18 research outputs found
A Unified Successive Pseudo-Convex Approximation Framework
In this paper, we propose a successive pseudo-convex approximation algorithm
to efficiently compute stationary points for a large class of possibly
nonconvex optimization problems. The stationary points are obtained by solving
a sequence of successively refined approximate problems, each of which is much
easier to solve than the original problem. To achieve convergence, the
approximate problem only needs to exhibit a weak form of convexity, namely,
pseudo-convexity. We show that the proposed framework not only includes as
special cases a number of existing methods, for example, the gradient method
and the Jacobi algorithm, but also leads to new algorithms which enjoy easier
implementation and faster convergence speed. We also propose a novel line
search method for nondifferentiable optimization problems, which is carried out
over a properly constructed differentiable function with the benefit of a
simplified implementation as compared to state-of-the-art line search
techniques that directly operate on the original nondifferentiable objective
function. The advantages of the proposed algorithm are shown, both
theoretically and numerically, by several example applications, namely, MIMO
broadcast channel capacity computation, energy efficiency maximization in
massive MIMO systems and LASSO in sparse signal recovery.Comment: submitted to IEEE Transactions on Signal Processing; original title:
A Novel Iterative Convex Approximation Metho
Multiuser MISO Transmitter Optimization for Inter-Cell Interference Mitigation
The transmitter optimization (i.e., steering vectors and power allocation)
for a MISO Broadcast Channel (MISO-BC) subject to general linear constraints is
considered. Such constraints include, as special cases, the sum power, the
per-antenna or per-group-of-antennas power, and "forbidden interference
direction" constraints. We consider both the optimal dirty-paper coding and the
simple suboptimal linear zero-forcing beamforming strategies, and provide
numerically efficient algorithms that solve the problem in its most general
form. As an application, we consider a multi-cell scenario with partial cell
cooperation, where each cell optimizes its precoder by taking into account
interference constraints on specific users in adjacent cells. The effectiveness
of the proposed methods is evaluated in a simple system scenario including two
adjacent cells, under different fairness criteria that emphasize the bottleneck
role of users near the cell "boundary". Our results show that "active"
Inter-Cell Interference (ICI) mitigation outperforms the conventional "static"
ICI mitigation based on fractional frequency reuse.Comment: 30 pages, 10 figures, and 1 table. revised and resubmitted to IEEE
Transactions on Signal Processin