Chia-Ching Yang

A Collision Pre-Warning Algorithm Based on V2V Communication

The WAVE (IEEE 1609) standard and vehicular technology creates a new opportunity for telematics service. Safety is one of the top issues of telematics service. In this paper, we focus on the safety application and WAVE communication to provide proactive safety which can alert drivers before the accident occurs. An algorithm named Collision Pre-Warning Algorithm (CPWA) was proposed to tackle the aforementioned issues. In CPWA, vehicles broadcast Relationship Information (RI) to neighboring vehicles periodically. Each vehicle calculates whether potential collision may happen or not upon the RI messages that were received. After calculation, the CPWA sends warning messages to drivers if the collision will occur before several seconds. The results show that CPWA has good performance and can always alert drivers suitably.

A Centralized Traffic Control Mechanism for Evacuation of Emergency Vehicles Using the DSRC Protocol

Emergency service vehicles need safety and fluent paths to save time. In this paper, a centralized traffic control mechanism is proposed for the evacuation of vehicles that drive toward the dedicated path of the emergency vehicles (EV), e.g. Ambulance, Fire Engines, Police Cars, etc, using the Dedicated Short Range Communications (DSRC) protocol. In our proposed mechanism, a centralized server is used to monitor and control all traffic information to support real time traffic information and services for emergency vehicles, and the centralized server also calculates the shortest path for emergency vehicles to pass by. If the approaching information of emergency vehicles is not announced in advance to other vehicles that will obstruct the approaching path of emergency vehicles, it will cause the traffic muddle on the road and increase the delayed time for emergency vehicles. Thus, we also propose a data dissemination scheme to transmit the warning messages to other vehicles that will obstruct the approaching road of emergency vehicles. In our experiment, we will exhibit the performance of our proposed system.

A Bandwidth Aggregation Scheme for Member-Based Cooperative Networking over the Hybrid VANET

In this paper, we proposed a K-hop bandwidth aggregation scheme for member-based cooperative video streaming over the hybrid vehicular networks consisting of DSRC ad hoc network and 3G/3.5G cellular network. Each member in the same group is known to each other, e.g., they may be a family or a group of friends driving their sedans and they set out from the same position along the same path to the same destination during the journey. When a member in a vehicle wants to watch video during traveling, he will request video through 3G/3.5G network. However, the limited bandwidth of the 3G/3.5G network is not enough to support higher resolution or higher quality of downloading video. In order to enhance the quality of video playback, the member, who is called requester, in one vehicle can ask members, who are called helpers, of the same group in other vehicles to cooperatively download video through their 3G/3.5G networks and then forward their downloaded video to the requester through the DSRC ad hoc network. In order to select suitable members as helpers to download and forward the video and make video streaming more effectively to the requester over the DSRC Ad hoc vehicular network, how to select suitable helpers to forward the downloaded video hop-by-hop back to the requester needs to be resolved. In this paper, we proposed a K-hop bandwidth aggregation scheme to tackle the aforementioned problem. The performance results show that our proposed scheme can get better quality video than cooperative video streaming schemes without the deliberately designed K-hop bandwidth aggregation mechanism.

An Effective Channel Utilization Scheme for IEEE 1609.4 Protocol

In this paper, the effective channel usage is investigated in IEEE 802.11p WAVE (Wireless Access in Vehicular Environments) communication protocol. IEEE P1609 family is the standard for wireless access in vehicular environments based on IEEE 802.11p, and the WAVE architecture with multi-channel operation over CCH (Control Channel) and SCH (Service Channel) are defined in the MAC layer. However, there is only one channel (CCH or SCH) that is used to transmit data and the other one will be wasted during service access. Thus, an Exploitable Node-Assisted WBSS (WAVE Basic Service Set) Broadcasting Mechanism is proposed to utilize empty channels and idle nodes for transmitting WBSS to newly coming nodes. The proposed mechanism can reduce the delay time for getting service information from RSU when vehicles are traveling into the broadcasting coverage of RSU. The Sync interval is fixed in the original scheme for guarantee OBU getting WBSS in a specific period. But, this feature may cause bandwidth wastage during service access. Therefore, a Dynamic Sync Interval Scheme is proposed to improve the channel usage. In this paper, we exhibit merits and performance results of our proposed schemes.

Mobility Management for Video Streaming on Heterogeneous Networks

This article discusses how ubiquitous video streaming platform can let people enjoy continuous multimedia services at any time, in any location, and with any computing device. There are several technical challenges to be met in the process of achieving this goal. These challenges entail developing sophisticated session handoff control, session descriptions, communication signaling, and adaptive video streaming, among other factors.

Network-Aware Multimedia Streaming using the Kalman Filter Over the Wired/Wireless/3G Networks

In order to adapt the quality of videos streamed over a time-varying bandwidth channel, a network-aware bandwidth management and rate control are required. This paper proposes the well-designed bandwidth estimation and active buffer control for streaming H.264 FGS videos over heterogeneous wired/ wireless/3G networks. According to the information of measured packet round-trip-time, loss-rate and delay jitter, an improved Kalman filter is proposed to predict the throughput recursively, and determine the transmission rate in consideration of buffer fullness of a decoder. The optimal parameters of the Kalman filter, e.g., transition matrix and error covariance, can be initialized, converged and adapted to the current network, even when the session handoff occurs. In our real experiments, distinct network traffic models are simulated, and corresponding estimation results w.r.t. network information are also exhibited.

An SVC-MDC video coding scheme using the multi-core parallel programming paradigm for P2P video streaming

In this paper, we propose a COmbined SVC-MDC (Scalable Video Coding & Multiple Description Coding) video coding scheme using the multi-core parallel programming paradigm for P2P video streaming, which is denoted Co-SVC-MDC. To date, P2P video streaming applications are widely popular and emphasized, e.g., PPstream and PPlive, because of higher transmission speed and data availability. However, in the heterogeneous P2P network environment, users are able to utilize PDA, notebook or desktop computer through distinct network interfaces to get on-demand videos ubiquitously. To provide distinct spatial-resolution/fidelity videos and flexible video transmission (playback) over P2P networks, a brand new coding architecture needs to be devised. In the proposed Co-SVC-MDC coding scheme, distinct MDC descriptions contain distinct portions of raw video frames, and each raw frame can be compressed as base layer and SVC enhancement layers. In our experiments, a real implementation of Co-SVC-MDC is exhibited and corresponding performances, e.g., PSNR and decoding speeds, are compared with original SVC in distinct congestion-level P2P networks.

K-Hop Packet Forwarding Schemes for Cooperative Video Streaming over Vehicular Networks

When a passenger in a vehicle wants to watch video during movement, he may request video through cellular network, e.g., 3G or 3.5G network. However, due to the characteristics of vehicular networks, the limited bandwidth of 3G/3.5G network is not enough to support high resolution or high video quality. In order to improve the quality of video playback, this vehicle, which is defined as requester in this paper, may try to ask other members of the same fleet to download video cooperatively. In other words, other members would download parts of requested video through their 3G/3.5G network individually and then forward video data hop by hop to the requester using the DSRC ad-hoc network. In order to smooth the DSRC ad-hoc network, we propose and discuss two k-hop packet forwarding schemes for the aforementioned cooperative video streaming over vehicular networks in this paper. Each intermediary node of the forwarding route must decide how to deliver buffered video data through the limited DSRC network. Finally, the NS2 simulation tool is adopted to evaluate the proposed schemes. Based on the simulation results, the Playback Priority First (PPF) scheme is performed better than the First-In First-Out (FIFO) scheme.

Co-SVC-MDC-Based Cooperative Video Streaming Over Vehicular Networks

When a vehicle requests a video streaming service from the Internet, it may not have enough bandwidth to receive good video quality. In order to resolve this problem, the vehicle is proposed to ask neighboring vehicles to help the video download process using a short-range wireless technique, i.e. Dedicated Short Range Communications (DSRCs). In this paper, this scenario is called cooperative streaming over vehicular networks. Since the topology of vehicular networks changes over time rapidly, three critical issues in the moving-vehicle-based cooperative streaming are: (i) how to form a cooperative group dynamically, (ii) how to schedule neighboring vehicles to help the video download process and (iii) how to estimate the possible change of network conditions. We propose corresponding control schemes to tackle the aforementioned issues in this paper. From the simulation results, we can find that different scheduling schemes are adaptive to different scenarios, and the proposed dynamic group formation scheme has better performance than that of periodic group formation scheme.

A Cooperative Video Streaming System over the Integrated Cellular and DSRC Networks

Due to the advance of wireless and mobile technologies, vehicular networks are widely discussed in recent years. When a vehicle requests a video stream from the Internet using the cellular network, i.e., 3G or 3.5G network, it may not have enough bandwidth to receive good quality of video. In order to resolve this problem, the vehicle can ask neighboring vehicles for the help of downloading the video stream. This scenario is called cooperative streaming in vehicular communications. The vehicle can communicate with neighboring vehicles using a short-range wireless technique, e.g., Dedicated Short Range Communications (DSRC). Since the topology of vehicle networks changes rapidly, two critical issues in the moving vehicle-based cooperative streaming are (1) how to form a cooperative group dynamically and (2) how to schedule neighboring vehicles to help the video downloading process. The simulation results reveal that the improvement of video quality is proportional to (1) high traffic flow, (2) high probability of willingness to share bandwidth and (3) low relative speed.