13 May 2013-IEEE Communications Letters (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 17, Iss: 6, pp 1196-1199

TL;DR: It is shown that the SL NR scheme can be viewed as a generalised channel regularisation technique and the conditions for an equivalence between the SLNR, the Regularised Block Diagonalisation (RBD) and the Generalised MMSE Channel Inversion (GMI method 2) schemes are given.

Abstract: In this letter, equivalent expressions of transmit precoding solutions based on the maximum signal-to-leakage-plus-noise ratio (SLNR) are derived for multiuser MIMO systems with multi-antenna receivers. The performance of the SLNR precoding scheme is also analysed based on this equivalent form. Further, it is shown that the SLNR scheme can be viewed as a generalised channel regularisation technique and the conditions for an equivalence between the SLNR, the Regularised Block Diagonalisation (RBD) and the Generalised MMSE Channel Inversion (GMI method 2) schemes are given. Consequently, the performance analysis in this letter can be extended to the RBD and GMI schemes. This generalises the equivalence between the SLNR and MMSE schemes and its useful implications, from the case of single-antenna to multi-antenna receivers.

Abstract: Massive multiple-input multiple-output (MIMO) is a key technology for 5G wireless communications with a promise of significant capacity increase. The use of low-resolution data converters is crucial for massive MIMO to make the overall transmission as cost- and energy-efficient as possible. In this work, we consider a downlink millimeter-wave (mmWave) transmission scenario, where multiple users are served simultaneously by massive MIMO with one-bit digital-to-analog (D/A) converters. In particular, we propose a novel precoder design based on signal-to-leakage-plus-noise ratio (SLNR), which minimizes energy leakage into undesired users while taking into account impairments due to nonlinear one-bit quantization. We show that well-known regularized zero-forcing (RZF) precoder is a particular version of the proposed SLNR-based precoder, which is obtained when quantization impairments are totally ignored. Numerical results underscore significant performance improvements along with the proposed SLNR-based precoder as compared to either RZF or zero-forcing (ZF) precoders.

TL;DR: This work proposes a novel precoder design based on signal-to-leakage-plus-noise ratio (SLNR), which minimizes energy leakage into undesired users while taking into account impairments due to nonlinear one-bit quantization.

Abstract: Massive multiple-input multiple-output (MIMO) is a key technology for 5G wireless communications with a promise of significant capacity increase. The use of low-resolution data converters is crucial for massive MIMO to make the overall transmission as cost- and energy-efficient as possible. In this work, we consider a downlink millimeter-wave (mmWave) transmission scenario, where multiple users are served simultaneously by massive MIMO with one-bit digital-to-analog (D/A) converters. In particular, we propose a novel precoder design based on signal-to-leakage-plus-noise ratio (SLNR), which minimizes energy leakage into undesired users while taking into account impairments due to nonlinear one-bit quantization. We show that well-known regularized zero-forcing (RZF) precoder is a particular version of the proposed SLNR-based precoder, which is obtained when quantization impairments are totally ignored. Numerical results underscore significant performance improvements along with the proposed SLNR-based precoder as compared to either RZF or zero-forcing (ZF) precoders.

TL;DR: An algorithm which combines the triangular decomposition and signal to leakage and noise ratio (SLNR) (TD- SLNR) to suppress strong co-channel interference in multi-cell multiple input and multiple output (MIMO) heterogeneous networks is proposed.

Abstract: The heterogeneous network, contains a macro cell and a grid of low power nodes with the same frequencies, can improve the system capacity and spectrum efficiency. Configuring low-power nodes that share the same spectrum with macro cell to form heterogeneous networks makes it more likely to improve the system capacity and spectrum efficiency, but inevitably, strong co-channel interference is the main barrier to further improvement for heterogeneous networks. This paper proposes an algorithm which combines the triangular decomposition and signal to leakage and noise ratio (SLNR) (TD-SLNR) to suppress strong co-channel interference in multi-cell multiple input and multiple output (MIMO) heterogeneous networks. Firstly, the proposed algorithm can reduce the number of inter-cell interferences in half. As a result of triangular decomposition, an equivalent interference channel model is extracted to eliminate the rest of interferences using SLNR and interference suppression matrix. Theoretical analysis shows that the proposed algorithm provides a potential solution to suppress the co-channel interference with low complexity and reduce the computation complexity without adding extra interference suppression matrices and computation complexity at receivers. Furthermore, the simulation results show that TD-SLNR algorithm can improve system capacity and energy efficiency comparing with the traditional SLNR algorithm.

TL;DR: A modified definition of signal-to-leakage-plus-noise ratio (SLNR) as a criterion for linear transmit filter design in Multi-user MIMO systems and an iterative precoding algorithm is proposed and is studied with two linear receivers.

Abstract: This paper proposes a modified definition of signal-to-leakage-plus-noise ratio (SLNR) as a criterion for linear transmit filter design in Multi-user MIMO systems. The proposed metric incorporates receiver structures into the precoder design, which can potentially exploit unused receive signal subspaces in cases where the available eigenmodes are not fully transmitted. The improvement in terms of the degrees of freedom of the precoder is also elaborated. In addition, an iterative precoding algorithm is proposed and is studied with two linear receivers, namely the matched filter (MF) and the minimum mean square error (MMSE) receivers. Simulation results show that the proposed scheme outperforms the conventional SLNR scheme and can achieve further improvement with an MMSE receiver, at the expense of increased computational complexity and slow convergence rate. Moreover, the proposed scheme is shown to reduce its form to the conventional scheme when full-eigenmode transmission is assumed.

TL;DR: This thesis investigates the application of an iterative leakage-based precoding algorithm to practical multiuser-MIMO systems and proposes several modifications to the aforementioned method which demonstrated improved performance under certain practical conditions.

Abstract: This thesis investigates the application of an iterative leakage-based precoding algorithm to practical multiuser-MIMO systems. We consider the effect of practical impairments including imperfect channel state information, transmit antenna correlation, and timevarying channels. Solutions are derived which improve performance of the algorithm with imperfect channel state information at the transmitter by leveraging knowledge of the second-order statistics of the error. From this work we draw a number of conclusions on how imperfect channel state information may impact the system design including the importance of interference suppression at the receiver and the selection of the number of co-scheduled users. We also demonstrate an efficient approach to improve the convergence of the algorithm when using interference-rejection-combining receivers. Finally, we conduct simulations of an LTE-A system employing the improved algorithm to show its utility for modern communication systems. Iterative Leakage-Based Precoding for Multiuser-MIMO Systems Eric Sollenberger General Audience Abstract This thesis investigates several aspects of a particular method by which multiple users can share radio resources within a wireless system i.e. they may operate on the same frequency and at the same time. This is a desirable capability in modern wireless systems because it improves the efficiency of radio spectrum usage. Radio spectrum has become a very expensive resource in recent years so achieving high efficiency is crucial. Our investigation led us to propose several modifications to the aforementioned method which demonstrated improved performance under certain practical conditions. We further demonstrated the effects of several common system impairments and provided insight into how these impairments effect the system design. Finally, we demonstrated that using this method provides significant gains when used for the latest cellular technology.

2 citations

Cites background from "Equivalent Expressions and Performa..."

...It was shown in [18] that sufficient degrees of freedom exist for the SLNR scheme to drive the leakage power to zero at asymptotic high SNR if ∑ Mi j≠i < Nt is satisfied....

Abstract: Linear algebra and matrix theory are fundamental tools in mathematical and physical science, as well as fertile fields for research. This new edition of the acclaimed text presents results of both classic and recent matrix analyses using canonical forms as a unifying theme, and demonstrates their importance in a variety of applications. The authors have thoroughly revised, updated, and expanded on the first edition. The book opens with an extended summary of useful concepts and facts and includes numerous new topics and features, such as: - New sections on the singular value and CS decompositions - New applications of the Jordan canonical form - A new section on the Weyr canonical form - Expanded treatments of inverse problems and of block matrices - A central role for the Von Neumann trace theorem - A new appendix with a modern list of canonical forms for a pair of Hermitian matrices and for a symmetric-skew symmetric pair - Expanded index with more than 3,500 entries for easy reference - More than 1,100 problems and exercises, many with hints, to reinforce understanding and develop auxiliary themes such as finite-dimensional quantum systems, the compound and adjugate matrices, and the Loewner ellipsoid - A new appendix provides a collection of problem-solving hints.

TL;DR: While the proposed algorithms are suboptimal, they lead to simpler transmitter and receiver structures and allow for a reasonable tradeoff between performance and complexity.

Abstract: The use of space-division multiple access (SDMA) in the downlink of a multiuser multiple-input, multiple-output (MIMO) wireless communications network can provide a substantial gain in system throughput. The challenge in such multiuser systems is designing transmit vectors while considering the co-channel interference of other users. Typical optimization problems of interest include the capacity problem - maximizing the sum information rate subject to a power constraint-or the power control problem-minimizing transmitted power such that a certain quality-of-service metric for each user is met. Neither of these problems possess closed-form solutions for the general multiuser MIMO channel, but the imposition of certain constraints can lead to closed-form solutions. This paper presents two such constrained solutions. The first, referred to as "block-diagonalization," is a generalization of channel inversion when there are multiple antennas at each receiver. It is easily adapted to optimize for either maximum transmission rate or minimum power and approaches the optimal solution at high SNR. The second, known as "successive optimization," is an alternative method for solving the power minimization problem one user at a time, and it yields superior results in some (e.g., low SNR) situations. Both of these algorithms are limited to cases where the transmitter has more antennas than all receive antennas combined. In order to accommodate more general scenarios, we also propose a framework for coordinated transmitter-receiver processing that generalizes the two algorithms to cases involving more receive than transmit antennas. While the proposed algorithms are suboptimal, they lead to simpler transmitter and receiver structures and allow for a reasonable tradeoff between performance and complexity.

3,117 citations

"Equivalent Expressions and Performa..." refers methods in this paper

...ZF is developed into Block Diagonalisation (BD) [3] precoding, and MMSE is extended to Regularised Block Diagonalisation (RBD) [4] and Generalised MMSE Channel Inversion (GMI) [5] schemes....

TL;DR: A simple encoding algorithm is introduced that achieves near-capacity at sum rates of tens of bits/channel use and regularization is introduced to improve the condition of the inverse and maximize the signal-to-interference-plus-noise ratio at the receivers.

Abstract: Recent theoretical results describing the sum capacity when using multiple antennas to communicate with multiple users in a known rich scattering environment have not yet been followed with practical transmission schemes that achieve this capacity. We introduce a simple encoding algorithm that achieves near-capacity at sum rates of tens of bits/channel use. The algorithm is a variation on channel inversion that regularizes the inverse and uses a "sphere encoder" to perturb the data to reduce the power of the transmitted signal. This work is comprised of two parts. In this first part, we show that while the sum capacity grows linearly with the minimum of the number of antennas and users, the sum rate of channel inversion does not. This poor performance is due to the large spread in the singular values of the channel matrix. We introduce regularization to improve the condition of the inverse and maximize the signal-to-interference-plus-noise ratio at the receivers. Regularization enables linear growth and works especially well at low signal-to-noise ratios (SNRs), but as we show in the second part, an additional step is needed to achieve near-capacity performance at all SNRs.

1,687 citations

"Equivalent Expressions and Performa..." refers methods in this paper

...This generalises the equivalence between the SLNR and MMSE schemes proven in [7], [8] and establishes the extension of its implications from the case of singleantenna to multi-antenna receivers....

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...Available: http://arxiv.org/abs/1202.1888 [8] P. Patcharamaneepakorn, S. Armour, and A. Doufexi, “On theEquivalence Between SLNR and MMSE Precoding Schemes with SingleAntenna Receivers,”IEEE Commun....

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...They are later extended to the case of multi-antenna receivers, e.g. ZF is developed into Block Diagonalisation (BD) [3] precoding, and MMSE is extended to Regularised Block Diagonalisation (RBD) [4] and Generalised MMSE Channel Inversion (GMI) [5] schemes....

[...]

...Linear precoding techniques, such as Zero-Forcing (ZF) [1] and Minimum Mean Square Error (MMSE) [1], [2], are initially developed for systems with single-antenna receivers....