DS‐SS modulated extremely weak power radio communications system synchronized by a GPS receiver PPS signal

Abstract

With developments in the technology and greater adoption of satellite positioning systems such as GPS, there has been much research into location information systems and services and their practical applications. Extremely weak power radio communications systems are small-scale and low-power devices that do not require a license and are rarely used for communications purposes because they are able to communicate only over small distances compared to other communications media; however, if the distance over which they can be used for communication could be increased, then it would be easy to construct communications systems with them. To take advantage of this we propose an extremely weak power radio communications system based on the DS-SS scheme that synchronizes chips using the pulse-per-second (PPS) signal that is output by a GPS receiver. This system is continuously able to have access to location information due to the use of the GPS receiver and we anticipate that by using this it should be possible to increase the communications distances and communications quality. In recent years there has been an increase in the number of accidents in small-scale ships with low-end communications systems have capsized while at sea or drifted. Small-scale location information systems that can be used for marine distress situations such as capsizing or drifting have become increasingly sought after and communications systems that use such extremely weak power radio communications devices for marine location information systems have been proposed. In this paper we first give an overview of our proposed marine location information system and then describe the extremely weak power radio DS-SS communications system used to implement the system. Following this we perform simple communications experiments. The results of our experiments show that a communications distance of 80 m can be improved to 800 m. From the above results we show that in addition to the marine location information system created using the proposed method, a wide range of different applications are possible. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(12): 39–50, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20379