Soon-Young Oh

Vehicular cloud networking: architecture and design principles

Over the past several decades, VANET has been a core networking technology to provide safety and comfort to drivers in vehicular environments. Emerging applications and services, however, require major changes to its underlying computing and networking models, which demand new network planning for VANET. This article especially examines how VANET evolves with two emerging paradigms: vehicular cloud computing and information-centric networking. VCC brings the mobile cloud model to vehicular networks and thus changes the way of network service provisioning, whereas ICN changes the notion of data routing and dissemination. We envision a new vehicular networking system, vehicular cloud networking, on top of them. This article scrutinizes its architecture and operations, and discusses its design principles.

Content Centric Networking in tactical and emergency MANETs

Reliable and secure content distribution in a disruptive environment is a critical challenge due to high mobile and lossy channels. Traditional IP networking and wireless protocols tend to perform poorly. In this paper, we propose Content Centric Networking (CCN) for emergency wireless ad hoc environments. CCN is a novel communication architecture capable to access and retrieve content by name. This new approach achieves scalability, security, and efficient network resource management in large scale disaster recovery and battlefield networks. Existing Internet CCN schemes cannot be directly applied to wireless mobile ad hoc networks due to different environments and specific limitations. Thus, we must extend the CCN architecture by introducing features and requirements especially designed for disruptive networks. We prove feasibility and performance gain of the new design via implementation and experimentation.

Physical layer security in wireless smart grid

The smart grid is characterized by the two-way flow of electric power and information. For the information flow implementation and support, several wireless communication technologies and standards are being considered. Although there is no doubt that using wireless communications offers significant benefits over wired connections, the wireless technology introduces additional vulnerability in terms of network security. This work addresses physical layer security, a topic that has been hardly investigated in the smart grid domain. To understand new types of threats, we review fundamentals of wireless communication and examine physical attack models in depth. As a promising solution to physical security, we describe a random spread-spectrum based wireless communication scheme that can achieve both fast and robust data transmission. We expect that the work presented here will advance the research on wireless smart grid security.

RFID assisted vehicle positioning in VANETs

With technological advancement, recent VANET applications such as safe driving and emergency rescue often demand high position accuracy. Unfortunately, however, conventional localization systems, e.g., GPS, hardly meet new accuracy requirements. To overcome this limitation, this paper proposes an RFID-assisted localization system. The proposed system employs the DGPS concept to improve GPS accuracy. A vehicle obtains two different position data: GPS coordinate from its own GPS receiver and accurate physical position via RFID communication. Then, it computes GPS error and shares it with neighbors to help them correct inaccurate GPS coordinates. To evaluate the proposed system, we conduct extensive experiments both on a simulator and on a real world test-bed. The simulation shows that, with the RFID-assisted localization system, vehicles can acquire accurate position both on a freeway and in an urban area. The results from the test-bed experiments demonstrate that the proposed system is feasible in the real VANET environment.

CoRoute: A new cognitive anypath vehicular routing protocol

Vehicular communications promise to bring us safer driving and better traffic control. Dedicated Short Range Communications (DSRC) and IEEE 802.11p are now well established standards for the inter-vehicle and vehicle-to-road side unit (RSU) communication. These channels, however, are of limited capacity and are not sufficient to support the broad range of services envisioned in VANETs. Thus, vehicles will utilize WiFi (802.11 a/b/g) and unlicensed ISM band to acquire more capacity. Unfortunately, the WiFi channels in urban area are already heavily subscribed by residential customers. In this paper, we propose CoVanet, a cognitive vehicular ad hoc network architecture that allows vehicles opportunistic access to WiFi channels. CoVanet is the first approach to use cognitive radios in a VANET. It differs from conventional cognitive radio strategies in that it uses unlicensed band and operates in an ad hoc, multihop mode. In CoVanet, network topology and channel environment change frequently due to high node mobility. The main contribution of this work is a Cognitive Ad hoc Vehicular Routing Protocol (CoRoute) that utilizes geographical location and sensed channel information. Simulation results demonstrate CoRoute efficiency and robustness to mobility and external interference.

Randomized channel hopping scheme for anti-jamming communication

Jamming attacks have been recently studied as wireless security threats disrupting reliable RF communication in a wireless network. By emitting noise-like signals arbitrarily on the shared wireless medium, a jammer can easily disturb the network. Countermeasures such as Frequency-Hopping Spread Spectrum enable nodes to avoid the jamming attacks by hopping over multiple channels. However, these solutions require pre-key establishment before data transmission, which in turns introduces several constraints. In order to solve the problem, this paper proposes a novel Quorum Rendezvous Channel Hopping (QRCH) scheme1. Nodes are able to hop over random channels independently, bypassing the need for pre-key establishment. Furthermore, by using a quorum system, nodes are guaranteed to meet within a bounded time to exchange pending messages. The scheme also enables nodes to transmit packets to multiple receivers simultaneously. We validate the proposed scheme via extensive simulations and present its robustness and efficiency.

CoRoute: a new cognitive anypath vehicular routing protocol

Vehicular communications promise to bring us safer driving and better traffic control. Dedicated short range communications and IEEE 802.11p are now well established standards for vehicular communications. Channels for those systems, however, are of limited capacity and are dedicated to safety applications. Thus, they are not sufficient to support the broad range of services envisioned in VANETs. It is anticipated that vehicles will utilize Wi-Fi (802.11 a/b/g) to acquire more capacity. Unfortunately, the Wi-Fi channels in urban areas are already quite heavily subscribed by residential customers. To evade the residential load, in this paper, we propose CoVanet, a cognitive vehicular ad hoc network architecture that allows vehicle radios to access the Wi-Fi channels ‘opportunistically’, finding least loaded channels. In CoVanet, network topology and channel environment change frequently because of high node mobility. The main contribution of this work is a cognitive ad hoc vehicular routing protocol (CoRoute). CoRoute is a hybrid that utilizes both geographical location and sensed channel information to establish stable, minimum delay routes to the destination. Simulation results show that CoRoute is robust to mobility and to external interference and improves packet delivery ratio on average by 70% with respect to routing without cognitive radios. Copyright

Scaling properties of delay tolerant networks with correlated motion patterns

Mobile wireless networks with intermittent connectivity, often called Delay/Disruption Tolerant Networks (DTNs), have recently received a lot of attention because of their efficiency in various application scenarios where delay is noncritical. DTN routing and transport protocols effectively overcome partial connectivity by letting the nodes carry-and-forward data. The scalability of DTN protocols is very important for protocol design and evaluation. In particular, we need models that allow us to predict the performance of DTN as a function of node mobility behavior (e.g., inter-contact times). Yet so far little work has been done to develop a unified framework that formalizes DTN performance as a function of motion behavior. In this paper, we represent DTNs as a class of wireless mobile networks with intermittent connectivity, where the inter-contact behavior of an arbitrary pair of nodes can be described by a generalized two-phase distribution (i.e., a power-law head with an exponential tail). Recent experiments have confirmed that the two-phase distribution is the most realistic model for vehicular and pedestrian scenarios, where the specific shape of the distribution depends on the degree of correlation among mobile traces. Using this DTN model, we make the following contributions. First, we extend the throughput and delay scaling results of Grossglauser and Tse (derived for exponential inter-contact time distributions) to the two-phase distribution with motion correlation. Second, we analyze the impact of finite buffer on the capacity scaling properties of DTNs, again for different correlation behaviors. Finally, we validate our analytical results with a simulation study.

Frequency quorum rendezvous for fast and resilient key establishment under jamming attack

This paper proposes a novel Frequency Quorum Rendezvous (FQR) scheme for fast and resilient pre-key establishment in anti-jamming spread spectrum techniques. While nodes hop over own frequencies during the key establishment phase, using a quorum system improves their rendezvous probability and reduces time latency.

Cognitive radio implementation in ISM bands with Microsoft SORA

Cognitive radio network research has mostly focused on licensed spectrum sensing and empty spectrum use while protecting licensed band primary users. However, the wide deployment of WiFi access points in unlicensed bands in urban areas brings difficult challenges regarding co-existence of ad hoc mobile users with residential access points. In this paper, we propose a new mobile user protocol for dynamic channel selection via channel workload estimation. The mobile node senses channel usage in unlicensed ISM band and selects the maximum residual capacity channel for own packet transmission. The new protocol is implemented on Microsofts SORA software defined radio system that enables fast prototyping. We have evaluated the performance using a Campus deployed SORA testbed. Experimental results show the efficiency of our approach in avoiding external interference.