– Mixed/hybrid – Cable distribution Allows the use of the same band as terrestrial sound broadcasting (mixed) as well as the use of terrestrial onchannel repeaters to reinforce the satellite coverage (hybrid) resulting in all these channels being received transparently by a common receiver. Signal can be carried transparently by cable Allows the use of the same band as terrestrial sound broadcasting (mixed) as well as the use of terrestrial on-channel repeaters to reinforce the satellite coverage (hybrid) resulting in all these channels being received transparently by a common receiver. Signal can be carried transparently by cable Signal can be carried transparently by cable Signal can be carried transparently by cable TABLE 1 (continued) Characteristics from Recommendation ITU-R BS.774 (condensed wording) Digital System A Digital System F Digital System C Digital System G
10.2 BER vs. S/N (in 1.5 MHz) in a Rayleigh channel simulated in urban environment Measurements of BER vs. S/N were made on the data channels, using a fading channel simulator. The Rayleigh channel simulations correspond to Fig. 5 in Cost 207 documentation (typical urban area, 0-0.5 s) and the receiver travelling at a speed of 15 km/h. The results are shown in Figs 10 and 11. FIGURE 10 BER vs. S/N for System A (Transmission Mode I, 226 MHz) FIGURE 11 BER vs. S/N for System A (Transmission Mode II, 1 480 MHz) 10.3 BER vs. S/N (in 1.5 MHz) in a Rayleigh channel simulated in rural environment Measurements of BER vs. S/N were made on the data channels using a fading channel simulator. The Rayleigh channel simulations correspond to Fig. 4 in Cost 207 documentation (rural area, nonhilly, 0-5 s) and the receiver travelling at 130 km/h. The results are shown in Figs 12 and 13. FIGURE 12 BER vs. S/N for System A (Transmission Mode I, 226 MHz) FIGURE 13 BER vs. S/N for System A (Transmission Mode II, 1 480 MHz) 10.4 Sound quality versus RF S/N A number of subjective assessments have been performed in to evaluate the sound quality versus the S/N. The transmission path included equipment for establishing the S/N in a Gaussian channel and, using a fading channel simulator, in a Rayleigh channel. Two different simulation “models” were used in the case of a Rayleigh channel, the same as those described in §§ 10.2 and 10.3. In each case a listening test was conducted in which the average S/N was reduced in 0.5 dB steps to establish, in sequence, the following two conditions: – the onset of impairment, which is the point at which the effects of errors start to become noticeable. This was defined as the point where 3 or 4 error-related events could be heard in a period of about 30 s; – the point of failure, which is the point at which a listener would probably stop listening to the programme because it became unintelligible or because it no longer provided the
6 Spectrum for extended hybrid mode The extended hybrid waveform is created by adding primary extended sidebands to the PM sidebands present in the hybrid waveform. Depending on the service mode, one, two, or four frequency partitions can be to the inner edge of each PM sideband. Each PM sideband consists of ten frequency partitions and an additional reference subcarrier spanning subcarriers 356 through 546, or 356 through 546. The upper primary extended sidebands include subcarriers 337 through 355 (one frequency partition), 318 through 355 (two frequency partitions) or 280 through 355 (four frequency partitions). The lower primary extended sidebands include subcarriers 337 through 355 (one frequency partition), 318 through 355 (two frequency partitions) or 280 through 355 (four frequency partitions). The subcarriers within primary extended sidebands are uniformly scaled the same amplitude scale factor, a0, as the PM sidebands (see Fig. 33 and Table 18). FIGURE 33 Spectrum of the extended hybrid waveform – Service modes MP2 through MP4 (The of the digital subcarriers is such that the total power of these carriers is 20 dB below the nominal power of the FM analogue carrier) TABLE 18 Extended hybrid waveform spectral summary – service modes MP2 through MP4 Sideband Number of frequency partitions Frequency partition ordering Subcarrier Subcarrier frequencies (from channel centre) (Hz) Amplitude scale factor Frequency span (Hz) Comments PM 10 A 356 to 546 129 361 to 198 402 a0 69 041 Includes additional reference subcarrier 546 PM 10 B 356 to 546 129 361 to 198 402 a0 69 041 Includes additional reference subcarrier 546 primary extended (1 frequency partition) 1 A 337 to 355 122 457 to 128 997 a0 6 540 None Lower primary extended (1 frequency partition) 1 B 337 to 355 122 457 to 128 997 a0 6 540 None