Joint Coordinated Precoding and Discrete Rate Selection in Multicell MIMO Networks

TL;DR

This paper proposes a joint optimization framework for coordinated precoding and discrete rate selection in MIMO multicell networks, improving practical system performance by accurately modeling discrete modulation schemes.

Contribution

It introduces a novel optimization approach that accounts for discrete rates using a concave envelope, enabling a semi-distributed algorithm with proven convergence.

Findings

Significant performance gains over traditional Shannon rate-based methods

Effective handling of combinatorial and non-convex optimization challenges

Convergent resource allocation algorithm suitable for practical implementation

Abstract

Many practical wireless communications systems select their transmit rate from a finite set of modulation and coding schemes, which correspond to a set of discrete rates. In this paper, we therefore formulate a joint coordinated precoding and discrete rate selection problem for multiple-input multiple-output (MIMO) multicell networks. Compared to the common assumption of using the continuous Shannon rates as the user utilities, explicitly accounting for the discrete rates more accurately models practical wireless communication systems. The optimization problem that we formulate is combinatorial and non-convex, however, and is thus hard to solve. We therefore rewrite the problem using a discontinuous rate function, which we then bound using its concave envelope in some domain. Based on block coordinate descent, we provide a convergent resource allocation algorithm which can be implemented in a semi-distributed fashion. Numerical performance evaluation shows performance gains when the discrete rates are optimized using our model, as compared to the traditional methods which use the continuous Shannon rates as the user utilities.