The cell size would be smaller than the
much more familiar term pico-cell.
9.5 MIMO TECHNIQUES
In this section, we will present a multiple-input-multiple-output (MIMO) system. MIMO systems can
be considered as extensions to the ???Smart Antenna??? techniques commonly deployed today. With a
MIMO system a number of transmit antennas are used to transmit data streams to a number of receive
antennas. Our goal is to jointly estimate and combine the spatial streams in their respective ways in
order to improve overall system performance (i.e., BLER, Throughput, and so on). This can be
viewed as having a system with joint transmit and receiver diversity gain [38??“40].
In Fig. 9.23 we present a MIMO system using three transmit and three receive antennas. The spatial
multiplexing of the data streams are highlighted by the solid and dashed lines representing the multipath.
What we can see is that using MIMO is alternatively represented as transmitting data over a matrix
channel instead of a vector channel. In the case where scalar weights are used in the receiver, it
assumes a flat fading channel is encountered. Otherwise creating a MIMO equalizer architecture can
be considered an extension and will be discussed latter.
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