arXiv subjects

Biao Chen

Publications and source records attributed to Biao Chen.

52 records · Page 3Linked to original sources

arXiv2012

On the Sum Capacity of the Discrete Memoryless Interference Channel with One-Sided Weak Interference and Mixed Interference

The sum capacity of a class of discrete memoryless interference channels is determined. This class of channels is defined analogous to the Gaussian Z-interference channel with weak interference; as a result, the sum capacity is achieved by letting the transceiver pair subject to the interference communicates at a rate such that its message can be decoded at the unintended receiver using single user detection. Moreover, this class of discrete memoryless interference channels is equivalent in capacity region to certain discrete degraded interference channels. This allows the construction of a capacity outer-bound using the capacity region of associated degraded broadcast channels. The same technique is then used to determine the sum capacity of the discrete memoryless interference channel with mixed interference. The above results allow one to determine sum capacities or capacity regions of several new discrete memoryless interference channels.

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arXiv2010

The Common Information of N Dependent Random Variables

This paper generalizes Wyner's definition of common information of a pair of random variables to that of $N$ random variables. We prove coding theorems that show the same operational meanings for the common information of two random variables generalize to that of $N$ random variables. As a byproduct of our proof, we show that the Gray-Wyner source coding network can be generalized to $N$ source squences with $N$ decoders. We also establish a monotone property of Wyner's common information which is in contrast to other notions of the common information, specifically Shannon's mutual information and Gács and Körner's common randomness. Examples about the computation of Wyner's common information of $N$ random variables are also given.

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arXiv2009

MIMO Z-Interference Channels: Capacity Under Strong and Noisy Interference

The capacity regions of multiple-input multiple-output Gaussian Z-interference channels are established for the very strong interference and aligned strong interference cases. The sum-rate capacity of such channels is established under noisy interference. These results generalize known results for scalar Gaussian Z-interference channels.

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arXiv2009

Interference Channels With Arbitrarily Correlated Sources

Communicating arbitrarily correlated sources over interference channels is considered in this paper. A sufficient condition is found for the lossless transmission of a pair of correlated sources over a discrete memoryless interference channel. With independent sources, the sufficient condition reduces to the Han-Kobayashi achievable rate region for the interference channel. For a special correlation structure (in the sense of Slepian-Wolf, 1973), the proposed region reduces to the known achievable region for interference channels with common information. A simple example is given to show that the separation approach, with Slepian-Wolf encoding followed by optimal channel coding, is strictly suboptimal.

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arXiv2009

Capacity Bounds for Two-Hop Interference Networks

This paper considers a two-hop interference network, where two users transmit independent messages to their respective receivers with the help of two relay nodes. The transmitters do not have direct links to the receivers; instead, two relay nodes serve as intermediaries between the transmitters and receivers. Each hop, one from the transmitters to the relays and the other from the relays to the receivers, is modeled as a Gaussian interference channel, thus the network is essentially a cascade of two interference channels. For this network, achievable symmetric rates for different parameter regimes under decode-and- forward relaying and amplify-and-forward relaying are proposed and the corresponding coding schemes are carefully studied. Numerical results are also provided.

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arXiv2009

Interference Channels with One Cognitive Transmitter

This paper studies the problem of interference channels with one cognitive transmitter (ICOCT) where "cognitive" is defined from both the noncausal and causal perspectives. For the noncausal ICOCT, referred to as interference channels with degraded message sets (IC-DMS), we propose a new achievable rate region that generalizes existing achievable rate regions for IC-DMS. In the absence of the noncognitive transmitter, the proposed region coincides with Marton's region for the broadcast channel. Based on this result, the capacity region of a class of semi-deterministic IC-DMS is established. For the causal ICOCT, due to the complexity of the channel model, we focus primarily on the cognitive Z interference channel (ZIC), where the interference link from the cognitive transmitter to the primary receiver is assumed to be absent due to practical design considerations. Capacity bounds for such channels in different parameter regimes are obtained and the impact of such causal cognitive ability is carefully studied. In particular, depending on the channel parameters, the cognitive link may not be useful in terms of enlarging the capacity region. An optimal corner point of the capacity region is also established for the cognitive ZIC for a certain parameter regime.

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arXiv2009

On the Optimality of Beamforming for Multi-User MISO Interference Channels with Single-User Detection

For a multi-user interference channel with multi-antenna transmitters and single-antenna receivers, by restricting each receiver to a single-user detector, computing the largest achievable rate region amounts to solving a family of non-convex optimization problems. Recognizing the intrinsic connection between the signal power at the intended receiver and the interference power at the unintended receiver, the original family of non-convex optimization problems is converted into a new family of convex optimization problems. It is shown that, for such interference channels with each receiver implementing single-user detection, transmitter beamforming can achieve all boundary points of the achievable rate region.

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arXiv2009

Multi-User MISO Interference Channels with Single-User Detection: Optimality of Beamforming and the Achievable Rate Region

For a multi-user interference channel with multi-antenna transmitters and single-antenna receivers, by restricting each transmitter to Gaussian input and each receiver to a single-user detector, computing the largest achievable rate region amounts to solving a family of non-convex optimization problems. Recognizing the intrinsic connection between the signal power at the intended receiver and the interference power at the unintended receiver, the original family of non-convex optimization problems is converted into a new family of convex optimization problems. It is shown that, for such interference channels with each receiver implementing single-user detection, transmitter beamforming can achieve all boundary points of the achievable rate region.

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arXiv2009

Capacity Regions and Sum-Rate Capacities of Vector Gaussian Interference Channels

The capacity regions of vector, or multiple-input multiple-output, Gaussian interference channels are established for very strong interference and aligned strong interference. Furthermore, the sum-rate capacities are established for Z interference, noisy interference, and mixed (aligned weak/intermediate and aligned strong) interference. These results generalize known results for scalar Gaussian interference channels.

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arXiv2009

Noisy-interference Sum-rate Capacity of Parallel Gaussian Interference Channels

The sum-rate capacity of the parallel Gaussian interference channel is shown to be achieved by independent transmission across sub-channels and treating interference as noise in each sub-channel if the channel coefficients and power constraints satisfy a certain condition. The condition requires the interference to be weak, a situation commonly encountered in, e.g., digital subscriber line transmission. The optimal power allocation is characterized by using the concavity of sum-rate capacity as a function of the power constraints.

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arXiv2008

On the Capacity of MIMO Interference Channels

The capacity region of a multiple-input-multiple-output interference channel (MIMO IC) where the channel matrices are square and invertible is studied. The capacity region for strong interference is established where the definition of strong interference parallels that of scalar channels. Moreover, the sum-rate capacity for Z interference, noisy interference, and mixed interference is established. These results generalize known results for the scalar Gaussian IC.

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arXiv2008

Capacity Bounds for Broadcast Channels with Confidential Messages

In this paper, we study capacity bounds for discrete memoryless broadcast channels with confidential messages. Two private messages as well as a common message are transmitted; the common message is to be decoded by both receivers, while each private message is only for its intended receiver. In addition, each private message is to be kept secret from the unintended receiver where secrecy is measured by equivocation. We propose both inner and outer bounds to the rate equivocation region for broadcast channels with confidential messages. The proposed inner bound generalizes Csiszár and Körner's rate equivocation region for broadcast channels with a single confidential message, Liu {\em et al}'s achievable rate region for broadcast channels with perfect secrecy, Marton's and Gel'fand and Pinsker's achievable rate region for general broadcast channels. Our proposed outer bounds, together with the inner bound, helps establish the rate equivocation region of several classes of discrete memoryless broadcast channels with confidential messages, including less noisy, deterministic, and semi-deterministic channels. Furthermore, specializing to the general broadcast channel by removing the confidentiality constraint, our proposed outer bounds reduce to new capacity outer bounds for the discrete memory broadcast channel.

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arXiv2008

New Outer Bounds on the Capacity Region of Gaussian Interference Channels

Recent outer bounds on the capacity region of Gaussian interference channels are generalized to $m$-user channels with $m>2$ and asymmetric powers and crosstalk coefficients. The bounds are again shown to give the sum-rate capacity for Gaussian interference channels with low powers and crosstalk coefficients. The capacity is achieved by using single-user detection at each receiver, i.e., treating the interference as noise incurs no loss in performance.

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arXiv2007

A New Outer Bound and the Noisy-Interference Sum-Rate Capacity for Gaussian Interference Channels

A new outer bound on the capacity region of Gaussian interference channels is developed. The bound combines and improves existing genie-aided methods and is shown to give the sum-rate capacity for noisy interference as defined in this paper. Specifically, it is shown that if the channel coefficients and power constraints satisfy a simple condition then single-user detection at each receiver is sum-rate optimal, i.e., treating the interference as noise incurs no loss in performance. This is the first concrete (finite signal-to-noise ratio) capacity result for the Gaussian interference channel with weak to moderate interference. Furthermore, for certain mixed (weak and strong) interference scenarios, the new outer bounds give a corner point of the capacity region.

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arXiv2007

An Achievable Rate Region for the Gaussian Interference Channel

An achievable rate region for the Gaussian interference channel is derived using Sato's modified frequency division multiplexing idea and a special case of Han and Kobayashi's rate region (denoted by $\Gmat^\prime$). We show that the new inner bound includes $\Gmat^\prime$, Sason's rate region $\Dmat$, as well as the achievable region via TDM/FDM, as its subsets. The advantage of this improved inner bound over $\Gmat^\prime$ arises due to its inherent ability to utilize the whole transmit power range on the real line without violating the power constraint. We also provide analysis to examine the conditions for the new achievable region to strictly extend $\Gmat^\prime$.

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arXiv2007

An Achievable Rate Region for Interference Channels with Conferencing

In this paper, we propose an achievable rate region for discrete memoryless interference channels with conferencing at the transmitter side. We employ superposition block Markov encoding, combined with simultaneous superposition coding, dirty paper coding, and random binning to obtain the achievable rate region. We show that, under respective conditions, the proposed achievable region reduces to Han and Kobayashi achievable region for interference channels, the capacity region for degraded relay channels, and the capacity region for the Gaussian vector broadcast channel. Numerical examples for the Gaussian case are given.

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