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