5G RACH attempts failure issue in 5G n78 band Standalone

Hi,

in our testing 5G Standalone n78 band for SCS30 KHz and 100 MHz bandwidth used, One one single cell radiating only for testing

Get
MIB,SIB1, 5GS MM [5gNR] - Registration request,UL-CCCH [5gNR] - rrcSetupRequest are getting passed

after that getting failure message in RACH

NR5G MAC RACH Trigger	CONNECTION_REQUEST
NR5G MAC RACH Attempt	FAILURE_MSG2_RA_TIMER_EXP	
NR5G MAC RACH Attempt	FAILURE_MSG2_RAPID_MISMATCH	

What will be reason?

NR5G MAC RACH Attempt FAILURE_MSG2_RA_TIMER_EXP: this is because UE is under poor RF condition;check RSRP from Log.

In case there is good coverage ,then need to check UE software issue.

Hi,

CHecked with 2 mobile phone same issue observed

cell_quality_rsrp : -86.500000
cell_quality_rsrq : -10.507813
SINr: 15 to 20

how about link adaptation ,its enable?

whats model of both mobile

what is value of Maximum number of preamble transmission

PRACH
transmit_power : -6
pathloss : 67
mtpl : 23
rach_attempt : 2
min_power : -38

i am rx prach min power -38 dbm is that OK

PRACH power = Min{mtpl, *PRACH target power * + (rach_attempt – 1) × prach Power Ramp + pathloss}

PRACH power = Min{23, *PRACH target power * + (2 – 1) × prach Power Ramp + 67}

We assume that power Ramp =1

in above case min_power : -38 ========> PRACH target power -105 dbm

in your case UE send Prach preamble with less power .

can you check configuration of PRACH target power & prach Power Ramp & Maximum number of preamble transmission

<rach-ConfigCommon>
                <setup>
                  <rach-ConfigGeneric>
                    <prach-ConfigurationIndex>70</prach-ConfigurationIndex>
                    <msg1-FDM>
                      <one/>
                    </msg1-FDM>
                    <msg1-FrequencyStart>4</msg1-FrequencyStart>
                    <zeroCorrelationZoneConfig>7</zeroCorrelationZoneConfig>
                    <preambleReceivedTargetPower>-90</preambleReceivedTargetPower>
                    <preambleTransMax>
                      <n8/>
                    </preambleTransMax>
                    <powerRampingStep>
                      <dB6/>
                    </powerRampingStep>
                    <ra-ResponseWindow>
                      <sl8/>
                    </ra-ResponseWindow>
                  </rach-ConfigGeneric>
                  <ssb-perRACH-OccasionAndCB-PreamblesPerSSB>
                    <one>
                      <n64/>
                    </one>
                  </ssb-perRACH-OccasionAndCB-PreamblesPerSSB>
                  <groupBconfigured>
                    <ra-Msg3SizeGroupA>
                      <b56/>
                    </ra-Msg3SizeGroupA>
                    <messagePowerOffsetGroupB>
                      <dB0/>
                    </messagePowerOffsetGroupB>
                    <numberOfRA-PreamblesGroupA>48</numberOfRA-PreamblesGroupA>
                  </groupBconfigured>
                  <ra-ContentionResolutionTimer>
                    <sf40/>
                  </ra-ContentionResolutionTimer>
                  <prach-RootSequenceIndex>
                    <l139>129</l139>
                  </prach-RootSequenceIndex>
                  <msg1-SubcarrierSpacing>
                    <kHz30/>
                  </msg1-SubcarrierSpacing>
                  <restrictedSetConfig>
                    <unrestrictedSet/>
                  </restrictedSetConfig>
                </setup>
              </rach-ConfigCommon> 

prach_data
        resource_allocation : 4
        zc_root_seq : 67
        preamble_format : 5
        symbol_offset : 0
        numerology : 30KHZ (1)
        prach_number : 0
        zc_cyclic_shift : 91


3530	2021-12-14 13:23:12.059154	Qc. 5G-NR[Chipset]	______[0xB88A] NR5G MAC RACH Attempt	FAILURE_MSG2_RA_TIMER_EXP	
[ 2021  Dec  14    13:23:12.059154 ]  [0xB88A] NR5G MAC RACH Attempt  

Chipset timestamp: 2021-09-28 08:48:00.159348, CFN : 96
Dual Mode Index : 0
SIM Index : 1
Version : 131079
Major.Minor Version : 2.7
  log_fields_change
  log_fields_change_bmask : 0x0000
  sub_id : 0
  header
    num_records : 1
  num_attempt : 1
  ssb_id : 0
  csi_rs_id : 0
  carrier_id : 0
  rach_result : FAILURE_MSG2_RA_TIMER_EXP (1)
  contention_type : CONT_DL_MCE (1)
  rach_msg_bitmask : 0x01
      rach_msg1 (0x01)
    msg1_scs : 30KHz (3)
    ul_bwp_scs : 30KHz (1)
  rach_msg1
    system_time
      frame : 321
      sub_frame : 9
      slot : 1
      scs_value : 1
    symbol_start : 0
    prach_config : 70
    preamble_format : 5
    preamble_format : FORMAT_A1 (5)
    ra_id : 37
    fdm : 0
    uroot : 67
    cyclic_shift_v : 91
    ra_rnti : 267
    rar_window_start_sfn
      frame : 322
      sub_frame : 2
      slot : 0
      scs_value : 1
    rar_window_end_sfn
      frame : 322
      sub_frame : 6
      slot : 0
      scs_value : 1
    backoff_duration : 0

Wrong preamble detection check the clock source.