QoS Constrained Power Minimization in the MISO Broadcast Channel with Imperfect CSI

TL;DR

This paper proposes a method for designing linear precoders and receivers in a MISO broadcast channel to minimize transmit power while satisfying user QoS constraints, using MMSE constraints and MSE duality, with an AO algorithm.

Contribution

It introduces a novel approach combining MMSE constraints, MSE duality, and alternating optimization for power minimization under QoS constraints with imperfect CSI.

Findings

The proposed algorithm effectively minimizes power while meeting QoS requirements.

Feasibility analysis helps determine if QoS constraints can be satisfied.

An algorithm balances rates and handles unfeasible or high-power scenarios.

Abstract

We consider the design of linear precoders and receivers in a Multiple-Input Single-Output (MISO) Broadcast Channel (BC). We aim at minimizing the transmit power while fullfiling a set of per-user Quality-of-Service (QoS) constraints expressed in terms of per-user average rate requirements. The Channel State Information (CSI) is assumed to be perfectly known at the receivers but only partially at the transmitter. To solve the problem we transform the QoS constraints into Minimum Mean Square Error (MMSE) constraints. We then leverage the MSE duality between the BC and the Multiple Access Channel (MAC), as well as standard interference functions in the dual MAC, to perform power minimization by means of an Alternating Optimization (AO) algorithm. Problem feasibility is also studied to determine whether the QoS constraints can be fulfilled or not. Finally, we present an algorithm to balance the average rates and manage situations that may be unfeasible or lead to an unacceptably high transmit power.