Angle-Domain Approach for Parameter Estimation in High-Mobility OFDM with Fully/Partly Calibrated Massive ULA

TL;DR

This paper presents an angle-domain method for estimating multiple Doppler and oscillator frequency offsets in high-mobility OFDM systems with massive ULA, improving accuracy in challenging wireless environments.

Contribution

It introduces a novel angle domain CFO estimation approach using high-resolution beamforming for both fully and partly calibrated ULAs, addressing inter-subarray mismatches.

Findings

Achieves accurate CFO estimation in high-mobility scenarios.

Provides theoretical analysis including MSE and Cramer-Rao bounds.

Demonstrates effectiveness through numerical simulations.

Abstract

In this paper, we consider a downlink orthogonal frequency division multiplexing (OFDM) system from a base station to a high-speed train (HST) equipped with fully/partly calibrated massive uniform linear antenna-array (ULA) in wireless environments with abundant scatterers. Multiple Doppler frequency offsets (DFOs) stemming from intensive propagation paths together with transceiver oscillator frequency offset (OFO) result in a fast time-varying frequency-selective channel. We develop an angle domain carrier frequency offset (CFO, general designation for DFO and OFO) estimation approach. A high-resolution beamforming network is designed to separate different DFOs into a set of parallel branches in angle domain such that each branch is mainly affected by a single dominant DFO. Then, a joint estimation algorithm for both maximum DFO and OFO is developed for fully calibrated ULA. Next, its estimation mean square error (MSE) performance is analyzed under inter-subarray mismatches. To mitigate the detrimental effects of inter-subarray mismatches, we introduce a calibration-oriented beamforming parameter (COBP) and develop the corresponding modified joint estimation algorithm for partly calibrated ULA. Moreover, the Cramer-Rao lower bound of CFO estimation is derived. Both theoretical and numerical results are provided to corroborate the proposed method.