Daiki Nobayashi

Multiple Station Aggregation Procedure for Radio-On-Demand WLANs

With the rapid growth in Internet network infrastructure, there is an urgent need to deploy energy-efficient networking technology. In particular, there is a need for energy-efficient wireless local area networks (WLANs), which are widely used due to their ease of deployment and low installation costs. To realize this, radio-on-demand (ROD) have been proposed. Access points (APs) in ROD are equipped with wake-up receivers that change their status to sleep or active mode based on the network traffic distribution. This study proposes a station aggregation scheme targeting multiple stations (STAs) in ROD. In this scheme, APs cooperate with each other and aggregate their STAs based on their utilization. Simulation results demonstrate the effectiveness of the scheme in terms of power saving and load balancing in ROD networks.

Power saving scheme with low-utilization station aggregation for Radio-On-Demand Networks

There has been widespread deployment of IEEE 802.11 wireless local area networks (LANs) because of high demand from mobile terminals, such as iPod and Android terminals. With the increasing energy consumption of the wireless LANs, the development of power saving technologies incorporated into the wireless LANs have become important. In wireless LANs, access points (APs) continuously consume the power regardless of the communication. Therefore, we have proposed the Radio-On-Demand (ROD) wireless LAN, which provides power saving schemes on the basis of the utilization of wireless LANs. In this study, we particularly focus on the power saving scheme of the APs, and propose the decentralized association management of ROD wireless LANs. In our scheme, an AP assigns associated stations (STAs) to new APs before switching to sleep mode. Simulation results show that the proposed scheme can realize sufficient power saving.

Development of Single Sign-On System with Hardware Token and Key Management Server

With the growth of the Internet, various types of services, such as World Wide Web (WWW), file transfer protocol (FTP), remote login, etc., are widely expanded. Consequently, it is difficult for users to manage all the authentication information, e.g., user ID/Password pairs, keys, and certificates, since the authentication information has been increased to use those services. Therefore, single sign-on (SSO) system, which makes all the services available for a user by only one-time authentication, has been developed. However, existing systems cannot provide all the SSO services for any kinds of services on the Internet even if the service provider deploys the SSO server. Therefore, in this paper, we propose a new SSO system with hardware token and key management server to improve the safety and the convenience. Furthermore, we implement the proposed system, and show its effectiveness through evaluation. In addition, adding any functions for this system provide various conveniences to us. As one example, we add high trust connection function for a Web server, and show its the effectiveness through evaluation by implementing it.

Performance Evaluation of Multi-Rate Communication in Wireless LANs

In IEEE 802.11a/b/g wireless LAN, STAs (Stations) can select an appropriate transmission rate based upon the received signal strength in order to achieve high throughput. In such a multi-rate environment, however, the total throughput is degraded if an AP (access point) is shared by STAs at both high and low transmission rates simultaneously. This problem is identified as the performance anomaly problem in only IEEE 802.11b [1], and we closely examine it under the IEEE 802.11a multi-rate environment. Although earlier studies have assumed that this performance anomaly always occurs, we show that it does not occur under a certain environment. First, we describe the mechanism of the performance anomaly, then illustrate the condition under which the performance anomaly does not occur. Finally, we show, through simulation results, the condition under which a performance anomaly may and may not occur in a multi-rate environment.

Performance Evaluation of Power Saving Scheme for Wireless LAN with Station Aggregation

The widespread deployment of wireless LANs (WLANs) has increased the importance of developing power-saving technologies. We have been involved in the research and development of Radio-On-Demand Networks (ROD) that reduce energy consumption in the operation of WLANs. In this paper, we evaluate the effectiveness of a power-saving scheme with that uses station aggregation for ROD WLANs by simulations. The simulation results show that our proposed scheme can contribute in reducing the power consumption of access points (APs).

On demand routing scheme for real-spatial information based group communication

Widespread high-performance mobile stations and wireless communication technologies make it possible to enjoy various network services anywhere at any time. In particular, social network services (SNSs) provide a wide variety of communication among users. We aim to achieve real-space communication that directly integrates information exchange and real-space activity in our daily lives. Therefore, we develop three subsystems: (i) gathering personal and location information of users, (ii) managing huge quantities of user information and creating a group of users on a request basis, and (iii) delivering a message for all users in a requested group. In this paper, we focus on the third subsystem, especially in a combinational configuration of wide-area wireless networks (WiMAX, LTE, and so on) and device-to-device (ad hoc) communication with WLANs. We assume that some users who should receive a message cannot use wide-area wireless networks due their inaccessible communication range or the occurrence of a disaster, and that supplemental device-to-device WLAN communication covers such users. Although multicast communication can provide effective message delivery to users in a group, the overhead increases with the increased number of messages multicast to many users and groups. We propose an on-demand routing scheme for group communication based on a real-spatial information system and evaluate the efficiency of the proposed scheme by a simulation.

Centralized association management for Radio-On-Demand Networks

The field of mobile data communication has seen very rapid growth with an increased number of mobile terminals connecting to the Internet using the IEEE 802.11 standard for wireless local area network (WLAN). As a result, the amount of energy consumed by WLANs is increasing. To reduce this power consumption, we have proposed a Radio-On-Demand (ROD) WLAN that reduces energy consumption in the operation of WLANs. In this study, we propose a centralized association management scheme for a ROD WLAN. In this scheme, a wireless LAN controller assigns the association between access points and stations, a process that saves power in accordance with network utilization. Using simulation studies, we show that the proposed scheme is effective in saving energy.

Adaptive contention window control scheme for dense IEEE802.11 wireless LANs

As portable information devices with a wireless local area network (LAN) interfaces, such as smartphones and tablet computers, become increasingly widespread, high station density and accompanying severe area throughput degradation are becoming more commonplace. One factor related to this situation is that the initial minimum contention windows size (CWmin) value in current Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) systems is set too low for the number of accessing stations. Because small CWmin values are unsuitable for high station densities, frame collisions become more commonplace and per-station communication performance decreases. In this paper, we assume that numerous stations are connected to a single access point (AP) and propose a media access control method for high station density network. In our proposed method, the AP periodically measures channel utilization and the number of stations that are transmitting frames to the AP, and then modifies the CWmin value based on these parameters. The AP then uses a beacon signal to inform the stations accessing the network of the new CWmin value. To verify the performance of our scheme, QualNet network simulations were performed, the results of which show us that, in terms of throughput, our proposed method outperforms conventional CSMA/CA schemes in wireless LAN environments with high station densities.

Station aggregation scheme considering channel interference for radio on demand networks

With the rapid growth of the Internet, deploying energy-efficient networking technology is an urgent matter. In particular, wireless LAN (WLAN), which is widely used due to its ease of deployment and low cost of installation, is also required to be energy efficient. For this purpose, R & D activities for Radio-On-Demand-Networks (ROD) have been proposed. In ROD networks, access points (APs) have been equipped with wake-up receivers, switching their status to sleep mode, depending on the traffic distribution in the network. In the present paper, a station (STA) aggregation scheme in ROD networks considering channel interference is proposed. In this scheme, APs cooperate with each other and aggregate their STAs depending on the channel utilization information rather than the AP utilization. The simulation results reveal the scheme effectiveness in terms of power savings without throughput degradation in WLANs even in the presence of interference.

Field tests and indoor emulation of Real-Spatial Information Based Group Communication

We proposed a novel scheme that combines information exchange and user social activities in real-time so that users can integrate their communications seamlessly with their daily lives. Called the Real-Spatial Information-Based Group Communication (r-Space) system, this scheme creates r-Space groups by considering personal and location information and enables users to share information within those groups. We developed a prototype system consisted of client application and control server and then conducted a field experiment in Nov. 2016. In PerCom 2017, the introduction of the experiment and its live demonstration will be exhibited.