C-Band Auctions: Broadcast Transitioning Strategies
How to optimize the use of spectrum for 5G
The insatiable demand for mobile data, driven by a multitude of consumer and business applications, is helping to advance the worldwide rollout of 5G. The potential 5G uses are themselves exciting and diverse, however spectrum must be made available to make this possible.
The broadcast and media industry currently uses some of the most desirable spectrum needed for 5G, so inevitably there are consequences. However, the rethink prompted by this allows broadcast and media organizations to look at advanced cloud and IP technologies that can not only solve the spectrum issue, but can also offer new, more agile, paradigms, allowing faster adoption of new capabilities and more flexibility for the future.
RULING THE (AIR)WAVES
Every country has a regulator that allocates radio frequency (RF) spectrum licenses. In the United States, this is the FCC. The spectrum is coordinated by the International Telecommunications Union in its World Radiocommunication Conference and uses spectrum in three different bands: low, mid and high. Each of these bands poses unique benefits and limitations depending on the application.
The low-band spectrum, in the region used by terrestrial broadcasters, has excellent reach. However, because the frequencies are low, the allocated bandwidth—and therefore, the data rate—is limited. The high-band (or "mmWave") spectrum has existing users in the satellite uplink market and is where the massive data rates synonymous with 5G exist. However, this has a very short reach and is ideal for fixed wireless terminals. Mid-band spectrum is an excellent balance between reach and bandwidth but includes the C-band frequencies used for satellite distribution, such as national channels, in the U.S. and other countries.
C-band refers typically to frequencies in the 3.7 GHz to 4.2 GHz range. The U.S.'s dominant use of this range is for program distribution of video feeds to broadcast, cable and telco headends. However, to make some of this spectrum available for 5G, C-band users need to take action now.
THE VALUE OF SPECTRUM
Most countries are currently holding spectrum auctions for various ranges within C-band. In 2018, Italy auctioned a block of low-band spectrum priced at €34 million per MHz. The auctions that taking place in the U.S. (opens in new tab) valued mid-band spectrum at $45.8 million per MHz.
Low-band and mid-band frequencies are in strong demand, and useful-sized blocks of frequencies often sell for greater than $1 billion. This provides a strong financial incentive for the regulators to raise revenue from such auctions, even if it means compensating existing users to move off those frequencies.
As allocation for mobile use increases and the momentum of 5G deployments intensifies, existing users may need to take action. In the U.S., the FCC has created an incentive program to encourage existing C-band users to migrate quickly, freeing up the frequency resource.
SPECTRUM TRANSITIONING STRATEGIES
For broadcasters, programmers and contribution links affected by spectrum reallocation, a strategic approach is needed to mitigate its impact and end up with improved capability. Potential strategies can range from using the spectrum more efficiently, moving the frequency, moving away from RF to IP or a combination of these.
For the simple spectrum efficiency approach, there are two main techniques by which the spectrum can be used more efficiently while retaining the same services. They are to improve modulation or to use better video compression.
First-generation DTT modulation (such as DVB-T and ATSC 1.0) had moderately efficient spectral efficiency; however, there was a significant gap between those modulation schemes and the theoretical limit, aka “Shannon's limit.” Later versions of both DVB and ATSC modulation standards allowed that theoretical limit to be approached more closely. These improvements were implemented in DVB-T2 and ATSC 3.0.
For DVB-T, existing services can migrate from DVB-T to DVB-T2 modulation. Since DVB-T2 has existed as a standard since 2009, the vast majority of today's Digital TVs and DTT STBs are likely to support DVB-T2, making a migration plan feasible. DVB-T2 also opens the opportunity for newer video compression.
On the other hand, ATSC has only recently released the new ATSC 3.0 specification, so it may be some years before there is sufficient adoption of the new modulation and video encoding formats to allow easy migration from ATSC 1.0 to ATSC 3.0.
IMPROVED VIDEO COMPRESSION
Improved video compression allows the same quality video to be transmitted using a lower bitrate and thereby reduces the need for RF spectrum. Two optimizations that can be considered: a) use a more recent video coding standard; or b) use more efficient video encoders. Taking the DVB-T to DVB-T2 example, the digital TVs that support DVB-T2 typically also support MPEG-4 AVC compression, meaning the legacy of MPEG-2 video could be eliminated in the same transition.
Similarly, anywhere that has decode capability for a newer standard can make that transition. Of course, that can always be made the case by deploying new decoders. HEVC and, most recently, VVC, offer substantial efficiency benefits over AVC (and in VVC's case, over HEVC). This may be particularly important because UHD resolution video has become more prevalent over the last few years, which creates demand for higher bitrates.
MOVING AWAY FROM RF
In some cases, squeezing bandwidth and using less spectrum may only delay the inevitable—and possibly just by a few years. So, the next available strategy is to look at alternatives to RF. This has different consequences for different applications, but it is possible to identify some applications for which this more radical step may immediately be a good choice.
The significant improvements in available IP network connectivity mean that IP-based options are much more attractive than might have been the case only a few years ago. Contribution links can take advantage of IP connections using private fiber or global IP network service providers. The increasing availability of cloud service providers' networks, combined with new protocols such as SRT, offers a realistic path to broadcast contribution using IP networks built for internet traffic.
Broadcast and cable programmer distribution networks can likewise consider transitioning to an IP-based or hybrid approach. This has more advantages as it brings new operational models and a more future-proofed approach, offering significantly better agility for new services and formats.
The reallocation of spectrum for 5G is well underway and is sure to continue. The consequences of that change are already felt by broadcasters, programmers and users of contribution links. This trend will continue for as long as the demand for 5G mobile data keeps increasing, and steps must be taken to deal with these changes.
Raul Aldrey is chief product officer for MediaKind.
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