A cyclic redundancy check-based non-coherent receiver for automatic identification system signals

et al. 2018

Summary In space‐based automatic identification system, message collision is inevitable. To separate collision messages in multichannel space‐based automatic identification system, an improved least squares constant modulus algorithm (LSCMA) is proposed in this paper. The algorithm initializes LSCMA by using the result of complex symmetric fast independent component analysis and reduces the dimension of the received signal by using the minimum description length algorithm. At the same time, a new metric named failure rate is proposed to measure the separation performance. The simulation shows that the performance loss caused by the delay, the frequency and phase offset, and the input signal‐to‐interference ratio is within an acceptable range. The proposed algorithm outperforms the original LSCMA and other algorithms in terms of red packet error rate and failure rate.

Section: Least Squares Constant Modulus Algorithmmentioning

confidence: 99%

An improved least squares constant modulus algorithm for collision messages separation in multichannel space‐based AIS

Zhang

Wang

et al. 2018

“…Zhou et al proposed a noncoherent detection scheme for satellite‐based AIS reception that also uses CRC to correct error bits. This scheme suffers from huge complexity.…”

Section: Introductionmentioning

confidence: 99%

Frequency offset insensitive demodulation algorithm for satellite‐based automatic identification system

et al. 2018

The frequency offset caused by the Doppler shift and the oscillators instability degrades the performance of satellite-based demodulators for automatic identification system (AIS) signals unless proper synchronization algorithms are used. A noncoherent demodulation algorithm (NDA) based on cyclic redundancy check (CRC) error correction is proposed in this paper, which is able to tolerate large frequency offsets, thus avoiding the use of an explicit frequency synchronizer. To reduce the complexity, the number of CRC register states for error correction can be limited. Simulation results of the proposed algorithm are presented and compared with other demodulation algorithms in the literature in terms of bit error rate (BER) and packet error rate (PER). KEYWORDSCRC error correction, complexity reduction, Doppler shift, NDA, satellite-based AIS, Viterbi algorithm INTRODUCTIONThe automatic identification system (AIS) is primarily developed for vessel collision avoidance and usually works within the range of very high frequency band. 1 Coverage of coastal stations is about 40 nautical miles, and the communication between a vessel and a coastal station is impossible if the vessel is outside the radio visibility. Therefore, it is difficult to obtain a real-time supervision of all ocean-going vessels. To ensure a global coverage, a good solution is to receive the AIS messages from a constellation of low Earth orbit satellites. 2 However, the AIS standard has not been designed for such a use, and several technical issues arise at the receiver in case of a reception from a low Earth orbit satellite. 3 Doppler shift, message collisions, path delay, and low signal-to-noise values are the main issues degrading the demodulation performance. 3Studies on improving the demodulation performance of AIS signals received by a satellite are still ongoing. Based on maximum likelihood estimation and Viterbi algorithm, an innovative coherent detector is proposed for satellite AIS signals in Gallardo and Sorger. 4 However, the performance of coherent detection relies on accurate parameter estimation and tracking. Especially when a message collision exists, it is difficult to recover and track the carrier phase, thus resulting into a degradation of the coherent detection performance. Noncoherent detection is an attractive alternative, because it is very robust to the oscillators' instability. In Burzigotti et al, 5 a scheme based on the noncoherent sequence detection algorithm of Colavolpe and Raheli 6 is proposed, using three zonal demodulators that process different (but overlapping) frequency bandwidths to increase the system diversity. Since in AIS the cyclic redundancy check (CRC) is used at the transmitter side, the receivers in previous studies 4,5 compare the checksum computed from the received data with the frame check sequence (FCS) to detect transmission error bits. Colavolpe et al 7 replaced the algorithms for synchronization, detection, and postprocessing in Burzigotti et al 5 with new ones obtaining a significant performance i...

“…Then, the Doppler shift is in the range of [−4kHz,4kHz] due to the symmetry of the coverage area. (ii) Because the satellite antenna footprint is much larger than the coverage of a typical SOTDMA region, a satellite‐based AIS equipment would receive uncoordinated messages from ships belonging to different SOTDMA regions , leading to message collisions.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, for ships outside the radio visibility of coast station, those ship-tocoast station communications are difficult. Receiving messages from a constellation of low-earth orbit satellites is a method to solve this problem, ensuring a global coverage [3].…”

Section: Introductionmentioning

confidence: 99%

“…Then, the Doppler shift is in the range of OE 4 kHz; 4 kHz due to the symmetry of the coverage area. (ii) Because the satellite antenna footprint is much larger than the coverage of a typical SOTDMA region, a satellite-based AIS equipment would receive uncoordinated messages from ships belonging to different SOTDMA regions [3], leading to message collisions. Energy detection [7] is a non-data-aided method for frame detection with good detection performance, whereas, it can not distinguish and identify the received signal is an AIS or not.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A constant false alarm rate frame detector for satellite‐based automatic identification system

Wang

Zhang

et al. 2016

Summary Frame detection is an important step in satellite‐based automatic identification system for its contributions in verifying the presence of automatic identification system signal before frame synchronization. In this paper, a constant false alarm rate frame detector is proposed, which exploits the feature implied in the training sequence, to realize frame detection in the presence of additive white Gaussian noise and frequency offset. False alarm probability is related with a threshold, which is independent of the signal and noise. For fixed false alarm probability, the relationship between detection performance and Eb/N0 is analyzed. Simulations prove that the proposed detector outperforms the detector based on cyclic autocorrelation when message collisions exist. Copyright © 2016 John Wiley & Sons, Ltd.