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

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...

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Veröffentlicht in:IEEE transactions on vehicular technology Jg. 69; H. 12; S. 15606 - 15622
Hauptverfasser: Thaj, Tharaj, Viterbo, Emanuele
Format: Journal Article
Sprache:Englisch
Veröffentlicht: New York IEEE 01.12.2020
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Schlagworte:
Complexity
Complexity theory
decoder
Delays
delay–doppler channel
detector
Detectors
DFE
Diversity reception
Error correcting codes
Error correction
Feedback
gauss seidel
Mathematical analysis
Matrix algebra
Matrix methods
maximal ratio combining
Message passing
Orthogonal Frequency Division Multiplexing
OTFS
Performance enhancement
rake
Receivers
Sensors
successive over-relaxation
Symbols
Time-domain analysis
Time-frequency analysis
turbo
ISSN:0018-9545, 1939-9359
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Zusammenfassung: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.
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ISSN:0018-9545
1939-9359
DOI:10.1109/TVT.2020.3044276