What are the transmission mode enb sends to UE in RRC connection setup and rrc connection reconfiguration?

Question

why eNB sends rrc reconfiguration to connected UE when we add or modify inter frequency for SIB5 on eNB
As i understand, UE reads SIB5 after reading paging in idle mode. Why RRC reconfig is required at this time ?

Answer 1

Transmit diversity is by default Transmission mode in RRC connection setup. It may or may not change in Reconfiguration to TM3 or TM4 based different transmission mode satisfied conditions.

Comments

@Suchakravarthi Sripathi plz share  some details about TM3 OR TM4.

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Agreed with but there is also another scenario
UE can detect eNB Antenna configuration right after power on and before dedicated channel establish (before RRC Connection Setup or before RRC Channel Reconfiguration) by during PBCH decoding.
PBCH carry the information about the antenna configuration (the number of Antenna ports being used for a cell). But if you look at the MIB message itself you wouldn't see any information elements about the number of antenna ports. Then how the PBCH can carry the antenna configuration in it ?

It is done by using special CRC mask (the number of bit stream being masked(XORed) over the CRC bits. Number of CRC bits for PBCH is 16 bits, so the length of the CRC mask is 16 bit as well. Following tables shows the types of CRC mask representing each of the antenna configurations.
You can refer 36.212 Table 5.3.1.1-1.
Thanks,
Sambit Routray

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Agree with you.
UE can detect eNB Antenna configuration right after power on and before dedicated channel establish (before RRC Connection Setup or before RRC Channel Reconfiguration) by during PBCH decoding.
PBCH carry the information about the antenna configuration (the number of Antenna ports being used for a cell). But if you look at the MIB message itself you wouldn't see any information elements about the number of antenna ports. Then how the PBCH can carry the antenna configuration in it ?

It is done by using special CRC mask (the number of bit stream being masked(XORed) over the CRC bits. Number of CRC bits for PBCH is 16 bits, so the length of the CRC mask is 16 bit as well. Following tables shows the types of CRC mask representing each of the antenna configurations.
You can refer to 36.212 Table 5.3.1.1-1 : CRC mask for PBCH
Thanks
Sambit Routray