3.3.1 Network scenario’s
Since the results and conclusions of this ReDeSign study should reflect the European cable networks, it is most crucial to use representative networks that cover somehow the range of European networks. In the ReDeSign Deliverable 6, the Reference Architectures Report, we have specified a number of coaxial architectures. However, because of the large variation in coaxial architectures found in Europe, these reference architectures specify ranges for net- work parameters. The reference architectures lacked sufficiently specified network figures that could be used in the calculation. Therefore, we have sought a close cooperation with some cable operators that were willing to share their network information with the ReDeSign project. Since the information is confidential, we only provide an anonymous summary of the cascades.
The reference architecture or reference cascade specifies the worst-case cascades that can be found in the real network. It specifies the node and all the amplifiers and the maximum signal attenuation between two subsequent amplifiers or between the end amplifier and the customer wall outlet. When building a network, the reference architecture is “projected” or “mapped” on the geographical topology in terms of streets, homes, railways, rivers etc of a neighborhood. This projecting or mapping yields the detail topological network lay out in terms of the sites of the optical node and the amplifiers, the number of sub-branches fed by a
node or amplifier and the length of the coaxial cable connecting the node with the first am- plifiers, the following consecutive amplifiers and the end amplifier with the customer outlet. Because of the above process of mapping the reference cascade, each home connection will be unique. As a rule, the signal loss between two consecutive amplifiers, or between the end amplifier and the customer wall outlet will be less than specified by the reference architec- ture. As a result, the quality of the signal delivered at the customer wall outlet will be better than the signal quality of the reference architecture, or at least equal. The reference architec- ture thus specifies the worst-case home connection. All home connections will have a signal with a quality equal or better than that of the reference cascade.
Figure 15 Specification of coaxial cascade. The gain and loss values indicated in the figure are cho-
sen arbitrary.
For the studies we have used four reference cascades with a different number of amplifiers: an optical node with respectively 2, 4, 5 and 15 amplifiers. Each section encompasses an amplifier (or the node) and the coaxial network connecting to the subsequent amplifier or to the customer wall outlet.
Table 8 Summary of the ReDeSign Reference Cascades used in this study.
Node + 2 Amplifiers
Section 1
Section 2
Section 3
UCS0=-60dBc / UCTB=-60dBc 110 107 107
Loss @ 862 MHz 30 30 30
Node + 4 Amplifiers
Section 1
Section 2-4
Section 5
UCS0=-60dBc / UCTB=-60dBc 113 110 100
Loss @ 862 MHz 32 32 19
Node + 5 Amplifiers
Section 1
Section 2-5
Section 6
UCS0=-60dBc / UCTB=-60dBc 110? 115 104
Loss @ 862 MHz 22 28 30
Node + 15 Amplifiers
Section 1
Section 2-11
Section 13-16
UCS0=-60dBc / UCTB=-60dBc 113 115 113 Loss @ 862 MHz 29 29 36 30 dB -30 dB 30 dB -30 dB 30 dB -30 dB 30 dB 30 dB -30 dB 30 dB 40 dB - 40 dB system outlet system inlet
+ slope + slope + slope
+ slope + slope 30 dB -30 dB 30 dB -30 dB 30 dB -30 dB 30 dB 30 dB -30 dB 30 dB 40 dB - 40 dB system outlet system inlet
+ slope + slope + slope
+ slope + slope Section 30 dB -30 dB 30 dB -30 dB 30 dB -30 dB 30 dB 30 dB -30 dB 30 dB 40 dB - 40 dB system outlet system inlet
+ slope + slope + slope
+ slope + slope 30 dB -30 dB 30 dB -30 dB 30 dB -30 dB 30 dB 30 dB -30 dB 30 dB 40 dB - 40 dB system outlet system inlet
+ slope + slope + slope
+ slope + slope
Figure 15 shows a cascade of a number of sections. For each section the following figures were specified:
• Node/amplifier: o Noise figure
o Worst case CSO and CTB values as specified in the IEC 60728 • Coaxial part of the segment:
o Maximum branching loss associated with splitters or multitaps as specified by the reference cascade
o Maximum coaxial loss at the frequencies of 200 MHz and 862 MHz as speci- fied by the reference cascade.
Table 8 gives a summary of the 4 reference cascades used in this study. This specification is not complete, but it gives an indication of the cascades.
3.3.2 Network load scenario’s
Next, in Table 9 we have specified the network loads that we have used for the simulations. In all cases we used a load of 93 equidistant channels of 8 MHz for PAL, DVB-C or DVB-C2 channels. As a rule, the PAL channels were placed at the low frequency side, the DVB –C2 channels at the high frequency and the DVB-C channels in the middle. In addition, the load included 25 FM radio channels located in the 87 – 108,5 MHz FM band.
Throughout the simulations, the same signal levels delivered to the customer wall outlet for FM radio, PAL TV and DVB-C were used. In contrast, the signal level of the DVB-C2 carriers was varied over a large range. As shown in the table, a DVB-C signal level with a 4 dB back- off with reference to the PAL carrier level was used. Similarly, a 10 dB back off was applied for the FM signal level.
Table 9 ReDeSign network load, signal levels and cumulative digital capacity
Network Load
Frequen- cy edgeDigital Capacity
Scenario FM PAL DVB-C 256 QAM DVB- C2 DVB-C2 1024 QAM DVB-C2 4096 QAM Reference 25 40 53 - 865 MHz 2,7 2,7 Scenario A 25 20 30 43 865 MHz 4,5 5,1 Scenario B 25 0 15 78 865 MHz 6,2 7,3 Signal level @ outlet dBµV 59 69 65 50 - 80The simulations were configured such that a flat spectrum was delivered at the customer wall outlet. Similarly, a flat spectrum was delivered to the input port of each amplifier of the cas- cade. To this end, a sloped amplifier gain was applied which results in a sloped output spec- trum with carrier levels that gradually increase for higher frequencies.
An absolute PAL signal level of 69 dBµV was chosen, which is somewhat higher than usually delivered by the operators. However, one should note that this value refers to the level at the input port of the wall outlet, so, at the TV output socket a 3 dB weaker signal will be deli- vered.