Low-complexity iterative detection for orthogonal time frequency space modulation

Raviteja, P.; Phan, Khoa T.; Jin, Qianyu; Hong, Yi; Viterbo, Emanuele

doi:10.1109/wcnc.2018.8377159

Cited by 123 publications

(110 citation statements)

References 9 publications

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“…2) Fractional Doppler shifts: Similarly, the following result was derived in [4] for the fractional Doppler case…”

Section: ) Integer Doppler Shiftsmentioning

confidence: 85%

“…for k ∈ [0, N − 1] and l [l p , l p + l τ ]. Now we can adapt the MP algorithm in [4] for data detection in (9). Note that, to guarantee no interference between the received symbols for channel estimation and data detection, the guard symbols need to expand over a wider range over the Doppler axis, when compared to the integer Doppler case.…”

Section: B the Fractional Doppler Casementioning

confidence: 99%

“…for data detection via a message passing (MP) algorithm in [4]. Depending on the channel and symbol arrangement, the threshold is chosen to optimize the estimation accuracy.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Embedded Pilot-Aided Channel Estimation for OTFS in Delay–Doppler Channels

Raviteja

Phan

Hong

2019

IEEE Trans. Veh. Technol.

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473

445

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Orthogonal time frequency space (OTFS) modulation was shown to provide significant error performance advantages over orthogonal frequency division multiplexing (OFDM) in delay-Doppler channels. In order to detect OTFS modulated data, the channel impulse response needs to be known at the receiver. In this paper, we propose embedded pilot-aided channel estimation schemes for OTFS. In each OTFS frame, we arrange pilot, guard, and data symbols in the delay-Doppler plane to suitably avoid interference between pilot and data symbols at the receiver. We develop such symbol arrangements for OTFS over multipath channels with integer and fractional Doppler shifts, respectively. At the receiver, channel estimation is performed based on a threshold method and the estimated channel information is used for data detection via a message passing (MP) algorithm. Thanks to our specific embedded symbol arrangements, both channel estimation and data detection are performed within the same OTFS frame with a minimum overhead. We compare by simulations the error performance of OTFS using the proposed channel estimation and OTFS with ideally known channel information and observe only a marginal performance loss. We also demonstrate that the proposed channel estimation in OTFS significantly outperforms OFDM with known channel information. Finally, we present extensions of the proposed schemes to MIMO and multi-user uplink/downlink.

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“…2) Fractional Doppler shifts: Similarly, the following result was derived in [4] for the fractional Doppler case…”

Section: ) Integer Doppler Shiftsmentioning

confidence: 85%

Section: B the Fractional Doppler Casementioning

confidence: 99%

See 1 more Smart Citation

Embedded Pilot-Aided Channel Estimation for OTFS in Delay–Doppler Channels

Raviteja

Phan

Hong

2019

IEEE Trans. Veh. Technol.

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473

445

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“…We follow the notations in [5], [13] summarized below: -The time-frequency signal plane is discretized to a grid by sampling time and frequency axes at intervals T (seconds) and ∆f (Hz), respectively, i.e., Λ = (nT, m∆f ), n = 0, . .…”

Section: A Basic Otfs Concepts/notationsmentioning

confidence: 99%

“…k−kν i +q] i N x [[k − k ν i + q] N , [l − l τ i ] M ] l < l τ i , 2: OTFS INPUT-OUTPUT RELATION IN DELAY-DOPPLER DOMAIN FOR IDEAL PULSESThe received signal y[k, l] for the ideal pulses, from(11) and(13), can be written asy[k, l] n,m [n, m]X[n, m]e −j2π nk N − ml M .By substituting the ISFFT equation from(2), y[k, l] can be expanded as in from(51) to (53).Here, h w [k − k ′ , l − l ′ ] can be seen as the value of h w (ν, τ ) sampled at ν = k−k ′ N T , τ = l−l ′ M ∆f .The value of h w (ν, τ ) can be obtained as from(54)to (56), by substituting H n,m [n, m] from (10), which completes the proof. APPENDIX C PROOF OF THEOREM 2: OTFS INPUT-OUTPUT RELATION IN DELAY-DOPPLER DOMAIN FOR RECTANGULAR PULSES We start with expanding y[k, l] in (11) using the Y [n, m] for rectangular pulses in (24) as in (57).…”

mentioning

confidence: 99%

Interference Cancellation and Iterative Detection for Orthogonal Time Frequency Space Modulation

Raviteja

Phan

Hong

et al. 2018

IEEE Trans. Wireless Commun.

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697

599

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The recently proposed orthogonal time frequency space (OTFS) modulation technique was shown to provide significant error performance advantages over orthogonal frequency division multiplexing (OFDM) in Doppler channels. In this paper, we first derive the explicit input-output relation describing OTFS modulation and demodulation (mod/demod) for delay-Doppler channels. We then analyze the cases of (i) ideal pulse-shaping waveforms that satisfy the bi-orthogonality conditions, and (ii) rectangular waveforms which do not. We show that while only inter-Doppler interference (IDI) is present in the first case, additional inter-carrier interference (ICI) and inter-symbol interference (ISI) occur in the second case. We next analyze the interferences and develop a novel low-complexity yet efficient message passing (MP) algorithm for joint interference cancellation (IC) and symbol detection. While ICI and ISI are eliminated through appropriate phase shifting, IDI can be mitigated by adapting the MP algorithm to account for only the largest interference terms. The proposed MP algorithm can effectively compensate for a wide range of channel Doppler spreads. Our results indicate that OTFS using practical rectangular waveforms can achieve the performance of OTFS using ideal but non-realizable pulseshaping waveforms. Finally, simulations results demonstrate the superior error performance gains of the proposed uncoded OTFS schemes over OFDM under various channel conditions.

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Advanced OTFS communication system with compact spectrum and power efficiency improvement

Hossain

Ryu

2021

Int J Communication

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Orthogonal time frequency space (OTFS) modulation technique is one-step more precoded system of the conventional orthogonal frequency division multiplexing (OFDM) system, i.e., a double precoded system. The OTFS system was suggested especially for the robust and reliable high-speed vehicle communications and massive multiple-input multiple-output (MIMO) systems. Nevertheless, this basic OTFS system has serious problems: high out-of-band (OOB) power emission and high peak-to-average power ratio (PAPR). This high OOB power spectrum requires a very wide guard band that can produce a great loss of frequency utilization efficiency, and the power efficiency becomes very poor due to this high PAPR problem. Therefore, in this paper, in order to mitigate these drawbacks, an advanced OTFS communication system is proposed to show the compact OOB power spectrum and power efficiency improvement.This system can be designed by discrete Fourier transform (DFT)-spread windowing and restructuring-OTFS (DFT-Spread WR-OTFS) scheme that can reduce PAPR by 2.1 dB, 0.5 dB, 1.7 dB, and 1.8 dB compared to the conventional OFDM, DFT-Spread OFDM, basic OTFS and WR-OTFS schemes, respectively. Consequently, the efficiency of the high power amplifier (HPA) is improved due to the low PAPR of the proposed system. In addition, we comprehensively evaluate the impact of PAPR reduction performance on the OOB power spectrums and bit error rate (BER) performance of each system in HPA linear and nonlinear environments. Simulation results verify that the power spectrums and the BER performance of the proposed system are better than the conventional schemes in HPA nonlinear environments.

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Low-complexity iterative detection for orthogonal time frequency space modulation

Cited by 123 publications

References 9 publications

Embedded Pilot-Aided Channel Estimation for OTFS in Delay–Doppler Channels

Embedded Pilot-Aided Channel Estimation for OTFS in Delay–Doppler Channels

Interference Cancellation and Iterative Detection for Orthogonal Time Frequency Space Modulation

Advanced OTFS communication system with compact spectrum and power efficiency improvement

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