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68
Towards an Information Theory of Large Networks: An Achievable Rate Region
 IEEE Trans. Inform. Theory
, 2003
"... Abstract — We study communication networks of arbitrary size and topology and communicating over a general vector discrete memoryless channel. We propose an informationtheoretic constructive scheme for obtaining an achievable rate region in such networks. Many wellknown capacitydefining achievabl ..."
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Cited by 204 (12 self)
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Abstract — We study communication networks of arbitrary size and topology and communicating over a general vector discrete memoryless channel. We propose an informationtheoretic constructive scheme for obtaining an achievable rate region in such networks. Many wellknown capacitydefining achievable rate regions can be derived as special cases of the proposed scheme. A few such examples are the physically degraded and reverselydegraded relay channels, the Gaussian multipleaccess channel, and the Gaussian broadcast channel. The proposed scheme also leads to inner bounds for the multicast and allcast capacities. Applying the proposed scheme to a specific wireless network of nodes located in a region of unit area, we show that a transport capacity of ¡£ ¢ bitmeters/sec is feasible in a certain family of networks, as compared to the best possible transport capacity ¡£¢§ ¦ ¨ ¤ of bitmeters/sec in [16] where the receiver capabilities were limited. Even though the improvement is shown for a specific class of networks, a clear implication is that designing and employing more sophisticated multiuser coding schemes can provide sizable gains in at least some large wireless networks. Index Terms — Discrete memoryless channels, Gaussian channels, multiuser communications, network information theory,
Capacity and Optimal Resource Allocation for Fading Broadcast Channels: Part I: Ergodic Capacity
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A ratesplitting approach to the Gaussian multipleaccess channel
 IEEE TRANS. INFORM. THEORY
, 1996
"... It is shown that any point in the capacity region of a Gaussian multipleaccess channel is achievable by singleuser coding without requiring synchronization among users, provided that each user “splits” data and signal into two parts. Based on this result, a new multipleaccess technique called rat ..."
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Cited by 130 (2 self)
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It is shown that any point in the capacity region of a Gaussian multipleaccess channel is achievable by singleuser coding without requiring synchronization among users, provided that each user “splits” data and signal into two parts. Based on this result, a new multipleaccess technique called ratesplitting multiple accessing (RSMA) is proposed. RSMA is a codedivision multipleaccess scheme for the Muser Gaussian multipleaccess channel for which the effort of finding the codes for the M users, of encoding, and of decoding is that of at most 2M  1 independent pointtopoint Gaussian channels. The effects of bursty sources, multipath fading, and intercell interference are discussed and directions for further research are indicated.
Ratesplitting multiple access for discrete memoryless channels
 IEEE TRANSACTIONS ON INFORMATION THEORY
, 2001
"... It is shown that the encoding/decoding problem for any asynchronoususer discrete memoryless multipleaccess channel can be reduced to corresponding problems for at most 2M  1 singleuser discrete memoryless channels. This result, which extends a similar result for Gaussian channels, reduces the se ..."
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Cited by 51 (1 self)
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It is shown that the encoding/decoding problem for any asynchronoususer discrete memoryless multipleaccess channel can be reduced to corresponding problems for at most 2M  1 singleuser discrete memoryless channels. This result, which extends a similar result for Gaussian channels, reduces the seemingly hard task of finding good multipleaccess codes to the much better understood task of finding good codes for singleuser channels. As a byproduct, some interesting properties of the capacity region ofuser asynchronous discrete memoryless channels are derived.
Low density parity check codes for the relay channel
 IEEE J. SELECT. AREAS COMMUN
, 2007
"... We propose Low Density Parity Check (LDPC) code designs for the halfduplex relay channel. Our designs are based on the information theoretic random coding scheme for decodeandforward relaying. The source transmission is decoded with the help of side information in the form of additional parity b ..."
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Cited by 39 (1 self)
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We propose Low Density Parity Check (LDPC) code designs for the halfduplex relay channel. Our designs are based on the information theoretic random coding scheme for decodeandforward relaying. The source transmission is decoded with the help of side information in the form of additional parity bits from the relay. We derive the exact relationships that the component LDPC code profiles in the relay coding scheme must satisfy. These relationships act as constraints for the density evolution algorithm which is used to search for good relay code profiles. To speed up optimization, we outline a Gaussian approximation of density evolution for the relay channel. The asymptotic noise thresholds of the discovered relay code profiles are a fraction of a decibel away from the achievable lower bound for decodeandforward relaying. With random component LDPC codes, the overall relay coding scheme performs within 1.2 dB of the theoretical limit.
FDMACapacity of Gaussian MultipleAccess Channels with ISI
 IEEE Trans. Commun
, 2000
"... This paper proposes a numerical method for characterizing the rate region achievable with frequencydivision multiple access (FDMA) for a Gaussian multipleaccess channel with intersymbol interference. The frequency spectrum is divided into discrete frequency bins and the discrete binassignment pro ..."
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Cited by 35 (3 self)
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This paper proposes a numerical method for characterizing the rate region achievable with frequencydivision multiple access (FDMA) for a Gaussian multipleaccess channel with intersymbol interference. The frequency spectrum is divided into discrete frequency bins and the discrete binassignment problem is shown to have a convex relaxation, making it tractable to numerical optimization algorithms. A practical lowcomplexity algorithm for the twouser case is also proposed. The algorithm is based on the observation that the optimal frequency partition has a twoband structure when the two channels are identical or when the signaltonoise ratio is high. Simulation result shows that the algorithm performs well in other cases as well. The FDMAcapacity algorithm is used to devise the optimal frequencydivision duplex plan for veryhighspeed digital subscriber lines.
Design and Performance Analysis of Wireless Network
, 2000
"... In this thesis we are concerned with the problems of data transport in wireless networks. We study some issues related to the design and performance evaluation of multihop wireless networks, also known as ad hoc networks. The rst issue that we address is the power requirement for assuring connectivi ..."
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Cited by 22 (3 self)
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In this thesis we are concerned with the problems of data transport in wireless networks. We study some issues related to the design and performance evaluation of multihop wireless networks, also known as ad hoc networks. The rst issue that we address is the power requirement for assuring connectivity of wireless networks. Employing some results from continuum percolation theory, we obtain a precise characterization of the critical transmission range of nodes in a wireless network such that the network is connected with probability approaching one as the number of nodes increases. We next analyze the traÆccarrying capacity of multihop wireless networks. We show that under some noninterference models motivated by current technology, the average throughput obtained by nodes in a twodimensional wireless network decreases as the reciprocal of the square root of the number of nodes in the network. We also show that a similar cube root law holds for threedimensional wireless networks. In doing so, we determine the VapnikChervonenkis dimensions of certain geometric sets, which may be of independent interest. We also study wireless networks in a more informationtheoretic framework, which allows
A successive decoding strategy for channels with memory
 in Proc. IEEE International symposium on Information Theory
, 2005
"... Abstract — This paper presents both an information lossless coding scheme and a method to evaluate constrained capacity for channels with memory and unknown state. The fundamental idea is to decompose the original channel into a bank of memoryless subchannels with partially known states, then succe ..."
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Cited by 18 (4 self)
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Abstract — This paper presents both an information lossless coding scheme and a method to evaluate constrained capacity for channels with memory and unknown state. The fundamental idea is to decompose the original channel into a bank of memoryless subchannels with partially known states, then successively decode these subchannels. The receiver of each subchannel consists of an optimal estimator followed by a memoryless channel decoder. The coding scheme translates the codes and decoders designed for memoryless channels with near capacity performance to channels with memory. The results are applied to both finite state Markov channels and correlated flat fading channels. I. INTRODUCTION AND SUMMARY Many communication channels, including intersymbol interference (ISI) channels and correlated fading channels with
Design and performance of highspeed communication systems over timevarying radio channels
 ELEC. ENGIN. COMPUT. SCIENCE
, 1994
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Simultaneous Water Filling in Mutually Interfering Systems
 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS
, 2004
"... In this paper we investigate properties of simultaneous water filling for a wireless system with two mutually interfering transmitters and receivers with noncooperative coding strategies. This is slightly different from the traditional interference channel problem which assumes that transmitters co ..."
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Cited by 14 (0 self)
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In this paper we investigate properties of simultaneous water filling for a wireless system with two mutually interfering transmitters and receivers with noncooperative coding strategies. This is slightly different from the traditional interference channel problem which assumes that transmitters cooperate in their respective coding strategies, and that interference cancellation can be performed at the receivers. In this noncooperative setup, greedy capacity optimization by individual transmitters through various algorithms leads to simultaneous water filling fixed points where the spectrum of the transmit covariance matrix of one user water fills over the spectrum of its corresponding interferenceplusnoise covariance matrix, and in our paper we study the properties of these fixed points. We show that at a simultaneous water filling point the eigenvectors of transmit covariance matrices at each receiver are aligned, and identify three regimes which correspond to simultaneous water filling that depend on the interference gains: a) complete spectral overlap, b) partial spectral overlap, and c) spectral segregation. These imply that the transmit covariance matrices will be white in regions of both overlap and segregation, but not necessarily white overall. We also consider performance as a function of interference gain and show that complete spectral overlap is a strongly suboptimal solution over a wide range of gains. Overall,