Introduction
|HFC-networks (see figure 1) are optimised for transport of distributed services, mainly cable-TV. For these services, data is modulated on carriers (according to today’s analogue TV-channels). An 8 MHz wide TV-channel can offer a payload data rate of 38,5 Mbit/s. Digital MPEG-2-coded video offer, on such a channel, about 4-8 TV-channels.
Figure 1. Reference model for HFC-networks.For other types of data than video, there are many alternatives. One proposition (which originate from the standardisation organisation DAVIC) aims at utilising the frame structure in MPEG-2 to place ATM-cells in it and thus being able to offer packet-oriented and circuit switched data (see figure 2).
Figure 1. Reference model for HFC-networks.For other types of data than video, there are many alternatives. One proposition (which originate from the standardisation organisation DAVIC) aims at utilising the frame structure in MPEG-2 to place ATM-cells in it and thus being able to offer packet-oriented and circuit switched data (see figure 2).
Figure 2. ATM in MPEG multiplexing.
The objective with this thesis, is to study the effectiveness in the multiplexing method described above and to comparethis method with the method of directly multiplex the ATM-cells on thedata channel (38,5 Mbit/s). Further, the possibility of multiplexing both ATM-cells and MPEG-2 data on the same data channel will be studied (see figure 3).
Figure 3. MPEG-2 multiplexing.