Telecommunication System
The intended audience is transportation professionals who may be involved with, or responsible for any phase in the life cycle of a traffic signal or freeway management control network. This includes all public or private “practitioners″ (e.g., managers, supervisors, engineers, planners, or technicians) involved with any issue or decision (e.g., policy, program, funding, or system implementation) and who may directly or indirectly influence the performance of traffic on local arteries or freeway facilities. These activities may include, but not be limited to, planning and design, operational strategies, programs, and services that support continuous management of travel and control of traffic, and the technology infrastructure to provide these capabilities
Telecommunications systems as part of the National ITS Architecture are the connecting pathways that bind the various elements of traffic signal, freeway management, and transportation systems together. The National ITS Architecture “sausage diagram” indicates how these elements are bound together, but does not specify the telecommunication system. The developers of the National ITS Architecture understood that each telecommunication system would be uniquely designed to meet the needs of each project.
The significant diversity of communications technologies and the overall complexity of traffic signal, freeway management, and transportation systems have created a need for traffic and transportation professionals to implement the Systems Engineering Process (SEP). This handbook provides a summary (Chapter 4) of how to apply an SEP to the development of a telecommunications system, for traffic signal and freeway management systems development.
The OSI model is an International Standards Organization (ISO) standard that defines a framework for implementing telecommunication and software protocols. The OSI model is organized into seven hierarchal layers. Control is passed from one layer to the next starting at the application layer and proceeding down to each successive layer and back as required for any given process. Most of the functionality of the OSI model exists in all communications systems – however, two or three layers may be combined into one. The most significant role of the OSI model is to serve as a reference for the development of other protocol stacks. A detailed explanation of the OSI Model is provided in the Addendum section of this handbook. Table 1-1, provides a list of the OSI Model Protocol Stack
The concept of the telephone instrument – and the system that allows it to work – was so strong that most communication technology during the past 125 years was developed to support an efficient voice communication network. It wasn’t until 2004 that major telecommunication carriers announced the need to develop, and support, a network designed for the purpose of transporting digital data
Bulgaria doesn’t have a standard system for telephone numbers. Some areas have a four-digit dialling code (e.g. Albena, 5722) while others have only a one- or two-digit code (e.g. Subscriber numbers can range from three to seven digits.
Such a Hybrid Fiber-Coax telecommunication system is generally known in the art. The idea of HFC is to put different telecommunication signals, received via optical fibers, onto distinct video channels and to apply these channels to the coaxial cable, preferably according to the Frequency Division Multiple Access [FDMA] structure. Each channel is modulated on a different carrier signal of which the frequency is in the video band. The outputs of the signal mixer means are generally connected to distinct inputs of the combiner means via drivers.
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