Multi-User Pilot Pattern Optimization for Channel Extrapolation in 5G NR Systems

TL;DR

This paper introduces a novel multi-user pilot pattern optimization method for 5G NR OFDM systems, improving channel extrapolation by minimizing interference and enhancing delay resolution through an estimation of distribution algorithm.

Contribution

It formulates a new optimization problem for pilot pattern design considering ISL and SRL constraints, and extends it to multiband scenarios for better delay resolution.

Findings

Significant improvement in channel extrapolation accuracy.

Effective reduction of multi-user interference.

Enhanced delay resolution in multiband systems.

Abstract

Pilot pattern optimization in orthogonal frequency division multiplexing (OFDM) systems has been widely investigated due to its positive impact on channel estimation. In this paper, we consider the problem of multi-user pilot pattern optimization for OFDM systems. In particular, the goal is to enhance channel extrapolation performance for 5G NR systems by optimizing multi-user pilot patterns in frequency-domain. We formulate a novel pilot pattern optimization problem with the objective of minimizing the maximum integrated side-lobe level (ISL) among all users, subject to a statistical resolution limit (SRL) constraint. Unlike existing literature that only utilizes ISL for controlling side-lobe levels of the ambiguity function, we also leverage ISL to mitigate multi-user interference in code-domain multiplexing. Additionally, the introduced SRL constraint ensures sufficient delay resolution of the system to resolve multipath, thereby improving channel extrapolation performance. Then, we employ the estimation of distribution algorithm (EDA) to solve the formulated problem in an offline manner. Finally, we extend the formulated multi-user pilot pattern optimization problem to a multiband scenario, in which multiband gains can be exploited to improve system delay resolution. Simulation results demonstrate that the optimized pilot pattern yields significant performance gains in channel extrapolation over the conventional pilot patterns.