- Fast Access Channel Data -
drm008001.jpg
FAC data

The FAC block contains 72 bits of information (64 bits of FAC data plus 8 bit CRC checksum) to allow the DRM software to decode the multiplex. FAC parameters include: spectrum occupancy, interleaver, modulation mode, number of services, language, audio or data, programme type.

Whatever the spectrum occupancy or transmission mode the DRM decoder always needs this FAC information first to know how to decode the rest of the DRM signal. Consequently the FAC is always transmitted in the same place with a fixed code rate. Comparing DRM to AM then the FAC would occupy the equivalent location of AM upper sideband.

Each transmission frame contains an FAC block (400 mSec). When more than one service is carried in the multiplex, a number of FAC blocks are required to describe all the services.

base/
enhance flag 

1 bit

0 : base - decodable by all DRM receivers
1 : enhancement only decodable by enhanced receivers

identity

2 bits

identifies current frame and validates SDC AFS index:
0 : first FAC of super frame and AFS index is valid
1 : second FAC of super frame
2 : third FAC of super frame
3 : first FAC of super frame, AFS index is invalid

RM flag

1 bit

0: robustness modes A, B, C or D

1: robustness mode E

spectrum occupancy

3 bits

if RM = 0
0 : 4.5 kHz
1 : 5.0 kHz
2 : 9.0 kHz
3 : 10 kHz
4 : 18 kHz
5 : 20 kHz
6 - 7 : not defined

if RM =1
0 : 100 kHz (DRM+)
1-7 : not defined

time interleaver

1 bit

RM = 0
0 : 2 Seconds (long interleaving)
1: 400 milliSec (short interleaving)
RM = 1
0 : 600 milliSec

1 : reserved

MSC modulation mode

2 bits

0 : 64-QAM, no hierarchical
1 : 64-QAM, hierarchical on I
2 : 64-QAM, hierarchical on I&Q
3 : 16-QAM, no hierarchical

SDC mode

1 bit

0 : 16-QAM
1 : 4-QAM

number of audio and
data services

4 bits

00 : 4 audio services
01 : 1 data service
02 : 2 data services
03 : 3 data services
04 : 1 audio service
05 : 1 audio service and 1 data service
06 : 1 audio service and 2 data services
07 : 1 audio service and 3 data services
08 : 2 audio services
09 : 2 audio services and 1 data service
10 : 2 audio services and 2 data services
11 : reserved
12 : 3 audio services
13 : 3 audio services and 1 data service
14 : reserved
15 : 4 data services

re-configuration index

3 bits

status and timing of a multiplex reconfiguration.
Non-zero value indicates the number of transmission super frames before the new configuration will take effect

rfu

2 bits

reserved for future use and set to zero until defined.

service identifier

24 bits

indicates the unique identifier for this service

short identifier

2 bits

assigned to this service and used as a reference in the SDC

conditional access flag

1 bit

0 : no CA system in use
1 : CA system in use - details provided by SDC

language of target audience
* further languages indicated by SDC data

4 bits

00 : no language specified
01 : Arabic
02 : Bengali
03 : Mandarin
04 : Dutch
05 : English
06 : French
06 : German
08 : Hindi
09 : Japanese
10 : Javanese
11 : Korean
12 : Portuguese
13 : Russian
14 : Spanish
15 : Other language

audio/data flag

1 bit 

0 : audio service
1 : data service

service descriptor
if audio/data flag = 0 then
the field indicates the
programme type:

If audio/data flag = 1 (data)
then the 5 bit field indicates
the application identifier of a
data service.

A value of 0 indicates that
the application details are provided by SDC data entity type 12.

A value of 31 indicates
that a DRM receiver
should skip this broadcast and continue to scan, this allows test transmissions to

be ignored by DRM receivers

5 bits

00 : no programme type
01 : news
02 : current Affairs
03 : information
04 : sport
05 : education
06 : drama
07 : culture
08 : science
09 : varied
10 : pop music
11 : rock music
12 : easy listening music
13 : light classical
14 : serious classical
15 : other music
16 : weather/meteorology
17 : finance/business
18 : children's programme
19 : social affairs
20 : religion
21 : phone in
22 : travel
23 : leisure
24 : jazz music
25 : country music
26 : national music
27 : oldies music
28 : folk music
29 : documentary
30 : not defined

31 : skip (test transmission)

conditional access flag

1 bit

0 : no CA system in use
1 : CA system in use
 (details provided by SDC data)

rfa

6 bits

reserved for future additions
- set to zero until defined

 

 

 

DRM background
COFDM
FAC
SFN
MSC
SDC data 1
Multimedia
Bandplan
DRM future
DRM audio
FAC sync
DRM multiplex
DRM modes
SDC data 2