DS-CDMA with M-ary Orthogonal Modulation for Wireless Sensor Networks Simultaneously Monitoring Multiple Events

In this paper, we propose a novel WSN framework for one fusion center to monitor simultaneously multiple source events (SEs), each of which has multiple states. In the proposed WSN, every SE is observed by a range of local sensors, which convey their observations to the fusion center in the principles of direct-sequence code-division multiple-access (DS-CDMA) associated with M-ary orthogonal modulation (MOM). Therefore, the proposed WSN is referred to as the MOM DS-CDMA WSN. In the MOM DS-CDMA WSN, the local sensors monitoring the same SE transmit their signals to the fusion center in the principles of time-division multiple-access (TDMA), while the local sensors serving different SEs communicate with the fusion center in the principles of DS-CDMA. By making use of the advantages of MOM, the fusion center detects the SEs' states either coherently based on the maximal ratio combing (MRC) fusion rule, or non-coherently based on the equal gain combining (EGC) fusion rule. The detection performance of the fusion center is investigated by simulations. Specifically, the impacts of the number of SEs, the number of local sensors per SE, the observation reliability of local sensors, the reliability of the channels from local sensors to fusion center, etc., on the fusion detection performance are addressed.