Connecting phone to srsran_4G_eNB with TM4 mode

[Azzedine-Touazi]

Hi there,

I'm running srseNB (release 23.04) on intel I9 machine with Ubuntu 22.04 using USRP B210 and GPSDO ref clock. The RACH procedure was successfully completed with eNB SISO TM1 mode with different phones (Samsung, Google pixel...). However, when trying with srseNB TM4 2x2 MIMO setup (by setting tm = 4 and nof_ports = 2), I got Msg3_CRC=KO with low SNR (Msg3 not received by eNB or maybe RAR not received by phone). Please see srseNB log below.

Is there any other parameter or special setup that needs to be considered in TM4 setup (e.g., antennas positioning, antennas type, time_adv…)?

Thank you!

[RLC ] [I] Added LTE radio bearer with LCID 0 in Transparent Mode
[RRC ] [I] Added new user rnti=0x46
[MAC ] [I] [ 4421] SCHED: New PRACH tti=4421, preamble=1, temp_crnti=0x46, ta_cmd=7, msg3_size=7
[MAC ] [I] [ 4421] RACH: tti=4421, cc=0, pci=2, preamble=1, offset=7, temp_crnti=0x46
[MAC ] [I] [ 4421] rach_tprof: {mean, max, min}={129.5, 129, 129} usec, nof_samples=1
[MAC ] [I] [ 4422] SCHED: RAR, ra-rnti=2, rbgs=[0, 1), dci=(2,0), msg3 grants=[{c-rnti=0x46, rba=51, mcs=0}]
[PHY2 ] [I] [ 4422] PDCCH: cc=0, rnti=0x2, f=1A, cce= 0, L=2, riv=25, pid=0, mcs={1}, ndi={0}, tpc_pucch=0, tti_tx_dl=4426
[PHY2 ] [I] [ 4422] PDSCH: cc=0, rnti=0x2, nof_prb=2, nof_re=240, tbs={11}, mod={2}, rv={0}, tx=div, nof_tb=1, nof_l=2, tti_tx_dl=4426
[MAC ] [I] [ 4424] SCHED: Msg3 tx rnti=0x46, cc=0, pid=0, dci=(0,0), prb=[1, 4), n_rtx=0, cfi=1, tbs=7, bsr=0 (0-7), tti_tx_ul=4432
[MAC ] [I] [ 4432] SCHED: UL adaptive link: rnti=0x46, snr_estim=5.00, last_mcs=0, snr_offset=0.000000
[PHY0 ] [I] [ 4432] PUSCH: cc=0, rnti=0x46, rb=(1,3), nof_re=432, tbs=7, mod=2, rv=0, crc=KO, avg_iter=8.0, snr=-0.4 dB, epre=-21.1 dBfs, ta=-6.4 us, cfo=-132.0 hz, t=21 us
[MAC ] [I] [ 4432] SCHED: Msg3 retx rnti=0x46, cc=0, pid=0, dci=(0,0), prb=[1, 4), n_rtx=1, cfi=1, tbs=7, bsr=0 (0-7), tti_tx_ul=4440
[PHY0 ] [I] [ 4432] PHICH: rnti=0x46, hi=0, I_lowest=1, n_dmrs=0, tti_tx_dl=4436
[MAC ] [I] [ 4440] SCHED: UL adaptive link: rnti=0x46, snr_estim=5.00, last_mcs=0, snr_offset=0.000000