MIMO

Multiple Input Multiple Outlut

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MIMO, is multiple input, multiple output meaning that the signal are transmitted on different frequencies to different antenna on the receiver, as can be seen in the diagram.

For example, if a phone has 2 antennae tuned to two different frequencies then it can receive half the packets on one antenna and the other half on another. To get the full transmission the packets are put together, In this example the speed of receiving the data is twice the speed of a single input. However to add complexity, and speed up the transmission, the transmitter splits the data between two different channels and uses multiplexing to send two different signals to the receiver at the same time. So with 2 channels at each of the transmitter and receiver the speed up is (theoretically a factor or 4). But with 4 channels transmitted and two received in the mobile phone there is a potential factor of 8 increase in network speed.

Real MIMO is much complex than indicated here. It all depends on network conditions, how strong the signals are. The transmitter is much more dynamic than indicated and picks the best transmission to the receiver, dependent on these conditions. Indeed in LTE-Advance the different signals can be transmitted on different transmission bands.