Low Complexity Iterative Rake Decision Feedback Equalizer for Zero-Padded OTFS Systems

By Tharaj Thaj, Emanuele Viterbo. IEEE Transactions on Vehicular Technology, 2020

325 citations recorded by the source corpus.

This paper presents a linear complexity iterative rake detector for the recently proposed orthogonal time frequency space (OTFS) modulation scheme. The basic idea is to extract and coherently combine the received multipath components of the transmitted symbols in the delay-Doppler grid using maximal ratio combining (MRC) to improve the SNR of the combined signal. We reformulate the OTFS input-output relation in simple vector form by placing guard null symbols or zero padding (ZP) in the delay-Doppler grid and exploiting the resulting circulant property of the blocks of the channel matrix. Using this vector input-output relation we propose a low complexity iterative decision feedback equalizer (DFE) based on MRC. The performance and complexity of the proposed detector favorably compares with the state of the art message passing detector. An alternative time domain MRC based detector is also proposed for even faster detection. We further propose a Gauss-Seidel based over-relaxation parameter in the rake detector to improve the performance and the convergence speed of the iterative detection. We also show how the MRC detector can be combined with outer error-correcting codes to operate as a turbo DFE scheme to further improve the error performance. All results are compared with a baseline orthogonal frequency division multiplexing (OFDM) scheme employing a single tap minimum mean square error (MMSE) equalizer.

Subfields: Aerospace Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/0de792076a47fa4cfa2a79bc9bb20ac873a10623

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Citations in the corpus

Twelve Scientific Challenges for 6G: Rethinking the Foundations of Communications Theory (2022, methodology): “Researchers have been working on reducing the receiver’s complexity of the spreading waveforms [73], [74], by making approximation of the LMMSE matrix.”
A Primer on Rate-Splitting Multiple Access: Tutorial, Myths, and Frequently Asked Questions (2022, background): “The DD domain symbol multiplexing enables a direct coupling of the transmitted symbols with the channel’s delay-Doppler spread function, which has nice properties, such as quasi-static, compact, and sparse, to be exploited to achieve a low channel estimation overhead and full channel diversity with ”