Metal Gradient

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Metal Gradient

METHODS FOR PROCESSING

AND INTERPRETATION OF AIS

SIGNALS

CORRUPTED BY NOISE AND

PACKET COLLISIONS.

Authors:

Juris Poļevskis

Mārtins Krastiņš

Gundars Korāts

Aleksandrs Skorodumovs

Jānis Trokšs


● Goal

To test performance of various AIS receivers

with signals as close as possible to spacebased

receiver.


Introduction


AIS – Automatic Identification System

– Ship (and land) based

– Application – safety and data gathering

– Transmits position, heading, speed etc.

– 161.75MHz and 162.25MHz frequency bands

– 9.6kbps GMSK modulation

– TDMA – Time Division Multiple Access


Introduction


AIS in space

– Interest of academics since 2006

– Covers large area

– Access to remote waters

– Problems




Low signal-to-noise ratio

Doppler shift

Packet collision


Introduction


Introduction


SDR – Software Defined Radio


USRP – Universal Software Radio Peripheral

– Universal transceiver

– Various radio front-end daughterboards

– Wide band (WBX 50MHz-2GHz)

– Uses GNU Radio development toolkit

– Networked and embedded versions


Experiment


Signal generation (GNU Radio)

● SDR transmitter (USRP N210)



AIS receiver

Data registration


Experiment


5 parameters:

– Primary signal amplitude

– Primary signal frequency shift

– Secondary signal amplitude

– Secondary signal frequency shift

– Noise amplitude


Results – percentage of messages decoded for

each parameter set.


Experiment


Receivers




Transas Ipx7 commercial AIS receiver

CML Microcircuits DE70321 demonstration

board

USRP E100 based SDR AIS receiver


Results


Results



Shows probability

of decoding based

on main and

interfering signal

frequency shifts

Averaged over all

amplitudes


Conclusions


Hardware based AIS receivers perform

adequately

– Effect of Doppler shift depends on receiver

– Packet collisions will cause drops regardless



Testing of software based AIS receiver was

unsuccessful

Additional work is necessary


Thank you for attention!


Tapis projekta "Programmvadāma (SDR)

satelītkomunikācijas modeļa izstrāde", Nr.

2010/0266/2DP/2.1.1.1.0/10/APIA/VIAA/117

ietvaros

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