Performance and Compensation of I/Q Imbalance in Differential STBC-OFDM

TL;DR

This paper investigates the impact of I/Q imbalance on differential STBC-OFDM systems and introduces an adaptive, decision-directed compensation algorithm that effectively mitigates IQ imbalance without requiring training sequences.

Contribution

It presents a novel adaptive decision-directed IQ imbalance compensation algorithm for differential STBC-OFDM that reduces training overhead and improves system robustness.

Findings

The proposed algorithm effectively mitigates receiver IQI effects.

Simulation results show significant performance improvement.

The method operates without known pilots or training sequences.

Abstract

Differential space time block coding (STBC) achieves full spatial diversity and avoids channel estimation overhead. Over highly frequency-selective channels, STBC is integrated with orthogonal frequency division multiplexing (OFDM) to achieve high performance. However, low-cost implementation of differential STBC-OFDM using direct-conversion transceivers is sensitive to In-phase/Quadrature-phase imbalance (IQI). In this paper, we quantify the performance impact of IQI at the receiver front-end on differential STBC-OFDM systems and propose a compensation algorithm to mitigate its effect. The proposed receiver IQI compensation works in an adaptive decision-directed manner without using known pilots or training sequences, which reduces the rate loss due to training overhead. Our numerical results show that our proposed compensation algorithm can effectively mitigate receive IQI in differential STBC-OFDM.