Robust Rate Adaptation and Proportional Fair Scheduling with Imperfect CSI

TL;DR

This paper proposes robust rate adaptation and proportional fair scheduling methods that account for imperfect CSI and feedback delays in wireless systems, aiming to improve performance in practical, latency-sensitive applications.

Contribution

It introduces novel robust algorithms for rate adaptation and scheduling that explicitly handle CSI errors and delays, enhancing reliability and fairness in wireless communications.

Findings

Guarantees fixed target outage probability under CSI impairments

Improves system robustness against feedback delays

Enhances performance for delay-critical applications

Abstract

In wireless fading channels, multi-user scheduling has the potential to boost the spectral efficiency by exploiting diversity gains. In this regard, proportional fair (PF) scheduling provides a solution for increasing the users' quality of experience by finding a balance between system throughput maximization and user fairness. For this purpose, precise instantaneous channel state information (CSI) needs to be available at the transmitter side to perform rate adaptation and scheduling. However, in practical setups, CSI is impaired by, e.g., channel estimation errors, quantization and feedback delays. Especially in centralized cloud based communication systems, where main parts of the lower layer processing is shifted to a central entity, high backhaul latency can cause substantial CSI imperfections, resulting in significant performance degradations. In this work robust rate adaptation as well as robust PF scheduling are presented, which account for CSI impairments. The proposed rate adaptation solution guarantees a fixed target outage probability, which is of interest for delay critical and data intensive applications, such as, video conference systems. In addition to CSI imperfections the proposed scheduler is able to account for delayed decoding acknowledgements from the receiver.