Optimal Pilot Pattern Design for LMMSE Channel Estimation in OFDM Systems with Finite Block Size over Doubly Dispersive Channels

TL;DR

This paper proposes heuristic algorithms for designing LMMSE-optimal pilot patterns in OFDM systems over doubly dispersive channels, outperforming traditional patterns in finite block scenarios.

Contribution

It formulates pilot pattern design as an A-optimal sensor selection problem and introduces two novel heuristic algorithms combining initialization and local refinement.

Findings

Proposed algorithms outperform conventional patterns in simulations.

Heuristic methods effectively optimize pilot placement for finite block OFDM.

Designs are suitable for high-mobility 5G-Advanced and 6G applications.

Abstract

Pilot pattern design over doubly dispersive channels has regained significant research interest, driven by emerging high-mobility applications in 5G-Advanced and 6G systems, as well as recent developments in Orthogonal Time Frequency Space (OTFS) modulation. This paper addresses the design of LMMSE-optimal pilot patterns for OFDM systems over doubly dispersive channels with finite time-frequency grids. We formulate the problem as A-optimal sensor selection and propose two heuristic algorithms, both combining an initialization stage with local swap refinement. The first employs convex relaxation with randomized rounding, while the second uses greedy selection. Simulations on practical resource block dimensions demonstrate that the proposed designs consistently outperform conventional rectangular and diamond lattice patterns.