講演抄録/キーワード |
講演名 |
2017-03-01 16:25
衛星AISにおける衝突パケット分離検出 ○神澤貴紀・府川和彦(東工大)・平原大地(JAXA)・張 裕淵(東工大) RCS2016-302 |
抄録 |
(和) |
AIS (Automatic Identification System) の情報は,遠洋においても衛星により入手可能となっている.国内では,JAXAがSPAISE (SPace-based AIS Experiment) と呼ばれる衛星搭載船舶自動識別システム実験を実施しており,AIS 受信機を搭載した衛星を高度600 km に打ち上げ,ドップラ変動を伴うAIS 信号を観測している.実験結果から,衛星の受信可能範囲が非常に広いため多くのAIS 信号パケットが衝突し,信号検出が困難になるという問題が明らかになった.本報告では,ドップラ周波数と受信遅延がパケットごとに異なることを利用し,衛星での受信時に衝突したパケットを分離検出する方法を検討する.まず,トレーニング信号をドップラ周波数の候補値で位相回転させ,さらに受信遅延時間候補で遅延したものと受信信号との相関を求める.相関値に最大ピークが現れるドップラ周波数候補と受信遅延時間候補を求め,そのトレーニング信号成分を受信信号から差し引き,相関ピークがある値以下になるまでこれを繰り返し,衝突パケットのパラメータを推定する.次にこれらの推定値に加えて複素包絡線の推定値を用いて,SIC (Successive Interference Canceller) による信号検出とレプリカ減算を繰り返す.計算機シミュレーションにより,衝突パケット数2で平均電力差10 dBのとき,パラメータ推定値の平均2乗誤差を求め,平均BER$= 10^{-3}$を達成できることを明らかにする. |
(英) |
Information of Automatic Identification System (AIS) can be obtained across the open sea by satellites. In Japan, JAXA has conducted a SPace-based AIS Experiment (SPAISE). In this experiment, satellites equipped with AIS receivers have been launched to an altitude of 600 km and have observed AIS signals suffering from Doppler shift. The experiment results clarify that the wide coverage of the satellite causes collision of many AIS signal packets, which makes signal detection very hard. To detect the collided packets separately, this report proposes a separate detection method exploiting Doppler frequencies and delayed time that are different among collided packets. First, the phase of the training sequence is rotated by candidates of the Doppler frequency and then its received timing is delayed by candidates of delayed time. Then, the correlation between the resultant training sequences and the received signals is calculated. By searching for the highest peak of the correlation, we can determine the Doppler frequency and delayed time of the dominant AIS packet. The training sequence with the estimated Doppler frequency and delayed time is subtracted from the received signals. The correlation between the resultant received signals and training sequences is recalculated. These processes are repeated until the peak of the correlation does not exceed a threshold, which we can estimate the parameters of collided packets. Using estimates of these parameters and complex envelope, successive interference cancellation (SIC) iteratively detects AIS signals and subtracts the replica signals from the received signals. Computer simulations under the condition of two collided packets evaluate mean squared estimation errors of these parameters and complex envelope. It is also shown that the average bit error rate of $10^{-3}$ can be achieved with a difference of average received powers being 10 dB. |
キーワード |
(和) |
自動船舶識別装置 (AIS) / 衛星AIS実験 / 衝突パケット数 / 相関検出 / SIC / / / |
(英) |
Automatic Identification System (AIS) / SPAISE / packet collision number / correlation detection / SIC / / / |
文献情報 |
信学技報, vol. 116, no. 479, RCS2016-302, pp. 79-84, 2017年3月. |
資料番号 |
RCS2016-302 |
発行日 |
2017-02-22 (RCS) |
ISSN |
Print edition: ISSN 0913-5685 Online edition: ISSN 2432-6380 |
著作権に ついて |
技術研究報告に掲載された論文の著作権は電子情報通信学会に帰属します.(許諾番号:10GA0019/12GB0052/13GB0056/17GB0034/18GB0034) |
PDFダウンロード |
RCS2016-302 |