Ruozhou Yu - Academia.edu (original) (raw)

Papers by Ruozhou Yu

Proceedings of the Twenty-First International Symposium on Theory, Algorithmic Foundations, and Protocol Design for Mobile Networks and Mobile Computing

Edge computing is one of the revolutionary technologies that enable high-performance and low-late... more Edge computing is one of the revolutionary technologies that enable high-performance and low-latency modern applications, such as smart cities, connected vehicles, etc. Yet its adoption has been limited by factors including high cost of edge resources, heterogeneous and uctuating demands, and lack of reliability. In this paper, we study resource provisioning in edge computing, taking into account these dierent factors. First, based on observations from real demand traces, we propose a time-varying stochastic model to capture the time-dependent and uncertain demand and network dynamics in an edge network. We then apply a novel robustness model that accounts for both expected and worst-case performance of a service. Based on these models, we formulate edge provisioning as a multi-stage stochastic optimization problem. The problem is NP-hard even in the deterministic case. Leveraging the multi-stage structure, we apply nested Benders decomposition to solve the problem. We also describe several eciency enhancement techniques, including a novel technique for quickly solving the large number of decomposed subproblems. Finally, we present results from real dataset-based simulations, which demonstrate the advantages of the proposed models, algorithm and techniques.

ICC 2022 - IEEE International Conference on Communications

Payment Channel Network (PCN) is an auspicious solution to the scalability issue of the blockchai... more Payment Channel Network (PCN) is an auspicious solution to the scalability issue of the blockchain, improving transaction throughput without relying on on-chain transactions. In a PCN, nodes can set prices for forwarding payments on behalf of other nodes, which motivates participation and improves network stability. Analyzing the price setting behaviors of PCN nodes plays a key role in understanding the economic properties of PCNs, but has been under-studied in the literature. In this paper, we apply equilibrium analysis to the price-setting game between two payment hubs in the PCN with limited channel capacities and partial overlap demand. We analyze existence of pure Nash Equilibriums (NEs) and bounds on the equilibrium revenue under various cases, and propose an algorithm to find all pure NEs. Using real data, we show bounds on the price of anarchy/stability and average transaction fee under realistic network conditions, and draw conclusions on the economic advantage of the PCN for making payment transfers by cryptocurrency users.

2020 IEEE Conference on Communications and Network Security (CNS)

Reputation systems, designed to remedy the lack of information quality and assess credibility of ... more Reputation systems, designed to remedy the lack of information quality and assess credibility of information sources, have become an indispensable component of many online systems. A typical reputation system works by tracking all information originating from a source, and the feedback to the information with its attribution to the source. The tracking of information and the feedback, though essential, could violate the privacy of users who provide the information and/or the feedback, which could both cause harm to the users’ online well-being, and discourage them from participation. Anonymous reputation systems have been designed to protect user privacy by ensuring anonymity of the users. Yet, current anonymous reputation systems suffer from several limitations, including but not limited to a)lack of support for core functionalities such as feedback update, b) lack of protocol efficiency for practical deployment, and c) reliance on a fully trusted authority. This paper proposes EARS, an anonymous reputation system that ensures user anonymity while supporting all core functionalities (including feedback update) of a reputation system both efficiently and practically, and without the need of a fully trusted central authority. We present security analysis of EARS against multiple types of attacks that could potentially violate user anonymity, such as feedback duplication, bad mouthing, and ballot stuffing. We also present evaluation of the efficiency and scalability of our system based on implementations.

2018 IEEE International Conference on Communications (ICC), 2018

The scarcity of spectrum channels resides in the limited bandwidth resource and the exploding dem... more The scarcity of spectrum channels resides in the limited bandwidth resource and the exploding demand from spectrum-based services and devices. To help ease this scarcity, the concept of cognitive radio networks (CRNs) is proposed, where licensed spectrum holders (primary users) may lease their channels to unlicensed users (secondary users). Many CRN auctions are thus designed to incentivize primary users (PUs) to share their idle channels with secondary users (SUs). Most of these auctions assume that a transmitting PU does not lease its channel to SUs; if it leases its channel to SUs, it does not transmit itself. To further utilize the resource, researchers have studied the scenario where a transmitting PU is allowed to lease its channels to SUs if the transmissions of the SUs do not undermine the transmission of the PU. However, the study assumes that there is only one PU who owns the licensed channels, whereas in practice, channels may be contributed by multiple PUs. This prevents the result of the study from being directly applied to the multi-PU scenario, as the potential competitions among the PUs are neglected. We extend the scenario to the CRN with multiple PUs and propose TDSA-PS as a Truthful Double Spectrum Auction with transmitting Primary users Sharing. We prove that TDSA-PS is truthful, individually rational, budget-balanced, and computationally efficient.

IEEE INFOCOM 2017 - IEEE Conference on Computer Communications, 2017

Cloud computing has emerged as a powerful and elastic platform for internet service hosting, yet ... more Cloud computing has emerged as a powerful and elastic platform for internet service hosting, yet it also draws concerns of the unpredictable performance of cloud-based services due to network congestion. To offer predictable performance, the virtual cluster abstraction of cloud services has been proposed, which enables allocation and performance isolation regarding both computing resources and network bandwidth in a simplified virtual network model. One issue arisen in virtual cluster allocation is the survivability of tenant services against physical failures. Existing works have studied virtual cluster backup provisioning with fixed primary embeddings, but have not considered the impact of primary embeddings on backup resource consumption. To address this issue, in this paper we study how to embed virtual clusters survivably in the cloud data center, by jointly optimizing primary and backup embeddings of the virtual clusters. We formally define the survivable virtual cluster embedding problem. We then propose a novel algorithm, which computes the most resource-efficient embedding given a tenant request. Since the optimal algorithm has high time complexity, we further propose a faster heuristic algorithm, which is several orders faster than the optimal solution, yet able to achieve similar performance. Besides theoretical analysis, we evaluate our algorithms via extensive simulations.

2016 IEEE Global Communications Conference (GLOBECOM), 2016

As more and more data-intensive applications have been moved to the cloud, the cloud network has ... more As more and more data-intensive applications have been moved to the cloud, the cloud network has become the new performance bottleneck for cloud applications. To boost application performance, the concept of coflow has been proposed to bring application-awareness into the cloud network. A coflow consists of many individual data flows, and a coflow is completed only when all its component flows are transmitted. The network performance of a cloud application is dependent on the completion time of coflows, rather than the completion time of each individual flow. Existing coflow-aware optimization solutions employ flow preemption to reduce the completion time, which brings difficulty in practical implementation and non-negligible overhead. In this paper, we study the non-preemptive coflow scheduling and routing problem in the cloud network. We propose an offline optimization framework for coflow scheduling, as well as two subroutines for coflow routing using single-path routing and multi-path routing respectively. We also show that our proposed framework is easily extensible to the online scenario. Extensive evaluations show that the proposed solutions can greatly reduce coflow completion time compared to coflow-agnostic solutions, and are also computationally efficient.

IEEE Internet of Things Journal, 2022

2019 IEEE Global Communications Conference (GLOBECOM), 2019

Blockchain Basics Blockchain is a distributed sequential / transactional data store (a ledger) wh... more Blockchain Basics Blockchain is a distributed sequential / transactional data store (a ledger) whose security (non-manipulability) is guaranteed via distributed consensus.

2020 IEEE 19th International Conference on Trust, Security and Privacy in Computing and Communications (TrustCom), 2020

Vehicular crowdsourcing networks (VCNs) enable vehicles to provide or obtain traffic-related serv... more Vehicular crowdsourcing networks (VCNs) enable vehicles to provide or obtain traffic-related services in a costefficient and flexible manner. Therefore, it is crucial to provide trusted management in VCNs for high reliability towards both service producers and consumers. However, most recent VCN platforms rely on a third party to manage crowdsourcing services which might be not fully trusted by users. For the issue, this paper proposes a blockchain-based trust management scheme for VCNs to provide a decentralized and trusted service management. A comprehensive trust evaluation model (TEM) is designed to quantify the trust degree of each vehicular node, and a vehicle-trust blockchain framework called VTchain is proposed to preserve the trust values of nodes while guaranteeing transparency and trustworthiness. Particularly, we leverage a trusted execution environment (TEE) to provide secure trust evaluation to tackle possible untrusted road-side units. In addition, we introduce TEM-based Proof of Trust to support blockchain maintenance, which works together with an efficient consensus algorithm Zyzzyva for improved scalability. Finally, extensive experiments are conducted by developing a testbed deployed on cloud servers for measurements.

IEEE Transactions on Intelligent Transportation Systems, 2020

Electric vehicles can place a significant load on the power grid due to their unscheduled chargin... more Electric vehicles can place a significant load on the power grid due to their unscheduled charging events. One way of improving power grid stability is to schedule electric vehicle charging in advance. Before a charging visit, the electric vehicle provides necessary information to request for charging at a charging station, which prepares and reserves the energy before the visit. However, the reported information can cause privacy leakage of the electric vehicle user. Anonymous information reporting can protect user privacy, but also enables attacks on the charging station by unauthorized users. An anonymous authentication system can address these issues, but cannot detect misbehaviors by authenticated users. One remedy to this is revocable anonymity-based authentication, which can revoke the anonymity of malicious users after their misbehaviors. However, we show that such a system is still vulnerable to application-level Denial of Service attacks, where a malicious user requests for large amounts of energy simultaneously from many charging stations, preventing these stations from serving other users. To address this, we improve upon an existing revocable anonymity-based authentication framework. We propose a permit-based mechanism, where each electric vehicle is only issued with one blind signature-based permit at a time. A request is valid only if it contains a valid and unused permit, which protects the system from the application-level Denial of Service attacks. Security analysis and experiments demonstrate that our framework, while ensuring user anonymity and being robust to the aforementioned attack, is also scalable and lightweight.

2016 IEEE International Conference on Communications (ICC), 2016

The ever increasing video demands from mobile users have posed great challenges to cellular netwo... more The ever increasing video demands from mobile users have posed great challenges to cellular networks. To address this issue, video caching in radio access networks (RANs) has been recognized as one of the enabling technologies in future 5G mobile networks, which brings contents near the end-users, reducing the transmission cost of duplicate contents, meanwhile increasing the Quality-of-Experience (QoE) of users. Inspired by the emerging software-defined networking technology, recent proposals have employed centralized collaborative caching among cells to further increase the caching capacity of the RAN. In this paper, we explore a new dimension in video caching in software-defined RANs to expand its capacity. We enable the controller with the capability to adaptively select the bitrates of videos received by users, in order to maximize the number and quality of video requests that can be served, meanwhile minimizing the transmission cost. To achieve this, we further incorporate Scalable Video Coding (SVC), which enables caching and serving sliced video layers that can serve different bitrates. We formulate the problem of joint video caching and scheduling as a reward maximization (cost minimization) problem. Based on the formulation, we further propose a 2-stage rounding-based algorithm to address the problem efficiently. Simulation results show that using SVC with collaborative caching greatly improves the cache capacity and the QoE of users.

IEEE INFOCOM 2021 - IEEE Conference on Computer Communications, 2021

Payment channel networks (PCNs) are proposed to improve the cryptocurrency scalability by settlin... more Payment channel networks (PCNs) are proposed to improve the cryptocurrency scalability by settling off-chain transactions. However, PCN introduces an undesirable assumption that a channel participant must stay online and be synchronized with the blockchain to defend against frauds. To alleviate this issue, watchtowers have been introduced, such that a hiring party can employ a watchtower to monitor the channel for fraud. However, a watchtower might profit from colluding with a cheating counterparty and fail to perform this job. Existing solutions either focus on heavy cryptographic techniques or require a large collateral. In this work, we leverage smart contracts through economic approaches to counter collusions for watchtowers in PCNs. This brings distrust between the watchtower and the counterparty, so that rational parties do not collude or cheat. We provide detailed analyses on the contracts and rigorously prove that the contracts are effective to counter collusions with minimal on-chain operations. In particular, a watchtower only needs to lock a small collateral, which incentivizes participation of watchtowers and users. We also provide an implementation of the contracts in Solidity and execute them on Ethereum to demonstrate the scalability and efficiency of the contracts.

2017 IEEE 37th International Conference on Distributed Computing Systems (ICDCS), 2017

With the proliferation of smart mobile devices (smart phone, tablet, and wearable), mobile crowds... more With the proliferation of smart mobile devices (smart phone, tablet, and wearable), mobile crowdsensing becomes a powerful sensing and computation paradigm. It has been put into application in many fields, such as spectrum sensing, environmental monitoring, healthcare, and so on. Driven by promising incentives, the power of the crowd grants crowdsensing an advantage in mobilizing users who perform sensing tasks with the embedded sensors on the smart devices. Auction is one of the commonly adopted crowdsensing incentive mechanisms to incentivize users for participation. However, it does not consider the incentive for user solicitation, where in crowdsensing, such incentive would ease the tension when there is a lack of crowdsensing users. To deal with this issue, we aim to design an auction-based incentive tree to offer rewards to users for both participation and solicitation. Meanwhile, we want the incentive mechanism to be robust against dishonest behavior such as untruthful bidding and sybil attacks, to eliminate malicious price manipulations. We design RIT as a Robust Incentive Tree mechanism for mobile crowdsensing which combines the advantages of auctions and incentive trees. We prove that RIT is truthful and sybil-proof with probability at least H, for any given H ∈ (0, 1). We also prove that RIT satisfies individual rationality, computational efficiency, and solicitation incentive. Simulation results of RIT further confirm our analysis.

IEEE INFOCOM 2019 - IEEE Conference on Computer Communications, 2019

Advances in virtualization technologies and edge computing have inspired a new paradigm for Inter... more Advances in virtualization technologies and edge computing have inspired a new paradigm for Internet-of-Things (IoT) application development. By breaking a monolithic application into loosely coupled microservices, great gain can be achieved in performance, flexibility and robustness. In this paper, we study the important problem of load balancing across IoT microservice instances. A key difficulty in this problem is the interdependencies among microservices: the load on a successor microservice instance directly depends on the load distributed from its predecessor microservice instances. We propose a graph-based model for describing the load dependencies among microservices. Based on the model, we first propose a basic formulation for load balancing, which can be solved optimally in polynomial time. The basic model neglects the quality-of-service (QoS) of the IoT application. We then propose a QoS-aware load balancing model, based on a novel abstraction that captures a realization of the application’s internal logic. The QoS-aware load balancing problem is NP-hard. We propose a fully polynomial-time approximation scheme for the QoS-aware problem. We show through simulation experiments that our proposed algorithm achieves enhanced QoS compared to heuristic solutions.

2018 27th International Conference on Computer Communication and Networks (ICCCN), 2018

Although cryptocurrencies have witnessed explosive growth in the past year, they have also raised... more Although cryptocurrencies have witnessed explosive growth in the past year, they have also raised many concerns, among which a crucial one is the scalability issue of blockchain-based cryptocurrencies. Suffering from the large overhead of global consensus and security assurance, even leading cryptocurrencies can only handle up to tens of transactions per second, which largely limits their applications in real- world scenarios. Among many proposals to improve cryptocurrency scalability, one of the most promising and mature solutions is the payment channel network (PCN), which offers off-chain settlement of transactions with minimal involvement of expensive blockchain operations. In this paper, we investigate the problem of payment routing in PCN. We suggest crucial design goals in PCN routing, and propose a novel distributed dynamic routing mechanism called CoinExpress. Through extensive simulations, we have shown that our proposed mechanism is able to achieve outstanding payment acceptance ratio with low routing overhead.

2017 IEEE International Conference on Edge Computing (EDGE), 2017

Finally, and most importantly, I would like to thank my family. I would like to especially thank ... more Finally, and most importantly, I would like to thank my family. I would like to especially thank my parents, for their 29-year great spiritual and material support. v

IEEE/ACM Transactions on Networking, 2019

The Internet-of-Things (IoT) has inspired numerous new applications ever since its invention. Nev... more The Internet-of-Things (IoT) has inspired numerous new applications ever since its invention. Nevertheless, its development and utilization have always been restricted by the limited resources in various application scenarios. In this paper, we study the problem of resource provisioning for real-time IoT applications, i.e., applications that process concurrent data streams from data sources in the network. We investigate joint application placement and data routing to support IoT applications that have both quality-of-service and robustness requirements. We formulate four versions of the provisioning problem, spanning across two important classes of real-time applications (parallelizable and non-parallelizable), and two provisioning scenarios (single application and multiple applications). All versions are proved to be NP-hard. We propose fully polynomial-time approximation schemes for three of the four versions, and a randomized algorithm for the forth. Through simulation experiments, we analyze the impact of parallelizability and robustness on the provisioning performance, and show that our proposed algorithms can greatly improve the quality-of-service of the IoT applications.

IEEE Communications Magazine, 2018

IEEE Transactions on Vehicular Technology, 2017

The drastic growth of mobile traffic greatly challenges the capacity of mobile infrastructures. D... more The drastic growth of mobile traffic greatly challenges the capacity of mobile infrastructures. Dense deployment of low-power small cells helps alleviate the congestion in the radio access network, yet it also introduces large complexity for network management. Software-defined radio access network has been proposed to tackle the added complexity. However, existing software-defined solutions rely on a fully centralized control plane to make decisions for the whole network, which greatly limits the scalability and responsiveness of the control plane. In this paper, we propose a hierarchical software-defined radio access network architecture. The proposed architecture leverages the hierarchical structure of radio access networks, deploying additional local controllers near the network edge. Utilizing the intrinsic locality in radio access networks, it offloads control tasks from the central controller to local controllers with limited overhead introduced. Under the architecture, a distributed optimization framework is proposed, and a typical optimization problem is studied to illustrate the effectiveness of the proposed architecture and framework. Both analysis and experiments validate that the proposed architecture and framework can improve the network objective during the optimization, meanwhile balancing load and improving scalability and responsiveness. Index Terms-Mobile 5G HetNets, radio access network, software-defined networking, distributed optimization I. INTRODUCTION Mobile traffic has undergone drastic growth in the last decade, owing to the advances of wireless broadband technologies and the wide spread of smart devices. Such growth greatly challenges the capacity of the current cellular infrastructure. A major technology invented to tackle this growth is the heterogeneous cellular networks (HetNets), which introduce densely-deployed low-power small base stations (SBSs) to reduce interference and increase system capacity. The dense deployment of SBSs brings new challenges to cellular radio access networks (RANs). First, large signaling and management overhead has been brought about by the heterogeneous location, channel, power and backhaul characteristics of base stations (BSs). Second, interference management becomes more complex due to more coupled

IEEE Transactions on Parallel and Distributed Systems, 2016

With the tremendous growth of cloud computing, it is increasingly critical to provide quantifiabl... more With the tremendous growth of cloud computing, it is increasingly critical to provide quantifiable performance to tenants and to improve resource utilization for the cloud provider. Though many recent proposals focus on guaranteeing job performance (with a particular note on network bandwidth) in the cloud, they usually lack efficient utilization of cloud resource, or vice versa. In this paper we present DCloud, which leverages the (soft) deadlines of cloud computing jobs to enable flexible and efficient resource utilization in data centers. With the deadline requirement of a job guaranteed, DCloud employs both time sliding (postponing the launching time of a job) and bandwidth scaling (adjusting the bandwidth associated with VMs) in resource allocation, so as to better match the resource allocated to the job with the cloud's residual resource. Extensive simulations and testbed experiments show that DCloud can accept much more jobs than existing solutions, and significantly increase the cloud provider's revenue with less cost for individual tenants.