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59
Large system analysis of linear precoding in correlated MISO broadcast channels under limited feedback
 IEEE TRANS. INF. THEORY
, 2012
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Minimum Mean Squared Error Interference Alignment
"... Abstract—To achieve the full multiplexing gain of MIMO interference networks at high SNRs, the interference from different transmitters must be aligned in lowerdimensional subspaces at the receivers. Recently a distributed “maxSINR” algorithm for precoder optimization has been proposed that achiev ..."
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Cited by 41 (1 self)
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Abstract—To achieve the full multiplexing gain of MIMO interference networks at high SNRs, the interference from different transmitters must be aligned in lowerdimensional subspaces at the receivers. Recently a distributed “maxSINR” algorithm for precoder optimization has been proposed that achieves interference alignment for sufficiently high SNRs. We show that this algorithm can be interpreted as a variation of an algorithm that minimizes the sum Mean Squared Error (MSE). To maximize sum utility, where the utility depends on rate or SINR, a weighted sum MSE objective is used to compute the beams, where the weights are updated according to the sum utility objective. We specify a class of utility functions for which convergence of the sum utility to a local optimum is guaranteed with asynchronous updates of beams, receiver filters, and utility weights. Numerical results are presented, which show that this method achieves interference alignment at high SNRs, and can achieve different points on the boundary of the achievable rate region by adjusting the MSE weights. I.
Linear precoding in cooperative MIMO cellular networks with limited coordination clusters
 IEEE J. Sel. Areas Commun
, 2010
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Large System Analysis of Linear Precoding in MISO Broadcast Channels with Limited Feedback
, 2010
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Linear Transceiver Design for Interference Alignment: Complexity and Computation
, 2010
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Optimal design of spatial sourceandrelaymatrices for a nonregenerative twoway MIMO relay system
 IEEE Trans. Wireless Commun
, 2011
"... Abstract—This paper considers a system where two users exchange information via a nonregenerative halfduplex twoway MIMO relay and each of the two users and the relay is equipped with multiple antennas. We study the design of the spatial source covariance matrices (or source matrices) at the two ..."
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Cited by 21 (1 self)
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Abstract—This paper considers a system where two users exchange information via a nonregenerative halfduplex twoway MIMO relay and each of the two users and the relay is equipped with multiple antennas. We study the design of the spatial source covariance matrices (or source matrices) at the two users and the spatial transformation matrix (or relay matrix) at the relay to maximize the achievable weighted sum rate of the system. The source matrices and the relay matrix are optimized alternately until convergence. If the relay matrix is given, we show that the optimal design of the source matrices (for uniformly weighted sum rate) follows a generalized water filling (GWF) algorithm. If the source matrices are given, we show two search algorithms to optimize the relay matrix. The first algorithm is a hybrid gradient method which adaptively switches between the (steepest) gradient descent and the Newton’s search. The second is an iterative weighted minimum mean square error (WMMSE) method which alternately refines the MMSE equalizers at the users and the relay matrix. We compare the convergence behaviors of the two algorithms and demonstrate their advantage over prior algorithms. We also show an optimal structure of the relay matrix, which is useful to reduce the search complexity. Index Terms—Smart relays, multiantenna relays, twoway relays, power scheduling, eigenbeamforming, gradient methods, weighted minimum mean square errors, generalized waterfilling algorithm. I.
Linear precoding designs for amplifyandforward multiuser twoway relay systems
 in Proc. IEEE GLOBECOM
, 2011
"... AbstractWe investigate the linear precoding designs for multiuser twoway relay system (MUTWRS) where a multiantenna basestation (BS) communicates with multiple singleantenna mobile stations (MSs) via a multiantenna relay station (RS). The amplifyandforward (AF) relay protocol is employed. Th ..."
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Cited by 20 (6 self)
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AbstractWe investigate the linear precoding designs for multiuser twoway relay system (MUTWRS) where a multiantenna basestation (BS) communicates with multiple singleantenna mobile stations (MSs) via a multiantenna relay station (RS). The amplifyandforward (AF) relay protocol is employed. The design goal is to optimize the precodings at BS, RS or both so as to minimize the total meansquare error (MSE) of the uplink messages while maintaining the individual signaltointerferenceplusnoise ratio (SINR) requirement for each downlink signal. We show that the BS precoding design problem can be converted to a standard second order cone programming (SOCP), while the RS precoding is nonconvex for which a local optimal solution is obtained using an iterative algorithm. A joint BSRS precoding is also obtained by alternating optimization of BS precoding and RS precoding with guaranteed convergence. Numerical results show that RSprecoding is superior to BSprecoding. Furthermore, the joint BSRS precoding can significantly outperform the two individual precoding schemes. The implementation issues including complexity and feedback overhead are also discussed.
A tutorial on the optimization of amplifyandforward MIMO relay systems
 IEEE J. Select. Areas Commun
, 2012
"... Abstract—The remarkable promise of multipleinput multipleoutput (MIMO) wireless channels has motivated an intense research activity to characterize the theoretical and practical issues associated with the design of transmit (source) and receive (destination) processing matrices under different op ..."
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Cited by 19 (7 self)
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Abstract—The remarkable promise of multipleinput multipleoutput (MIMO) wireless channels has motivated an intense research activity to characterize the theoretical and practical issues associated with the design of transmit (source) and receive (destination) processing matrices under different operating conditions. This activity was primarily focused on pointtopoint (singlehop) communications but more recently there has been an extensive work on twohop or multihop settings in which single or multiple relays are used to deliver the information from the source to the destination. The aim of this tutorial is to provide an uptodate overview of the fundamental results and practical implementation issues in designing amplifyandforward MIMO relay systems. Index Terms—Tutorial, MIMO, optimization, transceiver design, amplifyandforward, nonregenerative relay, power allocation, majorization theory, qualityofservice requirements, singlehop, twohop, multihop, oneway, twoway, multiple relays, perfect channel state information, robust design. I.
Wireless MIMO switching: Weighted sum mean square error and sum rate optimization
 IEEE TRANS. INF. THEORY
, 2013
"... This paper addresses joint transceiver and relay design for a wireless multipleinput multipleoutput (MIMO) switching scheme that enables data exchange amongmultiple users. Here, a multiantenna relay linearly precodes the received (uplink) signals frommultiple users and forwards the signal in the ..."
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Cited by 9 (4 self)
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This paper addresses joint transceiver and relay design for a wireless multipleinput multipleoutput (MIMO) switching scheme that enables data exchange amongmultiple users. Here, a multiantenna relay linearly precodes the received (uplink) signals frommultiple users and forwards the signal in the downlink, where the purpose of precoding is to let each user receive its desired signal with interference from other users suppressed. The problem of optimizing the precoder based on various design criteria is typically nonconvex and difficult to solve. Themain contribution of this paper is a unified approach to solve the weighted summean square error (MSE) minimization and weighted sum rate maximization problems inMIMOswitching. Specifically, an iterative algorithm is proposed for jointly optimizing the relay’s precoder and the users’ receive filters to minimize the weighted sum MSE. It is also shown that the weighted sum rate maximization problem can be reformulated as an iterated weighted sumMSEminimization problem and can, therefore, be solved similarly to the case of weighted sumMSE minimization. With properly chosen initial values, the proposed iterative algorithms are asymptotically optimal in both high and lowsignaltonoiseratio regimes for MIMO switching, either with or without selfinterference cancellation (a.k.a., physicallayer network coding). Numerical results show that the optimized MIMO switching scheme based on the proposed algorithms significantly outperforms existing approaches in the literature.
Fast Converging Algorithm for Weighted Sum Rate Maximization
 in Multicell MISO Downlink,h IEEE Signal Process. Letters
, 2012
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