Chao-Hsien Lee

A Novel SIP-Based Route Optimization for Network Mobility

With the provision of various wireless services, e.g., third-generation (3G) and wireless local area network (WLAN), more and more people request to access the Internet anywhere at anytime. For example, people want to check their e-mails on the bus or watch online news while traveling in the train. For this purpose, the Internet Engineering Task Force (IETF) proposed the concept of network mobility, i.e., a set of users move as a unit. We motivate the network mobility problem by considering the state-of-the-art scenario of the network mobility (NEMO) basic support protocol that is extended from the Mobile IPv6 (MIPv6). In order to avoid the same problems suffered by MIPv6, a new session initiation protocol (SIP)-based network mobility management scheme called SIP-NEMO is designed and proposed in this paper. The proposed SIP-NEMO not only copes with the movement of a mobile network but also achieves the route optimization between two SIP clients without too many signaling messages over wireless links, even if the mobile network is nested. In this paper, we also analytically compute and simulate the performance of SIP-NEMO with the NEMO basic support protocol proposed by the IETF

Multihomed SIP-Based Network Mobility Using IEEE 802.21 Media Independent Handover

When a group of users or devices move together, network mobility resolves how to manage the location transition of the whole members. Two kinds of solutions have been proposed at different layers. Network Mobility (NEMO) Basic Support Protocol (BSP) is the extension of Mobile IPv6 at the network layer. On the other hand, Session Initiation Protocol (SIP) based network mobility (SIP-NEMO) is defined at the application layer. However, on the perspective of ubiquitous network environment, a mobile router requires to possess several egress paths to the Internet for providing uninterrupted services and aggregating good enough bandwidth. Multihoming in network mobility support becomes one urgent and nessceary issue. Since Mobile IPv6 based NEMO BSP, called MIPv6-NEMO hereafter for convenience, uses a bi-directional tunnel between home agent and mobile router, Multihomed MIPv6-NEMO would suffer and deepen header overhead and suboptimal routing. In the past, we have proposed SIP-NEMO to achieve route optimization. In this paper, we investigate and analyze how to extend the current SIP-NEMO to support multihoming further. The proposed multihomed SIPNEMO is simulated in different cases and integrated with the IEEE 802.21 Media Independent Handover (MIH) standard. According to the simulation result, the SIP-NEMO can keep route optimization no matter which multihomed case is configured.

The K-hop Cooperative Video Streaming Protocol Using H.264/SVC Over the Hybrid Vehicular Networks

When a number of persons, e.g., a family or a group of friends, drive their vehicles for a trip together, they can form a fleet of vehicles and share their network resources during their trip. Let one member want to watch a video from the Internet. He may not have high resolution or video quality due to his limited 3G/3.5G bandwidth to the Internet. The cooperative video streaming scenario allows the requested member to ask other members of the same fleet to download video cooperatively. In other words, other members can help to download parts of the video from the Internet and then forward video data to the requested member hop by hop through the ad-hoc network. This work proposes the k-hop cooperative video streaming protocol using H.264/SVC over the hybrid vehicular networks which consist of 3G/3.5G cellular network and Dedicated Short-Range Communications (DSRC) ad-hoc network. In order to smooth video playback over the DSRC-based ad-hoc network, this work proposes: (1) one streaming task assignment scheme that schedules the streaming task to each member over the dynamic vehicular networks, and (2) packet forwarding strategies that decide the forwarding sequence of the buffered video data to the requested member hop by hop. Finally, we utilize the network simulator version 2 (NS2) to simulate the proposed protocol. Based on the simulation results, the proposed scheme can estimate the assignment interval adaptively and the playback priority first (PPF) strategy has the best performance for the k-hop video forwarding over the hybrid vehicular networks.

Location-aware multimedia proxy handoff over the IPv6 mobile network environment

In a server-proxy-client 3-tier networking architecture that is executed in the mobile network, proxies should be dynamically assigned to serve mobile hosts according to geographical dependency and the network situation. The goal of proxy handoff is to allow a mobile host still can receive packets from the corresponding server while its serving proxy is switched from the current one to another one. Once proxy handoff occurs, a proper proxy should be selected based on the load balance concern and the network situation concern. In this paper, a 3-tier Multimedia Mobile Transmission Platform, called MMTP, is proposed to solve the proxy handoff problem in the IPv6-based mobile network. A proxy handoff scheme based on the application-layer anycasting technique is proposed in MMTP. A proper proxy is selected from a number of candidate proxies by using the application-layer anycast. An experimental environment based on MMTP is also built to analyze the performance metrics of MMTP, including load balance among proxies and handoff latency.

Energy-Aware Group LBS Using D2D Offloading and M2M-Based Mobile Proxy Handoff Mechanisms Over the Mobile Converged Networks

Since smart phones are always equipped with both cellular and Wi-Fi interfaces, this paper exploits the feasibility of the Wi-Fi-based device-to-device offloading mechanism to reduce cellular traffic. In our group location-based service (LBS) scenario, a group of users travel outdoors together and utilize their smart phones to form a mobile converged network, which is composed of cellular and Wi-Fi networks, to download and share the neighboring LBS data. Due to the wide-range coverage of the cellular network and the keeping-moving characteristic of users, one of these smart phones is selected to play the role of mobile proxy to download the shared LBS data using its cellular interface and then disseminate to other members using multicast over the Wi-Fi network, in which one adaptive FEC mechanism is adopted to tackle the packet loss situation. Besides, a user-transparent machine-to-machine-based mobile proxy handoff mechanism is devised such that each smart phone can play the role of mobile proxy alternately to evenly consume each smart phones power and thus extend the service time of the group LBS scenario. That is, the proposed offloading mechanism not only offloads the cellular network traffic but also reduces the power consumption.

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.

Multiple router management for SIP-based Network Mobility

Network mobility is proposed to let a mobile network change its point of attachment and still keep all nodes attached to the mobile network globally reachable. However, due to finite bandwidth, limited signaling coverage and frequent link failure, a mobile network needs multihoming to access the Internet simultaneously on the perspective of performance and reliability. In this paper, we extends our previous work, i.e., SIP-based Network Mobility (SIP-NEMO), to support multihoming. A mobile network is considered to possess more than one egress gateway. The proposed multihomed SIP-NEMO provides dynamic synchronization among different egress gateways. Once an egress gateway joins or leaves the mobile network, the multihomed SIP-NEMO can establish or switch sessions on another alternative egress gateway. According to the simulation results, the proposed multihomed SIP-NEMO can achieve route optimization for data transmission.

A power efficient pedestrian touring scheme based on sensor-assisted positioning and prioritized caching for smart mobile devices

Location-based service (LBS) is a general class of add-on network services using the information on the geographical positions of users. With the significant growth of portable and mobile devices, integrating LBS into new smart devices, i.e., smart phone or tablet PC, becomes the main trend of the next-generation consumer electronic services. Due to limited power lifetime, this paper concentrates on the power saving issue of a pedestrian touring service using smart mobile devices. Regarding the positioning accuracy and neighboring points of interests (POIs), a power efficient touring scheme (PETS) is proposed to dynamically adjust the GPS sampling rate with the help of embedded sensors in smart mobile devices to keep enough positioning accuracy and low power consumption. At the same time, the proposed PETS prioritizes which POIs should be pre-downloaded and cached based on the relationship between the current geo-location of a pedestrian and neighboring POIs for reducing unnecessary transmission power. Based on our performance results, the PETS can save about 45% power consumption.