Multipath signal propagation has long been viewed as an impairment to reliable communication in wireless channels. This paper shows that the presence of multipath greatly improves achievable data rate if appropriate structure is employed. A compact model developed for multiple-input multiple-output (MIMO) dispersive spatially selective channel. The multivariate information capacity analyzed. For high signal-to-noise ratio (SNR) conditions, MIMO channel can exhibit a slope bits per decibel...

This paper addresses the joint design of transmit and receive beamforming or linear processing (commonly termed precoding at transmitter equalization receiver) for multicarrier multiple-input multiple-output (MIMO) channels under a variety criteria. Instead considering each criterion in separate way, we generalize existing results by developing unified framework based on two families objective functions that embrace most reasonable criteria to communication system: Schur-concave Schur-convex...

This paper investigates the problem of dynamic multiuser subchannel allocation in downlink OFDM systems. The assumptions are that channel model is quasi-static and base station has perfect information. In traditional TDMA or FDMA systems, resource for each user non-adaptively fixed, water-filling power spectrum known to be optimal. Since allocations among users not optimized, a group likely suffer from poor gains resulting large path loss random fading. To resolve this problem, we derive...

In this paper, we present a finite-granularity, loading algorithm for discrete multitone (DMT) modulation system. The proposed offers significant implementational advantages over the well-known water-pouring method and earlier Hughes-Hartogs algorithm, while typically suffering only negligible performance degradation relative to optimal solution. We also simulation results of applied newly asymmetric digital subscriber lines (ADSL) service.< <ETX...

This paper proposes an efficient numerical algorithm to compute the optimal input distribution that maximizes sum capacity of a Gaussian multiple-access channel with vector inputs and output. The has iterative water-filling interpretation. converges from any starting point, it reaches within 1/2 nats per user output dimension after just one iteration. characterization also allows upper bound lower for entire region be derived.

This paper studies linear transmit filter design for Weighted Sum-Rate (WSR) maximization in the Multiple Input Output Broadcast Channel (MIMO-BC). The problem of finding optimal is non-convex and intractable to solve using low complexity methods. Motivated by recent results highlighting relationship between mutual information Minimum Mean Square Error (MMSE), this establishes a weighted sum-rate MMSE MIMO-BC. used propose two algorithms local optimum based on alternating optimization....

This paper considers the multiuser power control problem in a frequency-selective interference channel. The channel is modeled as noncooperative game, and existence uniqueness of Nash equilibrium are established for two-player version game. An iterative water-filling algorithm proposed to efficiently reach equilibrium. can be implemented distributively without need centralized control. It implicitly takes into account loop transfer functions cross couplings, it reaches competitively optimal...

This paper characterizes the sum capacity of a class potentially nondegraded Gaussian vector broadcast channels where single transmitter with multiple transmit terminals sends independent information to receivers. Coordination is allowed among terminals, but not receive terminals. The shown be saddle-point mutual game, signal player chooses covariance matrix maximize and fictitious noise correlation minimize information. achieved using precoding strategy for additive side noncausally known...

Fast transversal filter (FTF) implementations of recursive-least-squares (RLS) adaptive-filtering algorithms are presented in this paper. Substantial improvements transient behavior comparison to stochastic-gradient or LMS adaptive efficiently achieved by the algorithms. The true, not approximate, solution RLS problem is always obtained FTF even during critical initialization period (first N iterations) filter. This true recursively calculated at a relatively modest increase computational...

The minimum mean-squared-error decision-feedback equalizer (MMSE-DFE) has properties that suggest it is a canonical equalization structure for systems combine with coded modulation. and performance of the MMSE-DFE are succinctly derived using linear-estimation-theoretic principles in this first part two-part paper. front-end MMSE-DFE, called "mean-square whitened matched filter" (MS-WMF), preferable some ways to filter or as receiver front end. In system, feedback may be implemented...

Channel estimation for mobile OFDM systems requires transmission of pilot tones. This paper addresses the important issue selecting these tones, so as to achieve a good quality estimate. It is shown that best set tones be used are those which equally spaced. Furthermore, it using case first order Markov channel, more efficient use few in all symbols, rather than some symbols.

This paper proposes efficient rate and power allocation algorithms for OFDMA downlink systems where each tone is taken by at most one user. Weighted sum maximization (WSRmax) weighted minimization (WSPmin) problems are considered. Since these resource non-convex, complexity of finding the optimal solutions prohibitively high. employs Lagrange dual decomposition method to efficiently solve both optimization problems. Because their non-convex nature, there no guarantee solution obtained be...

A discrete multitone (DMT) transceiver design for high bit rate digital subscriber line (HDSL) access is presented and analyzed. The DMT transmitter receiver structure algorithms are detailed, the computational requirements of HDSL estimated. At a sampling 640 kHz, using an appropriate combination short finite-impulse-response (FIR) equalizer length-512 system, 1.6 Mb/s data transmission possible within carrier serving area (CSA) at error 10/sup -7/ on single twisted pair. significant...

This paper describes the "vectored" transmission technique for digital subscriber line (DSL) systems, which utilizes user coordination at central office or optical network unit. method exploits colocation of downstream transmitters and upstream receivers, in order to achieve far-end crosstalk (FEXT) cancellation perform multiuser optimization. The performance improvements are particularly pronounced environments with strong FEXT such as very high-speed DSL. Discrete multitone is employed...

This paper extends a number of results on the infinite-length minimum-mean-square-error decision Feedback equalizer (MMSE-DFE) reported by Cioffi, Dudevoir, Eyuboglu and Forney (see IEEE Trans. Commun., 1995) to finite-length case. Cholesky factorization displacement structure theory are demonstrated be two powerful analytical tools for analyzing MMSE-DFE. Our objective throughout is establish analogs well-known MMSE-DFE results. Similarities differences between cases examined delineated....

This correspondence studies the statistical distribution of signal-to-interference-plus-noise ratio (SINR) for minimum mean-square error (MMSE) receiver in multiple-input multiple-output (MIMO) wireless communications. The channel model is assumed to be (transmit) correlated Rayleigh flat-fading with unequal powers. SINR can decomposed into two independent random variables: SINR=SINR/sup ZF/+T, where SINR/sup ZF/ corresponds a zero-forcing (ZF) and has an exact Gamma distribution. focuses on...

A new criterion for partially-equalizing severe-ISI channels to reduce the cyclic prefix overhead of discrete multitone transceiver (DMT) is introduced. The equalized DMT shown recover a significant portion performance loss incurred because use moderate size FFT in latency and implementation cost. In particular, equalizers designed using are result higher margin than traditional mean-square-error equalizers. Finally, authors outline two additional promising methods enhance further DMT.

This paper proposes a numerical method for characterizing the rate region achievable with frequency-division multiple access (FDMA) Gaussian multiple-access channel intersymbol interference. The frequency spectrum is divided into discrete bins and bin-assignment problem shown to have convex relaxation, making it tractable optimization algorithms. A practical low-complexity algorithm two-user case also proposed. based on observation that optimal partition has two-band structure when two...

The effects of limited-precision errors in several popular adaptive-filtering algorithms are analyzed. Performance degradations caused by quantization internal algorithmic quantities often found to be much larger than what might otherwise expected. Furthermore, many cases, accumulate time without bound, leading an eventual overflow. This overflow is unacceptable phenomenon practice. Where possible, we list modifications the infinite-precision design criteria which prevent at expense a small...

A unified approach for computing the optimum settings of a length-N/sub f/ input-aided equalizer that minimizes mean-square error between equalized channel impulse response and target given length N/sub b/ is presented. This offers more insight into problem, easily accommodates correlation in input noise sequences, leads to significant computational savings, allows us analyze variety constraints on besides standard unit-tap constraint. In particular, we show imposing unit-energy constraint...

A compact model is derived for the multiple-input multiple output (MIMO), dispersive, spatially selective wireless communication channel. The multivariate information capacity behavior then analyzed various input and antenna configurations. For high SNR conditions, MIMO channel can exhibit a slope in bits per dB of power increase that proportional to minimum number multipath components, antennas, or antennas. discrete matrix multitone (DMMT) proposed as an asymptotically optimal, practical...

A linear technique for combining equalization and coset codes on partial response channels with additive white Gaussian noise is developed. The technique, vector coding, uses a set of transmit filters or 'vectors' to partition the channel into an independent parallel intersymbol interference (ISI)-free any given finite (or infinite) block length. optimal vectors such partitioning are shown be eigenvectors covariance matrix specified length, gains individual eigenvalues. An bit allocation...

Multicarrier basis functions and related issues are overviewed in this article with an emphasis on filtered multitone (FMT) modulation for VDSL. The combination of filtering, small amounts excess bandwidth, multicarrier channel partitioning, some equalization shown to allow a good match spectrum management performance challenges VDSL transmission. FMT basic the context filter banks, appropriate changes nonzero bandwidth.

This letter shows that the receiver processing of Vertical Bell Labs Layered Space-Time (V-BLAST) architecture may he viewed as a generalized decision feedback equalizer (GDFE) applied to multiple-input-multiple-output (MIMO) channel. It is proven that, depending on criterion chosen reduce interference, operations V-BLAST system are fundamentally equivalent either zero-forcing (ZF) or minimum-mean-square-error (MMSE) GDFE.