Federated Unlearning (FUL) focuses on client data and computing power to offer a privacy-preserving solution. However, high computational demands, complex incentive mechanisms, and disparities in client-side computing power often lead to long times and higher costs. To address these challenges, many existing methods rely on server-side knowledge distillation that solely removes the updates of the target client, overlooking the privacy embedded in the contributions of other clients, which can lead to privacy leakage. In this work, we introduce DPUL, a novel server-side unlearning method that deeply unlearns all influential weights to prevent privacy pitfalls. Our approach comprises three components: (i) identifying high-weight parameters by filtering client update magnitudes, and rolling them back to ensure deep removal. (ii) leveraging the variational autoencoder (VAE) to reconstruct and eliminate low-weight parameters. (iii) utilizing a projection-based technique to recover the model. Experimental results on four datasets demonstrate that DPUL surpasses state-of-the-art baselines, providing a 1%-5% improvement in accuracy and up to 12x reduction in time cost.

Combining big data and deep learning can analyze large-scale breast cancer pathology images for auxiliary diagnosis. Furthermore, Whole Slide Images (WSIs) of breast cancer pathology offer detailed tissue feature information, which supports the accurate identification of malignant lesions. Current approaches combine Self-Supervised Learning (SSL) and Multiple Instance Learning (MIL) for WSI analysis, aiming to address the issues of billion-level pixels in a single WSI and the lack of precise annotations. However, pseudo-labels produced by SSL frequently lack accuracy, and MIL fails to effectively integrate global information at the WSI level, resulting in performance bottlenecks. This paper proposes the Multi-granularity Self-supervised Second-order MIL (MS2M) to tackle these issues. MS2M first achieves instance-level fine-grained feature learning through multi-granularity SSL and optimizes instance-level representations using bag-level labels within the MIL framework. Then, the transformer captures long-range dependencies between instances. When combined with second-order (covariance) pooling, it also captures high-order relational information. This process generates a robust bag-level representation. MS2M achieves accuracies of 0.9845 and 0.9719 on the CAMELYON16 and private breast cancer WSI datasets, respectively, outperforming existing methods.

Vision-Language Models (VLMs), with their advantages in vision and language processing, exhibit immense potential in mobile intelligent systems. Integrating federated learning with parameter-efficient fine-tuning of VLMs helps address data heterogeneity challenges. However, existing methods mainly focus on task-specific patterns, neglecting the impact of general features, such as background information and low-quality data, which weakens the model's ability to generalize when handling data from different sources and dealing with fluctuations in quality. To tackle these challenges, we propose Inverse Feature Consistency Federated Unlearning (IFCFU) for VLM, comprising three components: 1) Feature Consistency Federated Learning (FCFL) aligns fine-tuned features with pre-trained features through constraints to ensure the preservation of general features; 2) Pseudo-label Low-quality Data Detection (PLDD) identifies potential low-quality data through model quality assessment and pseudo-label generation; 3) Inverse Feature Consistency Unlearning (IFCU) distances low-quality data features from optimal model features to eliminate the negative impact and restores training with pseudo-labels. Evaluations on StanfordCars show that FCFL increased accuracy by 4.97% and 29.88% under normal data and low-quality data configurations, respectively. PLDD identified over 90.00% of low-quality data, while IFCU improved the global model's accuracy by 4.43% with 80% low-quality data.

Federated unlearning (FUL) facilitates targeted unlearning of data-specific artifacts from trained federated learning (FL) models. Existing methodologies primarily emphasize individual client demands at a time, such as enforcing the “right to be forgotten” or mitigating poor-quality data contributions from a single client. These strategies frequently rely on client-side computational engagement during unlearning. However, these approaches often neglect situations in which it is crucial to unlearn the contributions of multiple participants at a time from a global model. Therefore, we introduce a novel FUL method named “FULClean” to parallelly erase the adverse impacts of poor-quality data from multiple participants without using client resources and maintaining global model performance. FULClean employs a novel Contrastive Threshold-based Contribution Rectification (CTCR) mechanism, that (1) identifies and classifies the local models into unaffected and potentially affected local models, (2) computes the dynamic contribution threshold for each potentially affected model based on layer-wise parameter divergence, and (3) selectively replaces or remove contributions based on their affected ratio. FULClean can categorize and swiftly eliminate the impacts of poor-quality data from multiple participants on the global model. This can be accomplished without communication and utilization of the client's resources. Extensive experiments are also conducted on four distinct datasets with two different models to showcase the effectiveness and efficiency of FULClean.

Enhancing model performance on low-capacity devices remains a significant challenge in the Internet of Models (IoM). Inspired by the efficiency of disentangled representation learning, this study proposes a model decomposition approach to improve response time on low-capacity devices while maintaining accuracy, through collaborative learning with models deployed on higher-capacity devices. First, we introduce a divide-and-conquer strategy that decomposes and learns knowledge within each data sample. This enables lightweight sub-models, tailored to specific knowledge components, to respond efficiently on low-capacity devices in the IoM system. Second, we design a progressive crossfusion mechanism to promote mutual enhancement among these knowledge-specific sub-models. Third, we optimize the learning process by aligning the updates of these sub-models with those of the models on higher-capacity devices. This collaborative optimization is guided via knowledge distillation during model aggregation. Experimental results on image classification tasks demonstrate that our approach reduces response time by 9.87 % to 60.31 % without compromising accuracy.

Crowdsourced data refers to the information contributed by a large number of individuals, which may originate from various sources, including social media, online surveys, crowdsourcing tasks, etc. It is utilized for analysis and research across diverse scenarios. However, due to various subjective and objective factors, including the participants and sensing devices, the quality of the data collected for crowdsourcing tasks could be inconsistent. Therefore, how to filter out reliable information from the inconsistent data is crucial and difficult. Additionally, since participants consider their time and monetary costs, the crowdsourced datasets obtained are typically based on partial event observations, indicating a pronounced sparsity in the data. Current truth discovery methods struggle to adapt to datasets with varying levels of sparsity and lack effectiveness in evaluating and predicting sparse datasets that contain multiple judgments. In this article, we propose an adaptive hypergraph-based expectation-maximization (EM) truth discovery method for crowdsourced datasets with multiple judgments, named MHGEM (short for multidimensional-hypergraph EM). MHGEM leverages hypergraph topological metrics to model sparse datasets, enhancing the assessment of participant reliability and the prediction of truth for observed events. Experiments in both simulated and real-world scenarios demonstrate that MHGEM achieves higher predictive accuracy.

Monitoring renewable energy devices is crucial for the timely detection of faults and the improvement of system stability, making it a key component of the Internet of Things (IoT) ecosystem. However, existing intelligent algorithms and IoT methods rely on edge devices with limited computational capacity, which requires balancing real-time performance and accuracy. Additionally, most methods require initial training on large-scale data using cloud platforms or high-performance servers, leading to high initial costs. To address these challenges, we propose multimodal statistical prompt learning (MSPL) for new energy equipment defect recognition on IoT edge devices. This method enables rapid learning with only a few samples, avoiding the need for large-scale centralized training. Specifically, MSPL uses the pretrained contrastive language-image pretraining model as its backbone, leveraging text-based conceptual information to enhance the understanding of visual inputs. A statistical query module is implemented at the end of the backbone to extract distinctive features from the outputs, integrating these features with soft prompts to customize them for the defect recognition task. Since the learnable parameters are limited to soft prompts added at the end of the backbone, MSPL restricts gradient backpropagation to this point. This improves parameter and memory efficiency, making it more suitable for scenarios with limited computational capacity on IoT edge devices. Experimental results of MSPL on two renewable energy equipment defect datasets and edge devices indicate that it meets real-time processing requirements while maintaining high accuracy, outperforming other methods.

Internet of Things (IoT) technologies have been applied to fault detection in new energy equipment, which is crucial for ensuring the stable operation of energy systems. However, existing approaches typically rely on large amounts of labeled data to train intelligent algorithms, which are difficult to obtain in real-world. To address this challenge, this paper proposes a novel multi-modal few-shot defect recognition framework for new energy equipment, enabling data-efficient defect recognition in real-world scenarios through multi-modal harmony. Unlike previous multi-modal few-shot methods, it eliminates the necessity of pairwise similarity calculations, thereby simplifying the training and inference processes. Our approach trains a shared classifier through text and visual modality features integration. Initially, we extract feature vectors using text and visual encoders and then map them to common feature space. Subsequently, the vectors of these two modalities are used to train a shared classifier, which aids in the simultaneous learning of corresponding visual representations and conceptual information. Furthermore, to enhance interaction between modalities, the feature vectors of the text prompts are used to initialize the classifier weights, thereby promoting cross-modal consistency. Experiments on datasets of wind turbine blades and solar cells show that combining the two modalities improves recognition accuracy by up to 19.13% and 28.52% compared to other multi-modal few-shot methods. Despite its reliance on prompt quality, the approach provides an effective and scalable solution for defect recognition.

Anomaly detection is a fundamental component of intelligent monitoring in the Internet of Things (IoT), where accuracy, efficiency, and interpretability are critical requirements. However, existing methods often overlook the unique characteristics of IoT signals such as seasonality, trends, and irregular residual components, as well as the complex interactions among them. This oversight can lead to anomaly masking, increased false positives, and reduced interpretability in anomaly identification. Motivated by the effectiveness of disentangled representation learning, we propose TRAdetector, a novel disentangled reconstruction-based framework for IoT signals anomaly detection. TRAdetector explicitly models recurrent and consistent patterns, as well as irregular variations in the latent space by leveraging variational inference strategies, thereby enhancing probabilistic guidance in learning both regular and irregular temporal representations. A sparse coding strategy is incorporated within the latent space of the residual component to directly model inconsistent temporal fluctuations. Finally, a multihead cross-attention mechanism and a gated, decomposition-aware reconstruction strategy are designed to effectively model the complex interactions among different components. Extensive experiments show that our model achieves state-of-the-art performance on multiple benchmark datasets in terms of accuracy, efficiency, and interpretability.

Recent model recovery methods in federated unlearning (FUL) either rely on additional communication with the remaining clients or require large amounts of high-quality data from the server for training, overlooking scenarios with limited data resources. Currently, contrastive language-image pretraining (CLIP) has demonstrated remarkable performance across a wide range of tasks, particularly excelling in few-shot learning scenarios. In this article, inspired by CLIP, we explore the scenario of few-shot knowledge distillation and propose CLIP-guided few-shot knowledge distillation (CGKD) for model recovery in FUL. CGKD mainly consists of three components: 1) the unlearning module constructs the unlearning model by erasing all historical contributions of the target client, and this model is treated as the student model; 2) fine-tuning the pretrained CLIP model using few-shot data from the server side to obtain a more robust teacher model (CLIP$^{\mathbf {*}}$); and 3) model recovery is achieved through knowledge distillation, leveraging the rich visual and semantic knowledge of CLIP$^{\mathbf {*}}$to enhance the student model’s understanding of image semantic context, thereby improving the performance of the unlearning model. Extensive experimental results demonstrate that CGKD outperforms the compared FUL method in recovery performance across four standard datasets, validating the effectiveness of our approach.

Distributed machine learning over geo-distributed clouds enables joint training of data located in different regions, alleviating the burden of transferring large volumes of training datasets, which greatly saves bandwidth. However, the limited capacity of WAN links slows down the inter-cloud communications, which significantly decelerates the synchronization of distributed machine learning over geo-distributed clouds. Besides, the multi-tenancy in clouds results in multiple training tasks running simultaneously, whose synchronizations consistently compete for the limited WAN bandwidth with each other, which further aggravates the training performance of each task. While existing works optimize synchronizations through techniques like gradient compression, multi-resource interleaving and so on, none of them targets at the synchronization congestion especially due to multi-tenant learning, which results in inferior training performance.To solve these problems, we propose a simple but effective scheme, SCC, for fast and efficient multi-tenant learning via synchronization congestion control. SCC monitors the cross-cloud network conditions and evaluates the synchronization congestion level based on the round-trip transmission time for each synchronization. Then SCC alleviates synchronization congestion via controlling the synchronization frequency according to the synchronization congestion level in a probabilistic way. Extensive experiments are conducted within our testbeds consisted of 16 NVIDIA V100 GPUs to evaluate the performance of SCC, and comparison results show that SCC can reduce the average training completion time and makespan by up to 28.6% and 43.2% over SAP-SGD [1]. Targeted experiments are conducted to demonstrate the effectiveness and robustness of SCC.

Cooperative reconfigurable intelligent surfaces (RISs) are promising technologies for 6 G networks to support a great number of users. Compared with the fixed RISs, the properly deployed RISs may improve the communication performance with less communication energy consumption, thereby improving the energy efficiency. In this paper, we consider a cooperative unmanned aerial vehicle-mounted RISs (UAV-RISs)-assisted cellular network, where multiple RISs are carried and enhanced by UAVs to serve multiple ground users (GUs) simultaneously such that achieving the three-dimensional (3D) mobility and opportunistic deployment. Specifically, we formulate an energy-efficient communication problem based on multi-objective optimization framework (EEComm-MOF) to jointly consider the beamforming vector of base station (BS), the location deployment and the discrete phase shifts of UAV-RIS system so as to simultaneously maximize the minimum available rate over all GUs, maximize the total available rate of all GUs, and minimize the total energy consumption of the system, while the transmit power constraint of BS is considered. To comprehensively solve EEComm-MOF which is an NP-hard and non-convex problem with constraints, a non-dominated sorting genetic algorithm-II with a continuous solution processing mechanism, a discrete solution processing mechanism, and a complex solution processing mechanism (INSGA-II-CDC) is proposed. Simulations results demonstrate that the proposed INSGA-II-CDC can solve EEComm-MOF effectively and outperforms other benchmarks under different parameter settings. Moreover, the stability of INSGA-II-CDC and the effectiveness of the improved mechanisms are verified. Finally, the implementability analysis of the algorithm is given.

Recent federated unlearning studies mainly focus on removing the target client's contributions from the global model permanently. However, the requirement for accommodating temporary user exits or additions in federated learning has been neglected. In this paper, we propose a novel recoverable federated unlearning scheme, named RFUL, which allows users to remove or add their local model to the global one at any time easily and quickly. It mainly consists of two main components,i.e.,knowledge unlearning and knowledge recovery. In knowledge unlearning, the target contributions can be eliminated by training with mislabeled target data, while preserving the non-target contributions through distillation using the original model. In knowledge recovery, the forgotten contributions can be restored by training the target data using classification loss, while the non-target contributions are maintained through feature distillation and parameter freezing on the classifier. Both knowledge unlearning and recovery processes only require the participation of target data, guaranteeing the algorithm's practicality in federated learning systems. Extensive experiments demonstrate the significant efficacy of RFUL. For knowledge unlearning, RFUL matches state-of-the-art methods using only target data, achieving a runtime speedup of 3.3 to 8.7 times compared to retraining across various datasets. For knowledge recovery, RFUL exceeds state-of-the-art incremental learning methods by 5.02% to 29.97% in accuracy and achieves a runtime speedup of 1.8 to 4.4 times compared to retraining on different datasets.

Graph-learning methods, especially graph neural networks (GNNs), have shown remarkable effectiveness in handling non-Euclidean data and have achieved great success in various scenarios. Existing GNNs are primarily based on message-passing schemes, that is, aggregating information from neighboring nodes. However, the diversity and complexity of complex systems from real-world circumstances are not sufficiently taken into account. In these cases, the individual should be treated as an agent, with the ability to perceive their surroundings and interact with other individuals, rather than just be viewed as nodes in existing graph approaches. Additionally, the pairwise interactions used in existing methods also lack the expressiveness for the higher-order complex relations among multiple agents, thus limiting the performance in various tasks. In this work, we propose a Multiagent Hypergraph Force-learning method dubbed MHGForce. First, we formalize the multiagent system (MAS) and illustrate its connection to graph learning. Then, we propose a generalized multiagent hypergraph-learning framework. In this framework, we integrate message-passing and force-based interactions to devise a pluggable method. The method empowers graph approaches to excel in downstream tasks while effectively maintaining structural information in the representations. Experimental results on the Cora, Citeseer, Cora-CA, Zoo, and NTU2012 datasets in node classification demonstrate the effectiveness and generality of our proposed method. We also discuss the characteristics of the MHGForce and explore its role through parametric analysis and visualization. Finally, we give a discussion, conclude our work, and propose future directions.

By deploying distributed storage space on edge servers, mobile edge networks significantly enhance computation and transmission efficiency for wireless tasks. The selection of an appropriate caching policy not only optimizes bandwidth utilization but also alleviates network congestion. Given the intricate connectivity and vast data volume in edge computing, coupled with users’ demand for rapid response times, proposing a cache solution that closely matches data attributes becomes imperative to enhance overall efficiency. In this paper, we introduce RECG, a high-speed edge caching scheme designed specifically for graph data, leveraging the intricate data connectivity. RECG generates query graphs from edge servers to ensure swift and accurate identification of popular nodes. Additionally, we introduce a rapid hot-spot propagation partitioning technique to optimize the partitioning process, increasing the hit rate of partitioned subgraphs in the cache while reducing runtime. Our experimental evaluation, conducted on real-world datasets, compares RECG with specialized edge caching graph partitioning algorithms such as LGPE and other baseline algorithms. The thorough experimental results demonstrate the advantages of the proposed algorithm in terms of cache hit rate and processing delay.

Federated unlearning (FUL) is a solution aimed at addressing the problem of removing data contributions from trained federated learning (FL) models. Existing FUL methods only focus on iterative unlearning of clients’ contributions and fail to perform unlearning in scenarios where multiple clients request to remove their data at a time. Additionally, FUL still needs to address issues, including convergence speed, maintaining the global model’s performance, and parallel unlearning to expedite the unlearning process. To fill this gap, we introduce Federated Clients Forgetting (FedCF), a fast and accurate FUL method that can eliminate single client contributions similar to existing methods, eliminate multiple clients’ contributions on the global model parallelly, ensure the performance of the unlearned global model, and reduce the unlearning time. The key idea is to construct a temporary model by extracting knowledge from the remaining clients’ updates and adding it to the corresponding parameters of the initial global model and then leverage a temporary model to reconstruct the unlearned global model. Extensive experiments on three benchmark datasets, FedCF demonstrates its efficiency and effectiveness for single client contribution unlearning, achieving an average time efficiency of 8.3x, 6.5x, and 4.1x over existing methods FedRetrain, FedEraser, and FUL with knowledge distillation, respectively. Additionally, FedCF showcases the time efficiency and performance guarantee after unlearning the contributions of multiple clients in parallel.

Few-shot learning has become a key technical solution for addressing the challenges of limited data and difficult annotation acquisition in medical image classification. However, relying solely on a single image modality proves inadequate for capture conceptual categories. This paper proposes a novel medical image classification paradigm based on a multi-modal foundation model, called PM2. In addition to the image modality, PM2introduces supplementary text input (prompt) to further describe images or conceptual categories and facilitate cross-modal few-shot learning. We empirically studied five different prompting schemes under this new paradigm. Furthermore, linear probing in multi-modal models only takes class token as input, ignoring the rich statistical data contained in high-level visual tokens. Therefore, we alternately perform linear classification on the feature distributions of visual tokens and class token. To effectively extract statistical information, we use global covariance pool with efficient matrix power normalization to aggregate the visual tokens. We then combine two classification heads: one for handling image class token and prompt representations encoded by the text encoder, and the other for classifying the feature distributions of visual tokens. Experiments on two medical datasets demonstrate that regardless of the prompting scheme, our method PM2outperforms its counterparts, achieving state-of-the-art performance.

Unmanned aerial vehicles (UAVs)-enabled aerial communication provides a flexible, reliable, and cost-effective solution for a range of wireless applications. However, due to the high line-of-sight (LoS) probability, aerial communications between UAVs are vulnerable to eavesdropping attacks, particularly when multiple eavesdroppers collude. In this work, we aim to introduce distributed collaborative beamforming (DCB) into UAV swarms and handle the eavesdropper collusion by controlling the corresponding signal distributions. Specifically, we consider a two-way DCB-enabled aerial communication between two UAV swarms and construct these swarms as two UAV virtual antenna arrays. Then, we minimize the two-way known secrecy capacity and the maximum sidelobe level to avoid information leakage from the known and unknown eavesdroppers, respectively. Simultaneously, we also minimize the energy consumption of UAVs for constructing virtual antenna arrays. Due to the conflicting relationships between secure performance and energy efficiency, we consider these objectives as a multi-objective optimization problem. Following this, we propose an enhanced multi-objective swarm intelligence algorithm via the characterized properties of the problem. Simulation results show that our proposed algorithm can obtain a set of informative solutions and outperform other state-of-the-art baseline algorithms. Experimental tests demonstrate that our method can be deployed in limited computing power platforms of UAVs and is beneficial for saving computational resources.

Given flexible mobility, rapid deployment, and low cost, unmanned aerial vehicle (UAV)-enabled mobile edge computing (MEC) shows great potential to compensate for the lack of terrestrial edge computing coverage. However, limited battery capacity, computing and spectrum resources also pose serious challenges for UAV-enabled MEC, which shorten the service time of UAVs and degrade the quality of experience (QoE) of user devices (UDs) without effective control approach. In this work, we consider a UAV-enabled MEC scenario where a UAV serves as an aerial edge server to provide computing services for multiple ground UDs. Then, a joint task offloading, resource allocation, and UAV trajectory planning optimization problem (JTRTOP) is formulated to maximize the QoE of UDs under the UAV energy consumption constraint. To solve the JTRTOP that is proved to be a future-dependent and NP-hard problem, an online joint optimization approach (OJOA) is proposed. Specifically, the JTRTOP is first transformed into a per-slot real-time optimization problem (PROP) by using the Lyapunov optimization framework. Then, a two-stage optimization method based on game theory and convex optimization is proposed to solve the PROP. Simulation results validate that the proposed approach can achieve superior system performance compared to the other benchmark schemes.

Due to its practical integration with IoT networks and ability to remove specific data contributions from a trained model, federated unlearning (FUL) has become increasingly attractive for IoT sensing systems. However, existing FUL methods are inadequate for rollback (unlearning) in IoT sensing systems due to IoT devices' heterogeneity and the training process's dynamic nature. To address these issues, we propose “FedRollback”, a lightweight novel FUL method for efficient rollback in IoT sensing systems. The key idea is to compress and filter the retaining updates, dynamically adjust the adjustment retraining rounds, and weighted aggregation based on each user (IoT device) resource availability score. This approach reduces computational overhead, maintains model performance, mini-mizes storage overhead, and speeds up the rollback process by retraining the model in a few rounds based on adaptive intervals. Evaluations on four distinct datasets (i.e., MNIST, KMNIST, SVHN, and CelebA) show an approximately 11x average speed-up over retraining from scratch and 5x and 4x improvement over FedEraser and FedRemover, demonstrating its efficiency and robustness in real-world IoT data sensing systems.

Data privacy is becoming increasingly important as data becomes more valuable, as evidenced by the enactment of right-to-be-forgotten laws and regulations. However, in a federated learning (FL) system, simply deleting data from the database when a user requests data revocation is not sufficient, as the training data is already implicitly contained in the parameter distribution of the models trained with it. Furthermore, the global model in the FL system is vulnerable to data poisoning attacks by malicious nodes. Exploring a reliable data poisoning reversal method can effectively counter such attacks. In this article, we analyze the necessity of decoupling the processes of unlearning and training and propose a training-agnostic and efficient method that can effectively perform two types of unlearning tasks: 1) client revocation and 2) category removal. Specifically, we decompose the unlearning process into two steps: 1) knowledge erasure and 2) memory guidance. We first propose a novel knowledge erasure strategy called momentum degradation (MoDe) which realizes the erasure of implicit knowledge in the model and ensures that the model can move smoothly to the early state of the retrained model. To mitigate the performance degradation caused by the first step, the memory guidance strategy implements guided fine-tuning of the model on different data points, which can effectively restore the discriminability of the model on the remaining data points. Extensive experiments demonstrate that our method outperforms the existing task-specific algorithms and matches the performance of retraining, accelerating the execution time by 5–20 times compared to retraining on different data sets.

Federated Learning (FL), which has been employed to train machine learning models on the data with a distributed manner, could enhance the immersive user experience for the human-centric metaverse. However, it’s challenging to train machine learning models accurately and promptly with FL for the human-centric metaverse due to massive data communication and user unreliability. User experience could be negatively affected by using low-quality machine learning models for human-centric metaverse, e.g., it cannot scrutinize and arrive at decisions accurately and timely. To resolve this pressing issue, we propose MetaFul a federated unlearning solution which reduces the negative influences of low-quality data with no data transmission by removing low-quality training models at the server side. To be specific, MetaFul includes three main components. (i) Low-throughput federated learning (LT-FL) addresses the issue of large model transmission in FL by decreasing the dimension and the number of transmitted model parameters. (ii) Loss-based model quality assessment (LM-QA) utilizes the model loss generated in LT-FL to estimate user data quality. (iii) Non-communicative federated unlearning (NC-FUL) revokes the low-quality data impact on the FL model with careful designed federated unlearning at the server side. Both LM-QA and NC-FUL have no communications with clients. Finally, extensive evaluations are conducted to show MetaFul could improve the model accuracy by at least 2.5% and decrease the user perception time by at least 19.3% in human-centric metaverse compared to benchmarks.

Programmable switches allow data plane to program how packets are processed, which enables flexibility for network management tasks, e.g., packet scheduling and flow measurement. Existing studies focus on program deployment at a single switch, while deployment across the whole data plane is still a challenging issue, especially manifested in the difficulty in joint correct implementation of P4 programs, resource load balancing of network devices, and optimization of network performance. In this paper, we present RED, a Resource-Efficient and Distributed program deployment solution for programmable switches. First of all, we analyze data plane programs to estimate the resource utilization and divide them into two categories for further processing. Then, the proposed merging and splitting algorithms are selectively applied to merge or split the pending programs. Finally, we consolidate the scarce resources of the whole data plane for distributed program deployment. Extensive experiments with both testbed and large-scale simulations are conducted and comparison results show that 1) RED achieves network-wide resource balancing in a distributed way and the latency of processing packets within the switch was reduced by 16.7%. 2) RED improves the speedup by two orders of magnitude compared to P4Visor in merging program and merges more 18% tables than SPEED; 3) If the resources required to run a P4 program exceed the resource limit of the switch, it cannot be deployed on the switch. RED makes the overwhelmed programs to be deployed on switches and switch throughput increased by 10.7%.

Embedded real-time systems generally execute in a predictable and deterministic manner to deliver critical functionality within stringent timing constraints. However, the predictable execution behavior leaves the system vulnerable to schedule-based attacks. In this article, we present a multimode security-aware real-time scheduling scheme to counteract schedule-based attacks on multiprocessor real-time systems. To mitigate the vulnerability to the schedule-based attack, we propose a multimode scheduling method to reduce the accumulative attack effective window (AEW) of multiple victim tasks and prevent the untrusted tasks from executing during the AEW by distinctively scheduling mixed-trust tasks according to the system mode. To avoid the protection degradation due to the excessive blocking of untrusted tasks, we introduce a protection window for multiple victims on multiprocessors by analyzing the system protection capability limit under the system schedulability constraint. Furthermore, to maximize the protection capability of the multimode security-aware scheduling strategy on a multiprocessor platform, we also propose a security-aware packing algorithm to balance the workloads of mixed-trust tasks on different processors using a mixed-trust worst-fit decreasing heuristic strategy. The experimental results demonstrate that our proposed approach significantly outperforms the state-of-the-art method. Specifically, the AEW ratio and the AEW untrusted execution time ratio are reduced by 18.8% and 62.8%, respectively, while the defense success rate against ScheduLeak attack is improved by 16.3%.

In this paper, we investigate an unmanned aerial vehicle (UAV)-assistant air-to-ground communication system, where multiple UAVs form a UAV-enabled virtual antenna array (UVAA) to communicate with remote base stations by utilizing collaborative beamforming. To improve the work efficiency of the UVAA, we formulate a UAV-enabled collaborative beamforming multi-objective optimization problem (UCBMOP) to simultaneously maximize the transmission rate of the UVAA and minimize the energy consumption of all UAVs by optimizing the positions and excitation current weights of all UAVs. This problem is challenging because these two optimization objectives conflict with each other, and they are non-concave to the optimization variables. Moreover, the system is dynamic, and the cooperation among UAVs is complex, making traditional methods take much time to compute the optimization solution for a single task. In addition, as the task changes, the previously obtained solution will become obsolete and invalid. To handle these issues, we leverage the multi-agent deep reinforcement learning (MADRL) to address the UCBMOP. Specifically, we use the heterogeneous-agent trust region policy optimization (HATRPO) as the basic framework, and then propose an improved HATRPO algorithm, namely HATRPO-UCB, where three techniques are introduced to enhance the performance. Simulation results demonstrate that the proposed algorithm can learn a better strategy compared with other methods. Moreover, extensive experiments also demonstrate the effectiveness of the proposed techniques.

Federated learning (FL) offers a credible solution for distributed data trading since it could train machine learning models in a distributed manner thereby enhancing data privacy without sharing local data. However, it is still challenging to trade data through FL due to unfair model allocation issues arising from the unreliability of user-provided data. To tackle it, we propose F2UL, a Fairness-aware Federated UnLearning solution that distributes models to users commensurate with their data quality. F2UL is trained in a two-stage (TST) way and contains three main components: 1) Label-free model quality assessment (LMQA) promotes fairness by evaluating models without user-specific data, ensuring uniform assessment standards. 2) Fair model distribution (FMD) addresses the issue of unfair model distribution by allocating models with feature mapping deviation, ensuring that users who contribute low-quality models do not receive enhanced models. 3) User data federated unlearning (UDFU) ensures fairness in model distribution by employing rapid recovery federated unlearning, safeguarding regular users from the adverse effects of low-quality data on model performance. In experiments on CIFAR10, F2UL reduces the low-quality data user accuracy to 9.09% and increases regular users’ accuracy by 3.02%, thereby demonstrating F2UL's capacity to ensure fairness in data trading.

Unmanned Aerial Vehicle (UAV)-enabled mobile edge computing has been proposed as an efficient task-offloading solution for user equipments (UEs). Nevertheless, the presence of heterogeneous UAVs makes centralized navigation policies impractical. Decentralized navigation policies also face significant challenges in knowledge sharing among heterogeneous UAVs. To address this, we present the soft hierarchical deep reinforcement learning network (SHDRLN) and dual-end federated reinforcement learning (DFRL) as a decentralized navigation policy solution. It enhances overall task-offloading energy efficiency for UAVs while facilitating knowledge sharing. Specifically, SHDRLN, a hierarchical DRL network based on maximum entropy learning, reduces policy differences among UAVs by abstracting atomic actions into generic skills. Simultaneously, it maximizes the average efficiency of all UAVs, optimizing coverage for UEs and minimizing task-offloading waiting time. DFRL, a federated learning (FL) algorithm, aggregates policy knowledge at the cloud server and filters it at the UAV end, enabling adaptive learning of navigation policy knowledge suitable for the UAV's performance parameters. Extensive simulations demonstrate that the proposed solution not only outperforms other baseline algorithms in overall energy efficiency but also achieves more stable navigation policy learning under different levels of heterogeneity of different UAV performance parameters.

Mobile crowdsensing leverages the power of a vast group of participants to collect sensory data, thus presenting an economical solution for data collection. However, due to the variability among participants, the quality of sensory data varies significantly, making it crucial to extract truthful information from sensory data of differing quality. Additionally, given the fixed time and monetary costs for the participants, they typically only perform a subset of tasks. As a result, the datasets collected in real-world scenarios are usually sparse. Current truth discovery methods struggle to adapt to datasets with varying sparsity, especially when dealing with sparse datasets. In this article, we propose an adaptive Hypergraph-based EM truth discovery method, HGEM. The HGEM algorithm leverages the topological characteristics of hypergraphs to model sparse datasets, thereby improving its performance in evaluating the reliability of participants and the true value of the event to be observed. Experiments based on simulated and real-world scenarios demonstrate that HGEM consistently achieves higher predictive accuracy.

Federated unlearning (FUL) is an emerging distributed machine learning paradigm which enables the removal or unlearning of specific training data effects from trained Federated Learning (FL) models. While current studies mostly focus on client-side FUL to address the “right to be forgotten”, and ignore the server's right to remove local models from the global model, particularly when clients are trained with low-quality data. In this paper, we introduce the Server-Initiated Federated Unlearning (SIFU) algorithm, devised to eliminate low-quality data from the global model. SIFU consists of two main components: (i) Identifying low-quality data: we develop a category-based method for quantifying low-quality data for each client and filter out clients containing such data. Datasets are then divided accordingly. (ii) Unlearning low-quality data: we employ gradient ascent training to counteract the adverse effects of low-quality data on local models. To minimize any bias introduced, we concurrently perform several batches of boosting training with good-quality data. SIFU could identify and promptly eliminate the impact of low-quality data on the FL global model while still preserving the benefits of good-quality data. Finally, extensive evaluations are conducted to verify the performance of SIFU with four different kinds of datasets and models. Results show that, compared to retraining from scratch, SIFU accelerates the speed of unlearning by 15× for small datasets (i.e., MNIST and FMNIST) and 20× for large datasets (i.e., CIFAR-10 and CelebA) without any degradation in accuracy, which also outperforms the state of the arts.

Unmanned aerial vehicles (UAVs)-aided device-to-device (D2D) networks have attracted great interests with the development of 5G/6G communications, while there are several challenges about resource scheduling in UAVs-aided D2D networks. In this work, we formulate a UAVs-aided D2D network resource scheduling optimization problem (NetResSOP) to comprehensively consider the number of deployed UAVs, UAV positions, UAV transmission powers, UAV flight velocities, communication channels, and UAV-device pair assignment so as to maximize the D2D network capacity, minimize the number of deployed UAVs, and minimize the average energy consumption over all UAVs simultaneously. The formulated NetResSOP is a mixed-integer programming problem (MIPP) and an NP-hard problem, which means that it is difficult to be solved in polynomial time. Moreover, there are trade-offs between the optimization objectives, and hence it is also difficult to find an optimal solution that can simultaneously make all objectives be optimal. Thus, we propose a non-dominated sorting genetic algorithm-III with a Flexible solution dimension mechanism, a Discrete part generation mechanism, and a UAV number adjustment mechanism (NSGA-III-FDU) for solving the problem comprehensively. Simulation results demonstrate the effectiveness and the stability of the proposed NSGA-III-FDU under different scales and settings of the D2D networks.

Anomaly detection aims to identify data or behav-iors that are different from the usual patterns. In traditional anomaly detection settings, edge devices collect the data and send it to a centralized server for model training, which faces two critical issues: (1) it risks data exposure during transmission; (2) it demands a large amount of network bandwidth for data transfer. To tackle these problems, we propose a Visual Federated Learning algorithm (VFLA) for anomalous behavior identification in the multi-UAVs system. To the best of our knowledge, we are the first to merge federated learning with video-based anomaly detection. VFLA consists of two phases: The initial phase is training a pseudo-label generator. UAVs collect a dataset and manually annotate it. This labeled data is then used to train the pseudo-label generator on the server, which is subsequently distributed back to the UAVs. The second phase is the federated learning-based anomaly detection model training. UAVs leverage the pseudo-label generator to automatically annotate the collected video footage. These annotated videos are fed into an anomaly detection network for training. Once the local training is completed, UAVs upload their local models to a server for federated aggregation. The global model is then redistributed to the UAVs for additional training rounds, until reach the target accuracy. Finally, we simulate the federated learning anomaly detection algorithm on the Shanghai-tech dataset, it demonstrates an average accuracy boost of 5.6% compared to baselines.

Urban tracking plays a vital role for people’s urban life in intelligent transportation systems, e.g., public safety, case investigation, finding missing items, etc. However, the current tracking methods consume a large amount of communication and computing resources since they mainly offload all related sensing data, i.e., videos, generated by widely deployed cameras to the cloud where data are stored, processed, and analyzed. In this paper, we propose a graph optimized data offloading algorithm leveraging a crowd-AI hybrid method to minimize the data offloading cost and ensure the reliable urban tracking result. To be specific, we first formulate a crowd-AI hybrid urban tracking scenario, and prove the proposed data offloading problem in this scenario is NP-hard. Then, we solve it by decomposing the problem into two parts, i.e., trajectory prediction and task allocation. The trajectory prediction algorithm, leveraging the state graph, computes possible tracking areas of the target object, and the task allocation algorithm, using the dependency graph, chooses the optimal set of crowds and cameras to cover the tracking area while minimizing the data offloading cost separately. Finally, the extensive simulations with large real world data set are conducted showing that the proposed algorithm outperforms benchmarks in reducing data offloading cost while ensuring the tracking success rate in intelligent transportation systems.

In this paper, we studied a data caching problem in edge-based CDNs to facilitate the content delivery to serve a sequence of requests, off-line and online, with minimum costs as a goal based on a semi-homo cost model. To this end, we first designed an O(mn \log(mn)) time and space optimal proactive off-line algorithm,called pro-caching, by reducing the problem to a simple shortest path problem in a directed weighted network graph, and then extended the idea of anticipatory caching to develop an 2-competitive reactive online algorithm, called re-caching, for this problem and showed its tightness by proving that no deterministic online algorithm can do better than 2-o(1) in its worst case. Finally, to combine the advantages of both algorithms, we also presented a hybrid algorithm, called hy-caching, to fully utilize the power and benefits of edge-based CDNs while reducing their service costs. Our results improve the previous results not only in the cost model being used but also in the time complexity, competitive ratio, and the quality of the solutions. We provably achieve these results with our deep insights into the problem and the careful analysis, together with an empirical evaluation.

Wireless Rechargeable Sensor Networks (WRSNs) with perpetual network lifetime have been used in many Internet of Things (IoT) applications, like oceanic monitoring and precision agriculture. Rechargeable sensors, together with an Unmanned Aerial Vehicle (UAV), are collaboratively employed for fulfilling periodic coverage missions. However, traditional coverage solutions are normally based on static deployment of sensors and not suitable for such novel coverage requirements. In this paper, we propose the concept of Period-Area Coverage (PAC) problem, which requires the data of the overall area must be collected/monitored periodically. To solve the PAC problem, we employ a UAV that simultaneously acts as a mobile charger and sensor. It is responsible for charging nearly exhausted sensors and sensing vacant regions to realize complete event monitoring. To maximize the energy efficiency of the UAV, we propose a heuristic hexagon-based scheduling algorithm (HSA) which can also balance energy consumption. Furthermore, we develop an emergent node charging scheduling method to prevent node exhaustion, and introduce a grid-based boustrophedon scheduling algorithm (GBSA) to reduce the complexity. Finally, we present a charging re-allocation mechanism to further enhance energy efficiency. Extensive simulations demonstrate that the proposed schemes can solve the PAC problem and enhance energy efficiency by at least 18.2% compared to prior arts. Test-bed experiments conducted both in agriculture and oceanic monitoring applications validate the applicability of the proposed scheme in practical scenarios.

Wireless rechargeable sensor networks have become a hot research issue as it can overcome the limited energy bottleneck of wireless sensor networks owing to the recent breakthrough of wireless power transfer technology. Though network lifetime is prolonged and sensor nodes can sustain immortally, the issue of network robustness is overlooked, yielding most theoretical work unsuitable for practical applications when confronting with unpredictable packet loss. In this paper, we address the network robustness issue by maximizing the charging utility in a risk-averse view. First, we build a risk-averse model based on the concept of CVaR (Conditional Value at Risk), which trades-off charging utility and risk aversion for quantifying robustness. Then, we propose a spatial discretization scheme to construct a charging route for mobile charger, which can reduce computational overhead. Afterwards, a path optimization scheme is designed to further improve the charging utility. We convert the original problem into the submodular function maximization problem and propose a method with a performance guarantee while maximizing the system robustness. Finally, testbed experiments and simulations are conducted, and the results demonstrate that our schemes outperform comparison algorithms by at least 22.4% in effective energy in the presence of risks to guarantee system robustness.

The ubiquitous and fine-grained features of WiFi signals make it promising for realizing contactless authentication. Existing methods, though yielding reasonably good performance in certain cases, are suffering from two major drawbacks: sensitivity to environmental dynamics and over-dependence on certain activities. Thus, the challenge of solving such issues is how to validate human identities under different environments, even with different activities. Toward this goal, in this article, we develop WiTL, a transfer learning–based contactless authentication system, which works by simultaneously detecting unique human features and removing the environment dynamics contained in the signal data under different environments. To correctly detect human features (i.e., human heights used in this article), we design a Height EStimation (HES) algorithm based on Angle of Arrival (AoA). Furthermore, a transfer learning technology combined with the Residual Network (ResNet) and the adversarial network is devised to extract activity features and learn environmental independent representations. Finally, experiments through multi-activities and under multi-scenes are conducted to validate the performance of WiTL. Compared with the state-of-the-art contactless authentication systems, WiTL achieves a great accuracy over 93% and 97% in multi-scenes and multi-activities identity recognition, respectively.

Automotive systems are often subjected to stringent requirements on the maximum data age of certain cause-effect chains. In this paper, we present an efficient method for formally analyzing maximum data age of cause-effect chains. In particular, we decouple the problem of bounding the maximum data age of a chain into a problem of bounding the releasing interval of successive Last-to-Last data propagation instances in the chain. Owing to the problem decoupling, a relatively tighter data age upper bound can be effectively obtained in polynomial time. Experiments demonstrate that our approach can achieve high precision analysis with lower computational cost.

Wireless Rechargeable Sensor Networks (WRSNs) have become an important research issue as it can overcome the energy bottleneck problem of wireless sensor networks. However, inaccurate discretization methods and imprecise charging models yield a huge gap between theoretical results and practical applications, making it difficult for wide adoptions. In this paper, we focus on designing a precise charging method for maximizing charging utility when line-of-sight (LOS) and none-line-of-sight (NLOS) charging cases exist in complicated environments. First, we design discretization methods for charging area and charging orientation for precisely constructing the charging model. Then, we develop a novel electromagnetic wave reflection model to describe the signal propagation model in the presence of obstacles. We formalize the mobile charging problem into a submodular function maximization problem which can be solved by a proposed algorithm with an approximation guarantee. Finally, extensive experiments and simulations demonstrate that our schemes outperform comparison algorithms by 31.45% on average in charging utility in complicated environments.

The discovery of wireless power transfer technology enables power transferred between transceivers in a wireless manner, thus generating the concept of wireless rechargeable sensor networks (WRSNs). Previous arts paid little attention to network security issues, making them prone to novel attacks. In this work, we focus on developing a denial of charge attack for WRSNs, which aims at corrupting network functionalities by manipulating the malicious mobile charger. We formalize the maximization of destructiveness problem (MAD) and propose a denial of charge attacking method, termed MDoC, with a performance guarantee to solve it. MDoC is composed of two attacking rounds, which first triggers sensors to send requests to create a request explosion phenomenon and then figures out the longest charging route to yield nodes starving to death as much as possible. Finally, extensive testbed experiments and simulations are conducted to verify the performance of MDoC. The results reveal that MDoC attack is able to exhaust at least 20% additional nodes without being noticed.

Subset selection problem for task scheduling with general cost constraints exists widely in IoT applications. Its objective is to select several profitable tasks to execute under routing and cost constraints such that the total profit is maximized. Most prior arts only focus on either online tasks or offline tasks, which are usually inapplicable in practical applications where online tasks and offline tasks co-exist. In this paper, we study the subset selection problem for HybrId Task Scheduling with general cost constraints (HITS), in which both online and offline tasks are scheduled to maximize the overall profit. We first divide the HITS problem into online and offline subproblems and propose two algorithms to solve them with bounded approximation ratios. Furthermore, we propose an approximation algorithm for the hybrid scenario where both online and offline tasks are considered. Extensive simulations show that our proposed algorithm outperforms baseline algorithms by 21.5% averagely in profit and also performs well in pure online/offline scenarios. We further demonstrate the feasibility of our algorithm through test-bed experiments in a realistic scene.

Wireless Sensor Networks (WSNs) and Cloud Computing have received tremendous attention from both academia and industry. Sensor-Cloud is the product of combining WSNs and Cloud Computing together, which integrates edge computing and artificial intelligence technologies recently. This workshop provides a forum for academic researchers and industry practitioners to exchange the most recent progress in methods and applications in sensor-cloud systems.

The machine learning performance usually could be improved by training with massive data. However, requesters can only select a subset of devices with limited training data to execute federated learning (FL) tasks as a result of their limited budgets in today’s IoT scenario. To resolve this pressing issue, we devise a blockchain-enhanced FL market (BFL) to$(i)$make data in computationally bounded devices available for training with social Internet of things,$(ii)$maximize the amount of training data with given budgets for an FL task, and$(iii)$decentralize the FL market with blockchain. To achieve these goals, we firstly propose a trust-enhanced collaborative learning strategy (TCL) and a quality-oriented task allocation algorithm (QTA), where TCL enables training data sharing among trusted devices with social Internet of things, and QTA allocates suitable devices to execute FL tasks while maximizing the training quality with fixed budgets. Then, we devise an encrypted model training scheme (EMT) based on a simple but countervailable differential privacy methodology to prevent attacks from malicious devices. In addition, we also propose a contribution-driven delegated proof of stake (DPoS) consensus mechanism to guarantee the fairness of reward distribution in the block generation process. Finally, extensive evaluations are conducted to verify the proposed BFL could improve the total utility of requesters and average accuracy of FL models significantly.

As an epoch-making technology, wireless power transfer incredibly achieves energy transmission wirelessly, enabling reliable energy supplement for Wireless Rechargeable Sensor Networks (WRSNs). Existing methods mainly concentrate on performance improvement theoretically, neglecting the fact that most Commercial Off-The-Shelf (COTS) rechargeable sensors (e.g., WISP and Powercast) are not allowed to conduct sensing and energy harvesting tasks simultaneously, termedcharging exclusivity. Therefore, their schemes are not feasible for practical applications. In this paper, we focus on the charging exclusivity issue in stochastic events monitoring while improving network performance. In specific, we pay close attention to trading off charging and sensing tasks and formulate a combinatorial optimization problem with routing constraints. We introduce novel discretization techniques and investigate the routing problem to reformulate the original problem into maximization of a submodular function. With a slightly relaxed budget, the output of our proposed algorithm is better than$(1-1/e)/2$of the optimal solution to the original problem with a smaller charging radius$(1-\xi)D_{c}$. Through extensive simulations, numerical results show that in terms of charging utility, our algorithm outperforms baseline algorithms by 21.3% on average. Moreover, we conduct test-bed experiments to demonstrate the feasibility of our scheme in real scenarios.

The rapid popularization of wireless power transfer (WPT) technology promotes the wide adoption of wireless rechargeable sensor networks (WRSNs). Traditional methods only focus on how to optimize network performance, and most of them overlook the energy waste issue induced by WPT. In this paper, we explore the potentials of recycling wasted energy when using WPT by means of freeloading. Specifically, with a slight modification on hardware, we expand the functionality of the mobile chargers (MCs), enabling them to harvest and recycle the WPT-induced wasted energy in the air to serve more sensors, which promotes energy efficiency. We model the problem, termed MEFree, as maximizing network energy efficiency by utilizing a limited number of freeloading MCs and scheduling their freeloading behaviors. Through jointly scheduling freeloading and charging tasks, the proposed scheme is able to solve the problem with a (1 − 1/e)/2 approximation ratio with a slightly relaxed budget. Extensive simulations are conducted and corresponding numerical results show that our proposed scheme significantly improves network energy efficiency by at least 18.8% and outperforms baseline algorithms by 19.1% on average in various aspects. Our test-bed experiments further demonstrate the practicability of our scheme in actual scenes.

Accurate traffic prediction is of great importance in Intelligent Transportation System. This problem is very challenging due to the complex spatial and long-range temporal dependencies. Existing models generally suffer two limitations: (1) GCN-based methods usually use a fixed Laplacian matrix to model spatial dependencies, without considering their dynamics; (2) RNN and its variants are only capable of modeling a limited-range temporal dependencies, resulting in significant information loss. In this paper, we propose a novel spatial-temporal graph neural network (STNN), an end-to-end solution for traffic prediction that simultaneously captures dynamic spatial and long-range temporal dependencies. Specifically, STNN first uses a spatial attention network to model complex and dynamic spatial correlations, without any expensive matrix operations or relying on predefined road network topologies. Second, a temporal transformer network is utilized to model long-range temporal dependencies across multiple time steps, which considers not only the recent segment, but also the periodic dependencies of historical data. Making full use of historical data can alleviate the difficulty of obtaining real-time data and improve the prediction accuracy. Experiments are conducted on two real-world traffic datasets, and the results verify the effectiveness of the proposed model, especially in long-term traffic prediction.

The current Internet content delivery model assumes strict mapping between a resource and its descriptor, e.g., a JPEG file and its URL. Content Distribution Networks (CDNs) extend it by replicating the same resources across multiple locations, and introducing multiple descriptors. The goal of this work is to build Web-LEGO, an opt-in service, to speedup webpages at client side. Our rationale is to replace the slow original content with fast similar or equal content. Further, we perform a reality check of this idea both in term of the prevalence of CDN-less websites, availability of similar content, and user perception of similar webpages via millions of scale automated tests and thousands of real users. Then, we devise Web-LEGO, and address natural concerns on content inconsistency and copyright infringements. The final evaluation shows that Web-LEGO brings significant improvements both in term of reduced Page Load Time (PLT) and user-perceived PLT. Specifically, CDN-less websites provide more room for speedup than CDN-hosted ones, i.e., 7x more in the median case. Besides, Web-LEGO achieves high visual accuracy (94.2%) and high scores from a paid survey: 92% of the feedback collected from 1,000 people confirm Web-LEGO's accuracy as well as positive interest in the service.

Data caching in the cloud is an efficient way to improve the QoS of diverse data applications. However, this benefit is not freely available, given monetary cost to manage the caches in the cloud. In this paper, we study the data caching problem in the cloud that is driven by the monetary cost reduction, instead of the hit rate under limited capacity as in traditional cases. In particular, given a stream of requestsRto a shared data item, we present a shortest-path based optimal algorithm that can minimize the total transfer and caching costs within O(mn) time for off-line case, here m represents the number of nodes in the network, while n is the length of the request stream. The cost model in this computation is semi-homo, which indicates that all pairs of nodes have the same transfer cost, but each cache server node has its own caching cost rate. Our off-line algorithm improves the previous results not only in reducing the time complexity from O(m2n) to O(mn), but also in relaxing the cost model to be semi-homogeneous, rendering the algorithm more practical in reality. Furthermore, we also study this problem in its online form, and by extending the anticipatory caching idea, we propose a 2-competitive online algorithm based on the same cost model and show its tightness by giving a lower bound of the competitive ratio as 2 - o(1) for any deterministic online algorithm. We provably achieve these results with our deep insights into the problem and careful analysis of the solution algorithms, together with a trace-based study to evaluate their performance in reality.

Governments of the world have invested a lot of manpower and material resources to combat COVID-19 this year. At this moment, the most efficient way that could stop the epidemic is to leverage the contact tracing system to monitor people's daily contact information and isolate the close contacts of COVID-19. However, the contact tracing data usually contains people's sensitive information that they do not want to share with the contact tracing system and government. Conversely, the contact tracing system could perform better when it obtains more detailed contact tracing data. In this article, we treat the process of collecting contact tracing data from a crowdsourcing perspective in order to motivate users to contribute more contact tracing data and propose the incentive algorithm named CovidCrowd. Different from previous works where they ask users to contribute their data voluntarily, the government offers some reward to users who upload their contact tracing data to reimburse the privacy and data processing cost. We formulate the problem as a Stackelberg game and show there exists a Nash equilibrium for any user given the fixed reward value. Then, CovidCrowd computes the optimal reward value which could maximize the utility of the system. Finally, we conduct a large-scale simulation with thousands of users and evaluation with real-world data set. Both results show that CovidCrowd outperforms the benchmarks, e.g., the user participating level is improved by at least 13.2% for all evaluation scenarios.

Past years have witnessed the rapid increasing number of smart devices and objects deployed in the urban environment. Leveraging helpful data generated by hundreds of millions of smart objects, a large number of services in the Internet of Things (IoT) are devised and developed to improve our urban life quality. However, uploading the unprecedented volume of sensing data from IoT sensors to the cloud directly can lead to huge unnecessary consumption and hurt the quality of IoT services. This work leverages the fog architecture to devise a task-driven data offloading (TDO) algorithm in urban IoT services. Specifically, a three-layer urban IoT service architecture is proposed, and the TDO process is formulated as a combination optimization problem taking task deadlines and abilities of fog devices into consideration. Then, we prove the TDO problem is NP-hard, and the G-TDO algorithm is devised to solve it with a careful designed utility function. Also, we propose RG-TDO algorithm to improve the G-TDO algorithm considering the overlaps of tasks. Finally, we demonstrate the significant performance of the proposed algorithms with extensive evaluations based on real-world data set.

Abstract In the study of human action recognition, two-stream networks have made excellent progress recently. However, there remain challenges in distinguishing similar human actions in videos. This paper proposes a novel local-aware spatio-temporal attention network with multi-stage feature fusion based on compact bilinear pooling for human action recognition. To elaborate, taking two-stream networks as our essential backbones, the spatial network first employs multiple spatial transformer networks in a parallel manner to locate the discriminative regions related to human actions. Then, we perform feature fusion between the local and global features to enhance the human action representation. Furthermore, the output of the spatial network and the temporal information are fused at a particular layer to learn the pixel-wise correspondences. After that, we bring together three outputs to generate the global descriptors of human actions. To verify the efficacy of the proposed approach, comparison experiments are conducted with the traditional hand-engineered IDT algorithms, the classical machine learning methods (i.e., SVM) and the state-of-the-art deep learning methods (i.e., spatio-temporal multiplier networks). According to the results, our approach is reported to obtain the best performance among existing works, with the accuracy of 95.3% and 72.9% on UCF101 and HMDB51, respectively. The experimental results thus demonstrate the superiority and significance of the proposed architecture in solving the task of human action recognition.

With increasing more powerful sensing capacities of mobile devices, the Mobile Crowd Sensing (MCS) system requires to collect larger sensing data from participants. Nevertheless, collecting such large volume of data will cost a lot for participants, base stations and MCS server. Even worse, some sensing data cannot satisfy the MCS sensing requirement due to the low quality and are filtered by the MCS server in clouds. Inspired by the D2D technique, where mobile devices can communicate directly with the help of the nearby base station, in 5G networks, we propose the Reliable Data Collection (RDC) algorithm to validate the generated sensing data at device sides in this paper. To be specific, the whole progress is formulated as a Probability problem of Discovering Reliable sensing data (PDR) at client sides, and Expectation Maximization (EM) is leveraged to devise the algorithm. Finally, the extensive simulations and real-world use case are conducted to evaluate the performance of RDC algorithm, and the result shows that RDC outperforms the other two benchmarks in estimating accuracy and saving data collection cost.

Today's webpages development cycle consists of constant iterations with the goal to improve user retention, time spent on site, and overall quality of experience. Big companies like Google, Facebook, Amazon, etc. invest a lot of time and money to perform online testing. The prohibitive costs of these approaches are an entry barrier for smaller players. Further, the lack of a substantial user-base can be problematic to ensure statistical significance within a reasonable duration. In this paper we propose Kaleidoscope, an automated tool to evaluate Web features at a large scale, quickly, accurately, and at a reasonable price. Kaleidoscope can test two crucial user-perceived Web features - the style and page loading. As far as we know, it is the first testing tool to replay page loading by controlling visual changes on a webpage. Kaleidoscope allows to concurrently load a webpage in two versions (e.g., different fonts, with vs without ads) that are shown to a participant side-by-side. Further, Kaleidoscope also allows a participant to interact with each webpage version and provide feedback, e.g., respond to a questionnaire previously prepared by an "experimenter". Kaleidoscope supports both voluntary and paid testers from FigureEight, a popular crowdsourcing platform. Using hundreds of FigureEight testers, we validate that Kaleidoscope matches the accuracy of trusted in-lab tests while providing results about 12x faster (and arguably at a lower cost) than A/B testing. Finally, we showcase how to use Kaleidoscope's page loading feature to study the user-perceived page load time (uPLT) of a webpage.

With the emerging of sharing economy, taxi crowdsourcing delivery could be a feasible solution for logistics companies to deliver packages efficiently and securely with a lower cost in the urban area. In this paper, we propose LSTM2V, a novel mobility pattern-aware task recommendation algorithm for taxi crowdsourcing delivery leveraging the long short-term memory and Markov model. Taking the mobility pattern into consideration, LSTM2V leverages both deep learning and probabilistic model to recommend the most suitable tasks to taxis. It mainly consists of two components - the feature window based Long Short-Term Memory neural network (LSTM-w) and SpatioTemporal Markov (STM) model. The taxi mobility pattern is predicted by LSTM-w, and STM is utilized to predict locations which taxis can visit in the future. Extensive evaluations with real taxi trajectory dataset show LSTM2V can predict the mobility pattern precisely, improve the multi-location prediction accuracy, and recommend tasks efficiently.

Urban crowdsourced transportation, which can solve traffic problem within city, is a new scenario where citizens share vehicles to take passengers and packages while driving. Differing from the traditional location based crowdsourcing system (e.g., crowdsensing system), the task has to be completed with visiting two different locations (i.e., start and end points), so task allocation algorithms in crowdsensing cannot be leveraged in urban crowdsourced transportation directly. To solve this problem, we first prove that maximizing the crowdsourcing system’s profit (i.e., maximizing the total saved distance) is an NP-hard problem. We propose a heuristic greedy algorithm called Saving Most First (SMF) which is simple and effective in assigning tasks. Then, an optimized SMF based genetic algorithm (SMF-GA) is devised to jump out of the local optimal result. Finally, we demonstrate the performance of SMF and SMF-GA with extensive evaluations, based on a large scale real vehicle traces. The evaluation with large scale real dataset indicates that both SMF and SMF-GA algorithms outperform other benchmark algorithms in terms of saved distance, participant profits, etc.

Opportunistic networks are lack of end-to-end paths between source nodes and destination nodes, so the communications are mainly carried out by the “store-carry-forward” strategy. Selfish behaviors of rejecting packet relay requests will severely worsen the network performance. Incentive is an efficient way to reduce selfish behaviors, and hence improves the reliability and robustness of the networks. In this paper, we propose the Node-dependence-based Dynamic gaming Incentive (NDI) algorithm, which exploits the dynamic repeated gaming to motivate nodes relaying packets for other nodes. The NDI algorithm presents a mechanism of tolerating selfish behaviors of nodes. Reward and punishment methods are also designed based on the node dependence degree. Simulation results show that the NDI algorithm is effective on increase the delivery ratio and decrease average latency when there are a lot of selfish nodes in the opportunistic networks.