Syed V. Ahamed

Current Digital Networks

Public domain networks and totally private networks constitute the extremes of network ownership and thus its organization and management. Whereas there is considerable freedom in the architecture and operation of the private network, the public domain network architecture and operation tend to be standardized and streamlined (see Section 4). In the discussion presented here, acknowledged international standards are used in context to the public domain networks and for ISDN. There are two major architectural variations (circuit-switched and packet-switched) in the networks used in the public domain.

Networks and the Information Society

Vital differences exist between environments for human communication and those for computer communication. Human communication has been studied by social scientists in great detail and is of no direct consequence in the context of this chapter. However, almost all network data communication (except that used to control the network functions) is for eventual use in human interpretation and decision making. At this first and also at the final man-machine interface, users exchange information to and from the network in a multiplicity of modes, (for example, voice, visual, graphic, touch-tone, keyboard, scanners, fax, or even dialing). A degree of excellence in network service is a realistic expectation, as well as accuracy and rapid response from the network. The quality and response that the intelligent networks (INs) can provide far exceeds that of the conventional communication networks. For example, if visual communication in the high definition television (HDTV) mode is needed from a broadband intelligent network, the network must allocate about two orders of magnitude more bandwidth compared to the bandwidth for voice communication. Hence, the networks that provide integrated service need much greater sophistication to accommodate users and their individual needs.

Optical Lightwave Systems in Existing Networks

To become economically feasible, broadband networks have to be optical, even though individual links may be microwave, coaxial, or even satellite based. The recent technological strides in making very high quality fibers and optical devices, and the availability of ATM switches, all point to the use of optical systems becoming more and more entrenched in current and future networks. In this Chapter, the existing networks where optical systems are an integral part are identified. The emphasis is on the telecommunication environment and the role these in which optical systems have significantly altered the economics of both broadband and wideband data communication. A recent study of a typical developing country in the Middle East has indicated that any delay in bringing optical systems into major telecommunication centers is a significant source of negative cash flow to the telephone business, and more than that, the lingering demand of services will not be met (in any economically viable fashion) except by establishing OC-3 or at least OC-1 links between the population centers of the country.

Recent American Intelligent Networks

There are two major directions of force on the evolution of the public domain intelligent networks (INs) in the United States. First, the carriers of major data transport facilities around the country are evolving a special type of network intelligence to monitor and implement the network performance requirement from a data-throughput point of view. Optimal utilization of network switching and transmission facilities to maximize revenues is the major design criterion. With the advent of high-speed fiber optic systems that deploy multiple gigabit capacity in digital pipes, it is essential to be able to add, drop, and cross-connect channels appropriately from the digital superhighways spanning the country. Second, regional operations in the more densely populated areas of the United States are developing the capability to provide new intelligent network services (IN/1, IN/1+, and IN/2 architecture). In addition, the integrated services digital network (ISDN) capabilities for distributing data are being implemented by way of the ISDN switches, which are being implemented throughout the country.

Integrated Medical Systems

Routine medical care and functions are specially amenable to computer and network processing. In this chapter, we indicate a methodology for processing the medical functions of any patient by the medical community using intelligent computer systems. It is our objective to present architectures to demonstrate that machines can enhance the productivity and efficiency of medical environments by confining the procedural steps, bookkeeping functions, and resource allocation to specially tailored computer systems. The human functions of pattern matching, judgment, and ultimate decision-making are also facilitated by a backbone of computers and networks organized to perform knowledge-based AI functions. Similar existing and effective environments currently in use are the corporate Management Information Systems/Decision Support Systems (MIS/DSS), where decision-making tasks and analysis are performed routinely, and the stock market environments where vast numbers of routine transactions are handled quickly and inexpensively.

The AT&T View of Intelligent Networks (INs)

In order to facilitate the orderly evolution of network intelligence in the public domain, Bell Communications Research, a research and development facility of the Regional Bell Operating Companies (RBOCs), has proposed three distinct architectural variations (IN/1, IN/1+, and IN/2). Considerable collaboration in the phased introduction of these networks is essential to maintain uniformity and consistency of services throughout the nation. Vendors from all nations participate in supplying the networks components, interfaces, and software modules. To maintain any semblance of order, ITU (formerly CCITT) and ANSI publish stringent standards and well-defined protocol. Most companies follow these standards and implement networks, such as the CCS7 network and packet-switched networks. Based upon signaling and typical architecture, networks evolve, such as the 800 network, software defined network (SDN), and others. These rudimentary networks meet all the basic interface and signaling requirements of the first version of the public domain intelligent network, that is, IN/1.

Advanced Intelligent Networks (AINs)

Chapter 8, “The AT&T View of Intelligent Networks (INs),” through Chapter 12, “Global Intelligent Networks (INs),” focused on public domain intelligent networks and the AT&T concept (Type-A) and Bellcore concept (Type-B) of intelligent networks (INs). This chapter discusses the more sophisticated INs from a conceptual and functional perspective. These INs can be readily implemented in private networks and the more rapidly evolving arena of intelligent networks tailored for business communication systems. Section 13–1 discusses networks using existing and evolving technologies for INs. Such networks can utilize concepts more advanced than the IN/2 concept presented in Chapter 11, “Intelligent Networks/2 (IN/2),” and the Universal Information Services Network (UISN) presented in Chapter 8, “The AT&T View of Intelligent Networks (INs).” Universal information services provided by UISN are evolving into an integral part of the Advanced Intelligent Network (AIN) services.

Data up to PRISDN Rates

The BRISDN, HO and H1 rates in the loop plant imply the presence of a modern signaling system, if not a full-fledged ITU-T (formerly CCITT) standard SS7 system. Signaling is crucial to the viability of any ISDN service promised by the all-digital networks of the future. The transition can only be gradual since the telephone systems have massive capital investments already buried and sunk as copper wires. Traditional switching systems and the sustained effort make these various components and devices serve as a cogent and coherent communication facility. The vertical integration of these components is a tedious and well planned activity. The major concern of the owners for these systems is the utilization of the capital already committed to its full potential to realize the expected revenue stream. It is here that the higher rates start to become attractive to the network owners such as the European PTTs, AT&T (before the divestiture of 1996), the Bell Northerns and the Telecoms around the world. The challenges from the “wireless lastmile” and the “fiber to the curb” (if not “fiber to the home”) are not trivial. The challenge is akin to the challenge that the bubble technology of the 1970s posed to the traditional disk technology for secondary memories. It is this challenge that forced the costs of Winchester disk storage systems to tumble down through the late 1970s and 1980s that led to the demise of the bubble memories

Data at Prisdn Rate

Various coding techniques are being considered for higher rates ranging from DS-1 over the existing twisted wire-pairs spanning the ISDN Central Offices to the Subscriber, and up to 155 Mbps from data distribution centers to desk tops. Rates higher than the basic information rate at 144 kbps, i.e., the H0 (384 kbps), 768 kbps, are discussed in Chapter 11. Most telephone networks have at least one metallic connection to the customers from the Central Office or a remote distribution facility. Enhanced use of this existing copper facility to transmit high-speed data appears to be a viable choice towards the ISDN video and imaging services. Simulation results for increased rate with ideal equalizers are presented in this Chapter. The use of fiber in the distribution plant facilitates the availability of very high rate data ranging from 51.64 Mbps (or the standard OC-1 rate) through 2.4 Gbps (OC-48 rate) at the network distribution centers. More recently, the OC-3 rate is gaining most popularity for the fiber coaxial ATM systems. However, the use of fiber to every home is not economical at this stage, because of the existing copper wire-pairs to customer residences and almost all businesses. There is also a lack of justification for such high rates (even the OC-1 rate) to every customer.

Performance of Trellis Coding

Trellis codes combine channel coding and modulation techniques for data transmission over band limited channels. Theoretically, it achieves significant coding gains over conventional uncoded multilevel modulation without compromising bandwidth efficiency. In this Chapter, the effect of trellis encoding algorithms are studied, and the effectiveness for Carrier Serving Area (CSA) loop environments in the presence of imperfect echo cancellation at primary rate ISDN applications are evaluated. A basic methodology for the simulation of trellis codes for QAM clusters is utilized. The effect of trellis codes for 16 and 64 QAM is outlined. Results for the coded 16 and 64 QAM constellations for three typical CSA loops with 60 dB of echo cancellations are presented along with the effects of trellis codes on the entire CSA loop population.