Fundamentals of wireless communication
Fundamentals of wireless communication
How much multiuser diversity gain is required over large-scale fading?
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
On downlink beamforming with greedy user selection: performance analysis and a simple new algorithm
IEEE Transactions on Signal Processing - Part I
IEEE Transactions on Signal Processing
Acquiring Partial CSI for Spatially Selective Transmission by Instantaneous Channel Norm Feedback
IEEE Transactions on Signal Processing
Distributed closed-loop spatial multiplexing for uplink multiuser systems
IEEE Transactions on Wireless Communications
Capacity of fading channels with channel side information
IEEE Transactions on Information Theory
Opportunistic beamforming using dumb antennas
IEEE Transactions on Information Theory
On the optimality of multiantenna broadcast scheduling using zero-forcing beamforming
IEEE Journal on Selected Areas in Communications
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Multiuser diversity (MUDiv) is one of the central concepts in multiuser (MU) systems. In particular, MUDiv allows for scheduling among users in order to eliminate the negative effects of unfavorable channel fading conditions of some users on the system performance. Scheduling, however, consumes energy (e.g., for making users' channel state information available to the scheduler). This extra usage of energy, which could potentially be used for data transmission, can be very wasteful, especially if the number of users is large. In this paper, we answer the question of how much MUDiv is required for energy limited MU systems. Focusing on uplink MU wireless systems, we develop MU scheduling algorithms which aim at maximizing the MUDiv gain. Toward this end, we introduce a new realistic energy model which accounts for scheduling energy and describes the distribution of the total energy between scheduling and data transmission stages. Using the fact that such energy distribution can be controlled by varying the number of active users, we optimize this number by either i) minimizing the overall system bit error rate (BER) for a fixed total energy of all users in the system or ii) minimizing the total energy of all users for fixed BER requirements. We find that for a fixed number of available users, the achievable MUDiv gain can be improved by activating only a subset of users. Using asymptotic analysis and numerical simulations, we show that our approach benefits from MUDiv gains higher than that achievable by generic greedy access algorithm, which is the optimal scheduling method for energy unlimited systems.