SISO to MIMO: Moving Communications from Single-Input
The change has been driven by both customer demand for more mobile services and the decreasing cost of the digital signal processing technology required to deploy high bandwidth broadband wireless systems; the technology can now be used in the variety of commercial communications devices: the phones, PDAs, and the laptops on which we have become so dependent.
The technology of choice for this broadband connection is based on a modulation scheme called Orthogonal Frequency Division Multiplexing (OFDM). OFDM offers very good spectral efficiency and is quite tolerant of the ever-present interference in the bands where it is used. One of the key reasons for this is that it transmits hundreds of symbols simultaneously, yet at a low rate per symbol.