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Capacity of Fading Channels with Channel Side Information
, 1997
"... We obtain the Shannon capacity of a fading channel with channel side information at the transmitter and receiver, and at the receiver alone. The optimal power adaptation in the former case is "waterpouring" in time, analogous to waterpouring in frequency for timeinvariant frequencysele ..."
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Cited by 429 (22 self)
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We obtain the Shannon capacity of a fading channel with channel side information at the transmitter and receiver, and at the receiver alone. The optimal power adaptation in the former case is "waterpouring" in time, analogous to waterpouring in frequency for timeinvariant frequencyselective fading channels. Inverting the channel results in a large capacity penalty in severe fading.
Fading Channels: InformationTheoretic And Communications Aspects
 IEEE TRANSACTIONS ON INFORMATION THEORY
, 1998
"... In this paper we review the most peculiar and interesting informationtheoretic and communications features of fading channels. We first describe the statistical models of fading channels which are frequently used in the analysis and design of communication systems. Next, we focus on the information ..."
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Cited by 306 (1 self)
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In this paper we review the most peculiar and interesting informationtheoretic and communications features of fading channels. We first describe the statistical models of fading channels which are frequently used in the analysis and design of communication systems. Next, we focus on the information theory of fading channels, by emphasizing capacity as the most important performance measure. Both singleuser and multiuser transmission are examined. Further, we describe how the structure of fading channels impacts code design, and finally overview equalization of fading multipath channels.
The effect upon channel capacity in wireless communications of perfect and imperfect knowledge of the channel
 IEEE Trans. Inf. Theory
, 2000
"... Abstract—We present a model for timevarying communication singleaccess and multipleaccess channels without feedback. We consider the difference between mutual information when the receiver knows the channel perfectly and mutual information when the receiver only has an estimate of the channel. We ..."
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Cited by 198 (4 self)
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Abstract—We present a model for timevarying communication singleaccess and multipleaccess channels without feedback. We consider the difference between mutual information when the receiver knows the channel perfectly and mutual information when the receiver only has an estimate of the channel. We relate the variance of the channel measurement error at the receiver to upper and lower bounds for this difference in mutual information. We illustrate the use of our bounds on a channel modeled by a Gauss–Markov process, measured by a pilot tone. We relate the rate of time variation of the channel to the loss in mutual information due to imperfect knowledge of the measured channel. Index Terms—Channel uncertainty, multipleaccess channels, mutual information, timevarying channels, wireless communications. I.
Communication over fading channels with delay constraints
 IEEE Transactions on Information Theory
, 2002
"... We consider a user communicating over a fading channel with perfect channel state information. Data is assumed to arrive from some higher layer application and is stored in a buffer until it is transmitted. We study adapting the user's transmission rate and power based on the channel state info ..."
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Cited by 179 (7 self)
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We consider a user communicating over a fading channel with perfect channel state information. Data is assumed to arrive from some higher layer application and is stored in a buffer until it is transmitted. We study adapting the user's transmission rate and power based on the channel state information as well as the buffer occupancy; the objectives are to regulate both the longterm average transmission power and the average buffer delay incurred by the traffic. Two models for this situation are discussed; one corresponding to fixedlength/variablerate codewords and one corresponding to variablelength codewords. The tradeoff between the average delay and the average transmission power required for reliable communication is analyzed. A dynamic programming formulation is given to find all Pareto optimal power/delay operating points. We then quantify the behavior of this tradeoff in the regime of asymptotically large delay. In this regime we characterize simple buffer control policies which exhibit optimal characteristics. Connections to the delaylimited capacity and the expected capacity of fading channels are also discussed.
Capacity of Rayleigh Fading Channels under Different Adaptive Transmission and . . .
 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
, 1999
"... We study the Shannon capacity of adaptive transmission techniques in conjunction with diversity combining. This capacity provides an upper bound on spectral efficiency using these techniques. We obtain closedform solutions for the Rayleigh fading channel capacity under three adaptive policies: opti ..."
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Cited by 103 (7 self)
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We study the Shannon capacity of adaptive transmission techniques in conjunction with diversity combining. This capacity provides an upper bound on spectral efficiency using these techniques. We obtain closedform solutions for the Rayleigh fading channel capacity under three adaptive policies: optimal power and rate adaptation, constant power with optimal rate adaptation, and channel inversion with fixed rate. Optimal power and rate adaptation yields a small increase in capacity over just rate adaptation, and this increase diminishes as the average received carriertonoise ratio (CNR) or the number of diversity branches increases. Channel inversion suffers the largest capacity penalty relative to the optimal technique, however, the penalty diminishes with increased diversity. Although diversity yields large capacity gains for all the techniques, the gain is most pronounced with channel inversion. For example, the capacity using channel inversion with twobranch diversity exceeds that of a singlebranch system using optimal rate and power adaptation. Since channel inversion is the least complex scheme to implement, there is a tradeoff between complexity and capacity for the various adaptation methods and diversitycombining techniques.
Adaptive Modulation over Nakagami Fading Channels
, 1998
"... We first study the capacity of Nakagami multipath fading (NMF) channels with an average power constraint for three power and rate adaptation policies. We obtain closedform solutions for NMF channel capacity for each power and rate adaptation strategy. Results show that rate adaptation is the key to ..."
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Cited by 92 (6 self)
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We first study the capacity of Nakagami multipath fading (NMF) channels with an average power constraint for three power and rate adaptation policies. We obtain closedform solutions for NMF channel capacity for each power and rate adaptation strategy. Results show that rate adaptation is the key to increasing link spectral efficiency. We analyze therefore the performance of constantpower variablerate MQAM schemes over NMF channels. We obtain closedform expressions for the outage probability, spectral efficiency and average biterrorrate (BER) assuming perfect channel estimation and negligible time delay. We also analyze the impact of time delay on the BER of adaptive MQAM. Keywords Link Spectral Efficiency, Adaptive Modulation Techniques, and Nakagami Fading. I. Introduction The radio spectrum available for wireless services is extremely scarce, while demand for these services is growing at a rapid pace [1]. Hence spectral efficiency is of primary concern in the design of fut...
Bandwidth Scaling for Fading Multipath Channels
, 1999
"... We show that very large bandwidths on fading multipath channels cannot be effectively utilized by spread spectrum systems that (in a particular sense) spread the available power uniformly over both time and frequency. The approach is to express the input process as an expansion in an orthonormal set ..."
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Cited by 87 (12 self)
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We show that very large bandwidths on fading multipath channels cannot be effectively utilized by spread spectrum systems that (in a particular sense) spread the available power uniformly over both time and frequency. The approach is to express the input process as an expansion in an orthonormal set of functions each localized in time and frequency. The fourth moment of each coefficient in this expansion is then uniformly constrained. We show that such a constraint forces the mutual information to 0 inversely with increasing bandwidth. Simply constraining the second moment of these coefficients does not achieve this effect. The results suggest strongly that conventional direct sequence CDMA systems do not scale well to extremely large bandwidths. To illustrate how the interplay between channel estimation and symbol detection affects capacity, we present results for a specific channel and CDMA signaling scheme.
Unified Design of Iterative Receivers Using Factor Graphs
 IEEE Trans. Inform. Theory
, 2001
"... Iterative algorithms are an attractive approach to approximating optimal, but highcomplexity, joint channel estimation and decoding receivers for communication systems. We present a unified approach based on factor graphs for deriving iterative messagepassing receiver algorithms for channel estima ..."
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Cited by 68 (0 self)
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Iterative algorithms are an attractive approach to approximating optimal, but highcomplexity, joint channel estimation and decoding receivers for communication systems. We present a unified approach based on factor graphs for deriving iterative messagepassing receiver algorithms for channel estimation and decoding. For many common channels, it is easy to find simple graphical models that lead directly to implementable algorithms. Canonical distributions provide a new, general framework for handling continuous variables. Example receiver designs for Rayleigh fading channels with block or Markov memory, and multipath fading channels with fixed unknown coe#cients illustrate the e#ectiveness of our approach. Keywords channel estimation; fading channels; iterative decoding; lowdensity parity check (LDPC) codes I. Introduction For many communication systems it is wellknown that joint demodulation and decoding is required for optimum performance. Typically, this processing is too co...
Pilot Assisted Wireless Transmissions
 IEEE Signal Processing Mag
, 2004
"... The design of pilot assisted wireless transmissions is considered from signal processing and information theoretical perspectives. A general pilot placement model is presented and related figures of merit discussed. A survey of recent pilot assisted transmission theory and techniques is provided. ..."
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Cited by 45 (2 self)
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The design of pilot assisted wireless transmissions is considered from signal processing and information theoretical perspectives. A general pilot placement model is presented and related figures of merit discussed. A survey of recent pilot assisted transmission theory and techniques is provided.
SpaceTime Autocoding
 IEEE Trans. Inform. Theory
, 1999
"... Prior treatments of spacetime communications in Rayleigh flat fading generally assume that channel coding covers either one fading intervalin which case there is a nonzero "outage capacity"or multiple fading intervalsin which case there is a nonzero Shannon capacity. However, we ..."
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Cited by 30 (3 self)
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Prior treatments of spacetime communications in Rayleigh flat fading generally assume that channel coding covers either one fading intervalin which case there is a nonzero "outage capacity"or multiple fading intervalsin which case there is a nonzero Shannon capacity. However, we establish conditions under which channel codes span only one fading interval and yet are arbitrarily reliable. In short, spacetime signals are their own channel codes. We call this phenomenon spacetime autocoding, and the accompanying capacity the spacetime autocapacity. Let an Mtransmitterantenna, Nreceiverantenna Rayleigh flat fading channel be characterized by an M \Theta N matrix of independent propagation coefficients, distributed as zeromean, unitvariance complex Gaussian random variables. This propagation matrix is unknown to the transmitter, it remains constant during a T symbol coherence interval, and there is a fixed total transmit power. Let the coherence interval and number of ...