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22 pages, 2401 KiB

Open AccessArticle

Multi-Parameter Estimation Method and Closed-Form Solution Study for k-µ Channel Model

by Jie Tian, Zhongqing Fan, Zhengyu Ji, Xianglu Li, Peng Fei and Dong Hou

Sensors 2023, 23(10), 4760; https://doi.org/10.3390/s23104760 - 15 May 2023

Viewed by 982

Abstract

This paper proposes a novel multi-parameter estimation algorithm for the k-µ fading channel model to analyze wireless transmission performance in complex time-varying and non-line-of-sight communication scenarios involving moving targets. The proposed estimator offers a mathematically tractable theoretical framework for the application of the [...] Read more.

This paper proposes a novel multi-parameter estimation algorithm for the k-µ fading channel model to analyze wireless transmission performance in complex time-varying and non-line-of-sight communication scenarios involving moving targets. The proposed estimator offers a mathematically tractable theoretical framework for the application of the k-µ fading channel model in realistic scenarios. Specifically, the algorithm obtains expressions for the moment-generating function of the k-µ fading distribution and eliminates the gamma function using the even-order moment value comparison method. It then obtains two sets of solution models for the moment-generating function at different orders, which enable the estimation of the k and µ parameters using three sets of closed-form solutions. The k and µ parameters are estimated based on received channel data samples generated using the Monte Carlo method to restore the distribution envelope of the received signal. Simulation results show strong agreement between theoretical and estimated values for the closed-form estimated solutions. Additionally, the differences in complexity, accuracy exhibited under different parameter settings, and robustness under decreasing SNR may make the estimators suitable for different practical application scenarios. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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12 pages, 624 KiB

Open AccessArticle

UAV-Aided Dual-User Wireless Power Transfer: 3D Trajectory Design and Energy Optimization

by Xiaogang Gou, Zhaojie Sun and Kaiyuan Huang

Sensors 2023, 23(6), 2994; https://doi.org/10.3390/s23062994 - 10 Mar 2023

Cited by 2 | Viewed by 1426

Abstract

Unmanned aerial vehicles (UAVs) have been widely considered to enhance the communication coverage, as well as the wireless power transfer (WPT) of energy-constrained communication networks to prolong their lifetime. However, the trajectory design of a UAV in such a system remains a key [...] Read more.

Unmanned aerial vehicles (UAVs) have been widely considered to enhance the communication coverage, as well as the wireless power transfer (WPT) of energy-constrained communication networks to prolong their lifetime. However, the trajectory design of a UAV in such a system remains a key problem, especially considering the three-dimensional (3D) feature of the UAV. To address this issue, a UAV-assisted dual-user WPT system was investigated in this paper, where a UAV-mounted energy transmitter (ET) flies in the air to broadcast wireless energy to charge the energy receivers (ERs) on the ground. By optimizing the UAV’s 3D trajectory toward a balanced tradeoff between energy consumption and WPT performance, the energy harvested by all ERs during a given mission period was maximized. The above goal was achieved through the following detailed designs. On the one hand, on the basis of previous research results, there is a one-to-one correspondence between the UAV’s abscissa and height, so only the relationship between the height and time was focused on in this work to obtain the UAV’s optimal 3D trajectory. On the other hand, the idea of calculus was employed to calculate the total harvested energy, leading to the proposed high-efficiency trajectory design. Finally, the simulation results demonstrated that this contribution is capable of enhancing the energy supply by carefully designing the 3D trajectory of the UAV, compared to its conventional counterpart. In general, the above-mentioned contribution could be a promising way for UAV-aided WPT in the future Internet of Things (IoT) and wireless sensor networks (WSNs). Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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16 pages, 522 KiB

Open AccessArticle

Trajectory Design for Multi-UAV-Aided Wireless Power Transfer toward Future Wireless Systems

by Jun Mu and Zhaojie Sun

Sensors 2022, 22(18), 6859; https://doi.org/10.3390/s22186859 - 10 Sep 2022

Cited by 3 | Viewed by 1215

Abstract

In this paper, we investigate an unmanned aerial vehicle (UAV)-assisted wireless power transfer (WPT) system, in which a set of UAV-mounted mobile energy transmitters (ETs) are dispatched to broadcast wireless energy to an energy receiver (ER) on the ground. In particular, we aim [...] Read more.

In this paper, we investigate an unmanned aerial vehicle (UAV)-assisted wireless power transfer (WPT) system, in which a set of UAV-mounted mobile energy transmitters (ETs) are dispatched to broadcast wireless energy to an energy receiver (ER) on the ground. In particular, we aim to maximize the amount of energy transferred to the ER during a finite UAV’s flight period, subject to the UAV’s maximum speed and collision avoidance constraints. First, the basic one/two-UAV scenarios are researched in detail, which show that UAVs should hover at fixed locations during the whole charging period. Specifically, the Lagrange multiplier method is employed to solve the proposed optimization problem for the case of two UAV situation. Specifically, the general conclusions based on the theoretical analysis of one/two-UAV scenarios are drawn contribute to deducing the trajectory design of UAVs when the number of UAVs increases from three to seven. The obtained trajectory solution implies that UAVs should be evenly distributed on the circumference with point (0,0,H) as the center and UAVs’ safe distance as the radius. Finally, numerical results are provided to validate the trajectory design algorithm for the multiple UAVs-enabled single-user WPT system. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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13 pages, 325 KiB

Open AccessArticle

Sparse Space Shift Keying Modulation with Enhanced Constellation Mapping

by Tiebin Wang, Kaiyuan Huang, Min Liu and Ranran He

Sensors 2022, 22(15), 5895; https://doi.org/10.3390/s22155895 - 07 Aug 2022

Cited by 2 | Viewed by 1188

Abstract

For reducing the switching frequency between the radio frequency (RF) chain and transmit antennas, a class of new sparse space shift keying modulation (SSSK) schemes are presented. This new class is proposed to simplify hardware implementation, through carefully designing the spatial constellation mapping [...] Read more.

For reducing the switching frequency between the radio frequency (RF) chain and transmit antennas, a class of new sparse space shift keying modulation (SSSK) schemes are presented. This new class is proposed to simplify hardware implementation, through carefully designing the spatial constellation mapping pattern. Specifically, different from traditional space shift keying modulation (SSK), the proposed SSSK scheme utilizes more time slots to construct a joint design of time and spatial domain SSK modulation, while maintaining the special structure of single RF chain. Since part of the multi-dimension constellations of SSSK concentrate the energy in less time slots, the RF-switching frequency is effectively reduced due to the sparsity introduced in the time domain. Furthermore, through theoretical analysis, we obtain the closed-form expression of the bit error probability for the SSSK scheme, and demonstrate that slight performance gain can be achieved compared to traditional SSK with reduced implementation cost. Moreover, we integrate transmit antenna selection (TAS) to achieve considerable performance gain. Finally, simulation results confirm the effectiveness of the proposed SSSK scheme compared to its traditional counterpart. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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14 pages, 673 KiB

Open AccessArticle

Integrated Spatial Modulation and STBC-VBLAST Design toward Efficient MIMO Transmission

by Kaiyuan Huang, Yue Xiao, Lizhe Liu, Yong Li, Zhiqun Song, Bin Wang and Xingjian Li

Sensors 2022, 22(13), 4719; https://doi.org/10.3390/s22134719 - 22 Jun 2022

Cited by 4 | Viewed by 1288

Abstract

In this contribution, the concept of spatial modulation (SM) is firstly integrated into the structure of space-time block codes (STBC)-aided vertical Bell-labs layered space-time (VBLAST) systems, in order to strike a balanced tradeoff among bit error ratio (BER), spectral efficiency and computational complexity. [...] Read more.

In this contribution, the concept of spatial modulation (SM) is firstly integrated into the structure of space-time block codes (STBC)-aided vertical Bell-labs layered space-time (VBLAST) systems, in order to strike a balanced tradeoff among bit error ratio (BER), spectral efficiency and computational complexity. First of all, in order to enhance the BER performance of STBC-VBLAST, we advocate an effective transmit power allocation (TPA) scheme with negligible implementation costs, while dividing the STBC and VBLAST layers with alleviated interference, so as to facilitate combination with SM. Then, we further utilize the unique structure of SM for enhancing the spectral efficiency of original STBC-VBLAST, wherein the information is conveyed by not only the amplitude/phase modulation (APM) symbols but also the antenna indices. In addition, constellation sets of STBC symbols are specifically designed to be rotated to make full use of the degrees of freedom. Finally, the performance advantages of the above-mentioned structures over traditional STBC-VBLAST are demonstrated by the theoretical derivation of a closed-form expression for the union bound on the bit error probability for various spectral efficiencies, and they are supported by simulation results. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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17 pages, 4279 KiB

Open AccessArticle

A Random Subcarrier-Selection Method Based on Index Modulation for Secure Transmission

by Tao Zhan, Jiangong Chen, Shan Luan and Xia Lei

Sensors 2022, 22(7), 2676; https://doi.org/10.3390/s22072676 - 31 Mar 2022

Viewed by 1223

Abstract

Recently, a frequency diverse array (FDA) has been employed in an orthogonal frequency division multiplexing (OFDM) transmitter to achieve secure wireless communication without mathematical encryption. However, an insecure coupling effect arises if the frequency increments are linearly assigned to all antenna elements. To [...] Read more.

Recently, a frequency diverse array (FDA) has been employed in an orthogonal frequency division multiplexing (OFDM) transmitter to achieve secure wireless communication without mathematical encryption. However, an insecure coupling effect arises if the frequency increments are linearly assigned to all antenna elements. To solve this problem, random subcarrier-selection methods are proposed; however, the challenge lies in the random selection of subcarriers. Inspired by the randomness of index modulation (IM), this paper proposes a low complexity random subcarrier-selection method based on index modulation (RSCS-IM). Specifically, this work conducted analysis on the spectral efficiency (SE) of our system and the computational complexity of RSCS-IM, which works out a closed-form expression of the BER performance of a desired position and validates the theoretical outcomes through simulation. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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16 pages, 561 KiB

Open AccessArticle

Signal Detection for GSTFIM Systems with Carrier Frequency Offset

by Tingyong Wu, Shiwen Fan, Chengliang Di and Jinwei Ji

Sensors 2022, 22(7), 2548; https://doi.org/10.3390/s22072548 - 26 Mar 2022

Viewed by 1417

Abstract

Generalized space-time-frequency index modulation (GSTFIM) inherits the drawbacks of the conventional orthogonal frequency-division multiplex (OFDM), such as being sensitive to carrier frequency offset (CFO). For a robust design against this problem, in this contribution, a novel construction of a message passing (MP)-aided detector [...] Read more.

Generalized space-time-frequency index modulation (GSTFIM) inherits the drawbacks of the conventional orthogonal frequency-division multiplex (OFDM), such as being sensitive to carrier frequency offset (CFO). For a robust design against this problem, in this contribution, a novel construction of a message passing (MP)-aided detector is developed for GSTFIM systems to combat the influence of CFO, while offering a flexible tradeoff between transmission performance and computational complexity. Through complexity analysis and simulation results, we demonstrate that, in the context of CFO, with a careful design, the developed MP detector is capable of approaching traditional GSTFIM with maximum likelihood (ML) detection, and of offering better performance at lower complexity compared to its minimum mean-square-error (MMSE)-aided counterpart. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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15 pages, 438 KiB

Open AccessArticle

Optimal Power Allocation for Channel-Based Physical Layer Authentication in Dual-Hop Wireless Networks

by Ningbo Fan, Jiahui Sang, Yulin Heng, Xia Lei and Tao Tao

Sensors 2022, 22(5), 1759; https://doi.org/10.3390/s22051759 - 24 Feb 2022

Viewed by 1287

Abstract

Channel-based physical-layer authentication, which is capable of detecting spoofing attacks in dual-hop wireless networks with low cost and low complexity, attracted a great deal of attention from researchers. In this paper, we explore the likelihood ratio test (LRT) with cascade channel frequency response, [...] Read more.

Channel-based physical-layer authentication, which is capable of detecting spoofing attacks in dual-hop wireless networks with low cost and low complexity, attracted a great deal of attention from researchers. In this paper, we explore the likelihood ratio test (LRT) with cascade channel frequency response, which is optimal according to the Neyman–Pearson theorem. Since it is difficult to derive the theoretical threshold and the probability of detection for LRT, majority voting (MV) algorithm is employed as a trade-off between performance and practicality. We make decisions according to the temporal variations of channel frequency response in independent subcarriers separately, the results of which are used to achieve a hypothesis testing. Then, we analyze the theoretical false alarm rate (FAR) and miss detection rate (MDR) by quantifying the upper bound of their sum. Moreover, we develop the optimal power allocation strategy between the transmitter and the relay by minimizing the derived upper bound with the optimal decision threshold according to the relay-to-receiver channel gain. The proposed power allocation strategy takes advantage of the difference of noise power between the relay and the receiver to jointly adjust the transmit power, so as to improve the authentication performance on condition of fixed total power. Simulation results demonstrate that the proposed power allocation strategy outperforms the equal power allocation in terms of FAR and MDR. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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Review

Jump to: Research

29 pages, 1732 KiB

Open AccessReview

Terahertz Meets AI: The State of the Art

by Arshad Farhad and Jae-Young Pyun

Sensors 2023, 23(11), 5034; https://doi.org/10.3390/s23115034 - 24 May 2023

Cited by 9 | Viewed by 2727

Abstract

Terahertz (THz) is a promising technology for future wireless communication networks, particularly for 6G and beyond. The ultra-wide THz band, ranging from 0.1 to 10 THz, can potentially address the limited capacity and scarcity of spectrum in current wireless systems such as 4G-LTE [...] Read more.

Terahertz (THz) is a promising technology for future wireless communication networks, particularly for 6G and beyond. The ultra-wide THz band, ranging from 0.1 to 10 THz, can potentially address the limited capacity and scarcity of spectrum in current wireless systems such as 4G-LTE and 5G. Furthermore, it is expected to support advanced wireless applications requiring high data transmission and quality services, i.e., terabit-per-second backhaul systems, ultra-high-definition streaming, virtual/augmented reality, and high-bandwidth wireless communications. In recent years, artificial intelligence (AI) has been used mainly for resource management, spectrum allocation, modulation and bandwidth classification, interference mitigation, beamforming, and medium access control layer protocols to improve THz performance. This survey paper examines the use of AI in state-of-the-art THz communications, discussing the challenges, potentials, and shortcomings. Additionally, this survey discusses the available platforms, including commercial, testbeds, and publicly available simulators for THz communications. Finally, this survey provides future strategies for improving the existing THz simulators and using AI methods, including deep learning, federated learning, and reinforcement learning, to improve THz communications. Full article

(This article belongs to the Special Issue System Design and Signal Processing for 6G Wireless Communications)

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