Max-log demapper architecture design for DVB-T2 rotated QAM constellations

Yang, Jibin; Li, Meng; Li, Min; Nour, Charbel Abdel; Douillard, Catherine; Geller, Benoît

doi:10.1109/sips.2015.7344998

Cited by 12 publications

(6 citation statements)

References 21 publications

(12 reference statements)

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“…The equalized symbols can then be demapped as conventional M -QAM symbols with an O( √ M ) complexity, but the noise level is increased and performance becomes poor when the 2×2 channel response matrix is singular. Instead, two-dimensional (I and Q) demappers (2D-DEM) [13]- [16] approach much closely the optimum performance. In [13], a QAM constellation space is decomposed into four squared sub-regions and the demapping is performed within one of the four sub-regions according to the signs of the real and imaginary parts of the equalized symbol.…”

Section: Introductionmentioning

confidence: 99%

Uniformly Projected RCQD QAM: A Low-Complexity Signal Space Diversity Solution Over Fading Channels With or Without Erasures

Arbi

Geller

Yang

et al. 2018

IEEE Trans. on Broadcast.

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Abstract-Rotated and cyclic Q-delayed (RCQD) M -QAM (Quadrature Amplitude Modulation) provides signal space diversity and thus improves system performance over fading channels. However, previously published RCQD solutions were designed without fully considering the high demodulation complexity which prohibits wider applications. In this paper, a complete solution is proposed to reduce complexity for both the modulator and the demodulator. This solution uses a series of rotation angles α =arctan(1/ √ M ) which bring many interesting properties to the RCQD signals. A simplified sphere demapping algorithm is derived for fading channels with and without erasure events. In contrast to the sphere-decoder used for MIMO detection, the radius of the proposed sphere-demapper involves an exact amount of constellation points, thereby ensuring to perform the soft demapping operation successfully. Moreover, when either the in-phase (I) or the quadrature component (Q) is erased, the proposed demapping algorithm performs as well as the fullcomplexity Max-Log algorithm, with a reduced complexity. Compared to the solution currently used in DVB-T2, the proposed method reduces tremendously the computational complexity while still achieving similar performance over fading channels and even better performance over fading erasure channels.

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Section: Introductionmentioning

confidence: 99%

Uniformly Projected RCQD QAM: A Low-Complexity Signal Space Diversity Solution Over Fading Channels With or Without Erasures

Arbi

Geller

Yang

et al. 2018

IEEE Trans. on Broadcast.

Self Cite

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“…Simulation results of our proposal shows a significant BER improvement compared to the conventional solutions, in particular for time-varying channel with high Doppler shifts. Finally, in the future it seems very interesting to design fully adaptive algorithms for equalization and phase synchronisation for rotated constellations [29]- [34] so as to take advantage of the inherent diversity of rotated constellations without any bandwidth loss.…”

Section: Discussionmentioning

confidence: 99%

Adaptive Step-size Iterative Equalization for Underwater Communication

Arbi

Geller

2021

OCEANS 2021: San Diego – Porto

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This paper presents a fully adaptive Minimum Mean Square Error (MMSE) iterative equalization with a joint phase estimation, using various adaptive step-sizes scheme. To meet the requirement of fast convergence and low MSE over time-varying channels, we propose an original self-optimized algorithm whose step-sizes are updated adaptively and assisted by soft-information provided by the channel decoder in an iterative manner. Simulation results show that our proposal achieves better performance over various multipath time-varying channels, compared to the conventional equalizer using a fixed step-size.

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“…Regions 1 (Europe and Africa) and 3 (Asia) allocated the 800 MHz band (790-862 MHz, channels [61][62][63][64][65][66][67][68][69] for fourth generation (4G) LTE services, and Region 2 (America) allocated the 700 MHz band (698-806 MHz, channels [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69]. In the WRC-12, the ITU concluded with a decision to allocate additional UHF spectrum to mobile services.…”

Section: First and Second Digital Dividendsmentioning

confidence: 99%

“…For most countries, releasing the 700 MHz band will require a new re-tune of existing DTT networks. Implementing the DD2 within ITU Region 1 affects up to eleven more DTT channels (49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60), creating a number of challenges. Since cellular terminals are closer to the DTT receivers than base stations, interference issues may be relevant in the 700 MHz band [4].…”

Section: First and Second Digital Dividendsmentioning

confidence: 99%

“…The concept is similar to a sphere demapper [56], which also selects a cluster of symbols to compute the LLRs. An additional complexity-reduced max-log demapper for RCs was proposed in [57]. The proposed demapper allows to find the ML symbols with a search spanning, calculating only √ M signal constellation symbols and guaranteeing the same LLR metrics as the original max-log demapper.…”

Section: Combination With Advanced Signal Processing Techniquesmentioning

confidence: 99%

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Non-Uniform Constellations for Next-Generation Digital Terrestrial Broadcast Systems

Muela¹

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Nowadays, the digital terrestrial television (DTT) market is characterized by the high capacity needed for high definition TV services, and the limited spectrum available. There is a need for an efficient use of the broadcast spectrum, which requires new technologies to guarantee increased capacities. NonUniform Constellations (NUC) arise as one of the most innovative techniques to approach those requirements. These constellations have been implemented in next-generation broadcast systems such as DVB-NGH (Digital Video Broadcasting -Next Generation Handheld) or ATSC 3.0 (Advanced Television Systems Committee -Third Generation). NUCs reduce the gap between uniform Gray-labelled Quadrature Amplitude Modulation (QAM) constellations and the theoretical unconstrained Shannon limit. With these constellations, symbols are optimized in both in-phase (I) and quadrature (Q) components by means of signal geometrical shaping, considering a certain signal-to-noise ratio (SNR) and channel model.There are two types of NUC, depending on the number of real-valued dimensions considered in the optimization process, i.e. one-dimensional and two dimensional NUCs (1D-NUC and 2D-NUC, respectively). 1D-NUCs maintain the squared shape from QAM, but relaxing the distribution between constellation symbols in a single component, with non-uniform distance between them. These constellations provide better SNR performance than QAM, without any demapping complexity increase. 2D-NUCs also relax the square shape constraint, allowing to optimize the symbol positions in both dimensions, thus achieving higher capacity gains and lower SNR requirements. However, the use of 2D-NUCs implies a higher demapping complexity, since a 2D-demapper is needed, i.e. I and Q components cannot be separated.In this dissertation, NUCs are analyzed from both transmit and receive point of views, using either single-input single-output (SISO) or multiple-input multiple-output (MIMO) antenna configurations. In SISO transmissions, 1D-NUCs and 2D-NUCs are optimized for a wide range of SNRs, several channel models and different constellation orders, using the Nelder-Mead optimization 3 ABSTRACT algorithm. The optimization of rotated 2D-NUCs is also investigated, including the rotation angle as an additional variable in the optimization. Even though the demapping complexity is not increased, the SNR gain of these constellations is not significant. The highest rotation gain is obtained for low-order constellations and high SNRs. However, with multi-RF techniques such as Channel Bonding (CB) or Time-Frequency Slicing (TFS), the SNR gain is drastically increased, since I and Q components are transmitted in different RF channels. In this thesis, multi-RF gains of NUCs with and without rotation are provided for some representative scenarios.At the receiver, two different implementation bottlenecks are explored. First, the demapping complexity of all considered constellations is analyzed. Afterwards, two complexity reduction algorithms for 2D-NUCs are proposed. Both algor...

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Max-log demapper architecture design for DVB-T2 rotated QAM constellations

Cited by 12 publications

References 21 publications

Uniformly Projected RCQD QAM: A Low-Complexity Signal Space Diversity Solution Over Fading Channels With or Without Erasures

Uniformly Projected RCQD QAM: A Low-Complexity Signal Space Diversity Solution Over Fading Channels With or Without Erasures

Adaptive Step-size Iterative Equalization for Underwater Communication

Non-Uniform Constellations for Next-Generation Digital Terrestrial Broadcast Systems

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