# Direct Data Detection of OFDM Signals Over Wireless Channels

## TL;DR

This paper introduces a direct data detection (D^{3}) method for OFDM wireless signals that eliminates the need for channel estimation, achieving near-coherent performance with reduced complexity.

## Contribution

The paper proposes a novel receiver design that combines channel estimation, equalization, and data detection into a single operation for OFDM systems.

## Key findings

- D^{3} achieves BER within 3 dB of perfect CSI coherent detectors.
- D^{3} outperforms traditional coherent detectors when CSI is imperfect.
- Complexity can be significantly reduced using the Viterbi algorithm.

## Abstract

This paper presents a novel efficient receiver design for wireless communication systems that incorporate orthogonal frequency division multiplexing (OFDM) transmission. The proposed receiver does not require channel estimation or equalization to perform coherent data detection. Instead, channel estimation, equalization, and data detection are combined into a single operation, and hence, the detector is denoted as a direct data detector (D^{3}). The performance of the proposed system is thoroughly analyzed theoretically in terms of bit error rate (BER), and validated by Monte Carlo simulations. The obtained theoretical and simulation results demonstrate that the BER of the proposed D^{3} is only 3 dB away from coherent detectors with perfect knowledge of the channel state information (CSI) in flat fading channels, and similarly in frequency-selective channels for a wide range of signal-to-noise ratios (SNRs). If CSI is not known perfectly, then the D^{3} outperforms the coherent detector substantially, particularly at high SNRs with linear interpolation. The computational complexity of the D^{3} depends on the length of the sequence to be detected, nevertheless, a significant complexity reduction can be achieved using the Viterbi algorithm.