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Directv Press Release DVB-2

4K views 22 replies 13 participants last post by  dduitsman 
DVB-S2 is something you don't hear much about in this forum, and I applaud DirecTV for taking the leap and adopting it (the "other" company isn't using it). The article mentioned a 30% performance improvement over DVB-S, and this is true. What it means to us is more HD channels and less rain fade at Ka band. DVB-S2 allows MPEG-4 compression for HD and pilots to recover the signal during high noise conditions (rain fade).

So far DirecTV is using DVB-S2 for some of the locals. The problem with DVB-S2 is it's not compatible with the older DVB-S receivers, so they have to replace all of the older receivers before they can implement DVB-S2 across the board. This is the main reason Dish has so far chosen to not use DVB-S2.
 
tkrandall said:
But why would Dish not use it on their newest MPEG-4 receivers?
Don't know. When I was at the NAB show in April I walked over to the Echostar booth and asked if Dish had any plans to implement DVB-S2. The person I spoke to said no, because it was too expensive to change out the existing receivers.

The pilots used with DVB-S2 can not eliminate rain fade, only help. Ka-Band is more susceptible to rain fade than Ku-Band, so the DVB-S2 pilots help keep Ka-Band on par with Ku. But they can't eliminate it completely.
 
dduitsman said:
Scott and/or others,

What are pilots in this context?

Thanks,
Dave
Pilots, or more correctly pilot symbols, consist of additional information which the receiver uses to help lock onto the carrier. That's a very simplified description.

The pilots are inserted into the DVB-S2 frame structure along with the data (video and audio information).

DVB-S2 allows the use of higher order modulation compared to DVB-S which allowed only QPSK. These higher order modulations (8PSK, 16APSK and 32APSK) require LNBs with high stability and low phase noise. In short, DVB-S2 can not get away with the cheaper LNBs now used by DVB-S. These pilot symbols give the receiver something to lock onto.

Another example is during rain fade when the C/N drops (signal falls into the noise). The pilots help the receiver hang in there a bit longer before losing lock.
 
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