MSPlayer: Multi-Source and multi-Path LeverAged YoutubER

Online video streaming through mobile devices has become extremely popular nowadays. YouTube, for example, reported that the percentage of its traffic streaming to mobile devices has soared from 6% to more than 40% over the past two years. Moreover, people are constantly seeking to stream high quality video for better experience while often suffering from limited bandwidth. Thanks to the rapid deployment of content delivery networks (CDNs), popular videos are now replicated at different sites, and users can stream videos from close-by locations with low latencies. As mobile devices nowadays are equipped with multiple wireless interfaces (e.g., WiFi and 3G/4G), aggregating bandwidth for high definition video streaming has become possible. We propose a client-based video streaming solution, MSPlayer, that takes advantage of multiple video sources as well as multiple network paths through different interfaces. MSPlayer reduces start-up latency and provides high quality video streaming and robust data transport in mobile scenarios. We experimentally demonstrate our solution on a testbed and through the YouTube video service.Comment: accepted to ACM CoNEXT'1

On Distinguishing Relative Locations with Busy Tones for Wireless Sensor Networks

[[abstract]]Bounding-box mechanism is a well known low-cost localization approach for wireless sensor networks. However, the bounding-box location information can not distinguish the relative locations of neighboring sensors, hence leading to a poor performance for some applications such as location-aware routing. This paper proposes a Distinguishing Relative Locations (DRL) mechanism which uses a mobile anchor to broadcast tones and beacons aiming at distinguishing the relative locations of any two neighboring nodes. Experimental study reveals that the proposed DRL mechanism effectively distinguishes relative locations of any two neighboring nodes and hence significantly improves the performance of location-aware routing in wireless sensor networks (WSNs).[[conferencetype]]國際[[conferencedate]]20100523~20100527[[iscallforpapers]]Y[[conferencelocation]]Cape Town, South Afric

TCWTP: Time-Constrained Weighted Targets Patrolling Mechanism in Wireless Mobile Sensor Networks

[[abstract]]Target coverage problems have received much attention in recent years. In a large monitoring environment where targets are distributed over an entire monitored region, deploying static sensors leads to high hardware costs because a high number of sensors may be required to achieve network connectivity. This paper considers the target-patrol issue where a set of mobile data mules (DMs) are dispatched to efficiently patrol the given targets under a predefined time constraint. The targets are assigned weights indicating their importance, where more important targets should be visited more frequently by the DMs. Accordingly, this paper proposes a time-constrained weighted targets patrolling (TCWTP) algorithm for locally constructing efficient patrol paths, thereby ensuring globally stable intervals between visits to all target points. A performance analysis revealed that the proposed TCWTP mechanism outperforms existing works in terms of the average interval between visits, quality of monitoring satisfaction ratio, and monitoring fairness ratio.[[notice]]補正完畢[[booktype]]紙

Some studies and lessons learned from ad hoc learning

[[abstract]]This work proposes concepts, designs, experiences and lessons learned from some studies of ad hoc learning supported by wireless and mobile technologies. The ad hoc learning activity model supports learners communicating with or obtaining help from classmates or teacher, interacting with environment, and accessing teaching material from mobile device or Internet. Example scenarios with prototype systems for ad hoc learning are presented. Preliminary experimental and trial studies are conducted with these example scenarios in elementary and high school students. The potential impacts, limitations, and lessons learned in this study are also discussed from both the educational and technological points of view. Learning in a lively, vivid, and new learning environment, students are motivated with interests for learning the target domains. Ad hoc learning potentially extends the scope of learning activities and with more flexibility than in traditional school curriculum.[[conferencetype]]國際[[conferencedate]]20050627~20050630[[booktype]]紙本[[conferencelocation]]Hsinchu, Taiwa

Patrolling Mechanisms for Disconnected Targets in Wireless Mobile Data Mules Networks

[[abstract]]This paper considers the target patrolling problem which asks a set of mobile data mules to efficiently patrol a set of given targets. Since the time interval (also referred to visiting interval) for consecutively visiting to each target reflects the monitoring quality of this target, the goal of this research is to minimize the maximal visiting interval. This paper firstly proposes a basic algorithm, called Basic (B-TCTP), which aims at constructing an efficient patrolling route for a number of given data mules such that the visiting intervals of all target points can be minimized. For the scenario containing weighted target points, a Weighted-TCTP (W-TCTP) algorithm is further proposed to satisfy the demand that targets with higher weights have higher data collection frequencies. By considering the energy constraint of each data mule, this paper additionally proposes a RW-TCTP algorithm which treats energy recharge station as a weighted target and arranges the data mules visiting the recharge station before exhausting their energies. Performance study demonstrates that the proposed algorithms outperform existing approaches in terms of visiting intervals of the given targets and length of patrolling path.[[conferencetype]]國際[[conferencedate]]20110913~20110916[[conferencelocation]]Taiwa

The k-Barrier Coverage Mechanism in Wireless Visual Sensor Networks

[[abstract]]Wireless Visual Sensor Networks (WVSNs) consist of a set of camera sensor nodes each of which equips with a camera and is capable of communicating with the other camera sensors within a specific distance range. As an extension of wireless sensor networks (WSNs), the WVSNs can provide richer information such as image and picture during executing targets monitoring and tracking tasks. Since the sensing area of each camera sensor is fan-shaped, existing barrier-coverage algorithms developed for WSNs cannot be applied to the WVSNs. This paper is considering to address the k-barrier coverage problems in WVSNs and to propose a barrier-coverage approach aiming at finding a maximal number of distinct defense curves with each of which consists of as few camera sensors as possible but still guarantees k-barrier coverage. Compared with the related work, experimental study reveals that the proposed k-barrier coverage mechanism constructs more defense curves than the k-barrier coverage and the number of camera sensors participating in each defense curve is smaller.[[conferencetype]]國際[[conferencedate]]20120401~2012040

Path Guiding Mechanisms for a Mobile Anchor Improving or Balancing Location Accuracies of Static Sensors in WSNs

[[abstract]]Location information is of utmost importance for most applications in wireless sensor networks. Recent localization schemes have been categorized into range and range-free based techniques. Obvious inclination is towards range free algorithms since they do not rely on special hardware that would be required in range based algorithms. In the most proposed range-free algorithms, nodes estimate their location using the geometric constraints imposed by the location of a mobile anchor. However, there is no discussion on how the mobile anchor moves so that the maximal location accuracies of all sensor nodes can be obtained with the constraint of energy consumption of a mobile anchor. This paper assumes that traditional range-free algorithms have been executed for a certain time period and the deployed sensors are with different location accuracies. We propose path guiding mechanisms that sensor nodes cooperatively guide the mobile anchor moving along an efficient path which can maximize the improvement of location accuracies or minimize the accuracy differences for all sensor nodes in a given WSN. Experimental study reveals that the proposed path guiding mechanisms effectively guide the mobile anchor moving along the efficient path and thereby saves time and energy consumptions for improving or balancing the location accuracies of all sensor nodes.[[conferencetype]]國際[[conferencedate]]20081014~20081017[[iscallforpapers]]Y[[conferencelocation]]Montreal, Canad

PCF: on exploiting spatial reuse and power conservation opportunities with power control and fairness mechanism for 802.11 WLAN

[[abstract]]Exploiting spatial reuse opportunities allows more parallel transmissions and improve the throughput of wireless networks. Power control is one of the major mechanisms used to exploit both spatial reuse and power conservation opportunities. Increasing the transmitting power prevents the receiver from interference but consume power and create additional interference to other communicating nodes. On the contrary, reducing the transmitting power reduces the interference to other communicating pairs and save sender's power consumption, but result a lower SNR (signal to noise ratio) at receiver side. This article presents power control MAC protocol to exploit the spatial reuse and power conservation opportunities for 802.11 wireless LAN. The proposed protocol evaluates the interference and adopts power control mechanism on both sender and receiver sides, trying to allow more communications proceeding simultaneously. In addition, a fairness control mechanism is also proposed to reduce the average communication delay and alleviate the packet lost phenomenon. Performance results reveal that the proposed protocol improves the throughput and power consumption of WLAN while the fairness among communicating pairs can be maintained.[[conferencetype]]國際[[conferencedate]]20050306~20050308[[booktype]]紙

TARP: a traffic-aware restructuring protocol for Bluetooth radio networks

[[abstract]]Bluetooth is a well-known wireless technology designed for wireless personal area networks (WPAN). The Bluetooth device randomly searches and connects with other devices using the inquiry/inquiry scan and the page/page scan operations, resulting an uncontrolled scatternet topology. The unpredictable scatternet topology usually raises the problem of redundant traffic and causes inefficient communications. A traffic-aware restructuring protocol (TARP) is presented for partially restructuring a piconet or neighboring piconets by applying role switch mechanism. According to the recent routes and their traffic pattern, the TARP adjusts piconet structure by selecting the proper master from devices of a piconet and switches proper devices of neighboring piconets to reduce the route length and thus improve the power and bandwidth consumptions and transmission delay. Performance results show that TARP significantly improves network performance by reducing traffic load and power consumptions[[conferencetype]]國際[[conferencedate]]20050911~20050914[[booktype]]紙本[[conferencelocation]]Berlin, German