Blind Turbo Demodulation for Differentially Encoded OFDM with 2D Trellis Decomposition

2025-11-26

AI Summary

Blind demodulation of differential-encoded OFDM signals in DAB-like systems remains challenging due to the absence of pilot symbols, necessitating joint estimation of channel phase, gain, and noise variance without prior knowledge. Method: This paper proposes a fully blind Turbo-DE-PSK receiver that jointly estimates these parameters iteratively, integrating a novel two-dimensional trellis decomposition for high-accuracy blind phase estimation and power-statistics-based simultaneous estimation of channel gain and noise variance. The receiver tightly couples parameter estimation with Turbo decoding in an iterative architecture. Results: Simulation results demonstrate that the proposed scheme achieves performance close to the ideal case with perfect channel knowledge across diverse realistic channels and modulation configurations. It exhibits strong robustness against frequency offsets and multipath fading, significantly improving spectral efficiency and reception reliability compared to conventional approaches.

Technology Category

• Intelligent Robots: State Estimation
• Search and Optimization: Mixed Discrete/Continuous Search
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Security and Privacy: Large-scale security measurements

Abstract

Digital Audio Broadcasting (DAB)-like systems employ differentially encoded (DE) phase-shift keying (PSK) for transmission. While turbo-DE-PSK receivers offer substantial performance gains through iterative decoding by making the DE-PSK an inner code, they rely on accurate channel estimation without pilots, which is a key challenge in DAB-like scenarios. This paper develops a fully blind turbo-DE-PSK scheme that jointly estimates channel phase, channel gain, and noise variance directly from the received signal. The design leverages a two-dimensional (2D) trellis decomposition for blind phase estimation, complemented by power-based estimators for channel gain and noise variance. We provide a comprehensive system assessment across practical system parameters, including inner code length, phase quantization, and 2D block size. Simulation results show that the blind 2D turbo demodulator approaches the performance of receivers with perfect channel knowledge and remains robust under realistic transmission conditions.

Problem

• Developing blind turbo demodulation without pilots for differentially encoded OFDM systems
• Jointly estimating channel phase, gain and noise variance from received signals
• Overcoming channel estimation challenges in Digital Audio Broadcasting scenarios

Innovation

• Blind turbo-DE-PSK scheme jointly estimates channel parameters
• Uses 2D trellis decomposition for blind phase estimation
• Employs power-based estimators for gain and noise variance