PRACH Tx power Check points

 In 5G when UE has to send RACH to initiate communication with gNodeB it has to evaluate the path loss in order to know with how much power UE has to transmit PRACH to compensate this path loss. 

How the UE calculate this? 

It is based on one measurement SSB-RSRP ( that is the SSB RSRP measured by UE in that specific location, in that specific moment in time) and 

Based on one information element ss-PBCH-BlockPower that is the SSB power transmitted by gNodeB ( located either in SIB1 in 5G SA or in RRC Connection reconfiguration in 5G NSA).

So, for example, if SSB_RSRP=-91 dBm and ss-PBCH-BlockPower=21dBm then 

UE will calculate pathloss PL=ss-PBCH-BlockPower-SSB_RSRP=21-(-91)= 112 dB. 

Now knowing this value of PL=112dB and knowing preambleReceivedTargetPower=-104dBm ( also located either in SIB1 in 5G SA or in RRC Connection reconfiguration in 5G NSA) 

UE will calculate what will be the P_PRACH power UE needs to transmit PRACH like this P_PRACH - PL = preambleReceivedTargetPower so P-PRACH-112dB=-104dBm so the P-PRACH=112-104=8 dBm in this example. 

Please keep in mind that even the if calculated power for PRACH would be higher than its max nominal power 23dBm, UE would not stop from sending RACH it will still transmit PRACH but limited to its maximum power that is 23dBm.

Comments

Post a Comment

Popular posts from this blog

NR MSG1 Analysis and Check points

Image
  NR MSG1 Detailed Analysis: FR2 +mmWave+120Khz Case: rach_ConfigGeneric {   prach_ConfigurationIndex == '10'   msg1_FDM == 'one'   msg1_FrequencyStart == '0'   zeroCorrelationZoneConfig == '0'   preambleReceivedTargetPower == '-74'   preambleTransMax == 'n100'   powerRampingStep == 'dB4'   ra_ResponseWindow == 'sl80' } totalNumberOfRA_Preambles == '63' totalNumberOfRA_Preambles == '10 ssb_perRACH_OccasionAndCB_PreamblesPerSSB  one  : 'n48' ra_ContentionResolutionTimer == 'sf64' prach_RootSequenceIndex :  l139 == '0' msg1_SubcarrierSpacing == 'kHz120' restrictedSetConfig == 'unrestrictedSet' As per Spec , Preamble Format A1, Starting symbol =0  and 38.211 v15.3.0- Table 6.3.3.2-4 : Random access configurations for FR2 and unpaired spectrum 38.211 -  Table 6.3.3.1-2: Preamble formats  for    and    where   ...
Read more

NR SA Paging Issue

Image
Paging Issue Check Points                          Some check points which will help you to analyze the root cause . Channel to Check :                     PCCH -> PCH -> PDSCH   Check points: RLC TM P-RNTI ->16bit (‭65534‬-> FFFE)-> Can be seen in PDCCH channel  Paging Message will go on DCI Format 1_0 always -> Can be seen in PDCCH channel DCI payload check (will update ASAP)  Timer T3513 5G-S-TMSI value from Registration Accept message ->fiveGGUTI-> last 6 Bytes  Spec 23.003  sec 2.11 PDCCH Transmission for paging can share the same search space as PDCCH transmission for SIB1 in case of Multiplexing pattern3->Can be seen in PDCCH channel  In SIB1 - > pagingSearchSpace == '0’  It mean that paging and SIB1 share the same search space Addition Information : Transmit Paging...
Read more

NR MIB

Case : UE Powered ON Cell Search (PSS and SSS) and PBCH decode to get MIB Decode and store the MIB -> we will focus more on MIB itself  check if cellBarred= barred,  stop here   cellBarred != barred, move to next to process further information Decode SIB1 using parameters provided by MIB and store the results As SIB1 indicate no demand SI, decode other System Information (SIBs) The MIB includes the system information transmitted on BCH(TE->UE).     -> RLC TM      -> BCCH -> BCH->PBCH      ->    the MIB is always transmitted on the BCH with a periodicity of 80 ms and repetitions made within 80 ms (TS 38.212 [17], clause 7.1) and it includes parameters that are needed to acquire SIB1 from the cell. The first transmission of the MIB is scheduled in subframes as defined in TS 38.213 [13], clause 4.1 and repetitions are scheduled according to the period of SSB ; As per Spec:38.331 MIB ::= ...
Read more