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42
Iterative Waterfilling for Gaussian Vector Multiple Access Channels
 IEEE Transactions on Information Theory
, 2001
"... This paper characterizes the capacity region of a Gaussian multiple access channel with vector inputs and a vector output with or without intersymbol interference. The problem of finding the optimal input distribution is shown to be a convex programming problem, and an efficient numerical algorithm ..."
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Cited by 190 (11 self)
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This paper characterizes the capacity region of a Gaussian multiple access channel with vector inputs and a vector output with or without intersymbol interference. The problem of finding the optimal input distribution is shown to be a convex programming problem, and an efficient numerical algorithm is developed to evaluate the optimal transmit spectrum under the maximum sum data rate criterion. The numerical algorithm has an it#8 at#8 e wat#8filling int#j pret#4968 . It converges from any starting point and it reaches with in s per output dimension per transmission from the Kuser multiple access sum capacity af t#j just one it#4 at#49 . These results are also applicable to vector multiple access fading channels.
Designing Structured Tight Frames via an Alternating Projection Method
, 2003
"... Tight frames, also known as general WelchBoundEquality sequences, generalize orthonormal systems. Numerous applicationsincluding communications, coding and sparse approximationrequire finitedimensional tight frames that possess additional structural properties. This paper proposes an alterna ..."
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Cited by 44 (6 self)
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Tight frames, also known as general WelchBoundEquality sequences, generalize orthonormal systems. Numerous applicationsincluding communications, coding and sparse approximationrequire finitedimensional tight frames that possess additional structural properties. This paper proposes an alternating projection method that is versatile enough to solve a huge class of inverse eigenvalue problems, which includes the frame design problem. To apply this method, one only needs to solve a matrix nearness problem that arises naturally from the design specifications. Therefore, it is fast and easy to develop versions of the algorithm that target new design problems. Alternating projection will often succeed even if algebraic constructions are unavailable. To demonstrate
An overview of limited feedback in wireless communication systems
 IEEE J. SEL. AREAS COMMUN
, 2008
"... It is now well known that employing channel adaptive signaling in wireless communication systems can yield large improvements in almost any performance metric. Unfortunately, many kinds of channel adaptive techniques have been deemed impractical in the past because of the problem of obtaining channe ..."
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Cited by 43 (8 self)
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It is now well known that employing channel adaptive signaling in wireless communication systems can yield large improvements in almost any performance metric. Unfortunately, many kinds of channel adaptive techniques have been deemed impractical in the past because of the problem of obtaining channel knowledge at the transmitter. The transmitter in many systems (such as those using frequency division duplexing) can not leverage techniques such as training to obtain channel state information. Over the last few years, research has repeatedly shown that allowing the receiver to send a small number of information bits about the channel conditions to the transmitter can allow near optimal channel adaptation. These practical systems, which are commonly referred to as limited or finiterate feedback systems, supply benefits nearly identical to unrealizable perfect transmitter channel knowledge systems when they are judiciously designed. In this tutorial, we provide a broad look at the field of limited feedback wireless communications. We review work in systems using various combinations of single antenna, multiple antenna, narrowband, broadband, singleuser, and multiuser technology. We also provide a synopsis of the role of limited feedback in the standardization of next generation wireless systems.
Transceiver optimization for multiuser MIMO systems
 IEEE Tran. on Signal Processing, 52(1):214 – 226
, 2004
"... Abstract—We consider the uplink of a multiuser system where the transmitters as well as the receiver are equipped with multiple antennas. Each user multiplexes its symbols by a linear precoder through its transmit antennas. We work with the systemwide mean squared error as the performance measure a ..."
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Cited by 40 (9 self)
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Abstract—We consider the uplink of a multiuser system where the transmitters as well as the receiver are equipped with multiple antennas. Each user multiplexes its symbols by a linear precoder through its transmit antennas. We work with the systemwide mean squared error as the performance measure and propose algorithms to find the jointly optimum linear precoders at each transmitter and linear decoders at the receiver. We first work with the case where the number of symbols to be transmitted by each user is given. We then investigate how the symbol rate should be chosen for each user with optimum transmitters and receivers. The convergence analysis of the algorithms is given, and numerical evidence that supports the analysis is presented. Index Terms—MMSE receivers, multiuser MIMO system, receiver beamforming, transmitter beamforming.
Signature Optimization for CDMA with Limited Feedback
 IEEE TRANS. INFORM. THEORY
, 2005
"... We study the performance of joint signaturereceiver optimization for Direct Sequence (DS)Code Division Multiple Access (CDMA) with limited feedback. The receiver for a particular user selects the signature from a signature codebook, and relays the corresponding B index bits to the transmitter over ..."
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Cited by 18 (8 self)
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We study the performance of joint signaturereceiver optimization for Direct Sequence (DS)Code Division Multiple Access (CDMA) with limited feedback. The receiver for a particular user selects the signature from a signature codebook, and relays the corresponding B index bits to the transmitter over a noiseless channel. We study the performance of a Random Vector Quantization (RVQ) scheme in which the codebook entries are independent and isotropically distributed. Assuming the interfering signatures are independent, and have independent, identically distributed elements, we evaluate the received SignaltoInterference plus Noise Ratio (SINR) in the large system limit as the number of users, processing gain, and feedback bits B all tend to infinity with fixed ratios. This SINR is evaluated for both the matched filter and linear Minimum Mean Squared Error (MMSE) receivers. Furthermore, we show that this large system SINR is the maximum that can be achieved over any sequence of codebooks. Numerical results show that with the MMSE receiver one feedback bit per signature coefficient achieves close to singleuser performance. We also consider a less complex and suboptimal reducedrank signature optimization scheme in which the user's signature is constrained to lie in a lower dimensional subspace. The optimal subspace coefficients are scalarquantized and relayed to the transmitter. The large system performance of the quantized reducedrank scheme can be approximated, and numerical results show that it performs in the vicinity of the RVQ bound. Finally, we extend our analysis to the scenario in which a subset of users optimize their signatures in the presence of random interference.
Interference Avoidance and Multiaccess Vector Channels
 IEEE Transactions on Information Theory
, 2001
"... Application of interference avoidance methods to multiaccess vector channels is presented in this correspondence. Using a very general signal space approach it is shown that sequential application of the eigenalgorithm for interference avoidance by all users in a multiuser system is equivalent t ..."
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Cited by 16 (10 self)
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Application of interference avoidance methods to multiaccess vector channels is presented in this correspondence. Using a very general signal space approach it is shown that sequential application of the eigenalgorithm for interference avoidance by all users in a multiuser system is equivalent to iterative water filling and always yields codeword ensembles that maximize the sum capacity of the multiaccess vector channel. 1
game theory perspective on interference avoidance
 in Proc. IEEE Globecom
"... Abstract – We show that the fixed power, synchronous Interference Avoidance (IA) scheme of [3] employing the (greedy) eigeniteration can be modeled as the recently developed potential game of [10]. Motivated by the fact that receivers can make small mistakes, we consider the convergence of the eige ..."
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Cited by 13 (3 self)
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Abstract – We show that the fixed power, synchronous Interference Avoidance (IA) scheme of [3] employing the (greedy) eigeniteration can be modeled as the recently developed potential game of [10]. Motivated by the fact that receivers can make small mistakes, we consider the convergence of the eigeniteration when noise is added in a manner similar to [2]. Further, we restrict ourselves to a class of signal environments that we call levelable environments. Applying gametheory, we obtain a convergence result similar to that of [2] for levelable environments: arbitrarily small noise assures that the eigeniteration almost surely converges to a neighborhood of the optimum signature set. I.
Adaptation, Coordination and Distributed Resource Allocation in InterferenceLimited Wireless Networks
"... A sensible design of wireless networks involves striking a good balance between an aggressive reuse of the spectral resource throughout the network and managing the resulting cochannel interference. Traditionally this problem has been tackled using a “divide and conquer” approach. The latter consis ..."
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Cited by 13 (3 self)
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A sensible design of wireless networks involves striking a good balance between an aggressive reuse of the spectral resource throughout the network and managing the resulting cochannel interference. Traditionally this problem has been tackled using a “divide and conquer” approach. The latter consists in deploying the network with a static or semidynamic pattern of resource reutilization. The chosen reuse factor, while sacrificing a substantial amount of efficiency, brings the interference to a tolerable level. The resource can then be managed in each cell so as to optimize the per cell capacity using an advanced air interface design. In this paper we focus our attention on the overall network capacity as a measure of system performance. We consider the problem of resource allocation and adaptive transmission in multicell scenarios. As a key instance, the problem of joint scheduling and power control simultaneously in multiple transmitreceive links, which employ capacityachieving adaptive codes, is studied. In principle, the solution of such an optimization hinges on tough issues such as the computational complexity and the requirement for heavy receivertotransmitter feedback and, for cellular networks, celltocell channel state information (CSI) signaling. We give asymptotic properties pertaining to ratemaximizing power control and scheduling in multicell networks. We then present some promising leads for substantial complexity and signaling reduction via the use of newly developed distributed and game theoretic techniques.
Iterative transmitter and receiver optimization for CDMA networks
 IEEE Trans. Wireless Commun
, 2004
"... Abstract—Optimization of the capacity of a singlecell codedivision multipleaccess (CDMA) system, both from the perspective of the maximum number of users that can be served at a required quality of service level and from the information theoretic perspective, has been recently shown to be achieve ..."
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Cited by 12 (3 self)
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Abstract—Optimization of the capacity of a singlecell codedivision multipleaccess (CDMA) system, both from the perspective of the maximum number of users that can be served at a required quality of service level and from the information theoretic perspective, has been recently shown to be achieved by the same joint transmit and receive strategies. In this paper, we propose an alternating minimization based iterative algorithm that updates the transmitters and the corresponding receivers of the users. The algorithm is suitable for online implementation, and the objective function is suitable for extension to multicell networks, both of which are in contrast with the previously proposed algorithms. We show that the algorithm is provably convergent to the optimum signature sequences and the corresponding receivers. Index Terms—Alternating minimization, codedivision multiple access (CDMA), mean squared error (MSE), optimum signature sequence sets, sum capacity, Welch bound equality (WBE) sequences. I.
A gametheoretic framework for interference avoidance in ad hoc networks
 in Global Telecommunications Conference, 2006. GLOBECOM ’06. IEEE
, 2005
"... It is shown in this paper that direct extensions of distributed greedy Interference Avoidance (IA) techniques for networks with centralized receivers to networks with multiple uncoordinated receivers (as in adhoc networks) do not always lead to convergence and some channel conditions that lead to n ..."
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Cited by 12 (2 self)
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It is shown in this paper that direct extensions of distributed greedy Interference Avoidance (IA) techniques for networks with centralized receivers to networks with multiple uncoordinated receivers (as in adhoc networks) do not always lead to convergence and some channel conditions that lead to nonconvergence are identified. A framework based on potential game theory is presented which could be used to construct convergent IA games in these decentralized networks. Example waveform adaptation games for IA are formulated according to this framework. It is shown that these convergent games lead to the maximization of global network objectives.