 20 MHz, it connects initially but then disconnects after a few seconds due to an underflow issue.

sudo ./srsenb /root/.config/srsran/enb.conf
Active RF plugins: libsrsran_rf_uhd.so
Inactive RF plugins:
--- Software Radio Systems LTE eNodeB ---

Reading configuration file /root/.config/srsran/enb.conf...

Built in Release mode using commit ec29b0c1f on branch master.

Opening 1 channels in RF device=UHD with args=default
Supported RF device list: UHD file
[INFO] [UHD] linux; GNU C++ version 12.2.0; Boost_107400; UHD_4.3.0.0+ds1-5
[INFO] [LOGGING] Fastpath logging disabled at runtime.
Opening USRP channels=1, args: 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] Detecting internal GPSDO....
[INFO] [GPS] Found an internal GPSDO: GPSTCXO, Firmware Rev 0.929b
[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.

==== eNodeB started ===
Type to view trace
Setting frequency: DL=1850.0 Mhz, UL=1755.0 MHz for cc_idx=0 nof_prb=100
t
Enter t to stop trace.
RACH: tti=9371, cc=0, pci=1, preamble=29, offset=1, 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 11 0 2 1.1k 2 0 0% | 43.0 34.8 23 0 8.3k 2 0 0% 0.0
lte 1 46 10 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 8 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 8 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 8 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 8 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 8 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 9 0 3 560 2 0 0% | 37.1 36.8 32 22 8.3k 2 0 0% 0.0
lte 1 46 9 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 9 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 8 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 8 0 2 560 2 0 0% | 37.7 36.4 31 22 4.1k 1 0 0% 0.0
lte 1 46 8 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 9 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 8 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 9 0 0 0 0 0 0% | n/a 99.9 0 0 0 0 0 0% 0.0
lte 1 46 9 0 6 0 0 16 100% | n/a -0.6 0 0 0 0 0 0% 0.0
lte 1 46 14 0 0 0 0 0 0% | n/a 1.2 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 12 0 0 0 0 0 0% | n/a -0.2 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 14 0 0 0 0 0 0% | n/a 0.3 0 0 0 0 0 0% 0.0
Disconnecting rnti=0x46.
RF status: O=0, U=1, L=12

i set CPU frequency to performance mode and tried to install RT /low latency kernel. it installed correctly but not enabled:

dpkg --list | grep linux-image
ii linux-image-6.1.0-30-rt-arm64 6.1.124-1 arm64 Linux 6.1 for 64-bit ARMv8 machines, PREEMPT_RT (signed)
ii linux-image-6.6.51+rpt-rpi-v8 1:6.6.51-1+rpt3 arm64 Linux 6.6 for Raspberry Pi v8, Raspberry Pi
ii linux-image-6.6.62+rpt-rpi-2712 1:6.6.62-1+rpt1 arm64 Linux 6.6 for Raspberry Pi 2712, Raspberry Pi
ii linux-image-6.6.62+rpt-rpi-v8 1:6.6.62-1+rpt1 arm64 Linux 6.6 for Raspberry Pi v8, Raspberry Pi
ii linux-image-rpi-2712 1:6.6.62-1+rpt1 arm64 Linux for Raspberry Pi 2712 (meta-package)
ii linux-image-rpi-v8 1:6.6.62-1+rpt1 arm64 Linux for Raspberry Pi v8 (meta-package)
ii linux-image-rt-arm64 6.1.124-1 arm64 Linux for 64-bit ARMv8 machines (meta-package)

but : uname -a
Linux faraz 6.6.74-v8-16k+ #1 SMP PREhoEMPT Sat Feb 1 11:29:48 +0330 2025 aarch64 GNU/Linux