Monthly Archives: September 2001

Broadcast ITV: What It Is, How It Works, Why It Matters

by Leslie Ellis // September 17 2001

It’s safe to say that, in U.S. cable geography, none are more vexed by churn than the smaller operators – those focused on the wide, green swaths of the nation that aren’t particularly urban.

Capitally squeezed, these companies, oftentimes independently owned, are as helpless to the rich lures of DirecTV and EchoStar as small, independently-owned retail stores were when Walmart pulled into town, with its big, easy parking and bulk-based discounts, 12 or so years ago.

Walmart’s mantra, “more for less,” parallels the battle cries of the two DBS providers. Recent promotions by both DirecTV and EchoStar practically gave away the digital set-tops (which cost upwards of $200 to make), and plunged monthly subscription fees as low as a $9/month for 100+ digital channels.

“More for less” immediately and unpleasantly transforms the public perception of small, local cable providers into “less for more.”

It used to be that “more,” in terms of competing video offers, meant more channels. Small cable operators kept stride by scraping up enough cash to buy digital set-tops and digital programming – the latter, in most cases, from AT&T’s Headend in the Sky (HITS) service.

Today’s “more” from the satellite duo means scores of interactive features, on-demand television (albeit without local off-airs, in many cases), and a continued downward shove on equipment prices and monthly subscription fees.

Clearly, it’s not easy being a small cable operator right now.

There is, though, a bright spot on the horizon for cable’s petite siblings. It goes by two monikers — “broadcast ITV” or “basic interactive” – and is envisioned to be a cost-free adder to existing digital TV services. Happily, it doesn’t require extra equipment, or two-way plant, at the system.

Broadcast ITV is a far cry from personal video recorders and on-demand TV; but, it’s a far cry from nothing, too.

Broadcast ITV means pushing a button on the remote to play solitaire, or other such games. It means pushing the button to read text-based news articles on a wide range of topics, or to view extra information bound into participating TV networks – what technologists and ITV aficionados call “virtual channels.” All of it happens translucently, atop the TV show in progress.

As the name implies, broadcast ITV involves injecting interactive applications from servers into MPEG-2 digital broadcast streams at the satellite uplink. Again, in most cases affecting small operators, this happens at the HITS facility in Littleton, Colo. Specifically, the services are spliced into the transportation portion of the MPEG-2 video compression standard. From there, they move much like any other digital video channel, up to the satellite, and down to recipient cable headends for dispersal to digital set-tops.

To get broadcast ITV, when it is available – HITS is publicly working with Liberate for a possible launch before year-end; OpenTV is wrangling, and Canal+ Technologies is technologically outfitted to participate, too – small operators will need to do one thing: Download the core of the new apps into existing digital boxes.

Recalling the words of former Cox CTO Alex Best – “every time somebody tells me it’s just a software download, my knees knock” – a global download is cost-free, but requires vigilant pre-planning and testing to assure it doesn’t inadvertently addle existing services.

After the core broadcast ITV apps are safely ensconced in the digital boxes, any “refresher” content just keeps getting sent, like a broadcast, new stuff replacing old stuff in the broadcast queue. Tactically, it means that just the app itself sits in the box. When a subscriber clicks, the box displays what it can of the desired content, and opens the gate on the continuous broadcast stream to accept the associated content.

Say it’s a news ticker. What shows first is the headline. Clicking on it invokes a slight delay, as the box locates the packet headers of the desired info – the addressing information, typically sent in the out-of-band broadcast stream – and links it to the visible headline.

To work properly, broadcast ITV requires that its applications be extremely tightly-written: Skeletal, really, more than svelte. While a PC-based operating system, like Microsoft Windows, typically maneuvers in double-digit megabytes of computer memory, the applications of broadcast ITV won’t get a roomy welcome. In many cases, ITV applications must be measured in kilobytes. That’s because there just isn’t enough memory or processing muscle in today’s installed digital boxes to do much more: The Motorola DCT-2000, for example, contains about 4 Megabytes of total memory.

Getting to broadcast ITV should give smaller operators a few tools to fend off subscriber churn to DBS – to shed its “less for more” wrappings, and get closer to “more for less.” It’ll take some doing, and it’s wise keep Best’s observations close at hand during field changes. Of course, getting to an affordable set-top that contains enough processing muscle and memory to compete more vigorously is better.

That’s the how of broadcast ITV. Next time, the hows and whys of set-top memory.

This column originally appeared in the Broadband Week section of Multichannel News.

What is Modulation, Anyway?

by Leslie Ellis // September 03 2001

It’s the week of yellow school buses and book bags for most young people, which serves as a good enough reason to venture back-to-school on one of cable’s more enigmatic and pervasive technologies: Modulation.

Modulation, to industries that move information for a living, is as essential as oxygen is to humans. It is present in every analog and digital service ever delivered over a communications network — cable, telephone, wireless, or otherwise. Without modulation, signals wouldn’t move, or at least not very far.

From the earliest days of cable, through digital’s rise, and as far out as the next-next version of the DOCSIS cable modem specification (beyond 1.1), modulation sets the pace for what MSOs can and can’t deliver.

To modulate is to imprint information — voice, video, data, whatever; analog or digital — onto the spine of a carrier signal, so that it can get from one place to another. Maybe from the studio to the uplink, or from the uplink to the satellite, or from the headend to the home.

A carrier signal is an electromagnetic wave, which is a form of energy — just as heat, light and sound are forms of energy. Electromagnetic waves are invisible, and ubiquitous. One of their more interesting scientific properties is their ability to propagate through space, or over a conductor (such as a cable), essentially at the speed of light. Like most other forms of energy, the strength of the electromagnetic wave dissipates in a known and predictable manner.

The best way to envision a carrier signal is to picture the letter “S” on its side. One transit from the beginning to the end of the sidelong S-shape is one cycle. One cycle per second is 1 Hertz, or Hz. One million cycles per second is 1 MegaHertz, or MHz. The total number of cycles per second is the frequency of the carrier signal.

Now draw a horizontal line through the center of the sideways “S.” The distance from that line to the peak, and to the valley, is the amplitude of the carrier signal. Amplitude, translated, is power. The shape of the curves is known as the phase of the signal.

You see how this gets pretty dense, pretty fast. Hang on. We’re almost there.

As it turns out, changing the frequency, phase or amplitude of a carrier signal is what modulation is all about. Changing those core, electromagnetic ingredients is how information is impressed onto a carrier. It’s what’s happening when you hear of “amplitude modulation” (AM) and “frequency modulation” (FM). The former manipulates a signal’s power; the latter, the number of cycles per second it transmits.

Then there are the digital modulation types, such as Quadrature Amplitude Modulation (QAM, pronounced as a word that some rhyme with “Sam,” and others rhyme with “Tom.”) And, Quadrature Phase Shift Key, or QPSK (spelled out, conversationally). Both are hopelessly technical terms, but not impossible to grasp.

In a very condensed translation, QAM works by grouping digital bits into symbols, which get imprinted onto a carrier by adjusting two things: Amplitude (power) and phase (shape). The “quadrature” reference, in this case, means “at right angles.” There are four right angles in a 360-degree totality. The “quadrature” part of QAM, then, has to do with shifting the phase of the digital signal by 90 degrees, in order to imprint the digital information.

The number that usually sits ahead of QAM refers to the number of symbols — grouped bits — impressed onto the carrier. In 64 QAM, eight symbols are sent. In 256-QAM, 16 symbols are sent.

QPSK is a subset of QAM that manipulates just the phase of the carrier to move bit groups. As such, it is roughly equivalent to 4-QAM, or four symbols sent per second.

The constant in all modulation types is this: They walk a fine line between transmit speed, and noise immunity. QPSK is slower, but sturdy against noise. That’s why it gets used mostly in upstream, home-to-headend transmissions, where noise is common. QAM is faster, but less rugged in big noise. It mostly gets used in downstream, headend-to-home transmissions.

For all its venerability, the modulator itself isn’t much to look at. It’s one of those slender panels with blinking lights, stacked up one over the other in a headend rack. There’s generally one modulator for each channel on a cable lineup. In a signal path sense, it generally sits between the signal source (the satellite receiver, for example, or digital multiplexer), and the combiner (the thing that smooshes all the channels together to be squirted into the fiber or coax plant.)

You’ve seen modulators if you’ve ever toured a headend. Maybe you nod appreciatively, secretly wondering. Or, if you’re into being technologically gracious, maybe you step around the back to admire the tidy wiring.

The subject of modulation is dense and old, but knowing its rudiments is worthwhile. For one thing, it’s not going away. For another, it will continue to evolve — but its basic tenets, thanks to the laws of physics, will remain fairly stable. 

This column originally appeared in the Broadband Week section of Multichannel News.