a multiple - output multiple - input code - division multiple access apparatus and the coding method thereof . the apparatus includes a transmitter side and receiver side . both of the transmitter side and the receiver side have a plurality of antennas for achieving the effect of multi - path transmission and receiving . in addition , at the receiver side , use preamble - spreading codes and space - time block coding technology to eliminate multi - path signal interference as well as to modify carrier frequency shift of the received signal .