Introducing
Prezi AI.
Your new presentation assistant.
Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.
Trending searches
Loading…
Automatic Identification System (A.I.S.)
14
Transcript
Automatic Identification System (A.I.S.)
SUMMARY
I. Introduction
II. GMSK Modulation
III. Intersymbol Interference
IV. Viterbi's Algorithm
V. Conclusion
GMSK Modulation
Gaussian minimum-shift keying
Viterbi's Algorithm
- Viterbi's Algorithm allows us to correct the errors though noised channel
- Based on the knowledge of the noised channel. And the probability that an information has been modified into another
- Develop a scheme for dynamic calculation of Hamming Distances and Next State/Previous State outputs
- The minimum number of errors that could have transformed one string into the other.
- Assign two variables to each state in the Trellis Diagram
- One to calculate the minimum path metric (total Hamming distance)
- A second to record the previous state input/output transition pair.
- From exponential, this complexity becomes linear.
Intersymbol interference
- CPM (Continuous-Phase Modulation)
(I.S.I)
- Encoding the information on the signal's phase
Phase
Wave form
- form of distortion of a signal in which one symbol interferes with subsequent symbols
- This is an unwanted phenomenon as the previous symbols have similar effect as noise
- Caused by multipath propagation of the inherent non-linear frequency response of a channel causing successive symbols to "blur" together
- This is a data sequence that we wish to send (square pulse)
- Square pulse are nice as an abstraction but are hard to create and require far too much bandwidth
- Shaping at this point is that it reduces bandwidth requirements and can be created by the hardware
- Shows each symbols as it is received
Introduction
- The energy from 1 and 2 goes all the way into symbol 3
- Broadcast line
- Each symbols interferes with one or more of the subsequent symbols
- Acutal signal seen by the receiver
- For 3 notice that the value is half of the transmitted value
- GMSK (Gaussian minimum-shift keying)
- This symbol is more susceptible to noise and incorrect interpretation
- primary used for boat navigation
- Automatic system that exchanges information by VHF radio.
Conclusion
- This information includes the identifier, status, location, direction and speed of the emitter.
- allow maritime authorities to track and monitor vessel movements.
- With this system, it becomes
possible to know the position of all ships over the Earth.
- Use of a Self-Organized Time Division Multiple Access (SOTDMA)
- When satellites are used to detect AIS signatures then the term Satellite-AIS (S-AIS).
- The average period depend of the size
and the speed of the boat.
- Matlab aplication such as GMSK modulation / Viterbi decoder / ISI representation
- Transmission of coded information
- Encoder and decoder operation
- GMSK Modulation
Thank you for your attention
Choose a template
Presentations from around the world
Learn more about creating dynamic, engaging presentations with Prezi