수중 이동통신 시스템 개발을 위한 패킷 데이터의 확산대역변조 전송 실해역 시험

Abstract

KRISO has been developed an underwater communication system, which should transmit digital data at a rate of more than 100bps at 30km distance between a transmitter and a receiver. For a reliable long distance communication, the spread-spectrum modulation scheme is adapted to get a processing gain and to reduce the multipath interference at the same time by dispreading process at the receiver. Furthermore, a packet structure is designed to cope with Doppler shift due to the relative movement of transmitter and receiver and the ocean current. The designed packet is composed of a 64-chip symbol length preamble, a 64-chip symbol length pause, 16-chip spread DQPSK data symbol, a 64-chip symbol length preamble. The preambles at both end side of packet are used for Doppler shift and channel delay profile estimation and for the synchronization in the receiving process. The designed chip symbol rate and carrier frequency are 3.4kHz and 6.8kHz. If the roll-off factor is 0.35, the required bandwidth is 4.59kHz. The measurement of the transmission performance and the enhancement of receiver signal processing including Doppler compensation will be performed using the gathered data at the sea experiment with a moving as well as a fixed transmission environment. In this workshop, the designed packet structure, the modulation scheme and the designed receiver structure will be presented.trum modulation scheme is adapted to get a processing gain and to reduce the multipath interference at the same time by dispreading process at the receiver. Furthermore, a packet structure is designed to cope with Doppler shift due to the relative movement of transmitter and receiver and the ocean current. The designed packet is composed of a 64-chip symbol length preamble, a 64-chip symbol length pause, 16-chip spread DQPSK data symbol, a 64-chip symbol length preamble. The preambles at both end side of packet are used for Doppler shift and channel delay profile estimation and for the synchronization in the receiving process. The designed chip symbol rate and carrier frequency are 3.4kHz and 6.8kHz. If the roll-off factor is 0.35, the required bandwidth is 4.59kHz. The measurement of the transmission performance and the enhancement of receiver signal processing including Doppler compensation will be performed using the gathered data at the sea experiment with a moving as well as a fixed transmission environment. In this workshop, the designed packet structure, the modulation scheme and the designed receiver structure will be presented.