Nowadays, the rapid development of self-driving technology and its fusion with the current vehicle electrification process has given rise to electric self-driving taxis (es-taxis). Foreseeably, es-taxis will become a major force that serves the massive urban mobility demands not far into the future. Though promising, it is still a fundamental unsolved problem of effectively deciding when and where a city-scale fleet of es-taxis should be charged, so that enough es-taxis will be available whenever and wherever ride requests are submitted. Furthermore, charging decisions are far from isolated, but tightly coupled with the order dispatch process that matches orders with es-taxis. Therefore, in this paper, we investigate the problem of joint order dispatch and charging in es-taxi systems, with the objective of maximizing the ride-hailing platform’s long-term cumulative profit. Technically, such problem is challenging in a myriad of aspects, such as long-term profit maximization, partial statistical information on future orders, etc. We address the various arising challenges by meticulously integrating a series of methods, including distributionally robust optimization, primal-dual transformation, and second order conic programming to yield far-sighted decisions. Finally, we validate the effectiveness of our proposed methods though extensive experiments based on two large-scale real-world online ride-hailing order datasets.

Vehicular urban sensing (VUS), which uses sensors mounted on crowdsourced vehicles or on-board drivers' smartphones, has become a promising paradigm for monitoring critical urban metrics. Due to various hardware and software constraints difficult for private vehicles to satisfy, for-hire vehicles (FHVs) are usually the major forces for VUS systems. However, FHVs alone are far from enough for fine-grained spatio-temporal sensing coverage, because of their severe distribution biases. To address this issue, we propose to use a hybrid approach, where a centralized platform not only leverages FHVs to conduct sensing tasks during their daily movements of serving passenger orders, but also controls multiple dedicated sensing vehicles (DSVs) to bridge FHVs' coverage gaps. Specifically, we aim to achieve fine-grained spatio-temporal sensing coverage at the minimum long-term operational cost by systematically optimizing the repositioning policy for DSVs. Technically, we formulate the problem as a stochastic dynamic program, and solve various challenges, including long-term cost minimization, stochastic demand with partial statistical knowledge, and computational intractability, by integrating distributionally robust optimization, primal-dual transformation, and second order conic programming methods. We validate the effectiveness of our methods using a real-world dataset from Shenzhen, China, containing 726,000 trajectories of 3848 taxis spanning overall 1 month in 2017.

The paper presents a real-time computing framework for intelligent real-time edge services, on behalf of local embedded devices that are themselves unable to support extensive computations. The work contributes to a new direction in realtime computing that develops scheduling algorithms for machine intelligence tasks that enable anytime prediction. We show that deep neural network workflows can be cast as imprecise computations, each with a mandatory part and (several) optional parts whose execution utility depends on input data. With our design, deep neural networks can be preempted before their completion and support anytime inference. The goal of the realtime scheduler is to maximize the average accuracy of deep neural network outputs while meeting task deadlines, thanks to opportunistic shedding of the least necessary optional parts. The work is motivated by the proliferation of increasingly ubiquitous but resource-constrained embedded devices (for applications ranging from autonomous cars to the Internet of Things) and the desire to develop services that endow them with intelligence. Experiments on recent GPU hardware and a state of the art deep neural network for machine vision illustrate that our scheme can increase the overall accuracy by 10% ~ 20% while incurring (nearly) no deadline misses.

This paper presents realistic traffic simulations in four representative regions in Chicago, using real map data and historical traffic statistics, to estimate the amount of fuel that can be saved by two types of systems, namely, a Green Light Optimal Speed Advisory (GLOSA) system and an Eco-Routing system. In particular, two previous systems called GreenDrive and GreenRoute are selected to estimate how much fuel they can save in a year, assuming they enjoy the same popularity as Google Maps. Evaluating intelligent transportation systems in simulation has attracted significant research efforts as large scale real-world experiments are often too expensive to carry out. However, simulation-based evaluations pose serious questions on how real the simulated environments are. In this paper, we resort to several data sources from the city of Chicago to quantify the approximation in simulated traffic, so as to convincingly derive the amount of fuel savings on a larger scale. Specifically, we create SUMO simulations of four real regions of Chicago, and utilize traffic counts data, road speed data, and taxi trips data to validate each simulation scenario. In the end, we show that by using our previously proposed systems, the estimated fuel saved in a year can be 17.6 million gallons for the entire Chicago area.

Large volumes of event data are becoming increasingly available on online social networks. These events are usually causally dependent to each other, reflecting the interactions and collaborations among different parties. Learning and interpreting the temporal patterns and dynamics within these event streams plays an important role in many practical applications, such as trend prediction and anomaly detection. Since causal dependencies can be reflected in both event time (i.e., when) and event content (i.e., who and what), we thus develop a user community based generative model, called latent Hawkes process (LHP), taking into account both-side information to illustrate the generation of such inter-dependent event streams on GitHub repositories, where each attribute is assumed to be generated by interplays between correlated latent communities. Through learning of our model, two functionalities are fulfilled concurrently: event clustering (i.e., community discovery) and temporal dependency learning among these clusters (i.e., dependency profiling). To do so, we design an EM-based framework integrating sequential Monte Carlo sampling to estimate model parameters in an end-to-end manner. Through experiments on practical GitHub event data, we validate the effectiveness of LHP in extracting user community structures and learning their correlated temporal dynamics. Such knowledge further enables us to gain new insights into the development status of software, such as the project persistence and anomaly detection.

The paper discusses an emerging suite of machine intelligence services that are of increasing importance in the highly instrumented world of the Internet of Things (IoT). The suite, called Eugene, would offer a form of intelligent behavior (based on deep neural networks) to otherwise simple embedded devices; the clients of the service. These devices would benefit from service resources to learn from data and to perform intelligent inference, classification, prediction, and estimation tasks that they are too limited to carry out on their own. The paper discusses the taxonomy of such services and the state of implementation, as well as the various challenges entailed, including scheduling, caching (of intelligent functions), and cooperative learning.

Deep neural networks are becoming increasingly popular in Internet of Things (IoT) applications. Their capabilities of fusing multiple sensor inputs and extracting temporal relationships can enhance intelligence in a wide range of applications. However, one key problem is the missing of adaptation to heterogeneous on-device sensors. These low-end sensors on IoT devices possess different accuracies, granularities, and amounts of information, whose sensing qualities are heterogeneous and vary over time. The existing deep learning frameworks for IoT applications usually treat every sensor input equally over time or increase model capacity in an ad-hoc manner, lacking the ability to identify and exploit the sensor heterogeneities. In this work, we propose SADeepSense, a deep learning framework that can automatically balance the contributions of multiple sensor inputs over time by exploiting their sensing qualities. SADeepSense makes two key contributions. First, SADeepSense employs the self-attention mechanism to learn the correlations among different sensors over time with no additional supervision. The correlations are then applied to infer the sensing qualities and to reassign model concentrations in multiple sensors over time. Second, instead of directly learning the sensing qualities and contributions, SADeepSense generates the residual concentrations that are deviated from the equal contributions, which helps to stabilize the training process. We demonstrate the effectiveness of SADeepSense with two representative IoT sensing tasks: heterogeneous human activity recognition with motion sensors and gesture recognition with the wireless signal. SADeepSense consistently outperforms the state-of-the-art methods by a clear margin. In addition, we show that SADeepSense only imposes little additional resource-consumption burden on embedded devices compared to the corresponding state-of-the-art framework.

Recent advances in deep learning motivate the use of deep neural networks in Internet-of-Things (IoT) applications. These networks are modelled after signal processing in the human brain, thereby leading to significant advantages at perceptual tasks such as vision and speech recognition. IoT applications, however, often measure physical phenomena, where the underlying physics (such as inertia, wireless signal propagation, or the natural frequency of oscillation) are fundamentally a function of signal frequencies, offering better features in the frequency domain. This observation leads to a fundamental question: For IoT applications, can one develop a new brand of neural network structures that synthesize features inspired not only by the biology of human perception but also by the fundamental nature of physics? Hence, in this paper, instead of using conventional building blocks (e.g., convolutional and recurrent layers), we propose a new foundational neural network building block, the Short-Time Fourier Neural Network (STFNet). It integrates a widely-used time-frequency analysis method, the Short-Time Fourier Transform, into data processing to learn features directly in the frequency domain, where the physics of underlying phenomena leave better footprints. STFNets bring additional flexibility to time-frequency analysis by offering novel nonlinear learnable operations that are spectral-compatible. Moreover, STFNets show that transforming signals to a domain that is more connected to the underlying physics greatly simplifies the learning process. We demonstrate the effectiveness of STFNets with extensive experiments on a wide range of sensing inputs, including motion sensors, WiFi, ultrasound, and visible light. STFNets significantly outperform the state-of-the-art deep learning models in all experiments. A STFNet, therefore, demonstrates superior capability as the fundamental building block of deep neural networks for IoT applications for various sensor inputs 1.

Recent advances in deep-learning-based applications have attracted a growing attention from the IoT community. These highly capable learning models have shown significant improvements in expected accuracy of various sensory inference tasks. One important and yet overlooked direction remains to provide uncertainty estimates in deep learning outputs. Since robustness and reliability of sensory inference results are critical to IoT systems, uncertainty estimates are indispensable for IoT applications. To address this challenge, we develop ApDeepSense, an effective and efficient deep learning uncertainty estimation method for resource-constrained IoT devices. ApDeepSense leverages an implicit Bayesian approximation that links neural networks to deep Gaussian processes, allowing output uncertainty to be quantified. Our approach is shown to significantly reduce the execution time and energy consumption of uncertainty estimation thanks to a novel layer-wise approximation that replaces the traditional computationally intensive sampling-based uncertainty estimation methods. ApDeepSense is designed for neural net-works trained using dropout; one of the most widely used regularization methods in deep learning. No additional training is needed for uncertainty estimation purposes. We evaluate ApDeepSense using four IoT applications on Intel Edison devices. Results show that ApDeepSense can reduce around 88.9% of the execution time and 90.0% of the energy consumption, while producing more accurate uncertainty estimates compared with state-of-the-art methods.

This paper develops a constrained expectation maximization algorithm (CEM) that improves the accuracy of truth estimation in unguided social sensing applications. Unguided social sensing refers to the act of leveraging naturally occurring observations on social media as “sensor measurements”, when the sources post at will and not in response to specific sensing campaigns or surveys. A key challenge in social sensing, in general, lies in estimating the veracity of reported observations, when the sources reporting these observations are of unknown reliability and their observations themselves cannot be readily verified. This problem is known as fact-finding. Unsupervised solutions have been proposed to the fact-finding problem that explore notions of internal data consistency in order to estimate observation veracity. This paper observes that unguided social sensing gives rise to a new (and very simple) constraint that dramatically reduces the space of feasible fact-finding solutions, hence significantly improving the quality of fact-finding results. The constraint relies on a simple approximate test of source independence, applicable to unguided sensing, and incorporates information about the number of independent sources of an observation to constrain the posterior estimate of its probability of correctness. Two different approaches are developed to test the independence of sources for purposes of applying this constraint, leading to two flavors of the CEM algorithm, we call CEM and CEM-Jaccard. We show using both simulation and real data sets collected from Twitter that by forcing the algorithm to converge to a solution in which the constraint is satisfied, the quality of solutions is significantly improved.

Deep neural networks show great potential as solutions to many sensing application problems, but their excessive resource demand slows down execution time, pausing a serious impediment to deployment on low-end devices. To address this challenge, recent literature focused on compressing neural network size to improve performance. We show that changing neural network size does not proportionally affect performance attributes of interest, such as execution time. Rather, extreme run-time nonlinearities exist over the network configuration space. Hence, we propose a novel framework, called FastDeepIoT, that uncovers the non-linear relation between neural network structure and execution time, then exploits that understanding to find network configurations that significantly improve the trade-off between execution time and accuracy on mobile and embedded devices. FastDeepIoT makes two key contributions. First, FastDeepIoT automatically learns an accurate and highly interpretable execution time model for deep neural networks on the target device. This is done without prior knowledge of either the hardware specifications or the detailed implementation of the used deep learning library. Second, FastDeepIoT informs a compression algorithm how to minimize execution time on the profiled device without impacting accuracy. We evaluate FastDeepIoT using three different sensing-related tasks on two mobile devices: Nexus 5 and Galaxy Nexus. FastDeepIoT further reduces the neural network execution time by 48% to 78% and energy consumption by 37% to 69% compared with the state-of-the-art compression algorithms.

This paper presents improved results on classifying electroencephalography (EEG) recordings using deep learning. The task is to classify movements that the subject is thinking about (motor imagery), using only the recorded electrical activities on the scalp. The challenges are: poor signal-to-noise ratio; interference from numerous sources such as electrical line noise, muscle activity, and eye movements; considerable variability between individuals and even recording sessions. Traditional signal processing techniques such as frequency band analysis, common spatial pattern (CSP) algorithm or independent component analysis (ICA) fall short due to their limited capacity. Thanks to the rise of big data in healthcare, medical recordings now come in abundance. Therefore deep learning which relies on large amounts of training data is becoming the new cutting edge tool. We present a significant improvement of classification accuracy on the Brain-Computer Interfaces Competition IV dataset (2a), and compare the results of various state of the art neural network structures.

This paper introduces a novel paradigm for resource management in distributed systems, called decision-driven execution. The paradigm is appropriate for mission-driven systems, where the goal is to enable faster, leaner, and more effective decision making. All resource consumption, in this paradigm, is tied to the needs of making decisions on alternative courses of action. A point of departure from traditional architectures lies in interfaces that allow applications to specify their underlying decision logic. This specification, in turn, allows the system to reason about most effective means to meet information needs of decisions, resulting in simultaneous optimization of decision accuracy, cost, and speed. The paper discusses the overall vision of decision-driven execution, outlining preliminary work and novel challenges.

Emerging distributed in-memory computing frameworks, such as Apache Spark, can process a huge amount of cached data within seconds. This remarkably high efficiency requires the system to well balance data across tasks and ensure data locality. However, it is challenging to satisfy these requirements for applications that operate on a collection of dynamically loaded and evicted datasets. The dynamics may lead to time-varying data volume and distribution, which would frequently invoke expensive data re-partition and transfer operations, resulting in high overhead and large delay. To address this problem, we present Stark, a system specifically designed for optimizing in-memory computing on dynamic dataset collections. Stark enforces data locality for transformations spanning multiple datasets (e.g., join and cogroup) to avoid unnecessary data replications and shuffles. Moreover, to accommodate fluctuating data volume and skeweddata distribution, Stark delivers elasticity into partitions to balance task execution time andreduce job makespan. Finally, Stark achieves bounded failure recovery latency byoptimizing the data checkpointing strategy. Evaluations on a 50-server cluster show that Stark reduces the job makespan by 4X and improves system throughput by 6X compared to Spark.

This paper addresses the problem of choosing the right sources to solicit data from in sensing applications involving broadcast channels, such as those crowdsensing applications where sources share their observations on social media. The goal is to select sources such that expected fusion error is minimized. We assume that soliciting data from a source incurs a cost and that the cost budget is limited. Contrary to other formulations of this problem, we focus on the case where some sources influence others. Hence, asking a source to make a claim affects the behavior of other sources as well, according to an influence model. The paper makes two contributions. First, we develop an analytic model for estimating expected fusion error, given a particular influence graph and solution to the source selection problem. Second, we use that model to search for a solution that minimizes expected fusion error, formulating it as a zero-one integer non-linear programming (INLP) problem. To scale the approach, the paper further proposes a novel reliability-based pruning heuristic (RPH) and a similarity-based lossy estimation (SLE) algorithm that significantly reduce the complexity of the INLP algorithm at the cost of a modest approximation. The analytically computed expected fusion error is validated using both simulations and real-world data from Twitter, demonstrating a good match between analytic predictions and empirical measurements. It is also shown that our method outperforms baselines in terms of resulting fusion error.

Recent advances in deep learning motivate the use of deep neutral networks in sensing applications, but their excessive resource needs on constrained embedded devices remain an important impediment. A recently explored solution space lies in compressing (approximating or simplifying) deep neural networks in some manner before use on the device. We propose a new compression solution, called DeepIoT, that makes two key contributions in that space. First, unlike current solutions geared for compressing specific types of neural networks, DeepIoT presents a unified approach that compresses all commonly used deep learning structures for sensing applications, including fully-connected, convolutional, and recurrent neural networks, as well as their combinations. Second, unlike solutions that either sparsify weight matrices or assume linear structure within weight matrices, DeepIoT compresses neural network structures into smaller dense matrices by finding the minimum number of non-redundant hidden elements, such as filters and dimensions required by each layer, while keeping the performance of sensing applications the same. Importantly, it does so using an approach that obtains a global view of parameter redundancies, which is shown to produce superior compression. The compressed model generated by DeepIoT can directly use existing deep learning libraries that run on embedded and mobile systems without further modifications. We conduct experiments with five different sensing-related tasks on Intel Edison devices. DeepIoT outperforms all compared baseline algorithms with respect to execution time and energy consumption by a significant margin. It reduces the size of deep neural networks by 90% to 98.9%. It is thus able to shorten execution time by 71.4% to 94.5%, and decrease energy consumption by 72.2% to 95.7%. These improvements are achieved without loss of accuracy. The results underscore the potential of DeepIoT for advancing the exploitation of deep neural networks on resource-constrained embedded devices.

Mobile sensing and computing applications usually require time-series inputs from sensors, such as accelerometers, gyroscopes, and magnetometers. Some applications, such as tracking, can use sensed acceleration and rate of rotation to calculate displacement based on physical system models. Other applications, such as activity recognition, extract manually designed features from sensor inputs for classification. Such applications face two challenges. On one hand, on-device sensor measurements are noisy. For many mobile applications, it is hard to find a distribution that exactly describes the noise in practice. Unfortunately, calculating target quantities based on physical system and noise models is only as accurate as the noise assumptions. Similarly, in classification applications, although manually designed features have proven to be effective, it is not always straightforward to find the most robust features to accommodate diverse sensor noise patterns and heterogeneous user behaviors. To this end, we propose DeepSense, a deep learning framework that directly addresses the aforementioned noise and feature customization challenges in a unified manner. DeepSense integrates convolutional and recurrent neural networks to exploit local interactions among similar mobile sensors, merge local interactions of different sensory modalities into global interactions, and extract temporal relationships to model signal dynamics. DeepSense thus provides a general signal estimation and classification framework that accommodates a wide range of applications. We demonstrate the effectiveness of DeepSense using three representative and challenging tasks: car tracking with motion sensors, heterogeneous human activity recognition, and user identification with biometric motion analysis. DeepSense significantly outperforms the state-of-the-art methods for all three tasks. In addition, we show that DeepSense is feasible to implement on smartphones and embedded devices thanks to its moderate energy consumption and low latency.

This paper develops a simplified dependency model for sources on social networks that is shown to improve the quality of fact-finding -- assessing veracity of observations shared on social media. Recent literature developed a mathematical approach for exploiting social networks, such as Twitter, as noisy sensor networks that report observations on the state of the physical world. It was shown that the quality of state estimation from such noisy data, known as fact-finding, was a function of assumptions made regarding the independence of sources or lack thereof. When sources propagate information they hear from others (without verification), correlated errors may arise that degrade fact-finding performance. This work advances the state of the art by developing a simplified model of dependencies between sources and designing an improved dependency-aware estimator to assess veracity of observations, taking into account the observed dependency structure. A fundamental error bound is derived for this estimator to understand the gap in its performance from optimal. It is shown that the new estimator outperforms state of the art fact-finders and, in some cases, yields an accuracy close to the fundamental error bound.

The paper develops a recursive state estimator for social network data streams that allows exploitation of social networks, such as Twitter, as sensor networks to reliably observe physical events. Recent literature suggested using social networks as sensor networks leveraging the fact that much of the information upload on the former constitutes acts of sensing. A significant challenge identified in that context was that source reliability is often unknown, leading to uncertainty regarding the veracity of reported observations. Multiple truth finding systems were developed to solve this problem, generally geared towards batch analysis of offline datasets. This work complements the present batch approaches by developing an online recursive state estimator that recovers ground truth from streaming data. In this paper, we model physical world state by a set of binary signals (propositions, called assertions, about world state) and the social network as a noisy medium, where distortion, fabrication, omissions, and duplication are introduced. Our recursive state estimator is designed to recover the original binary signal (the true propositions) from the received noisy signal, essentially decoding the unreliable social network output to obtain the best estimate of ground truth in the physical world. Results show that the estimator is both effective and efficient at recovering the original signal with a high degree of accuracy. The estimator gives rise to a novel situation awareness tool that can be used for reliably following unfolding events in real time, using dynamically arriving social network data.

This paper presents a comprehensive evaluation of an ultra-low power cluster, built upon the Intel Edison based micro servers. The improved performance and high energy efficiency of micro servers have driven both academia and industry to explore the possibility of replacing conventional brawny servers with a larger swarm of embedded micro servers. Existing attempts mostly focus on mobile-class micro servers, whose capacities are similar to mobile phones. We, on the other hand, target on sensor-class micro servers, which are originally intended for uses in wearable technologies, sensor networks, and Internet-of-Things. Although sensor-class micro servers have much less capacity, they are touted for minimal power consumption (< 1 Watt), which opens new possibilities of achieving higher energy efficiency in datacenter workloads. Our systematic evaluation of the Edison cluster and comparisons to conventional brawny clusters involve careful workload choosing and laborious parameter tuning, which ensures maximum server utilization and thus fair comparisons. Results show that the Edison cluster achieves up to 3.5x improvement on work-done-per-joule for web service applications and data-intensive MapReduce jobs. In terms of scalability, the Edison cluster scales linearly on the throughput of web service workloads, and also shows satisfactory scalability for MapReduce workloads despite coordination overhead.

The paper describes a novel algorithm for timely sensor data retrieval in resource-poor environments under freshness constraints. Consider a civil unrest, national security, or disaster management scenario, where a dynamic situation evolves and a decision-maker must decide on a course of action in view of latest data. Since the situation changes, so is the best course of action. The scenario offers two interesting constraints. First, one should be able to successfully compute the course of action within some appropriate time window, which we call the decision deadline. Second, at the time the course of action is computed, the data it is based on must be fresh (i.e., within some corresponding validity interval). We call it the freshness constraint. These constraints create an interesting novel problem of timely data retrieval. We address this problem in resource-scarce environments, where network resource limitations require that data objects (e.g., pictures and other sensor measurements pertinent to the decision) generally remain at the sources. Hence, one must decide on (i) which objects to retrieve and (ii) in what order, such that the cost of deciding on a valid course of action is minimized while meeting data freshness and decision deadline constraints. Such an algorithm is reported in this paper. The algorithm is shown in simulation to reduce the cost of data retrieval compared to a host of baselines that consider time or resource constraints. It is applied in the context of minimizing cost of finding unobstructed routes between specified locations in a disaster zone by retrieving data on the health of individual route segments.