Multiple-antenna communication systems: an emerging technology

Abstract

A recent development in wireless communications is the application of multiple-input multiple-output (MIMO) systems to radio communications via use of multiple antennas. In order to investigate the technology's potential, an experimental MIMO system which contains two four-element antenna arrays (4 × 4) has been developed at the University of Alberta. The system is used to obtain MIMO channel measurements in a typical indoor office environment in the ISM band (902 -928 MHz). Measurement campaigns were performed using different antenna spacings and two different types of antenna: half-wavelength (λ/2) centre-fed dipoles and dual polarized patches. The measurements are used to calculate channel capacities for an indoor 4 × 4 MIMO system. The measurements confirm the high capacity potential of a MIMO channel, with ergodic capacity of approximately 21 bits per channel use available with either antenna type at a signal-to-noise ratio of 20 dB if the antenna element separation is λ/2 or larger. An introduction to basic MIMO theory, a discussion of the University of Alberta wireless MIMO testbed, and observations regarding the measured indoor MIMO channel are presented in the paper.

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“…Ultra-dense SMP. In order to provide uncorrelated copies of the signal for successful MIMO decoding, the minimum separation of the adjacent transmitter and receiver elements must be greater than half the carrier wavelength [74]. This limits the adjacent transmitter/receiver separation to the centimetre range for GHz RF carriers and higher for MHz carriers.…”