Non-Redundant OFDM Receiver Windowing for 5G Frames & Beyond

TL;DR

This paper introduces a low-complexity, backward-compatible Hann windowed OFDM scheme that enhances adjacent channel interference rejection without additional redundancies, improving performance in high mobility scenarios.

Contribution

A novel Hann RW-OFDM scheme is proposed that improves ACI rejection while maintaining compatibility with existing standards and requiring no extra redundancies.

Findings

Superior ACI rejection in high delay spread environments.

Comparable computational complexity to existing algorithms.

Enhanced bit-error rate performance in various delay conditions.

Abstract

Contemporary receiver windowed orthogonal frequency division multiplexing (RW-OFDM) algorithms have limited adjacent channel interference (ACI) rejection capability under high delay spread and small Fast Fourier Transform (FFT) sizes. Cyclic prefix (CP) is designed to be longer than the maximum excess delay (MED) of the channel to accommodate such algorithms in current standards. The robustness of these algorithms can only be improved against these conditions by adopting additional extensions in a new backward incompatible standard. Such extensions would deteriorate the performance of high mobility vehicular communication systems in particular. In this paper, we present a low-complexity Hann RW-OFDM scheme that provides resistance against ACI without requiring any intersymbol interference (ISI)-free redundancies. While this scheme is backward compatible with current and legacy standards and requires no changes to the conventionally transmitted signals, it also paves the way towards future spectrotemporally localized and efficient schemes suitable for higher mobility vehicular communications. A Hann window effectively rejects unstructured ACI at the expense of structured and limited intercarrier interference (ICI) across data carriers. A simple maximum ratio combining successive interference cancellation (MRC-SIC) receiver is therefore proposed to resolve this induced ICI and receive symbols transmitted by standard transmitters currently in use. The computational complexity of the proposed scheme is comparable to that of contemporary RW-OFDM algorithms, while ACI rejection and bit-error rate performance is superior in both long and short delay spreads. Channel estimation using Hann RW-OFDM symbols is also discussed.