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Sum capacity of the vector Gaussian broadcast channel and uplinkdownlink duality
 IEEE TRANS. ON INFORM. THEORY
, 2003
"... We characterize the sum capacity of the vector Gaussian broadcast channel by showing that the existing inner bound of Marton and the existing upper bound of Sato are tight for this channel. We exploit an intimate fourway connection between the vector broadcast channel, the corresponding pointtopo ..."
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Cited by 323 (2 self)
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We characterize the sum capacity of the vector Gaussian broadcast channel by showing that the existing inner bound of Marton and the existing upper bound of Sato are tight for this channel. We exploit an intimate fourway connection between the vector broadcast channel, the corresponding pointtopoint channel (where the receivers can cooperate), the multiple access channel (where the role of transmitters and receivers are reversed), and the corresponding pointtopoint channel (where the transmitters can cooperate).
Sum Capacity of the Multiple Antenna Gaussian Broadcast Channel And UplinkDownlink Duality
 IEEE Transactions on Information Theory
, 2002
"... We characterize the sum capacity of the multiple antenna Gaussian broadcast channel by showing that the existing inner bound of Marton and the existing upper bound of Sato are tight for this channel. We exploit an intimate fourway connection between the multiple antenna broadcast channel, the corre ..."
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Cited by 48 (4 self)
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We characterize the sum capacity of the multiple antenna Gaussian broadcast channel by showing that the existing inner bound of Marton and the existing upper bound of Sato are tight for this channel. We exploit an intimate fourway connection between the multiple antenna broadcast channel, the corresponding pointtopoint channel (where the receivers can cooperate), the multiple access channel (where the role of transmitters and receivers are reversed), and the corresponding pointtopoint channel (where the transmitters can cooperate).
On the Capacity of the Multiple Antenna Broadcast Channel
 DIMACS SERIES IN DISCRETE MATHEMATICS AND THEORETICAL COMPUTER SCIENCE
"... The capacity region of the multiple antenna (transmit and receive) broadcast channel is considered. We propose an outer bound to the capacity region by converting this nondegraded broadcast channel into a degraded one with users privy to the signals of users ordered below them. We extend our proof ..."
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Cited by 37 (3 self)
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The capacity region of the multiple antenna (transmit and receive) broadcast channel is considered. We propose an outer bound to the capacity region by converting this nondegraded broadcast channel into a degraded one with users privy to the signals of users ordered below them. We extend our proof techniques in the characterization of the sum capacity of the multiple antenna broadcast channel to evaluate this outer bound with Gaussian inputs. Our main result is the observation that if Gaussian inputs are optimal to the constructed degraded channel, then the capacity region of the multiple antenna broadcast channel is characterized.
The Impact of Space Division Multiplexing on Resource Allocation: A Unified Approach
, 2003
"... Recent advances in the area of wireless communications have revealed the emerging need for efficient wireless access in personal, local and wide area networks. Space division multiple access (SDMA) with smart antennas at the base station is recognized as a promising means of increasing system capaci ..."
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Cited by 14 (3 self)
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Recent advances in the area of wireless communications have revealed the emerging need for efficient wireless access in personal, local and wide area networks. Space division multiple access (SDMA) with smart antennas at the base station is recognized as a promising means of increasing system capacity and supporting ratedemanding services. However, the existence of SDMA at the physical layer raises significant issues at higher layers. In this paper, we attempt to capture the impact of SDMA on channel allocation at the media access control (MAC) layer. This impact obtains different forms in TDMA, CDMA and OFDMA access schemes, due to the different cochannel and interchannel interference instances, as well as the different effect of corresponding channels (time slots, codes or subcarrier frequencies) on user channel characteristics. We follow a unified approach for these multiple access schemes and propose heuristic algorithms to allocate channels to users and adjust downlink beamforming vectors and transmission powers, with the objective to increase achievable system rate and provide QoS to users in the form of minimum rate guarantees. We consider the class of greedy algorithms, based on criteria such as minimum induced or received interference and minimum signaltointerference ratio (SIR), as well as the class of SIR balancing algorithms. Our results indicate that this crosslayer approach yields significant performance benefits and that SIR balancing algorithms achieves the best performance.
Joint Base Station Association and Power Allocation for Uplink SumRate Maximization
"... Abstract—In this paper, the problem of sumrate maximization with Quality of Service (QoS) for a multicell multiuser uplink is addressed. The problem is formulated as a Mixed Integer Nonlinear Programming (MINLP) problem with nonconvex feasible region and hence is difficult to solve. A primald ..."
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Cited by 2 (0 self)
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Abstract—In this paper, the problem of sumrate maximization with Quality of Service (QoS) for a multicell multiuser uplink is addressed. The problem is formulated as a Mixed Integer Nonlinear Programming (MINLP) problem with nonconvex feasible region and hence is difficult to solve. A primaldual infeasibleinteriorpoint method (IIPM) is applied to jointly optimize resources. With this method, simultaneously optimizing the Base Station Association (BSA) and Power Allocation (PA) is possible. Further to reduce the size, the problem is decomposed into two subproblems. The NPhard Integer Programming (IP) BSA subproblem from the decomposition is solved by two different methods. One method uses the IIPM and other uses a Semidefinite Programming formulation. The PA subproblem is solved iteratively by IIPM. Simulation results converge to the optimum obtained by an existing exhaustive search. Apart from the sumrate objective, the IIPM is applicable to broad class of utility functions and objectives and it also eliminates the requirement of an initial primal feasible point to begin the algorithm. Index Terms—Base station association, power allocation, mixed integer nonlinear program, primaldual infeasibleinteriorpoint method. I.
A subspace multiuser beamforming algorithm for downlink of mobile communications
 in Proc. IEEE Int. Symp. Circuits Syst., May 2004
"... Abstract—A new algorithm for downlink multiuser beamforming in mobile communications is described. The optimization problem is reformulated by modifying the constraints so that weight vectors of different mobile stations are optimized in a reduced feasible region which is a subset of that of the mu ..."
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Cited by 1 (0 self)
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Abstract—A new algorithm for downlink multiuser beamforming in mobile communications is described. The optimization problem is reformulated by modifying the constraints so that weight vectors of different mobile stations are optimized in a reduced feasible region which is a subset of that of the multiuser beamforming problem. The downlink beamforming weight vectors of different mobile stations are then jointly optimized in a subspace instead of searching in the entire parameter space. Simulation results show that the modified optimization problem leads to solutions that satisfy the signaltonoiseplusinterference ratio specification at each mobile station and that the total power transmitted from the base station is very close to the optimal one. The solution of the modified optimization problem requires significantly less computation than the optimal multiuser beamforming algorithms. Index Terms—Antenna arrays, beamforming, downlink. I.
1Inflated Lattice Precoding, Bias Compensation, and the Uplink/Downlink Duality: The Connection
"... Abstract — We review the uplink/downlink duality between decisionfeedback equalization (DFE) and (nonlinear) precoding at the transmitter side. Thereby the effect of bias compensation in DFE is addressed, and its connection to the concept of “inflated lattice precoding ” (ILP)—a tool which has been ..."
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Abstract — We review the uplink/downlink duality between decisionfeedback equalization (DFE) and (nonlinear) precoding at the transmitter side. Thereby the effect of bias compensation in DFE is addressed, and its connection to the concept of “inflated lattice precoding ” (ILP)—a tool which has been proven to be the key to achieve the capacity of channels with interference known at the transmitter—is elucidated. Concentrating on signaltointerference plus noise ratios and hence error rates, pairs of schemes dual to each other are identified. It is shown that bias compensation in DFE and the scaling in ILP are dual operations and cancel each other. I.
On the Impact of Information Theory on Today’s Communication Technology
"... Dedicated to our esteemed colleague Prof. Dr. Heinz Gerhäuser on occasion of his 60 th birthday The impact of results from Information Theory on todays information technology is illustrated by means of derivations from capacity formula and chain rule. By this, the huge possible increase in power and ..."
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Dedicated to our esteemed colleague Prof. Dr. Heinz Gerhäuser on occasion of his 60 th birthday The impact of results from Information Theory on todays information technology is illustrated by means of derivations from capacity formula and chain rule. By this, the huge possible increase in power and bandwidth efficiency for transmission of analog source signals via modern digital communication techniques is enlightened. The foundations of modern approaches like OFDM, CDMA, coded modulation, precoding for equalization, signaling over MIMO channels, etc. in theorems of Information Theory, especially the chain rule is pointed out. 1.
Joint Optimal Power Control and TransmitReceive Beamforming in a MultiUser MIMO Environment
, 2005
"... This master thesis considers joint optimal power control and transmitreceive beamforming for a downlink system in a multiuser MIMO (Multiple Input Multiple Output) environment. The goal of the transmit strategy presented here is to minimize the total transmitted power subject to some desired Quali ..."
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This master thesis considers joint optimal power control and transmitreceive beamforming for a downlink system in a multiuser MIMO (Multiple Input Multiple Output) environment. The goal of the transmit strategy presented here is to minimize the total transmitted power subject to some desired Quality of Service criteria, which are based on the operator’s perspective. This results in a multivariable joint optimization problem with three sets of variables: the transmitter powers, the transmit beamforming vectors and the receive beamforming vectors. Two iterative algorithms will be proposed. The first one is based on the virtual uplink concept, and the solution to this multivariable optimization problem will be determined by optimizing with respect to one set of variables while having the other two fixed. The second algorithm is based on the uplinkdownlink duality for MIMO systems and is solved by minimizing the maximal eigenvalue of an extended coupling matrix. Both algorithms will require global system knowledge and are therefore mainly intended as benchmarks in system simulations. Simulation results will show that both algorithms are producing solutions that might be globally optimal. This is motivated by the fact that the resulting sets of variables are not affected by the initialization process. i