Multi-User MIMO Scheduling in the Fourth Generation Cellular Uplink

TL;DR

This paper addresses the complex problem of MU-MIMO scheduling in LTE-Advanced uplink, proposing approximation algorithms that efficiently optimize resource allocation under practical constraints.

Contribution

It formulates the MU-MIMO scheduling as a submodular maximization problem with constraints and introduces polynomial-time algorithms with proven approximation guarantees.

Findings

Proposed algorithms outperform existing methods in simulations.

The scheduling problem is NP-hard but can be approximated effectively.

Algorithms achieve near-optimal solutions within practical constraints.

Abstract

We consider Multi-User MIMO (MU-MIMO) scheduling in the 3GPP LTE-Advanced (3GPP LTE-A) cellular uplink. The 3GPP LTE-A uplink allows for precoded multi-stream (precoded MIMO) transmission from each scheduled user and also allows flexible multi-user (MU) scheduling wherein multiple users can be assigned the same time-frequency resource. However, exploiting these features is made challenging by certain practical constraints that have been imposed in order to maintain a low signaling overhead. We show that while the scheduling problem in the 3GPP LTE-A cellular uplink is NP-hard, it can be formulated as the maximization of a submodular set function subject to one matroid and multiple knapsack constraints. We then propose constant-factor polynomial-time approximation algorithms and demonstrate their superior performance via simulations.