The SBTVD Forum, Brazil’s Digital Terrestrial Television System body, has released results from the lab tests for the physical layer in phase 3 of the TV 3.0 project – presenting the technical details of why Advanced ISDB-T and ATSC 3.0 were both selected for field trials, and why 5G Broadcast was not.
As a quick recap, a month ago we reported that Advanced ISDB-T (the pre-standard Japanese broadcast system) and ATSC 3.0 (used in South Korea and the US) had both been waved through to begin field trials for Brazil’s forthcoming TV 3.0 hybrid standard from December 2023 through May 2024.
Then, in June 2024, just one of ATSC 3.0 and Advanced ISBD-T will be selected for the OTA physical layer of TV 3.0.
Now, for the test results.
To save our readers having to sift through the full 116-page report, we have extracted the respective summaries of test results across the three candidate technologies and compiled them into four charts, representing the four use cases.
In use case 1, for enabling side-by-side operation with existing ISDB-T systems in the same frequency bands, with minimum impact over existing planning, the minimum technical specifications were fulfilled most by Advanced ISDB-T – meeting 5 out of 8 criteria.
These are not surprise results, considering the existing ISDB-T systems used in Brazil’s SBTVD standards, which are also known as ISDB-T International.
ATSC 3.0 meets fewer minimum technical specifications in use case 1, with 4 out of 8, missing the 174 MHz to 216 MHz band, the very-high frequency (VHF) band airing channels 7 to 13 in Brazil, and the extended VHF band of 174 MHz to 230 MHz.
This can be explained because the lab tests for ATSC 3.0 in this phase were performed only on ultra-high frequency (UHF) channel 33 (587 MHz), since exciters (the component housing the oscillator, modulator and sometimes audio processor that feeds the broadcast transmitter) provided by the Advanced Television Systems Committee was limited to UHF operation.
Here, the player generates up to four multicast UDP streams that are used to configure the Core Layer and Enhanced Layer for the two ATSC 3.0 exciters used. After the RF transmission, the ATSC 3.0 demodulators forward the recovered multicast UDP streams to the decoder PC. The threshold of visibility measurement was then conducted using the video decoder.
With 5G Broadcast only partially fulfilling one of the frequency bands, showing partial side-by-side operation with the existing ISDB-T system, and not fulfilling any of the channel bandwidth, co-channel, or adjacent channel requirements, 5G Broadcast scores a weak 0.5 out of 8 in use case 1.
This is because the 5G system under evaluation has a limited frequency range (617 MHz to 637 MHz), and was tested with a 10 MHz bandwidth, since the 5G Broadcast receiver is not deployed with 6 MHz as per the Brazilian VHF and UHF channels.
Use case 2 stipulates enabling scalable broadcast network deployment in terms of coverage and capacity, flexible frequency reuse with spatial content segmentation (reuse-1), and the most efficient spectrum use possible, targeting both fixed indoor and mobile (high-speed) outdoor reception.
Advanced ISDB-T and ATSC 3.0 are neck-and-neck here, fulfilling both the MIMO 2×2 and multi-RF channel transmission with a minimum technical requirement of channel bonding. The two technologies also partially fulfilled the high-speed reception category, delivering to mobile devices travelling at 120 Km/h (74.5 Mph).
5G Broadcast, developed and specified as part of the general mobile communication technology of 3GPP, only met 1 out of 3 minimum technical requirements for use case 2 in these tests. To not even partially fulfill the high-speed requirement for mobile outdoor use is disappointing for a mobile broadcast technology.
As with the successful recent proof of concept for 5G Broadcast at Boston-based TV station WWOO-LD, a Qualcomm reference design mobile unit was used for testing. The Qualcomm brick phone is specifically designed for 5G Broadcast tests, and is not commercially available, which may have impacted its results in the high-speed reception tests.
Reuse-1 describes use of the same RF channel by independent stations covering adjacent service areas. Here, the SBTVD Forum did not want TV 3.0 to be bound by a black box with all components integrated and ready to use.
Frequency reuse-1 enables segmentation of geographic coverage, allowing for the same 6 MHz channels in Brazil to be used by neighboring stations broadcasting different content. This will allow broadcasters to target smaller regional areas, in a more efficient and precise way, using dual location.
The SBTVD Forum therefore endeavored to source the best possible technologies available and fit these around its particular country-specific requirements, such as eliminating the entire concept of channels.
Instead, every broadcaster will be an app via TV 3.0 in Brazil. When you turn on your TV, it will scan for apps available OTA, instead of channels, and once you receive an app, it will be installed on your TV and is responsible for the presentation layer. Viewers will then be presented with content that comes OTA via FTA broadcast or over broadband, and it can switch between these seamlessly.
This is why the SBTVD Forum has attempted to do something different with the physical layer for FTA broadcast, and why these physical layer test results are so significant.
Use case 3 is a key component of TV 3.0 in Brazil, for emergency warning systems much like ATSC 3.0 in the US – to provide a “wake-up” capability for compatible receivers in the event of an emergency warning alert. Despite this, none of the three technologies fulfilled the minimum technical requirements for this use case regarding the physical layer.
That will need to be ironed out during the field trials for Advanced ISDB-T and ATSC 3.0 kicking off in just a few weeks.
Finally, we have use case 4, to enable future extensions to the physical layer such as to support new modulation schemes. Again, all three candidate technologies fell short of the minimum technical requirements for this OTA physical layer lab test.
With the SBTVD Forum now moving into field trials with phase 3, there are just seven months until the June 2023 deadline to decide on one of either Advanced ISDB-T or ATSC 3.0 to comprise the OTA physical layer for Brazil’s future DTT standard.
Along with the transport layer, the physical layer is one of the most challenging areas in development of a broadcast standard, particularly for a generation-defining IP and app-based TV experience like Brazil’s TV 3.0, with personalized content, UHD/HDR, immersive audio, enhanced accessibility features, and advanced emergency warning system.
In earlier tests for phase 2, the SBTVD Forum concluded that it was necessary to carry out a real-time video coding subjective quality assessment using the video coding technologies selected for the TV 3.0 project – VVC and LCEVC – to determine the required bitrate for the OTA physical layer to enable delivering audiovisual quality superior to that of the first-generation Brazilian DTTB system.
It’s worth noting that DTMB-A (Digital Terrestrial Multimedia Broadcast – Advanced), the ITU standard from China, was also proposed as a candidate technology for the OTA physical layer, but was withdrawn by the proponent.
Going by these lab test results, it shows that Advanced ISDB-T is best positioned to beat out ATSC 3.0 for the prize come June 2024.