Nowadays, unmanned aerial vehicle (UAV) communication systems are commonly considered as one of the key enabling technologies for 6G. The hybrid free space optical (FSO)/radio frequency (RF) system has the advantages of both FSO and RF links to improve communication system performance, and the relay-assisted system adopts multi-hop transmission and cooperative diversity methods to extend communication coverage. Thus, a joint consideration of UAV-assistedUAV assisted relay in hybrid FSO/RF transmission is meaningful. In this paper, we aim to analyze the performance of UAV-assisted multi-hop parallel hybrid FSO/RF communication systems with and without pointing errors (PE) in terms of Bit Error Rate (BER) and outage probability. In our considered system, the FSO sub-link adopts the Exponential Weibull turbulence model and the RF sub-link suffers the Nakagami fading model. With these, new mathematical formulas of both BER and outage probability are derived under the UAV-assisted hybrid FSO/RF with different modulation methods. Through numerical evaluationnumerical simulations, the performances of UAV-assisted hybrid FSO/RF systems are analyzed under different weather conditions, modulation methods, optical receiver aperture, RF fading parameters, pointing errors, and relay structures. The results demonstrate that (1) compared to hybrid FSO/RF direct links, UAV-assisted hybrid FSO/RF systems can further improve system performance; (2) the performance of UAV-assisted hybrid FSO/RF systems varies with different relay structures; (3) large receiver aperture and RF fading parameters can further improve the communication performance of hybrid FSO/RF direct links and UAV-assisted hybrid FSO/RF systems.

In this paper, an online truthful mechanism is designed for mobile crowdsensing systems. Traditionally, the scenario where participants arrived at the platform in an online manner was widely discussed in existing works. On contrary, we focus on random task arrivals case to design an online truthful mechanism by jointly considering the cost budget and the requirement of sensed data of each participant. Specifically, when the task arrives, the platform must make decisions in a sequence to select a specific number of participants to obtain a better competitive ratio. To address this issue, an online strategy proof incentive mechanism is designed to minimize the social cost of the whole system and achieve truthfulness by applying the auction framework. Moreover, in order to further improve the competitive ratio of the online algorithm, a more efficient online scheme is proposed if more information on the participants is available at the platform. Theoretical and simulation results demonstrate the effectiveness of our proposed online truthful mechanisms.

In this article, we consider incentive mechanism designs in asynchronous federated learning (FL) systems. With the consideration of unique characteristics inherent in asynchronous FL, such as dynamic participating and multiminded IoT nodes such as mobile users (MUs), requirements of model training (i.e., training accuracy and convergence time), and limited uplink bandwidth, we formulate considered system as an online incentive mechanism design problem, where each MU is not only a buyer for communication resource but also a seller for computation service. To address the challenges involved in the design, we first derive the relationship between the number of participants and the global training accuracy in asynchronous FL. Then, based on that, we propose a novel mechanism, called the online incentive mechanism for asynchronous FL (OIMAF). To the best of our knowledge, this is the first work to design incentive mechanisms for asynchronous FL. Furthermore, in order to obtain a more robust mechanism, an improved online mechanism, called the two-shot-based online incentive mechanism (TOIM), is proposed by using OIMAF as a building block. Theoretical analyses show that our proposed online incentive mechanisms can guarantee individual rationality, truthfulness, a sound performance, and solution feasibilities. We further conduct comprehensive simulations to validate the effectiveness of our proposed mechanisms.

In the operational context of a cross-device federated learning (FL), the efficient allocation of resources, such as transmission powers, channels, and computation resources, significantly impacts overall performance. Existing research in cross-device FL has predominantly concentrated on either resource allocation to enhance training accuracy or incentivizing participation, while ignoring their integrated designs for further improving the performance in cross-device FL. Different from existing work, in this paper, we jointly integrate the power allocation, channel assignment, user selection, and allocation of computation frequency into the design of incentive mechanism, where each mobile user plays a dual role as both a buyer and a seller. Because of complex resource allocation, truthfulness guarantee in a dual role scenario, and unavailable prior information, the considered mechanism design problem is challenging. To tackle such combinatorial problem, we propose a Reinforcement Auction Mechanism (RAM), comprising two layers. The upper layer features a Hybrid Action Reinforcement Learning scheme to learn the outcomes of user selection and payments. In the lower layer, each selected mobile user optimizes its resources to maximize its utility. Theoretical analyses affirm that our proposed RAM ensures individual rationality and truthfulness. Extensive simulations have been conducted to validate the effectiveness of the proposed RAM.

Tracking vital signs during sleeping is important because the breathing and heart rates can be used to detect breathing diseases and heart disorders. However, existing work for breathing and heart rates estimations only considered long-term data, while ignoring the fact that people could turn over frequently in practice, which results in different data lengths of breathing and heart rates signals. In addition, most systems based on channel state information (CSI) only adopted either amplitude or phase information to select sub-carrier, which could degrade the performance of breathing and heart rates estimations. In this paper, in order to improve the performance, we first propose a new sub-carrier selection method by jointly considering the CSI amplitude and phase information. Then, based on the proposed sub-carrier selection scheme, a new breathing and heart rates estimations scheme is proposed under the consideration of different data lengths, where the peak detection and the FFT-based methods are respectively used for long-term and short-term breathing signals, while the FFT-based method is used to estimate the heart rate for both long-term and short-term signals. Experiment results demonstrate that our work can achieve accuracies of 96.1% and 94.3% for breathing and heart rates estimations.