QoS Constrained Power Minimization in the Multiple Stream MIMO Broadcast Channel

TL;DR

This paper develops optimal linear transmit filters for MIMO broadcast channels with multiple streams per user, considering partial CSI at the transmitter, and introduces a gradient-based method for rate distribution among streams.

Contribution

It extends MIMO broadcast channel filter design to multiple streams per user with partial CSI, using MSE dualities and a projected gradient algorithm for rate allocation.

Findings

Effective filter design under partial CSI

Successful rate distribution among multiple streams

Enhanced power minimization in MIMO BC

Abstract

This work addresses the design of optimal linear transmit filters for the Multiple Input-Multiple Output (MIMO) Broadcast Channel (BC) when several spatial streams are allocated to each user.We also consider that the Channel State Information (CSI) is perfect at the receivers but is only partial at the transmitter. A statistical model for the partial CSI is assumed and exploited for the filter design. Similarly to the single-stream per user case, the problem is solved via Mean Square Error (MSE) dualities and interference functions. However, including more streams per user involves an additional complexity level since we must determine how to distribute the per-user rates among the streams. Such problem is solved using a projected gradient algorithm.