
VITA-49 Radio Transport Protocol
Table 21
: Extension Context Packet Class Structure
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Pkt Type
0 1 0 1
C
R
T
S
M
TSI TSF Pkt Count
Pkt Size
Stream Identifier (1 word)
Timestamp - Integer Seconds (1 word)
Timestamp - Integer Picoseconds (2 words)
Context Indicator Field (1 word)
Context Fields (Variable Size)
1.
Pkt Type
shall be set to
0101
to indicate this is an extension packet.
2.
C
shall be set to
0
to indicate there is no Class Identifier in the packet.
3.
R
shall be set to
00
, because they are reserved bits.
4.
TSM
shall be set to
0
, indicating that context packet timestamps are precise.
5.
TSI
field shall be set to
01
, indicating that integer (seconds) part of the timestamps
are in UTC.
6.
TSF
field shall be set to
10
, indicating that the fractional part of the timestamp
measures in real time picosecond resolution.
7.
Pkt Count
shall start at 0000 and increment once for each context packet, until
reaching 1111, where it shall rollover to 0000 on the next count.
8.
Pkt Size
indicates the total number of 32-bit words in the entire context packet,
including all headers, the context indicator field and context sections.
9.
Stream Identifier
shall be the 32-bit word,
0x90000004
10.
Timestamp - Integer Seconds
shall be in UTC format and will represent the
number of seconds occurred since Midnight, January 1, 1970, GMT.
11.
Timestamp - Integer Picoseconds
shall count the number of picoseconds past
since the last increment of the Timestamp seconds field. See the Picosecond
Timestamp Words Format section for the format.
12. The
Context Indicator Field
shall follow the format indicated in
Table 22:
Extension Context Indicator Field Positions
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9
8
7
6
5
4
3
2
1
0
I
IQ Sc St S
w
13. The
Context Fields
section shall contain a context field for every field that is
indicated to be present in the Context Indicator Field. The fields shall be ordered in
the identical order of their occurrence in the Context Indicator Field. See
for the definition and associated value of each field.
ThinkRF WSA5000 Wireless Signal Analyzer Programmer's Guide
35