Chien Ming Chou

A Feasibility Study on Vehicle-to-Infrastructure Communication: WiFi vs. WiMAX

Vehicular Network is becoming increasingly popular in recent years, in which vehicles constitute a wireless mobile network. Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) are two different modes of communication in a vehicular network. Some measurement studies have previously been undertaken to understand the feasibility of using WiFi for V2V and V2I communication. Recently WiMAX is emerging as one of the possible candidates for next generation mobile networks. In this work, we set out to understand the feasibility of using WiMAX for V2I communication as compared to the use of WiFi. Due to the hardware limitation, we focus on a static setting in urban environment. Our initial measurement studies show that while WiMAX can offer a longer communication range than WiFi, its latency can be significantly larger than that of WiFi at a short distance (e.g. less than 100m). In addition, we show the setting of frame size has a strong impact on the performance of WiMAX.

An Incentive-Based Framework for Vehicle-Based Mobile Sensing☆

Mobile surveillance has been recently proposed as a replacement for traditional road-side surveillance system. One important aspect of a mobile surveillance system is to decide what are the events of interest. In this work, we adopt the concept of participatory sensing for mobile surveillance by involving a human into the loop of data collection. We introduce a virtual credit based mechanism to motivate the participants to collect data and share their bandwidth. Finally, we use a large-scale real-world vehicle trace to evaluate the feasibility of our proposed framework.

On the Feasibility of Using 802.11p for Communication of Electronic Toll Collection Systems

In an 802.11p (so-called DSRC) network, the WSMP protocol is used for the communication between OBU and RSU. Unlike a wired network, an 802.11p wireless network is prone to fading, shadowing and interferences, which might result in high error rates. However, there is no reliability mechanism embedded in the WSMP protocol, which can become an important issue for mission-critical ITS applications such as ETC (Electronic Toll Collection). In this work, we develop a protocol on top of WSMP to build a reliable session for the message exchanges between RSU and OBU. Our protocol uses a timer-based mechanism for the message retransmission in the case of message losses. In this paper, we first describe the design of our session protocol. We then discuss the implementation of our protocol using the ITRI WAVE box and evaluate its effectiveness on real roads.

Using Vehicular Sensor Networks for Mobile Surveillance

Mobile surveillance has been recently proposed as a replacement for traditional road-side surveillance system. One important aspect of a mobile surveillance system is to decide what the events of interest are. In this work, we adopt the concept of participatory sensing for mobile surveillance by involving a human into the loop of data collection. We introduce a virtual credit based mechanism to motivate the participants to collect data and share their bandwidth. Finally, we use a large-scale real- world vehicle trace to evaluate the feasibility of our proposed framework.

Using virtual credits to provide incentives for vehicle communication

Participatory sensing has been recently proposed as a replacement for traditional mobile sensing system. In this work, we adopt the concept of participatory sensing for mobile surveillance by involving a human into the loop of data collection. Furthermore, we introduce a virtual credit based mechanism to motivate the participants to collect data and share their bandwidth. We perform an analysis of different parameters which might affect the performance of such a system.

The effect of 802.11a on DSRC for ETC communication

There are increasing interest recently in using 802.11p for ETC (Electronic Toll Collection) communication. However, there are two potential problems for using 802.11p for mission-critical applications like ETC. First, a 802.11p wireless network is prone to fading, shadowing, and interferences, which might result in packet losses. But the WSMP protocol in 802.11p standard does not provide any reliability mechanism. Second, since the frequency bands used by 802.11a and 802.11p are relatively close, it is possible that any 802.11a-based devices could potentially interfere the 802.11p traffic and disrupt the service. We previously proposed a simple session-layer protocol to improve the reliability of WSMP for ETC communication. In this work, we focus on investigating the effect of on-board 802.11a devices on ETC communication. We first demonstrate the possibility of that 802.11a could potentially interfere 802.11p traffic through theory and real-world experiments. Then, with extensive simulations, we discuss how on-board 802.11a devices could degrade ETC services in different scenarios.

Localized data dissemination in vehicular sensing networks

A vehicular sensing network (VSN) is a type of wireless sensor network that empowers legacy resource-constrained WSNs by taking advantage of the rich network resources (e.g., the battery life, storage capability, and mobility) of vehicles. In this paper, we posit that the sensed data in VSNs is generally local in nature and propose a simple yet effective scheme, called To-and-Fro (TAF), for localized data dissemination. Unlike conventional wireless networks and sensing systems, the TAF scheme operates in an opportunistic manner and does not need a network infrastructure. More precisely, the scheme always forwards messages to passing vehicles if they are moving in the opposite direction. Using simulations of both synthetic and realistic network scenarios, we demonstrate that the proposed scheme is simple, practical, and effective for localized data dissemination in vehicular sensing networks. Moreover, the scheme is easy to deploy, as long as each vehicle in the network can access GPS information.

Avoiding Biased-Feeding in the Scheduling of Collaborative Multipath TCP

Smartphones have become the major communication and portable computing devices that access the Internet through Wi-Fi or mobile networks. Unfortunately, users without a mobile data subscription can only access the Internet at limited locations, such as hotspots. In this paper, we propose a collaborative bandwidth sharing protocol (CBSP) built on top of MultiPath TCP (MPTCP). CBSP enables users to buy bandwidth on demand from neighbors (called Helpers) and uses virtual interfaces to bind the subflows of MPTCP to avoid modifying the implementation of MPTCP. However, although MPTCP provides the required multi-homing functionality for bandwidth sharing, the current packet scheduling in collaborative MPTCP (e.g., Co-MPTCP) leads to the so-called biased-feeding problem. In this problem, the fastest link might always be selected to send packets whenever it has available cwnd, which results in other links not being fully utilized. In this work, we set out to design an algorithm, called Scheduled Window-based Transmission Control (SWTC), to improve the performance of packet scheduling in MPTCP, and we perform extensive simulations to evaluate its performance.

Collaborative bandwidth sharing for resilient communication during a disaster

Given peoples increasing dependence on communication networks, vulnerabilities of communication networks and the Internet can significantly impact our lives. These networks and services are susceptible to accidents or natural disasters that can disrupt service and compromised the network infrastructure. In the face of these disasters, the need for greater resilience for the Internet has attracted the attention of researchers. In this work, we propose an architecture that allows a disconnected smart-phone in a disaster situation to utilize the Internet connections of neighboring smart-phones. We evaluate the performance of our protocol by comparing it with the Concurrent Multipath Transfer SCTP (CMT-SCTP), and the results show that our protocol can achieve similar or better performance.

Effects of Preferred Routes and Destinations on the Performance of Vehicular Network

Vehicular Ad-Hoc Networks (VANET), in which vehicles constitute the mobile nodes in the network, have attracted increasing interest in both academia and industry. However, due to the prohibitive cost of deploying and implementing such a system in the real world, most of the related research relies on simulations for evaluation purposes. A key component for VANET simulations is a realistic vehicular mobility model, as this ensures that the conclusions drawn from simulation experiments will carry through to the real deployments. Node mobility in a vehicular network is strongly affected by the driving behavior such as route choices. While route choice models have been extensively studied in the transportation community, as far as we know, the effects of preferred route and destination on vehicular network simulations have not been discussed much in the networking literature. In this work, we set out to understand the effect of route choices on vehicular network simulation. We also discuss how different destination selection models affect two practical ITS application scenarios: traffic monitoring and event broadcasting. We conclude that selecting a sufficient level of detail in the simulations, such as modeling of route choices, is critical for evaluating VANET protocol design.