33 research outputs found
The BER Analysis of MRC-aided Greedy Detection for OFDM-IM in Presence of Uncertain CSI
This letter investigates the bit error rate (BER) performance of orthogonal frequency division multiplexing index modulation, employing the maximal ratio combining-based low-complexity greedy detector (MRC-GD) and the PSK modulation. For performance analysis, we derive tight expressions for both index error probability (IEP) and BER, taking into account channel state information (CSI) uncertainty. This provides insight into various impacts of CSI uncertainty on the diversity gain and error floor of the IEP and the BER, respectively. We clearly show that under imperfect CSI, the MRC-aided GD can perform like the MRC-maximum likelihood detector, at lower complexity. Finally, simulation results are presented to verify the accuracy of derived expressions and the theoretical analysis
Spread OFDM-IM with precoding matrix and low-complexity detection designs
We propose a new spread orthogonal frequency division multiplexing with index modulation (S-OFDM-IM), which employs precoding matrices such as Walsh-Hadamard (WH) and Zadoff-Chu (ZC) to spread both non-zero data symbols of active sub-carriers and their indices, and then compress them into all available sub-carriers. This aims to increase the transmit diversity, exploiting both multipath and index diversities. As for the performance analysis, we derive the bit error probability (BEP) to provide an insight into the diversity and coding gains, and especially impacts of selecting various spreading matrices on these gains. This interestingly reveals an opportunity of using rotated versions of original WH and ZC matrices to further improve the BEP performance. More specifically, rotated matrices can enable S-OFDM-IM to harvest the maximum diversity gain, which is the number of sub-carriers, while benchmark schemes have diversity gains limited by two. Moreover, we propose three low-complexity detectors, namely minimum mean square error log-likelihood ratio, index pattern MMSE (IP-MMSE), and enhanced IP-MMSE, which achieve different levels of complexity and reliability. Simulation results are presented to prove the superiority of S-OFDM-IM over the benchmarks
Impact of CSI Uncertainty on the MCIK-OFDM Performance: Tight, Closed-Form Symbol Error Probability Analysis
This paper proposes a novel framework to analyze the symbol error probability (SEP) for multicarrier index keying orthogonal frequency-division multiplexing (MCIK-OFDM) systems. Considering two different types of detections such as the maximum likelihood (ML) and low-complexity greedy detectors (GD), we derive tight closed-form expressions for the average SEPs of MCIK-OFDM in the presence of channel state information (CSI) uncertainty. We undertake an asymptotic performance analysis with respect to three CSI conditions, which ensures to provide a comprehensive insight into the achievable diversity and coding gains as well as the impact of various CSI uncertainties on the SEP performance. The SEP performance comparison between the ML and GD is obtained under different CSI uncertainties. This interestingly reveals that the GD can achieve nearly optimal error performance as the M-ary modulation size is large or even outperforms the ML under certain CSI conditions. Finally, the theoretical and asymptotic analysis are verified via simulation results, obtaining the high accuracy of the derived SEP
After-Fatigue Condition: A Novel Analysis Based on Surface EMG Signals
This study introduces a novel muscle activation analysis based on surface
electromyography (sEMG) signals to assess the muscle's after-fatigue condition.
Previous studies have mainly focused on the before-fatigue and fatigue
conditions. However, a comprehensive analysis of the after-fatigue condition
has been overlooked. The proposed method analyzes muscle fatigue indicators at
various maximal voluntary contraction (MVC) levels to compare the
before-fatigue, fatigue, and after-fatigue conditions using amplitude-based,
spectral-based, and muscle fiber conduction velocity (CV) parameters. In
addition, the contraction time of each MVC level is also analyzed with the same
indicators. The results show that in the after-fatigue condition, the muscle
activation changes significantly in the ways such as higher CV, power spectral
density shifting to the right, and longer contraction time until exhaustion
compared to the before-fatigue and fatigue conditions. The results can provide
a comprehensive and objective evaluation of muscle fatigue and recovery, which
can be helpful in clinical diagnosis, rehabilitation, and sports performance
Repeated MCIK-OFDM with Enhanced Transmit Diversity under CSI Uncertainty
This paper investigates the opportunity for a repetition coded multi-carrier index keying-orthogonal frequency division multiplexing (MCIK-OFDM), termed repeated MCIK-OFDM (ReMO), which can provide superior performance over existing schemes at the same spectral efficiency. Unlike the classical scheme, the proposed scheme activates a subset of subcarriers and modulates them with the same M-ary data symbol, while additional information is conveyed by the active sub-carrier indices. This approach not only provides the frequency diversity gains in the M-ary symbol detection but also improves the index detection, leading to considerable improvement in the transmit diversity. For performance analysis, we derive tight closed-form expressions for the symbol error probability and the bit error rate, under both perfect and imperfect channel state information (CSI). These expressions provide insight into the achievable performance gains, system designs, and impacts of various CSI conditions. Finally, simulation results are given to illustrate the superior performance achieved by our scheme over existing schemes under different CSI uncertainties
Transformer-Based Deep Learning Detector for Dual-Mode Index Modulation 3D-OFDM
In this paper, we propose a deep learning-based signal detector called
TransD3D-IM, which employs the Transformer framework for signal detection in
the Dual-mode index modulation-aided three-dimensional (3D) orthogonal
frequency division multiplexing (DM-IM-3D-OFDM) system. In this system, the
data bits are conveyed using dual-mode 3D constellation symbols and active
subcarrier indices. As a result, this method exhibits significantly higher
transmission reliability than current IM-based models with traditional maximum
likelihood (ML) detection. Nevertheless, the ML detector suffers from high
computational complexity, particularly when the parameters of the system are
large. Even the complexity of the Log-Likelihood Ratio algorithm, known as a
low-complexity detector for signal detection in the DM-IM-3D-OFDM system, is
also not impressive enough. To overcome this limitation, our proposal applies a
deep neural network at the receiver, utilizing the Transformer framework for
signal detection of DM-IM-3D-OFDM system in Rayleigh fading channel. Simulation
results demonstrate that our detector attains to approach performance compared
to the model-based receiver. Furthermore, TransD3D-IM exhibits more robustness
than the existing deep learning-based detector while considerably reducing
runtime complexity in comparison with the benchmarks
Deep Learning-Based Signal Detection for Dual-Mode Index Modulation 3D-OFDM
In this paper, we propose a deep learning-based signal detector called
DuaIM-3DNet for dual-mode index modulation-based three-dimensional (3D)
orthogonal frequency division multiplexing (DM-IM-3D-OFDM). Herein, DM-IM-3D-
OFDM is a subcarrier index modulation scheme which conveys data bits via both
dual-mode 3D constellation symbols and indices of active subcarriers. Thus,
this scheme obtains better error performance than the existing IM schemes when
using the conventional maximum likelihood (ML) detector, which, however,
suffers from high computational complexity, especially when the system
parameters increase. In order to address this fundamental issue, we propose the
usage of a deep neural network (DNN) at the receiver to jointly and reliably
detect both symbols and index bits of DM-IM-3D-OFDM under Rayleigh fading
channels in a data-driven manner. Simulation results demonstrate that our
proposed DNN detector achieves near-optimal performance at significantly lower
runtime complexity compared to the ML detector
Deep Energy Autoencoder for Noncoherent Multicarrier MU-SIMO Systems
We propose a novel deep energy autoencoder (EA) for noncoherent multicarrier
multiuser single-input multipleoutput (MU-SIMO) systems under fading channels.
In particular, a single-user noncoherent EA-based (NC-EA) system, based on the
multicarrier SIMO framework, is first proposed, where both the transmitter and
receiver are represented by deep neural networks (DNNs), known as the encoder
and decoder of an EA. Unlike existing systems, the decoder of the NC-EA is fed
only with the energy combined from all receive antennas, while its encoder
outputs a real-valued vector whose elements stand for the subcarrier power
levels. Using the NC-EA, we then develop two novel DNN structures for both
uplink and downlink NC-EA multiple access (NC-EAMA) schemes, based on the
multicarrier MUSIMO framework. Note that NC-EAMA allows multiple users to share
the same sub-carriers, thus enables to achieve higher performance gains than
noncoherent orthogonal counterparts. By properly training, the proposed NC-EA
and NC-EAMA can efficiently recover the transmitted data without any channel
state information estimation. Simulation results clearly show the superiority
of our schemes in terms of reliability, flexibility and complexity over
baseline schemes.Comment: Accepted, IEEE TW
Deep Neural Network-Based Detector for Single-Carrier Index Modulation NOMA
In this paper, a deep neural network (DNN)-based detector for an uplink
single-carrier index modulation nonorthogonal multiple access (SC-IM-NOMA)
system is proposed, where SC-IM-NOMA allows users to use the same set of
subcarriers for transmitting their data modulated by the sub-carrier index
modulation technique. More particularly, users of SC-IMNOMA simultaneously
transmit their SC-IM data at different power levels which are then exploited by
their receivers to perform successive interference cancellation (SIC)
multi-user detection. The existing detectors designed for SC-IM-NOMA, such as
the joint maximum-likelihood (JML) detector and the maximum likelihood
SIC-based (ML-SIC) detector, suffer from high computational complexity. To
address this issue, we propose a DNN-based detector whose structure relies on
the model-based SIC for jointly detecting both M-ary symbols and index bits of
all users after trained with sufficient simulated data. The simulation results
demonstrate that the proposed DNN-based detector attains near-optimal error
performance and significantly reduced runtime complexity in comparison with the
existing hand-crafted detectors