Satellites receiving Automatic Identification System (AIS) packets in dense areas are particularly prone to AIS channel overload due to the extensive number of vessels. Thus a failure of detection might be caused by the collisions among AIS messages. To improve the detection capability, we propose to exploit the presence of the cyclic redundancy check (CRC) in AIS frames by using the parallel list Viterbi algorithm (PLVA) instead of the classical Viterbi algorithm (VA) often used for decoding AIS signals. The performance of combining the PLVA with AIS post processing including the CRC is studied with two detectors, one coherent and the other differential, in two channel models: a single-user AWGN channel and a more realistic multiple-access AIS channel. We also show the impact of the PLVA parameters on the success recovery rate. The simulation results show that the resulting procedure can significantly improve the packet error rate (PER) at the cost of a limited increase of the computational complexity. The proposed technique could be applied to improve the performance of interference cancellation receivers by significantly lowering the AIS decoding threshold.

翻译：在船舶密集区域，卫星接收自动识别系统（AIS）数据包时，由于船舶数量庞大，特别容易发生AIS信道过载。因此，AIS消息之间的碰撞可能导致检测失败。为提高检测能力，我们提出利用AIS帧中循环冗余校验（CRC）的存在，采用并行列表维特比算法（PLVA）替代常用于解码AIS信号的经典维特比算法（VA）。通过两种检测器（一种相干检测器，一种差分检测器），在两种信道模型（单用户AWGN信道和更现实的多址AIS信道）中，研究了将PLVA与包含CRC的AIS后处理相结合的性能。我们还展示了PLVA参数对成功恢复率的影响。仿真结果表明，所提出的方法能以计算复杂度有限增加为代价，显著改善分组错误率（PER）。该技术可用于提升干扰消除接收机的性能，通过显著降低AIS解码阈值来实现。