These are all complex technologies, in brief:
STBC = Space Time Block Encoding - Used to spread copies of a single data stream across multiple (2 or more) antennas to improve the reliability of data transfer.
LDPC = Low Density Parity Check - is a forward error correction encoding scheme, the idea being to correct single bit errors and improve SNR.
TxBF = Transmit beamforming Allows the antenna to adjust the phase and amplitude in such away that MIMO is utilised and allows a signal to arrive at a receiver in phase, therefore using multipath in a constructive way - the net result being higher SNR at the receiver and increased throughput.
-Gareth