Layered Division Multiplex (LDM) is an optional technology of the new ATSC 3.0 Physical Layer standard. It allows transmitting two signals over a single RF channel. One signal (the Core Layer) is addressing receivers with difficult receiving conditions (e.g. indoor or mobile) because it is very robust, but offers a limited bandwidth. The other signal (the Enhancement Layer) is targeting receivers in good receiving conditions (e.g. roof antennas) as it is less robust, but offers a higher bandwidth. This two-layer technique allows ATSC 3.0 to address all receiving conditions (indoor, mobile, fixed) within a single channel This is a key benefit of ATSC 3.0 as it always providing the best trade-off in terms of robustness and capacity.
ATSC 3.0 is well suited to transmission of hierarchically encoded audio and video (using the SHVC codec) where a base signal (e.g. an HD signal) is carried in the Core layer while an enhancement signal (e.g. the enhancement from HD to UHD) is carried in the Enhancement Layer. With this technique, receivers can display a HD picture when the conditions are difficult and UHD when they get better. Beyond of this hierarchical encoding case, new use cases exist for this LDM feature for receivers in difficult receiving conditions that must be addressed over a regular TV channel without using additional frequencies. A potential for monetization exists there.
TeamCast’s ATSC 3.0 Vortex II exciter is already in use across the USA for powering ATSC 3.0 pilot projects and many other projects linked to the Spectrum Repack, where its dual cast capability (ATSC 1.0 today, ready to switch to ATSC 3.0 tomorrow) is a key feature.
With the latest software upgrade now released, Vortex II now supports the LDM waveform modulation. Several pilot projects are planning to evaluate LDM in the real world. Among them there is the project sponsored by the National Association of Broadcasters (NAB) & the Consumer Technology Association (CTA) in Cleveland (OHIO - USA). The Comark transmitter there has been recently upgraded with a Vortex II and is now ready for field evaluation of LDM.
“We’re excited to continue to empower the field testing of the amazingly rich ATSC 3.0 technology with our Vortex exciter” states Eric Pinson, Business Unit Manager at TeamCast.
“The introduction of LDM as a simple software upgrade demonstrates this exciter is continuously evolving in the direction the broadcasters may expect, as a future proof investment, even beyond its dual ATSC 1.0 / 3.0 feature” adds Eric.
TeamCast VORTEX II comes as the second generation of DualCast ATSC 1.0/3.0 rack exciter designed by TeamCast. The very last software release allows Broadcasters to conduct field trials of the advanced configuration profiles including Multiple PLPs, Multi-Subframes and LDM waveform. VORTEX II features specific functionalities in order to ease the integration within existing Transmitters. It constitutes a unique solution to upgrade transmitters from ATSC 1.0 to ATSC 3.0.