What's the approximate bitrate in a Ku or Ka feed?

[tkrandall]

Specifically, what I am trying to get a feel for is how much bitrate is passing through the coax coming down from the dish when say odd or even transponders are selected? For example, 16 transponders all being tuned in at one time (which is what happens when 13v or 18v signal is sent) and feeding through the coax represents what kind of throughput?

[veryoldschool]

Specifically, what I am trying to get a feel for is how much bitrate is passing through the coax coming down from the dish when say odd or even transponders are selected? For example, 16 transponders all being tuned in at one time (which is what happens when 13v or 18v signal is sent) and feeding through the coax represents what kind of throughput?
Since at this point it's still modulated RF, bandwidth usage would seem to be more the question and there are 2 to 3 500 MHz blocks on the coax [250-750 MHz Ka-lo, 950-1450 MHz Ku, and if you have any Ka-hi 1650-2150 MHz], with a standard HD dish. With SWiM, there are only 9 100 MHz bands between just over 950 MHz and just under 1800 MHz.

[tkrandall]

Thanks VOS. The context of my question was addressed with cable providers here:

http://www.dbstalk.com/showthread.php?p=2405675#post2405675

I just was wanting a comparison of how much equivalent data is in, say, each 500 mhz chunk (16 transponders) of modulated RF coming from the dish/multiswitch.

[Jeremy W]

I just was wanting a comparison of how much equivalent data is in, say, each 500 mhz chunk (16 transponders) of modulated RF coming from the dish/multiswitch.
So look it up. All of the data you need is posted on this site, do a search for it. Why does it need to be handed to you?

[tkrandall]

I guess I just missed it then......not looking to be spoon fed anything. I thought it perhaps an interesting topic to explore.

[Jason Whiddon]

So look it up. All of the data you need is posted on this site, do a search for it. Why does it need to be handed to you?


Mature...

[doctor j]

Bit rate on KU tpn's (can't measure KA with TSReader) is about 39.9 mb/sec as i recall.

Can put up a bar graph of the various pid's from TSReader if that would help.

Doctor j

[Jeremy W]

I thought it perhaps an interesting topic to explore.
I can understand why it might seem that way. But with the vast number of differences between the two systems, any comparisons on this level are fairly useless. DirecTV can't use the spectrum as efficiently as any terrestrial provider, simply because their signal has to travel 22,300 miles through open air before it gets to you.

[evan_s]

Bit rate on KU tpn's (can't measure KA with TSReader) is about 39.9 mb/sec as i recall.

Can put up a bar graph of the various pid's from TSReader if that would help.

Doctor j

The Ka conus tps are probably in the same area currently. They generally have 5 hd channels per tp and average~8mbs each.

To figure out exactly what it you get from a TP and why you need to start with the size bandwidth of the tp. Then look at the encoding scheme which for sat is usually either qpsk or 8psk. QAM fits more data but needs a better signal than sat can provide to work effectively. Then you need to start looking at the Symbol rate and the FEC(forward error correction).

[techntrek]

Mature...

Agreed. Going with that logic everything that ever needs to be posted, has been posted, so nobody needs to ever post on here again. ;)

[Jeremy W]

Going with that logic everything that ever needs to be posted, has been posted, so nobody needs to ever post on here again.
Not even close. Grow up.

[ekgermann]

... how much bitrate is passing through the coax coming down from the dish when say odd or even transponders are selected?

laden or unladen, European or African?

[doctor j]

screen shot of TSReader capture of 101 TPN 30.

Bitrate is 30.3 mbps

Doctor j

[Scott in FL]

That's probably about right. Lyngsat.com shows the symbol rate for the 101W Ku-band transponders to be 20 Msps, FEC = 6/7: http://www.lyngsat.com/dtv101.html So doing the math, I get 31.6 Mbps per transponder. There are 32 transponders (one with FEC 2/3, but let's ignore that detail to keep it simple) and the total data rate for all Ku-band signals is just over 1 Gbps (1011 Mbps).

For the D10 Ka-band satellite at 103W, I believe they use DVB-S2, 8PSK. Lyngsat shows 30 Msps, 2/3 rate FEC http://www.lyngsat.com/dtv10.html (which does work out to 36 MHz using a rolloff factor of 20%, so I probably have it right). If I am correct, the data rate is 59.4 Mbps. Lyngsat shows 17 transponders, so a total of just over 1 Gbps again (1009 Mbps).

The Spaceway 1 Ka-band satellite at 103W has 6 transponders at 66.8 Mbps per transponder. http://www.lyngsat.com/space1.html Total = 400 Mbps.

Lyngsat shows very little information on the Ka-band satellites at 99W:
http://www.lyngsat.com/space2.html
http://www.lyngsat.com/dtv11.html

[Jeremy W]

For the D10 Ka-band satellite at 103W, I believe they use DVB-S2, 8PSK. Lyngsat shows 30 Msps, 2/3 rate FEC http://www.lyngsat.com/dtv10.html (which does work out to 36 MHz using a rolloff factor of 20%, so I probably have it right). If I am correct, the data rate is 59.4 Mbps.
I'm horrible at math, so I can't tell you what's wrong with your figuring, but it's not correct. The bitrate for a single Ka transponder is closer to 40 Mbps, nowhere near 59.4 Mbps. They could stick 2-3 more channels on each transponder if that were the bitrate!

[veryoldschool]

I'm horrible at math, so I can't tell you what's wrong with your figuring, but it's not correct. The bitrate for a single Ka transponder is closer to 40 Mbps, nowhere near 59.4 Mbps. They could stick 2-3 more channels on each transponder if that were the bitrate!
I don't think this can be the case, since I've got 7 HD channels coming off one Ka TP.

[Jeremy W]

I don't think this can be the case, since I've got 7 HD channels coming off one Ka TP.
What satellite and transponder? A quick glance at the list doesn't show any Ka transponders with more than 5 actual HD channels.

[Scott in FL]

I'm horrible at math, so I can't tell you what's wrong with your figuring, but it's not correct. The bitrate for a single Ka transponder is closer to 40 Mbps, nowhere near 59.4 Mbps.

My assumptions may be incorrect, but there's nothing wrong with my figuring. Because DVB-S2 calculations are so complicated, I cheat and use a calculator. Newtec's can be found on line here: http://www.newtec.eu/library/dvb-s2-calculator/ I can tell you from working with this calculator just about every day at work for over 2 years, it is correct.

Now for my assumptions. Lyngsat says the symbol rate is 30 Msps, 2/3 rate. They're usually correct.

I believe the Ka-band signals use 8PSK. Plug all that into the calculator and you get 59.4 Mbps.

I did see a presentation once stating that Directv uses the DVB-S2 pilots to combat rain fade. If true, the data rate would be just over 58 Mbps.

And I believe the input to the modulator is TS over IP, which would indicate encapsulation. That would drop it down to about 57 Mbps.

I wonder where the OP would have found all this in previous posts???

[Davenlr]

What satellite and transponder? A quick glance at the list doesn't show any Ka transponders with more than 5 actual HD channels.

Check the spot beams.

[tkrandall]

You guys are getting over my head with the signal protocols, etc :) but I do appreciate the bottom line information.

[veryoldschool]

What satellite and transponder? A quick glance at the list doesn't show any Ka transponders with more than 5 actual HD channels.
When they were on the Spaceways, it was one TP, but looking on the list now, they're on D11 and 5 on one TP 23 and 2 on TP 15.

[evan_s]

for the ka beams I believe they use 8psk for the spots and qpsk for the conus. So those calcs and 7 channels seems right for spots but not for conus.

[P Smith]

for the ka beams I believe they use 8psk for the spots and qpsk for the conus. So those calcs and 7 channels seems right for spots but not for conus.
And your facts are ? To support your theory...

[doctor j]

The KA Spaceway spotbeams are also much wider bandwidth.
Will have to research source but fuzzy recollection is about 1 1/2 the CONUS bandwidth. Thus no problem with 7 - 9 HD LIL's per TPN.

Doctor j

[Jeremy W]

I wonder where the OP would have found all this in previous posts???
The correct info could have been found by doing a search. I know this because I've participated in at least one thread where this topic has come up in the past.

[Scott in FL]

This is correct:

DVB-S2, 8PSK, 30 Msps, 2/3 rate FEC yields 59.4 Mbps (pilots off, no encapsulation).

DVB-S2, QPSK, 30 Msps, 2/3 rate FEC yields 39.7 Mbps (pilots off, no encapsulation).

Not sure why you had to be so rough on the OP. After all, this is a forum to share information.

[Jeremy W]

Not sure why you had to be so rough on the OP. After all, this is a forum to share information.
Then why does the search function exist?

[tkrandall]

This is correct:

DVB-S2, 8PSK, 30 Msps, 2/3 rate FEC yields 59.4 Mbps (pilots off, no encapsulation).

DVB-S2, QPSK, 30 Msps, 2/3 rate FEC yields 39.7 Mbps (pilots off, no encapsulation).

Not sure why you had to be so rough on the OP. After all, this is a forum to share information.


For D10 and D11, is not the latter (DVB-S2, QPSK, 30 Msps, 2/3 rate FEC) what is employed by DirecTV? I thought I read DirecTV was not using 8PSK. Are they now?

[P Smith]

For D10 and D11, is not the latter (DVB-S2, QPSK, 30 Msps, 2/3 rate FEC) what is employed by DirecTV? I did not think they were using 8PSK.

If you'll [think ;)] it will come close to real info.

[evan_s]

For D10 and D11, is not the latter (DVB-S2, QPSK, 30 Msps, 2/3 rate FEC) what is employed by DirecTV? I thought I read DirecTV was not using 8PSK. Are they now?

I believe they actually use both. QPSK on the Conus tps and 8PSK on the spots which is how some spots have 7 or 8 channels on a single TP.

[P Smith]

I believe they actually use both. QPSK on the Conus tps and 8PSK on the spots which is how some spots have 7 or 8 channels on a single TP.

I have a knowledge that all Ka sats using DVB-S2/8PSK modulation/30 Msps with different FEC.

[tkrandall]

...with vary SR.

Sorry - but can you translate that last part?

[P Smith]

Sorry, Different FEC; between transponders and in time.

[evan_s]

I have a knowledge that all Ka sats using DVB-S2/8PSK modulation/30 Msps with different FEC.

I can't dispute that but if that is the case something doesn't seem to add up with the Conus Tps. It's fairly easy to establish with MRV or DirecTV2PC that most HD channels seem to average ~8mbs. With 5 channels per TP this nicely matches up with ~40mbs bandwidth per tp. If they are using 8psk on the conus tps there seems to either be a lot of overhead someplace or a lot of bandwidth left unused (which I highly doubt). Can you offer any insight on this seeming inconsistency?

[P Smith]

Not before I'll see PID's distribution in the mux.

[veryoldschool]

I can't dispute that but if that is the case something doesn't seem to add up with the Conus Tps. It's fairly easy to establish with MRV or DirecTV2PC that most HD channels seem to average ~8mbs. With 5 channels per TP this nicely matches up with ~40mbs bandwidth per tp. If they are using 8psk on the conus tps there seems to either be a lot of overhead someplace or a lot of bandwidth left unused (which I highly doubt). Can you offer any insight on this seeming inconsistency?
There does seem to be differences between the Spaceways and the D10/11 tps.
When my locals came off spaceways, all 7 HD channels were on one TP, but when they were moved to D10 or 11, they now are on 2 TPs. 5 on one and two on another.

[evan_s]

The spaceway Tps are larger so I'd expect there to be more channels per tp.

"For D10 and D11, Ka transponders are numbered 1-24, and are 40mhz wide with 36mhz usable. S1 and S2 can be operated as eight transponders 62.5mhz wide"

http://www.dbstalk.com/showthread.php?p=869690#post869690