Telecommunications Systems

Telecommunications Systems

So as we proceed through this material, try not to get frustrated with the constant mix of services, technological discussions, and costing issues. From time to time, we may also introduce some extra technical notes that are for the more technically astute but can be ignored by the novice trying to progress through the industry. As you read about a topic, do so with a focus on systems, rather than individual technologies. We have tried to make these somewhat stand-alone chapters, yet we have also tied them together in bundles of three or four chapters to formulate a final telecommunications system. Do what you must to understand the information, but do not force it as you read. The pieces will all come together throughout the groupings of topics.

What Constitutes a Telecommunications System

A network is a series of interconnections that form a cohesive and ubiquitous connectivity arrangement when all tied together. That sounds rather vague, so let’s look at the components of what constitutes the telecommunications network. The telecommunications network referred to here is the one that was built around voice communications but has been undergoing a metamorphosis for the past two decades. The convergence of voice and data is nothing new; we have been trying to run data over a voice network since the 1970s. However, to run data over the voice network, we had to make the data look like voice. This caused significant problems for the data because the voice network was noisy and error-prone. Reliability was a dream and integrity was unattainable, no matter what the price.

Generally speaking, a network is a series of interconnection points. The telephone companies over the years have been developing the connections throughout the world so that a level of cost-effective services can be achieved and their return on investment (ROI) can be met. As a matter of due course, whenever a customer wants a particular form of service, the traditional carriers offer two answers:

1. It cannot be done technically.
2. The tariff will not allow us to do that!

Regardless what the question happened to be, the telephone carriers were constantly the delay and the limiting factor in meeting the needs and demands for data and voice communications.
In order to facilitate our interconnections, the telephone companies installed wires to the customer’s door. The wiring was selected as the most economical to satisfy the need and the ROI equation. Consequently, the telephone companies installed the least expensive wiring possible. Because they were primarily satisfying the demand for voice communications, they installed a thin wire (26-gauge) to most customers whose locations were within a mile or two from the central office. At the demarcation point, they installed the least expensive termination device (RJ-11), satisfying the standard two-wire unshielded twisted pair communications infrastructure. The position of the demarcation point depended on the legal issues involved. In the early days of the telephone network, the telephone companies owned everything, so they ran the wires to an interface point and then connected their telephone equipment to the wires at the customer’s end. The point here is that the telephone sets were essentially commodity-priced items requiring little special effect or treatment.

When the data communications industry began during the late 1950s, the telephone companies began to charge an inordinate amount of money to accommodate this different service. Functionally, they were in the voice business and not the data business. As a matter of fact, to this day, most telephone companies do not know how to spell the word data ! They profess that they understand this technology, but when faced with tough decisions or generic questions, few of their people can even talk about the services. How sad, they will be left behind if they do not change quickly. New regulations in the U.S., in effect since the divestiture agreement, changed this demarcation point to the entrance of the customer’s building. From there, the customer hooked up whatever equipment was desired. Few people remember that in early 1980, a 2400-bps modem cost $10,000. The items that customers purchase from a myriad of other sources include all the pieces we see during the convergence process. In the rest of the world today, where full divestiture or privatization has not yet taken place, the telephone companies (or PTTs) still own the equipment. Other areas of the world have a hybrid system under which customers might or might not own their equipment. The combinations of this arrangement are almost limitless, depending on the degree of privatization and deregulation. However, the one characteristic that is common in most of the world to date is that the local provider owns the wires from the outside world to the entrance of the customer’s building. This local loop is now under constant attack from the wireless providers offering satellite service, local multipoint distribution services (LMDS), and multi-channel multi-point distribution services (MMDS). Moreover, the CATV companies have installed coaxial cable or fiber, if new wiring has been installed, and they offer the interconnection to business and residential consumers alike. The CLECs have also emerged as formidable foes to the local providers. They are installing fiber to many corporate clients (or buildings) with less expense and long-term write-off issues. The CLECs are literally walking away from the telephone companies and the local loop. Add the xDSL family of products to this equation and the telephone companies are running out of options. The telephone companies today have approximately 15,000 xDSL connections across the U.S., whereas the CLECs have over 200,000. Moreover, the cable TV companies have close to 800,000 cable modems installed for high-speed Internet access. This is where the CATV companies see the convergence taking place. CLECs are also seeing the convergence in the local loop, and with xDSL in their potpourri of offerings, they are actually nudging the local telephone
companies aside.

A Topology of Connections Is Used

In the local loop, the topological layout of the wires has traditionally been a single-wire pair or multiple pairs of wires strung to the customer’s location. Just how many pairs of wires are needed for the connection of a single line set to a telecommunications system and network? The answer (one pair) is obvious. However, other types of services, such as digital circuits and connections, require two pairs. The use of a single or dual pair of wires has been the norm. More recently, the local providers have been installing a fourpair (eight wires) connection to the customer location. The end user is now using separate voice lines, separate fax lines, and separate data communications hookups. Each of these requires a two-wire interface from the LEC. However, if a CATV provider has the technology installed, they can get a single coax to satisfy the voice, fax, data, and highspeed Internet access on a single interface, proving the convergence is rapidly occurring at the local loop. It is far less expensive to install a coax running all services (TV, voice, and data) than multiple pairs of wire, so the topology is a dedicated local connection of one or more pairs from the telephone provider to the customer location or a shared coax from the CATV supplier. This is called a star and/or shared star-bus configuration . The telephone company connection to the customer originates from a centralized point called a central office (CO). The provider at this point might be using a different topology. Either a star configuration to a hierarchy of other locations in the network layout or a ring can be used. The ring is becoming a far more prevalent method of connection for the local Telcos. Although we might also show the ring as a triangle, it is still a functional and logical ring. These star/ring or star/bus combinations constitute the bulk of the networking topologies today. Remember one fundamental fact: the telephone network was designed to carry analog electrical signals across a pair of wires to recreate a voice conversation at both ends. This network has been built to carry voice and does a reasonable job of doing so. Only recently have we been transmitting other forms of communication, such as facsimile, data, and video.

The telephone switch (such as DMS-100 or #5ESS) makes routing decisions based on some parameter, such as the digits dialed by the customer. These decisions are made very quickly and a cross-connection is made in logic. This means that the switch sets up a logical connection to another set of wires. Throughout this network, more or fewer connections are installed, depending on the anticipated calling patterns of the user population. Sometimes there are many connections among many offices. At other times, it can be simple with single connections. The telephone companies have begun to see a shift in their traffic over the past few years. More data traffic is being generated across the networks than ever before. As a matter of fact, 1996 marked the first year that as much data was carried on the network as voice. Since that time, data has continued its escalated growth pattern, whereas voice has been stable.


The Local Loop

Our interface to the telephone company network is the single-line telephone line, which has been installed for decades and is written off after 30 or 40 years. Each subscriber or customer is delivered at least one pair of wires per telephone line. There are exceptions to this rule, such as when the telephone company might have multiple users sharing a single pair of wires. If the number of users demanding telephone service exceeds the number of pairs available, a Telco might offer the service on a party-line or shared set of wires. It is in this outside plant, from the CO to the customer location, that 90 percent of all problems occur. This is not to imply that the Telco is doing a lousy job of delivering service to the customer. In the analog dial-up telephone network, each pair of the local loop is designed to carry a single telephone call to service voice conversations. This is a proven technology that works for the most part and continues to get better as the technologies advance. What has just been described is the connection at the local portion of the network. From there, the local connectivity must be extended out to other locations in and around a metropolitan area or across the country. The connections to other types of offices are then required.


The Telecommunications Network

Prior to 1984, most of the network was owned by AT&T through its local Bell operating telephone companies. A layered hierarchy of office connections was designed around a five-level architecture. Each of these layers was designed around the concept of call completion. The offices were connected together with wires of various types called trunks . These trunks can be twisted pairs of wire, coaxial cables (like the CATV wire), radio (such as microwave), or fiber optics. As the convergence of voice and data networks continues, we see a revisitation to the older technologies as well as the new ones. Fiber is still the preferred medium from a carrier’s perspective. However, microwave radio is making a comeback in our telecommunications systems, linking door-to-door private line services. Carrying voice, data, video, and high-speed Internet access is a natural for a microwave system. Lightbased systems, however, are limited in their use by telephone companies. It has been user demand that has brought infrared light and now SONET-based infrared systems in place. Recently, the introduction of an unguided light introduced by Lucent Technologies operates at speeds up to 2.4 Gbps with a promised speed of up to 10 Gbps by end of 2000. This offers the connectivity to almost anyone who can afford the system, because the right of way is no longer an issue.


The Network Hierarchy (Post-1984)

After 1984, ownership of the network took a dramatic turn. AT&T separated itself from the Bell Operating Companies (BOCs), opening the door for more competition and new ventures. Equal access became a reality and users were no longer frustrated in their attempts to open their telecommunications networks to competition.


The Public-Switched Network

The U.S. public-switched network is the largest and the best in the world. Over the years, the network has penetrated to even the most remote locations around the country. The primary call-carrying capacity in the U.S. is done through the public-switched network. Because this is the environment AT&T and the BOCs built, we still refer to it as the Bell System. However, as we’ve already seen, significant changes have taken place to change that environment. The public network enables access to the end office, connects through the long-distance network, and delivers to the end. This makes the cycle complete. Many companies use the switched network exclusively, while others have created variations depending on need, finances, and size. The network is dynamic enough, however, to pass the call along longer routes through the hierarchy to complete the call in the first attempt wherever possible.


The North American Numbering Plan

The network-numbering plan was designed to enable a quick and discreet connection to any telephone in the country. The North American Numbering Plan , as it is called, works on a series of 10 numbers. As progress occurs, the use of Local Number Portability (LNP) and Intelligent Networks (IN) enables the competitors to break in and offer new services to the consumer. Note that there have been some changes in this numbering plan. When it originally was formulated, the telephone numbers were divided into three sets of sequences. The area codes were set to designate high-volume usage and enabled some number recognition tied to a state boundary. With the convergence in full swing, the numbering plan became a bottleneck. Now with the use of LNP, the Numbering Plan will completely become obsolete as we know it. No longer will we recognize the number by an area code and correlate it to a specific geographic area. LNP will make the number a fully portable entity. Moreover, 10-digit dialing in the age of convergence becomes the norm because of the multitude of area codes that will reside in a state.


Private Networks

Many companies created or built their own private networks in the past. These networks are usually cost-justified or based on the availability of lines, facilities, and special needs. Often these networks employ a mix of technologies, such as private microwaves, satellite communications, fiber optics, and infrared transmission. The convergence of the networks has further been deployed because of the mix of services that the telephone companies did not service well. Many companies with private networks have been subjected to criticisms because the networks were misunderstood. Often the networks were based on voice savings and could not be justified. Now that the telecommunications networks and systems are merging, the demand for higher-speed and more availability is driving either a private network or a hybrid.


Hybrid Networks

Some companies have to decide whether to use a private- or public-switched network for their voice, data, video, and Internet needs. Therefore, these organizations use a mix of services based on both private and public networks. The high-end usage is connected via private facilities creating a Virtual Private Network (VPN), while the lower-volume locations utilize the switched network. Installing private-line facilities comes from the integration of voice, data, video, graphics, and facsimile transmissions. Now VPNs are used on the Internet to guarantee speed, throughput, quality of service, and reliability. This new wave of VPN takes up where the voice VPNs left off. Only by combining these services across a common circuitry will many organizations realize a savings.


Equipment
Equipment in the telephony and telecommunications business is highly varied and complex. The mix of goods and services is as large as the human imagination, yet the standard types are the ones that constitute the ends on the network. The convergence and computerization of our equipment over the years has led to significant variations. The devices that hook up to the network are covered in various other chapters, but here is a summary of certain connections and their functions in the network:

• The Private branch exchange ( PBX)
• The modem (data communications device)
• The multiplexer (enables more users on a single line)
• Automatic call distributor (ACD)
• Voice mail system (VMS)
• Automated attendant (AA)
• Radio systems
• Cellular telephones
• Facsimile machines
• CATV connections
• Web-enabled call centers
• Integrated voice recognition and response systems

This is a sampling of the types of equipment and services you will encounter in dealing with Telecommunications Systems and convergence in this industry.

Telecommunications Concepts

After a few ideas have sunk in, we move on to a high-speed data networking strategy, with the use of Frame Relay. After Frame Relay, we discuss the use of ATM for its merits and benefits. Next, we take the convergence a step farther and delve into the Frame and ATM inter networking applications—still a great way to carry our voice and data no matter how we slice and dice it.

Just when we thought it was safe to use these high-speed services across the WAN, we realize that local access is a problem. Entering into the discussion is the high-speed convergence in the local loop arena with the use of CATV and cable modems to access the Internet at LAN speeds. Mix in a little xDSL, and we start the fires burning on the local wires. The use of copper wires or cable TV is the hot issue in data access. From the discussion of the local loop, we then see the comparisons of a wireless local loop with LMDS and MMDS. These techniques are all based on a form of Microwave, so the comparison of microwave radio techniques is shown. Wireless portability is another hot area in the marketplace. Therefore, we compare and contrast the use of GSM, cellular, and personal communications’ services and capacities. Convergence is only as good as one’s ability to place the voice and data on the same links.

Leaving the low-end wireless services behind, we then enter into a discussion of the sky wave and satellite transmission for voice and data. No satellite transmission discussion would be worth anything without paying homage to the TCP and IP protocols on the satellite networks. Yet, the satellite services are now facing direct competition where the Low Earth Orbit satellite strategies are becoming ever popular. The use of Teledesic, Iridium, or Globalstar systems are merely transport systems. These pull the pieces together and will offer voice and data transmission for years to come. One could not go too far with the wireless-only world, so we back up and begin to
contrast the use of the wired world again. This time, we look at T1, T2, and T3 on copper or coax cable, which is a journey down memory lane for some. However, by adding a little fiber to the diet, we provide these digital architectures on SONET or SDH services. SONET makes the T1 and T3 look like fun! Topics include the ability to carry Frame Relay and ATM as the networks are now beginning to meld together. SONET is good, but if we use an older form of multiplexing (wavelength), we can get more yet from the fibers. So, we look at the benefits of dense-wave division multiplexing on the fiber to carry more SONET and more data.

With the infrastructure kicked around, the logical step is to complete this tour of the telecommunications arena with the introduction of the Internet, intranets, and extranets. Wow, this stuff really does come together! Using the Internet or the other two forms of nets, we can then carry our data transparently. What would convergence be without the voice? Therefore, the next step is to look at the use of voice over Internet Protocols (IPs).

Lastly, we have to come up with a management system to control all the pieces that we have grouped and bonded together. This is in the form of a simple network management protocol (SNMP) as the network management tool of choice. If all the converged pieces work, there is no issue. However, with all the variants discussed in this book, we must believe that “Murphy is alive and well!” Thus, all the pieces are formed together by groups, to form a homogenous network of Internets.

Basic Telecommunications Systems

When the FCC began removing regulatory barriers for the long distance and customer premises equipment (CPE) markets, its goal was to increase competition through the number of suppliers in these markets. Recently, consumers have begun to enjoy lower prices and new bundled service offerings. The local and long distance markets are examples of the new direction taken by the FCC in the 1980s to eliminate and mitigate the traditional telephone monopoly into a set of competitive markets. Although these two components of the monopoly have been stripped away, barriers still exist at the local access network—the portion of the public network that extends between the IEC network and the end user. The local loop and the basic telecommunications infrastructure are not as readily available as one would like to think. The growth of private network alternatives improves with facilities-based competition in the transport of communications services. The industry realizes that more than 500 competitive local exchange carriers have grown out of the deregulation of the monopolies. These CLECs include cable television networks, wireless telephone networks, local area networks (LANs), and metropolitan area networks. Incumbent local exchange carriers (ILECs) indicate that their networks are continually evolving into a multimedia platform capable of delivering a rich variety of text, imaging, and messaging services as a direct response to the competition. Many suggest that their networks are wide open, for all competitors. Imagine an open network —a network with well-defined interfaces accessible to all—allowing an unlimited number of entrants a means to offer competitive services limited only by their imagination and the capabilities of the local loop network facilities. If natural monopolies are still in the local exchange network, open access to these network resources must be fostered to promote a competitive market in spite of the monopolistic nature of the ILECs. The FCC continues to wrestle with how far it has to go and what requirements are necessary to open and equal access to the network. Network unbundling, the process of breaking the network into separate functional elements, opens the local access to competition. CLECs select unbundled components they need to provide their own service. If the unbundled price is still too expensive, the service provider will provide its own private resources. This is the facilities-based provider. All too often, we hear about new suppliers who offer high-speed services, better than the incumbent. Yet, these suppliers are typically using the Bell System’s wires to get to the consumer’s door. The only change that occurs is the person to whom we send the bill. Hardly a competitive local networking strategy. As a result, the new providers
(CATV, wireless local loop, IEC, and facilities-based CLEC) are now in the mode to provide their own facilities.

Components of the Telecommunications Networks

Telecommunications network components fall into logical or physical elements. A logical element is a software-defined network (SDN) or virtual private network (VPN) feature or capability. This SDN or VPN feature can be as simple as the number translation performed in a switch to establish a call. Switching systems have evolved into the use of external signaling systems to set up and tear down the call. These external physical and logical components formulate the basis of a network element. Moreover, Intelligent Networks (and Advanced Intelligent Networks) have surpassed the wildest expectations of the service provider. These logical extensions of the network bear higher revenue while opening the network up to a myriad of new services. Number portability can also be categorized into the logical elements because the number switching and logic are no longer bound to a specific system. A physical element is the actual switching element, such as the link or the matrices used internally. A network is made up of a unique sequence of logical elements implemented by physical elements. Given the local exchange network and local transport markets, open mandates had to be considered because the LEC has the power to stall competition. In many documented cases the LECs have purposefully dragged their feet to stall the competition and to discredit the new provider in the eyes of the customer. This is a matter of survival of the fittest. The ILECs have the edge over the network components because their networks were built over the past 120 + years. This is the basis for the deregulatory efforts in the networks, because the LECs are fighting to survive the onslaught of new providers who are in the cream-skimming mode. If access mandates are necessary, to what degree? These and other issues are driving the technological innovation, competition at the local
loop, and the development of higher capacity services in a very competitive manner.

The Local Loop

So much attention has been parlayed on the local loop. Nevertheless, is it a realistic expectation to use the network facilities for future high-speed services? Would the newer providers, such as the CATV companies, have an edge over the ILECs? These issues are the foundation of the network of the new millennium. The new providers will use whatever technology is available to attack the competition, including

• CATV
• Fiber-based architectures (FTTC, FTTH, HFC)
• Wireless microwave systems
• Wireless third-generation cellular systems
• Infrared and laser based wireless architectures
• Satellite and DSS type services
Regardless of the technology used, the demand never seems to be satisfied. Therefore, the field of competitors will continue to metamorphose as the demand dictates and as the revenues continue to attract new business.

The Movement Toward Fiber Optic Networks

A transmission link transports information from one location to another in a usable and understandable format. The three functional attributes of this link are-

1. Capacity
2. Condition
3. Quality of Service
The deregulation of the local exchange networks has led to significant improvements in one of the following criteria:
• Access to network capacity
• Access to intermediate points along the transmission path The transmission path may include pieces of the existing copper or newer fiber-based network architectures. The current copper-based loop limits opportunities.
• The transmission distances associated with the subscriber loop limit the amount of bandwidth available over twisted wire pair roughly to the DS1 rate of 1.5 Mbps. As broadband services become increasingly popular, the copper network severely constrains the broadband services.
• The current switched-star architecture runs at least one dedicated twisted pair from the central office to each customer’s door without any intermediate locations available to unbundle the transport segment. This precludes a lot of the innovation desired by the end user. Although the current copper-based network is unattractive to unbundle the physical transmission components, fiber-based networks offer many more opportunities. The local access network can be improved by telephone companies by deploying fiber in the future. The central office, nodes at remote sites and the curbside pedestal can all be improved with fiber-based architectures. These nodes serve as flexibility points where signals can be switched or multiplexed to the appropriate destination. A small percentage of lines are served by digital loop carrier (DLC) systems that incorporate a second flexibility point into the architecture at the remote node. The third flexibility point at the pedestal has been proposed for fiber-to-the-curb systems in the future. The bandwidth limitations of a fiber system are not due to the intrinsic properties of the
fiber, but the limitations of the switching, multiplexing, and transmission equipment connected to the fiber. This opens the world up for a myriad of new service offerings when fiber makes it to the consumer’s door. Third parties like Qwest and Level 3 are becoming the carrier’s carrier. They will install the fiber to the pedestal, the door, or to the backbone and sell the capacity to the ILEC or CLEC. This produces many attractive alternatives to the broadband networks for the future. No longer will bandwidth be the constraining factor; the application or the computer will be the bottleneck.

Because of the tremendous bandwidth available with fiber optic cable and the technological improvements in SONET and Dense Wave Division Multiplexing, virtually unlimited bandwidth will be available. This statement of course is contingent on the following caveats:

• The abundance of bandwidth is not likely to appear for some time.
• This bandwidth is available only over the fiber links. Yet, installation of new technology is a slow process. Fiber will be deployed in hybrid network architectures, which continue to utilize existing portions of the copper network. Consequently, until fiber is deployed all the way to the customer premises, portions of the network will continue to present the same speed and throughput limitations.

Digital Transfer Systems

The switching and multiplexing techniques characteristic of the transmission systems within the network are all digital. Currently, the network employs a synchronous transfer mode (STM) technique for switching and multiplexing these digital signals. The broadband networks of the future will continue to utilize a synchronous transmission hierarchy using the SONET standards defined by the ITU. SONET describes a family of broadband digital transport signals operating in 50 Mbps increments. As a result, wherever SONET equipment is used, the standard interfaces at the central office, remote nodes, or subscriber premises will be multiples of these rates. Above the physical layer, however, changes are now underway that move away from the
synchronous communications modes. The asynchronous transfer mode (ATM) is the preferred method of transporting at the data link layer. ATM uses the best of packet switching and routing techniques to carry information signals, regardless of the desired bandwidth, over one high-speed switching fabric. Using fixed-length cells, the information is processed at higher speeds, reducing some of the original latency in the network. These cells then combine with the cells of other signals across a single highspeed channel like a SONET OC − 48. In time division multiplexing (TDM), timing is crucial. In ATM, timing is statistically multiplexed (STDM) so the timing is less crucial at the data link layer. The cells fit into the payload of the SONET frame structure for transmission where the timing is again used by the physical layer devices. ATM will use a combined switching and multiplexing service at the cell level. Continued use of SONET multiplexers will combine and separate SONET signals carrying ATM cells. What distinguishes ATM from a synchronous approach is that subscribers have the ability to customize their use of the bandwidth without being constrained to the channel data rates.

When the intelligent networks are fully implemented, the logical network components will be separated from the physical switching element—where the physical component of a current digital switch consists of 64 Kbps (DS0) access to the network switch. ATM should improve the capability to separate the physical switching elements of the network. The attributes of the ATM switch, which could facilitate more modularity, is the bandwidth flexibility. Because each information signal is segmented into cells, switching is performed in much smaller increments. Current digital switching elements switch a DS0 signal whether the full bandwidth is needed or not. With ATM, the switching element resources can be much more efficiently matched to the bandwidth requirements of the user. Access to the ATM switch will be specified according to the maximum data rate forecasted for the particular access arrangement, instead of specifying the number of DS0 circuits required, as is the case today with digital switches.

The Intelligent Networks of Tomorrow

The ILECs have been developing the AIN to provide new services or to customize current services based on the user demand. The Central Office switches contain the necessary software to facilitate these enhanced features. The manufacturers of the systems have fully embodied their application software with the operating systems software within the switch to create a simple interface for the carriers. When new features are added, the integrated software must be fully tested by the switch manufacturer. The limitations of a centralized architecture caused the vendors and manufacturers concern. Now, as intelligent services are deployed, the movement is to a distributed architecture and Intelligent Peripheral devices on the network. The LECs use a network architecture, which enables efficient and rapid network deployment. The single most important feature of AIN is its flexibility to configure the network according to the characteristics of the service. The modular architecture allows the addition of adjunct processors, such as voice processing equipment, data communication gateways, video services, and directory look-up features to the network without major modifications. These peripheral devices (servers) provide local customer database information and act like the intelligent centralized architectures of old. The basic architecture of the AIN takes these application functions and breaks them into a
collection of functionally specific components. Ultimately, AIN allows modifications to application software without having to alter the operating system of the switch.


Summary

The telecommunications systems include the variations of the local loop and the changes taking place within that first (or last) mile. As the migration moves away from the local copper-based cable plant (a slow evolution for sure), the movement will be to other forms of communications subsystems to include the use of

• Fiber optics
• Coax cable
• Radio-based systems
• Light-based systems
• Hybrids of the preceding

These changes will take users and carriers alike into the new millennium. Using the CATV modem technologies on coax, the fiber-based SONET architectures in the backbone (and ultimately in the local loop), and copper wires in the xDSL technologies all combine to bring higher speed access. After access is accomplished, the use of the SONET-based protocols and multiplexing systems creates an environment for the orchestration of newer services and features that will be bandwidth intensive. The SONET systems will be used to step up to the
challenges of the 2000s. ATM will add a new dimension to the access methods and the transport of the broadband information through the use of STDM and cell-based transmission. No longer will the network suppliers have to commit specific fixed bandwidth to an application that only rarely uses the service. Instead, the services will merely use the cells as necessary to perform the functionality needed. Wireless local loop services are relatively new in the broadband arena but will play a significant role in the future. The untethered ability to access the network no matter where you are will be attractive to a large new population of users. Access to low-speed
voice and data services are achievable today. However, the demand for real-time voice, data, video, and multimedia applications from a portable device is what the new generation of networks must accommodate. The broadband convergence will set the stage for all future development. Today speeds are set up in the kilobits to megabits per second range. The broadband networks of the future will have to deal with demands for multi-megabit speeds up to the gigabit per second speeds. Through each interface, the carriers must be able to preserve
as much of their infrastructure as possible so that forklift technological changes are not forced upon them. The business case for the evolution of the broadband convergence is one that mimics a classical business model. Using a 7-15 year return on investment model, the carriers must see the benefit of profitability before they install the architectural changes demanded today.