While earables present a promising avenue for cardiac sensing, whether they may replace the stethoscope to perform heart sound (a.k.a. PCG) monitoring remains questionable. The latest effort attempts to generate PCG-like waveform out of in-ear audio collected via earphones, yet its data-driven approach does not seem to be grounded in the underlying physics. To this end, this paper introduces EarPCG, a system for continuous PCG monitoring leveraging physics-informed neural models. As opposed to the debatable belief that bone-conducted PCG appears within ear canal, EarPCG generates PCG waveforms from the (actually existing) photoplethysmography (PPG) waveforms conveyed via blood vessels. Arising from pressure variations induced by heartbeats, PPG can be mathematically described by a Partial Differential Equation (PDE). Therefore, solving this PDE inversely may reconstruct cardiac dynamics and in turn enable the generation of PCG waveforms with another PDE characterizing the pressure oscillations propagating through soft tissues. Pipelining the two PDE-solving neural models, EarPCG achieves accurate PCG monitoring from in-ear audio, while requiring minimal training. Our extensive experiments leveraging a custom-built prototype demonstrate the efficacy of our proposed system. Furthermore, we have conducted clinical trials, with clinicians reporting no perceptible difference between authentic PCG and the sounds reconstructed by EarPCG.

Many reconnaissance missions require a group of mobile terminals (such as soldiers, mobile robots, and unmanned boats) to jointly operate within a region which is far away from the command centre. When a critical event occurs and is detected by a terminal, it is often required for the terminal to upload some critical data to the command centre (or via the satellite). As the bandwidth of the upload link is usually low due to the long distance, uploading the critical data often has long latency. To reduce the latency, a feasible way is to utilize the nearby terminals’ idle uplinks to help with the upload process, which requires the terminal’s data to be disseminated to other terminals as soon as possible. This is a new dissemination problem because the data being disseminated is also partially being uploaded, which seems as a noveldata-leakingdissemination problem. To solve it, we propose LHDS (Low-latency Heterogeneous Dissemination Scheduling) scheme by transforming the problem into two special sub-problems, i.e., constructing a special degree-decreasing tree with maximum multichild nodes, and designing a leaking-sustained dissemination schedule for each subtree. Extensive simulation experiments have been conducted on LHDS as well as two heuristic algorithms (i.e.,DBOandS-GA) designed for baselines. The results show that LHDS scheme significantly outperforms theDBOandS-GAalgorithms in terms of total collaborative data uploading latency, with saving 41% and 42% latency on average, respectively.

The big data era has accelerated the development of artificial intelligence (AI). The Model-as-a-Service (MaaS) paradigm has been used to address the substantial challenges associated with the organization and development of AI services. However, the successful delivery of complete AI applications is contingent upon the robust collaboration between microservice architectures and AI services. In this case, hybrid orchestration of AI services and microservices is highly necessary, but it still brings challenges. Furthermore, due to the heterogeneity of servers, resource competition, and multi-instance, the difficulty of hybrid orchestration modeling is enlarged. When considering intricate service dependencies among AI services and microservices, the tight coupling of deployment and routing leads to complex joint optimization problems, vastly aggravating the pressure of hybrid orchestration. Nonetheless, extant literature largely failed to address the intricate competitive and collaborative relationships between AI services and microservices, and fine-grained latency analysis with multi-instance modeling in hybrid orchestration problem. Therefore, we study joint deployment and routing for hybrid AI services and microservices in heterogeneous edge. Firstly, we conduct a precise analysis of latency and energy consumption, based on queuing networks and multi-instance models. Secondly, we propose a reinforcement learning method based on potential functions and segmented rewards (PS_SAC) to optimize end-to-end latency and system energy consumption, achieving efficient hybrid orchestration. Finally, through extensive simulation experiments, the algorithm demonstrates significant advantages in reducing latency, improving resource utilization, and lowering system energy consumption.

Service meshes built upon ubiquitous microservice architectures, as an emerging paradigm, promise to enhance the flexibility, scalability, and portability of energy-consuming and latency-sensitive applications in edge with limited resources. However, due to intricate microservice dependencies, service multiplexing, and parallel distributed instances, microservice deployment and request routing are highly interdependent. To reduce response latency and energy consumption, such collaborative optimization for efficient service mesh orchestration is necessary, but significantly challenging. Besides, strict service level objective (SLO) requirements and f ine-grained latency analysis with multi-nest routing further impose great difficulties to online orchestration. When considering multi instance modeling and multi-hop data communications for numerous microservices, the difficulty is extremely amplified. Nevertheless, most prevailing work failed to design sophisticate models and methods for addressing the above difficulties, and ignored the inherent transmission energy consumption for highly-concurrent multi-hop data interactions. Therefore, this paper investigates the energy aware service mesh deployment and online request routing in edge. First, we establish a multi-instance queuing network model to accurately analyze the end-to-end response latency with complicated dependencies and multi-hop communications, and optimize energy consumption in a fine-grained manner. Then, to boost the overall performance, we design an efficient multi-dimensional hierarchical deep reinforcement learning algorithm, which enables edges and service instances to cooperate with each other to handle massively concurrent requests. Besides, we propose an energy-aware proactive autoscaling algorithm to carefully adapt to exceedingly dynamic scenarios. Finally, extensive experiments are performed to show our superior performance compared to other baselines.

The rapid development of AI accelerates the implementation and delivery of AI applications in diverse fields. In cloud-edge collaboration, delivering a complete AI application relies on the robust coordination between AI-supporting microservices and AI services. However, most existing studies only coarsely considered monolithic AI service orchestration while neglecting microservice orchestration. Such coarse-grained orchestration severely impacts application performance. To enable diverse high-performance AI applications, fine-grained hybrid orchestration of AI services and microservices (HOAIM) is highly desirable, yet presents formidable challenges. Due to heterogeneous services, call dependencies, and service multiplexing, fine-grained hybrid orchestration modeling is highly non-trivial. Moreover, the tight coupling between deployment and routing results in a complex joint optimization problem. To address this, we first propose a heterogeneous service orchestration network that supports orchestration optimization and automated management. Then, based on queuing networks and multi-instance models, we conduct an accurate analysis of delay and load. Furthermore, to achieve efficient hybrid orchestration, we propose preference-driven resource allocation and instance computation algorithms, along with reinforcement learning with action masking and reward shaping. Finally, extensive trace-driven simulations demonstrate that our algorithms optimize average response delay by up to 41.83%, and achieve significant advantages in load balancing, response success rate, and resource efficiency.

Low Earth Orbit (LEO) satellite networks, with their low latency, high bandwidth, and global coverage, are becoming key technologies for applications like real-time video transmission. As satellite networks expand, effectively managing multicast traffic and optimizing bandwidth utilization have become major challenges for efficient video distribution. Although Software-Defined Multicast (SDM) technology has made progress in bandwidth optimization, existing SDM methods are still focused on constructing Steiner trees, making it difficult to address the dynamic changes and high-load issues in LEO satellite networks. This paper frames the multicast tree construction problem as a Joint Path Optimization Game (JPOG). We propose a Cooperative Game-Theoretic Routing (CGMR) Algorithm based on game theory, which optimizes multicast path selection and achieves load balancing by introducing a link cost-sharing mechanism. Additionally, we propose a two-stage A* path generation algorithm to improve path search efficiency. Theoretically, this paper proves that JPOG is a potential game and can converge to a pure strategy Nash equilibrium (PSNE) within a finite number of iterations. The results showed that JPOG outperformed other algorithms, achieving lower link load, path cost, and superior load balancing, demonstrating its effectiveness in optimizing multicast routing and resource management in large-scale LEO satellite networks.

Microservice as a promising architecture has been widely employed in edge computing to support sensitive-latency online applications. Unfortunately, the deployment of numerous microservices creates complex invocations and requires frequent communications, which brings significant challenges to service deployment and request routing. Moreover, the strict requirements for low energy consumption and low latency in edge computing further exacerbate these difficulties. In this case, it is crucial to optimize the joint microservices deployment and request routing using a meticulous and energy-efficient approach. However, existing studies often overlook their interdependence and treat them as separate problems. Therefore, we propose a fine-grained approach in this paper to jointly optimize the deployment and request routing of microservices within edge computing scenarios. First, we utilize queuing networks to conduct detailed modeling and mathematical analysis that study the complex invocation relationships, microservice instance sharing, and communication latency. Second, we propose an energy-efficient microservice orchestration algorithm, referred to as Cluster-Processing-based Adaptive Memory Procedure. This algorithm maintains a memory storing elite solution elements, and it iteratively picks up suitable elements from the memory to construct superior solutions. Finally, extensive simulation experiments demonstrate that the proposed algorithm outperforms baseline algorithms significantly in terms of response latency and energy consumption.

The rapid proliferation of Internet of Things (IoT) devices has increased the variety of devices and data traffic, making data management and analysis more complex. This complexity has raised the demand for efficient device identification methods to ensure the smooth operation of the network. Conventional identification methods rely on Machine Learning (ML) and Deep Learning (DL), which either suffer from unstable feature engineering or rely on large labeled datasets with confined representation. To overcome these shortcomings, generic hybrid representations of raw traffic are essential for precise device identification. Additionally, existing work mainly investigated device identification in clouds, incurring high network latency and computation costs. A few studies have identified IoT devices in edge, but such methods used simple neural networks, resulting in incomplete representation and redundant operations. Comprehensive representations typically require complex models, but the limited resources at the edge are insufficient to execute these models. Therefore, this paper proposes a lightweight hybrid device identification (LHDI) approach, which achieves efficient device identification in resource-constrained edge nodes. First, we adopt the unsupervised pre-training to enhance the characterization of network packets. Second, we devise LHDI by integrating bidirectional long short-term memory (Bi-LSTM) and Transformerbased blocks in a parallel configuration. Third, a pruning framework is introduced to automatically reduce Transformer parameters using structured sparsity methods without retraining. By reducing redundant neural network parameters, the proposed lightweight model facilitates effective device identification in edge, without losing representation capabilities. Experimental results demonstrate that our methods deliver high accuracy with low cost compared to others.

The deployment of the microservice architecture in edge networks presents new opportunities for supporting latency-sensitive network services. However, most such services are both computation-intensive and energy-consuming, posing significant challenges for edge nodes with constrained computing resources and energy supply. Therefore, designing efficient microservice orchestration strategies to reduce service latency and network energy consumption is essential but highly challenging. Due to frequent communication among microservices, service deployment and request routing are tightly coupled, which lead to a complex joint optimization problem. This complexity further increases when considering large-scale microservices under multi-instance modeling and fine-grained analysis. Nevertheless, previous work has failed to address these challenges and largely overlooked the balance between latency and energy consumption. To overcome these issues, this paper proposes an energy-latency balanced microservice orchestration method to jointly minimize service latency and energy usage. First, we adopt multi-instance modeling to enable precise end-to-end latency analysis, and integrate an energy model to quantify overall network consumption. Then, we design the Node Ranking Matrix-based Microservice Orchestration Algorithm (NRMA), which dynamically selects high-ranking nodes based on centrality and energy metrics, thereby balancing latency and energy in the deployment stage. Moreover, we use the proportional routing strategy that distributes user request traffic according to the number of deployed instances, preventing node overload and reducing cross-node communication. Experimental results show that the proposed method is significantly better than the baseline algorithms in terms of latency and energy consumption, and achieves significant results.

Biometrics has been increasingly integrated into wearables for enhanced data security in recent years. Meanwhile, wearable popularity offers a unique chance to capture novel biometrics via embedded sensors. In this article, we study new intracorporal biometrics combining the uniqueness of heart motion, bone conduction, and body asymmetry. Specifically, we introduce HeartPrint, a passive yet secure user authentication system exploiting the bone-conducted heart sounds captured by (widely available) dualin-ear microphones (IEMs). To eliminate interference, we devise a novel method combining modified non-negative matrix factorization and adaptive filtering. This extracts clean heart sounds while addressing interference of body sounds and audio produced by the earphones. We further explore the uniqueness of IEM-recorded heart sounds in three aspects to extract a novel biometric representation, based on which HeartPrint leverages a convolutional neural model equipped with a continual learning method to achieve accurate authentication under drifting body conditions. Furthermore, user-friendly registration and energy-effective authentication are facilitated by a data augmentation method using transformer-based GAN and an authentication interval control method. Extensive experiments with 45 participants confirm that HeartPrint can achieve 1.6% FAR and 1.8% FRR, while effectively coping with major attacks, complicated interference, and hardware diversity, while exhibiting robustness in real-world environments.

As a cornerstone for numerous sensing applications, wireless indoor localization has been a pivotal area of research over the last two decades. While techniques such as jamming, spoofing, and adversarial perturbation have been exploited to compromise wireless indoor localization, existing attacks face challenges in accessibility to wireless systems and stealthiness. To address these limitations, we introduceLoki, a novel physical-world attack on wireless indoor localization via differentiable object placement. Specifically, we develop a differentiable wireless ray-tracing technique that allows us to optimize object placement in the scene. By repositioning an existing object in the scene by just a few centimeters,Lokifools existing wireless indoor localization systems into generating erroneous localization results. We also show via experiments that the object placement generated byLokialigns with wireless sensing theory (e.g., the forward scattering region and Fresnel zone), confirming its explainability. Additionally,Lokiproves effective across various localization models and scenarios, highlighting its generalizability.

As a classic data processing tool, Principal Component Analysis (PCA) has been widely applied in various data analysis applications. To mitigate the high computational complexity of PCA on big data, distributed PCA methods have been extensively studied, which disperse the computational tasks across multiple computation units while guaranteeing the accuracy. For the scenarios of distributed PCA in wireless networks, as the data is originally dispersed across different locations, it is further required to reduce the communication cost of distributed PCA in networks, which however has been seldom studied. Reducing the communication cost of distributed PCA in wireless networks requires not only appropriately partitioning the computation of PCA, ensuring accuracy, but also effectively assigning the partitioned computations and routing strategies to the nodes. In this paper, we propose CD-PCA, a communication-efficient distributed PCA (CD-PCA) scheme. This scheme implements a transmission-benefit equipartition strategy for the network to facilitate high-accuracy distributed computation and designs novel routing strategies for nodes to execute the distributed PCA within each partitioned region. Extensive simulation results demonstrate that the proposed CD-PCA scheme can reduce transmission costs by over 30% on average compared to related methods and baseline approaches.

Lightweight microservices as a software architecture have been widely adopted in online application development. However, in highly-concurrent microservice scenarios, frequent data communications, complex call dependencies, and dynamic delay requirements bring great challenges to efficient microservice orchestration. In this case, service deployment and request routing are interactively-coupled in multi-instance modeling, and cannot be locally optimized effectively, thereby enlarging the difficulty for collaborative orchestration. To accommodate time-varying request properties and dynamic microservice multiplexing, orchestration schemes are frequently adapted to real-time parallel request queues, further complicating the difficulty. Nevertheless, most previous work failed to propose appropriate models and methods for the above issues. Therefore, this paper investigates the online microservice orchestration with probabilistic routing for dynamic call graphs in clouds. First, we formulate the time-slot-based joint optimization problem as a Markov Decision Process. The open Jackson queuing networks are used to accurately establish multi-instance models and analyze the request queuing, processing, and communicating delays. Then, we propose an efficient curiosity-driven deep reinforcement learning algorithm, which meticulously implements instance-level orchestration through multi-dimensional collaborative decisions and multi-time-scale trigger events. Finally, through comprehensive trace-driven experiments, our proposed approach significantly outperforms other baselines in terms of orchestration cost and resource utilization.

Service mesh architectures are emerging as a promising microservice paradigm for developing online cloud applications. However, in large-scale microservice scenarios, frequent service communications, intricate call dependencies, and stringent latency requirements bring great pressure to efficient service mesh orchestration. In this case, the problems of service deployment and request routing based on service mesh architectures are tightly-coupled and interdependent, and cannot be effectively optimized individually, enlarging the difficulty for collaborative orchestration. When microservice multiplexing, parallel dependencies, and multi-instance modeling are considered, the difficulty is further aggravated. Nonetheless, most existing work failed to propose appropriate models and methods for the above challenges. Therefore, this article studies the large-scale service mesh orchestration with probabilistic routing and constrained bandwidths for parallel call graphs. We leverage the open Jackson queuing network theory to capture crucial microservices and analyze request processing, queuing, and communication latency for massive user requests in a fine-grained way. Then, this article proposes an efficient three-stage heuristic, which achieves elegant multi-instance consolidation and probabilistic multi-queue routing to reduce response latency and cost. We also provide the algorithm complexity and mathematical analysis of the performance. Finally, extensive trace-driven experiments are performed to validate the superiority of our proposed algorithm over other baselines.

Aerial Acoustic Communication (AAC) has attracted much attention recently due to its ubiquitous device support. However, the transmission rate has largely throttled the boom of AAC-enabled applications. In this paper, we propose a high-speed AAC system that modulates messages over the entire bandwidth but is unobtrusive to end users. We achieve high bandwidth efficiency through a dynamic modulation mechanism. Specifically, we propose a high-order phase-based modulation mechanism on existing audio channels. Additionally, we leverage the auditory masking effect to embed data streams over the unused frequency band. Through a sophisticated power analysis and frequency allocation scheme, the changes made by these two modulation techniques on existing audio can be imperceptible to human ears. Furthermore, we utilize the loose orthogonal modulation on the inaudible channel to further boost the transmission rate. Our system prototype reveals that we can achieve up to 2 kbps link rate.

Stress tracing is an important research domain that supports many applications, such as health care and stress management; and its closest related works are derived from stress detection. However, these existing works cannot well address two important challenges facing stress detection. First, most of these studies involve asking the users to wear physiological sensors to detect their stress states, which has a negative impact on the user experience. Second, these studies have failed to effectively utilize the multimodal physiological signals, which results in less satisfactory detection results. This article formally defines the stress tracing problem, which emphasizes the continuous detection of human stress states. A novel deep stress tracing (DST) method, named DST, is presented. Note that, DST proposes tracing human stress based on the physiological signals collected by a noncontact ultrawideband radar, which is more friendly to users when collecting their physiological signals. In DST, a signal extraction module is carefully designed at first to robustly extract the multimodal physiological signals from the raw RF data of the radar, even in the presence of body movement. Afterward, a multimodal fusion module is proposed in DST to ensure that the extracted multimodal physiological signals can be effectively fused and utilized. Extensive experiments are conducted on the three real-world data sets, including one self-collected data set and two publicity data sets. Experimental results show that the proposed DST method significantly outperforms all the baselines in terms of tracing human stress states. On average, DST averagely provides a 6.31% increase in detection accuracy on all the data sets, compared with the best baselines.

Door lock is regarded as a critical line of defending the privacy and security of personal areas. However, for inner doors in environments like factories, existing locking mechanisms can be poor in user-friendliness and high in cost. For instance, mechanical locks require carrying keys that inevitably compromise user experiences, while smart locks always require non-trivial sensors. Therefore, inner doors urgently require a lightweight unlocking scheme that can properly balance user-friendliness, cost, and security. To this end, we propose HandKey as a keyless unlocking scheme to supplement existing lock systems. HandKey relies on two principles: the simplicity of hand knocking doors and the uniqueness of vibration triggered by the knocking force. In other words, a door and a hand knocking it jointly form a unique physical system that generates hand-dependent and user-specific vibration signatures uniquely representing a user identity. In designing HandKey, we first analyze the vibration mechanism behind it and the impacts of gestures and door materials on vibration signatures. Then we innovatively construct a signal processing and deep learning-based pipeline to extract signatures robust to variable knocking behaviors for representing user identity. Finally, we implement a HandKey prototype and use extensive evaluation to demonstrate its security and effectiveness.

The emerging low earth orbit (LEO) broadband satellite networks are creating new opportunities to enable superior video distribution. With numerous satellites deployed, broadband constellations are capable of distributing videos across the globe by efficient multicasting techniques. However, existing work only studied IP multicast for broadband constellations, which suffer from limited scalability and tree performance. With recent breakthroughs in software defined networking, novel software defined multicasting (SDM) techniques manage to achieve efficient data transfer through intelligent and granular management, outperforming traditional IP Multicast. This paper leverages software defined multicasting in the promising broadband constellations to empower satellite-based Internet video distribution. Based on rectilinear Steiner trees, this paper proposes a novel software defined multicasting framework for broadband satellite networks. In addition, this paper designs simple, agile, and scalable multicast segment routing protocols implementing source routing and equal cost multipath routing. The proposed protocols also adapt to frequent member updates and network failures with efficient tree recovery and local rerouting mechanisms. Comprehensive experiments demonstrate the effectiveness and efficiency of our approach when compared with traditional algorithms.

Acoustic-based respiration sensing is promising due to its ubiquitous device support and great freedom in signal design. However, existing proposals often either fail to function properly when a target is non-static or is under multipath interference, or address it in an algorithmic manner. To this end, in this paper, we propose CORA, a COntinuous RespirAtion monitoring system using purely analytical signal processing methods. CORA is the first approach that achieves physical separation between motion artifacts and respiration, other than existing algorithmic solutions, and hence can obtain results that are closer to ground truth. CORA leverages the edges of Orthogonal Time Frequency Space signals in monitoring motion states and addressing multipath interference. The ability to tackle these challenges can help to compensate motion-induced artifacts for FMCW-based sensing techniques, enabling continuous respiration monitoring even in non-static scenarios. To achieve high-quality compensation, a pipeline of signal processing techniques is proposed, including robust moving target tracking, accurate frequency bin selection, and effective phase denoising. Unlike existing deep learning-based approaches, CORA is explainable and is readily deployable, without sophisticated adaptation or exhausted training processes. We have implemented a system prototype and evaluated its performance. Experiment results demonstrate a median error of 0.86 respiration per minute.

Microservices as an emerging architecture are creating new opportunities to enable superior network services in Mobile Edge Computing (MEC). In the presence of huge amounts of user requests, the massive communications among microservices have become notoriously complicated. Due to the intricate data dependencies of the microservices, the overall performance of large-scale MEC applications simultaneously depends on both service deployment and request routing. However, most existing work ignores the interdependencies of microservices and studies the deployment and routing as two isolated problems. In this case, this paper investigates the joint optimization of service deployment and request routing in edge computing. We first formulate a delay minimization problem via mixed integer linear programming and queuing analysis, and then provide a hardness proof on the problem. In addition, this paper presents a 2-approximation algorithm, followed with rigorous mathematical proofs to demonstrate the approximation ratio. The proposed two-phase algorithm consists of rounding based service deployment and adaptive-scaling-based request routing policies, which employ fine grained joint optimization to minimize service response delay. Finally, we illustrate the near-optimal performance of the proposed algorithm via comprehensive experiments.

With the wide adoption of versatile IoT devices, device providers may desire to locate users around those devices to plan context-aware intelligence, which may improve the quality of daily life. As most IoT devices are WiFi enabled, the WiFi-based indoor positioning system is supposed to achieve this future scene. However, the state-of-the-art WiFi indoor positioning systems face challenges when being practically deployed as they may have to tradeoff between, say accuracy and computational overhead. In light of this, this article mainly introduces PLP-Track, a practical lightweight passive indoor tracking system based on channel state information (CSI) fingerprints. To settle the low granularity of fingerprints in distinguishing different positions, we propose a fingerprint preprocessing algorithm based on unsupervised learning and incorporate this algorithm with a state-space model to enable lightweight real-time tracking. Our implementation and evaluation of commodity WiFi devices demonstrate that PLP-Track can achieve indoor localization with high accuracy and low-computation cost.

Acoustic sensing has attracted significant attention recently, thanks to the pervasive availability of device support. However, adopting consumer-grade devices (e.g., smartphones) to deploy acoustic sensing applications faces the challenge of device/OS heterogeneity. Researchers have to pay tremendous efforts in tackling platform-dependent details even in simply accessing raw audio samples, thus losing focus on innovating sensing algorithms. To this end, this paper presents the first Acoustic Software Defined Platform (ASDP): a versatile sensing and general benchmarking platform. ASDP encompasses several customized acoustic modules running on a ubiquitous computing board, backed by a dedicated software framework. It is superior to commodity devices in controlling and reconfiguring physical layer settings, thus offering much better usability. The tailored software framework abstracts platform details and provides user-friendly interface for fast prototyping, while maintaining adequate programmability. To demonstrate the usefulness of ASDP, we showcase several relevant applications based on it. The promising outcomes make us believe that the release of our ASDP could greatly advance acoustic sensing research.

Though measuring ambient temperature is often deemed as an easy job, collecting large-scale temperature readings in real-time is still a formidable task. The recent boom of network-ready (mobile) devices and the subsequent mobile crowdsourcing applications do offer an opportunity to accomplish this task, yet equipping commodity devices with ambient temperature sensing capability is highly non-trivial and hence has never been achieved. In this paper, we proposeAcousticThermometer (AcuTe+) as an interference-resilient ambient temperature sensor empowered by a single commodity smartphone. AcuTe+ utilizes on-board dual microphones to estimate air-borne sound propagation speed, thereby deriving ambient temperature. To accurately estimate sound propagation speed, we leverage the phase of chirp signals to circumvent the low sample rate on commodity hardware. In addition, we propose to use both structure-borne and air-borne propagations to address the multipath problem. Most importantly, we equip AcuTe+ with a mask-based desnoising algorithm to handle intensive acoustic interference. As a mobile, economical, highly accurate sensor, AcuTe+ may potentially enable many relevant applications, in particular large-scale indoor/outdoor temperature monitoring in real-time. We have conducted extensive experiments on AcuTe+; the results demonstrate a median error of 0.6$^\circ$C even under severe acoustic interference (overall median 0.3$^\circ$C), and they also showcase the practical ability of AcuTe+ in real-time distributed temperature sensing.

Human activity recognition (HAR) plays a critical role in a wide range of real-world applications, and it is traditionally achieved via wearable sensing. Recently, to avoid the burden and discomfort caused by wearable devices, device-free approaches exploiting radio-frequency (RF) signals arise as a promising alternative for HAR. Most of the latest device-free approaches require training a large deep neural network model in either time or frequency domain, entailing extensive storage to contain the model and intensive computations to infer human activities. Consequently, even with some major advances on device-free HAR, current device-free approaches are still far from practical in real-world scenarios where the computation and storage resources possessed by, for example, edge devices, are limited. To overcome these weaknesses, we introduce HAR-SAnet which is a novel RF-based HAR framework. It adopts an original signal adapted convolutional neural network architecture: instead of feeding the handcraft features of RF signals into a classifier, HAR-SAnet fuses them adaptively from both time and frequency domains to design an end-to-end neural network model. We apply point-wise grouped convolution and depth-wise separable convolutions to confine the model scale and to speed up the inference execution time. The experiment results show that the recognition accuracy of HAR-SAnet substantially outperforms the state-of-the-art algorithms and systems.

Proliferation of smart environments entails the need for real-time and ubiquitous human-machine interactions through, mostly likely, hand/arm motions. Though a few recent efforts attempt to track hand/arm motions in real-time with COTS devices, they either obtain a rather low accuracy or have to rely on a carefully designed infrastructure and some heavy signal processing. To this end, we propose SoM (Sound of Motion) as a lightweight system for wrist tracking. Requiring only a smart watch-phone pair, SoM entails very light computations that can operate in resource constrained smartwatches. SoM uses embedded IMU sensors to perform basic motion tracking in the smartwatch, and it depends on the fixed smartphone to act as an "acoustic anchor": regular beacons sent by the phone are received in an irregular manner due to the watch motion, and such variances provide useful hints to adjust the drifting of IMU tracking. Using extensive experiments on our SoM prototype, we demonstrate that the delicately engineered system achieves a satisfactory wrist tracking accuracy and strikes a good balance between complexity and performance.

Aerial acoustic communication attracts substantial attention for its simplicity and cost-effectiveness. Unfortunately, the preferred inaudible transmission has to strike a balance between the transmission rate and communication range, when the Bit-Error-Rate (BER) is under a certain threshold. Additionally, the performance of previous proposals can be deteriorated by dynamic channel conditions including near-far problem, device heterogeneity, and multipath fading. To this end, we propose a High-speed, long-range, and Robust Chirp Spread Spectrum (HRCSS) scheme for inaudible aerial acoustic communication under dynamic channels. HRCSS innovates in the definition of a loose orthogonality condition, and it leverages this orthogonality to overlap multiple chirp carriers in a single time duration to form a data symbol representing multiple bits, thereby substantially promoting the data rate. To further enhance system robustness in long communication ranges and dynamic channel conditions, we construct a lightweight rate adaptation algorithm and design a simple yet efficient normalization method. Experiment results reveal that HRCSS achieves a significant improvement in data rate over existing methods: it delivers 500 bps data rate with a BER of 0.24 percent at 10 m, and achieves 125 bps with zero BER at 20 m. Meanwhile, HRCSS can work adaptively under dynamic channel conditions while still retaining a BER below 3 percent.

The emerging large-scale low earth orbit (LEO) broadband satellite networks manifest great potentials in distributing videos across the globe via efficient multicast techniques. However, existing work only studied IP multicast (IPMC) for LEO constellations, which suffers from limited scalability and tree performance. In this paper, we employ the promising software defined multicast (SDM) techniques in large-scale LEO constellations to empower satellite-based Internet video distribution. We present a multi-layer rectilinear Steiner tree (ML-RST) construction algorithm for multicast routing in large-scale LEO constellations. We extend the spanning graph and edge substitution to three-dimensional (3D) scenes. Based on multi-layer spanning graphs and multi-layer edge substitution approaches, we manage to efficiently construct ML-RSTs with${O}$(${n}$log${n}$) complexity. Experimental results show that our approach can achieve an average 10% improvement in bandwidth saving compared with existing algorithms.

Vital signs are crucial indicators for human health, and researchers are studying contact-free alternatives to existing wearable vital signs sensors. Unfortunately, most of these designs demand a subject human body to be relatively static, rendering them very inconvenient to adopt in practice where body movements occur frequently. In particular, radio-frequency (RF) based contact-free sensing can be severely affected by body movements that overwhelm vital signs. To this end, we introduce MoVi-Fi as a motion-robust vital signs monitoring system, capable of recovering fine-grained vital signs waveform in a contact-free manner. Being a pure software system, MoVi-Fi can be built on top of virtually any commercial-grade radars. What inspires our design is that RF reflections caused by vital signs, albeit weak, do not totally disappear but are composited with other motion-incurred reflections in a nonlinear manner. As nonlinear blind source separation is inherently hard, MoVi-Fi innovatively employs deep contrastive learning to tackle the problem; this self-supervised method requires no ground truth in training, and it exploits contrastive signal features to distinguish vital signs from body movements. Our experiments with 12 subjects and 80hour data demonstrate that MoVi-Fi accurately recovers vital signs waveform under severe body movements.

Crucial for healthcare and biomedical applications, respiration monitoring often employs wearable sensors in practice, causing inconvenience due to their direct contact with human bodies. Therefore, researchers have been constantly searching for contact-free alternatives. Nonetheless, existing contact-free designs mostly require human subjects to remain static, largely confining their adoptions in everyday environments where body movements are inevitable. Fortunately, radio-frequency (RF) enabled contact-free sensing, though suffering motion interference inseparable by conventional filtering, may offer a potential to distill respiratory waveform with the help of deep learning. To realize this potential, we introduce MoRe-Fi to conduct fine-grained respiration monitoring under body movements. MoRe-Fi leverages an IR-UWB radar to achieve contact-free sensing, and it fully exploits the complex radar signal for data augmentation. The core of MoRe-Fi is a novel variational encoder-decoder network; it aims to single out the respiratory waveforms that are modulated by body movements in a non-linear manner. Our experiments with 12 subjects and 66-hour data demonstrate that MoRe-Fi accurately recovers respiratory waveform despite the interference caused by body movements. We also discuss potential applications of MoRe-Fi for pulmonary disease diagnoses.

Fitness games recently attract much attention these years due to its combination of playability and athleticism. However, most fitness games are entertainment for a single person, with only a few deliver distinctive experiences for multiplayers. Enabling interaction between multiple players would be more enjoyable due to exciting cooperation among players. Considering a Big Stomach Challenge for two players, a certain amount of food can be only eaten when a mouth size, represented by the distance between players is reached collaboratively. Similarly, a certain type of food can only be picked up when the food grabbing speed, denoted by the approaching speed between players, is fast enough. Such games require accurate ranging and speed estimation in a relatively long distance (1-15 m) to deliver a good gaming experience. However, existing ranging schemes cannot meet the above requirements. They either cannot work under Doppler channels or have to strike a balance between accuracy and operational range, prohibiting a heuristic implementation for the above games. To this end, we design MotionBeep, a novel acoustic ranging scheme that achieves centimeter-level ranging and dm/s-level speed estimation accuracy under representative indoor and outdoor scenes within 15 m. In MotionBeep, we design a new working paradigm and incorporates a state-space model to maintain accurate ranging in both static and dynamic channels. We have implemented a system prototype and evaluate its performance in representative environments. Evaluation results demonstrate that MotionBeep achieves a median of centimeter accuracy with up to 15 m even under Doppler effect.

Temperature is an important data source for weather forecasting, agriculture irrigation, anomaly detection, etc. While temperature measurement can be achieved via low-cost yet standalone hardware with reasonable accuracy, integrating thermal sensing into ubiquitous computing devices is highly non-trivial due to the design requirement for specific heat isolation and proper device layout. In this paper, we present the first integrated thermometer using commercial-off-the-shelf acoustic-enabled devices. Our software sonic thermometer (SST) utilizes on-board dual microphones on commodity mobile devices to estimate sound speed, which has a known relation with temperature. To precisely measure temperature via sound speed, we propose a chirp mixing approach to circumvent low sampling rates on commodity hardware and design a pipeline of signal processing blocks to handle channel distortions. SST, for the first time, empowers ubiquitous computing devices with thermal sensing capability. It is portable and cost-effective, making it competitive with current thermometers using dedicated hardware. SST is potential to facilitate many interesting applications such as large-scale distributed thermal sensing, yielding high temporal/spatial resolutions with unimaginable low costs. We implement SST on a commodity platform and results show that SST achieves a median accuracy of${0.5^\circ \mathrm{C}}$even at varying humidity levels.

Though measuring ambient temperature is often deemed as an easy job, collecting large-scale temperature readings in real-time is still a formidable task. The recent boom of network-ready (mobile) devices and the subsequent mobile crowdsourcing applications do offer an opportunity to accomplish this task, yet equipping commodity devices with ambient temperature sensing capability is highly non-trivial and hence has never been achieved. In this paper, we propose Acoustic Thermometer (AcuTe) as the first ambient temperature sensor empowered by a single commodity smartphone. AcuTe utilizes on-board dual microphones to estimate air-borne sound propagation speed, thereby deriving ambient temperature. To accurately estimate sound propagation speed, we leverage the phase of chirp signals to circumvent the low sample rate on commodity hardware. In addition, we propose to use both structure-borne and air-borne propagations to address the multipath problem. Furthermore, to prevent disruptive audible transmissions, we convert chirp signals into white noises and propose a pipeline of signal processing algorithms to denoise received samples. As a mobile, economical, highly accurate sensor, AcuTe may potentially enable many relevant applications, in particular large-scale indoor/outdoor temperature monitoring in real-time. We conduct extensive experiments on AcuTe; the results demonstrate a robust performance, a median accuracy of 0.3° C even at a varying humidity level, and the ability to conduct distributed temperature sensing in real-time.

Recently, acoustic-based indoor localization has attracted much attention due to its affordable infrastructure costs and high localization accuracy. However, previous work is infeasible in mobile target tracking for its long latency in obtaining sufficient beacon messages. In addition, the performance can further deteriorate due to device diversity, varying channel gains, and background noises. To this end, we propose an asynchronous acoustic localization and tracking system (AALTS), which utilizes distributed acoustic anchor nodes to locate passive off-the-shelf mobile devices. In AALTS, we propose an orthogonal chirp spread spectrum (OCSS) modulation technique, which doubles the data rate and thus mitigates the latency. We design a more robust method to capture acoustic signals which embody timestamps for localization, accounting for device diversity, varying channel gains, and the multipath effect. Finally, we incorporate an acoustic Doppler speed estimation module with a path-based particle filter framework to accurately track the moving targets. We have evaluated AALTS in an indoor testbed of size 8×12 m2with commodity mobile phones and customized acoustic anchors. Our evaluation results demonstrate remarkable performance: AALTS achieves 90-percentile tracking errors of 0.49 m for mobile targets and a median of 0.12 m for stationary ones with only four anchor nodes.

Indoor localization has witnessed a rapid development in the past few decades. Tremendous solutions have been put forwarded in the literature and the localization accuracy has reach an unprecedent centimeter-level. Among the available approaches, acoustic-enabled solutions have attracted much attention. They customarily achieve decimeter-level localization accuracy with affordable infrastructure costs. However, there still exist several open issues for the acoustic-based approaches which prohibit their wide-scale adoptions. First, although extra infrastructures (i.e., beacons) are economical, deployment, and maintenance can incur excessive labor cost. Second, current approaches have much latency to obtain a location fix, making it infeasible for mobile target tracking. Third, the localization performance of current solutions degrades easily by the near-far problem, multipath effect, and device diversity. To address these issues, this paper presents an asynchronous acoustic-based localization system with participatory sensing. We leverage the collaborative efforts of the participatory users who are relatively stationary in indoor environments as virtual anchors (VAs) to eliminate the predeployment and post-maintenance costs incurred in traditional anchor-based solutions. To mitigate the latency to obtain a location fix, we design an orthogonal ranging mechanism to enable concurrent beacon message transmission, which is $2\boldsymbol \times $ faster than previous work in obtaining a location fix. Moreover, we propose a robust method to address the near-far problem and device diversity, and we conquer the multipath problem via a genetic algorithm-based approach. Our VA-based system is self-deployable, cost-effective, and robust to environmental dynamics. We have implemented and evaluated a system prototype, demonstrating a median accuracy of 0.98 m in typical indoor settings.

The enabling Internet-of-Things technology has inspired many innovative sensing mechanisms by repurposing the onboard sensors. Leveraging the built-in acoustic sensors for ranging is among one of the interesting applications. However, among the few studies on acoustic ranging, the one-way sensing method suffers from synchronization errors and requires cumbersome kernel modifications; the other two-way approaches overcome these shortcomings, but they are sensitive to system delays. In this case, this paper proposes a novel lightweight one-way sensing paradigm without the above drawbacks. The key insight of this paper is to perform ranging by estimating the propagation time of acoustic signals via linear frequency modulation signal mixing. Such a signal mix operation can translate range estimation into fine-grain frequency estimation, thereby enhancing ranging accuracy. In addition, our system can have multiple receivers co-exist and thus the measurement dimensions are boosted. We have implemented and evaluated our system prototype in real-world settings. The prototype demonstrated centimeter-level ranging performance.