 =Wireless communications=
If the transmitter is equipped with formula_1 antennas and the receiver has formula_2 antennas, the maximum spatial multiplexing order (the number of streams) is,

if a linear receiver is used.This means that formula_4 streams can be transmitted in parallel, ideally leading to an formula_4 increase of the spectral efficiency (the number of bits per second per Hz that can be transmitted over the wireless channel).The practical multiplexing gain can be limited by spatial correlation, which means that some of the parallel streams may have very weak channel gains.