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Sherman Shen

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University of Zagreb

Uppsala University

University of East London

Armando Marques-Guedes

UNL - New University of Lisbon

University of Leicester

Gwen Robbins Schug

University of North Carolina at Greensboro

Gabriel Gutierrez-Alonso

University of Salamanca

Macquarie University

Universidade Federal do Rio Grande do Sul

Swansea University

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Papers by Sherman Shen

Exploiting temporal dependency for opportunistic forwarding in urban vehicular networks

Inter-contact times (ICTs) between moving objects are one of the key metrics in vehicular network... more Inter-contact times (ICTs) between moving objects are one of the key metrics in vehicular networks, and they are also central to forwarding algorithms and the end-to-end delay. Recent study on the tail distribution of ICTs based on theoretical mobility models and empirical trace data shows that the delay between two consecutive contact opportunities drops exponentially. While theoretical results facilitate problem analysis, how to design practical opportunistic forwarding protocols in vehicular networks, where messages are delivered in carry-and-forward fashion, is still unclear. In this paper, we study three large sets of Global Positioning System (GPS) traces of more than ten thousand public vehicles, collected from Shanghai and Shenzhen, two metropolises in China. By mining the temporal correlation and the evolution of ICTs between each pair of vehicles, we develop higher order Markov chains to characterize urban vehicular mobility patterns, which adapt as ICTs between vehicles continuously get updated. Then, the next hop for message forwarding is determined based on the previous ICTs. With our message forwarding strategy, it can dramatically increase delivery ratio (up to 80%) and reduce end-to-end delay (up to 50%) while generating similar network traffic comparing to current strategies based on the delivery probability or the expected delay.

Cloud-Edge Coordinated Processing: Low-Latency Multicasting Transmission

IEEE Journal on Selected Areas in Communications, May 1, 2019

Recently, edge caching and multicasting arise as two promising technologies to support highdata-r... more Recently, edge caching and multicasting arise as two promising technologies to support highdata-rate and low-latency delivery in wireless communication networks. In this paper, we design three transmission schemes aiming to minimize the delivery latency for cache-enabled multigroup multicasting networks. In particular, full caching bulk transmission scheme is first designed as a performance benchmark for the ideal situation where the caching capability of each enhanced remote radio head (eRRH) is sufficient large to cache all files. For the practical situation where the caching capability of each eRRH is limited, we further design two transmission schemes, namely partial caching bulk transmission (PCBT) and partial caching pipelined transmission (PCPT) schemes. In the PCBT scheme, eRRHs first fetch the uncached requested files from the baseband unit (BBU) and then all requested files are simultaneously transmitted to the users. In the PCPT scheme, eRRHs first transmit the cached requested files while fetching the uncached requested files from the BBU. Then, the remaining cached requested files and fetched uncached requested files are simultaneously transmitted to the users. The design goal of the three transmission schemes is to minimize the delivery latency, subject to some practical constraints. Efficient algorithms are developed for the low-latency cloud-edge coordinated transmission strategies. Numerical results are provided to evaluate the performance of the proposed S. He, J. Ren, and Y. Zhang are with the

A Cross-Layer Design Approach to Multicast in Wireless Networks

IEEE Transactions on Wireless Communications, Mar 1, 2007

We study rate optimization for multicast communications at the media access control (MAC) layer, ... more We study rate optimization for multicast communications at the media access control (MAC) layer, and explore transport layer erasure coding to enhance multicast reliability in wireless networks. We start with investigating network models with single-input-single-output (SISO) links. For Threshold-T based multicast policies, we characterize the optimal transmission rates that maximize the throughput in stable networks and in saturated networks, respectively. We investigate the tradeoff between stability and throughput therein. We then generalize our study to network models with multiple-input-multiple-output (MIMO) links and non-i.i.d. channel links, and investigate the optimal transmission rate. In addition, to ensure multicast reliability while no retransmission is required at the MAC layer, we propose to use transport layer erasure coding for reliability enhancement, where the problem boils down to jointly optimizing the transmission rate and the multicast threshold. We provide a solution to this optimization problem accordingly.

SATS: Secure Data-Forwarding Scheme for Delay-Tolerant Wireless Networks

2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011

In this paper, we propose a secure data-forwarding scheme, called SATS, for delay-tolerant wirele... more In this paper, we propose a secure data-forwarding scheme, called SATS, for delay-tolerant wireless networks. SATS uses credits (or micropayment) to stimulate the nodes' cooperation in relaying other nodes' messages and to enforce fairness. SATS also makes use of a trust system to assign a trust value for each node. A node's trust value is high when the node actively forwards others' messages. The highly trusted nodes are preferable in data forwarding to avoid the Black-Hole attackers that drop messages intentionally to degrade the message delivery rate. In this way, SATS can stimulate the nodes' cooperation not only to earn credits but also to maintain high trust values to increase their chances to participate in future data forwarding. Our security evaluation demonstrates that SATS can secure the payment and trust calculation. The performance evaluation demonstrates that SATS can significantly improve the message delivery rate due to avoiding the Black-Hole attackers in message forwarding and stimulating the nodes' cooperation.

A Federated Learning Based Privacy-Preserving Smart Healthcare System

IEEE Transactions on Industrial Informatics, 2022

The rapid development of the smart healthcare system makes the early-stage detection of dementia ... more The rapid development of the smart healthcare system makes the early-stage detection of dementia disease more user-friendly and affordable. However, the main concern is the potential serious privacy leakage of the system. In this article, we take Alzheimer's disease (AD) as an example and design a convenient and privacy-preserving system named ADDETECTOR with the assistance of Internet of Things ( ) devices and security mechanisms. Particularly, to achieve effective AD detection, ADDETECTOR only collects user's audio by IoT devices widely deployed in the smart home environment and utilizes novel topic-based linguistic features to improve the detection accuracy. For the privacy breach existing in data, feature, and model levels, ADDETECTOR achieves privacy-preserving by employing a unique three-layer (i.e., user, client, cloud, etc.) architecture. Moreover, ADDETECTOR exploits federated learning (FL) based scheme to ensure the user owns the integrity of raw data and secure the confidentiality of the classification model and implement differential privacy (DP) mechanism to enhance the privacy level of the feature. Furthermore, to secure the model aggregation process between clients and cloud in FL-based scheme, a novel asynchronous privacy-preserving aggregation framework is designed. We evaluate ADDETECTOR on 1010 AD detection trials from 99 health and AD users. The experimental results show that ADDETECTOR achieves high

V2X Empowered Non-Signalized Intersection Management in the AI Era: Opportunities and Solutions

IEEE Communications Standards Magazine, 2020

With significant advancements of vehicle-to-everything (V2X) communication technologies in recent... more With significant advancements of vehicle-to-everything (V2X) communication technologies in recent years, intelligent collaboration between connected vehicles and roadside units provides new opportunities for better road safety and vehicle traffic management via innovative non-signalized intersections. In this article, to deal with sophisticated traffic information brought about by a dynamic non-signalized intersection environment, artificial intelligence (AI) solutions together with V2X communication technologies are proposed to provide data-driven intersection management strategies. We first present the emerging technologies and key challenges toward V2X empowered non-signalized intersection management. By introducing the applications of typical AI technologies, we pinpoint three main research issues on V2X empowered non-signalized intersection management, leveraging various AI approaches. Finally, we present a case study where a multi-agent learning approach is applied for intelligent multiple intersection management to demonstrate the effectiveness of our non-signalized intersection solution.

Roadside Units Deployment for Efficient Short-time Certificate Updating in VANETs Roadside Units Deployment for Efficient Short-time Certificate Updating in VANETs

2.2/index.php/pptvt/comment/add/495/0 Copyright ©2009 IEEE. Personal use of this material is perm... more 2.2/index.php/pptvt/comment/add/495/0 Copyright ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Guest Editorial: Artificial Intelligence Empowered Future Connection

IEEE Network, 2021

Towards an Ideally Scheduled Route Optimization Algorithm for Improved Throughput in Multi-hop Wireless Networks

Multipath Transmission for Wireless Internet Access--From an End-to-End Transport Layer Perspective

Journal of Internet Technology, 2012

With the growing demand of Internet services, network operators have put significant efforts to i... more With the growing demand of Internet services, network operators have put significant efforts to improve network error resilience and efficiency. Since there exist different wired/wireless technologies for Internet access such as digital subscriber line (DSL), Ethernet, and worldwide interoperability for microwave access (WiMax), a mobile host can use multiple access networks simultaneously with multipath transmission. Taking the advantage of heterogeneous environment, multipath transmission through the Internet can improve service reliability and network flexibility. Ensuring a reliable end-to-end connection oriented communication with satisfactory quality of service (QoS) and maintaining congestion control and flow control are the main responsibilities of the Transmission Control Protocol (TCP), the dominant transport layer protocol in the Internet. In this paper, we survey the state-of-the-art of multipath transmission techniques for QoS provisioning in wireless Internet access, f...

Age-of-Information Aware Scheduling for Edge-Assisted Industrial Wireless Networks

IEEE Transactions on Industrial Informatics, 2021

Industrial wireless networks (IWNs) have attracted significant attention for providing time-criti... more Industrial wireless networks (IWNs) have attracted significant attention for providing time-critical delivery services, which can benefit from device-to-device (D2D) communication for low transmission delay. In this article, a distributed scheduling problem is investigated for D2D-enabled IWNs, where D2D links have various ageof-information (AoI) constraints for information freshness. This problem is formulated as a constrained optimization problem to optimize D2D packet delivery over limited spectrum resources, which is intractable since D2D users have no prior knowledge of the operating environment. To tackle this problem, in this article, an AoI-aware scheduling scheme is proposed based on primal-dual optimization and actor-critic reinforcement learning. In specific, multiple local actors for D2D devices learn AoI-aware scheduling policies to make on-site decisions with their stochastic AoI constraints addressed in the dual domain. An edge-based critic estimates the performance of all actors' decisionmaking policies from a global view, which can effectively address the nonstationary environment caused by concurrent learning of multiple local actors. Theoretical analysis on the convergence of learning is provided and simulation results demonstrate the effectiveness of the proposed scheme.

Cloud-Edge Coordinated Processing: Low-Latency Multicasting Transmission

IEEE Journal on Selected Areas in Communications, 2019

Recently, edge caching and multicasting arise as two promising technologies to support highdata-r... more Recently, edge caching and multicasting arise as two promising technologies to support highdata-rate and low-latency delivery in wireless communication networks. In this paper, we design three transmission schemes aiming to minimize the delivery latency for cache-enabled multigroup multicasting networks. In particular, full caching bulk transmission scheme is first designed as a performance benchmark for the ideal situation where the caching capability of each enhanced remote radio head (eRRH) is sufficient large to cache all files. For the practical situation where the caching capability of each eRRH is limited, we further design two transmission schemes, namely partial caching bulk transmission (PCBT) and partial caching pipelined transmission (PCPT) schemes. In the PCBT scheme, eRRHs first fetch the uncached requested files from the baseband unit (BBU) and then all requested files are simultaneously transmitted to the users. In the PCPT scheme, eRRHs first transmit the cached requested files while fetching the uncached requested files from the BBU. Then, the remaining cached requested files and fetched uncached requested files are simultaneously transmitted to the users. The design goal of the three transmission schemes is to minimize the delivery latency, subject to some practical constraints. Efficient algorithms are developed for the low-latency cloud-edge coordinated transmission strategies. Numerical results are provided to evaluate the performance of the proposed S. He, J. Ren, and Y. Zhang are with the

Peer Collaboration in Wireless Ad Hoc Networks

NETWORKING 2005. Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications Systems, 2005

Voluntary peer collaboration is often assumed in media access, route discovery, packet forwarding... more Voluntary peer collaboration is often assumed in media access, route discovery, packet forwarding, and upper-layer protocols for wireless ad hoc networks. This assumption is seriously challenged when some peers are autonomous, selfish, or malicious in large-scale, heterogeneous networks. In this paper, based on the latest advances in identitybased cryptography, we design a lightweight and cheat-resistant micropayment scheme to stimulate and compensate collaborative peers that sacrifice their resources to relay packets for other peers. We also demonstrate that when security and collaboration measures are properly enforced, profitable collaboration is a preferable strategy for all peers.

Efficient Data Access Algorithms for ITS-based Networks with Multi-Hop Wireless Links

2007 IEEE International Conference on Communications, 2007

In this paper, we investigate efficient data access algorithms in intelligent transportation syst... more In this paper, we investigate efficient data access algorithms in intelligent transportation system (ITS)-based networks with multi-hop wireless links. We introduce a proxy cache (PC) and propose PC-based poll-each-read (P-PER) and PCbased callback (P-CB) data access algorithms to reduce the transmission cost over the bottleneck wireless links. Extensive simulation results are given to demonstrate the performance of P-PER and P-CB. It is shown that P-PER and P-CB can improve the cache hit performance and reduce the transmission cost significantly. A tradeoff between P-PER and P-CB suggests the need to use a hybrid proxy-based approach to attain optimal performance of data access in ITS-based networks with multihop wireless links.

Locating base-stations for video sensor networks

Vehicular Technology Conference, 1988, IEEE 38th

For a wireless video sensor network (WiViSeN) where video nodes have been placed at some strategi... more For a wireless video sensor network (WiViSeN) where video nodes have been placed at some strategic locations to capture designated scenes, an immediate challenge is to locate the base-station optimally such that the network lifetime of batterypowered video nodes can be maximized. This paper presents two schemes, one centralized and the other distributed, to obtain the optimal base-station location algorithmically under the proposed definition of topological lifetime. The upper and lower bounds of maximal topological lifetime are derived to enable a quick assessment of energy provisioning feasibility and topology control necessity. In addition, the proposed research provides a foundation to introduce the relay and cluster techniques that can further prolong network lifetime.

Footprint: Detecting Sybil Attacks in Urban Private Vehicular Networks

In private vehicular networks, where privacy, especially the location privacy of anonymous vehicl... more In private vehicular networks, where privacy, especially the location privacy of anonymous vehicles is highly concerned, anonymous verification of vehicles is indispensable. Consequently, an attacker who succeeds in forging multiple hostile identifies can easily launch a Sybil attack, gaining a disproportionately large influence. In this paper, we propose a novel Sybil attack detection mechanism Footprint using the trajectories of vehicles for identification while still preserving their location privacy. More specifically, when a vehicle approaches a road-side unit (RSU), it actively demands an authorized message from the RSU as the proof of appearance at this RSU and time. We design a location-hidden authorized message generation scheme for two objectives: first, RSU signatures on messages are signer-ambiguous so that the RSU location information is concealed from the resulted authorized message; second, two authorized messages signed by the same RSU within the same given period of time (temporarily linkable) are recognizable so that they can be used for identification. With the temporal limitation on the linkability of two authorized messages, authorized messages used for long-term identification is prohibited. With this scheme, vehicles can generate a location-hidden trajectory for location-privacy-preserved identification by collecting a consecutive series of authorized messages. Utilizing social relationship among trajectories according to the similarity definition of two trajectories, Footprint can recognize and therefore dismiss "communities" of Sybil trajectories. Rigorous security analysis and extensive trace-driven simulations demonstrate the efficacy of Footprint.

Integrity-oriented content transmission in highway vehicular ad hoc networks

2013 Proceedings IEEE INFOCOM, 2013

The effective inter-vehicle transmission of content files, e.g., images, music and video clips, i... more The effective inter-vehicle transmission of content files, e.g., images, music and video clips, is the basis of media communications in vehicular networks, such as social communications and video sharing. However, due to the presence of diverse node velocities, severe channel fadings and intensive mutual interferences among vehicles, the inter-vehicle or vehicle-to-vehicle (V2V) communications tend to be transient and highly dynamic. Content transmissions among vehicles over the volatile and spotty V2V channels are thus susceptible to frequent interruptions and failures, resulting in many fragment content transmissions which are unable to finish during the connection time and unusable by on-top media applications. The interruptions of content transmissions not only lead to the failure of media presentations to users, but the transmission of the invalid fragment contents would also result in the significant waste of precious vehicular bandwidth. On addressing this issue, in this work we target on provisioning the integrity-oriented inter-vehicle content transmissions. Given the initial distance and mobility statistics of vehicles, we develop an analytical framework to evaluate the data volume that can be transmitted upon the short-lived and spotty V2V connection from the source to the destination vehicle. Provided the content file size, we are able to evaluate the likelihood of successful content transmissions through the model. Based upon this analysis, we propose an admission control scheme at the transmitters, that filters the suspicious content transmission requests which are unlikely to be accomplished over the transient inter-vehicle links. Using extensive simulations, we demonstrate the accuracy of the developed analytical model, and the effectiveness of the proposed admission control scheme. In the simulated scenario, with the proposed admission control scheme applied, it is observed that about 30% of the network bandwidth can be saved for effective content transmissions.

Vulnerabilities in distance-indexed IP traceback schemes

International Journal of Security and Networks, 2007

In order to counter Denial-of-Service (DoS) attacks using spoofed source addresses, many IP trace... more In order to counter Denial-of-Service (DoS) attacks using spoofed source addresses, many IP traceback schemes have been proposed in the last few years. Among them, distanceindexed probabilistic packet marking schemes appear to be very attractive. In this paper, we first discover two intrinsic vulnerabilities in these schemes. Substantiated by efficacy analysis and numerical results, several exploits are designed to take advantage of these vulnerabilities in an efficient manner when compared with the traceback effort attempted by victims. Consequently, we show that the design goal of these schemes can be compromised in practice. Further, we discuss these vulnerabilities in a general context relevant to network protocols and examine a few possible alternatives.

Vehicular Passenger Mobility-Aware Bandwidth Allocation in Mobile Hotspots

IEEE Transactions on Wireless Communications, 2014

In this paper, we propose a vehicular passenger mobility-aware bandwidth allocation (V-MBA) schem... more In this paper, we propose a vehicular passenger mobility-aware bandwidth allocation (V-MBA) scheme in mobile hotspots. The V-MBA scheme consists of both call admission control and bandwidth adjustment functions to lower handoff vehicle service dropping probability and efficiently utilize resource of base station. Specifically, a handoff priority scheme with guard bandwidth is employed to protect handoff vehicle service. Also, bandwidth is dynamically assigned to each vehicle by exploiting vehicular passenger movement pattern that includes getting on and off events at a station. We evaluate the V-MBA scheme by developing a continuous-time Markov chain model. Simulation results demonstrate that the V-MBA scheme can guarantee low new vehicle service blocking probability and handoff vehicle service dropping probability through flexible bandwidth allocation.

FESCIM: Fair, Efficient, and Secure Cooperation Incentive Mechanism for Multihop Cellular Networks

IEEE Transactions on Mobile Computing, 2012

In multihop cellular networks, the mobile nodes usually relay others' packets for enhancing the n... more In multihop cellular networks, the mobile nodes usually relay others' packets for enhancing the network performance and deployment. However, selfish nodes usually do not cooperate but make use of the cooperative nodes to relay their packets, which has a negative effect on the network fairness and performance. In this paper, we propose a fair and efficient incentive mechanism to stimulate the node cooperation. Our mechanism applies a fair charging policy by charging the source and destination nodes when both of them benefit from the communication. To implement this charging policy efficiently, hashing operations are used in the ACK packets to reduce the number of public-key-cryptography operations. Moreover, reducing the overhead of the payment checks is essential for the efficient implementation of the incentive mechanism due to the large number of payment transactions. Instead of generating a check per message, a small-size check can be generated per route, and a check submission scheme is proposed to reduce the number of submitted checks and protect against collusion attacks. Extensive analysis and simulations demonstrate that our mechanism can secure the payment and significantly reduce the checks' overhead, and the fair charging policy can be implemented almost computationally free by using hashing operations.

Exploiting temporal dependency for opportunistic forwarding in urban vehicular networks

Inter-contact times (ICTs) between moving objects are one of the key metrics in vehicular network... more Inter-contact times (ICTs) between moving objects are one of the key metrics in vehicular networks, and they are also central to forwarding algorithms and the end-to-end delay. Recent study on the tail distribution of ICTs based on theoretical mobility models and empirical trace data shows that the delay between two consecutive contact opportunities drops exponentially. While theoretical results facilitate problem analysis, how to design practical opportunistic forwarding protocols in vehicular networks, where messages are delivered in carry-and-forward fashion, is still unclear. In this paper, we study three large sets of Global Positioning System (GPS) traces of more than ten thousand public vehicles, collected from Shanghai and Shenzhen, two metropolises in China. By mining the temporal correlation and the evolution of ICTs between each pair of vehicles, we develop higher order Markov chains to characterize urban vehicular mobility patterns, which adapt as ICTs between vehicles continuously get updated. Then, the next hop for message forwarding is determined based on the previous ICTs. With our message forwarding strategy, it can dramatically increase delivery ratio (up to 80%) and reduce end-to-end delay (up to 50%) while generating similar network traffic comparing to current strategies based on the delivery probability or the expected delay.

Cloud-Edge Coordinated Processing: Low-Latency Multicasting Transmission

IEEE Journal on Selected Areas in Communications, May 1, 2019

Recently, edge caching and multicasting arise as two promising technologies to support highdata-r... more Recently, edge caching and multicasting arise as two promising technologies to support highdata-rate and low-latency delivery in wireless communication networks. In this paper, we design three transmission schemes aiming to minimize the delivery latency for cache-enabled multigroup multicasting networks. In particular, full caching bulk transmission scheme is first designed as a performance benchmark for the ideal situation where the caching capability of each enhanced remote radio head (eRRH) is sufficient large to cache all files. For the practical situation where the caching capability of each eRRH is limited, we further design two transmission schemes, namely partial caching bulk transmission (PCBT) and partial caching pipelined transmission (PCPT) schemes. In the PCBT scheme, eRRHs first fetch the uncached requested files from the baseband unit (BBU) and then all requested files are simultaneously transmitted to the users. In the PCPT scheme, eRRHs first transmit the cached requested files while fetching the uncached requested files from the BBU. Then, the remaining cached requested files and fetched uncached requested files are simultaneously transmitted to the users. The design goal of the three transmission schemes is to minimize the delivery latency, subject to some practical constraints. Efficient algorithms are developed for the low-latency cloud-edge coordinated transmission strategies. Numerical results are provided to evaluate the performance of the proposed S. He, J. Ren, and Y. Zhang are with the

A Cross-Layer Design Approach to Multicast in Wireless Networks

IEEE Transactions on Wireless Communications, Mar 1, 2007

We study rate optimization for multicast communications at the media access control (MAC) layer, ... more We study rate optimization for multicast communications at the media access control (MAC) layer, and explore transport layer erasure coding to enhance multicast reliability in wireless networks. We start with investigating network models with single-input-single-output (SISO) links. For Threshold-T based multicast policies, we characterize the optimal transmission rates that maximize the throughput in stable networks and in saturated networks, respectively. We investigate the tradeoff between stability and throughput therein. We then generalize our study to network models with multiple-input-multiple-output (MIMO) links and non-i.i.d. channel links, and investigate the optimal transmission rate. In addition, to ensure multicast reliability while no retransmission is required at the MAC layer, we propose to use transport layer erasure coding for reliability enhancement, where the problem boils down to jointly optimizing the transmission rate and the multicast threshold. We provide a solution to this optimization problem accordingly.

SATS: Secure Data-Forwarding Scheme for Delay-Tolerant Wireless Networks

2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011

In this paper, we propose a secure data-forwarding scheme, called SATS, for delay-tolerant wirele... more In this paper, we propose a secure data-forwarding scheme, called SATS, for delay-tolerant wireless networks. SATS uses credits (or micropayment) to stimulate the nodes' cooperation in relaying other nodes' messages and to enforce fairness. SATS also makes use of a trust system to assign a trust value for each node. A node's trust value is high when the node actively forwards others' messages. The highly trusted nodes are preferable in data forwarding to avoid the Black-Hole attackers that drop messages intentionally to degrade the message delivery rate. In this way, SATS can stimulate the nodes' cooperation not only to earn credits but also to maintain high trust values to increase their chances to participate in future data forwarding. Our security evaluation demonstrates that SATS can secure the payment and trust calculation. The performance evaluation demonstrates that SATS can significantly improve the message delivery rate due to avoiding the Black-Hole attackers in message forwarding and stimulating the nodes' cooperation.

A Federated Learning Based Privacy-Preserving Smart Healthcare System

IEEE Transactions on Industrial Informatics, 2022

The rapid development of the smart healthcare system makes the early-stage detection of dementia ... more The rapid development of the smart healthcare system makes the early-stage detection of dementia disease more user-friendly and affordable. However, the main concern is the potential serious privacy leakage of the system. In this article, we take Alzheimer's disease (AD) as an example and design a convenient and privacy-preserving system named ADDETECTOR with the assistance of Internet of Things ( ) devices and security mechanisms. Particularly, to achieve effective AD detection, ADDETECTOR only collects user's audio by IoT devices widely deployed in the smart home environment and utilizes novel topic-based linguistic features to improve the detection accuracy. For the privacy breach existing in data, feature, and model levels, ADDETECTOR achieves privacy-preserving by employing a unique three-layer (i.e., user, client, cloud, etc.) architecture. Moreover, ADDETECTOR exploits federated learning (FL) based scheme to ensure the user owns the integrity of raw data and secure the confidentiality of the classification model and implement differential privacy (DP) mechanism to enhance the privacy level of the feature. Furthermore, to secure the model aggregation process between clients and cloud in FL-based scheme, a novel asynchronous privacy-preserving aggregation framework is designed. We evaluate ADDETECTOR on 1010 AD detection trials from 99 health and AD users. The experimental results show that ADDETECTOR achieves high

V2X Empowered Non-Signalized Intersection Management in the AI Era: Opportunities and Solutions

IEEE Communications Standards Magazine, 2020

With significant advancements of vehicle-to-everything (V2X) communication technologies in recent... more With significant advancements of vehicle-to-everything (V2X) communication technologies in recent years, intelligent collaboration between connected vehicles and roadside units provides new opportunities for better road safety and vehicle traffic management via innovative non-signalized intersections. In this article, to deal with sophisticated traffic information brought about by a dynamic non-signalized intersection environment, artificial intelligence (AI) solutions together with V2X communication technologies are proposed to provide data-driven intersection management strategies. We first present the emerging technologies and key challenges toward V2X empowered non-signalized intersection management. By introducing the applications of typical AI technologies, we pinpoint three main research issues on V2X empowered non-signalized intersection management, leveraging various AI approaches. Finally, we present a case study where a multi-agent learning approach is applied for intelligent multiple intersection management to demonstrate the effectiveness of our non-signalized intersection solution.

Roadside Units Deployment for Efficient Short-time Certificate Updating in VANETs Roadside Units Deployment for Efficient Short-time Certificate Updating in VANETs

2.2/index.php/pptvt/comment/add/495/0 Copyright ©2009 IEEE. Personal use of this material is perm... more 2.2/index.php/pptvt/comment/add/495/0 Copyright ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Guest Editorial: Artificial Intelligence Empowered Future Connection

IEEE Network, 2021

Towards an Ideally Scheduled Route Optimization Algorithm for Improved Throughput in Multi-hop Wireless Networks

Multipath Transmission for Wireless Internet Access--From an End-to-End Transport Layer Perspective

Journal of Internet Technology, 2012

With the growing demand of Internet services, network operators have put significant efforts to i... more With the growing demand of Internet services, network operators have put significant efforts to improve network error resilience and efficiency. Since there exist different wired/wireless technologies for Internet access such as digital subscriber line (DSL), Ethernet, and worldwide interoperability for microwave access (WiMax), a mobile host can use multiple access networks simultaneously with multipath transmission. Taking the advantage of heterogeneous environment, multipath transmission through the Internet can improve service reliability and network flexibility. Ensuring a reliable end-to-end connection oriented communication with satisfactory quality of service (QoS) and maintaining congestion control and flow control are the main responsibilities of the Transmission Control Protocol (TCP), the dominant transport layer protocol in the Internet. In this paper, we survey the state-of-the-art of multipath transmission techniques for QoS provisioning in wireless Internet access, f...

Age-of-Information Aware Scheduling for Edge-Assisted Industrial Wireless Networks

IEEE Transactions on Industrial Informatics, 2021

Industrial wireless networks (IWNs) have attracted significant attention for providing time-criti... more Industrial wireless networks (IWNs) have attracted significant attention for providing time-critical delivery services, which can benefit from device-to-device (D2D) communication for low transmission delay. In this article, a distributed scheduling problem is investigated for D2D-enabled IWNs, where D2D links have various ageof-information (AoI) constraints for information freshness. This problem is formulated as a constrained optimization problem to optimize D2D packet delivery over limited spectrum resources, which is intractable since D2D users have no prior knowledge of the operating environment. To tackle this problem, in this article, an AoI-aware scheduling scheme is proposed based on primal-dual optimization and actor-critic reinforcement learning. In specific, multiple local actors for D2D devices learn AoI-aware scheduling policies to make on-site decisions with their stochastic AoI constraints addressed in the dual domain. An edge-based critic estimates the performance of all actors' decisionmaking policies from a global view, which can effectively address the nonstationary environment caused by concurrent learning of multiple local actors. Theoretical analysis on the convergence of learning is provided and simulation results demonstrate the effectiveness of the proposed scheme.

Cloud-Edge Coordinated Processing: Low-Latency Multicasting Transmission

IEEE Journal on Selected Areas in Communications, 2019

Recently, edge caching and multicasting arise as two promising technologies to support highdata-r... more Recently, edge caching and multicasting arise as two promising technologies to support highdata-rate and low-latency delivery in wireless communication networks. In this paper, we design three transmission schemes aiming to minimize the delivery latency for cache-enabled multigroup multicasting networks. In particular, full caching bulk transmission scheme is first designed as a performance benchmark for the ideal situation where the caching capability of each enhanced remote radio head (eRRH) is sufficient large to cache all files. For the practical situation where the caching capability of each eRRH is limited, we further design two transmission schemes, namely partial caching bulk transmission (PCBT) and partial caching pipelined transmission (PCPT) schemes. In the PCBT scheme, eRRHs first fetch the uncached requested files from the baseband unit (BBU) and then all requested files are simultaneously transmitted to the users. In the PCPT scheme, eRRHs first transmit the cached requested files while fetching the uncached requested files from the BBU. Then, the remaining cached requested files and fetched uncached requested files are simultaneously transmitted to the users. The design goal of the three transmission schemes is to minimize the delivery latency, subject to some practical constraints. Efficient algorithms are developed for the low-latency cloud-edge coordinated transmission strategies. Numerical results are provided to evaluate the performance of the proposed S. He, J. Ren, and Y. Zhang are with the

Peer Collaboration in Wireless Ad Hoc Networks

NETWORKING 2005. Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications Systems, 2005

Voluntary peer collaboration is often assumed in media access, route discovery, packet forwarding... more Voluntary peer collaboration is often assumed in media access, route discovery, packet forwarding, and upper-layer protocols for wireless ad hoc networks. This assumption is seriously challenged when some peers are autonomous, selfish, or malicious in large-scale, heterogeneous networks. In this paper, based on the latest advances in identitybased cryptography, we design a lightweight and cheat-resistant micropayment scheme to stimulate and compensate collaborative peers that sacrifice their resources to relay packets for other peers. We also demonstrate that when security and collaboration measures are properly enforced, profitable collaboration is a preferable strategy for all peers.

Efficient Data Access Algorithms for ITS-based Networks with Multi-Hop Wireless Links

2007 IEEE International Conference on Communications, 2007

In this paper, we investigate efficient data access algorithms in intelligent transportation syst... more In this paper, we investigate efficient data access algorithms in intelligent transportation system (ITS)-based networks with multi-hop wireless links. We introduce a proxy cache (PC) and propose PC-based poll-each-read (P-PER) and PCbased callback (P-CB) data access algorithms to reduce the transmission cost over the bottleneck wireless links. Extensive simulation results are given to demonstrate the performance of P-PER and P-CB. It is shown that P-PER and P-CB can improve the cache hit performance and reduce the transmission cost significantly. A tradeoff between P-PER and P-CB suggests the need to use a hybrid proxy-based approach to attain optimal performance of data access in ITS-based networks with multihop wireless links.

Locating base-stations for video sensor networks

Vehicular Technology Conference, 1988, IEEE 38th

For a wireless video sensor network (WiViSeN) where video nodes have been placed at some strategi... more For a wireless video sensor network (WiViSeN) where video nodes have been placed at some strategic locations to capture designated scenes, an immediate challenge is to locate the base-station optimally such that the network lifetime of batterypowered video nodes can be maximized. This paper presents two schemes, one centralized and the other distributed, to obtain the optimal base-station location algorithmically under the proposed definition of topological lifetime. The upper and lower bounds of maximal topological lifetime are derived to enable a quick assessment of energy provisioning feasibility and topology control necessity. In addition, the proposed research provides a foundation to introduce the relay and cluster techniques that can further prolong network lifetime.

Footprint: Detecting Sybil Attacks in Urban Private Vehicular Networks

In private vehicular networks, where privacy, especially the location privacy of anonymous vehicl... more In private vehicular networks, where privacy, especially the location privacy of anonymous vehicles is highly concerned, anonymous verification of vehicles is indispensable. Consequently, an attacker who succeeds in forging multiple hostile identifies can easily launch a Sybil attack, gaining a disproportionately large influence. In this paper, we propose a novel Sybil attack detection mechanism Footprint using the trajectories of vehicles for identification while still preserving their location privacy. More specifically, when a vehicle approaches a road-side unit (RSU), it actively demands an authorized message from the RSU as the proof of appearance at this RSU and time. We design a location-hidden authorized message generation scheme for two objectives: first, RSU signatures on messages are signer-ambiguous so that the RSU location information is concealed from the resulted authorized message; second, two authorized messages signed by the same RSU within the same given period of time (temporarily linkable) are recognizable so that they can be used for identification. With the temporal limitation on the linkability of two authorized messages, authorized messages used for long-term identification is prohibited. With this scheme, vehicles can generate a location-hidden trajectory for location-privacy-preserved identification by collecting a consecutive series of authorized messages. Utilizing social relationship among trajectories according to the similarity definition of two trajectories, Footprint can recognize and therefore dismiss "communities" of Sybil trajectories. Rigorous security analysis and extensive trace-driven simulations demonstrate the efficacy of Footprint.

Integrity-oriented content transmission in highway vehicular ad hoc networks

2013 Proceedings IEEE INFOCOM, 2013

The effective inter-vehicle transmission of content files, e.g., images, music and video clips, i... more The effective inter-vehicle transmission of content files, e.g., images, music and video clips, is the basis of media communications in vehicular networks, such as social communications and video sharing. However, due to the presence of diverse node velocities, severe channel fadings and intensive mutual interferences among vehicles, the inter-vehicle or vehicle-to-vehicle (V2V) communications tend to be transient and highly dynamic. Content transmissions among vehicles over the volatile and spotty V2V channels are thus susceptible to frequent interruptions and failures, resulting in many fragment content transmissions which are unable to finish during the connection time and unusable by on-top media applications. The interruptions of content transmissions not only lead to the failure of media presentations to users, but the transmission of the invalid fragment contents would also result in the significant waste of precious vehicular bandwidth. On addressing this issue, in this work we target on provisioning the integrity-oriented inter-vehicle content transmissions. Given the initial distance and mobility statistics of vehicles, we develop an analytical framework to evaluate the data volume that can be transmitted upon the short-lived and spotty V2V connection from the source to the destination vehicle. Provided the content file size, we are able to evaluate the likelihood of successful content transmissions through the model. Based upon this analysis, we propose an admission control scheme at the transmitters, that filters the suspicious content transmission requests which are unlikely to be accomplished over the transient inter-vehicle links. Using extensive simulations, we demonstrate the accuracy of the developed analytical model, and the effectiveness of the proposed admission control scheme. In the simulated scenario, with the proposed admission control scheme applied, it is observed that about 30% of the network bandwidth can be saved for effective content transmissions.

Vulnerabilities in distance-indexed IP traceback schemes

International Journal of Security and Networks, 2007

In order to counter Denial-of-Service (DoS) attacks using spoofed source addresses, many IP trace... more In order to counter Denial-of-Service (DoS) attacks using spoofed source addresses, many IP traceback schemes have been proposed in the last few years. Among them, distanceindexed probabilistic packet marking schemes appear to be very attractive. In this paper, we first discover two intrinsic vulnerabilities in these schemes. Substantiated by efficacy analysis and numerical results, several exploits are designed to take advantage of these vulnerabilities in an efficient manner when compared with the traceback effort attempted by victims. Consequently, we show that the design goal of these schemes can be compromised in practice. Further, we discuss these vulnerabilities in a general context relevant to network protocols and examine a few possible alternatives.

Vehicular Passenger Mobility-Aware Bandwidth Allocation in Mobile Hotspots

IEEE Transactions on Wireless Communications, 2014

In this paper, we propose a vehicular passenger mobility-aware bandwidth allocation (V-MBA) schem... more In this paper, we propose a vehicular passenger mobility-aware bandwidth allocation (V-MBA) scheme in mobile hotspots. The V-MBA scheme consists of both call admission control and bandwidth adjustment functions to lower handoff vehicle service dropping probability and efficiently utilize resource of base station. Specifically, a handoff priority scheme with guard bandwidth is employed to protect handoff vehicle service. Also, bandwidth is dynamically assigned to each vehicle by exploiting vehicular passenger movement pattern that includes getting on and off events at a station. We evaluate the V-MBA scheme by developing a continuous-time Markov chain model. Simulation results demonstrate that the V-MBA scheme can guarantee low new vehicle service blocking probability and handoff vehicle service dropping probability through flexible bandwidth allocation.

FESCIM: Fair, Efficient, and Secure Cooperation Incentive Mechanism for Multihop Cellular Networks

IEEE Transactions on Mobile Computing, 2012

In multihop cellular networks, the mobile nodes usually relay others' packets for enhancing the n... more In multihop cellular networks, the mobile nodes usually relay others' packets for enhancing the network performance and deployment. However, selfish nodes usually do not cooperate but make use of the cooperative nodes to relay their packets, which has a negative effect on the network fairness and performance. In this paper, we propose a fair and efficient incentive mechanism to stimulate the node cooperation. Our mechanism applies a fair charging policy by charging the source and destination nodes when both of them benefit from the communication. To implement this charging policy efficiently, hashing operations are used in the ACK packets to reduce the number of public-key-cryptography operations. Moreover, reducing the overhead of the payment checks is essential for the efficient implementation of the incentive mechanism due to the large number of payment transactions. Instead of generating a check per message, a small-size check can be generated per route, and a check submission scheme is proposed to reduce the number of submitted checks and protect against collusion attacks. Extensive analysis and simulations demonstrate that our mechanism can secure the payment and significantly reduce the checks' overhead, and the fair charging policy can be implemented almost computationally free by using hashing operations.