Extended Dependable Air: Use of Satellites in Boosting Dependability of Public Wireless Communications

Abstract

We propose “Extended Dependable Air” as a highly reliable wireless network. Extended Dependable Air can be used in the “3S” areas: space, surface, and sea. For the implementation of the Extended Dependable Air, two key technologies using satellite systems such as the Quasi-Zenith Satellite System (QZSS) and the Global Positioning System (GPS) are proposed; One is a QZSS Spread Spectrum Code Division Multiple Access (SS-CDMA) short-message communication system, and the other is a heterogeneous wireless system with a network selection scheme using positioning information. The former, the QZSS SS-CDMA short-message communication system, is proposed for large-scale disaster relief. The target capacity of the proposed system is the transmission of at least three million message data per hour. Because this method provides high-density user multiplexing using long spread codes in the uplink, highly accurate timing and frequency synchronization among all terminals is the most important issue. SS-CDMA ensures the use of QZSS positioning signals and maintains the orthogonality in the time and frequency domains among all the codes transmitted from terminals. The latter, the heterogeneous wireless systems, are candidates for achieving a large capacity in next-generation mobile communication systems. In this section, we propose a cell selection scheme for data traffic optimization in heterogeneous wireless systems. The proposed scheme uses high-accuracy positioning information and the average signal strength for cell selection. Using positioning information, users can select a cell with the highest channel quality quickly and easily. It is considered that the proposed scheme will be useful for optimizing data traffic offloading in heterogeneous wireless networks.