# Presentation: 391487

## 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@.nasa.gov

## 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

## 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.

## 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.

## Top-level Diagram

## Transmitter Description

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

## Transmitter Block Diagram

## 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

## Receiver Block Diagram

## Noise and Scintillation Generation

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

## Testing Block Diagram

## Summary of Results

- 40% of the CPU bandwidth required for Receiver processing.
- 7 dB of coding gain at the output of the Viterbi decoder @ 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.

## 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.

## 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