1 Type of Question

Task-oriented Question that should result in one or more Recommendations and in liaison statements to the appropriate ITU-T and ITU-R Study Groups.

2 Motivation

ITU-T has issued a comprehensive set of Recommendations defining the form and structure of digital signals carried in plesiochronous networks, on the synchronous digital hierarchy (SDH), and on Broadband Integrated Services Digital Networks, in which the signals are transported in an Asynchronous Transfer Mode (ATM).

Both sound-programme and television signals can be carried on such digital networks. It now remains to specify the requirements for the transmission of MPEG-2 multiplexes of television and sound programme signals carried on PDH and SDH links. In course of the conversion of TV broadcasting distributive networks to the digital mode of operation a question is frequently raised on how to organize MPEG-2 signals transmission over PDH/SDH networks. ITU-T has approved Recommendations J.131 and J.132, containing the description of procedures needed for MPEG-2 signals conversion into PDH and SDH formats correspondingly based on ATM technology. Meanwhile, certain problems the solution for which is not covered by the said Recommendations arise in countries where there is no dedicated specialized network for distributing TV broadcasting programs (e.g., a digital satellite or cable distributive TV network for MPEG-2). This leads to the necessity to include digital TV programs signals into multiplex PDH/SDH digital streams, which besides TV signals contain also multichannel digital telephony and data signals. In short, the abovementioned problems arise when a TV distributive network is based on an extensive terrestrial PDH/SDH network including digital radio relay lines and fiber-optic lines covering thousands of kilometers.

The problem mentioned before may be solved by forming and transmitting TV signal in an Nx2,048 (N = 4 to 16) format, i.e., as a set of standard digital 2,048 Mbps E1 PDH streams. In such a case, e.g., an 8,448 Mbps E2 TV signal will be transmitted as four 2,048 Mbps E1 streams. Presently existing PDH networks are as a common practice using 16xE1 multiplexer (in most cases to combine 2,048 Mbps E1 multichannel telephony digital streams). A format for digital transmission of a Nx2,048 (N = 4 to 16) Mbps TV signal will allow joint digital transmission of TV and multichannel telephony on the basis of this unified multiplexer without any additional hardware.

3 Questions

• What are the network characteristics required for carrying digital sound-programme and television signals on PDH and SDH networks for purposes of programme contribution or primary distribution?

• What are the service and performance requirements applicable to the transmission of MPEG-2 multiplexes of television and sound programme signals in the NxE1 PDH (N = 4 to 16) format over PDH and SDH networks?

• What Application Programming Interfaces (APIs) should be foreseen for the software-based solution of MPEG-2/PDH (MPEG-2/SDH) conversion in TV coders and decoders?

• What benefits and constraints would be offered by ATM techniques when applied to digital sound-programme and television signals?

• How could a coded digital sound-programme or television signal be most effectively adapted to and from the ATM?

Studies will be presented in the form of Recommendations, to be adopted, depending on incoming contributions, by the year 2003 and beyond.

The work must be carried out in close cooperation with ITU-T Study Group 15, which has responsibilities for Recommendations on PDH (e.g. G.730, 740, 750-series), SDH (e.g. G.707, G.780-series) and the associated source signal mappings, including those for sound-programme and television broadcasting

Liaison with ITU-R Study Group 6, is also necessary in the study of this Question.