The Repack s Impact on Reception

This month I decided to take a break from talking about TV transmission to focus on TV reception. I receive emails from non-engineers with questions about TV transmission and reception who happen to stumble upon my articles.

People are starting to realize the incentive auction and repack will impact viewers' TV reception. This month I'll explain the impact of the incentive auction, channel sharing and the repack on over-the-air TV reception.

Stations may sell their spectrum and go away, meaning the programming they carried may no longer be available. Stations may sell their spectrum and channel share with another station. These stations' primary channels will be available on another channel, perhaps at reduced quality, but some multicast channels on either of the stations sharing the channel may disappear.

Viewers who watch TV via translators or over LPTV stations may find they are no longer available. Finally, during repacking, stations' coverage may change, temporarily or permanently, making reception more difficult in some areas.

Will your favorite DTV program channel disappear after the incentive auction? In part, that will depend on that channel's popularity and viewership. When talking about channels, it is easy to get confused. A station has only one RF channel (their spectrum), but may run several virtual program channels on it-28.1, 28.2, 28.3, 28.4. These are transmitted in the same spectrum, but each takes some of the data bandwidth.

While stations can't discuss their auction plans during the FCC's quiet period, the value of the spectrum versus the value of the programming will likely determine whether or not the program channel survives the auction.

CHANNEL SHARING MISUNDERSTOOD

Stations can sell their spectrum, but retain their license, through channel sharing. This is probably the most misunderstood aspect of the incentive auction. First, stations are not, strictly speaking, sharing spectrum. The sharee station has no spectrum; the sharer has 6 MHz, one full channel. An ATSC DTV channel cannot be less than 6 MHz. It cannot be divided. What can be divided is the data rate transmitted on that channel-19.392 Mbps.

Viewers watching two or more stations sharing a channel are likely to notice some reduction in picture quality. How noticeable it is will depend on the total number of program streams sharing one RF channel; how many of the program streams are in HD; the way the bits are allocated between program streams; and the content on the channel.

In the early days of legacy ATSC, expert OTA viewers used TSReader software to see what bit rate stations were using to transmit their HDTV programs. Stations that sacrificed HDTV bit rates to add additional program streams were criticized. Now that some stations are transmitting two HDTV program streams and one or two SD program streams in the same 19.392 Mbps, most stations have at least one SD multicast, but there don't seem to be as many complaints. Why?

Fig. 1: Statistical multiplexing bandwidth allotment

LINK:	http://www.tvtechnology.com/resources/0006/the-repacks-impact-on-recep...
	See more stories from tvtechnology

Most recent headlines