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Boston’s WGBH uses Grass Valley platform for mobile video service

WGBH, the public broadcaster in Boston and the leading producer for PBS, has installed a new ATSC A/153-compliant mobile video transmission system from Grass Valley to support the station’s mobile video service, which was launched in late 2009, and additional channels added earlier this year.

In addition to its main HD DTV channel, the station is simulcasting two mobile DTV channels: its primary signal plus the "GBH Kids" channel. WGBH is also rebroadcasting its radio services 89.7 WGBH and 99.5 All Classical in mobile as part of its 6MHz of digital television spectrum.

Joe Igoe, chief technology officer for WGBH, said Grass Valley’s statistical multiplexing for mobile DTV allow his staff to offer more of educational services at a higher quality level than would be otherwise possible. The station plans to offer additional mobile DTV services as the market develops.

WGBH is a longtime Grass Valley customer, and now operates several Grass Valley K2 media servers and other equipment. The station currently operates a two-tube DCX Paragon MSDC-IOT transmitter, which includes the new Adapt IV exciter that has been retrofitted for simultaneous ATSC terrestrial and mobile video operation. WGBH’s sister station WGBX operates a DCX Millennium single-tube transmitter to broadcast its on-air signal.

ATSC mobile DTV terrestrial broadcast technology from Grass Valley is backward compatible with legacy ATSC transmission systems, enabling stations to use their existing DTV channel and the mandated ATSC 8-VSB modulation scheme. The technology offers several significant technological advantages over other systems, including the use of M/H block coding to provide maximum capability for signal reception.

The basic equipment needed to begin broadcasting mobile video services via ATSC mobile DTV includes program encoders, a multiplexer, an ESG guide server, and a compatible DTV transmission exciter. Each of these devices is now available in field-tested production models from Grass Valley.

Grass Valley offers an end-to-end mobile DTV video solution. The WGBH installation includes a new Adapt IV Exciter with mobility software, a NetProcessor 9030, a Jade ESG server, two new ViBE mobility encoders in a statistical multiplexing mode, two ViBE audio encoders, and an Amethyst smart switch for redundancy. Grass Valley engineers handled all equipment installation and commissioning.