Satoko Itaya

Demonstration of robust multi-hop wireless packet broadcasts for moving vehicles using aggregated redundancy

We demonstrate a method for improving quality of ad-hoc multihop wireless communications between moving vehicles. This method is designed to overcome problems of high packet loss and route instability common in inter-vehicular communications. We implemented the proposed method as middleware supporting real-time packet transmissions such as VoIP, and evaluated the performance in experimental tests, including a 3-vehicle test on a public road. We obtained measurement results showing maximum packet loss lower than 5 %, compared to more than 80% with existing implementations of the ad hoc routing protocols OLSR and AODV. We also showed that it is possible to support good quality VoIP broadcasts at normal traffic speeds of from 40km/h to 60 km/h on open roads.

Autonomous cooperative energy trading between prosumers for microgrid systems

A method of autonomous cooperative energy trading is proposed for prosumers in microgrid systems with renewable energy generation, storage and prosumer-to-prosumer energy exchange. The trading is based on policies and protocols for sharing and matching of energy schedules, including repayment of energy. Prosumer to Prosumer (P2P) trading mode and Proxy trading mode are described. Simulation results show that the proposed energy trading can increase the utilization of renewable energy, and reduce costs of energy purchase and energy storage.

Achieving stable operation of ad hoc wireless networks with neighbor pre-selection and synchronous route updates

We propose two methods for improving the stability of communication in ad hoc wireless networks - firstly, the selection of reliable neighbors for data relay based on monitoring signal strength variations and secondly, the synchronous update of routing tables. These methods were designed to overcome problems observed in recent large testbed experiments. We show the dramatic improvement in stability and reduction of packet error rate which was achieved when we introduced these methods to an implementation of the OLSR routing protocol. Specifically we evaluated performance in a 50-node ad hoc wireless network, and showed a reduction in the packet error rate from 12% to less than 1

Differentiated Incentive Rewarding for Social Networking Services

Our ultimate goal is to develop an information diffusion system where individuals are motivated to create content and share it with public. As our first step, in this paper, we present an incentive-rewarding mechanism for social networking services and focus particularly on changing reward assignment ratio considering different risks users perceive when uploading content with different privacy settings: public-open and friend-limited. Our learning-based simulation allowed us to observe enlargement of social networks with different rewarding ratio. The result also suggested that there is an optimal reward assignment ratio to maximize social networks.

Incentive Rewarding Method for Information Propagation in Social Networks

A problem in the social-network-based intaraction distribution is that people are less motivated to forward information when psychological forwarding cost is large. The simplest solution for this is to compensate for the cost by giving people incentive reward when they forward information. However, it is unclear that, even if we successfully propagate information over the whole social network by the incentive reward, this propagation is meaningful for the sender (original information source). Therefore, in this paper, we propose a novel incentive rewarding method where incentive reward is assigned to a forwarder only when the receiver reacts to the forwarded information. In our method, forwarders are motivated to attach their own recommendation comment when they forward information. As a result, our method can promote receivers to react the information without increasing the total amount of incentive reward, compared with the method that gives incentive reward independently of the receivers reaction.

Packet aggregation at access points for concurrent real-time interactions over wireless relay networks

We propose and demonstrate a method for improving capacity for real-time interactive communications over multi-hop wireless networks using WiFi wireless devices. The proposed method uses aggregation of packets at access points designed to avoid bottlenecks in relay traffic and maintain low end-to-end latency. We present experimental results which demonstrate that a relay node can support seven concurrent voice-over-IP (VoIP) sessions using a single 802.11 channel.

Evaluation of packet latency and fluctuation during UDP packet exchange in ad hoc wireless groups

We study latency fluctuation during UDP packet exchange in ad hoc wireless groups. We focus on wireless media access using carrier sensing multiple access with collision avoidance, specifically the 802.11 protocol. We show that there can be large intermittent fluctuations in transmission times when packet exchange is done using UDP unicast. We show how the conditions for the onset of large fluctuations can be estimated, and how these estimates can be used in the design of applications which require real-time data exchanges with low latency.

Content Propagation Analysis of E-mail Communications

We analyze email communications within a large company to reveal how email activity patterns depend on content. We characterize email contents using keywords and examine statistics of email transmissions. As a result, we are able to identify differences in network structures and propagation behaviors depending on the type of keyword.We analyze email communications within a large company to reveal how email activity patterns depend on content. We characterize email contents using keywords and examine statistics of email transmissions. As a result, we are able to identify differences in network structures and propagation behaviors depending on the type of keyword.

Experiments on Personal Opinion Expression and Consensus Building using Future Chronicle

It is an important issue to understand the mechanism of personal opinion expression and consensus building in communities. We implemented an interactive application called ldquofuture chroniclerdquo for monitoring personal opinion expression and consensus building in communities. Future chronicle produces the field of personal opinion expression from multiple users, and users can share their thoughts with each other on this field. Moreover, we can observe the growth of communities through this application. In this paper, we report our experiments using future chronicle.

Evaluation of Multi-Channel Flooding for Inter-Vehicle Communication

Flooding protocols are efficient for communications on instable network such as inter-vehicle communications because there is no necessity of complex procedures to build routes for data forwarding. In this paper, we propose a multi-channel flooding protocol using multi-interface WLAN terminals for improving robustness of communications. In simulation test, we show that packet loss rate can be reduced with parallel-redundant packet transmission using multi-channel, and transmission delay can also be reduced compared to serial-redundant packet transmission using single-channel. In experimental test, we confirm that the multi-channel flooding is also effective in real environment.