Scalability

Current Research Topics

A Smartphone-based Warning System for Rain-induced Disasters

There is currently a growing concern for climate change considering that it causes the increasing frequency of localized heavy rains. This type of rain events are difficult to detect even with existing weather forecasting systems because they tend to suddenly occur in a small area. Also, detection methods that are currently being developed are high-cost and has low scalability. Moreover, localized heavy rains impact society by causing disasters such as flash floods and landslides, which in turn causes human deaths and severe damage to properties. To reduce such catastrophes, we explore the possibility of a low-cost and scalable warning system using smartphone measurements of network signal strengths and significant weather parameters, such as pressure, humidity, and temperature. We are presuming that a small network of smartphones in an area of less than a kilometer would be able to describe the current weather condition by monitoring the environment and accordingly provide appropriate warnings in the event of a heavy rain.

SOSCast:SOS message Propagation for Locating Disaster Victims using Smartphones

During the first three days right after a disaster happens, which is also known as the "Golden 72 hours", it is important to rescue as many disaster victims as possible since the survival rate rapidly decreases when the said duration has passed. But in a large disaster, citizens suffered major disruptions in telecommunications when equipment and base stations were severely damaged. In this case, victims and rescuers are difficult to correct and send disaster information.
To treat these problem,we focus on smartphone that most of disaster victims may have. Connecting between each smartphones with wireless communications(e.g. Wi-Fi, Bluetooth), and moving them, we can propagate desaster information to other area (called Store-Carry-Forward Network). Propagating rescue call messages created by disater victims using this system, we can reach these messages to rescue team.

IPv6 Network Evaluation Testbed(IPv6NET)

Among the many challenges introduced by the IPv6 transition process to the Internet community, one of the most difficult was presented to the network operators. All of the existing production networks were forced to reconsider their inner architecture to move towards IPv6. To support network operators in this challenge, the IETF has proposed multiple IPv6 transition and coexistence technologies. Which one of these technologies is most feasible for their scenario, is still an open problem. To support network operators solve this problem, we are proposing a suite of practical evaluation methodologies, exploring various feasibility dimensions of transition technologies. The methodologies are associated with a heterogeneous IPv4 and IPv6 network testbed, which we called the IPv6 Network Evaluation Testbed (IPv6NET). In order to validate these methodologies, we have used them to analyze the feasibility of two open source transition implementations, covering multiple transition technologies. To that end, we are showing how network performance, scalability and operational capability data can be obtained, analyzed and compared.

Emulated Internet for Scalability Tests

Complexity of the physical resource assignment and numerous configurations makes it difficult for an experimenter to build an experimental network. Also, the differences of description among configuration files used on each software and hardware makes it difficult to reuse these files. In this paper, we propose the AnyBed: the experimental network building system using the logical and physical network topologies which are described in XML. Mapping these two topologies, AnyBed can build intended logical network topology on any PC clusters. We have also evaluated an implementation of AnyBed using two distinct clusters.

Overlay Network

As the Internet grows, its traditional architecture and applications have revealed some problems such as the overload on centralized servers and the existence of single points of failure. In these years, researchers are spotlighting "overlay network" as a solution against these problems. Our research focuses on QoS, security, mobility and diversity on overlay networks from both the methodological aspect and the practical aspect.

Mobile, Personal Data Offloading to Public Transportation

With the proliferation of smart mobile devices, mobile data traffic is increasing at an unprecedented rate, and the increase then weighs heavily on mobile networks. To relieve the traffic load, data offloading through WiFi and Femtocell has recently attracted considerable attention. They, however, have some difficulties to offload high- volume data objects, such as video data, because of the limitations of their transmission speeds and user mobility. This research explores offloading delay-tolerant and large data objects to public transport vehicles by using high-speed short-range wireless communication.

Seamless Mobility

With spread of wireless access technologies, users have many opportunities to connect the Internet anytime and everywhere. However, since user's movement is limited by one independent network such as cellular network and wi-fi network, user cannot freely move without considering the area. To realize seamless inter-domain mobility, we need mobility technology between heterogeneous networks. In this theme, we study seamless inter-domain handover with no interruption and quality degradation in heterogeneous networks.