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Open AccessArticle

Hybrid NOMA Protocol with Relay Adaptive AF/DF Collaboration and Its Modeling Analysis in NB-IoT

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Electronics 2023, 12(15), 3217; https://doi.org/10.3390/electronics12153217 - 25 Jul 2023

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Abstract

In order to meet the demand for large-scale device access in Narrowband Internet of Things (NB-IoT) and to overcome the problem that some resources are wasted due to the use of single decode-and-forward (DF) or amplify-and-forward (AF) collaboration in traditional collaborative communication, this [...] Read more.

In order to meet the demand for large-scale device access in Narrowband Internet of Things (NB-IoT) and to overcome the problem that some resources are wasted due to the use of single decode-and-forward (DF) or amplify-and-forward (AF) collaboration in traditional collaborative communication, this paper introduces a non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) hybrid access method into the NB-IoT and proposes a new Hybrid NOMA transmission protocol with relay adaptively selectable collaboration, which is represented as an algorithm. Based on this protocol, we classify the whole transmission process into five states after deriving the outage probability of each link. We then consider the system as a discrete-time Markov model, the closed expressions of the system outage probability and throughput are derived based on the system steady-state probability. In order to improve the system’s reliability, we further optimize the above protocol by allowing the source node to retransmit the unsuccessful received superimposed signals a limited number of times. Numerical results and simulations show that the outage probability is lower when multiple retransmissions are possible. The proposed relay adaptive collaborative hybrid NOMA transmission protocol has advantages over the pure OMA transmission mode. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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Open AccessArticle

A Novel Fully Digital Feedforward Background Calibration Technique for Timing Mismatch in M-Channel Time-Interleaved ADCs

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Electronics 2023, 12(9), 1965; https://doi.org/10.3390/electronics12091965 - 23 Apr 2023

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Abstract

This paper presents a novel digital background calibration technique for timing mismatches in time-interleaved analog-to-digital converters (TIADCs). We reconstruct and eliminate the timing mismatch based on the theory of timing-mismatch-induced spurious signals in the frequency domain. The proposed compensation algorithm utilizes the conjugate [...] Read more.

This paper presents a novel digital background calibration technique for timing mismatches in time-interleaved analog-to-digital converters (TIADCs). We reconstruct and eliminate the timing mismatch based on the theory of timing-mismatch-induced spurious signals in the frequency domain. The proposed compensation algorithm utilizes the conjugate property between spurious signals to achieve low complexity. A coarse-fine correction architecture is adopted to eliminate higher-order time-skew errors. A novel feedforward estimation algorithm based on the correlation of adjacent channels is proposed to extract the time-skew errors. Our proposed calibration technique is suitable for an arbitrary number of channels. The simulation results demonstrate that the utilization of the proposed calibration technique yields significant improvements in both the signal-to-noise-and-distortion ratio (SNDR) and spurious-free dynamic range (SFDR). The SNDR and SFDR are improved from 55.82 dB and 56.64 dB to 79.92 dB and 105.98 dB, respectively. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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Open AccessArticle

A Digital Timing-Mismatch Calibration Technique for Time-Interleaved ADCs Based on a Coordinate Rotational Digital Computer Algorithm

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Electronics 2023, 12(6), 1319; https://doi.org/10.3390/electronics12061319 - 09 Mar 2023

Cited by 1 | Viewed by 883

Abstract

Timing-mismatch errors among channels in time-interleaved analog-to-digital converters (TIADCs) greatly degrade the whole performance of the system. Therefore, techniques for calibrating timing mismatch are indispensable, and a new fully-digital calibration technique is presented in this article. Based on a Hilbert filter, modified moving [...] Read more.

Timing-mismatch errors among channels in time-interleaved analog-to-digital converters (TIADCs) greatly degrade the whole performance of the system. Therefore, techniques for calibrating timing mismatch are indispensable, and a new fully-digital calibration technique is presented in this article. Based on a Hilbert filter, modified moving averagers (MMAs) and inverse cosine functions, the proposed estimation algorithm is fast (within 1200 sample points) and accurate. Meanwhile, the coordinate rotational digital computer (CORDIC) algorithm, which is used to implement inverse cosine functions, is also improved, giving it higher precision. In addition, a compensation method based on second-order Taylor series approximation with less hardware resource consumption is provided. Through analyses and simulations, this calibration technique proved to be suitable for TIADCs with an arbitrary number of channels, in which the signal-to-noise and distortion ratio (SNDR) and the spurious-free dynamic range (SFDR) were, respectively, improved from 24.06 dB and 24.57 dB to 67.96 dB and 85.69 dB. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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Open AccessArticle

Cooperative Localization of Firefighters Based on Relative Ranging Constraints of UWB and Autonomous Navigation

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Electronics 2023, 12(5), 1181; https://doi.org/10.3390/electronics12051181 - 28 Feb 2023

Viewed by 806

Abstract

There are many demands for the cooperative localization (CL) of multiple people, such as firefighter rescue. The classical foot-mounted inertial navigation based on zero velocity update (ZUPT) suffers from accumulating error due to the low-cost inertial sensor, and the pre-placed anchors in the [...] Read more.

There are many demands for the cooperative localization (CL) of multiple people, such as firefighter rescue. The classical foot-mounted inertial navigation based on zero velocity update (ZUPT) suffers from accumulating error due to the low-cost inertial sensor, and the pre-placed anchors in the ultra-wideband (UWB) system limit the application in an unknown environment. In this study, a group of sensors including the inertial measurement unit (IMU), magnetometer, barometer, and UWB sensor is used. Through the different characteristics of sensors and the position relationship between people, a cooperative localization system using an extended Kalman filter for three-dimensional firefighter tracking is proposed. Ranging information between firefighters from UWB is utilized, and couplings introduced by relative measurement are estimated. Two experiments are designed to verify the proposed algorithm in building and forest environments. Compared with the results of single-person inertial navigation, the average positioning precision of the algorithm in the building and forest is, respectively, improved by 38.93% and 79.01%. This approach successfully suppresses the divergence of positioning errors, and fixed UWB anchors are not needed. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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Open AccessArticle

Design of a Low-Cost Measurement Module for the Acquisition of Analogue Voltage Signals

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Electronics 2023, 12(3), 610; https://doi.org/10.3390/electronics12030610 - 26 Jan 2023

Viewed by 898

Abstract

The aim of this work was to design and program a low-cost universal multichannel measurement card from scratch. The constructed device has analog inputs with the possibility of using them as differential inputs. This makes it possible to measure the analog signals for [...] Read more.

The aim of this work was to design and program a low-cost universal multichannel measurement card from scratch. The constructed device has analog inputs with the possibility of using them as differential inputs. This makes it possible to measure the analog signals for most of the available sensors. Thus, universality of the device is achieved. Simultaneously, the main assumption of the project and its novelty was to develop a measurement module. It is characterized by high measurement parameters, comparable to commercial products available on the market, with a very low production cost. The usability and assumed features of the measurement module were verified and tested using a functional generator and constructed test stand. During the tests, a sampling rate of at least 250 kS/s and a resolution of at least 14 bit were used. The module enables the acquisition of analog signals with voltages in the range of ±10 V and digital signals in the transistor–transistor logic (TTL) 5 V standard with a frequency of at least 250 kS/s. In addition, our device can be controlled via a computer, and data can be downloaded via the USB interface. It has 16 input channels with the possibility of differential measurements. The proposed solution is several times cheaper than commercial solutions while maintaining comparable parameters, as shown in the conclusion of the work. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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Open AccessArticle

Aperture-Level Simultaneous Transmit and Receive Simplified Structure Based on Hybrid Beamforming of Switching Network

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Electronics 2023, 12(3), 602; https://doi.org/10.3390/electronics12030602 - 25 Jan 2023

Viewed by 604

Abstract

With the increasing competition for spectrum resources, the technology of simultaneous transmit and receive (STAR) is attracting more and more attention. However, full digital aperture-level simultaneous transmit and receive (FD-ALSTAR) is difficult to implement in a large-scale array with high frequency and bandwidth [...] Read more.

With the increasing competition for spectrum resources, the technology of simultaneous transmit and receive (STAR) is attracting more and more attention. However, full digital aperture-level simultaneous transmit and receive (FD-ALSTAR) is difficult to implement in a large-scale array with high frequency and bandwidth due to its high hardware cost and high power consumption. Therefore, this paper combines FD-ALSTAR with hybrid beamforming technology and proposes two categories and four types of aperture-level simultaneous transmit and receive simplified structures based on hybrid beamforming to reduce the number of RF links (NRF), hardware cost, and operation power consumption. In view of the complexity of the hardware of the fully connected hybrid beamforming structure and the low amplitude and phase control accuracy of the partially connected hybrid beamforming structure, an aperture-level simultaneous transmit and receive simplified structure based on hybrid beamforming of switching network (HBF-SN-ALSTAR) is proposed, and the mathematical model is established. The simulation results show that the simplified structure proposed in this paper can effectively reduce the NRF and power consumption, increase system redundancy, and improve system reliability. In a 144 × 144 antenna array, under the condition that NRF = 16 of HBF-SN-ALSTAR, that is, 1/9 of the number of FD-ALSTAR RF links, the effective isotropic isolation (EII) of the system is only 17 dB less than that of the FD-ALSTAR. The experimental results fully prove the effectiveness of the simplified structure. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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Open AccessArticle

A Sparse Recovery Algorithm Based on Arithmetic Optimization

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Electronics 2023, 12(1), 162; https://doi.org/10.3390/electronics12010162 - 29 Dec 2022

Viewed by 667

Abstract

At present, the sparse recovery problem is mainly solved by convx optimization algorithm and greedy tracking method. However, the former has defects in recovery efficiency and the latter in recovery ability, and neither of them can obtain effective recovery under large sparsity or [...] Read more.

At present, the sparse recovery problem is mainly solved by convx optimization algorithm and greedy tracking method. However, the former has defects in recovery efficiency and the latter in recovery ability, and neither of them can obtain effective recovery under large sparsity or small observation degree. In this paper, we propose a new sparse recovery algorithm based on arithmetic optimization algorithm and combine the ideas of greedy tracking method. The proposed algorithm uses arithmetic optimization algorithm to solve the sparse coefficient of the signal in the transform domain, so as to reconstruct the original signal. At the same time, the greedy tracking technique is combined to design the initial position of the operator before solving, so that it can be searched better. Experiments show that compared with other methods, the proposed algorithm can not only obtain more effective recovery, but also run faster under general conditions of observation number. At the same time, It can also recover the signal better in the presence of noise. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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Open AccessArticle

Periodic Signal Suppression in Position Domain Based on Repetitive Control

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Electronics 2022, 11(24), 4069; https://doi.org/10.3390/electronics11244069 - 07 Dec 2022

Cited by 2 | Viewed by 808

Abstract

In this paper, a periodic signal suppression method in position domain based on repetitive control (RC) is proposed to realize high-precision speed control for the gimbal servo system of the single gimbal control moment gyro (SGCMG). To reduce the volume and weight while [...] Read more.

In this paper, a periodic signal suppression method in position domain based on repetitive control (RC) is proposed to realize high-precision speed control for the gimbal servo system of the single gimbal control moment gyro (SGCMG). To reduce the volume and weight while outputting large torque, the gimbal servo system usually needs to install the harmonic drive. However, the nonlinear transmission characteristics of the harmonic drive are also introduced into the gimbal servo system and make the speed fluctuate. Considering the speed fluctuation signal shown as a fixed frequency in the position domain, a position domain RC method combined with acceleration feedback is designed to realize the speed fluctuation minimization. The position domain RC improves the dynamic characteristics, while the acceleration feedback increases the damping of the system. To analyze the stability, the position domain RC is converted into the time domain through the domain transformation method, and a phase compensator is designed to improve the stability and increase the bandwidth of the position domain RC by compensating for the phase lag of the middle and low frequency, respectively. The feasibility and effectiveness of the proposed method are verified by the simulation and experimental results. These results illustrate that after applying the proposed approach, the output speed fluctuation and harmonic components decrease more than 20% and 24.1%, respectively. Full article

(This article belongs to the Special Issue Advanced Technologies in Digital Signal Processing)

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