Consideraes s comunicaes acsticas

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Considerações às comunicações acústicas

• É cada vez mais comum a instalação de sistemas
  capazes de monitorizar o ambiente envolvente e o
  controlo de equipamentos subaquáticos junto à
  costa.
• Tipicamente estes sistemas são constituídos por
  sensores localizados no fundo do mar ou na água
  e são ligados à costa tanto por cabo como por via
  radio network através de bóias à superfície.
• Nem sempre é possível a colocação de bóias, ou de
  cabos devido às costas associadas, condições
  ambientais, ou actividades piscatórias. Em tais
  condições a melhor maneira de transferir
  informação é através da comunicação acústica.

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Considerações às comunicações acústicas

• Tem como principais desvantagens
• 1)O ambiente acústico em áreas costeiras ,
  especialmente perto de marinas é muito poluído.
  Pode ser caracterizado por
• -propagação em vários sentidos
• condições de alteração rápida
• alto nível de ruído
• -ausência de um caminho directo para o som entre
  dois modems
• 2)Possui baterias com duração limitada
• 3)Normalmente estas áreas são visitadas por
  mamíferos aquáticos , logo, são necessários
  cuidados para não ferir esses animais, com a
  contínua operação dessa rede subaquática de
  sensores

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Sensores alternativosArgo System
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Argo System

• Comprised of three subsystems
• Hydraulics control buoyancy adjustment via an
  inflatable external bladder, so the float can
  surface and dive.
• Microprocessors deal with function control and
  scheduling.
• Data transmission system controls communication
  with satellite.
• Approx. Weight 25 KgMax. operating depth
  2000mCrush depth 2600m

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• Argo Floats
• Argo is an international collaboration that
  collects high-quality temperature and salinity
  profiles from the upper 2000m of the ice-free
  global ocean and currents from intermediate
  depths. The data come from battery-powered
  autonomous floats that spend most of their life
  drifting at depth where they are stabilised by
  being neutrally buoyant at the "parking depth"
  pressure by having a density equal to the ambient
  pressure and a compressibility that is less than
  that of sea water. At typically 10-day intervals,
  the floats pump fluid into an external bladder
  and rise to the surface over about 6 hours while
  measuring temperature and salinity. Satellites
  determine the position of the floats when they
  surface, and receive the data transmitted by the
  floats. The bladder then deflates and the float
  returns to its original density and sinks to
  drift until the cycle is repeated. Floats are
  designed to make about 150 such cycles.
• Argo Float Models
• The three float models in use are the PROVOR
  built by MARTEC in France in close collaboration
  with IFREMER, the APEX float produced by Webb
  Research Corporation, USA and the SOLO float
  designed and built by Scripps Institution of
  Oceanography, USA.
• Two temperature/salinity sensor suites are used -
  SBE, and FSI. The temperature data are accurate
  to a few millidegrees over the float lifetime.
• Argo Data Transmission
• As the float ascends a series of typically about
  200 pressure, temperature, salinity measurements
  are made and stored on board the float. These are
  transmitted to satellites when the float reaches
  the surface.

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• Cable Architecture
• The Project Observatory Network Cable is based on
  CELTNET architecture
• The cable is the best option for Long-term and
  continuous marine monitoring
• Subsea cabled observatories are the only means of
  continuously acquiring large amounts of different
  data in areas where satellites cannot see and are
  crucial for observing natural processes that are
  very episodic or that require long time series to
  detect
• The architecture is a robust, ring design,
  repeater driven backbone cable that services
  primary nodes through branching units and spur
  cables is proposed to provide a link from shore
  to the remote deep sea sites
• This option would reduce the risk of cost and
  time delays
• System Main Features
• The communication infrastructure of CELTNET will
  be based on optically amplified technology using
  Wavelength Division Multiplexing (WDM). The
  system wavelengths will be in the 1550nm
  wavelength window in order to use
  telecommunication industrial components (state of
  the art design). It will have the following key
  features
• Repeaters (where needed) designed for WDM
  applications.
• Equalization and dispersion management.
• WDM Line Terminal Equipment supporting.
• Global data rate number of nodes X data rate
  for one node (namely 2.5Gb/s original design).
• High reliability submerged components
• Forward Error Correction (FEC).
• Network Management System (state of the art
  design).