Abstract The identification of key flows, as one of the most important traffic measurement tasks in high-speed networks, has lots of practical applications, including network resource optimization and network attack detection. However, the existing works define the key flows only according to the flow size or the persistence (i.e. time dimension), all of which are one-sided definitions. To bridge the gap, we propose a new metric (named $H$-value) to identify key flows in high-speed networks, in which the flow $H$-value metric considers the joint distribution of flow size and time relationships. Specifically, the $H$-value of one flow means the flow size of this flow in at least $H$ measurement periods is not less than $H$. Based on this new metric, we redefine the key flows as the flows with large $H$-values, called $H^{2}$-flow. Efficiently and accurately identifying $H^{2}$-flows in high-speed networks faces significant challenges due to limited memory space, uneven distribution of flow $H$-values, and real-time requirements. To this end, we propose a new sketch structure called H$^{2}$Sketch, which consists of two main modules. Extensive experimental results based on real datasets show that H$^{2}$Sketch outperforms all the compared solutions in all evaluation metrics, such as ARE, F1 score, and throughput.

Key-value data streams are widely spread in modern information systems. This paper delves into the inner features of individual keys and introduces a new measurement task called Core Composition Estimation for Frequent Keys (CCEFK). CCEFK aims to identify the most significant values associated with an item's key, which can be fully applied to a wide range of real-world scenarios. To address this quite challenging, multidimensional CCEFK mission, we propose PieSketch, a novel sketch-based algorithm that supports three types of queries related to CCEFK. PieSketch employs a three-level data structure and a two-staged insertion algorithm to process the keys and values of data streams separately and sequentially, achieving fine-grained data summarization for both. Through some rigorous theoretical analysis, we prove that PieSketch can achieve a good performance guarantee with low time and space complexity. We further present three optimizations to enhance PieSketch comprehensively: Sector Morphing addresses the diversity in value distribution among different keys with a dynamically adjusting strategy, significantly improving memory efficiency; Early Filtration ensures PieSketch's stability in extreme conditions; SIMD Acceleration speeds up PieSketch for data processing. We finally conducted extensive experiments on four real-world datasets to evaluate PieSketch's excellent performance. The results show that PieSketch significantly outperforms state-of-the-art techniques, achieving$23.67\times$,$88.41\times$, and$15.80\times$better accuracy on three types of queries, respectively, and demonstrating 1.84 times higher insertion throughput on average. All our codes are publicly available on GitHubhttps://github.com/NeoAnderson-20/PieSketch-source.

Identifying the hierarchical heavy hitters (HHHs), i.e., the frequent aggregated flows based on common IP prefixes, is a vital task in network traffic measurement and security. Existing methods typically employ dynamic trie structures to track numerous prefixes or utilize multiple separate sketch instances, one for each hierarchical level, to capture HHHs across different levels, while both approaches suffer from low memory efficiency and limited compatibility with programmable switches. In this paper, we introduce two novel HHH detection solutions, respectively, Hierarchical Heavy Detector (HHD) and the Compressed Hierarchical Heavy Detector (CHHD), to achieve high memory efficiency and enhanced hardware compatibility. The key idea of HHD is to design a shared bucket array structure to identify and record HHHs from all hierarchical levels, which avoids the memory wastage of maintaining separate sketches to achieve high memory efficiency and allows feasible deployment of both byte-hierarchy and bit-hierarchy HHH detection on programmable switches using minimal processing stage resources. Additionally, HHD utilizes a sampling-based update strategy to effectively balance packet processing speed and detection accuracy. Furthermore, we present the CHHD, which enhances HHH detection in bit hierarchies through a more compact cell structure, which allows for compressing several ancestor and descendant prefixes within a single cell, further boosting memory efficiency and accuracy. We have implemented HHD and CHHD on a P4-based programmable switch with limited switch resources. Experimental results based on real-world Internet traces demonstrate that HHD and CHHD outperform the state-of-the-art by achieving up to 56 percentage points higher detection precision and 2.6× higher throughput.

Federated learning (FL) is a distributed learning paradigm that enables large-scale IoT devices to collaboratively train a shared model while preserving the privacy of local data. To avoid the single-point-of-failure of the conventional parameter server architecture, the study concentrates on the decentralized FL (DFL) paradigm building on the device-to-device communication network. However, existing DFL frameworks encounter challenges related to resource limitations, privacy protection, and data heterogeneity. To overcome these challenges, the study proposes and implements DF$^{2}$-MPC in industrial IoT, an efficient DFL framework with personalized model pruning and adaptive communication. Specifically, a personalized pruning ratio determination approach is designed by exploiting the model pruning technique. This approach enables all devices to flexibly determine pruning ratios by themselves, thereby achieving both communication savings and privacy protection. Then, this study designs an adaptive neighbor selection scheme, which can enhance model performance and foster model consensus under resource constraints. In addition, the study theoretically proves the convergence performance of DF$^{2}$-MPC. Finally, extensive simulations on three real-world traces are conducted to corroborate the superiority of DF$^{2}$-MPC, demonstrating that the method can improve communication efficiency with satisfactory model accuracy and convergence performance.

Network traffic measurement is crucial for the effective management of data center networks. Collaborative measurement solutions distribute measurement tasks to switches based on flow-level or packet-level granularity to alleviate the measurement load on each switch. However, flow-level solutions often experience severe imbalances in measurement overhead between switches measuring large or small flows, and face scalability challenges due to the costly optimization of collaborative plans. Additionally, packet-level solutions do not adequately reduce hash collisions in sketches and fail to significantly enhance measurement accuracy. In this article, we present the Lightweight Two-level Collaborative Measurement (LTCM) that synergies flow-level and packet-level strategy to optimize measurement load balancing, reduce overall measurement overhead, and enhance measurement accuracy. We first design a Lightweight Flow-level Measurement (FCM) framework that balances the number of flows measured by each switch, incorporating a novel interval-matching technique that significantly lowers the computational costs of collaborative strategies. Based on FCM, LTCM implements our measurement load balancing strategy selector at ingress switches to detect flows whose number of packets entering the network exceeds a given threshold and evenly distribute their subsequent packets across all switches for measurement. To further improve measurement accuracy and speed, we design a two-layer collaborative sketch that reduces hash collisions between large and small flows. We implement LTCM on a Tofino-based programmable switch. Experimental results based on real Internet traces show that LTCM achieves highly efficient flow-level and packet-level measurement load balancing, improving accuracy by up to 96.6% and throughput by up to 112.79%. All related implementations are open-sourced. 1

Spread measurement is an essential problem in high-speed networks with broad applications, such as anomaly detection and network telemetry. Network administrators typically need to concurrently monitor the spreads of different types of flows to detect various abnormal behaviors. Although many studies have designed memory-efficient structures, such as sketches, for a specific spread measurement task, they have to deploy multiple sketches to support multiple spread measurement tasks, resulting in significant memory and computational overhead. This paper proposes an efficient multi-task information compression method to simultaneously estimate differently defined flow spreads. We introduce multi-information sampling to capture multi-task spread information from each arriving packet by one pass and store it in off-chip memory, thereby conserving on-chip memory and computational resources. Additionally, we carefully designed a one-access multi-dimensional structure called Supercube to preserve as much spread information as possible while catching up with the line rate, thereby enhancing estimation accuracy. We implement our estimator in hardware using NetFPGA. Experiments based on real Internet traces show that our method reduces the ARE by 83.36% for spread estimation compared to rSkt (SOTA) with 300KB of on-chip memory and increases update throughput by 251.252-fold compared to Supersketch. All source codes are available athttps://github.com/Hanwen808/MIME.

Traffic measurement provides essential information for various network services. Burst is a common phenomenon in high-speed network streams, which manifests as a surge in the number of incoming packets in a flow. We propose a new definition named across-period burst, considering the change not in two adjacent time windows but in two groups of windows with time continuity. The across-period burst definition can better capture the continuous changes of flows in high-speed networks. To achieve real-time burst detection with high accuracy and low memory consumption, we propose a novel sketch named BurstDetector, which consists of two stages. Stage 1 excludes those flows that will not become burst flows, while Stage 2 accurately records the information of the potential burst flows and carries out across-period burst detections at the end of every time window. We further propose an optimization called Hierarchical Cell, which can improve the memory utilization of BurstDetector. In addition, we analyze the estimation accuracy and time complexity of BurstDetector. Extensive experiments based on real-world datasets show that our BurstDetector can achieve at least 2.8 times as much detection accuracy and processing throughput as some existing algorithms.

This paper studies a new but important pattern for items in data streams, called promising items. The promising items mean that the frequencies of an item in multiple continuous time windows show an upward trend overall, while a slight decrease in some of these windows is allowed. Many practical applications can benefit from the property of promising items, e.g., detecting potential hot events or news in social networks, preventing network congestion in communication channels, and monitoring latent attacks in computer networks. To accurately find promising items in data streams in real-time under limited memory space, we propose a novel structure named Scout Sketch, which consists of Filter and Finder. Filter is devised based on the Bloom filter to eliminate the ungratified items with less memory overload; Finder records some necessary information about the potential items and detects the promising items at the end of each time window, where we propose some tailor-made detection operations. We also analyze the theoretical performance of Scout Sketch. Finally, we conducted extensive experiments based on four real-world datasets. The experimental results show that the F1 Score and throughput of Scout Sketch are about 2.02 and 5.61 times that of the compared solutions, respectively.

Periodicity and fluctuation are two crucial characteristics of data streams. This paper investigates a novel data stream pattern called periodic spread changer (PSC flow for short), which refers to the heavy change in the spread of a flow occurring with fixed time intervals. Effectively identifying such flows is essential for many real-world applications, such as anomaly detection and network monitoring. To achieve precise real-time detection of these flows under limited memory resources, we propose a novel structure named PSC Sketch. PSC Sketch firstly performs the spread estimation by removing duplicate data items and filters out those non-potential flows with small spreads. During the measurement period, PSC Sketch detects the spread changers, calculates the time intervals between adjacent heavy changes, and reports the top-k periodic spread changers. Extensive experiments based on four real-world datasets demonstrate that, compared to competing algorithms, PSC Sketch achieves an average of 16.80 times lower average absolute error, 44.93% higher accuracy, and 1.83 times higher throughput.

Mobile crowdsensing (MC), an excellent solution to large-scale spatiotemporal data sensing problems, has recently received lots of attention from both industry and academia. In the MC system, any requester can acquire the sensing data for his points of interest (PoIs) by offering some payments to attract a group of mobile users capable of completing these PoI-related sensing tasks. However, the current MC work neglected three vital factors, more or less. First, they assume that these distributed users are mutually independent in MC, ignoring the social effects. Actually, the sensing data collected by one user may be corroborated by others’ sensing data, so-called information corroboration. Second, all rational and selfish users are inclined to gather to perform these tasks due to information corroboration. Meanwhile, they may be strategic about their participation levels to maximize profits. However, more similar sensing data will undoubtedly lower the information value, so any user has a tradeoff between gather and scatter. Third, although mobile users can obtain some payments, privacy issues may still prevent them from participating in MC. In this article, we propose a secure blockchain-assisted socially-aware MC framework by adopting the smart contract technique of Ethereum. For this framework, we further devise a two-stage Stackelberg game model to assist the requester (i.e., the leader in the game) in properly pricing each PoI-related sensing task, so that mobile users (i.e., the followers in the game) can exactly select their tasks and determine their participation levels. To analyze the game equilibrium, we extend the traditional Hessian matrix method to a multidimension case involving the multiuser multitask hyperspace setting. We conduct extensive experiments to prove the equilibrium and effectiveness of the proposed solution. We also implement a prototype and deploy the smart contract to an official Ethereum test network to demonstrate the practicability of the proposed framework.

In recent years, Crowdsensing Data Trading (CDT) has emerged as a new data trading paradigm, where buyers crowdsource data collection tasks to a group of mobile users with sensing devices (a.k.a., sellers) who sell the collected data to them, through a platform as the broker for a long-term data trading. One of the most critical issues in CDT is ensuring the stability of the matching between buyers and sellers in the data trading market. In this paper, we focus on privacy protection and the stability problems in the CDT market with unknown preference sequences of buyers. The goal is to protect sellers' data qualities and ensure the CDT market's stability while maximizing the cumulative data quality for each task. We model this problem as a differentially private multi-player multi-armed competing bandit problem and propose a novel metric of the approximate stability, called$\delta$-stability. We propose a privacy-preserving stable CDT mechanism called DPS-CB to solve this problem in the centralized setting, which is based on stable matching theory, and competing bandit strategy. Moreover, we extend it into decentralized setting in order to avoid the competitive matching conflicts caused in this setting and propose a Conflicts-avoiding DPS-CB mechanism, called CDPS-CB, by using Bernoulli probability and selecting feasible sets of sellers. In addition, we prove the security and stability of the CDT market under privacy concerns and analyze the regret performance of DPS-CB and CDPS-CB mechanisms, respectively. Finally, the significant performance of these two mechanisms is demonstrated through extensive simulations on a real-world dataset.

In this paper, we focus on the privacy preserving mechanism design for crowdsourced Federated Learning (FL), where a requester can outsource its model training task to some workers via an FL platform. A potential way to preserve the privacy of workers' local data is to leverage Differential Privacy (DP) mechanisms on local models. However, most of these studies cannot allow workers to dominate their own privacy protection levels by themselves. Thus, we propose a Personalized Privacy Preserving Mechanism, called P3M, to satisfy the heterogeneous privacy needs of workers, which consists of two parts. The first part includes a personalized privacy budget determination problem. We model it as a two-stage Stackelberg game, derive the personalized privacy budget for each worker and the optimal payment for the requester, and prove that they form a unique Stackelberg equilibrium. Second, we design a dynamic perturbation scheme to perturb model parameters. Through the theoretical analysis, we prove that P3M satisfies the desired DP property, and derive the bounds of the variance of average perturbed parameters and the convergence upper bound. This demonstrates that the global model accuracy can be controllable and P3M is endowed with the satisfactory convergence performance. In addition, we extend our problem to the scenario where the total privacy budget of all workers is limited, so as to prevent some workers from setting exorbitant privacy budgets. Under the privacy constraint, we re-determine the personalized privacy budget for each worker. Finally, exhaustive simulations of P3M are conducted based on real-world datasets, and the experimental results corroborate its effectiveness and practicability.

Data stream processing holds great potential value in lots of practical application scenarios. This paper studies two new but important patterns for items in data streams, called promising and damping items. The promising items mean that the frequencies of an item in multiple continuous time windows show an upward trend overall, while a slight decrease in some of these windows is allowed. In contrast to promising items exhibiting an increasing trend, the definition of damping items indicates a decreasing trend. Many applications can benefit from the property of promising or damping items, e.g., monitoring latent attacks in computer networks, pre-adjusting bandwidth allocation in communication channels, detecting potential hot events/news, or finding topics that gradually lose momentum in social networks. We first introduce how to accurately find promising items in data streams in real-time under limited memory space. To this end, we propose a novel structure named Scout Sketch, which consists of Filter and Finder. Filter is devised based on the Bloom filter to eliminate the ungratified items with less memory overload; Finder records some necessary information about the potential items and detects the promising items at the end of each time window, where we propose some tailor-made detection operations. We then enhance Scout Sketch (called Scout Sketch+) to adaptively detect both types of promising and damping items simultaneously. Finally, we conducted extensive experiments on four real-world datasets, which show that the F1 Score and throughput of Scout Sketch(+) are about 2.02 and 5.61 times that of the compared solutions. All source codes are available at Github (https://github.com/Aoohhh/ScoutSketch).

Cardinality estimation is a fundamental problem with diverse practical applications. HyperLogLog (HLL) has become a standard in practice because it offers good memory efficiency, constant update time, and mergeability. Some recent work achieved better memory efficiency, but typically at the cost of impractical update time or losing mergeability, making them incompatible with applications like network-wide traffic measurement. This work presents SpikeSketch, a better cardinality estimator that reduces memory usage of HLL by 37% without sacrificing other crucial metrics. We adopt a bucket-based data structure to promise constant update time, design a smoothed log4ranking and a spike coding scheme to compress cardinality observables into buckets, and propose a lightweight mergeable lossy compression to balance memory usage, information loss, and mergeability. Then we derive an unbiased estimator for recovering cardinality from the lossy-compressed sketch. Theoretical and empirical results show that SpikeSketch can work as a drop-in replacement for HLL because it achieves a near-optimal MVP (memory-variance-product) of 4.08 (37% smaller than HLL) with constant update time and mergeability. Its memory efficiency even defeats ACPC and HLLL, the state-of-the-art lossless-compressed sketches using linear-time compression to reduce memory usage.

Multi-Armed Bandit (MAB) that solves the sequential decision-making to the prior-unknown settings has been extensively studied and adopted in various applications such as online recommendation, transmission rate allocation, etc. Although some recent work has investigated the multi-agent MAB model, they supposed that agents share their bandit information based on social networks but neglected the incentives and arm-pulling budget for heterogeneous agents. In this paper, we propose a transaction-based multi-agent MAB framework, where agents can trade their bandit experience with each other to improve their total individual rewards. Agents not only face the dilemma between exploitation and exploration, but also decide to post a suitable price for their bandit experience. Meanwhile, as a buyer, the agent accepts another agent whose experience will help her the most, according to the posted price and her risk-tolerance level. The key challenge lies in that the arm-pulling and experience-trading decisions affect each other. To this end, we design the transaction-based upper confidence bound to estimate the prior-unknown rewards of arms, based on which the agents pull arms or trade their experience. We prove the regret bound of the proposed algorithm for each independent agent and conduct extensive experiments to verify the performance of our solution.

Accurate and fast per-flow size traffic measurement is fundamental to some network applications, e.g., load balancing, anomaly detection, traffic engineering, especially in face of the processing and memory constraints of switches. Sketch, a compact data structure, can output high-fidelity approximate perflow statistics. However, most existing sketches such as Count-Min are trapped in the dilemma between a large counting range and memory waste, due to the highly skewed characteristics of traffic size distribution. In this paper, we propose an adaptive counter-splicing-based sketch for per-flow size measurement. Specifically, we first allocate a small number of bits for each counter to handle mouse flows, and then splice several basic counters on the same layer to satisfy the counting range requirement for elephant flows. Extensive experiments based on real-world datasets CAIDA show that our proposed sketch can achieve better estimation performance in per-flow size estimation, flow size distribution, entropy estimation, heavy hitter detection, and heavy change detection, compared to several existing algorithms.

The multi-armed bandit (MAB) models have always received lots of attention from multiple research communities due to their broad application domains. The optimal selection problem with unknown rewards in advance, such as ad recommendation in social networks, spectrum access in the cognitive radio field, etc., can be efficiently solved by using MAB models. In an MAB model, given$N$arms whose rewards are unknown in advance, the player selects exactly one arm in each round, and his goal is to maximize the cumulative rewards over a fixed horizon. Further, a more general model called combinatorial MAB (i.e., CMAB), where$K$arms can be played simultaneously in each round, is put forward. However, the existing CMAB models neglect the strategic behaviors of the$N$arms, which indicates that one arm might report false information to increase its own profits. In fact, in many applications such as user selection in crowdsensing, the arms are not the feelingless machines but the rational individuals. To this end, we combine the upper confidence bound (UCB) with auction theory to develop a new algorithm called auction-based UCB (AUCB). We divide the auction-based CMAB problem into two sub-problems: winning arm selection and payment computation problems. For AUCB, we derive an upper bound on regret and prove the truthfulness in one round, individual rationality, and computational efficiency. In addition, we consider an extended situation that some arms may be unavailable in some rounds and the arms will bid inconsistently in different rounds. We devise another algorithm called eAUCB to solve this problem. Extensive simulations are conducted to show the significant performance of the proposed algorithms.

In this paper, we investigate the incentive problem in Spatial Crowdsourcing (SC), where mobile social-aware workers have unknown qualities and can share their answers to tasks via social networks. The objectives are to recruit high-quality workers and maximize all parties’ utilities simultaneously. However, most existing works assume that the qualities of workers are known in advance or cannot take all parties’ utilities into account together, especially having not considered the impact of social networks. Thus, we propose an incentive mechanism based on the multi-armed bandit and three-stage Stackelberg game, called TACT. We first design a greedy arm-pulling scheme to recruit workers, which not only can solve the exploration-exploitation dilemma but also takes workers’ social relations into account. Based on the recruitment results, we further design the utility functions incorporating with social benefits for workers, and model the payment computation problem as a three-stage Stackelberg game among all participants. Next, we derive the optimal strategy group so that each party can maximize its own utility to form a multi-win situation. Moreover, we theoretically prove the unique existence of Stackelberg equilibrium and the worst regret bound. Finally, we conduct extensive simulations on a real trace to corroborate the performance of TACT.

Per-flow traffic measurement in the high-speed network plays an important role in many practical applications. Due to the limited on-chip memory and the mismatch between off-chip memory speed and line rate, sampling-based methods select and forward a part of flow traffic to off-chip memory, which complements sketch-based solutions in estimation accuracy and online query support. However, most current work uses the same sampling probability for all flows, leading to the waste in storage and communication resources. In practice, different flows often require different sampling rates to meet the same accuracy constraint. This paper presents self-adaptive sampling, a framework to sample each flow with a probability adapted to flow size/spread. Then we propose three algorithms, SAS-LC, SAS-LOG, and SAS-HYB. SAS-LC and SAS-LOG are geared towards per-flow spread estimation and per-flow size estimation by using different compression functions. SAS-HYB combines the advantages of SAS-LC and SAS-LOG, showing higher efficiency when both small flows and large flows are interested. We implement our estimators in hardware using NetFPGA. Experimental results based on real Internet traces show that, compared to the state-of-the-art in per-flow spread estimation, SAS-LC can save around 10% on-chip space and reduce up to 40% communication cost for large flows. In per-flow size estimation, SAS-LOG can save 40% on-chip space and reduce up to 96% communication costs for large flows. Moreover, SAS-HYB’s on-chip memory usage will not be larger than SAS-LC or SAS-LOG and can save up to 19% on-chip space than SAS-LOG when both small flows and large flows are interested.

Blockchain came to prominence as the distributed ledger underneath Bitcoin, which protects the transaction histories in a fully-connected, peer-to-peer network. The blockchain mining process requires high computing power to solve a Proof-of-Work (PoW) puzzle, which is hard to implement on users’ mobile devices. So these miners may leverage the edge/cloud service providers (ESPs/CSP) to calculate the PoW puzzle. The existing edge-assisted blockchain networks assumed that all ESPs have a uniform propagation delay, which is unrealistic. In this article, we consider a more practical scene where ESPs locate in diverse positions of the blockchain network, which causes different propagation delays when supporting the computation of the PoW puzzle. Additionally, these ESPs connect to a remote CSP for resource scheduling when the computing tasks exceed their maximum capacity. The blockchain mining process generally involves complicated competition and games among CSP, ESPs, and miners. Each service provider focuses on how to determine his resource price so that he can maximize his utility. According to the set resource price, each miner concentrates on scheduling his resource requests for each ESP to maximize individual personal utility, which depends on ESPs’ resource price and propagation delays. We first model such a resource pricing and scheduling problem as a three-stage multi-leader multi-follower Stackelberg game and aim at finding the Stackelberg equilibrium. Then, we analyze the subgame optimization problem in each stage and propose an iterative algorithm based on backward induction to achieve the Nash equilibrium of the Stackelberg game. Finally, extensive simulations are conducted to verify the significant performance of the proposed solution.

As the popularity of mobile devices continues to increase, Mobile Crowdsensing (MC), a scalable and efficient data collection method, has received widespread attention. Although lots of effort has been devoted to studying the task assignment or worker recruitment in MC, most of them focus on how to maximize the profit from the perspective of the platform while ignoring rational individual workers' entitlement. We creatively start from the worker's perspective to find the task selection strategy to maximize the worker's profit. In this paper, the problem of unknown task selection is modeled as a Multi-Armed Bandit (MAB), on which three types of additional constraints are considered. The first constraint is the device budget. Workers choose and conduct tasks before it is exhausted. The second constraint is the personal preference regarding the traveling cost. The third constraint is the balance requirement of the MC platform, which has regulations on the tasks' execution rounds. In addition to the dilemma between exploration and exploitation in the classical MAB, we have to face the tradeoff between the reward and all the constraints above. To this end, we first adopt the epoch-style algorithm to reduce the number of switches between any two sensing tasks and further build new algorithms to deal with different constraints. The traveling cost and platform balance are involved in the task index computation as a penalty. We conduct extensive simulations based on real-world traces to verify the significant performance of our proposed algorithms.

Detecting heavy hitters that constitute the majority of network traffic is a critical task in network measurement. However, the highly skewed network traffic and the size-limited on-chip memory pose great challenges for heavy-hitter detection. The prior arts either use sketches to track all flows or maintain a fix-sized tracking list for recording elephant flows, resulting in limited detection precision or time-consuming tracking list exchanges. This paper presents HeavyTracker, an efficient algorithm that detects heavy hitters based on a count-with-threshold strategy. A two-dimensional tracker unit array is employed in our design to capture the heavy hitters, where each flow is randomly mapped to one unit in all rows. The tracker unit is designed to accept many flows and precisely report the largest two with frequencies that reach a predefined threshold. This design eliminates the frequent and time-consuming exchanges for maintaining the tracking list, allowing us to use a hash table to track the reported elephant flows. Experimental results based on real Internet traces show that HeavyTracker achieves a high $\mathbf{F}_{\beta}$-Score of threshold-t detection (0.97) and over 99% precision of top-k detection under a tight memory size. Besides, it reduces the frequency estimation error by 97.4% compared to the state-of-the-art.

Per-flow spread measurement in high-speed networks can provide indispensable information to many practical applications. However, it is challenging to measure millions of flows at line speed because on-chip memory modules cannot simultaneously provide large capacity and large bandwidth. The prior studies address this mismatch by entirely using on-chip compact data structures or utilizing off-chip space to assist limited on-chip memory. Nevertheless, their on-chip data structures record massive transient elements, each of which only appears in a short time interval in a long-period measurement task, and thus waste significant on-chip space. This paper presents short-term memory sampling, a novel spread estimator that samples new elements while only holding elements for short periods. Our estimator can work with tiny on-chip space and provide accurate estimations for online queries. The key of our design is a short-term memory duplicate filter that reports new elements and filters duplicates effectively while allowing incoming elements to override the stale elements to reduce on-chip memory usage. We implement our approach on a NetFPGA-equipped prototype. Experimental results based on real Internet traces show that, compared to the state-of-the-art, short-term memory sampling reduces up to 99% of on-chip memory usage when providing the same probabilistic assurance on spread-estimation error.

Per-flow size measurement is a fundamental problem in network engineering and plays a pivotal role in many practical applications. Constrained by on-chip memory resources and packet processing speed, most existing solutions use compact data structures (i.e., sketches) to perform the line-speed measurement. However, sketches share the record units (bits/counters) among flows, inevitably introducing noises to each flow’s measurement result. Although they adopt an average denoising strategy to remove noises from the raw estimations, the accuracy for medium flows is still lacking. This paper complements the prior art and presents a novel per-flow size measurement method, Adaptive Denoising (ADN), which can provide more accurate estimates for online and offline queries. For an online query, we use the collected flow records for real-time estimation. For an offline query, we model the propagation of noises based on the optimization algorithm to produce flow size estimation with much better accuracy. Experimental results based on real Internet traffic traces show that our measurement solutions outperform the state-of-the-art approaches and reduce the mean absolute error by around one order of magnitude under the same on-chip memory usage.

Federated learning (FL) is a newly emerging distributed machine learning paradigm, whereby a server can coordinate multiple clients to jointly train a learning model by using their private datasets. Many researches focus on designing incentive mechanisms in FL, but most of them cannot allow that clients flexibly determine privacy budgets by themselves. In this article, we propose a privacy-preserving incentive mechanism (NICE) based on differential privacy (DP) and Stackelberg game for FL systems in industrial Internet of Things. First, we design a flexible privacy-preserving mechanism for NICE, in which clients can add a Laplace noise into the loss function according to a customized privacy budget. Under this mechanism, we design two incentive utility functions for the server and clients. Next, we model the utility optimization problems as a two-stage Stackelberg game by seeing the server as a leader and the clients as followers. Finally, we derive an optimal Stackelberg equilibrium solution for both the stages of the whole game. Based on this solution, NICE can make the server and all clients achieve their maximum utilities simultaneously. In addition, we conduct extensive simulations on real-world datasets to demonstrate the significant performance of the proposed mechanism.

Mobile crowdsensing, through which a requester can coordinate a crowd of workers to complete some sensing tasks, has attracted significant attention recently. In this paper, we focus on the unknown worker recruitment problem in mobile crowdsensing, where workers’ sensing qualities are unknown a priori. We consider the scenario of recruiting workers to complete some continuous sensing tasks. The whole process is divided into multiple rounds. In each round, every task may be covered by more than one recruited workers, but its completion quality only depends on these workers’ maximum sensing quality. Each recruited worker will incur a cost and each task is attached a weight to indicate its importance. Our objective is to determine a recruiting strategy to maximize the total weighted completion quality under a limited budget. We model such unknown worker recruitment process as anovel combinatorial multi-armed bandit(CMAB) problem, and propose an unknown worker recruitment algorithm based on the modified upper confidence bound (UCB). Moreover, we extend the problem to the case where the workers’ costs are also unknown and design the corresponding algorithm. We analyze the regret bounds of the two proposed algorithms through rigorous proofs. In addition, we also study the unknown worker recruitment problem with fairness constraints. Here, the term “fairness” means that the platform must guarantee a minimum selection fraction for each registered worker, so that the platform can avoid the scenario where some workers are over-recruited but some others might be under-recruited. For this problem, we devise a fairness-aware unknown worker recruitment algorithm. Finally, we demonstrate the performance of the proposed algorithms through extensive simulations on real-world traces

Mobile CrowdSensing (MCS), through which a requester can coordinate a crowd of workers to accomplish some data collection tasks, has been recognized as a promising paradigm for large-scale data acquisition in recent years. Many researches focus on the worker recruitment problem in MCS, but most of them either have the assumption that workers’ qualities are known ahead of time or cannot ensure that workers report costs honestly. In this paper, we propose an incentive mechanism based on Combinatorial Multi-Armed Bandit and reverse Auction, called CMABA, to solve the multiple unknown workers recruitment problem in MCS. Our objective is to determine a recruiting strategy to maximize the total sensing quality under a limited budget, while ensuring truthfulness and individual rationality of sensing workers. We theoretically prove that our CMABA mechanism achieves truthfulness and individual rationality, and then analyze the regret of the mechanism. Based on CMABA, we ulteriorly propose an adaptive incentive mechanism, called ACMABA, to recruit workers via the alternative worker recruitment and quality update, which can achieve a higher total sensing quality and lower regret. Additionally, we also demonstrate significant performances of the CMABA and ACMABA mechanisms through extensive simulations on real-world data traces.

Traffic signal control is essential to efficient transportation networks since it can mitigate traffic congestion significantly. Trial-and-error approach in reinforcement learning will lead to traffic jams, even traffic accidents in the real scene, which is in violation of safety for traffic signal control. Besides, most signal control systems still rely on oversimplified information, which makes item challenging to adapt to dynamic traffic. In this paper, we focus on the edge coordinated optimization of large-scale traffic signal control, and propose a two-layeR edge-assisted pressUre balaNce (RUN) approach based on cooperative game. The external layer utilizes cooperative game to divide the traffic network into multiple coalitions. The internal layer uses pressure control and weighted queue to coordinate actions within each coalition and handle dynamic traffic situations over time. We derive a Pareto stable solution for the multi-intersection signal cooperative game with pressure control, and prove that it is non-superadditive. Moreover, we conduct extensive simulations to verify the significant performances of RUN based on both real data and synthetic data.

With the rapid development of the Internet of Things (IoT), massive high-speed data streams are produced every moment, making accurate size estimation a challenging task. Many sketches have been proposed to summarize real-time high-speed data streams and provide per-flow size estimations. However, sketches have to share the memory units to fit in limited on-chip space, inevitably introducing noises to all flows and resulting in over-estimation problems. Prior work adopts an average denoising strategy to remove the same noise from raw sketch estimations. However, they overlook that the noise distribution is highly skewed, leading to inaccurate results for most flows. This paper proposes an efficient Adaptive Noise Correction (ANC) framework, which analyzes the noise of each flow on a case-by-case basis and provides accurate size estimations. The key of our design is to build an ML model to predict a weight coefficient that indicates the noises in raw estimations, which is conducted for each flow by analyzing the neighbor flows whose memory units overlap with the given flow. Then we introduce a novel Probabilistic Cold Filter to block the tiny flows and assist in noise correction. Experimental results based on real Internet traces show that our framework can effectively remove the noises for different sketches, showing better estimation accuracy than the state-of-the-art.

Online anomalous taxi trajectory detection, which identifies anomalies from ongoing taxi trajectories, has become an important and fundamental concern in many real-world applications. Most of the existing studies define the anomalous trajectories as the ones deviating from the majority of routes or showing abnormal driving time and distance at the same time. However, due to the complexity of road conditions and the variety of passenger preferences, those methods have large false-positive rates, i.e., reporting many normal routes as anomalies. A high false-positive rate is harmful since false alarms will 1) bring unnecessary panic to passengers, 2) cause fiscally punishments to normal drivers, and 3) wastes human resource to deal with drivers' complaints. To this end, this paper proposes an online anomalous trajectory detection method, namely multidimensional criteria based anomalous trajectory (MCAT), to identify anomalous trajectories online. It judges anomalies by considering multidimensional criteria (similarity, time, distance) at the same time, reducing the false positives without sacrificing false negative rates. We evaluate the proposed method based on the real-world taxi data collected from Shanghai, China. The experimental results demonstrate that our method can outperform state-of-the-art methods in terms of accuracy, false-negative rate, and false-positive rate.

Per-flow traffic measurement in the high-speed network plays an important role in many practical applications. Due to the limited on-chip memory and the mismatch between off-chip memory speed and line rate, sampling-based methods select and forward a part of flow traffic to off-chip memory, complementing sketch-based solutions in estimation accuracy and online query support. However, most current work uses the same sampling probability for all flows, overlooking that the sampling rates different flows require to meet the same accuracy constraint are different. It leads to a waste in storage and communication resources. In this paper, we present self-adaptive sampling, a framework to sample each flow with a probability adapted to flow size/spread. Then we propose two algorithms, SAS-LC and SAS-LOG, which are geared towards per-flow spread estimation and per-flow size estimation by using different compression functions. Experimental results based on real Internet traces show that, when compared to NDS in per-flow spread estimation, SAS-LC can save around 10% on-chip space and reduce up to 40% communication cost for large flows. Moreover, SAS-LOG can save 40% on-chip space and reduce up to 96% communication cost for large flows than NDS in per-flow size estimation.

The multi-armed bandit (MAB) model has been deeply studied to solve many online learning problems, such as rate allocation in communication networks, Ad recommendation in social networks, etc. In an MAB model, given N arms whose rewards are unknown in advance, the player selects exactly one arm in each round, and his goal is to maximize the cumulative rewards over a fixed horizon. In this paper, we study the budget-constrained auction-based combinatorial multi-armed bandit mechanism with strategic arms, where the player can select K (<; N) arms in a round and pulling each arm has a unique cost. In addition, each arm might strategically report its cost in the auction. To this end, we combine the upper confidence bound (UCB) with auction to define the UCB-based rewards and then devise an auction-based UCB algorithm (called AUCB). In each round, AUCB selects the top K arms according to the ratios of UCB-based rewards to bids and further determines the critical payment for each arm. For AUCB, we derive an upper bound on regret and prove the truthfulness, individual rationality, and computational efficiency. Extensive simulations show that the rewards achieved by AUCB are at least 12.49% higher than those of state-of-the-art algorithms.

Currently, the blockchain, as a key enabling technology of digital currency, has attracted lots of attention from both industry and academia. The blockchain mining process requires high computing power to solve a Proof-of-Work (PoW) puzzle, which is hard to implement on users’ mobile devices. So these miners may leverage the resources of the edge/cloud service providers (ESPs/CSP) to calculate the PoW puzzle. The existing edge-assisted blockchain networks simply assumed that all ESPs have a uniform propagation delay, which is not realistic. In this paper, we consider a more practical scene where ESPs with distributed geographic locations have diverse propagation delays when supporting the computation of the PoW puzzle. Additionally, the blockchain mining process generally involves the complicated competition and game among these ESPs and miners. Each ESP focuses on how to determine his resource price and to select the requests from the miners, so that he can maximize his utility. According to the set resource price, each miner concentrates on scheduling his resource requests for each ESP to maximize his individual utility which depends on ESPs’ resource price and propagation delays. We model such a resource pricing and scheduling problem as a multi-leader multi-follower Stackelberg game and aim at finding the joint maximization of the utilities of each ESP and each individual miner. We prove the existence and uniqueness of the Stackelberg equilibrium (SE) and meanwhile propose an algorithm to achieve the corresponding SE. Finally, extensive simulations are conducted to verify the significant performance of the proposed solution.

Edge cloud computing is a new paradigm in which the computation and storage services of remote cloud data centers are moved to Edge Cloud Nodes (ECNs) in network edges. Compared to traditional cloud data centers, ECNs are geographically close to mobile users so the communication latency is significantly reduced. In this paper, we study the problem of allocating Virtual Machine (VM) resources in geo-distributed ECNs to mobile users by using the auction theory. First, we treat mobile users and ECNs as the buyers and sellers of the VM resource auction, respectively. Then, we model the VM resource allocation problem as an$n$-to-one weighted bipartite graph matching problem with 0-1 knapsack constraints. Since this problem is NP-hard, we design a greedy approximation algorithm to determine the winners of the auction, based on which we propose a truthful Auction-based VM resource Allocation (AVA) mechanism to solve the problem. Moreover, we prove that the AVA mechanism not only achieves an approximately optimal solution for winner selection, but also has the properties of truthfulness, individual rationality, and computational efficiency. Finally, we conduct extensive simulations on real traces to verify the significant performances of the proposed AVA mechanism.

Mobile CrowdSensing (MCS), through which a requester can coordinate a crowd of workers to accomplish some data collection tasks, has been recognized as a promising paradigm for large-scale data acquisition in recent years. Although many MCS systems have been built for various applications, most of them either assume that workers’ qualities are known in advance or cannot ensure workers to report costs honestly. In this paper, we propose an incentive mechanism based on Combinatorial Multi-Armed Bandit and reverse Auction, called CMABA, to solve the multiple unknown workers recruitment problem in MCS. Our objective is to determine a recruiting strategy to maximize the total sensing quality under a limited budget, while ensuring truthfulness and individual rationality of sensing workers. We theoretically prove that our CMABA mechanism achieves truthfulness and individual rationality, and then analyze the regret of the mechanism. Additionally, we also demonstrate its significant performances through extensive simulations on real-world data traces.

Federated Learning (FL) is a newly-emerging distributed ML model, where a server can coordinate multiple workers to cooperatively train a learning model by using their private datasets, while ensuring these datasets not to be revealed to others. In this paper, we focus on the incentive mechanism design for FL systems. Taking the incentives into consideration, we first design two utility functions for the server and workers, respectively. Then, we model the corresponding utility optimization problem as a two-stage Stackelberg game by seeing the server as a leader and the workers as some followers. Next, we derive an optimal Equilibrium solution for the both stages of the whole game. Based on this solution, we design an incentive mechanism that can ensure the server to achieve the optimal utility, while stimulating workers to do their best to train the ML model. Finally, we conduct extensive simulations to demonstrate the significant performance of the proposed mechanism.

Mobile crowdsensing, through which a requester can coordinate a crowd of workers to complete some sensing tasks, has attracted significant attention recently. In this paper, we focus on the unknown worker recruitment problem in mobile crowdsensing, where workers' sensing qualities are unknown a priori. We consider the scenario of recruiting workers to complete some continuous sensing tasks. The whole process is divided into multiple rounds. In each round, every task may be covered by more than one recruited workers, but its completion quality only depends on these workers' maximum sensing quality. Each recruited worker will incur a cost, and each task is attached a weight to indicate its importance. Our objective is to determine a recruiting strategy to maximize the total weighted completion quality under a limited budget. We model such an unknown worker recruitment process as a novel combinatorial multi-armed bandit problem, and propose an extended UCB based worker recruitment algorithm. Moreover, we extend the problem to the case where the workers' costs are also unknown and design the corresponding algorithm. We analyze the regrets of the two proposed algorithms and demonstrate their performance through extensive simulations on real-world traces.

Along with the generation of Internet of Things (IoT), the values of tremendous volumes of sensing data will be slowly unlocked. Thus, crowd-sensed data trading as a new business paradigm has recently attracted increasing attention. A typical data trading system contains a platform, data consumers, and crowd workers. The platform recruits crowd workers to collect data and then sells the data to consumers. In this article, we design a differentially private crowd-sensed data trading mechanism, called DPDT, to preserve the identity privacy of consumers and the task privacy against crowd workers during the data collection process, simultaneously. DPDT consists of a differentially private auction-based data pricing algorithm and a differentially private data collection algorithm. The data pricing algorithm achieves a good approximation to the maximum revenue. Meanwhile, it guarantees (e2- 1)ϵ-truthfulness and 2ϵ-differential privacy, where ϵ > 0 is a small constant. The data collection algorithm is able to effectively protect the data collection task privacy against crowd workers. We prove that this data collection algorithm achieves δ-approximate ϵ-differential privacy, where δ <; 1/e is a small constant, and meanwhile guarantees a tight bound of the expected approximation ratio. At last, extensive simulations are conducted to verify the significant performance of DPDT.

Mobile crowdsensing is a new paradigm in which a requester can recruit a group of mobile users via a platform and coordinate them to perform some sensing tasks by using their smartphones. In mobile crowdsensing, each user might perform multiple tasks with different sensing qualities. Meanwhile, the users participating in the crowdsensing will ask for sufficient rewards to compensate for their expenditures. Hence, an important problem is how to recruit the users with minimum cost while achieving a satisfactory sensing quality for each task. Furthermore, in order to ease users' worries about privacy disclosures, the user recruitment process needs to protect each user's sensing quality and recruitment cost information from being revealed to other users or to the platform. In this paper, we propose two secure user recruitment problems for the cases where the recruitment costs of users are homogeneous and heterogeneous. After proving the NP-hardness of the problems, we design two secure user recruitment protocols by using secret sharing scheme. Both of the proposed protocols adopt greedy strategies, which can recruit nearly optimal users while ensuring that the total sensing quality of each task is no less than a given threshold. The difference lies in that the two greedy strategies are based on two unique utility functions. We analyze the approximation ratios of the two protocols and prove the security under the semi-honest model. Finally, we demonstrate the significant performance of the proposed protocols through extensive simulations and executions on real smartphones.

Mobile crowdsensing, through which a requester can recruit a group of crowd workers via a platform and coordinate them to perform some sensing tasks, has attracted lots of attention recently. However, most of the existing mobile crowdsensing systems assume that the qualities of workers are known in advance. Based on this assumption, they study the task assignment and worker recruitment problems. Unfortunately, the qualities of workers are generally unknown in reality, so the platform must find the tradeoff between exploring and exploiting the qualities by using reinforcement learning. At the same time, all sensing tasks are required to be covered in each round (covering constraint), and the requester usually has a limited budget (budget constraint). In this paper, we study how to recruit unknown workers under the budget and covering constraints so that the total expected achieved qualities can be maximized. To this end, we model the problem as a combination of a maximum weight matching problem and a special multi-armed bandit problem. We first consider that the recruitment costs of workers are homogeneous and propose a recruitment algorithm with a performance guarantee. Then, we study the heterogenous case and devise a heuristic algorithm. Finally, we demonstrate the performances of our algorithms through extensive simulations.

The ride-hailing system has become popular around the world. The Service Providers (SPs) such as Uber and Didi dispatch passenger orders based on their location information. However, one concern from the public is whether the SPs could protect the location privacy of passengers. In this paper, we propose an order dispatch scheme that could preserve the location privacy of passengers based on their requirements. Our scheme uses cloaking regions in which the SPs cannot distinguish actual locations of passengers. The trade-off is the loss of matching performance or social welfare, i.e., the increase in the overall pick-up distance. We formulate the problem as maximizing the social welfare (or minimizing the overall pick-up distances) under privacy requirements of passengers. A bipartite-matching-based scheme is investigated, and we provide a theoretical bound on the matching performance under specific privacy requirements. Nevertheless, minimizing the overall pick-up distances does not consider the interest of each individual passenger. Passengers with low privacy requirements may be matched with drivers far from them. Therefore, we further propose a pricing scheme that could make up for the individual loss by allocating discounts on their riding fares. Especially, three discount allocation strategies are proposed in this paper. Experiments on both real-world and synthetic datasets show the efficiency of our scheme.

Recently, influence maximization in social networks has attracted great attention. In this paper, we consider that a company intends to select some users to promote its multiple products (called influences) in online social network consisting of many communities, in which each user has different preferences for each influence. We focus on the Minimum Cost Seed Selection (MCSS) problem for multiple influences, that is, how to select some seeds with minimum cost so that the average influenced probability of all users in each community is not less than a threshold. To solve the MCSS problem, we design a submodular utility function, based on which we turn our problem into a non-trivial set cover problem with non-linear constraints. After proving the NP-hardness of MCSS, we propose a greedy algorithm, called G-MCSS, to solve it. We analyze the approximation ratio of G-MCSS. Additionally, we extend the MCSS problem to a complex case, where the number of acceptable influences for each user is limited, and the cost is proportional to the number of allocated influences. We further propose another greedy algorithm to solve the extended problem. Finally, we demonstrate the significant performances of our algorithms through extensive experiments based on real social network traces.

In this paper, we focus on the incentive mechanism design for a vehicle-based, nondeterministic crowdsensing system. In this crowdsensing system, vehicles move along their trajectories and perform corresponding sensing tasks with different probabilities. Each task may be performed by multiple vehicles jointly so as to ensure a high probability of success. Designing an incentive mechanism for such a crowdsensing system is challenging since it contains a non-trivial set cover problem. To solve this problem, we propose a truthful, reverse-auction-based incentive mechanism that includes an approximation algorithm to select winning bids with a nearly minimum social cost and a payment algorithm to determine payments for all participants. Moreover, we extend the problem to a more complex case in which the Quality of sensing Data (QoD) of each vehicle is taken into consideration. For this problem, we propose a QoD-aware incentive mechanism, which consists of a QoD-aware winning-bid selection algorithm and a QoD-aware payment determination algorithm. We prove that the proposed incentive mechanisms have truthfulness, individual rationality, and computational efficiency. Moreover, we analyze the approximation ratios of the winning-bid selection algorithms. The simulations, based on a real vehicle trace, also demonstrate the significant performances of our incentive mechanisms.

Due to the explosive proliferation of mobile cloud computing applications, much data needs to be transmitted between mobile users and clouds, incurring a huge traffic demand on cellular networks. Mobile offloading is a promising approach to address this challenge. In this paper, we focus on the problem of offloading many deadline-sensitive data items to some WiFi networks with capacity constraints; that is, how to schedule each data item to the WiFi networks, so that we can offload as many data items before their deadlines as possible, while taking the constraints of transmission capacity into consideration. This problem involves a probabilistic combination of multiple 0-1 knapsack constraints, which differs from existing problems. To solve this problem, we propose a greedy oFfline Data Offloading (FDO) algorithm, achieving an approximation ratio of 2. Also, we propose an oNline Data Offloading (NDO) algorithm, which has a competitive ratio of 2. Additionally, we extend our problem to a more general scenario where WiFi transmission costs are heterogeneous. We design a Heterogeneous Data Offloading (HDO) algorithm to solve the extended problem, and give its performance analysis. Finally, we demonstrate the significant performances of our algorithms through extensive simulations based on some real-world and synthetic WiFi datasets.

Traditional taxi-hailing systems through wireless networks in metropolitan areas allow taxis to compete for passengers chaotically and accidentally, which generally result in inefficiencies, long waiting time and low satisfaction of taxi-hailing passengers. In this paper, we propose a new Mobile Taxi-hailing System (called MTS) based on optimal multi-taxi dispatch, which can be used by taxi service companies (TSCs). Different from the competition modes used in traditional taxi-hailing systems, MTS assigns vacant taxis to taxi-hailing passengers proactively. For the taxi dispatch problem in MTS, we define a system utility function, which involves the total net profits of taxis and waiting time of passengers. Moreover, in the utility function, we take into consideration the various classes of taxis with different resource configurations, and the cost associated with taxis' empty travel distances. Our goal is to maximize the system utility function, restricted by the individual net profits of taxis and the passengers' requirements for specified classes of taxis. To solve this problem, we design an optimal algorithm based on the idea of Kuhn-Munkres (called KMBA), and prove the correctness and optimality of the proposed algorithm. Additionally, we demonstrate the significant performances of our algorithm through extensive simulations.

Nowadays, vehicles have shown great potential in crowdsensing. To guarantee a good Quality of Service (QoS), stimulating enough vehicles to participate in crowdsensing is very necessary. In this paper, we focus on the incentive mechanism design in the vehicle-based nondeterministic crowdsensing. Different from existing works, we take into consideration that each vehicle performs sensing tasks along some trajectories with different probabilities, and each task must be successfully performed with a joint probability no less than a threshold. Designing an incentive mechanism for such a nondeterministic crowdsensing system is challenging, which contains a non-trivial set cover problem with non-linear constraints. To solve the problem, we propose a truthful incentive mechanism based on reverse auction, including an approximation algorithm to select winning bids with a nearly minimum social cost, and a payment algorithm to determine the payments for all participants. Through theoretical analysis, we prove that our incentive mechanism is truthful and individual rational, and we give an approximation ratio of the winning bid selection algorithm. In addition, we conduct extensive simulations, based on a real vehicle trace, to validate the performances of the proposed incentive mechanism.

With the explosive proliferation of smartphones, many mobile cloud computing applications have emerged in recent years. These applications generally involve many data transmissions between mobile users and the cloud side. In order to reduce the monetary cost of these data transmissions, an effective approach is to offload partial data traffic from cellular networks to WiFi networks, when mobile users pass by some WiFi Access Points (APs). In this paper, we focus on the problem of offloading many deadline-sensitive data items to some WiFi APs with capacity constraints; that is, how to schedule each data item to the WiFi APs, so that we can offload as many data items before their deadlines as possible, while taking the constraints of transmission capacity into consideration. This problem involves a probabilistic combination of multiple 0-1 knapsack constraints, which differs from existing problems. To solve this problem, we propose a greedy oFfline Data Offloading (FDO) algorithm, and prove that this algorithm can achieve an approximation ratio of 2. Moreover, we extend our data offloading strategy to the online decision case, and propose an oNline Data Offloading (NDO) algorithm, which has a competitive ratio of 2. Finally, we demonstrate the significant performances of our algorithms through extensive simulations.