Saturday, February 5, 2011

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
• 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.


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.

1 comment:

  1. Thanks for putting the efforts on gathering useful content and sharing here. You can find more networking and telecom related question and answers in the below forum.

    Networking and telecom question and answers