Prototype LRPT Receiver

1
Prototype LRPT Receiver

• NOAA Satellite Direct Readout Conference for the
  Americas
• December 9-13, 2002
• Miami, FL
• Wai Fong
• NASA/GSFC
• Code 567
• Microwave and Communications System Branch
• wai.h.fong_at_.nasa.gov

2
Background

• Low-Resolution Picture Transmission (LRPT) is a
  proposed standard for direct broadcast
  transmission of satellite weather images for
  METOP
• LRPT definition is a joint effort by EUMETSAT and
  NOAA
• Goddard Space Flight Center was tasked to build
  an LRPT Demonstration System (LDS) and study the
  protocol performance

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Objective

• To develop and demonstrate the feasibility of a
  low-cost receiver utilizing as much
  Commercial-off-the-shelf (COTS) equipment as
  possible.
• Determine the performance of the protocol in a
  simulated Radio Frequency (RF) environment.

4
Approach

• Utilize Personal Computers as the primary
  processing component.
• Develop all software elements to process and
  control data flow.
• Identify and procure COTS RF modulator/demodulator
  (MODEM).
• Utilize the Institute for Telecommunications
  Sciences (ITS) study for modeling two noise
  environments Residential (Lakewood, CO) and
  Business (Downtown Denver, CO).
• Perform BER analysis of protocol and simulate a
  satellite pass.
• Use Modulated Lapped Transform (MLT) instead of
  current JPEG variant.

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Top-level Diagram
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Transmitter Description

• Compress, channel code and CCSDS format AVHRR
  data off-line and store in the Transmitter buffer
• RF Modem performs QPSK modulation

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Transmitter Block Diagram
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Key Features of the Receiver

• Hardware elements
• Modem performs QPSK demodulation
• Bit synchronization producing 3-bit soft-decision
  samples
• Real-time Software elements
• Unique Word (UW) synchronization
• Convolutional de-interleaving
• Viterbi decoding
• CCSDS Frame Synchronization
• CCSDS Block de-interleaving
• Reed-Solomon decoding
• CCSDS Virtual-Channel processing
• CCSDS Packet processing
• Modulated Lapped Transform (MLT) decompression
• Image Display
• Status/Statistical analysis and display

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Receiver Block Diagram
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Noise and Scintillation Generation

• Noise and Scintillation patterns are generated by
  ITS models.
• Use Pattern Generators to drive programmable
  attenuators and phase shifters.

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Testing Block Diagram
12
Summary of Results

• 40 of the CPU bandwidth required for Receiver
  processing.
• 7 dB of coding gain at the output of the Viterbi
  decoder _at_ 10-4 BER in a residential environment
  with Man-made/Gaussian noise and Scintillation.
• Coding gain decrease to 5.2 dB as the Man-made
  noise increased for the urban environment.
• Use of convolutional interleaving can provide as
  much as 2 dB of gain.
• The output of the R-S decoder was virtually
  error-free as long as the receiver maintained
  solid lock.
• For residential (low noise) environments e.g.
  Lakewood, nearly 100 coverage for either Yagi or
  Omni antenna.
• In high noise urban environments like Downtown
  Denver, 65 coverage using an Omni antenna.

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Conclusion

• Protocol mitigates scintillation and man-noise
  effects.
• In larger more populated metropolitan areas, use
  a tracking Yagi antenna and/or a better receiver
  due to the noisier environment.
• Inexpensive LRPT receivers can be made by using
  software to perform most of the receiving
  functions.

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Demonstration

• Pass simulation of Downtown Denver with Omni
  Antenna in Man-made noise/Gaussian noise and
  Scintillation
• Pass simulation of Lakewood with Yagi Antenna in
  Man-made noise/Gaussian noise and Scintillation