Masaki Hanada

Tokyo University of Information Sciences · Information system

Recently packet scheduling algorithms such as Packetized GPS (PGPS), worst-case fair weighted fair queueing (WF²Q) and Self-Clocked Fair Queueing (SCFQ) have been proposed in order to guarantee deterministic or statistical delay bounds. These algorithms are based on generalized processor sharing (GPS) which is an ideal scheduling algorit...

In this study, we propose a Peer-to-Peer (P2P) Video-on-Demand (VoD) streaming method which adjusts the receiving rate of pieces by considering the playback deadline of the pieces to reduce interrupted playback. P2P VoD streaming methods based on BitTorrent, such as BitTorrent Streaming (BiToS) and BiToS + Immediacy and Scarcity (BIS), have been pr...

End-to-end available bandwidth estimation is very important for real-time services such as voice over internet protocol, videoconferencing and peer-to-peer streaming. Several available bandwidth estimation methods such as Pathload, IGI/PTR, pathChirp, Yaz and ASSOLO have been proposed. However, these methods have drawbacks in terms of accuracy of a...

Parallelization paradigms for effective execution in a Directed Acyclic Graph (DAG) application have been widely studied in the area of task scheduling. Schedule length can be varied depending on task assignment policies, scheduling policies, and heterogeneity in terms of each processor and each communication bandwidth in a heterogeneous system. On...

Many workflow scheduling algorithms for heterogeneous systems have been developed to satisfy multiple requirements such as minimizing schedule length while maximizing throughput. In particular, in list-based scheduling approaches, the schedule length depends on the given nodes as well as the task allocation and ordering policies. This is because th...

Edge computing can realize a data locality among a cloud and users, and it can be applied to task offloading, i.e., a part of workload on a mobile terminal is moved to an edge or a cloud system to minimize the response time with reducing energy consumption. Mobile workflow jobs have been widely used due to advance of computational power on a mobile...

Interference in ad hoc WLANs is a common occurrence as there is no centralized access point controlling device access to the wireless channel. IEEE 802.11 WLANs use carrier sense multiple access with collision avoidance (CSMA/CA) which initiates the Request to Send/Clear to Send (RTS/CTS) handshaking mechanism to solve the hidden node problem. Whil...

Satellite data has often been used to investigate damage from natural disasters (e.g., flood, drought, forest fire and volcano eruption) close to real-time. In particular, Terra/MODIS and Aqua/MODIS have been widely used for retrieving information on natural disasters and land cover changes because of their advantage of good ground resolution (maxi...

Recent task scheduling algorithms for a generalized workflow job in heterogeneous system adopt list-based scheduling. In those algorithms, the response time cannot be effectively reduced if the given workflow job is data-intensive. If the workflow job is computationally intensive, an attempt is made to assign tasks to many processors, which can lea...

Recently, Content-Centric Networking (CCN) has emerged as a new networking paradigm. The main features of CCN architecture are in-network caching and content-based routing. Cache replacement and decision policies have been discussed as important mechanisms of in-network caching in past literature. However, these policies cannot efficiently support...

In this paper, we evaluate a novel method for reducing exposed nodes in IEEE 802.11 ad hoc WLANs using asymmetric transmission ranges for RTS and CTS frames. The RTS/CTS handshake communication control mechanism used in IEEE 802.11 networks solves the hidden node problem but causes the exposed node problem. Our proposed method uses asymmetric trans...

The W-LAN Ad Hoc network tends to cause problems called 'Hidden Node' and 'Exposed Node'. RTS/CTS mechanism has been introduced to mitigate Hidden Node and most of existing researches assume that RTS and CTS are sent at the same transmission range. This paper describes a new method to improve the network throughput by adjusting the RTS transmission...

One interesting problem regarding wireless local area network (WLAN) ad-hoc networks is the effective mitigation of hidden nodes. The WLAN standard IEEE 802.11 provides request to send/clear to send (RTS/CTS) as mitigation for the hidden node problem; however, this causes the exposed node problem. The first 802.11 standard provided only two transmi...

A wireless network node with the Omni antenna tends to cause problems called "Hidden Node" and "Exposed Node". RTS/CTS mechanism has been introduced to mitigate Hidden Node and most of existing researches assume that RTS and CTS are sent at the same data rate. In this paper we have intentionally allocate different transmission rate to RTS and CTS i...

This paper proposes a new QoS management method for W-LAN network considering hidden node issue which handles the communication priority in accordance with each node's required bit rate. By the proposed method a W-LAN node requiring the higher bit rates can have more chance to send data to control QoS requirement with propriety.

In the last decades, many kinds of task execution models such as grid and cloud computing have been developed. In such distributed systems, each task is processed by respective processor in multicored computers e.g., household PCs which we can easily harness in recent years. If there is one policy to automatically decide the “best” combination and...

Multimedia applications such as music or video streaming, video teleconferencing and IP telephony are flourishing in packet-switched networks. Applications that generate such real-time data can have very diverse quality-of-service (QoS) requirements. In order to guarantee diverse QoS requirements, the combined use of a packet scheduling algorithm b...

Recently multimedia applications such as music or video streaming, video teleconferencing and IP telephony have been flourishing in packet-switched networks. Applications that generate such real-time data can have very diverse quality-of-service (QoS) requirements. In order to guarantee diverse QoS requirements, the combined use of a packet schedul...

Recently many packet scheduling algorithms based on generalized processor sharing (GPS) and earliest deadline first (EDF) have been proposed in order to guarantee deterministic or statistical delay bounds. GPS provides a minimum guaranteed service rate for each session and tight end-to-end delay bounds for leaky bucket constrained sessions. However...

Due to recent advances in multimedia technology, a real-time capability is needed to a certain extent even in information systems, in addition to control systems. In general, information systems are classified as soft real-time systems, which keep operating even if a deadline is missed. In soft real-time systems, it is more important to provide sta...