LTE: Why eNodeB scramble MIB information with antenna specific mask before broadcasting over the air ?

Question

At the high level I understand LTE nodes and signalling but want to learn in depth. I read one statement saying " MIB information is scrambled with antenna specific mask". Now I want to understand if an eNodeB supports multiple antennas (saying two antennas) , known as MIMO, then in that case, does an eNodeB sends MIB information into two different frequency spaces ? MIB is transmitted into subframe #0 of each radio frame.
Now I have doubt when we say MIB is scrambled with antenna specific mask before broadcasting and only middle 6 RBs are used to braodcast MIB, then in case of MIMO where multiple antennas are being used to send MIBs. Shall MIB from both the antennas overlap due to same 6 RBs or the same 6 RBs can be used to broadcast MIBs from both the antennas ?

Answer 1

Hi rupam,

Its very simple, If MIMO case ENB will have 3 different kind of antenna mask to send MIB. To send MIB ENB will use tranmit diversity as trasnmission mode. so there is no problem in decoding side. UE will try to decode these three sequence scrambled MIB to find the antenna info. Each sequence will have its specific antenna info, For e.g two antenna case ENB will use Space-Frequency Block Coding to scramble the MIB. UE will try all three sequence and find the antenna info.