5G-NR: MIB (Master information block)-
Introduction:
When the UE switches on, it starts listening to the SSB(PSS/SSS/PBCH) for time and frequency synchronization with a cell and to detect Physical layer Cell ID (PCI) of the cell and tried to get the system information. After the successful cell setup gNB always broadcasting the MIB On SSBs occasions. MIB is the part on SSB.
PBCH carries system information, such as Master Information Block, SSB Index.
MIB:
MIB (Master information block) includes the system information and always transmitted on the BCH from network to UE with a periodicity of 80 ms and
repetitions made within 80 ms.
it also includes the parameters that are needed to acquire/decode the SIB1 from the cell.
The first transmission of the MIB is scheduled in subframes defined by [TS 38.211,
7.4.3.2] and repetitions are scheduled according to the period of SSB;
It uses QPSK modulation for transmission from the network to UE It is transmitted on OFDM symbol 1,2,3.
RRC parameters of MIB:
NR PBCH under SSB:
MIB
::= SEQUENCE {
Description if parameters:
systemFrameNumber:The 6 most significant bit (MSB) of the 10-bit System Frame Number. The 4 LSB of the SFN is conveyed in the PBCH transport block as part of channel coding (i.e. outside the MIB encoding).
subCarrierSpacingCommon
Subcarrier spacing for SIB1, Msg.2/4 for initial access and broadcast SI-messages. If the UE acquires this MIB on a carrier frequency <6GHz, the value scs15or60 corresponds to 15 Khz and the value scs30or120 corresponds to 30 kHz. If the UE acquires this MIB on a carrier frequency >6GHz, the value scs15or60 corresponds to 60 Khz and the value scs30or120 corresponds to 120 kHz.
scs15or60 | scs30or120 | |
| FR1 | 15 Khz | 30 Khz |
| FR2 | 60 Khz | 120 Khz |
ssb-SubcarrierOffset
Corresponds to kSSB (see TS 38.213 [13]), which is the frequency domain offset between SSB and the overall resource block grid in the number of subcarriers. (See 38.211).
The value range of this field maybe extended by an additional most significant bit encoded within PBCH as specified in 38.213 [13].
This field may indicate that this beam does not provide SIB1 and that there is hence no common CORESET (see TS 38.213 [13], section 13). 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 SIB1 (see 38.213 [13], section 13)
dmrs-TypeA-Position
Position of (first) DM-RS for in downlink (see 38.211, section 7.4.1.1.1) and in uplink (see 38.211, section 6.4.1.1.3).
cellBarred indicates whether the cell allows UEs to camp on this cell as per specification TS 38.304
intraFreqReselection indicates 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 treated as barred by the UE as specified in TS 38.304
The call flow of MIB and SIB:
NR and LTE comparison:
Parameters
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Long Term Evolution (LTE)
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New Radio (NR)
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Broadcast Channel
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Transport – BCH
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Transport – BCH
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Physical- PBCH
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Physical- PBCH
|
|
Periodicity
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40 ms periodicity with 10 ms re-transmission
periodicity
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80 ms periodicity with
repetitions made within 80 ms
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Channel Coding
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Tail Bit Convolution encoding
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Polar Coding
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Modulation
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QPSK
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QPSK
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Resource Allocation
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6 RBs (72 subcarriers) in Frequency domain
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It is transmitted on OFDM symbol 1,2,3.
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4 symbols of first subframe second slot symbol 0,
1, 2 and 3.
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It uses 0 to 239 subcarriers number on symbol 1
& 3, whereas on symbol 2 it uses sub carried number 0 to 47 and 192 to
239
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