# On the Use of Multiple Antennas for Downlink of Wireless Systems

Abstract : For point-to-point communication, Multi-Input Multi-Output technology has emerged as an attractive solution to increase the capacity by providing multiplexing gain and/or to improve the link quality by diversity. The first part focuses on the use of multiple antennas to increase the reliability of wireless links via space-time coding (STC). For frequency selective multi-input single-output fading channels, we propose a STC scheme that concatenates trellis-coded modulation with time-reversal orthogonal space-time block coding. Numerical examples show that our scheme offers superior performance at lower complexity than the existing schemes thanks to reduced-state joint equalization and decoding. The second and third parts investigate the use of multiple transmit antennas in a point-to-multipoint downlink system with channel state information at transmitter (CSIT). In the second part, we compare and random opportunistic'' beamforming by restricting ourselves to a rate feedback. We take into account the realistic aspects such as random packet arrivals, correlated block-fading channels, and a feedback delay. The realistic assumption of non-perfect CSIT yields a non-trivial tradeoff between multiuser diversity achieved by opportunistic beamforming and transmit diversity achieved by STC. In the third part, we consider a more qualitative analog feedback" in which each user sends back its estimated channel without quantizing and coding. We propose a novel method for user selection and linear beamforming that maximizes a weighted sum rate over a beamforming matrix. Over a time-varying channel, our scheme achieves a smaller average delay than the previously considered schemes.
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https://pastel.archives-ouvertes.fr/pastel-00001329
Contributor : Ecole Télécom Paristech <>
Submitted on : Wednesday, July 13, 2005 - 8:00:00 AM
Last modification on : Friday, July 31, 2020 - 10:44:03 AM
Long-term archiving on: : Saturday, November 26, 2016 - 4:11:43 PM

### Identifiers

• HAL Id : pastel-00001329, version 1

### Citation

Mari Kobayashi. On the Use of Multiple Antennas for Downlink of Wireless Systems. domain_other. Télécom ParisTech, 2005. English. ⟨pastel-00001329⟩

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