August 2001
 

The Bliss Of Mellifluous Power

BY KEVIN MAYER

Unfortunately, the pleasures of displacing power anxieties are no longer so easily available, not when convergence proceeds apace, when enterprise telephony becomes just another mainstream IT function, and the public network seems less and less monolithic, but rather an agglomeration of circuit-switched and packet-based hybrids.

Overall, these changes suggest a trend towards independence, manifest as freedom from proprietary, mainframe-style PBXs or as a proliferation of specialized service providers, and an ever richer assortment of enhanced services options. With independence, however, comes responsibility.

VOICE, DATA, AND THE FORGOTTEN NETWORK
With so much speculation about the convergence of voice and data networks, little attention remains for contemplating the role of the power network. And yet, as communications systems evolve, so do their corresponding power requirements. Let's consider how power requirements may relate to each of the following communications trends:

•  Instead of a solitary key system or PBX, a corporation may deploy and manage a constellation of voice-enabled servers, routers, and gateways. And individual desktop computers may implement each user's personal configuration and access preferences. In short, the trend is towards accommodating a wider array of network elements, and incorporating them in more distributed, more complex network architectures, which may leave corporations more vulnerable to adverse power events.
  
• Corporations are increasingly likely to consolidate voice and data functionality by deploying premises-based integrated access devices (IADs), PC-PBXs, and IP-PBXs. While convenient, such devices could bring down both voice and data if they were to fail, thus increasing the stakes of any power failure event. Another stake-raising communications application is unified messaging, which may involve a single server consolidating the functions of voice mail, e-mail, and fax servers.
  
• More corporations and contact centers are embracing multi-channel communications, not just in the sense of deploying alternative independent channels, but in the sense of orchestrating a variety of channels, accommodating each customer's contact preferences, translating freely from medium to medium, depending on content, time of day, nature of the communication (notification, reminder, etc.), as well as the perceived value of the customer relationship. Such intricate plans could come to naught, however, if even a subset of channels (or even a single channel) were unavailable due to an adverse power event.
  
• Increasingly, broadband data access is accommodating real-time, mission-critical communications. Telephony-ready cable infrastructure, DSLAMs, wireless data infrastructure, and gateways of various types increase the number of end office elements with an exceedingly low tolerance for power-related service interruptions.
  
• Corporations are weighing the advantages and disadvantages of outsourcing, often to data network providers of various types, many of which plan to carry real-time, mission-critical traffic on behalf of subscribers. Before committing to any outsourcing scheme, a corporation will want to ask about the provisions for power reliability the service provider may have implemented. And, of course, the service providers will need to have a compelling power control story.

For providers, something as basic as access to reliable power could become a competitive differentiator.

FEARFUL SYMMETRY
It is curious that just as voice/data convergence increases the general reliance on the power grid, the limitations of the grid are growing more obvious. The grid, while fairly well adapted to the needs of manufacturing and residential consumers, is less well suited to a high-tech service economy that relies on sensitive electronics. While a drill press or a hair dryer may function well enough despite occasional power fluctuations, circuit boards controlling communications are fussier. They require precision power. Plus there are issues of availability. Availability, as the extreme example of California attests, may become less rather than more assured, particularly if provisions for growth lag behind actual demand, or if policy missteps derange the mechanisms of distribution.

If traditional utilities prove less than completely reliable, or deliver power that is less than constant, alternatives such as self-generation or co-generation become more attractive. However, these alternatives may deliver power that is at least as "dirty" as that from a utility, and switching from one power source to another can itself introduce disruptions. However, a general trend towards more local power might also favor a trend towards greater reliance on DC power, since it was the need for efficient sharing of power over long distances that justified reliance on less "clean" AC power.

CONVERGING POWER PRIORITIES
In the access network, in the end office, and elsewhere in the telco space, the emphasis has always been on ensuring maximum uptime, providing nearly uninterrupted support for real-time, mission-critical communications. It was, after all, in the telco space where commitments to six or seven "nines" of reliability evolved.

Similarly evolved commitments apply in the IT space, at least in large data centers, which may even, like the telcos, rely on DC power, at least for certain classes of equipment. However, in many IT scenarios, power solutions tended to emphasize equipment protection, perhaps via a simple, disposable surge suppressor, or perhaps via relatively short-lived battery backup, which would at least permit a managed shutdown, if not continuous operation through an adverse power event.

While controlled shutdown capabilities are and will remain important, they do prompt the question of how much downtime is acceptable, especially since more and more IT functions are deemed mission-critical, and since IT may find itself responsible for maintaining converged voice/data infrastructure, which supports communications flows which are inherently intolerant of interruption.

Ultimately, we may see a convergence of power priorities. While those maintaining communications infrastructure may enhance uptime capabilities, in emulation of telco practices, they may also emphasize management flexibility, exercising discrimination about what must stay up, and what may be shut down, with an eye towards extending battery power though an adverse power event. That is, we may see more emphasis on self-diagnostics, manageability, and serviceability in all kinds of communications equipment, including classes of equipment for which such discrimination had scarcely been thought necessary.

Another area of converging priorities involves power density, which is closely related to yet another common concern, namely, cooling. Power density, or the amount of power consumed within a given volume, grows as computing and processing power grows, and as equipment becomes more compact, despite delivering more performance. Power density increases indirectly as a result of Moore's Law, and directly as a result of the increasing value of central office, data center, and collocation space.

The more power that is consumed within a given space, the more heat is generated, and, accordingly, the greater the need to dissipate heat. In the absence of effective temperature control, excess heat can shorten equipment life or even instigate a system failure.

POWER SOLUTIONS
In keeping with the general idea of converging power priorities, telco-oriented operations will be mindful of how much more sensitive digital circuitry is compared to analogue circuitry, as well as more demanding in terms of scalability, manageability, and serviceability, particularly in the light of greater competition amongst service providers and the proliferation of network equipment, including the possibility of service providers assuming greater responsibility for customer premises equipment.

IT-oriented operations will weigh their power control options while remaining mindful of how business imperatives place less emphasis on mere equipment protection, or managed shutdowns, and more emphasis on continuous uptime.

Both telco- and IT-oriented operations may be more inclined to rely on hybrid AC/DC systems. Telco operations will continue to rely predominantly on DC power and 48V systems, and IT operations will continue to evolve their AC UPS approaches to power control. Accordingly, on either side, the advantages of maintaining a single infrastructure, AC or DC, will outweigh the disadvantages of additional power conversion. For example, an IT operation responsible for some DC-reliant communications equipment would probably opt to convert some AC power to DC, instead of installing, managing, and maintaining both AC and DC batteries.

As for UPS systems in general, we could hardly conclude without first quickly reviewing the three basic UPS types: standby (or offline), line interactive, and online. They differ, for the most part, in how seamlessly they accomplish the switch from generated power (from the utility or self-generated) to stored battery power. The least expensive option, standby, accomplishes the switch more or less precipitously, upon detection of an adverse power event, a brownout or blackout. The somewhat more sophisticated line-interactive option, accomplishes the switch more delicately or selectively. That is, a line-interactive UPS will rely on a voltage regulator to adjust power up or down to accommodate brief sags or surges, resorting to backup power only when voltage exceeds a predefined range. Finally, the most expensive UPS option, online, doesn't switch at all. All current is converted to battery power and conditioned, eliminating sags and surges and noise, before powering equipment.

CONCLUSION
Ignorance of power requirement is no longer tenable, for such ignorance no longer a source of bliss, but inevitably, pain and loss. Instead, bliss should reside in knowledge, that is, in knowing you've made appropriate provisions. Certainly, this is the sort of bliss appropriate to power control. 

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