Weak Interference Channel Research Articles

Robust Sum-GDoF of Symmetric 2 × 2 × 2 Weak Interference Channel With Heterogeneous Hops

The symmetric 2 × 2 × 2 weak interference channel setting with heterogeneous hops is explored from a Generalized Degrees of Freedom (GDoF) perspective, especially under the robust assumption that limits the channel state information at the transmitters (CSIT) to finite precision. Specifically, in the ℓ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>th</i></sup> hop, ℓ ∈ {1, 2}, both direct channels have strength α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> , both cross channels have strength β <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> (in logarithmic scale), and β <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> ≤ 0.5α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> . Thus, while assuming symmetry within each hop, the model allows heterogeneity across hops (α <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</sup> , β <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</sub> ) ≠ (α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</sub> , β <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</sub> ). Because β <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> ≤ 0.5α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> , each hop corresponds to an interference channel in the weak interference regime where power control and treating interference as noise are known to be sum-GDoF optimal in a 1-hop setting. The main result of this work is the exact sum-GDoF of the symmetric 2 × 2 × 2 weak interference channel for heterogeneous hops under finite precision CSIT. Compared to prior work that assumes homogeneous hops, heterogeneous hops require not only more sophisticated optimal rate-splitting arguments, but also quantize-and-forward ideas which were not needed for homogeneous hops. The converse proof similarly involves generalizations to accommodate hop heterogeneity, as well as new bounds beyond the homogeneous case, based on sum-set inequalities and aligned images arguments. Additional results include sum-GDoF for perfect CSIT, and for a natural dual strong interference setting where β <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> ≥ 2α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[ℓ]</sub> .

Another Perspective on Interference Channels for Non-Orthogonal Multiple Access Communications

In this letter, a new perspective on non-orthogonal multiple access (NOMA) is given, relying on the established model of interference channels (IC) from information theory. Establishing links with studies on ICs enables a new framework for the application of NOMA, especially in the context of distributed antenna systems. Thanks to this common framework, a fair and comprehensive evaluation of single antenna NOMA and IC-based NOMA is provided first. Then, a simple transmit coordination scheme, termed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">antenna switching</i> , is proposed to switch the IC scenario from strong to weak IC leading to an increase in the achievable capacity under some system and channel conditions. Finally an application example is provided to show the advantage of the proposed approach that enables to match the type of NOMA to the deployment context according to the desired trade off between system throughput and user fairness.

Maximizing the Minimum Achievable Secrecy Rate for a Two-User Gaussian Weak Interference Channel

This paper is a study of the Gaussian weak interference channel in which two single-antenna sources aim to send their messages to legitimate destinations such that all messages are kept confidential from non-intended receivers. Under the Gaussian codebook assumption, the problem of secrecy rate balancing with the objective of exploring the optimal power allocation policy at the sources in an attempt to maximize the minimum achievable secrecy rate is investigated, assuming each source is subject to a transmit power constraint. It is shown that at the optimal point, the two secrecy rates are equal; hence, the problem is abstracted to maximize the secrecy rate associated with one destination, while the other is restricted to having the same secrecy rate. The optimum secrecy rate associated with the investigated max–min problem is analytically derived, leading to the solution of the secrecy rate balancing problem. An additional scenario is considered in which sources can transmit artificial noise in addition to their signals. In this case, the max–min problem is solved and a suboptimal solution is provided. Numerical results show that the proposed solution is near-optimal and can be used as a suitable alternative.

Analysis of Capacity Bound on Two-User Transmitter Preprocessing Weak Interference MIMO Channels

In information theory (IT), it is an open problem for thirty years to establish an entire capacity bound of two-user Gaussian weak interference network. Under the assumption that channel situation information (CSI) is known at transmitter, we analyze the effects of three methods of transmitter preprocessing on performance of weak interference MIMO channels. Due to treat weak interference as noise, the bounds on the capacity region of two-user Gaussian weak interference channels (ICs) with the three transmitter preprocessing methods are derived. Compared with the performance without transmitter preprocessing, the sum rate in our system is larger. Finally the simulation results are proposed to be consistent with the theorem.