Precoding for the Multiantenna Downlink: Multiuser SNR Gap and Optimal User Ordering

This paper develops a practical design method for implementing Tomlinson-Harashima precoding (THP) in a downlink channel with multiple antennas at the transmitter and a single antenna at each receiver. A two-step design process is proposed for minimizing the total transmit power while satisfying eve...

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Bibliographic Details
Published in:IEEE transactions on communications 2007-01, Vol.55 (1), p.188-197
Main Authors: Fung, C.-H.F., Wei Yu, Teng Joon Lim
Format: Article
Language:English
Subjects:
Algorithms
Antennas
Applied sciences
Bit error rate
Broadcast channel (BC)
Channels
Coding, codes
Covariance matrix
Design engineering
Design methodology
Downlink
Exact sciences and technology
Information, signal and communications theory
Mathematical analysis
Modulation, demodulation
multiple antennas
multiple-access channel (MAC)
Optimization
Polynomials
Process design
Quadrature amplitude modulation
Radiocommunications
Receivers
Receiving antennas
Signal and communications theory
signal-to-noise ratio (SNR) gap approximation
spatial multiplex
Studies
Systems, networks and services of telecommunications
Telecommunications
Telecommunications and information theory
Tomlinson-Harashima precoding (THP)
Transmission and modulation (techniques and equipments)
Transmitters
Transmitting antennas
uplink-downlink duality
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Summary:This paper develops a practical design method for implementing Tomlinson-Harashima precoding (THP) in a downlink channel with multiple antennas at the transmitter and a single antenna at each receiver. A two-step design process is proposed for minimizing the total transmit power while satisfying every user's minimum data rate and maximum bit-error rate (BER) requirements. First, the BER and rate requirements are converted to "virtual rate" requirements, which account for the gap-to-capacity introduced by practical quadrature amplitude modulation (QAM) and THP. The second step is to determine the transmit covariance matrices (which specify the entire THP system) that will provide these virtual rates at the minimum total transmit power. As one of the main features in the proposed scheme, an algorithm for finding the optimal user encoding (or presubtraction) order in polynomial time is proposed. In addition, we also propose an algorithm that finds a near-optimal order, but which is much less complex. The proposed method outperforms existing zero-forcing-based THP systems in term of power efficiency
ISSN:0090-6778
1558-0857
DOI:10.1109/TCOMM.2006.885095