Adaptive orthogonal beamforming for the MIMO broadcast channel

This paper addresses both the user selection and the linear precoding design of a MIMO broadcast channel where the number of users is assumed to be greater than the number of transmit antennas. The optimization criterion considered is the sum-rate. A greedy algorithm tackling jointly the two issues is developed. It sequentially adds new users so as their beamformers build up an orthonormal basis which is optimized with the help of the channel knowledge assumed to be exhaustive. This solution benefits asymptotically (in the limit of a large number of users) from the full multiplexing and multiuser diversity gains alike the capacity achieving dirty paper coding. Moreover, it exhibits better results than existing schemes and offers some advantages resulting from the choice of an orthogonal structure. © 2007 IEEE

Optimization of linear pre/decoders for multi-user closed-loop MIMO-OFDM

This paper deals with a multi-user downlink MIMO-OFDM scheme with perfect channel knowledge at both the transmit and receive sides. The objective is to optimize the average BER while fulfilling each user's rate and satisfying a global transmit power constraint. Space Division Multiple Access (SDMA) is investigated and three new iterative schemes are proposed to compute the linear pre/decoders. The results exhibit, inter alia, that orthogonalizing the channels does not lead to the best results. © 2005 IEEE

Interference-free multi-user MIMO-OFDM

A multi-user downlink MIMO-OFDM scheme is considered. Perfect channel knowledge is assumed at the base station and linear processing is used at both the transmit and receive sides. The objective is to optimize the mean BER of the system while satisfying a transmit power constraint and fulfilling each user's rate. FDMA and SDMA are investigated. We show how the multi-user interference induced by SDMA can be annihilated and exhibit that this multiple access technique should be preferred to FDMA. © 2005 IEEE

Cognitive radio systems evaluation: measurement, modeling, and emulation approach

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Real-time ultra-wideband spectrum management in critical civil infrastructures : UCELSS project

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Utility-based MIMO uplink beamforming

This paper1 addresses the design of transmit and receive beamformers in a Multiple-Input Multiple-Output (MIMO) uplink system. To optimize the beamformers, we introduce a new utility function denned as a weighted difference between users' rates and their transmit power. This new criterion allows to take into account whether the users are more rate-sensitive or powersensitive. Beamformers and power allocation are iteratively computed by resorting to the framework of non-cooperative game theory. ©2006 IEEE

Management of UWB picocell clusters : UCELLS project approach

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