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A MIMO WLAN based on linear channel inversion

: Jungnickel, V.; Haustein, T.; Jorswieck, E.; Helmolt, C. von

	IEE Professional Network for Antennas and Propagation: MIMO: Communications systems from concept to implementations: Seminar : Wednesday, 12 Dcember 2001, Savoy Place, London London: IEE, 2001 (Digest. Institution of Electrical Engineers 2001,175) pp.20/1-6
	Seminar "MIMO: Communications Systems from Concept to Implementations" <2001, London>

	English
	Conference Paper
	Fraunhofer HHI ()
	channel capacity; channel coding; electromagnetic wave scattering; indoor radio; mimo systems; radiowave propagation; rayleigh channels; signal processing; statistical analysis; transmitting antennas; wireless lan; mimo wlan; linear channel inversion; multiple-input multiple-output techniques; wireless local area networks; radiowave scattering; channel information; reciprocity; real-time applications; isotropic noise gain; power distribution; statistical properties; rayleigh fading; transmitting antenna; transmitter power

Abstract
Multiple-input multiple-output (MIMO) techniques may increase the capacity of wireless local area networks (WLAN) since they profit from rich scattering of radio waves in indoor environments. On the other hand, much signal processing must be performed in a very short time to reach practical data rates. This paper reports on elementary steps towards MIMO transmission when the channel is known to the transmitter. In most cases, channel information can be obtained at the transmitter by means of reciprocity. Linear channel inversion (LCI) may then be employed allowing simple processing suitable for real-time applications. In contrast to signal processing at the receiver, LCI offers isotropic noise gain which simplifies coding. On the other hand, power distribution at the transmitter depends on the statistical properties of the MIMO channel. Results in the case of Rayleigh fading indicate that at least one additional antenna is needed at the transmitter for reliable operation. Asimple formula for the mean transmitter power is reported and confirmed by simulation. Performance can now be expressed in terms of transmitter power and a fair comparison with transmission based on signal processing at the receiver is possible.