Experimental evaluation of timing synchronization accuracy for QZSS short message synchronized SS-CDMA communication

Abstract

We have proposed spread spectrum code division multiple access (SS-CDMA) short message communication using Quasi-Zenith Satellite System (QZSS) as a safety confirmation system at the time of great disaster. Highly accurate timing and frequency synchronization among all mobile terminals (MTs) is necessary for the synchronized SS-CDMA system to provide high density user multiplexing using long spreading codes in uplink. In order to synchronize the timing that the satellites receive uplink signals, each MT controls its own timing and frequency at the timing of each transmission using QZS and Global Positioning System (GPS) signals. Particularly the number of visible satellites can have a major impact on the time synchronization. In this paper, we evaluated the time synchronization accuracy in the synchronized SS-CDMA system experimentally. The results show that it is possible to achieve accommodation rate of short message system of 100 % when the elevation mask is 30 degrees.