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INTRO_MIMO&OFDM_3

# INTRO_MIMO&OFDM_3 - THE NON-ENGINEERS INTRODUCTION TO...

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THE NON-ENGINEER’S INTRODUCTION TO MIMO AND MIMO-OFDM http://www.mimo.ucla.edu Various schemes that employ multiple antennas at the transmitter and receiver are being considered to improve the range and performance of communication systems. By far the most promising multiple antenna technology today happens to be the so called multiple-input multiple-output (MIMO) system. MIMO systems employ multiple antennas at both the transmitter and receiver as shown in Figure . Data 1:N DEMUX MODULATOR MODULATOR MODULATOR MIMO Receiver ENCODER x 1 (t) x 2 (t) x 3 (t) r 1 (t) = h 11 x 1 (t)+h 12 x 2 (t)+h 13 x 3 (t) r 3 (t) = h 31 x 1 (t)+h 32 x 2 (t)+h 33 x 3 (t) Figure 1 A Generic MIMO system They transmit independent data (say x 1 , x 2 , …, x N ) on different transmit antennas simultaneously and in the same frequency band. At the receiver, a MIMO decoder users M N antennas. Assuming N receive antennas, and representing the signal received by each antenna as r j we have: N NN N N N N N N N x h x h x h r x h x h x h r x h x h x h r + + + = + + + = + + + = L M L L 2 2 1 1 2 2 22 1 21 2 1 2 12 1 11 1 As can be seen from the above set of equations, in making their way from the transmitter to the receiver, the independent signals {x1, x2, …, xN} are all combined. Traditionally this “combination” has been treated as interference. However, by treating the channel as a matrix, we can in fact recover the independent transmitted streams {xi}. To recover the transmitted data

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