Multi-mode communication-based cooperative networking of UFCs for energy saving

Abstract

In 2005, our research team launched a project aimed at realizing a campus-wide ubiquitous computing environment, named U-TOPIA. In U-TOPIA, there are many WLAN access points distributed in a wide mesh manner, allowing users to continuously access network services everywhere. Our team have also developed a wearable computing platform, named Ubiquitous Fashionable Computer, as a main user computing device in U-TOPIA. It possesses three wireless communication interfaces: WLAN, Bluetooth, and ZigBee. Thus, UFC users in U-TOPIA can use variety of wireless networking services from e-mail services to remote conference applications. Sometimes, several UFC users get together and work for a common goal. For example, some friends on a bench connect to the same server and play on-line games together. In this case, individual battery lifetimes are critical factors that decide the lifetime of the group of friends. If one should quit because his battery runs out, then remaining others also can not continue playing game. Therefore, it is a challenging issue that how to extend the lifetime of a group when several UFC users work together. In this thesis, we present an energy-saving system, named CoNet, which maximizes the lifetime of a UFC group by cooperative networking. In CoNet, UFCs with multiple wireless interfaces form a group and cooperate with each other to minimize the power consumption of the wireless interfaces so that they can work together for a longer period. Among the interfaces, WLAN consumes about 50% of the total power consumption. Thus, it is important to reduce the WLAN power-on time to increase the lifetime of UFC. In CoNet, one of the grouped UFCs becomes a Bluetooth access point for the group, allowing others can use low-power Bluetooth rather than high-power WLAN for wireless networking. Thus, others can signi¯cantly reduce the power total consumption, while the WLAN provider can not. In CoNet, under the role switching algorithm proposed in this t...