Master Information Block : MIB in LTE

Direction :  E-UTRAN to UE 

Channel Mapping : (BCCH->BCH->PBCH)

The MIB is carried on the Broadcast Channel (BCH) mapped into the Physical Broadcast Channel (PBCH). This is transmitted with a fixed coding and modulation scheme and can be decoded after the initial cell search procedure.

Question comes from above statement in every step and we will try to find out the exact meaning of step, when UE read MIB? Why its need? And what will happen after that?

·         Prior to decoding the MIB, the UE does not know the full system bandwidth. The primary and secondary synchronization signals (PSS and SSS) and the PBCH (containing the MIB) all lie in the central 72 subcarriers (6 resource blocks) of the system bandwidth, Network allowed the UE to initially demodulate just this central region. Therefore the bandwidth is initially set to 6 resource blocks.

·         At this stage User Equipment (UE) can communicate with the network it must perform cell search and selection procedures and obtain initial system information. This involves acquiring slot and frame synchronization, finding out the cell identity and decoding the Master Information Block (MIB) and the System Information Blocks (SIBs).

• The MIB is transmitted on physical channel (BCCH->BCH->PBCH).The first transmission of the MIB is scheduled in sub-frame number 0 of radio frames for which the SFN mod 4 = 0
• Repetitions are scheduled in sub-frame 0 of all other radio frames
• In order to communicate with the network the UE must obtain some basic system information.This is carried by the MIB and SIBs. The MIB carries the most essential system information
• System bandwidth
• System Frame Number (SFN)
• Physical Hybrid Automatic Repeat Request (HARQ) Indicator Channel (PHICH) Configuration
• MasterInformationBlock::= SEQUENCE {
  dl-Bandwidth ENUMERATED { n6, n15, n25, n50, n75, n100}, 
  phich-Config PHICH-Config, 
  systemFrameNumber BIT STRING (SIZE (8)), 
  spare BIT STRING (SIZE (10))
  }

MasterInformationBlock{

      dl_Bandwidth = n100

      Phich-Config {

         phich_Duration = normal

         phich_Resource = one Sixth

      }

      SystemFrameNumber = {8, 0x00}

      Spare = {10, 0x00 00xxxxxx}

   }