5G原理和协议重点解读英文版.docx

1、5G原理和协议重点解读英文版5G Master Information Block (NR-MIB)Over all structure of MIB and SIB in NR is almost similar to LTE and other legacy technologies. However there is a major difference related to the periodical transmission of SIBs. In LTE and other legacy technologies the SIBs are broadcasted priodica

2、lly regardless of whether UE wants it or not. But, in New Radio (NR) there are two versions of SIBs. One is being transmitted periodically like LTE and other is being transmitted only on-Demand i.e. when requested by UE.NR MIB characteristicsMIB is transmitted over BCH transport channel and PBCH phy

3、sical channelIt is QPSK modulatedIt included the necessary parameters required to decode SystemInformationBlockType1 (SIB1)Its priodicity is about 80 ms and with in this 80 ms repetitive transmission happensIt is transmitted on OFDM symbol 1,2,3 .It uses 0 to 239 sub carrier number on symbol 1 & 3,

4、where as on symbol 2 it uses subcarried number 0 to 47 and 192 to 239 as per TS 38.211.MIB/SIB signalling call flow:Signalling radio bearer: N/ARLC-SAP: TMLogical channel: BCCHDirection: Network to UERRC Parameters for Master Information Block:MIB := SEQUENCE systemFrameNumber BIT STRING (SIZE (6),s

5、ubCarrierSpacingCommon ENUMERATED scs15or60, scs30or120,ssb-SubcarrierOffset INTEGER (015),dmrs-TypeA-Position ENUMERATED pos2, pos3,pdcch-ConfigSIB1 INTEGER (0255),cellBarred ENUMERATED barred, notBarred,intraFreqReselection ENUMERATED allowed, notAllowed,spare BIT STRING (SIZE (1)Parameters Descri

6、ption:systemFrameNumber: Similar to LTE, NR does have a 10 bit System Frame Number start from 0 to 1023. MIB carries 6 most significant bit (MSB) of the 10 bits and remaining 4 LSB of the SFN are conveyed in the PBCH transport block as part of channel coding (i.e. outside the MIB encoding).subCarrie

7、rSpacingCommon: Indicates the Subcarrier spacing for SIB1, Message 2/4 for initial access and System Information-messages. It can have a values 15 and 30 kHz valid for carrier frequencies 6GHzssb-subcarrierOffsetindicates the frequency domain offset between SSB and the overall resource block grid in

8、 number of subcarriers. This field may indicate that this cell does not provide SIB1 and that there is hence no common CORESET. In this case, the field pdcch-ConfigSIB1 may indicate the frequency positions where the UE may (not) find a SS/PBCH with a control resource set and search space for SIB1dmr

9、s-TypeA-Position: Indicates Position of (first) DL DM-RS. It corresponds to L1 parameter DL-DMRS-typeA-pospdcchConfigSIB1: It is corresponds to RMSI-PDCCH-Config in TS 38.213 13, section 4.1. Determines a bandwidth for PDCCH/SIB, a common ControlResourceSet (CORESET) a common search space and necess

10、ary PDCCH parameters. If the field ssb-SubcarrierOffset indicates that SIB1 is not present, the field pdcch-ConfigSIB1 indicate the frequency positions where the UE may find SS/PBCH block with SIB1 or the frequency range where the network does not provide SS/PBCH block with SIB1 (see TS 38.213 13, s

11、ection 13).cellBarredindicates whether the cell allows UEs to camp on this cell as per specification TS 38.304intraFreqReselectionindicates if Intra frequency cell reselection is Allowed or notAllowed. It controls cell reselection to intra-frequency cells when the highest ranked cell is barred, or t

12、reated as barred by the UE as specified in TS 38.304MIB Acquiringand ProcessingMIB / SIB acquisition process vary case to case. Here we will dicsuss overall MIB/SIB acquisition process as defined in TS 38.331 NR-RRC specification.Case 1 : No On-Demand System Information, No previously stored SIB and

13、 UE just powered ONUE Powered ONCell Search (PSS and SSS) and PBCH decode to get MIBDecode and store the MIBcheck if cellBarred= barred, stop here cellBarred != barred, move to next to process further informationDecode SIB1 using parameters provided by MIB and store the resultsAs SIB1 indicate no de

14、mand SI, decode other System Information (SIBs)Case 2 : On-Demand System Information Indication, No previously stored SIB and UE just powered ONUE Powered ONCell Search (PSS and SSS) and PBCH decode to get MIBDecode and store the MIBcheck if cellBarred= barred, stop here cellBarred != barred, move to next to process further informationDecode SIB1 using parameters provided by MIB and store the resultsAs SIB1 indicate on demand SI, check RRC statusIf UE RRC status is in RRC-IDLE or RRC-INACTIVE stateTrigger UE lower layers to initate RACH procedureAcquire the on-Demand SI messages when Ackn