Channel Independent Precoder for OFDM-based Systems over Fading Channels

TL;DR

This paper introduces a novel channel-independent precoder for OFDM systems that reduces noise variance caused by fading, adaptable to channel conditions, and compatible with a modified Zero Forcing equalizer.

Contribution

The proposed precoder design is independent of channel state information and improves noise variance management in OFDM systems over fading channels.

Findings

Reduces instantaneous noise power variance.

Allows flexible time-frequency diversity configurations.

Enhances performance with a clipped Zero Forcing equalizer.

Abstract

In this paper we propose an independent channel precoder for orthogonal frequency division multiplexing (OFDM) systems over fading channels. The design of the precoder is based on the information redistribution of the input modulated symbols amongst the output precoded symbols. The proposed precoder decreases the variance of the instantaneous noise power at the receiver produced by the channel variability. The employment of an interleaver together with a precoding matrix whose size does not depend on the number of data carriers in an OFDM symbol allows different configurations of time-frequency diversity which can be easily adapted to the channel conditions. The precoder is evaluated with a modified Zero Forcing (ZF) equalizer whose maximum gain is constrained by means of a clipping factor. Thus, the clipping factor limits the noise power transfer in the receiver deprecoding block in low SNR conditions.