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.