Chapter 4. Developing the Telecommunication System


Telecommunication systems can be very complex and difficult to design because there is usually more than one way to meet requirements. Often, several communication protocols must be used in the final design. This chapter attempts to provide the traffic engineer, and traffic system project manager, with a suggested process for developing the design and specification for a communications network to support traffic signal and freeway management systems. A theme that is repeated throughout this handbook is that the design of a communications network to support roadway and transportation functions is not a stand-alone process. The determination of functionality and selection of options must be done as an integrated part of the overall traffic management system design. Personnel responsible for the development of the communications system should be full members of the overall project team.

Central to the development of the communication system is the fact that it is there to serve the requirements of the overall project. Communication project personnel should attend general project planning meetings. If new roadway construction, or roadway modification, is part of the overall project, communication engineers should be included.

This chapter is organized into six primary sections. First, a recommendation of qualifications for a telecommunications consultant, including types of experience and education. The next three sections are devoted to the Requirements Document. The development of a complete requirements document is essential to the proper implementation of a telecommunications system. The final section concludes this chapter with some basic recommendations for managing the communication project.

Selecting the Consultant

This section provides guidelines for selecting an engineering / communications consultant with the right qualifications. Three basic qualification areas must be considered when selecting a qualified communication consultant: experience, education, project background. And, these four (4) basic rules apply in making the selection:

There's no substitute for experience.

Qualified applicants need to demonstrate a good understanding of how each element of a communication system will impact on the viability of a whole system. There are only a few engineering schools offering degree programs in telecommunications. Technology changes faster than the professors can write new text books.

Communication Engineers don't design traffic (or freeway management) systems don't use a traffic engineer to design a communication network.

There's no substitute for experience. Consulting firms (or individuals) should have at least 10 years (as individuals or combined with other team members) of experience in analysis, design and implementation of communications systems. Ten years may seem like a very heavy requirement, but will assure that the engineer (or firm) will have a broad range and depth of experiences. Most communication system engineers are used to the idea of wearing many hats. And, as technology changes, there is a greater need to have a broad application experience than a specific focus. There is also a need to understand legacy technologies. In many circumstances, the communication engineer must design a system that allows for the use of legacy technology, adds current technologies, and provides for implementation of future technologies.

During the course of writing this handbook, more than a dozen new IEEE standards relating to Ethernet and the application of Ethernet to wireless and broadband wireless were either published, or sent to committees for final acceptance, and there are about a dozen more in development. Since the early-1990s there has been a focus – by the telecommunication carriers – to move from primary support of analog voice based services to data transmission services. During that same period, Transportation agencies – on a broad scale – embraced the use of technology to support their operations. Their use of telecommunication technologies has very rapidly evolved from analog systems to digital data systems and the use of wireless. There is a general convergence of voice based and data based telecommunications services. This creates a greater need for communication engineers to develop a broad based background. During the transition period, it is important for telecommunication system designers to have an understanding of both analog and digital communication systems.

Different Telecommunication Design Specialties

Many specialties have engineers that primarily do design and others that focus on construction or manufacturing. The same is true for telecommunications. There are engineers that only do design and those that work on the construction of the systems. For most ITS projects it's a good idea to have at least one member of the design team that has experience in both the design and implementation of communication systems. Most communication system designers have learned valuable lessons by actually having to make their design work. Larger firms may have significant breadth of experience in developing traffic signal and freeway management systems. However, you'll want to look closely at their experience with communications systems design and deployment. If you are making a choice between two or more qualified firms, take a hard look at both corporate and individual personnel experience.

Many IT personnel have significant experience with the deployment of Local Area Networks, but the may lack a background with the types of systems required for freeway management and traffic signals. Local area networks are generally deployed within a building. The personnel designing those systems don't have to worry about location of the media infrastructure, or bringing power to a communications cabinet, or using equipment that can survive extremes of temperature and moisture. On the other hand, make certain that an experienced IT person is involved in design of the control center.

Types of Telecommunications Experience

Communication system engineers should have the following experience (this can be defined as either direct experience or the management of individuals and firms doing the work):

Knowledge of Telecommunications Systems Relationships

Seek out engineering talent with a good understanding of how each element of the communication system will impact on the viability of the whole system. The following should be applied in the search for qualified firms and personnel:

Educational Qualifications

Education is important, however, there are only a few Universities offering degree programs for communication system design and/or engineering. Most engineering schools offer courses in communication technology. However, the courses are designed to provide the student with a fundamental understanding of how the technologies work. Additional points:

Requirements Analysis

The communication system requirements document is based on the overall concept of operations for the traffic/transportation system. Keep in mind that the communication system is a supporting element of the overall system. It is important for the project team to make certain that the communication engineer is fully aware of the concept of operations for the main project.

The requirements analysis sets the tone for the whole project. Organizing the requirements analysis into primary elements will help the project team visualize the interactive relationships. The organization chart (figure 4-1) is a suggested representation of one method of creating the visualization. The reader may have another preferred way to show the relationships. There is no "right" or "wrong" way to present the information. Simply be aware that creating a requirements analysis for the communications system starts with the overall program requirements analysis.

organization chart showing the relationship of the communications systems used for traffic signal and freeway management to the major related systems. The communication systems field equipment links area is at the top of the chart leading to related systems: traveler information (leading to changeable message signs), CCTV (leading to video image broadband link and PTZ control low speed data link), and radar detectors.

Figure 4-1: Field Devices Communication Link Requirements

Figure 4-2 shows the relationships of the major functional elements of a proposed system and the general communication link required. In chapter 3 we looked at how the national architecture is used to structure a relationship between various elements of a freeway management system. The requirements analysis is the process for telling systems designers what system functionality is needed. If the whole project was laid out in a block diagram, figure 4-2 would represent one portion of the overall diagram. This diagram represents the communication links for the field equipment.

Once the role of the communication system – in terms of the overall program – is established, the communication engineer should focus on developing this aspect of the requirements document. Following is an example of a communications system centric requirements relationship diagram:

organization chart showing how the communication system is related to overall system functionality. The incident management system is at the top of the chart leading to functional elements (leading to lane occupancy and traveler information systems), technology elements (leading to radar detection devices and CCTV), and operational elements (leading to communication system). The communication system connects to the others.

Figure 4-2: Chart Relationship Communication to Overall System

The chart is generic. There is no attempt to specify technology only general requirements. Communication technology strategy is determined by examination of the specific system requirements. The communication system is one of the operational elements of the Incident Management System. The chart shows the relationship of communications systems to the whole project and individual elements. The design engineer will be forced to explain all of the links and not overlook any requirements.

The "Gee-Whiz" Factor

It is important to approach the communications system design with the right attitude. There is a tendency to look at the "gee-whiz" of communications technologies and assume they will support project requirements. Project managers and engineers should get past this phase of the requirements analysis as quickly as possible. Streaming Video over an IP Multi-cast network is not the only solution to provide for the distribution of video. The communications systems are designed, and implemented, in support of the traffic management system – not vice-versa!

However, there is a valid reason for using the "gee-whiz" factor. Properly employed, it can lead to some innovative uses of technology. An example of the innovative use (within the transportation environment) is presented in Chapter 7. The project team should look at the "if anything is possible" scenario. It is perfectly acceptable to ask the communication engineer to look at system options using leading (sometimes called "bleeding") edge technology. The communication engineer gains an understanding of project team expectations. In return, the project team is provided with enough information to make the right decisions.

Completing the requirements analysis will provide the project development team with a clear understanding of the viable alternatives, the role of the communication system as part of the overall project and a potential budget for the communication system.

The communication requirements analysis should be completed as a part of the overall project concept of operations and requirements analysis. When practical, wait until the project requirements analysis is almost complete. The communication system is there to serve the needs of the overall traffic/transportation system.

Keep expectations realistic – ask questions

Recognize that system reliability and quality are necessary and desirable. But, also recognize that many features and benefits have a cost. Use the "KISS" (keep it simple stupid) principle of system design whenever practical. The requirements document should help answer the following:

A Systematic Engineering Approach to the Requirements Analysis

There is no magic formula, just the tried and true "five Ws and H" question and answer technique – what, where, when, who, why, and how. The questions are not complex, but the individual answers may point to a series of complex design and implementation issues for the required communications system.

Key points to consider:

Ask the Questions

What is the purpose of the proposed traffic/transportation system? Look at the original project statement of purpose for this answer. Relate the communication requirements to the reason for the project's existence. Most projects require bi-directional information flow. Many require bandwidth to support video from CCTV cameras.

Where will it be located? Location of the project has an impact on overall design of the physical infrastructure and the cost of construction of a communication network. If the project is to be constructed in a narrow mountain pass, it will create challenges that won't be encountered on a local city street. Where is the TMC to be located in relation to the field equipment?

When (over what period of time) will it be deployed? This is a question that is directed to the communication network. Does the project plan call for implementation over a relatively short period – one to two years – or a long period – five to eight years?

Who will operate and maintain the system? Consider whether the communication system will require that operational personnel activate various functions of the communication equipment. All of the following may have an impact on the overall design of the communication system:

Answering the question of who will operate and maintain the system will lead to operator and maintenance staff qualification requirements. DOTs have personnel regulations and guidelines that have to be met in order to provide staffing. Private contractors supplying operational and maintenance personnel may have to meet other criteria. Outsourcing might be a reasonable consideration.

Why is the traffic system being deployed? This may seem redundant to the question of "what" is being deployed, but at this point the project team will focus on the specific type of traffic system. "Why" might be answered with a look at the research that was used to justify the deployment of the traffic/transportation system. The communication engineers responsible for analyzing and designing the communications system need to be provided with a good understanding of how various types of traffic/transportation systems work. This will lead to a design of the communication system based on the functions of the traffic/transportation equipment. Examples of various systems that should be explained:

There are a number of "How" questions to be answered and most are interrelated.

Creating the Requirements Document

Once the basic questions have been asked and answered the communications engineer will present a preliminary communication systems requirements document. The project design team should review the proposed requirements document, and consider the following:

  1. Merging Expectations with Reality – At this point, it is time to look at the requirements for the communications system and reconcile original expectations with the realities of what is possible. Compare expectations with the preliminary communication systems design. Ask the communication engineer to fully explain how technical and financial barriers impact on expectations. Challenge the requirements document.
  2. What Type of Communications System Should I Build? Now that the requirements document has been presented, the project team needs to determine if it should follow all of the suggestions made in the requirements document. There may be new information that was not available when the communications design team started to work on the requirements document.

Three Basic Systems Types:

Developing a Budget

Once the requirements have been reviewed against expectations, it's time to develop a "real" communication system budget.


A few simple guidelines to follow:

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