From: pbaatech@peg.apc.org
Subject: The Complete DAB, parts 2 & 3 of 6
Originator: wdp@gagme
Organization: Australia Public RADIO
Date: Thu, 15 Oct 1992 00:08:15 GMT

****************************SECTION 2**************************
****EBU REQUIREMENTS FOR DAB  (AS PER CCIR RECOMMENDATIONS)****

  SOUND QUALITY LEVELS
* High quality stereo indistinguishable from CD/R-DAT

* Possibility of transmitting program with lower bit rate in
  order to optimize the number of sound channels.


  SOUND CONTROL SIGNALS
* Transmission of control informations on sound presentation,
  loudness,  dynamic range compression, matrix etc.


  SERVICE CONFIGURATIONS
* High quality monophonic sound 

* Possibility of adding further coherent sound 
  channels,e.g.surround sound

* Value added services with different data capacities and 
  delivery  time, e.g. Traffic message channel, business data,
  paging, still  picture/graphics, 1.5 Mbits/s video/sound 
  multiplex, future  integrated  services digital broadcasting 
  (ISDB).

* Flexible allocation/realocation of services without affecting 
  continuing  services

  SERVICE DELIVERY * Use of common signal processing in receivers 
  for:
a) Local, regional and national terrestrial VHF/UHF networks
b) mixed use of terrestrial and national/supernational UHF 
   satellite services
c) cable distribution

  SERVICE INFORMATION
* Radio programme data related to each programme signal,
  programme labelling, programme delivery control, copyright 
  control, conditional  access, dynamic programme linking,
  service for hearing-impaired.Cross - referencing between 
  corresponding DAB and VHF/FM services is required.

* Multiplex system information, simple programme or service 
  identification, selection and linking.

  INTERFACE
* Recording capability in bit-rate reduced form and related data.
  This  implies recording the complete programme signal including 
  its programme   related data, and the ability to access small 
  blocks of data in the encoded signal.

* Data interface to Information Technology Equipment (ITE) and 
  communication networks.

  SERVICE AVAILABILITY.
* Mobile, portable and fixed reception
* High coverage availability in location and time.
* Subjectively acceptable failure characteristics
* High immunity to multipath, (long and short delay) and Doppler 
  effect for mobile receivers.

  UNIVERSALITY.
* The system shall be suitable for fixed, portable and mobile 
  reception.
* Use of common signal processing in receivers for different 
  types of services delivery facilitating a common receiver 
  design.

  SPECTRUM EFFICIENCY.
* High spectrum utilisation efficiency, better than FM, maximize 
  frequency  and single frequency network, minimize sharing 
  constraints with other  services (claim: 3X improvement for 
  SFN than for VHF/FM )

* Multiple programme service provision within a contiguous
  frequency band.

  OPERATIONAL REQUIREMENTS.
* Sound Codec cascadability desirable, at least 2 codecs
* Minimum sound signal delay, and known fixed amount.

COMPLEXITY.
* Low cost basic receivers configuration.
* Use simple, non-directional antenna.


**************************SECTION 3****************************
*******************EBU POSITION MONTREUX 1992******************

TERRESTRIAL DAB
- In Europe, large terrestrial DAB networks should be primarily 
in the VHF band(s) to provide economic continuity of coverage 
areas in both rural and urban terrain.

- No new frequency band under 1 GHz is currently available, It 
follows that new DAB services has to be accommodated in bands 
already heavily used by broadcasting

- VHF Band I may be suitable, but further investigation are 
needed in respect of the effect of man-made noise and significant 
sporadic-E propagation effects.

- VHF  Band II and III (50 - 230 MHz) are particularly suited for 
DAB. Spectral efficiency of DAB is most evident when used in a 
Single Frequency Network (SFN) operating in this band which 
typically would operate with the same transmitter site separation 
as currently used in VHF/FM networks, thus avoiding  major 
modification and investment in transmitter site infrastructure.

- UHF (Band IV/V) for a terrestrial DAB service is much less 
favourable than Band I, II or III due to the much more dense 
transmitter network needed for a SFN service, the terrain effect 
being more significant at such frequencies and the technical 
implication of system performance (i.e. lesser spectral 
efficiency) to serve fast moving vehicle.

- UHF Band IV/V could be used for smaller scale local services, 
but consideration of the economics of receiver manufacture may 
militate against such an approach.

- For majority of European countries,the upper part of Band III 
(TV channel 12) seems likely solution for the start of DAB. The 
final frequency band will probably be all or part of Band II 
(87.5-108 MHz), the PRESENT FM Band.


SATELLITE DAB
- Satellite delivery will be possible in the long term at 
frequency allocated by WARC-92 (1452-1492 MHz)

- EBU and CCIR technical studies  have indicated that the 
operation of satellite services at around 1.5 GHz would offer the 
widest range of implementation flexibility.

- The European Space Agency (ESA) is currently defining an 
experimental pre-operational pilot satellite (ARCHIMEDES) 
operating at 1.5 GHz which could be launched 1997. Archimedes 
will transmit from a highly inclined elliptical orbit (HEO) thus 
allowing a considerable reduction in radiated power for high 
latitude countries given the implementation of directive 
receiving antenna with some gain.

-Satellite in Geostationary orbit (GSO) would be of greater 
benefit to the consumer and the overall service concept if it can 
be achieved economically. GSO satellites generally require more 
radiated power but do not require directive antenna; thus the 
reception is fairly independent of a given orbit position. 
Terrestrial gap-fillers can be installed to augment reception in 
permanently shadowed areas.

-The concept of using gap-fillers on the same frequency in order 
to minimize the satellite ERP is called HYBRID. The higher the 
satellite ERP, the lower the number of gap-filler required in 
build-up areas. Gap-filler  will not normally be required in sub-
urban or rural areas, except for tunnels etc.

- The band allocated for satellite DAB may also be used by 
terrestrial DAB services (not related to a satellite service).on 
a local or regional basis, provided that if both use the same 
COFDM block they do not mutually interfere. Such a concept of 
additional terrestrial services in the satellite band (but not 
exactly on the satellite frequency) is called MIXED. Individual 
stations augmented by gap-fillers on the same frequency, thus 
forming a small area SFN covering for example a large city and 
its agglomeration can be envisaged.


RECEIVERS
- Receivers  initially are likely to cover Band II/III and 
possibly Band IV/V  but should be designed so that a simple 
converter can be added to provide the 1.5 GHz band. 

- All terrestrial DAB receivers should be capable of receiving 
Band II (87.5-108 MHz) for both analogue(VHF/FM) and digital 
(DAB) transmissions. 

- All receivers will employ a common signal processing for 
terrestrial and satellite transmissions, but in reality. certain 
system parameters have been selected to adapt to frequency bands 
foreseen for DAB; depending of the network configuration, three 
different operating modes are defined, each having its particular 
set of parameters and all of which must be implemented in the 
decoding chip of every receiver:

MODE I  SINGLE FREQUENCY NETWORK (SFN) as applicable in Bands I, 
II and III (cut off at 340 MHz)

MODE II LOCAL SERVICES  as applicable to local broadcasting in 
Bands I to V (47-862 MHz)

MODE III SATELLITE SERVICES as applicable to satellite, hybrid 
and mixed satellite/terrestrial and terrestrial broadcasting 
between 1.3 and 3 GHz. Note that below 1.3 GHz, use of mode II is 
suggested).

- Because provision can be made for considerable additional data 
services, user-friendly operation of receivers is possible.


DAB INTRODUCTION FOR EUROPE.
- Very likely to be introduced within  existing terrestrial bands 
from 1995

- The parallel transmission of identical programmes over FM/AM 
and DAB will probably result in a significant increase of 
expenses for broadcasting organisations without any necessary 
increase in audience. This need taking into account in the 
financial planning for DAB.

- In order to achieve better spectrum utilisation of the existing 
VHF/FM band in the future, it seems desirable to realocate at 
least a part of this band for use by digital systems. This may 
need to be the topic of a future ITU conference.

- With respect to frequency planning considerations, several DAB 
frequency blocks are necessary to cover separate neighbouring 
areas, giving one block per area. With a block-width of about 1.5 
MHz and appropriate guard bands, a total band equivalent to one 7 
MHz TV channel would generally permit an introduction of DAB 
terrestrial services.

- Satellite introduction early years next century, this requiring
considerable cordination since a number of European and other in 
Region 1 have maintained broadcasting allocation until 2007. 


SCHEDULE FOR INTRODUCTION OF DAB SERVICES

A) TERRESTRIAL DAB
End 1992  final specification of system completed

1991-1995  
* Broadcasters/Administrations takes decision  concerning Band 
  used and frequencies for DAB

* Industry prepare for mass production of DAB receivers and 
  combined FM/DAB receivers

1995-1997  Introduction of initial DAB services

1995-2000  DAB implementation period, simultaneous broadcast
of DAB and VHF/FM services plus additional DAB services only

2010 Substantial replacement of FM services by DAB  where 
appropriate


B) SATELLITE DAB.
MARCH 1992 Band allocated for DAB satellite and complementary 
terrestrial transmissions and date for band  availability agreed

END 1992  Final specification of DAB system complete

1992-1995 Broadcasters and Administrations determine frequency 
for satellite experiment in band allocated by WARC-92

1997 ESA/Industry prepares satellite mission and production of 
appropriate receivers.

1998 Expect launch of ARCHIMEDES

1998 WARC for planning BSS (Sound)

1997-2007 Technical test leading to pre-operational services for 
satellite and/or complementary terrestrial DAB services in 
conformity with  WARC-92 procedures.


Newsgroups: rec.radio.broadcasting