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Miscellaneous

JANUS Baseline Bit Allocation Table


JANUS Baseline Bit Allocation Table (64 bit total)

Image

The field names are detailed in the following table:

JANUS Bits
1..4
5
6
7
8
9..16
17..22
23..56
57..64
Descriptor
Version Number
Mobility Flag
Schedule Flag
Tx/Rx Flag
Forwarding Capability
Class User ID
Application Type
Application Data Block
CRC8
Bits per Field
4
1
1
1
1
8
6
34
8

The row JANUS Bits refers to transmission order. JANUS follows the Most Significant Bit First (MSBF) transmission ordering scheme (the MSB is the first to be transmitted). Binary numbers are written left to right, with the Least Significant Bit (LSB) being the right-most bit on the table above.
E.g.: the "Version Number" field, where the JANUS version decimal 3 is coded using the 4 bits as 0b0011, will be transmitted as the bit sequence 0 0 1 1.
1st bit: 0
2nd bit: 0
3rd bit: 1
4th bit: 1
The same rationale applies to all fields.

If the Schedule Flag is set to 1, the JANUS standard subdivides the Application Data Block (ADB) 34 bits as follows:

JANUS Bits
23
24..30
31..56
ADP Field Bit #
33
32..26
25..0
Descriptor
Reservation Time/ Repeat Interval Flag Reservation Time/ Repeat Interval User Defined
Bits per Field
1
7
26

The Reservation Time/ Repeat Interval field contents are selected via the Reservation Time/ Repeat Interval Flag field according to:

Reservation Time/ Repeat Interval Flag Reservation Time/ Repeat Interval field contents
0
Reservation Time
1
Repeat Interval

The time values are specified in separate look-up tables in the ANEP-87(external link).

Note:
The bit numbering ADP Field Bit # is included to aid developers since it is a more common bit numbering scheme in Computer Science.