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Cellular bonding for live event streaming: The state of the art.

Cellular bonding products are key tools for live event producers, who use them to transmit their live streams to the cloud via these multiplexed cellular signals when Ethernet or Wi-Fi isn't available, and to replace much more expensive satellite transmissions. To catch up on the past, present, and future of cellular bonding, we spoke with executives from four companies that manufacture and distribute cellular bonding products and services.

Specifically, we corresponded via email with LiveU COO and Cofounder Avi Cohen. We spoke with Cahit Akin, CEO of Mushroom Networks; Bob Hildeman (CEO) and Alex Telitsine (CTO) from Streambox, Inc.; and Jon Landman, VP Sales at Teradek. Here are the questions, and here's what we learned.

What Is Cellular Bonding?

For those new to the technology, cellular bonding products use multiple cellular modems to combine 3G, 4G, LTE, and other cellular signals to provide increased throughput and signal resiliency. Many cellular bonding products can also combine other signals, like Wi-Fi and Ethernet, for even greater robustness.

Interestingly, Streambox developed its first bonding products during the second Iraq War when a prominent news organization requested a product that could combine two 64Kbps Inmarsat satellite signals into a 128Kbps stream for both video and audio. Much of the news delivered remotely during that war was via bonded signals.

Although our primary focus is on live production, cellular bonding is used in a much broader range of applications. For example, cellular bonding products provide Wi-Fi on trains and buses, provide data and video links for first responders, transmit signals from remote security cameras, and even provide data links for crop sensors on large farms.

How Effective Is Cellular Bonding in the Real World Today?

Like all technologies, cellular bonding had humble beginnings, and many early forays into livestreaming via cellular bonding met with more failure than success. Since then, services like Facebook Live and YouTube Live have resulted in much more contention for available cellular bandwidth from casual producers. This begs the question, "How robust is cellular bonding for mission-critical applications today?"

As we learned from our respondents, we need to recognize that while there are many more users, there are also many more towers, and they're increasingly connected to the base station via high-bandwidth fiber, increasing tower capacity. While you shouldn't try to use a single connection for real production applications, Mushroom Networks' Akin states that, with a properly configured bonding solution (more on configuring later), you should be able to achieve a successful transmission more than 99% of the time.

Teradek's Landman has a personal example. In May 2017, he was in Times Square when one woman was killed and 22 injured by a car driven by a PCP-fueled suspect with "psychological issues." Landman started transmitting video using a four-node Bond III unit and the company's new H.265 encoder. Despite transmitting from one of the world's densest population centers, and competing with as many as 15 other bonding units present on the scene, Landman managed to broadcast a consistent 1080p signal at 4Mbps.

Obviously, cellular availability varies by country, and even by regions within a country, though Streambox's Hildeman points out that coverage is more than adequate for successful live transmissions in many countries. As an example, Streambox's technology has been adopted by the Argentine Federal Police to fly drones over soccer matches, streaming security footage back to the authorities while competing for coverage with 70,000 ardent soccer fans, many seeking to share their experiences via the various social media channels.

How Can You Improve Your Chances for Success?

There are two ways to get better bonding results: deploy multiple modems or use signal extenders to make your signal more powerful than the typical cellular phone you're competing with. On the first point, our executive panel agreed that two modems constituted the bare minimum, but that four was the sweet spot, particularly for those transmitting at 1080p. According to Streambox's Hildeman, "Bigger providers never go live with two modems. They typically deploy four modems from four different providers to produce a reliable 5-12Mbps."

Expanding upon the reliability aspect, Mushroom Networks' Akin points out that the value of multiple cards is more about signal resiliency than top-line throughput. Although a single modem can spike to 10Mbps or higher, you can't achieve the sustained throughput to "convert an unpredictable link to a predictable one." For that, you need multiple modems.

Teradek's Landman disagrees slightly with Hildeman's provider strategy, particularly for those broadcasting primarily from a single city or similar geographical area. He recommends getting two modems from the strongest service in the area and two from the next strongest. A useful site for identifying the front-runners is Open-Signal.com, which publishes reports showing coverage in many major geographical regions.

Beyond using multiple modems, you can also deploy signal extenders, either as separate devices or integrated into the cellular bonding modems. Signal extenders can have two components, a larger antenna to receive and broadcast the signals, and a booster to amplify them. Some extenders only have antennas, some have antennas and boosters. For example, the Streambox Signal Extender 2.A shown in Figure 1 has both components, while the company's Signal Extender 2.0 lacks the amplifier.

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Teradek's new Node product (Figure 2) also combines larger antennas than are available on most cellular modem cards with a signal amplifier for an extra boost. Significantly, this is the first Teradek product that accepts SIM cards directly into the unit, which simplifies transport and usage, and presents a more ruggedized and weather-proof exterior. While the first versions of Node will be region-specific for North and South America and other areas, Teradek plans to introduce a worldwide unit at some point in the future.

Similarly, the LiveU Xtender integrated antenna-only solution can increase network reception for additional resiliency for live video transmission in heavily crowded areas. The bottom line is that whichever cellular bonding system you choose, you can increase your chances of successful transmissions by using two to four modems and signal extenders.

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What's New in 2017?

Potential buyers sorting through new models from these vendors will find plenty of new features, including HEVC encoding from LiveU and Teradek, which should deliver quality comparable to existing H.264-based products at 40-50% bandwidth savings. This is obviously significant when you're vying for bandwidth, or if you'd like to cut costs by using fewer modems or lower bandwidth.

LiveU's product is a new HEVC Pro Card, which is available as a user-installable upgrade to LiveU's LU600 unit, as shown in Figure 3. The card supports both HEVC and H.264, which is important for backward compatibility with most CDNs or live-streaming services.

Teradek's product is the Cube 755, a standalone HEVC/H.264 encoder that can transmit directly via Wi-Fi and GigE support. Alternatively, you can transmit via Teradek ShareLink, a service that bonds signals from multiple iPhones (but not Android phones), along with the Wi-Fi or GigE from the Cube unit itself. Or, you can pair the Cube with a Teradek Bond cellular bonding unit.

Despite the obvious benefits of HEVC, note that you'll find few direct use cases. That is, few, if any, live-streaming services or CDNs accept HEVC input--yet another result of the devastatingly poor royalty strategy pursued by HEVC IP owners. If your ultimate target is a CDN or livestreaming service, you'll have to transmit through each company's cloud service, transcode to H.264 in the cloud, and route the transcoded signal to the desired service or services.

Some services, like Teradek's Core (see Figure 4 on page 74), will charge extra for this, while others, like LiveU, don't plan to, at least for sub-4K streams. If you're buying into HEVC to save money, be sure to factor the costs of these transcoding services into the equation. Alternatively, for point-to-point transmissions, you can transmit directly to an HEVC decoder, which both companies offer.

New from Mushroom Networks are the Streamer 2000i, 4000i, and 8000i devices (see Figure 5 on page 74), which have been ruggedized and run through certifications for deployment on trains, or with first responders or law enforcement. These units feature embedded modems, passive cooling, external antenna connectors, embedded Wi-Fi, and optional lockable M12 Ethernet connectors. In addition to streaming video, these units can also provide high-speed internet access, doubling their potential utility. All three units, which feature two, four, and eight embedded modems, respectively, are transmission units only, and can work with most standalone encoders.

Streambox's most recent innovation focused on modularizing the company's tiny Avenir Micro so it can be deployed in multiple form factors. The base encoder itself weighs half a pound and uses 10 watts of power, and comes with an AC adapter. The Avenir Micro has HD-SDI and HDMI inputs, along with GigE and Wi-Fi so it can encode and transmit video without any accessories. Modular options include three battery modules (Streambox, Anton Bauer, IDX), embedded and USB-connected modem modules that can accept up to four modems, and more.

Interestingly, like all Streambox encoders, the Avenir encodes using the Streambox proprietary ACT-L3 Advanced Profile Codec, which on this product can encode up to 1080i/59.94 video at data rates ranging from 64Kbps to 18Mbps. Streambox also offers rackmounted hardware that can support up to 4K resolution using the same ACT-L3 codec. As with HEVC as utilized by Teradek and LiveU, this means that the streams are not directly compatible with any CDNs or social media services. To support these sites, you must route the video through Streambox Cloud, or you can send the video to Streambox decoders that can output single-link 6G-SDI 4K, 3G-SDI x 2, or HDMI video with eight-channel embedded SDI audio or analog XLR.

A recent priority for all companies has been building enhanced cloud facilities that have the ability to control and configure their own encoders remotely, and route video to multiple outputs, including social media sites. Beyond this, each company is investing heavily in cloud facilities to provide the broadest and most robust feature set possible. As an example, Streambox has 11 ingestion points around the globe, with fiber connections in between, and its own Low Delay Multi-Path protocol to manage transport from encoder to the last mile. This should pay dividends for producers who are shooting in one part of the world and delivering in another.

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When Will 5G Be a Thing?

None of the executives we spoke with expect 5G to become relevant anytime soon. Akin, from Mushroom Networks, predicts that 5G is at least several years away, as mobile companies try to maximize the profitability of their investments in 4G technology.

Hildeman from Streambox believes that LTE Advanced, which has been deployed by Verizon in more than 450 U.S. cities, could have a more immediate impact. Interestingly, LTE Advanced, which uses carrier aggregation to utilize multiple LTE channels at once, is a form of a bonded solution. Hildeman also notes that companies like Google and Comcast are deploying large networks of Wi-Fi hotspots, and that bonding devices should also benefit from incorporating these into the aggregate signal.

Finally, Teradek's Landman points out that all providers in the space are agnostic as to the cell signal, since the key technology is how efficiently they can mux them together. So supporting new technologies should occur soon after they become relevant.

Choosing a Vendor

All of this has been interesting (I hope), but you've probably read this article to assist with an upcoming buying decision. So here is some specific advice for that. Step 1 is always to plot out how you'll be using cellular bonding, which can range from simple, stream-to-Facebook-Live applications, to point-to-point video transmissions to decoders in your studio, to more complicated hybrid schemas that involve encoders, decoders, and the cloud.

In particular, if you have existing encoders that you need to use, you'll want a transport-only solution. Recognize, however, that integrated encoding/bonding solutions may provide a more-functional solution overall. That's because within an integrated solution, the encoder can adjust the data rate of the encoded video upward or downward to reflect the available bandwidth, improving quality when bandwidth is plentiful, but preventing dropped frames and stoppages when bandwidth drops. If you're streaming from a notebook running vMix into a modem-only solution, there's no back channel for adjusting the encoded bitrate if bandwidth drops, so you risk stoppages--or you'll have to stream at a less-aggressive data rate to avoid them.

Then assess product requirements like miniaturization or ruggedization to identify which families of solutions can meet your needs. From there, ask the following questions and take these steps before buying a cellular bonding solution, whether from one of the vendors included in this discussion, or any other.

Ask Around

Recognize that there are multiple factors that impact throughput beyond the speed of the underlying cellular modems. Specifically, the underlying technologies that differentiate products from these companies include how efficiently they can bond together the signals, and how fully they can utilize the bonded signal. All companies also offer some form of error correction to maintain a robust signal when packets are lost. As you've learned, cellular bonding systems use different codecs, including H.264, H.265, and Streambox's ACT-L3 codec.

All of these factors impact the bandwidth necessary to transmit a sufficiently high-quality video signal, and they impact each device's ability to maintain that bandwidth. The best way to figure out how a particular device will perform in your area is to ask producers who are already using it. While you're at it, you should ask how many modems they're using, and from which provider.

* What's the minimum functional bitrate? While it's probably not relevant in most regions in the U.S., minimum bitrate becomes critical in many other countries. If you'll be operating outside of the U.S., this is one number you need to know.

* What's the available cloud functionality? When you choose a cellular bonding modem, you'll likely also be buying into the cloud solution offered by that company. So understand what you'll need from the cloud before buying the hardware, and understand what it will cost, particularly if you'll use the cloud service to transcode from HEVC or ACT-L3 to a format your target CDN or social media service can accept.

By this point, most cloud services should be able to remotely update, configure, and control their encoders, provide previews of all streams, route streams to multiple points (including social media services), and archive the streams. If your usage will be primarily local or regional, most cloud services should work well. However, if you'll be routing signals around the globe, you should understand whether the cloud service has the infrastructure and protocols to efficiently support this.

Take these steps, and follow the guidelines provided within this article, and you should be able to configure, acquire, and use a functional system that reliably gets your signal up to the cloud, and to multiple output points from there.

By Jan Ozer

Jan Ozer (jan@streaminglearningcenter.com) is a streaming media producer and consultant, a frequent contributor to industry magazines and websites on streaming-related topics, and the author of Video Encoding by the Numbers. He blogs frequently at streaminglearningcenter.com.

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Author:Ozer, Jan
Publication:Streaming Media
Date:Jul 1, 2017
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