LT Terry D. Norbraten, USN December 2004
description
Transcript of LT Terry D. Norbraten, USN December 2004
UTILIZATION OF FORWARD ERROR CORRECTION (FEC) TECHNIQUES WITH
EXTENSIBLE MARKUP LANGUAGE (XML) SCHEMA-BASED BINARY COMPRESSION (XSBC)
TECHNOLOGY
LT Terry D. Norbraten, USN
December 2004
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The Very Basics
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Formally known as Cross-format Schema Protocol (XFSP) in NPSNET-V
Target Area XML Serialization / XML Marshalling Transactions via XML with reliability
Possible Applications Networked Virtual Environments (NVEs) AUV Workbench Server / AUVs, UUVs, UAVs XML-based Tactical Chat (XTC)
Benefits Schemas can be tailored: No need to hard code protocols Compact Efficient Platform-independent Run-time extensibility Built-in redundancy with minimal cycle overhead
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XSBC w/ FECIdea : Creating DOM Pipe between users
FEC Encoded XML Data
FEC Encoded XML Data
FEC E
ncod
ed X
ML Dat
a
Schema
Schema
Schema
Schema
Schema
Schema
DOM : Document Object Model
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XSBC w/ FEC Data Flow
XML Data Flow
XML SchemaDefining Mission Data Document
Structure
GZip/XSBC SerializerModule
FEC Encoder(Optional)
AUV Acoustic Modem
XML Document (Mission Data) to transmit Acoustic Medium
XML Document (Mission Data) stored from an AUV
UnGZip/XSBC De-Serializer
Module
FEC Decoder
XML SchemaDefining Mission Data Document
Structure
AUV Workbench Server Acoustic Modem
Acoustic Medium
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XSBC w/ FECProcess: XML Serialization and Encoding
Parse the schema document Create a look-up table for attributes and elements Assign unique numbers to the elements and
attributes Walk through the XML tree and put each element
and attribute into the output stream by replacing their tag names with numbers
Capture bit stream and encode with redundancy: an (n, k) code takes k original source symbols and encodes n-k redundant symbols, then sends all n via UDP packets
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XSBC w/ FEC
<?xml version="1.0" encoding="UTF-8"?><protocol xmlns:xsi="http://www.w3.org/2001/XMLSchema-
instance"xsi:noNamespaceSchemaLocation="example.xsd">
<location x="3.45" y="56.72" z="-10.1"/><header>
<exerciseID>1</exerciseID><version>1</version><pduType>2</pduType>
</header><velocity x="1.0" y="0.0" z="-0.7"/>
</protocol>
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XSBC w/ FEC
<10><14 24="3.45" 25="56.72" 26="-10.1" 15><12>
<18>1<19> <20>1<21> <22>2<23>
<13><16 27="1.0" 28="0.0" 29="-0.7" 17>
<11>
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FEC Overview
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XSBC w/ FEC
Process: Decoding and XML De-serialization Receive any subset k of the n UDP repair
packets sent to reconstruct original data Read tag numbers from decoded data symbols Retrieve element or attribute associated with
that number Read the data
Create the elements, attributes and bind data to them
Rebuild the XML tree Store reconstructed file for later retrieval
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UDP Example of XML -> XSBC -> FEC and back
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FEC Principle of Operation
Encoded data represented as:y = E x
where x is a k-vector with source data, y is an n-vector with the redundant info and E is an n*k derived Vandermonde matrix.
The code is systematic.
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FEC Principle of Operation
At the receiver, any subset y’ of k elements from y allows the reconstruction of the whole x by solving the system:
y’ = E’ x
where E’ is made of rows from E corresponding to the received elements
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Systematic code data recovery
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ComparisonTool
AutonomousVehicleMissionOutputXML file
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Teapot Exemplar