Introduction
The Holy Grail of spectrum planning is finding the most efficient transmission path for the most used data.  In today’s digital world, this data can range from NBA basketball games to enhanced GPS coordinates to 3D maps for autonomous cars.  International and domestic spectrum czars have recognized that flexible channel use is the licensing key, and U.S. broadcasters have jumped at the opportunity.  While continuing to provide public interest-based video programming, they are now fully embracing a new transmission standard: ATSC 3.0, aka NextGen Broadcasting.

The European Telecommunications Standards Institute, with help from the 3rd Generation Partnership Project (3GPP), has cobbled together a different option: the so-called “5G Broadcast System.”  5G Broadcast is built on the existing unicast 4G LTE waveform.  It is far from “new.” Despite the hype (and money) surrounding these two options—ATSC 3.0 and 5G Broadcast—they are not equal. Is this Betamax vs. VHS? Blu-Ray vs. HD DVD? PlayStation vs. Xbox? Or is this something more dynamic? Which is better? Read on. (Spoiler alert: it’s ATSC 3.0!)

Background
Technological advances and audience demand have pushed past plain-old linear program services. Free over-the-air (OTA) transmissions are giving way to paid, on-demand services, both physically connected (cable, fiber, phones, internet) and wirelessly connected (satellites, cellular and WiFi). Those have been, by and large, inefficient, one-to-many, dedicated, unicast services.    

U.S. broadcasters, recognizing their inherent advantage of robust, one-to-many, high power/high tower (HPHT) broadcast capabilities, have now added fundamental enhancements. Those include transmissions using the same “language” of the internet—Internet Protocol (IP)—and new frequency modulation and coding technologies for reliable mobile reception. They have also solved the challenge of delivering hyper-localized content to different parts of a community. 

The new capabilities of ATSC 3.0 are elegant, efficient, and evolvable, aligning perfectly with the increased demand for multimedia content over mobile devices, which have swamped conventional cellular unicast networks. For television broadcasters, the ‘ALL IP’ standard and associated revenue projections have stoked the imaginations of those looking for whole new business opportunities.  

Meanwhile some entrenched wireless players (e.g. Qualcomm and Ericsson) are hyping approaches and technologies that facially appear to focus on similar objectives. While this reinforces the idea of additional revenue opportunities in mobile and datacasting, the allure is essentially illusory. Yes, they both provide IP transport, are more efficient than previous iterations and provide enhanced content.  But the similarities end at the physical layer: The ATSC 3.0 system is dramatically more efficient, robust, mobile, and evolvable.

Here’s why.

ATSC 3.0 – NextGen Broadcasting
NextGen Broadcasting is the most advanced digital terrestrial broadcast standard designed for over-the-air reception. It delivers an extraordinarily improved viewing experience, supporting ultra-high-definition high dynamic range (HDR) content, immersive audio, interactivity, and other advanced features to both fixed and mobile devices. 

It also enables use of the broadcast spectrum for a host of new data services. It was designed from the outset to offer multiple simultaneous wireless-based services in addition to broadcast television. It simultaneously accommodates fixed, portable, and mobile use cases, allowing flexible spectrum utilization tailored to various new platforms. And the ATSC 3.0 standard is adaptable for different use cases in different countries. 

At the heart of the ATSC 3.0 standard is System Discovery Signaling—the so-called “Bootstrap.”  It serves as the universal entry point into the broadcast waveform, ensuring that all receive devices identify and decode each unique signal, even those yet to be defined. This “evolvability” attribute is key to ATSC 3.0 ability to expand and adapt to support emerging offerings.

ATSC 3.0 Key Features

• Ultra-High-Definition (UHD) and Immersive Audio: ATSC 3.0 supports UHD resolutions with higher image quality and immersive audio formats, enhancing the overall viewing experience.
  
• Hybrid Broadcast-Broadband: It seamlessly integrates OTA broadcasting with broadband, enabling interactive content, targeted advertising, and other data-related features.
  
• Advanced Emergency Infomation: The robust bootstrap permits triggers for advanced emergency alerting that can wake up devices at very low signal levels, enabling the delivery of rich media supplements to target geolocations.
  
• Interactive Services: Viewers can access interactive content, on-demand video, and personalized services through the hybrid capabilities of ATSC 3.0.
  
• Data Delivery as a Service: IP transport and one-to-many architecture of the high power/high tower broadcast service provides efficient delivery of common data including video offloading, enhanced GPS offerings, automobile telematics delivery and IoT support services.
  
• Efficient and Flexible Broadcast/Multicast: OTA broadcast, native to ATSC 3.0, enables efficient data delivery to multiple users of fixed and portable/mobile services simultaneously.

5G Broadcast
In Europe, the search for an IP-based solution for fixed and mobile broadcasting gained momentum when the Digital Video Broadcasting (DVB) Project shifted its focus to DVB-I (IP content delivery). Activities like those of 5G-Xcast, 5G-MAG identified needs and uses of IP-based delivery.  5G Broadcast emerged as a multicast technology specified by the 3GPP, designed to provide broadcast and multicast services over various networks. 

(Read more: What is 5G Broadcast?)

To be clear—5G Broadcast is based on the old 4G LTE waveform. Over the past few years, 3GPP has tried to meet the challenges of the OTA broadcast environment. But, despite work to better support OTA broadcast environments, efforts to improve the physical layer of the underlying 4G LTE Broadcast platform (time and frequency interleaving as an example) have been rejected and/or withdrawn, including the latest Release from 3GPP.

5G Broadcast Key Features:

1. Efficient Multicast: 5G broadcast uses multicast transmission, efficiently delivering data to multiple users simultaneously, reducing the network load compared to unicast streaming to individual users.
   
2. Content Delivery Efficiency: It efficiently distributes live events, emergency alerts, software updates, and other high-demand content to many users as a “one-to-many” service.
   
3. Cellular Network Integration: 5G broadcast could seamlessly integrate with existing 5G cellular networks, enabling mobile network operators to provide content services without significant infrastructure changes.
   
4. Broadcast Mode: It operates in broadcast mode where many users need access to the same content concurrently.

Comparing the Two
There has been considerable hype suggesting that these two technologies are roughly equivalent and that 5G Broadcast has an edge given it is a 3GPP standard. While both technologies employ IP transport and one-to-many wireless distribution technologies using the same modulation scheme, the similarities largely end there. 

The implied notion that, because 5G Broadcast is a 3GPP standard and in phones today, it somehow magically opens the market to hundreds of millions of devices compatible with 5G wireless reception is wishful thinking. Here are a half dozen reasons why ATSC wins out:

1. ATSC 3.0 has the Bootstrap: Absent from 5G Broadcast, the real technological magic of the Bootstrap is its ability to discover and identify a near infinite number of different signals (including those that have yet to be defined) and pass only the needed one to the specific receive device, thereby enabling a host of new services. More significantly, the robust bootstrap carries triggers for advanced emergency alerting that can wake up devices at very low signal levels—think deep indoors.
   
2. ATSC 3.0 has better error correction: Better error correction means a more reliable signal than 5G Broadcast. The two transmission standards are vastly different in performance. 5G Broadcast employs a suboptimal waveform.
   
3. ATSC 3.0 is “robust by design” in mobile environments: ATSC 3.0 outperforms 5G Broadcast in mobile environments with fast fading channels. Its sophisticated time interleaver provides a 3 dB to 11 dB performance advantage, depending on vehicle speeds. 5G Broadcast has worse pedestrian (<3 kph) performance and terrible mobile (Doppler) performance above 10 kph since it has NO bit interleaving. This may be one reason why older versions of 5G Broadcast have been discarded by mobile operators.
   
4. ATSC 3.0 is compatible with IMT Services: Claims that the ATSC 3.0 physical layer is incompatible with International Mobile Telecommunications (IMT) services are misleading. ASTC 3.0 has demonstrated interworking at the IP level, and major mobile ecosystem stakeholders have endorsed this for future 3GPP standards activity. If differing physical layers were a real issue, WiFi (an IEEE standard), as an example, would similarly be an implementation problem.
   
5. ATSC 3.0 can share IMT resources: The assertion that only 5G Broadcast can share IMT resources is overstated. ATSC 3.0 can also achieve this through device-level solutions and network topology adjustments. While there are minor challenges any standard would face in integration at the device level (antenna size, receiver front-end, band-filtering as examples), there are solution paths at the device level (e.g., the MarkONE phone). Notably, there are no commercial phones today that support either 5G Broadcast or ATSC 3.0.
   
6. The cost of adding ATSC 3.0 to chips is negligible: While ATSC 3.0 is not yet integrated into IMT device system-on-chip silicon, the cost of adding an ATSC 3.0 demodulator is negligible compared to the incremental cost of mobile chipsets. The front-end frequency tuner, filters, and antenna(e) are common to either ATSC 3.0 or 5G Broadcast. 

Conclusion
In technology comparisons, it's crucial to separate what we think we know from the facts. 5G Broadcast has some visceral appeal:  Why not simply integrate and extend broadcast into the already existing cell phone 3GPP ecosystem? How hard can that be? However, that’s a compromise that has serious drawbacks. With 5G Broadcast you would give up on:

• a standard that can grow as needs and uses change,
• technological advancements and future capabilities while maintaining backwards compatibility, and
• maximizing the flexibility to do other things with your valuable spectrum. 

It’s as if you have a plot of land and are forever restricted to only growing corn on it.  Would you give up growing a more profitable plant or mining for minerals below the dirt or constructing a high rise to maximize the value of that land?  We should want to maximize the flexibility and new uses for our little “plot of spectrum.” The best equipment to maximize that is ATSC 3.0.  It’s the equivalent of a sophisticated EV tractor vs. a shovel. Go with the tractor. The upside is far, far greater.

ALEXANDRIA, VA.—ATSC 3.0 will be a suite of about 20 separate standards. The first one—describing the “entry point” into the physical layer (aka “Bootstrap”)—has been finalized and approved, and is posted on the ATSC web site. Known as A/321, it is the core physical layer specification.

The detailed description of the physical layer is found in A/322, “Physical Layer Protocol.” This is a very large (250+ page) and complex document. A/322 describes the RF/transmission system of the physical layer waveform. It enables flexible configurations of physical layer resources to target a variety of operating modes. The intent is to signal the applied technologies and allow for future technology adaptation. A/322 is currently at the Proposed Standard stage, with final approval expected this summer.

At this writing, more than a dozen other documents that describe various elements of the ATSC 3.0 system are at the Candidate Standard (CS) phase, where implementation experience is gained and the document is expanded and clarified as needed. The bulk of all ATSC 3.0 specifications have been made public for review and trial implementations. All ATSC Candidate Standards can be downloaded from the ATSC web site. See Table 1.

Table 1: ATSC 3.0 Document Status

SPECIFIED PROCESS

Working Draft documents in development include specification of the STL system, optional RF return path, runtime environment, and security provisions. In addition, a document is under development that describes the overall ATSC 3.0 system, and the components necessary to make it work.

Like any standards development organization (SDO), ATSC has a specified process for document development. Fig. 1 illustrates the major steps.

Fig. 1: ATSC document development process

The path taken by a standard from concept through to completion can vary. In general, however, the process is as follows:

1.A Specialist Group (usually with the assistance of a designated ad-hoc group of experts) develops the specification and approves it by consensus, at which point the document is forwarded to the parent Technology Group.

2.The Technology Group votes by ballot to elevate the document to Candidate Standard (CS) for a specified period of time. A two-thirds majority is required for approval. Comments are considered.

3.At or before the close of the CS period, the Technology Group votes by ballot to elevate the document to Proposed Standard. A two-thirds majority is required for approval. Comments are considered.

4.The ATSC Membership votes by ballot to approve the document. A two-thirds majority is required for approval. Comments are considered.

5.The completed document is posted on the ATSC web site as a Standard.

REACHING CONSENSUS

Reaching consensus is a key part of standards development. Consensus requires that under due process procedures, substantial agreement has been achieved among members. Substantial agreement means much more than a simple majority, but not necessarily unanimity.

The timeline for moving a document from one step to the next varies, depending on the document itself. For most of the ATSC 3.0 specifications, a time span of about two years is probably typical. The majority of work occurs during initial document development. After that, the CS phase is probably the second most time-intensive part of the process. The intent of this multi-level approval process is to make certain that the specification is technically correct and addresses the user requirements identified before work began on the project.

Work in ATSC is open to all with a direct and material interest in the work. All ATSC Standards, Candidate Standards, and Recommended Practices can be downloaded at no charge from the ATSC Web site.

Jerry Whitaker is Vice President for Standards Development at the Advanced Television Systems Committee. 

For more on this subject, visit our ATSC 3.0 silo. 

WASHINGTON—The Advanced Television Systems Committee has approved the bootstrap component of its developing broadcast transmission standard. “Bootstrap” refers to the “System Discovery and Signaling” architecture of the ATSC 3.0 physical layer. The bootstrap provides a “universal entry point into a broadcast waveform,” for multiple service types such fixed and mobile television, for example.

It is the first element of ATSC 3.0 to reach standard status. This means there will be no further modifications made to this particular element of the developing ATSC 3.0 standard. The bootstrap signal is one of the five technologies that will comprise the physical layer, the foundation of the standard. The remaining four are at “Candidate Standard” status and await a full vote.

The bootstrap architecture is “integral to reception,” according to TV Technology contributor Doug Lung. “The receiver only has to detect the bootstrap signal to know there is a DTV signal on a channel. The bootstrap signal is much more robust than the payload data, so antenna positioning isn’t likely to be a problem.” (See “The ATSC 3.0 Physical Layer—Bootstrap Basics.” Dec. 23, 2015.)

The bootstrap signal uses a fixed configuration “known to all receiver devices,” the bootstrap standard document states. Another characteristic provided by the bootstrap architecture is the accommodation of future signal configurations, including those not directly associated with the ATSC 3.0 standard:

“New signal types, at least some of which have likely not yet even been conceived, could also be provided by a broadcaster and identified within a transmitted waveform through the use of a bootstrap signal associated with each particular time-multiplexed signal. Some future signal types indicated by a particular bootstrap signal may even be outside the scope of the ATSC.”

The remaining components of the physical layer at Candidate Standard status include the “Physical Layer Protocol,” which describes the RF transmission system of the waveform. The CS period ends for the PLP April 4. “Signaling, Delivery, Synchronization and Error Protection” defines the “technical mechanisms and procedures pertaining to service signaling and IP-based delivery of a variety of ATSC 3.0 services and contents” over-the-air, via broadband and a hybrid of the two. It will come up for a vote after the CS period ends July 31.

All ATSC 3.0 Candidate Standards are available here.

For a comprehensive list of TV Technology’s ATSC 3.0 coverage, seeour ATSC3 silo.

See more of Doug Lung’s contributions, including...
November 3, 2015
“Getting Ready for the Repack”
After the FCC incentive auction is complete, likely before we transition to ATSC 3.0, many UHF TV stations will have to move to new channels. Many TV translator stations will have to find new channels, if they can.

July 23, 2015
“Getting Ready for ATSC 3.0”
The amount of spectrum devoted to TV broadcasters is shrinking—from a peak of 486 MHz before 1983 to 294 MHz today.

Also see…
May 7, 2015,
“ATSC 3.0 Bootstrap Signal Becomes Candidate Standard”
The first of five components in the Physical Layer transmission standard for ATSC 3.0 has been elevated to “Candidate Standard” status.

THE BIG ISLAND—The ATSC 3.0 standard is nearing completion. Candidate standards have been released for system discovery, or “bootstrap,” and the physical layer. Broadcast engineers will have to understand how ATSC 3.0 works if they want to take advantage of the improved performance and flexibility it offers. This month, I’ll describe the physical layer differences between ATSC 3.0 and other DTV standards in general and explain the unique ATSC 3.0 bootstrap signal in detail.

Most readers know that ATSC 3.0 uses OFDM (orthogonal frequency division multiplexing), which divides data among thousands of carriers (8K, 16K or 32K); versus the legacy ATSC standard that uses 8-VSB (eight-level vestigial sideband modulation), which puts all the data on a single carrier. All other DTV standards around the world, including DVBT, DVB-T2, ISDB-T, ISDB-Tb and DTMB use OFDM, although DTMB also supports a single-carrier mode.

ATSC 3.0 provides an improvement over existing OFDM-based DTV standards through use of the latest LDPC FEC (low-density parity-check forward error correction) codes and optimized constellations ranging from QPSK (quadrature phase shift keying) through 4096QAM (quadrature amplitude modulation).

Different combinations of codes, pilot patterns and constellations can be selected to allow data rates ranging from less than 1 Mbps in an extremely robust mode working at less than zero dB SNR (signal-to-noise ratio) to over 57 Mbps when a much higher SNR is available.

A key requirement for ATSC 3.0 is the ability to change the transmission format while continuing to support legacy receivers. This is accomplished through a framing structure that includes a “System Discovery and Signaling” signal, referred to as the “bootstrap” signal before each frame. This signal has a fixed physical configuration, but carries data identifying the version of the frame following it. This could be ATSC 3.0, a future ATSC 3.1 or some other variation; even one using a different waveform.

Frames carrying ATSC 3.0 data and those with different formats can be combined in the same RF channel. When it is time to transition to a new standard, the bootstrap will allow older receivers to ignore the new ATSC 3.1 frames, but continue to demodulate the ATSC 3.0 frames.

Fig. 7.10: ATSC 3.0 Frame Structure

Figure 7.10 from “A/322: ATSC Candidate Standard – Physical Layer Protocol” shows the frame structure of an ATSC 3.0 frame. The bootstrap at the start of the frame provides the information necessary to demodulate the preamble, which in turn provides the information necessary to demodulate the rest of the data in the frame and its subframes.

The bootstrap is the most robust part of the signal. The preamble is less robust than the bootstrap, but more robust than the data in the frame.

The bootstrap signal uses a Zadoff-Chu sequence combined with a PN (pseudo-noise) sequence to create a robust signal that allows detection and decoding at a SNR of around –10 dB or less. The Zadoff-Chu root defines the major version number and the PN sequence defines the minor version number. Once this frequency domain sequence is translated to the time domain using a 2048 point IFFT (inverse fast fourier transform), cyclic shifts can be applied in the time domain to encode information in the bootstrap symbol.

The bootstrap signal has a fixed bandwidth of 4.5 MHz, regardless of the actual RF channel bandwidth. The sampling rate is fixed at 6.144 Msamples per second with an FFT size of 2048, resulting subcarrier spacing of 3 kHz.

Each bootstrap symbol has a duration of 500 microseconds. The number of bootstrap symbols is set at four. The first is a synchronization symbol. Symbols that follow contain emergency alert wake-up information, system bandwidth, the minimum time to the next frame with the same major and minor version, and a value for one of the defined preamble structures. Annex K of “A/322” defines 119 different preamble structures.

BOOTSTRAP BENEFITS
Mathematics, beyond the scope of this article, is required to fully describe the bootstrap signal. To learn more, search Google “Zadoff Chu.” See “A/321 Part 1—ATSC Candidate Standard: System Discovery and Signaling” for a mathematical description of how the signal is generated in ATSC 3.0. Zadoff-Chu sequences are also used in LTE cellular transmissions.

The ATSC bootstrap signal provides benefits beyond those I mentioned earlier. In addition to providing a universal entry point to the ATSC 3.0 waveform and any future waveform, the robust signal gives the receiver a head start on frequency offset and RF channel estimation, making it easier to decode the preamble and the rest of the frame.

The bootstrap is integral to reception. The time required to complete a DTV channel scan is a major frustration for viewers. Worse, channel scans often have to be repeated if the desired signal wasn’t received on the first scan and the antenna is relocated. The bootstrap signal should help solve both of these issues. The receiver only has to detect the bootstrap signal to know there is a DTV signal on a channel. The bootstrap signal is much more robust than the payload data, so antenna positioning isn’t likely to be a problem.

The spacing of the frames will determine how long a receiver will have to remain on a channel to detect the presence of an ATSC 3.0 signal. Although the ATSC 3.0 standard will allow frame lengths up to about 5 seconds, such long frames are not likely to be used for conventional broadcasting because it will greatly slow the time required to change programs, even on the same channel.

A more realistic frame length is around 250 ms. At this frame length, a scan of 49 channels would take less than 15 seconds! While this won’t provide the call letters or program information on available stations, that information can be easily obtained after the identified channel is selected, on a more detailed follow-up scan, or from a listing of stations in an area transmitted by one or more of the stations.

The bootstrap signal also will play a key role in emergency alerting. For example, a portable receiver in a tablet or cellphone only has to turn its receiver on long enough to pick up the bootstrap signal (2 ms). The receiver does not need to decode the preamble or the rest of the frame or turn on additional demodulation circuitry until the bootstrap signals that an emergency alert is available, reducing power consumption and thus providing longer battery life. When an alert is received, it can switch on the demodulator and receive and display the emergency message and supplemental data.

The ATSC 3.0 standard offers broadcasters unparalleled flexibility. If broadcasters fail to utilize this flexibility, they may find consumer electronics manufacturers reluctant to support it in their products. Understanding the options is the first step.

Over the next few months, I’ll delve into the ATSC 3.0 candidate standards in more detail and examine some practical examples of how this flexibility can be used. The ATSC candidate standards are available at http://atsc.org/standards/candidate-standards/.

How would you like to see ATSC 3.0 used? How can it increase consumer interest in broadcast TV? Email me atdlung@transmitter.comand I may use your answers in the examples.

See more of Doug Lung’s contributions, including...
November 3, 2015
“Getting Ready for the Repack”
After the FCC incentive auction is complete, likely before we transition to ATSC 3.0, many UHF TV stations will have to move to new channels. Many TV translator stations will have to find new channels, if they can.

July 23, 2015
“Getting Ready for ATSC 3.0”
The amount of spectrum devoted to TV broadcasters is shrinking—from a peak of 486 MHz before 1983 to 294 MHz today.