Implementation of fast independent component analysis on field‐programmable gate array for resolving the slot collision issue in the space‐based automatic identification system

Abstract

The space-based automatic identification system (S-AIS) is a maritime safety and vessel monitoring system used to broadcast the ship position and other telemetry every few seconds in short bursts. A satellite-based AIS receiver is of interest to defense community as it provides global or wide-area coverage. However, when the satellite passes regions with elevated traffic density, a major challenge is to overcome the message or signal interference at the satellite receiver. This paper mainly focuses on developing a novel AIS satellite receiver that uses fast independent component analysis (FastICA) blind source separation technique to resolve the overlapped signals at the satellite. We propose an architecture to realize FastICA algorithm on hardware. In addition to this, we present Gaussian minimum shift keying modulator and demodulator design schemes used by the S-AIS transponders. The proposed framework is realized on Virtex5-xc5vlx110t field-programmable gate array. The results obtained validate the effectiveness of the FastICA architecture realized by recovering the original ship data from the overlapped signals. K E Y W O R D S blind source separation (BSS), field programmable gate array (FPGA), Gaussian minimum shift keying (GMSK), space-based automatic identification system (S-AIS) 1 | INTRODUCTION The automatic identification system is formulated to provide the static and dynamic ship information to other vessels and the base station for monitoring the ships, for handling the traffic flow, and to prevent the accidental collisions between the ships in high seas. The static information includes call sign, International Maritime Organization (IMO) number, and type of ship, and dynamic information comprises time in Coordinated Universal Time (UTC), speed over ground, heading, and navigational status.1 The conventional communication between the ship to shore and ship to ship in the ground-based network is limited in range by horizon to 40 nautical miles. This constrain is overcome by space-based automatic identification system (AIS), wherein the messages from the ships are received by the satellite for providing global coverage. The transmissions are made with the Gaussian minimum shift keying (GMSK) modulation technique with data rate of 9600 bps in the very high frequency (VHF) maritime mobile band over the frequencies channels 161.975 and 162.025 MHz. Self-organized time-division multiple access (SOTDMA) is the multiple access scheme employed that works on 2250 time slots with the slot duration of 26.66 ms established every 60 s.2 The slot allocation is self-organized within a structured area that is termed as AIS cells. However, the field of view (FoV) of the satellite spans a large number of self organized area (AIS cells). Hence, when several AIS cells are covered during the satellite visibility period, AIS messages sent in the same time slot from different organized areas will reach satellite simultaneously colliding with each other.3 Further AIS messages sent in

Single-channel blind source separation of underwater acoustic signals using improved NMF and FastICA

“…According to the central limit theorem (Krishna et al, 2020), the mixed signal obtained from independent source signals has a high Gaussian distribution. From information theory, the stronger the Gaussian property of the equivariance random variable, the greater its entropy.…”

“…The FastICA algorithm was explicitly built to maximize the non-Gaussian property of mixed observation signals, and negative entropy is used as the parameter. When negative entropy reaches its maximum, the non-Gaussian property of each source signal also reaches its maximum, indicating that each independent component is well-separated (Krishna et al, 2020).…”

The Big Picture: An Improved Method for Mapping Shipping Activities

“…Satellite receivers function similarly to terrestrial receivers by transmitting the received AIS message to a computer for data storage, processing and visualization. Having a large field of view (up to 5000 km), satellite receivers are always in view of the transponders [18].…”