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797
Variablerate variablepower MQAM for fading channels.
 IEEE T. Commun.,
, 1997
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Reducing the peaktoaverage power ratio of multicarrier modulation by selected mapping,"
 IEE Electronics Letters,
, 1996
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OFDM with Reduced PeaktoAverage Power Ratio by Multiple Signal Representation
, 1997
"... In this paper two highly effective, flexible and distortionless peak power reduction schemes for Orthogonal Frequency Division Multiplexing (OFDM) with low amount of additional complexity and almost vanishing redundancy are presented. The schemes work with arbitrary numbers of subcarriers and signal ..."
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Cited by 182 (10 self)
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In this paper two highly effective, flexible and distortionless peak power reduction schemes for Orthogonal Frequency Division Multiplexing (OFDM) with low amount of additional complexity and almost vanishing redundancy are presented. The schemes work with arbitrary numbers of subcarriers and signal sets. The first approach generates a set of several alternative multicarrier signals and selects that transmit signal with the lowest peak power value. The second method optimally combines partial transmit sequences to minimize the peaktoaverage power ratio (PARcoefficient) . The schemes are analyzed theoretically and their performance is covered by simulations. 1 Introduction Even though there are many wellknown advantages of OFDM signaling [4], there are some limitations and complications in practice, when using OFDM transmission systems. The main problem is that the OFDM transmit signal exhibits a very high PARcoefficient. Therefore nonlinear characteristics are often overloa...
Adaptive resource allocation in multiuser OFDM systems with proportional rate constraints
 IEEE Trans. Wireless Commun
, 2005
"... Abstract—Multiuser orthogonal frequency division multiplexing (MUOFDM) is a promising technique for achieving high downlink capacities in future cellular and wireless local area network (LAN) systems. The sum capacity of MUOFDM is maximized when each subchannel is assigned to the user with the b ..."
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Cited by 127 (9 self)
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Abstract—Multiuser orthogonal frequency division multiplexing (MUOFDM) is a promising technique for achieving high downlink capacities in future cellular and wireless local area network (LAN) systems. The sum capacity of MUOFDM is maximized when each subchannel is assigned to the user with the best channeltonoise ratio for that subchannel, with power subsequently distributed by waterfilling. However, fairness among the users cannot generally be achieved with such a scheme. In this paper, a set of proportional fairness constraints is imposed to assure that each user can achieve a required data rate, as in a system with quality of service guarantees. Since the optimal solution to the constrained fairness problem is extremely computationally complex to obtain, a lowcomplexity suboptimal algorithm that separates subchannel allocation and power allocation is proposed. In the proposed algorithm, subchannel allocation is first performed by assuming an equal power distribution. An optimal power allocation algorithm then maximizes the sum capacity while maintaining proportional fairness. The proposed algorithm is shown to achieve about 95 % of the optimal capacity in a twouser system, while reducing the complexity from exponential to linear in the number of subchannels. It is also shown that with the proposed resource allocation algorithm, the sum capacity is distributed more fairly and flexibly among users than the sum capacity maximization method. Index Terms—Channel capacity, dynamic resource allocation, multiuser OFDM, proportional fairness, waterfilling. I.
A New Loading Algorithm For Discrete Multitone Transmission
, 1996
"... A new loading algorithm for discrete multitone transmission is proposed. Thereby rate is not distributed according to channel capacity, but rate and transmit power are assigned to maximize the signaltonoise ratio in each carrier. Because closed form expressions can be derived the algorithm is of v ..."
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Cited by 124 (19 self)
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A new loading algorithm for discrete multitone transmission is proposed. Thereby rate is not distributed according to channel capacity, but rate and transmit power are assigned to maximize the signaltonoise ratio in each carrier. Because closed form expressions can be derived the algorithm is of very low complexity, even lower than the loading algorithm recently proposed by Chow et al. [3]. Nevertheless achievable performance is higher or at least the same. Results for a typical high rate transmission over twisted pair lines are presented.
Adaptive Multicarrier Modulation: A Convenient Framework for TimeFrequency Processing in Wireless Communications
 Proc. IEEE
, 2000
"... This paper concludes with a wideranging throughput comparison of the schemes discussed herein under the unified constraint of a fixed target bit error rate of 10 04 . KeywordsAdaptive modulation, adaptive orthogonal frequency division multiplexing (AOFDM), applications of OFDM, blind modem m ..."
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Cited by 122 (10 self)
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This paper concludes with a wideranging throughput comparison of the schemes discussed herein under the unified constraint of a fixed target bit error rate of 10 04 . KeywordsAdaptive modulation, adaptive orthogonal frequency division multiplexing (AOFDM), applications of OFDM, blind modem mode detection in OFDM, broadcasting using OFDM, channel quality estimation in OFDM, coded OFDM (COFDM), coherent and noncoherent detection of OFDM, crest factor in OFDM, frequency and timing errors in OFDM, HIPERLAN, mode signaling in OFDM, multicarrier modulation, OFDM, peaktomean envelope fluctuation in OFDM, phase noise in OFDM, preequalization, synchronization in OFDM, throughput of adaptive OFDM, wireless asynchronous transfer mode (WATM) using OFDM, wireless localarea networks (WLAN's) using OFDM. I. INTRODUCTION Highdatarate communications are limited not only by noise butespecially with increasing symbol ratesoft
Design of a multiband OFDM system for realistic UWB channel environments
 IEEE Trans. Microwave Theory Tech
, 2004
"... Commission allocated 7500 MHz of spectrum for unlicensed use of commercial ultrawideband (UWB) communication devices. This spectral allocation has initiated an extremely productive activity for industry and academia. Wireless communications experts now consider UWB as available spectrum to be utili ..."
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Cited by 121 (0 self)
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Commission allocated 7500 MHz of spectrum for unlicensed use of commercial ultrawideband (UWB) communication devices. This spectral allocation has initiated an extremely productive activity for industry and academia. Wireless communications experts now consider UWB as available spectrum to be utilized with a variety of techniques, and not specifically related to the generation and detection of short RF pulses as in the past. There are many differences between realworld behavior of narrowband and UWB systems. All wireless systems must be able to deal with the challenges of operating over a multipath propagation channel, where objects in the environment can cause multiple reflections to arrive at the receiver (RX). For narrowband systems, these reflections will not be resolvable by the RX when the narrowband system bandwidth is less than the coherence bandwidth of the channel. The large bandwidth of
Optimum power allocation for parallel Gaussian channels with arbitrary input distributions
 IEEE TRANS. INF. THEORY
, 2006
"... The mutual information of independent parallel Gaussiannoise channels is maximized, under an average power constraint, by independent Gaussian inputs whose power is allocated according to the waterfilling policy. In practice, discrete signaling constellations with limited peaktoaverage ratios (m ..."
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Cited by 96 (10 self)
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The mutual information of independent parallel Gaussiannoise channels is maximized, under an average power constraint, by independent Gaussian inputs whose power is allocated according to the waterfilling policy. In practice, discrete signaling constellations with limited peaktoaverage ratios (mPSK, mQAM, etc.) are used in lieu of the ideal Gaussian signals. This paper gives the power allocation policy that maximizes the mutual information over parallel channels with arbitrary input distributions. Such policy admits a graphical interpretation, referred to as mercury/waterfilling, which generalizes the waterfilling solution and allows retaining some of its intuition. The relationship between mutual information of Gaussian channels and nonlinear minimum meansquare error (MMSE) proves key to solving the power allocation problem.
Adaptive coding for timevarying channels using outdated fading estimates,
 IEEE Trans. Commun.
, 1999
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Computationally efficient optimal power allocation algorithms for multicarrier communication systems
 IEEE Transactions on Communications
"... Abstract—In this paper, we present an optimal, computationally efficient, integerbit power allocation algorithm for discrete multitone modulation. Using efficient lookup table searches and a Lagrangemultiplier bisection search, our algorithm converges faster to the optimal solution than existing ..."
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Cited by 92 (1 self)
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Abstract—In this paper, we present an optimal, computationally efficient, integerbit power allocation algorithm for discrete multitone modulation. Using efficient lookup table searches and a Lagrangemultiplier bisection search, our algorithm converges faster to the optimal solution than existing techniques and can replace the use of suboptimal methods because of its low computational complexity. Fast algorithms are developed for the data rate and performance margin maximization problems. Index Terms—Discrete multitone modulation, loading algorithm, multicarrier communication systems, power allocation. I.