How to calculate Transmit Diversity Gain in LTE?

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

Credit: http://www.teletopix.org/4g-lte/transmit-diversity-gain-in-lte/

Transmit diversity gain can be used when transmitting broadcast information from multiple antennas. This effectively produces, by design, frequency diversity in the transmitter. The gain obtained from transmit diversity can be approximated with the following equation.

GCC = 10× log(NTx)

Where NTx is the number of transmit antennas.

Thus, a BS that has 2 transmit antennas and transmit diversity will have 3 dB of improvement in its EIRP versus a BS without transmit diversity.

Typically, only the BS uses multiple transmit antennas and will benefit from the transmit diversity. The subscriber device using a single transmit antenna would not have this benefit.

Comments

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