org.orekit.gnss.rflink.gps

Class SubFrame

java.lang.Object

org.orekit.gnss.rflink.gps.SubFrame

Direct Known Subclasses:

SubFrame1, SubFrame2, SubFrame3, SubFrame45

public abstract class SubFrame
extends Object

Container for sub-frames in a GPS navigation message.

Since:

12.0

Author:

Luc Maisonobe

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	PARITY_SIZE Size of parity field.
static int	PREAMBLE_VALUE TLM preamble.
protected static int	WORD_SIZE Words size.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SubFrame(int[] words, int nbFields) Simple constructor.

Method Summary

Modifier and Type	Method and Description
static boolean	checkParity(int previous, int current) Check parity.
int	getAlert() Get alert flag.
int	getAntiSpoofing() Get anti-spoofing flag.
protected int	getField(int fieldIndex) Get a field.
int	getId() Get sub-frame id.
int	getIntegrityStatus() Get integrity status flag.
int	getMessage() Get telemetry message.
int	getPreamble() Get telemetry preamble.
int	getTow() Get Time Of Week of next 12 second message.
boolean	hasParityErrors() Check if the sub-frame has parity errors.
static SubFrame	parse(EncodedMessage encodedMessage) Builder for sub-frames.
protected void	setField(int fieldIndex, int wordIndex, int shift, int nbBits, int[] words) Set a field.
protected void	setField(int fieldIndex, int wordIndexMSB, int shiftMSB, int nbBitsMSB, int wordIndexLSB, int shiftLSB, int nbBitsLSB, int[] words) Set a field.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

PREAMBLE_VALUE

public static final int PREAMBLE_VALUE

TLM preamble.

See Also:

Constant Field Values

WORD_SIZE

protected static final int WORD_SIZE

Words size.

See Also:

Constant Field Values

PARITY_SIZE

protected static final int PARITY_SIZE

Size of parity field.

See Also:

Constant Field Values

Constructor Detail

SubFrame

protected SubFrame(int[] words,
                   int nbFields)

Simple constructor.

Parameters:

words - raw words

nbFields - number of fields in the sub-frame (including TLM and HOW data fields, excluding non-information and parity)

Method Detail

parse

public static SubFrame parse(EncodedMessage encodedMessage)

Builder for sub-frames.

This builder creates the proper sub-frame type corresponding to the ID in handover word and the SV Id for sub-frames 4 and 5.

Parameters:

encodedMessage - encoded message containing exactly one sub-frame

Returns:

sub-frame with TLM and HOW fields already set up

See Also:

SubFrame1, SubFrame2, SubFrame3, SubFrame4A0, SubFrame4A1, SubFrame4B, SubFrame4C, SubFrame4D, SubFrame4E, SubFrameAlmanac, SubFrameDummyAlmanac

checkParity

public static boolean checkParity(int previous,
                                  int current)

Check parity.

This implements algorithm in table 20-XIV from IS-GPS-200N

Parameters:

previous - previous 30 bits word (only two least significant bits are used)

current - current 30 bits word

Returns:

true if parity check succeeded

hasParityErrors

public boolean hasParityErrors()

Check if the sub-frame has parity errors.

Returns:

true if frame has parity errors

getField

protected int getField(int fieldIndex)

Get a field.

The field indices are defined as constants in the various sub-frames classes.

Parameters:

fieldIndex - field index (counting from 0)

Returns:

field value

setField

protected void setField(int fieldIndex,
                        int wordIndex,
                        int shift,
                        int nbBits,
                        int[] words)

Set a field.

Parameters:

fieldIndex - field index (counting from 0)

wordIndex - word index (counting from 1, to match IS-GPS-200 tables)

shift - right shift to apply (i.e. number of LSB bits for next fields that should be removed)

nbBits - number of bits in the field

words - raw 30 bits words

setField

protected void setField(int fieldIndex,
                        int wordIndexMSB,
                        int shiftMSB,
                        int nbBitsMSB,
                        int wordIndexLSB,
                        int shiftLSB,
                        int nbBitsLSB,
                        int[] words)

Set a field.

Parameters:

fieldIndex - field index (counting from 0)

wordIndexMSB - word index containing MSB (counting from 1, to match IS-GPS-200 tables)

shiftMSB - right shift to apply to MSB (i.e. number of LSB bits for next fields that should be removed)

nbBitsMSB - number of bits in the MSB

wordIndexLSB - word index containing LSB (counting from 1, to match IS-GPS-200 tables)

shiftLSB - right shift to apply to LSB (i.e. number of LSB bits for next fields that should be removed)

nbBitsLSB - number of bits in the LSB

words - raw 30 bits words

getPreamble

public int getPreamble()

Get telemetry preamble.

Returns:

telemetry preamble

getMessage

public int getMessage()

Get telemetry message.

Returns:

telemetry message

getIntegrityStatus

public int getIntegrityStatus()

Get integrity status flag.

Returns:

integrity status flag

getTow

public int getTow()

Get Time Of Week of next 12 second message.

Returns:

Time Of Week of next 12 second message (s)

getAlert

public int getAlert()

Get alert flag.

Returns:

alert flag

getAntiSpoofing

public int getAntiSpoofing()

Get anti-spoofing flag.

Returns:

anti-spoofing flag

getId

public int getId()

Get sub-frame id.

Returns:

sub-frame id