UNDERSTANDING TELECOM INFRASTRUCTURE

Much like broadcast systems and facilities, telecom systems and facilities have their unique symbols, labels, and documentation conventions. The key to understanding the technology and its application is getting a grip on the language. The keys to designing, specifying, and getting what you want include a basic knowledge of the subject matter and some design tools. The design tools include a computer with word processor, spreadsheet, and drawing capability. For large complex systems and networks, a database manager becomes an important tool for thorough and accurate cost and operations analysis. In addition to these tools, design reference material in the form of recommended practices, standards, product specifications, and data sheets are a must.

Another way of defining telecom infrastructure is a technique called layering. Layering, as used in computer and communications, is best explained as a technique whereby software and digital networks are designed and built in layers. The notion is that if the operational routine or software system is built in layers and each layer interacts or interoperates with the one above and below it, then the entire system is more likely to achieve its overall goals and effectiveness.

Examples of layering include the ISO Open Systems Interconnect model, the four-layer Internet model, and the synchronous optical network/synchronous digital hierarchy (SONET/SDH) four-layer model. These models are three entirely separate models, and while they may not have been created without awareness of each other, taken literally, they don’t appear to have any relationship. Figure 1 shows these three models side by side and how they relate to each other.

Figure 1: Open Systems Interconnect Stack

It’s almost impossible to design, build, and operate a network without some form of integration of all three. For now, take notice of the matching shades of gray—dark, medium, and white. The intention is to use the darker levels to represent the bottom layers and the lighter layers to represent intermediate and top layers in each stack.

THE NATURE OF TELECOM NETWORKS

Telecom or common carrier networks have evolved over many years. The basic elements include switching, transmission, and network management. Telecom network operations run 24/7 and require very similar levels of flexibility and reliability as broadcast operations. Telecom networks are said to be ubiquitous and are built to reach the widest possible market for their services.

A key characteristic of communications networks is the concept of channelization or use of one or a group of channels between two points to support movement of information. Channelization first appeared when Edison and a now nameless technician accidentally discovered movement of sound waves over a pair of wires. That first pair of wires eventually turned into two pair to facilitate a two-way talk path. Over time through the magic of technological evolution ways and means to enable multiple channels on a single talk path, or four-wire facility were realized. For many years the jellybean of telephone technology was and still is the voice grade channel. The channel, be it wire or a virtual channel has certain capabilities and limitations bound by the laws of physics. Attempting to send a 30-Mbs payload through a 64-Kbs channel doesn’t result in any more success than an attempt to pump 30 barrels of oil per hour through a 1-inch pipe. Expecting networks to carry voice, data, and video without some way to match each with a unique part of a communications channel is the equivalent of mixing oil, water, and orange juice into the same pipe and expecting each to arrive intact at the other end. The challenge is not so much in the mixing as in the separation at the receive end.

Telecom network architecture is standards based. Most telecom network operators standardize and base their designs on a limited number of manufacturers and suppliers, generally constrained by maintaining sound, competitive procurement practices. Equipment and software suppliers active in the market generally participate in standards development and tend to comply in most, if not all, aspects of applicable standards.

Telecom networks interoperate across business entity and physical boundaries that are local, regional, national, and international.

Telecom networks are built using a layered architecture. This architecture is based on international standards and consists of a physical layer, facilities, and service layers. Although this layering characteristic is related, it should not be confused with the seven-layer ISO model commonly used in data communications and information technology documentation. It is also related and should not be confused with the four-layer approach sometimes seen or referred to in Internet or Internet protocol (IP) documentation.

One of the main objectives of this book is to bring clarity to this picture for the reader. Clarity comes from understanding a greater level of detail of the telecom entity. For purposes here, the Internet is another facilities or service layer in the overall architecture. The Internet relies on classical telecom physical or transmission layer infrastructure. It is likely to remain that way for the foreseeable future.

Many, if not most Internet people, netizens as they sometimes refer to themselves in a third-person way, lack appreciation and understanding of the physical layer or the entire classical telecom infrastructure. To many it’s old, outdated, obsolete, and subject to complete disregard, yet it is critical to successful operation of the Internet. That’s because the original Department of Defense Advanced Research Projects Agency project included an assumption that the physical layer would always be 100% available. That general approach and attitude remains today and is reflected in such things as contemporary certification training and testing by router equipment manufacturers. There has always been a similar attitude and approach in classical data communications network design and operations. The simple message in this point is ‘‘don’t forget the layer 1 and 2.’’

Another area of misunderstanding and common misuse is the term private network. Networks are made up of individual elements of hardware and software, supported and managed by a sophisticated network and equipment management infrastructure capable of monitoring, detecting, and reporting network behavior and performance outside predetermined limits. Strictly speaking, a private network is built using the same or similar kinds of equipment, software, and supporting infrastructure. It requires capital investment and ongoing operations expense. In the same context, private networks are used exclusively by their owners and don’t provide services or facilities to others. Satellite facilities are generally thought of as private networks; however, regardless of the term, they are built using shared and nonshared equipment.

Public networks, also called common carrier networks, are shared among a community of enterprise and residential customers. They operate under rules and regulations promulgated by the Federal Communications Commission (FCC) and state Public Utilities Commissions (PUCs), based on state and federal law in the United States, and similar government bodies in other countries. This includes physical aspects of orbital platforms, radio frequency spectrum, and, to a lesser degree, the equipment and services in ground station facilities.

Virtual private network (VPN) is a term used to describe a network designed and created from public network facilities and services. In some designs, the customer purchases or otherwise acquires the right to use equipment and software making up a VPN. Typically, this equipment is located on customer premises, although it may be colocated in service provider facilities with other customers or carrier owned equipment. VPNs didn’t just show up yesterday. The incarnation in the mid-1980s was software-defined network (SDN). These terms are another source of confusion. At a high level, both mean the same thing. Both evolved from private networks, which are built using point-to-point private line facilities and premises based multiplexing and switching equipment. The use of the terms virtual private and software-defined came into vogue around the time of the divestiture of AT&T and the deregulation of the long distance industry. Early examples of SDNs include AT&T and the Bell Operating Companies, who shared central office switching as an alternative to a private branch exchange and enhanced private switched communications services.

VPN is often used to describe a data network, but it is nothing more than a combination of point-to-point private leased lines and shared core routers or, in the old days, multiplexers. Some will claim that VPNs include encryption, firewalls, and so-called tunneling and that they are capable of carrying voice traffic. These claims and attributes are all true; however, the concept of shared faculties is the same as used in the SDNs that arose in the late 1970s and early 1980s to support multiple locations private dial plans for telephone service.

LOCAL SERVICES DEREGULATION AND CHANGE AFTER 1996

With the breakup of the Bell System, long distance services were deregulated and began a path to a competitive marketplace. AT&T remained under greater restrictions than other common carriers. Regulations prohibited them from providing local service of any kind and they continued to be subject to tariff processes administered by state PUCs and the FCC.

The RBOCs were restricted as well. They were prohibited from offering any kind of inter-LATA service with three exceptions, the North Jersey LATA, an area on the border between Newark and New York; the South Jersey LATA between Philadelphia and Camden; and the DC LATA covering DC, and immediate surrounding areas in Maryland and Virginia.

With passage of the 1996 Telecom Legislation, the RBOCs were given a path to compete in the long distance market in return for opening up their networks to re-sale by third parties. This legislation defined and named entities in the local exchange business. The RBOCs were branded incumbent local exchange carrier (ILEC), and all others were named competitive local exchange carrier (CLEC).

Internet and Telecom: A Brief History

Alexander Graham Bell is credited with inventing the telephone sometime after Samuel B. Morse came up with the telegraph key and code, making smoke signals obsolete technology. Somewhere along the way, in the more recent past, computers learned to talk to one another over telephone lines. And then along came the Internet.

That’s almost enough history for practitioners. However, a perspective on the past is well worth a quick read because understanding some of the history, especially since 1982, provides insight into the changes the Telecom industry has undergone and how that has, or will impact media and entertainment industry operations in the future.

Keeping our focus on practical considerations it makes sense to start somewhere in the early part of the past century. After all, radio and telephones came from similar inventive roots and had electrical or ‘‘electronics’’ in common. It’s also instructive to observe that the two parted ways when digital electronics went solid state. With digital electronics—initially the switching transistor—devices could count and keep track of items or service transactions, calculate, or measure interesting, valuable operational and accounting characteristics of the business.

Someone figured out how to convert an analog signal into digital form, and the telephone world went for it with a vengeance. On the other hand, radio and television receivers didn’t warm to digital techniques until well after integrated circuits with divide and multiply capability became cost effective for use in tuners. Other similar events along the way could be mentioned, but suffice it to say that broadcasting and consumer electronics lagged the telephone industry in adoption of digital technology by many years and did so, one painful step at a time.

The telephone industry was digital in nature from the start. For example, the basic business transaction unit, or service function, was and still is, a phone call. The line was in use or it was free. It could be used or one had to wait. One person could talk to one person at a time (until party lines were figured out). One operator could connect two parties to make conversation, later capitalized by the industry in the form of a telephone call.

Almon B. Strowger, a Kansas City undertaker, invented the stepping switch to allow customers to decide between his establishment and a competitor without undue influence of the wife of his competitor who just happened to be the local telephone operator. The stepping switch enabled the industry to continue in a mechanized and automated fashion, without operators, one telephone call at a time, the staple of long distance telephone bills.

Audio—the staple of radio—was analog and stayed that way. In 2003, radio broadcasters began upgrading transmission facilities to digital transmission.

Video might be characterized as digital in nature—at the very least it’s highly structured. Pioneer inventors Philo Farnsworth and Vladimir Zworykin both conceived a fixed, repetitive scan structure. Farnsworth reportedly conceived his version while plowing successive rows in a field.

Historically, telephony, radio, and television share a common business life-cycle behavior. Still in relative infancy, the Internet seems to be evolving in similar fashion. The life-cycle includes three distinct phases starting with experimentation, moving into growth and consolidation, and finally into a mature state where the technology continues to evolve and the business segment makes a continuing contribution to the economy over a long time.

The CLECs

As we noted earlier, the CLECs came into existence in concert with the release of the Telecommunications Act of 1996, with plans to create a fully competitive market at the local loop level. Until that time, only the long-distance sector was fully competitive, with customers able to choose from among three major providers. The local loop was dominated by the ILECs. Since that time, the CLECs have carved out a reasonable piece of the market for themselves, supported by a certain degree of customer dissatisfaction with the ILECs, the promise of lower prices, and a number of favorable regulatory decisions including the Unbundled Network Element-Platform (UNE-P), which offered a generic switching and access platform to all entrants.

CLEC Challenges

Of course, the creation of a local competitive market has been fraught with difficulty. Many of the CLECs filed for bankruptcy because of inability to attract an adequate customer base, and while some analysts believe that CLECs may own as much as 65 percent of the medium enterprise market, their overall showing is still relatively small. In fact, while it is easy to conclude that CLECs are largely small startups that are giving fits to the ILECs, this is not true: Ironically, the largest CLECs in the United States have traditionally been AT&T and MCI, although recent regulatory decisions may force them to drastically reduce their footprint in the local marketplace.

For the most part, CLECs target the small-to-medium business market, which is largely underserved by the ILECs, whose primary focus is on the large business and residence sectors. Most CLECs resell services at a price that is 15 to 20 percent lower than the ILEC price and can thus attract a share of the market that is price sensitive. In fact, the numbers are significant: ILECs lease 20 million lines to resellers at an average of 40 percent of retail, although these numbers could change with the recent regulatory changes announced in recent months by the FCC—and which continue to be announced. The ongoing regulatory circus, combined with the burgeoning deployment of IP-based voice by various market sectors, will continue to make this game an exciting one for the CLECs. Stay tuned!

The ILECs

The ILECs have had a tumultuous ride since their inception in 1984, following the divestiture of AT&T. At that time, AT&T, through its negotiated settlement with the Justice Department, fought to retain control of its Western Electric manufacturing arm and spin off the local service providers because it was clear at the time that the real money was in hardware and that the local telephone companies would not be long for the world. In retrospect, perhaps they should have kept the local telephone companies (the Regional Bell Operating Companies, or RBOCs) and divested themselves of Western Electric. Amazing thing, 20-20 hindsight.

Today, of course, we know that the ILECs are in positions of significant market power. The four that remain—Verizon, SBC, Bellsouth, and Qwest—control 90 percent of the roughly 200 million access lines in the United States today. The remainder of these lines are served by CLECs—small independent telephone companies, cable providers, and wireless providers. Much to the chagrin of the ILECs, that 90 percent market share that they enjoy is declining at the rate of about 2.1 percent per year, and has been for the last couple of years, while “lineshare” for the other sectors has increased incrementally—but increased. It is critical that the incumbent telephone companies stop focusing on numbers of access lines and preservation of minutes of use, and start focusing on preservation of customers. That is the only winning measure.

Timeline Highlights
■	1963:81 million subscriber lines in United States; 159 million worldwide.
■	1966: First optical cable used for voice transmission.
■	1976: First digital switch installed by AT&T.
■	1984: AT&T is divested; at time of divestiture it has more than one million employees and is worth $155 billion.
■	1988: First transatlantic optical cable is completed.
■	1989:138 million subscriber lines in United States; 496 million worldwide.
■	1991: Bell Labs develops photonic (optical) switching capability.
■	2000: International voice traffic quadruples in 10 years to 132.7 billion minutes—but revenue only doubles to $70 billion.
■	2002: U.S. residential cable modem subscribers: 7.7 million; DSL: 4.4 million; data traffic passes voice at 200,000 TB/day; also in 2002, IP surpasses all other traffic in volume.

Contrary to popular belief, the most significant challenge faced by the ILECs is cable, not the threat posed by the CLECs. Cable companies are beginning to take on a more strategic role in the industry at large. After years of competing with satellite providers for “eyeshare,” cable providers are finally beginning to enjoy price stability for the services they provide over their almost completely digital broadband networks. Furthermore, they are beginning to offer a variety of value-added services in addition to their traditional distributive entertainment content, such as high-speed cable modem Internet access and Internet-based telephony—both of which have become significant revenue producers as well as disruptive forces among their new competitors, the ILECs. Furthermore, the recently upgraded cable modem standards (DOCSIS 2.0) add significantly to the capabilities of broadband cable. These companies are now offering what has come to be known as the quadruple play—voice, video, data, and wireless—all packaged as a single, converged, and very lucrative bundle.

The fact is that the ILECs are under siege on multiple fronts. One of the critical questions that now comes up routinely in strategy discussions is this: Should the big three (Verizon, SBC, and Bellsouth) stop spending so much on capital outlay to build out their own networks and instead start spending their cash on the acquisition of preexisting assets? Companies like WorldCom, Cingular, Nextel, and Sprint PCS are, by many measures, undervalued at the moment; and because the ILECs have a recurring revenue stream, they have relatively easy access to capital compared to some of their competitors. One of the biggest challenges they face is that they have very high fixed costs and very low variable costs—which makes it difficult for them to make major adjustments in their cost base without drastic changes (like huge headcount reductions). The danger is that as they begin to lose access lines to competitors—such as cable MSOs, wireless providers, and CLECs—at what point do they lose critical mass and begin to collapse under the weight of their own infrastructure? Furthermore, as ARPU levels decline without a closely tied reduction in costs, the hole gets deeper.

Consider that between 1998 and 2002 alone Bellsouth, Verizon, and SBC spent $140 billion in CAPEX on their networks, a move that yielded less than one percent revenue growth. In 2003 they made combined profits of $20 billion on a collective market value of $240 billion. Clearly they want these numbers to increase. In 1998, ILEC CAPEX was 30 to 33 percent of revenues; today it is far lower, about 14 percent.

What steps have they taken to remedy the ongoing revenue shortfall? The first steps they took involved a direct attack on the FCC with a petition to reenter the long-distance market, referred to by regulators as Section 271 relief. Section 271 of the 1996 Telecommunications Act allows the remaining ILECs (Qwest, Verizon, SBC, and BellSouth) to enter the long-distance market if they can prove that they have sufficiently opened up their local markets to competition. As you know from your readings, they have aggressively pursued this course of action; so, suffice it to say that the ILECs universally fought for long-distance relief in response to local telephony entry by their competitors and have in fact been granted large entry concessions. Verizon, for example, replaced Sprint as the third largest long-distance provider in terms of customer count. The originally stated reason for long-distance entry was incremental revenue, since the cost to an ILEC for in-region entry was near zero. However, while the ILECs doubled the number of long-distance customers they serve, the revenues from the long-distance lines of business they established declined 6 percent as the bandwidth glut and the magic of declining ARPUs took effect. Clearly, ILEC entry into long dis- tance has bought them precious little if any margin relief as they watch their local services revenues decline.

So what must they do? There are a number of steps that service providers can take to shore up their falling revenue targets. They include acceleration of the circuit-to-packet migration, which facilitates convergence; marshalling a renewed focus on the importance of the metro marketplace; aggressive revamping of their overall network infrastructures; a much stronger focus on both element and network management; an aggressive examination of the services that customers actually want and a plan to deliver them cost effectively; and a strong focus on both enterprise and residence customer requirements.

Circuit-to-Packet

The circuit-to-packet migration plan stems from the convergence activity that is underway throughout the greater industry. There is no question that circuit-based services such as voice, ATM, and frame relay will be around for some time to come, but there is aggressive movement going on with regard to packet migration. Companies are rapidly developing and rolling out service packages that rely on IP, softswitch technology, and packet-based services, including voice. The VoIP marketplace for wireless, Centrex, and PBX service alone is enormous. Now that the industry is back on its feet and money is moving in, this trend will accelerate. VoIP is a critical success component and not simply because it helps the telco reduce costs. It is critical because it facilitates the delivery of a new suite of converged applications and services that represent new revenue streams for the telco. There is nothing more important than that.

Metro Markets

Because of the diverse, multiprotocol nature of the metro marketplace and the ongoing evolution of the corporation—from operating out of a single metro-based location to a distributed corporate architecture with offices scattered throughout customer locations—metro has become one of the fastest growing market sectors for service providers. And because optical technology has taken root in the metro rather effectively, with low-cost, multichannel DWDM technology offering lower cost solutions due to optical’s ability to reduce the total number of network elements under management control, it garners attention. Today, ILECs control more than 60 percent of all metro spending; this is a significant percentage of the overall market and deserves the attention it attracts. Furthermore, the fundamental local-loop technology for the metro is Gigabit Ethernet, and to be even more granular, switched Gigabit Ethernet. Service providers can simply drop a fiber connection in the basement of a metro office building, terminate it on a high-volume Ethernet switch, and deliver a broad range of high-bandwidth services to multiple customers in the building.

Network Revamp

Today the typical ILEC operates a wide array of disparate and functionally unrelated networks: the PSTN, the IP network, the ATM network, the frame-relay network, the ISDN overlay, the DSL overlay, the wireless network, the high-speed Ethernet access and transport network, and so on. Recent technological advances such as Multiprotocol Label Switching (MPLS) and Resilient Packet Ring (RPR) allow for many of these network infrastructures to be converged onto a reduced set of protocols and physical networks, a move that dramatically simplifies the complex management task that ILECs face. This complexity translates into revenue barriers because of service delays, QoS issues, and billing discrepancies. Anything that can be done to simplify “the cloud” is a step in the proper direction because it reduces overall operating cost and stands a good chance of increasing customer service levels because of reduced network complexity.

The move to an IP infrastructure is clearly underway, but in many cases the telcos are reluctant to make big moves in that direction because of uncertainty over the business reasons for such a radical migration. In fact, there are relatively few valid business reasons for the migration to IP. The first is obsolescence: If a telco is facing a situation in which a switch in a central office is nearing obsolescence, then an IP overlay is probably worth considering. Or, if the telco is about to offer service in a greenfield (new, devoid of services) market, then IP is worth considering. Alternatively, if the service provider is facing a situation in which a switch is nearing capacity and will potentially require real estate expansion to accommodate the new equipment required, then IP is worth considering because of its reduced floor space requirements. Finally, if the service provider is operating in a region with a high degree of business penetration, or is in an area where fiber-to-the-home (FTTH) is being considered, then IP represents a serious advantage and should be considered as a key infrastructure component.

Management

Network and element management, like staff training, are often the first things cut from the budget and the last things implemented. Perhaps that’s a bit harsh, but not by much. One of the loudest complaints voiced by customers, especially enterprise customers, is billing complexity. Customers claim to want a single, simple-to-understand bill^[1] for all of their network services. And because of the diverse and logically disconnected nature of the network elements that come into play when provisioning customer services, the actual provisioning process is often slow, inaccurate, and expensive. Reduction of managed elements and the creation of an aggressively accurate and capable management interface must be of paramount importance to incumbent service providers.

Furthermore, there is ample evidence to suggest that the management systems operated by service providers since time began will soon be inadequate to handle the evolving demands of the services marketplace. Those systems are based on a model of predictable, recurring charges as well as a few nonrecurring charges every month. The market model, however, is beginning to embrace a more transaction-oriented billing model, which means that the OSS systems operated by the traditional telco will no longer suffice. It is critical that these companies actively evolve their internal systems to meet the needs of the changing customer base.

Another factor is physical deployment. The operating expenses incurred by ILECs to deploy DSL, for example, are inordinately high because it often requires multiple “truck rolls” (installation technician dispatches) to make it work. Not only is this expensive in terms of real dollars, it’s frustrating for customers.

Services

Next on the wish list is an aggressive examination of the services that customers actually want and a plan to deliver them cost-effectively. Service providers are now putting into place data-mining and knowledge-management applications to help them better understand the evolving needs of their customers and make them more capable of responding to demands for service, perhaps even before the customer realizes the need. Most important is the aforementioned understanding: At the risk of sounding simplistic, it is absolutely critical that service providers offer services the customers actually want rather than the services that they think they want or that are based on the technologies that happen to be available at the time.

Finally, related to the last item, it is important that service providers carefully differentiate between enterprise and residence customer requirements, as much for the commonalities of demand as for the differences.

So what are these additional services? Many believe that the key to enhanced market success lies in a well-planned entry on the part of the ILECs into the video services market, offering content and interactive video-based services. This could also lead to enhanced success for broadband wireless technologies such as the Local Multipoint Distribution Service (LMDS), WiMAX, and the Multipoint, Multichannel Distribution Service (MMDS). Some service providers are already looking at content delivery; consider, for example, Telus in western Canada. Telus was the first service provider in North America to deploy a regionwide IP backbone, one of the first to offer IP-based voice services, and now offers Telus TV, which is the equivalent of cable content delivered over DSL. Industry analysts continue to examine the viability of ILEC/satellite provider alliances, which would give ILECs an enormous footprint for service delivery and potential access to far-ranging content, and the satellite company access to a large collection of potential subscribers. And while this combination may not be ideal, it is worth considering in the future. Consider SBC’s recent interest in DirecTV. Today, 11 service providers control 85 percent of the global telecommunications marketplace, and ILECs are responsible for 85 percent of all equipment spending. So, they are without question a force to be reckoned with.

ILEC Summary

So, what are the primary challenges facing the ILECs? First, they are experiencing declining revenues brought on by wireless substitution, cable incursion and broadband IP voice in both the enterprise and end user sectors. Second, because of OPEX issues, they often lose money on DSL deployment. Third, their debt load is high. Finally, uncertainty associated with regulatory decisions leaves them with a number of unanswered questions. Nevertheless, the market is currently theirs to lose because they do own the bulk of the customers. However, they must refocus their efforts on both cost reduction and customer-specific service delivery if they are to hold on to their advantage, and must also develop the logical infrastructure required to offer, deploy, and bill for converged service packages.

We now move our attention to the much-maligned CLECs.

The Secondary Market

Overview

Many companies buy used or refurbished equipment to cut costs. This market is a great place to buy telephones and equipment if you take a little time to do your homework and browse for the best deals. Why not buy refurbished equipment if it can run as good as new, comes with a warranty and saves you money?

Secondary equipment usually costs 30% to 70% less than new. Most vendors will tell you that the older the equipment, the greater the discount. Whatever is scarce costs more money. Phone color also affects value; unpopular colors are scarcer, so cost more.

You can shop for the system you want through the manufacturer or dealer, then call a secondary vendor to see if you can get it for less. Make sure you know your product. The telephone and KSU model numbers indicate analog vs. digital, plus non-visible features like speakerphone.

If you decide to buy from the secondary market rather than a dealer or OEM (Original Equipment Manufacturer), make sure you can install it yourself or that you have someone lined up to install it. Secondary market sources are usually (but not always, so ask) equipment-only.

Many remarketers lease or rent equipment. They also assist in acquiring financing through third-party leasing companies or from the original equipment manufacturer (OEM).

Refurbished equipment is known for its reliability. Some say it’s because it has already endured the burn-in that makes faulty circuits obvious. Refurbished products should be “near new” with all the OEM-provided accessories, up to date software and (at least) the standard warranty.

Make sure you get a user guide with each phone and programming manuals with the systems.

Many remarketers have increased their warranties from 90 days to up to two years. Find out if they provide advance replacement or if you must first return the defective goods. Find out who has to pay the shipping costs.

Remarketers focus heavily on the resale of parts. They should go out of their way to make sure they have in stock the parts you need. Some even track the average rate of failure for various components and stock their shelves according to the forecasted needs of their customers. Find out what the refurbisher’s normal inventory level is for equipment. If they don’t have well-stocked inventory, they may be less equipped to hook you up with the equipment you need when you need it.

Much of the market for secondary systems comes from companies that don’t want to keep their own telecom inventory. Some vendors put serial barcodes on each item, so its history is always known.

Make sure you understand what you are buying. There are many terms that refer to different states of previously-owned and they are used somewhat interchangeably.

The National Association of Telecommunications Dealers (NATD) defines refurbished equipment classes

As Is

Equipment that is bought or sold with no implied warranties. You should expect any condition from inoperative to good. This equipment may not be complete. Buy at your own risk.

Fair Condition Equipment

This equipment is usually in working condition but looks poor.

Good Condition Product

Equipment that is in working condition and looks good.

New

Generally defined as being sold by an authorized vendor of the Original Equipment Manufacturer (OEM) carrying the OEM’s standard warranty.

Like New Excellent condition

Under normal conditions could pass as new, (not used) but is not necessarily in the Original Equipment Manufacturer (OEM) packaging.

Refurbished

Refurbished equipment is cleaned, repaired, and/or painted (panels, covers, etc.) to restore the appearance of the product to a like new condition. It is completely tested, repaired and ready for installation.

Factory Refurbished Equipment

Factory refurbished equipment has been returned to the factory and the factory has replaced the plastic, repaired what’s broken, upgraded circuit boards, or has otherwise reconditioned the equipment to near-new.

Reconditioned

Reconditionedis not a NATD term but it is usually used as synonymous with refurbished.

Before you buy, get a credit report, call other dealers and industry peers. Call the NATD (National Association of Telecommunications Dealers, 561-266-9440) to see if the dealer is a member. If so, see if they are in good standing.

Place several small orders to test dealers before placing a large order.

Call Centers (Telecom Made Simple)

Call Centers
A call center is a place where calls are answered and originated, typically between a company and a customer. Call centers assist customers with requests for new service activation and help with product features and services. A call center usually has many stations for call center agents that communicate with customers. When call agents assist customers, they are typically called customer service representatives (CSRs).

Call centers use telephone systems that usually include sophisticated automatic call distribution (ACD) systems and computer telephone integration (CTI) systems. ACD systems route the incoming calls to the correct (qualified) customer service representative (CSR). CTI systems link the telephone calls to the accounting databases to allow the CSR to see the account history (usually producing a “screen-pop” of information).

Call centers are typically established as either incoming or outgoing. Seldom are they set up together. The main exception is debt collection where there are representatives making outgoing calls and other taking incoming calls. Still, in most cases, the functions are really separate although to the outside client they appear as one.

Incoming (inbound) call centers are set up primarily for some sort of customer service function such as catalogues sales, service or billing inquiries, or technical support. They may be front-ended by an interactive voice response (IVR) systems that take care of customer questions and inquiries that can be handled via computer database look-up’s or via general information recordings.

Traffic monitoring in such centers via ACD and IVR reporting is critical in order to detect and correct bottlenecks and lost calls before such situations becomes crises. Where the representatives are geographically spread, much of this analytical support may be contracted to the carrier that supplies the inbound telephone service. As small sales/service offices become less profitable and are closed, less on-site technical support is available from manufacturers/vendors, and less people are available to provide customer interface, the need for such incoming call centers increases. Consequently this type operation will flourish for some time to come even in face of the Internet.

Figure 1 list the typical costs associated with a call center used for order fulfillment. This table shows that the cost of inbound call center order fulfillment may include a minimum call processing charge in addition to a percentage of sales.


Figure 1: Cost of Inbound Call Center Service

Outbound call centers are primarily geared to two businesses: telephone sales (telemarketing) and debt collection. Many systems use special computer software that dials numbers from a database and once the call is answered passes the call off to an attendant who actually speaks to the person called. The timing of the pass off is critical. Older systems dialed a number and when answered mechanically switched the call causing significant delays between the person answering the call and the representative speaking. Many people routinely hang up on these type calls. Some outbound call centers are designed to deliver a pre-recorded message until an available CSR can be connected. Call center telemarketing services are heavily regulated in the United States and in many other countries. There may be restrictions on whom the call center can contact, the times of day calls can be originated, what the CSR can say, and what they must disclose to the prospective customer.

Telecom : Repeaters

Repeaters are devices or circuits that are located between transmitting and receiving devices to improve the quality the signal that is delivered between them. A repeater obtains some or all of the signal from the transmitter, amplifies and may adjust (change a frequency) or filter the signal, and retransmits the signal to the receiver(s).

Repeaters can be analog or digital. Analog repeaters amplify the received signal for retransmission. Analog repeaters amplify both the desired signal and any noise that is added to the communication lines. This limits the maximum number of analog repeaters that can be used and this limits the maximum distance for analog communication lines. Digital repeaters can receive and recreate digital signals. Digital repeaters are also called regenerative repeaters. The regenerative process allows digital signals to be transferred at great distances with minimal errors at the receiving end.

Channel Multiplexing

Channel multiplexing is a process that divides a single transmission path into several parts that can transfer multiple communication (voice and/or data) channels. Multiplexing may be frequency division (dividing into frequency bands), time division (dividing into time slots), code division (dividing into coded data that randomly overlap), or statistical multiplexing (dynamically assigning portions of channels when activity exists).

When several communications channels are connected over a common channel, a device called a multiplexer is used. The multiplexer combines multiple incoming (input) signals onto one common communications channel through the process of time, frequency, or code sharing. At the other end of the communication line, a demultiplexer device is used to separate the channels (output) at the receiving end.

When a digital channel is divided into multiple digital sub channels, the separate channels are called logical channels. Each logical channel is assigned a portion of the bits from the digital communications channel.


Frequency Division Multiplexing

A device that converts the information signal into a format that is suitable for transmission is called a transmitter. The device that receives and decodes the transmitted signal is called a receiver. When a transmitter and receiver are combined into one device, it is called a transceiver.

Frequency Division Multiplexing (FDM)
Frequency division multiplexing is a process of allowing multiple channels to share a frequency band by dividing up a frequency band into smaller frequency bandwidth channels. Each of these smaller channels provides for a separate communications channel.


Time Division Multiplexing

Figure below shows how a frequency band can be divided into several communication channels. When a device is communicating on a FDM system using a frequency carrier signal, it’s carrier channel is completely occupied by the transmission of the device. For some FDM systems, after it has stopped transmitting, other transceivers may be assigned to that carrier channel frequency. When this process of assigning channels is organized, it is called frequency division multiple access (FDMA). Transceivers in an FDM system typically have the ability to tune to several different carrier channel frequencies.

Carrier signals can co-exist with each other on an FDM system without interference if they are operating at different frequencies. Because the modulating signal slightly changes the carrier signal, this produces small changes in frequency. This results in a single radio signal that occupies a frequency range, depending on the type and amount of information that is changing the electromagnetic wave. The maximum amount of frequency change is typically called the channel bandwidth. Hence, a carrier signal should not typically operate in areas that other radio carrier signals may occupy.

As a carrier signal is modulated (amplitude, frequency, or phase), several other small energy signals at different frequencies are created. Some of the signals produced by the modulation process fall outside the designated frequency bandwidth. Although the amount of energy that falls outside the designated bandwidth is usually small, they may cause interference with other devices that are communicating on other nearby channels.

To help protect from unwanted interference, when multiple carrier signals are operating in an FDM system, a guard band is usually used to protect adjacent carriers from interference. Guard bands are a portion of a resource (frequency or time) that is dedicated to the protection of a communication channel from interference due to radio signal energy or time overlap of signals. While guard bands protect a desired communication channel from interference, the guard band also uses part of the valuable resource (frequency bandwidth or time period) for this protection.

Time Division Multiplexing (TDM)
Time division multiplexing (TDM) is a process of sharing a single carrier channel by dividing the channel into time slots that are shared between simultaneous users of the carrier channel. When a transceiver communicates on a TDM system, it is assigned a specific time position on the carrier channel. By allowing several users to use different time positions (time slots) on a single carrier channel, TDM systems increase their ability to serve multiple users with a limited number of channels by dividing a frequency band into time slots. Time slots are grouped into repetitive frames. Each communication channel is assigned to one (or several) time slot(s) within a frame.

To allow TDM systems to provide continuous voice communication to a transceiver that can only transmit for brief periods, TDM systems use digital signal processing to characterize and compress digital signals into short time-slices. Figure below shows how a single carrier channel is time-sliced into three communication channels. Transceiver number 1 is communicating on time slot number 1 and mobile radio number 2 is communicating on time slot number 3. Each frame on this communication system has three time slots.

Code Division Multiplexing (CDM)
Code division multiplexing uses a method of spreading an information signal using different codes on a wide bandwidth communication channel (typically digital signals). For CDM channels, the frequency bandwidth of the carrier channel is much larger than the bandwidth of the original information signal. Because the channel bandwidth is very large, information from other channels operating in the same frequency band is relatively small. This allows multiple communications channels to operate in the same frequency bandwidth at the same time. There are various forms of CDM. The most popular forms of spread spectrum include frequency hopping and direct spread spectrum.

Frequency hopping is a multiplexing technology where transceivers may share a frequency band by transmitting for brief periods of time on an individual carrier channels and then hopping to other carrier channels to continue transmission. Each transceiver is assigned to a particular hopping pattern and collisions that occur are random. These errors only cause a loss of small amounts of data that may be fixed through error detection and correction methods.

Direct spread spectrum is relatively new commercialized (verses militarized) modulation technique that is used primarily in cellular and satellite systems. Direct sequence spread spectrum systems mix a relatively long digital code with a small amount of communication data (information signal) to produce a combined signal that is spread over a relatively wide frequency band. To receive the signal, the long code is used to extract the original signal.

Because the energy is spread over a wide bandwidth, multiple spread spectrum channels with different codes can co-exist with minimal interference. Figure 3.8 shows how a single direct sequence spread spectrum communication channel can have several channels. In this example, there are 3 different code patterns that are used for communication channels. When a receiver uses the reference code, a direct sequence spread spectrum system can build a mask as shown in Figure below for each conversation allowing only that information which falls within the mask to be transmitted or received.


Code Division Multiplexing

Digital Speech Interpolation (DSI)
In addition to multiplexing through channel division, statistical multiplexing can also be used by distributing transmission of a communications channel over idle portions of multiplexed channels. An example of statistical multiplexing is digital speech interpolation (DSI). DSI is a technique that dynamically allocates time slots for voice or data transmission to a user only when the have voice or data activity. This increases the system capacity as transmission for other users can occur when others are silent.

Digital speech interpolation (DSI) is a digital form of a process known as time assigned speech interpolation (TASI). The DSI technique that dynamically allocates channels (usually time slots) for voice or data transmission to a user only when the have voice or data activity. This increases the system capacity as transmission for other users can occur when others are silent.

A system that has DSI capability assigns information transmission based in speech activity. The DSI system senses activities of speech signals and availability of communication channels in a system and dynamically transmits information signals on available communications channels. Because speech conversation is composed of pauses and alternating directions of communications (usually one person speaks at a time), the use of TASI increases the efficiency of a communications system of approximately 2:1. For example, a 96 channel communications circuit that uses TASI can provide service approximately 192 calls.

Figure below shows the process of multiplexing using DSI. This diagram shows a communication circuit that has 96 independent communication channels (one communication link that has 96 time slots). The DSI system monitors the activity of each voice conversation (a voice channel) using a voice activity detector (VAD). The VAD is an electronic circuit that senses the activity (or absence) of voice signals. This is used to inhibit a transmission signal during periods of voice inactivity.


Digital Speech Interpolation (DSI)

When the VAD detects that speech is active, the DSI system assigns the information to specific time slots on the communications channel. The DSI transmitter system identifies the voice channel at the beginning of the transmission so the DSI receiver can assign it to an output voice channel. When the voice activity detector senses a pause in communication, the DSI transmitter sends an ending message on the channel allowing the channel to be placed back into a pool of available communication channels. The next time the speech activity detector senses the voice channel is again active, the DSI transmitter will select a channel from the pool of available communication channels and the process begins again. Each time, the DSI receiver will assign the information to the correct output voice channel.

Simple Telecom : Basic Concepts

Most telecommunication customers are served by copper cable (twisted pair or coax) terminated by the local telephone company in a telephone network interface box, called a network termination (NT). The NT is normally located on the side of the building. The network termination isolates the network from the wiring inside the building. From the NT, the “inside wiring” extends the telephone cable to all internal wall and floor jacks.

To reduce the number of copper pairs, telephone systems use a hybrid transmission system to allow both transmission and reception on a single pair of copper wires. By combining both transmit and receive audio signals using a special hybrid combiner, only one-pair of wires is required to operate a standard home telephone. These two lines are routinely referred to as “tip and ring.” This single pair of wires also provides dial tone, dialing pulses or tones, ringing (high voltage signal), and a talk path.

Most of the information that is transferred in voice conversation occurs at frequencies below 3,300 cycles per second (Hertz or Hz) and above 300 Hz. This allows telephone systems to restrict the audio frequency range for voice grade circuits from 300Hz to 3300Hz. Using a restricted frequency range reduces the transmission line and system switching performance requirements. The limiting of the audio frequency range is accomplished through the use of devices known as band-pass filters. Band-pass filters strongly attenuate signal frequencies above and below specific frequencies.

It is possible to send digital information through the hybrid network through the use of a modulator/demodulator (MoDem). The MoDem converts digital signals into analog tones that can be transmitted on standard telephone lines.

Telephone transmission lines can be divided into access lines (local loops) and interconnection lines (trunks). Often referred to as 1FB’s or B1’s, local loops refer to all two-wire voice grade connections between a residence or place of business and the telephone company’s serving end office (e.g., where the dial tone originates). Interconnection trunks refer to high capacity groups of circuits connecting switching sites such as end offices or other switching centers.

Simple Telecom : Transmission Systems

Overview,
Transmission systems interconnect communication devices (end nodes) by guiding signal energy in a particular direction or directions through a transmission medium such as copper, air, or glass. A transmission system will have at least one transmitting device, a transmission medium, and a receiving device. The transmitting communication device is capable of converting an information signal into a form of electrical, electromagnetic wave (radio), or optical signal that allow the information to be transferred through the transmission medium. The receiving communication device converts the transmitted signal into another form that can be used by the device or other devices that are connected to it. Transmission systems can be unidirectional (one direction) or they can be bi-directional (two directions).

The basic types of transmission mediums include copper wire, coaxial cable, free space/air, fiber optic cable, and mechanical transmission line. Copper and coaxial wire is primarily used for low to moderate frequency transmission over a few miles. Free space/air systems can transmit hundreds of miles but have limited bandwidth and are susceptible to noise interference. Fiber optic cable is capable of carrying high-speed data signals (as light pulses) over thousands of miles. Mechanical (acoustic wave) transmission lines transmit over very short distances (only a few millimeters) and are used for signal filtering components.

Different types of transmission lines have varying performance characteristics and may be susceptible to interference during signal transmission. These characteristics include the available frequency bandwidth (frequency response), how much signal leakage may occur (cross talk), and the susceptibility of absorbing other signals (signal ingress). The construction of the transmission line itself may cause distortions in the transmitted signal. This includes unterminated line splices (bridge tap reflections), poor line splices, and line resistance (signal attenuation). Other characteristics such as varying delays to different frequency ranges may cause group dispersion (smearing) of the desired signal.

To allow devices to communicate with each other over a transmission line, carrier systems specify the signal types and levels along with specific protocol controls (communication rules). These carrier systems are often specific to the transmission medium such as copper or fiber. Some of the more popular carrier systems include plain old telephone service (POTS), digital signaling carrier (DSx), digital subscriber line (DSL), and optical carrier (OCx).

To coordinate the transmission line, signaling messages are sent between communication devices. Some of these control messages are sent along with the data on the transmission line (called in-band signaling) and others are sent through another path or network (called out-of-band signaling).

In some cases, a transmission path may only be a portion of a path (a logical path) through a transmission line. The length of a transmission may be extended through the use of amplifiers or repeaters.

Telecom : Protocols

Protocols are the precise set of rules and a syntax that govern the accurate transfer of information within a communications network. Protocols are used within a communication system to establish, carry out, and terminate communication circuits. Protocols are also used to coordinate billing and customer care systems, manage network devices, and any other process that requires coordinated communication and control.

There are thousands of different protocols used in communications systems. Usually, protocols are grouped into families of protocols so they can serve specific types of networks and services. When interconnecting different networks, protocols need to be converted.

Protocol conversion involves the translation of the protocols of one system to those of another to enable different types of equipment, such as data terminals and computers, to communicate. This is done by an inter-working function (IWF). An IWF system (such as a data bridge) adapts the communications between two different types of networks. Protocol conversion may be used to interconnect circuit switched or packet switched networks.

Communication Systems: Simplex, Half Duplex, Full Duplex (FDX), Time Division Duplex (TDD)

Communication systems transfer information between 2 or more users. Communications systems may transfer information in one direction at a time on the same channel (simplex), in two directions on different time at different times (half duplex), or simultaneously on two different channels (full duplex). There are various approaches including TDD that allow the appearance of full duplex operation although the actual transmission system uses simplex or half duplex operation.

Simplex
Simplex communication allows the transmission of information between users, but only one direction at a time on the same channel or frequency. The common use of Simplex systems is traditional television or audio broadcast radio systems that transmit a signal from a single transmitter to many receivers.

Half Duplex
Half duplex communication provides the ability to transfer voice or data information in either direction between communications devices but not at the same time. The information may be transmitted on the same frequency or divided into different channels. When divided into different channels, one channel of frequency is used for transmitting and the other channel or frequency is used for receiving.

The use of different frequencies is common in half duplex radio transmission because the transmitter and receiver are commonly connected to the same antenna. If the same transmitter and receiver frequency were used, the high transmitter power would probably destroy the receiver circuitry.

Full Duplex (FDX)
Full Duplex communication is the process of transferring of voice or data signals in both directions at the same time. Full duplex operation normally assigns the transmitter and receiver to different communication channels. When the communications system uses two different frequencies for simultaneous communication, it is called frequency division duplex (FDD). One frequency is used to communicate in one direction and the other frequency is required to communicate in the opposite direction.

The definition of full duplex becomes confusing when it is applied to the end result of simultaneous voice and data communication. This is because it is possible to provide information at the input and output of a communication system while not actually sending the information simultaneously in a communication system. When a communication system provides for simultaneous two-way communication by time sharing, it is called time division duplex (TDD).

Time Division Duplex (TDD)
Time division duplex (TDD) communication uses a single channel or frequency to provide simultaneous two-way communications between devices by time-sharing. When using TDD, one device transmits (device 1), the other device listens (device 2) for a short period of time. After the transmission is complete, the devices reverse their role so device 1 becomes a receiver and device 2 becomes a transmitter. The process continually repeats itself so data appears to flow in both directions simultaneously. Figure below shows the basic operation of FDD and TDD system.

Telecom Made Simple : Modulation

Signal modulation is the process of modifying the characteristics of a carrier wave signal using an information signal (such as voice or data). The characteristics that can be changed include amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM). A pure electrical, radio, or optical carrier signal carries no information aside from either being in on or off state. When the carrier signal is modified from a normalized state, it is called a modulated signal. This modulated signal is the carrier of the information that is used to modify the carrier signal. When the carrier signal is received, its signal is compared to an unmodulated signal to reverse the process (called demodulation). This allows the extraction of the original information signal. A carrier wave signal can be carried by wire, fiber, or electromagnetic waves transmitted through the air (radio).

When a carrier signal is modulated, the frequency changes above and below its reference frequency. The difference between the upper and lower maximum frequency changes is called the bandwidth. The relationship between the amount of frequency bandwidth of an information signal (the baseband) and the channel bandwidth of the modulated carrier determines if the system is a narrowband or wideband system. Narrowband systems have a relatively small communications channel bandwidth, typically below 100 kbps. When the bandwidth of the broadband carrier is much higher than the bandwidth of the information source, it is called a wideband system.

The device that modifies the carrier signal with the information source (baseband signal) is called a modulator. An assembly or device that combines the function of modulating and demodulating signals is called a Modulator/DEModulator (MODEM).

Combined types of Modulation
Today’s sophisticated modulation systems can use all three variable parameters: frequency, amplitude, or timing (phase) at the same time to transfer analog or digital information. One of the more popular forms of combined modulation technologies is Quadrature Amplitude Modulation (QAM). QAM is a modulation technique that enables two information signals to modulate a single carrier frequency. The two different signals’ amplitude modulates two samples of the carrier that are of the same frequency, but differ in phase by 90 degrees. The resultant two signals can be added together and both signals recovered at a decoder where they are then demodulated 90 degrees apart.