Q 2.25-1 Jacek Pawlowski , How many SD/HD channels can we get from one transponder?
Number of channels supported by a satellite transponder depends on numerous variables:
TV transmission standard – standard definition (SD) or high definition (HD);
Satellite transmission standard: DVB-S or DVB-S2;
Video compression standard: MPEG-2 or MPEG-4;
Permissible modulation and coding schemes: QPSK, 8PSK, etc. as defined in the chosen standard.
Traditional SD quality transmissions tend to use MPEG-2/DVB-S combination; more recent introductions particularly in support of HD use MPEG-4/DVB-S2.
Consider an example.
Video bit rates of 4 Mb/s for MPEG-2/SD and 10 Mb/s for MPEG-4/HD;
Transmission symbol rate = 26 Ms/s (that fills a 36 MHZ transponder);
Coding rates = respectively ½ and 7/8;
The corresponding numbers of SD TV channels in a 36 MHz transponder are estimated as 6 and 11 respectively, reducing respectively to 2 and 4 HD channels (Ref 2.25).
Since bandwidth = Symbol rate*(1+roll off factor),
With a typical roll-off of 0.35, corresponding bandwidth at 26 Ms/s = 35.1 MHz, adequate to fill a 36 MHz transponder.
Available: http://www.tele-audiovision.com/TELE-satellite-1107/eng/sdinhd.pdf, retrieved 3/3/2018.