5G Tutorial

Following steps are performed during Initial Synchronisation: 1) Reading SSB block (PSS, SSS & MIB ). Determining PCI, Sub Frame number, SFN etc. 2) Reading SIB1 and finding RACH/PRACH information 3) RACH transmission and RAR reception. STEP 1: SSB Reading Synchronisation Block: SSB block takes 20 RBs . It is transmitted over 4 symbols.  Default periodicity is 20 ms. in one slot, maximum 2 SBs can be transmitted. Multiple SBs are transmitted as each SB corresponds to each beam. Maximum number of SB blocks varies depending on the frequency range.  For Freq < 3 GHz, Max SB Blocks = 4,  For 3< Freq < 6 GHz, Max SB Blocks = 8 For Freq > 6 GHz, Max SB Blocks = 64 SSB  block contains following signals PSS (Primary synchronisation signal) SSS (Secondary Synchronisation Signal) PBCH DMRS + PBCH  (MIB) PSS and SSS together is used to determine the physical cell ID which is 0-1008. PBCH DMRS provides SSB index as it is gener...

DMRS is demodulation reference signal that is required to decode PDSCH/PUSCH/PBCH data. Following are the parameters related to DMRS configuration DMRS is present in the same location where PDSCH is present/PUSCH/PBCH. for MIB decoding, PBCH DMRS position is mentioned in the post  "Intial Cell Selection" For SIB1, DMRS position is given in MIB message.  For all other cases, DMRS configuration comes either in RRCRewconfiguration or SIB1 message. Parameters related to DMRS : Mapping Type : Type A ==> Always start with Symbol 2 or 3 specified by parameter DMRS_TypeA_Pos in RRC configuration. In this case PDSCH starts from Symbol 0 in the slot. Type B ==> Starts with the first symbol of PDSCH allocated. In this case PDSCH must be starting from any symbol in the slot. Add_pos:  Multiple DMRS symbols can be present in the PDSCH. This is defined by the parameter DMRS_Add_Pos. It can be 1, 2 or 3 Following is the ...