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

Thaj, Tharaj; Viterbo, Emanuele

doi:10.1109/tvt.2020.3044276

“…For BER plots, 10 5 frames are send for every point in the BER curve. In [13], it was shown that the proposed matched filtered GS algorithm in Section III-B can be implemented in the time domain in N M (2L + 1) complex multiplications per iteration. Moreover, in OTFS employing similar detector, taking the hard estimates between every iteration requires converting the timedomain samples to the delay-Doppler domain and replacing them with the nearest QAM symbol and then converting them back to get the improved time domain estimates.…”

Section: Simulation Results and Discussionmentioning

confidence: 99%

Orthogonal Time Sequency Multiplexing Modulation

Thaj¹,

Viterbo²

2021

Preprint

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This paper proposes <i>orthogonal time sequency multiplexing</i> (OTSM), a novel single carrier modulation scheme based on the well known Walsh-Hadamard transform (WHT) combined with row-column interleaving, and zero padding (ZP) between blocks in the time-domain. The information symbols in OTSM are multiplexed in the delay and sequency domain using a cascade of time-division and Walsh-Hadamard (sequency) multiplexing. By using the WHT for transmission and reception, the modulation and demodulation steps do not require any complex multiplications. We then propose two low-complexity detectors: (i) a simpler non-iterative detector based on a single tap minimum mean square time-frequency domain equalizer and (ii) an iterative time-domain detector. We demonstrate, via numerical simulations, that the proposed modulation scheme offers high performance gains over orthogonal frequency division multiplexing (OFDM) and exhibits the same performance of orthogonal time frequency space (OTFS) modulation, but with lower complexity. In proposing OTSM, along with simple detection schemes, we offer the lowest complexity solution to achieving reliable communication in high mobility wireless channels, as compared to the available schemes published so far in the literature.

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“…where is the relaxation parameter to improve the detector convergence for higher modulation schemes like 64-QAM, [29], [35], [36]. As initial estimates to the iterative detection, we chose X (0) = 0 × or the MMSE solution presented in [26] yielding faster convergence.…”

Section: Low-complexity Detectionmentioning

confidence: 99%

Orthogonal Time Sequency Multiplexing Modulation: Analysis and Low-Complexity Receiver Design

Thaj¹,

Viterbo²,

Hong³

2021

Preprint

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This paper proposes orthogonal time sequency multiplexing (OTSM), a novel single carrier modulation scheme that places information symbols in the delay-sequency domain followed by a cascade of time-division multiplexing (TDM) and Walsh-Hadamard sequence multiplexing. Thanks to the Walsh Hadamard transform (WHT), the modulation and demodulation do not require complex domain multiplications. For the proposed OTSM, we first derive the input-output relation in the delay-sequency domain and present a low complexity detection method taking advantage of zero-padding. We demonstrate via simulations that OTSM offers high performance gains over orthogonal frequency division multiplexing (OFDM) and similar performance to orthogonal time frequency space (OTFS), but at lower complexity owing to WHT. Then we propose a low complexity time-domain channel estimation method. Finally, we show how to include an outer error control code and a turbo decoder to improve error performance of the coded system.

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“…where δ is the relaxation parameter to improve the detector convergence for higher modulation schemes like 64-QAM, [13], [20], [21]. As initial estimate to the iterative detection, we can chose either X (0) = 0 or the MMSE solution in (21) yielding faster convergence.…”

Section: B Block-wise Time Domain Iterative Detectormentioning

confidence: 99%

“…1. Relation between the different discrete information symbol domains and the corresponding modulation schemes [6]- [13].…”

Section: Introductionmentioning

confidence: 99%

Orthogonal Time Sequency Multiplexing Modulation

Thaj¹,

Viterbo²

2021

Preprint

Self Cite

0

View full text Add to dashboard Cite

This paper proposes <i>orthogonal time sequency multiplexing</i> (OTSM), a novel single carrier modulation scheme based on the well known Walsh-Hadamard transform (WHT) combined with row-column interleaving, and zero padding (ZP) between blocks in the time-domain. The information symbols in OTSM are multiplexed in the delay and sequency domain using a cascade of time-division and Walsh-Hadamard (sequency) multiplexing. By using the WHT for transmission and reception, the modulation and demodulation steps do not require any complex multiplications. We then propose two low-complexity detectors: (i) a simpler non-iterative detector based on a single tap minimum mean square time-frequency domain equalizer and (ii) an iterative time-domain detector. We demonstrate, via numerical simulations, that the proposed modulation scheme offers high performance gains over orthogonal frequency division multiplexing (OFDM) and exhibits the same performance of orthogonal time frequency space (OTFS) modulation, but with lower complexity. In proposing OTSM, along with simple detection schemes, we offer the lowest complexity solution to achieving reliable communication in high mobility wireless channels, as compared to the available schemes published so far in the literature.

show abstract

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

Cited by 186 publications

References 21 publications

Orthogonal Time Sequency Multiplexing Modulation

Orthogonal Time Sequency Multiplexing Modulation

Orthogonal Time Sequency Multiplexing Modulation: Analysis and Low-Complexity Receiver Design

Orthogonal Time Sequency Multiplexing Modulation

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