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HD TV link budget

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Ex Member
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May 12th, 2011 at 8:54pm  
Hi,

could any body help me to know how i can decide the needed antenna size, HPA power and the needed Bandwidth for HD sport channel in the KU band?
also which better use MPEG2/DVBS or MPEG4/DVBS2
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Eric Johnston
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Reply #1 - May 13th, 2011 at 8:58am  
As a first approximation just try to get an uplink C/N of about 23 dB. This assumes that your far end receive-only sites are small diameter.

Find the satellite uplink beam G/T using an uplink beam coverage map and your location.
Put this into a link budget calculator e.g. http://www.satsig.net/satellite-tv-budget.htm

Concentrate only on the uplink link budget for the purposes of this very initial analysis.

Try many different uplink dish size dishes and HPA powers and bandwidths, always adjusting the values to get the same uplink C/N = 23 dB (you can try other values, between say 15 dB to 25 dB).

Learn these by experiment:
You will find that different bandwidths all have the same uplink eirp per MHz.
You will find that a larger dish needs less HPA power to get the same uplink eirp.

The bandwidth you need depends on the symbol rate. See http://www.satsig.net/symbol01.htm
Occupied bandwidth is the -10 dB bandwidth of the carrier (approx 1.19 x Symbol rate).
Allocated bandwidth is what you pay for (approx 1.35 x Symbol rate)

Symbol rate depends on transmission bit rate and modulation method (QPSK, 8-PSK, 16-QAM etc).  

Transmission bit rate depends on information bit rate plus FEC overhead.

Information rate depends on the TV picture/sound quality that you want.

MPEG2 needs more bit rate than MPEG4 for the same picture quality.

DVB-S uses QPSK and a limited range of FEC rate options. DVB-S2 has many possible modulation and FEC methods.  The most efficient systems, in terms of bandwidth, need a high overall C/N and thus need either larger receive dishes or a very powerful satellite. Make sure your customers will have suitable receivers if you choose DVB-S2/MPEG4.

Once you have a good understanding as above contact a satellite operator with specific proposals. They will help you with complete link budgets (uplink+downlink).

Do consider sub-contracting the entire uplinking job to some exiting teleport with large uplink dish facilities for your chosen satellite.

Best regards, Eric.
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« Last Edit: May 13th, 2011 at 12:44pm by Admin1 »  
 
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Reply #2 - May 14th, 2011 at 1:49am  
thank you eric Smiley.

the final question is do you have an approximate values for the minimum bandwidth for the HD TV for MPEG4/DVBS2?

Thanks
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Eric Johnston
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Reply #3 - May 14th, 2011 at 11:12am  
The low bandwidth is associated with low picture quality options in MPEG-4 and highest density modulation method and minimal FEC in DVB-S2.

This extreme concept only seems appropriate to me for a point to point link providing low quality TV towards a large earth station receive site. Who wants that ?

Read more:
http://en.wikipedia.org/wiki/DVB-S2
http://en.wikipedia.org/wiki/MPEG-4
There are links here to the more detailed technical aspects and vast number of options.

If your service is intended for general domestic reception, a most important factor will be the ability of those customers to receive the signal without having to buy expensive PLL LNBs, new satellite TV set top boxes and large antennas. You may well decide to use a less efficient system in terms of satellite bandwidth and spend more on the satellite capacity in order to reduce costs to the end user receive-only customers.

Go and talk to existing satellite TV uplinking teleports and ask about combining your programme into one of their big carriers.

You might also consider IP-TV distributed as part of the VSAT outlink data carrier. This may be suitable if you have a limited number of VSAT receive sites.

Best regards, Eric.
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« Last Edit: May 14th, 2011 at 12:52pm by Admin1 »  
 
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