A Semi-Blind Multiuser SIMO GFDM System in the Presence of CFOs and IQ Imbalances

TL;DR

This paper presents a low-complexity semi-blind joint estimation scheme for multiuser SIMO GFDM systems that effectively estimates channels, CFOs, and IQ imbalances, improving performance under various system configurations.

Contribution

It introduces a novel subspace-based semi-blind estimation method that handles multiple impairments without strict system constraints, outperforming existing techniques.

Findings

Significantly better bit error rate and outage probability

Accurate CFO, channel, and IQ imbalance estimation close to Cramer-Rao bounds

Applicable to a wide range of system configurations

Abstract

In this paper, we investigate an open topic of a multiuser single-input-multiple-output (SIMO) generalized frequency division multiplexing (GFDM) system in the presence of carrier frequency offsets (CFOs) and in-phase/quadrature-phase (IQ) imbalances. A low-complexity semi-blind joint estimation scheme of multiple channels, CFOs and IQ imbalances is proposed. By utilizing the subspace approach, CFOs and channels corresponding to U users are first separated into U groups. For each individual user, CFO is extracted by minimizing the smallest eigenvalue whose corresponding eigenvector is utilized to estimate channel blindly. The IQ imbalance parameters are estimated jointly with channel ambiguities by very few pilots. The proposed scheme is feasible for a wider range of receive antennas number and has no constraints on the assignment scheme of subsymbols and subcarriers, modulation type, cyclic prefix length and the number of subsymbols per GFDM symbol. Simulation results show that the proposed scheme significantly outperforms the existing methods in terms of bit error rate, outage probability, mean-square-errors of CFO estimation, channel and IQ imbalance estimation, while at much higher spectral efficiency and lower computational complexity. The Cramer-Rao lower bound is derived to verify the effectiveness of the proposed scheme, which is shown to be close to simulation results.