Jump to content


Welcome to DBSTalk


Sign In 

Create Account
Welcome to DBSTalk. Our community covers all aspects of video delivery solutions including: Direct Broadcast Satellite (DBS), Cable Television, and Internet Protocol Television (IPTV). We also have forums to discuss popular television programs, home theater equipment, and internet streaming service providers. Members of our community include experts who can help you solve technical problems, industry professionals, company representatives, and novices who are here to learn.

Like most online communities you must register to view or post in our community. Sign-up is a free and simple process that requires minimal information. Be a part of our community by signing in or creating an account. The Digital Bit Stream starts here!
  • Reply to existing topics or start a discussion of your own
  • Subscribe to topics and forums and get email updates
  • Send private personal messages (PM) to other forum members
  • Customize your profile page and make new friends
 
Guest Message by DevFuse

Photo

QPSK vs. 8PSK in Standard Definition


  • Please log in to reply
3 replies to this topic

#1 OFFLINE   Mark Holtz

Mark Holtz

    Day Sleeper

  • DBSTalk Club
  • 9,938 posts
  • LocationSacramento, CA
Joined: Mar 23, 2002

Posted 16 February 2004 - 02:27 PM

Okay, pardon my ignorance and if I got the terms off, but...

In the past, I thought that QPSK and 8PSK was the method of compressing HD channels, and that Dish was converting over to 8PSK in order to get three HD channels on a transponder instead of two.

Now, I read somewhere that the recent receivers receive the SD material in QPSK, but are capable of 8PSK for additional compression without loss of quality.

Is this correct? How long has this been true?

"In an effort to increase your cable and satellite bills beyond the point of affordability and to further pad the pockets of our executives..."
Check out my list of links.


...Ads Help To Support This Site...

#2 OFFLINE   boba

boba

    Hall Of Fame

  • Registered
  • 5,580 posts
Joined: May 23, 2003

Posted 16 February 2004 - 02:41 PM

Since about mid November. All new DISH products have the 8psk built in 111,311,322,522 and HDs have the capability so at sometime in the future there may be an upgrade. Right now I certainly wouldn't trade my 301 in for a 111, that is about the only use I can figure for a 111 it is a no feature receiver DISH wants $100 for.

#3 OFFLINE   rvd420

rvd420

    Legend

  • Registered
  • 124 posts
Joined: Mar 10, 2003

Posted 16 February 2004 - 05:20 PM

Okay, pardon my ignorance and if I got the terms off, but...

In the past, I thought that QPSK and 8PSK was the method of compressing HD channels, and that Dish was converting over to 8PSK in order to get three HD channels on a transponder instead of two.

Now, I read somewhere that the recent receivers receive the SD material in QPSK, but are capable of 8PSK for additional compression without loss of quality.

Is this correct? How long has this been true?


QPSK and 8PSK are signal modulation schemes.

A way to look at it is look at computer ram.
SDRAM would be QPSK.
DDR RAM would be 8PSK.

But there is a catch to 8PSK.
You need to run a higher FEC to maintain the data intgerity.
So in real world application you only get a 33% increase of bandwidth.

An example would be on a normal QPSK TP both providers usually run up to 12 channles per TP.

With 8PSK they could squeeze 16 channels at the same data rate and PQ on the smae TP.


I hope that explains it.

#4 OFFLINE   Mark Holtz

Mark Holtz

    Day Sleeper

  • Topic Starter
  • DBSTalk Club
  • 9,938 posts
  • LocationSacramento, CA
Joined: Mar 23, 2002

Posted 16 February 2004 - 06:47 PM

What about the DirecTV receivers?

"In an effort to increase your cable and satellite bills beyond the point of affordability and to further pad the pockets of our executives..."
Check out my list of links.





Protected By... spam firewall...And...