Coherent Demodulation of GMSK-AIS Signals

Coherent Demodulation of GMSK-AIS Signals

Coherent Demodulation of AIS-GMSK Signals in Co-Channel

Originally implemented for the US Navy, the Automatic Identification System (AIS) system transmits a burst Gaussian Minimum Shift Keyed (GMSK) signal designed to alert ships of other nearby ships. This technology is an improved method of demodulating GMSK-AIS signals that does not require user-specific training codes and does not utilize an equalizer.

In this technology, the GMSK signal is basebanded, which enhances favorable signal qualities and decorrelates interfering signals. The error rate is also significantly reduced by using and applying poly-bit matched filters and a Viterbi decoding algorithm.

The technology also does not require preamble codes.

 

Abstract: 

Click to view PDFs of these patents on the US Patent and Trademark Office website: Patent 8,275,077

applications: 
  • Demodulation of GMSK signals with co-channel interference
  • Improved AIS signal processing
Patent Number: 
8,275,077
Patent Issue Date: 
September 25, 2012
Email: 
tech_transfer@nsa.gov
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