Transmit Beamforming for MISO Broadcast Channels with Statistical and Delayed CSIT

TL;DR

This paper introduces the SAMAT transmission strategy for MISO broadcast channels that leverages statistical and delayed CSIT to optimize ergodic sum-rate, demonstrating significant performance improvements over existing methods.

Contribution

The paper proposes the SAMAT framework combining statistical beamforming and iterative precoding with power allocation for improved ergodic rate in MISO systems.

Findings

SAMAT outperforms SBF and AMAT in sum-rate performance.

Optimal power allocation enhances ergodic sum-rate.

The method is effective for arbitrary transmit antennas and SNR levels.

Abstract

This paper focuses on linear beamforming design and power allocation strategy for ergodic rate optimization in a two-user Multiple-Input-Single-Output (MISO) system with statistical and delayed channel state information at the transmitter (CSIT). We propose a transmission strategy, denoted as Statistical Alternative MAT (SAMAT), which exploits both channel statistics and delayed CSIT. Firstly, with statistical CSIT only, we focus on statistical beamforming (SBF) design that maximizes a lower bound on the ergodic sum-rate. Secondly, relying on both statistical and delayed CSIT, an iterative algorithm is proposed to compute the precoding vectors of Alternative MAT (AMAT), originally proposed by Yang et al., which maximizes an approximation of the ergodic sum-rate with equal power allocation. Finally, via proper power allocation, the SAMAT framework is proposed to softly bridge between SBF and AMAT for an arbitrary number of transmit antennas and signal-to-noise ratio (SNR). A necessary condition for the power allocation optimization is identified from the Karush-Kuhn-Tucker (KKT) conditions. The optimum power allocation to maximize an ergodic sum-rate approximation is computed using Sequential Quadratic Programming (SQP). Simulation results show that the proposed SAMAT scheme yields a significant sum-rate enhancement over both SBF and AMAT.