5 research outputs found
A Very Low Complexity Successive Symbol-by-Symbol Sequence Estimator for Faster-Than-Nyquist Signaling
In this paper, we investigate the sequence estimation problem of binary and
quadrature phase shift keying faster-than-Nyquist (FTN) signaling and propose
two novel low-complexity sequence estimation techniques based on concepts of
successive interference cancellation. To the best of our knowledge, this is the
first approach in the literature to detect FTN signaling on a symbol-by-symbol
basis. In particular, based on the structure of the self-interference inherited
in FTN signaling, we first find the operating region boundary---defined by the
root-raised cosine (rRC) pulse shape, its roll-off factor, and the time
acceleration parameter of the FTN signaling---where perfect estimation of the
transmit data symbols on a symbol-by-symbol basis is guaranteed, assuming
noise-free transmission. For noisy transmission, we then propose a novel
low-complexity technique that works within the operating region and is capable
of estimating the transmit data symbols on a symbol-by-symbol basis. To reduce
the error propagation of the proposed successive symbol-by-symbol sequence
estimator (SSSSE), we propose a successive symbol-by-symbol with go-back-
sequence estimator (SSSgbSE) that goes back to re-estimate up to
symbols, and subsequently improves the estimation accuracy of the current data
symbol. Simulation results show that the proposed sequence estimation
techniques perform well for low intersymbol interference (ISI) scenarios and
can significantly increase the data rate and spectral efficiency. Additionally,
results reveal that choosing the value of as low as or data symbols
is sufficient to significantly improve the bit-error-rate performance. Results
also show that the performance of the proposed SSSgbSE, with or ,
surpasses the performance of the lowest complexity equalizers reported in the
literature, with reduced computational complexity.Comment: IEEE Access, accepte
Polar Coded Faster-than-Nyquist (FTN) Signaling with Symbol-by-Symbol Detection
Reduced complexity faster-than-Nyquist (FTN) signaling systems are gaining
increased attention as they provide improved bandwidth utilization for an
acceptable level of detection complexity. In order to have a better
understanding of the tradeoff between performance and complexity of the reduced
complexity FTN detection techniques, it is necessary to study these techniques
in the presence of channel coding. In this paper, we investigate the
performance a polar coded FTN system which uses a reduced complexity FTN
detection, namely, the recently proposed successive symbol-by-symbol with
go-backK sequence estimation (SSSgbKSE) technique. Simulations are performed
for various intersymbol-interference (ISI) levels and for various go-back-K
values. Bit error rate (BER) performance of Bahl-Cocke-Jelinek-Raviv (BCJR)
detection and SSSgbKSE detection techniques are studied for both uncoded and
polar coded systems. Simulation results reveal that polar codes can compensate
some of the performance loss incurred in the reduced complexity SSSgbKSE
technique and assist in closing the performance gap between BCJR and SSSgbKSE
detection algorithms
Low-Complexity Detection of High-Order QAM Faster-than-Nyquist Signaling
Faster-than-Nyquist (FTN) signaling is a promising non-orthogonal transmission technique to considerably improve the spectral efficiency. This paper presents the first attempt in the literature to estimate the transmit data symbols of any high-order quadrature amplitude modulation (QAM) FTN signaling in polynomial time complexity. In particular, we propose a generalized approach to model the finite alphabet of any high-order QAM constellation as a high degree polynomial constraint. Then, we formulate the high-order QAM FTN signaling sequence estimation problem as a non-convex optimization problem. As an example of a high-order QAM, we consider 16-QAM FTN signaling and then transform the high degree polynomial constraint, with the help of auxiliary variables, to multiple quadratic constraints. Such transformation allows us to propose a generalized approach semidefinite relaxation (SDR)- based sequence estimation (GASDRSE) technique to efficiently provide a sub-optimal solution to the NP-hard non-convex FTN detection problem, with polynomial time complexity. For the particular case of 16-QAM FTN signaling,
A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future
A High Altitude Platform Station (HAPS) is a network node that operates in
the stratosphere at an of altitude around 20 km and is instrumental for
providing communication services. Precipitated by technological innovations in
the areas of autonomous avionics, array antennas, solar panel efficiency
levels, and battery energy densities, and fueled by flourishing industry
ecosystems, the HAPS has emerged as an indispensable component of
next-generations of wireless networks. In this article, we provide a vision and
framework for the HAPS networks of the future supported by a comprehensive and
state-of-the-art literature review. We highlight the unrealized potential of
HAPS systems and elaborate on their unique ability to serve metropolitan areas.
The latest advancements and promising technologies in the HAPS energy and
payload systems are discussed. The integration of the emerging Reconfigurable
Smart Surface (RSS) technology in the communications payload of HAPS systems
for providing a cost-effective deployment is proposed. A detailed overview of
the radio resource management in HAPS systems is presented along with
synergistic physical layer techniques, including Faster-Than-Nyquist (FTN)
signaling. Numerous aspects of handoff management in HAPS systems are
described. The notable contributions of Artificial Intelligence (AI) in HAPS,
including machine learning in the design, topology management, handoff, and
resource allocation aspects are emphasized. The extensive overview of the
literature we provide is crucial for substantiating our vision that depicts the
expected deployment opportunities and challenges in the next 10 years
(next-generation networks), as well as in the subsequent 10 years
(next-next-generation networks).Comment: To appear in IEEE Communications Surveys & Tutorial