New York - The
revealed Tuesday several new tools that will help Mobile DTV consumer electronics manufacturers reduce the need for expensive field testing and help TV station engineers design more robust Mobile DTV systems.
At a conference here this week, the OMVC unveiled a new Predictive model for reception of UHF (channels 14 to 51) Mobile DTV signals, and has coordinated over the past several months the "capture" (or recording) of live over-the-air Mobile DTV RF signals in the Washington D.C. market.
The RF Capture Catalog is a collection of profiles that broadcasters and product developers can play back in the laboratory for more thorough analysis and evaluation of the Mobile DTV RF environment.
Different captures of RF television signals will help broadcasters determine the relative performance between the two services and their expected coverage.
The RF signal capture program was initiated in March to create a signal library that will both assist broadcasters in better understanding their reception environments and help mobile device product developers improve their products.
Meanwhile, the new Predictive model is intended to predict signal coverage in automobiles with an antenna mounted on the vehicle, in a handheld unit operating outdoors, and a handheld unit operating indoors. Broadcaster RF experts can use this new model to predict future coverage of existing or future transmit facilities.
"While there are different models used to predict broadcast signal coverage, we've opted for a â€˜semi-empirical' method that uses a blend of actual field reception data and theory. With information about the local terrain, antenna height, frequency and polarization as well as details about the receiver and atmospheric conditions, we can predict signal strength for mobile broadcasts with this model," said Anne Schelle, OMVC executive director.
The results are local maps that show where Mobile DTV reception can be expected to be robust. Subsequent field testing with automobiles showed the predictive model to accurately correlate to actual conditions.
Future iterations of the Predictive Reception model will consider the impact of elliptical or circular polarized transmission antennas, the effects of tall buildings near receivers, and details on predictive reception for VHF reception.
The OMVC.org has posted on its website a Mobile DTV Propagation study that reviews the reception characteristics of the mobile video service and details about the RF Capture program service for device manufacturers, the coalition said. It is also releasing two other documents for broadcast engineers: a recommended practices document for deployment of electronic service guides, and a presentation about the most likely broadcast scenarios for Mobile DTV services, including 11 use cases for multiple channels at varying qualities of transmission.
The OMVC said Mobile DTV is already available from 75 broadcasters and is forecasted to hit two-thirds of the viewing public over the next year, as more stations enhance their broadcast operations.
Mobile DTV broadcasts signals are designed to be transmitted alongside the HD digital TV broadcasts. But the signal qualities of Mobile DTV are different than HDTV transmissions because antennas in Mobile DTV receivers are usually lower to the ground and are always on the move, the OMVC said.
Similar to the process used in the earlier development of fixed HDTV consumer products, consumer electronics manufacturers can use recorded streams for lab testing of new Mobile DTV products, and the OMVC has been busy developing several new services that will help all parts of the ecosystem deploy the best system for local viewers, Schelle said.