ANTENNAS IN WIRELESS COMMUNICATION

A conventional radio uses one antenna to transmit a datastream.
A smart antenna uses multiple antenna to transmit a datastream.
Smart antenna techniques are one-dimensional.
MIMO uses multi-dimensional antenna.
It builds on one-dimensional smart antenna technology by simultaneously transmitting multiple datastreams through the same channel, which increases wireless capacity
The use of antennas at both transmitter and receiver allows –
1.Multiplicative increase in capacity and spectral efficiency
2.Dramatic reductions of fading thanks to diversity
3.Increased system capacity (number of users)
4.Lower probability of detection
5.Improved resistance to interference

Smart antenna techniques use multiple antennas to improve wireless performance and reliability
– Antennas themselves are “dumb” pieces of metal
– “Smartness” comes from signal processing that is applied to the multiple antennas
– There are differing degrees of smartness

Conventional, “single-dimension” (1D) smart antenna techniques transmit just one data stream per channel
– RF beamforming
– Digital beamforming
– Digital receive diversity combining

• MIMO makes smart antennas “multi-dimension”
– Multiple data streams in the same channel
– 2-D signals