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To access the contents, click the chapter and section titles.
Wireless Networking Handbook
(Publisher: Macmillan Computer Publishing)
Author(s): Jim Geier
ISBN: 156205631x
Publication Date: 09/01/96
CHAPTER 6 Defining Requirements for Wireless Networks
Requirements are crucial in all development projectsthey provide the basis for design, implementation, and support of the system or product (see fig. 6.1). Incomplete or missing requirements are the major reasons for unsuccessful projects, resulting in 6080 percent of system defects that eventually surface late in the development phase or after delivery to the users. These system defects are very time-consuming and expensive to correct. Shabby up-front requirements also lead to the continual stream of new requirements that fill in for inadequacies throughout the project. New requirements cause a great deal of rework, extending development time and costs. Requirements that are ambiguous, untestable, and most of all, not able to fully satisfy needs of potential users contribute to high development costs, lagging time-to-market, and unhappy users and customers. Thus, organizations must emphasize the definition of requirements to keep their heads above water.
Figure 6.1 Requirementsthe foundation of design, implementation, and support.
A large part of planning the requirements phase is to calculate how much work will be necessary to determine what the requirements are. For all projects, thoroughly assess requirements for security and interfacing to existing systems; keep in mind, however, that the amount of time spent analyzing the users requirements differs depending on whether you are developing software applications or using off-the-shelf products. You should spend more time defining user functional requirements for an application development than for the deployment of just the network infrastructure. The reason is that users spend more time interfacing directly with applications rather than the network components.
For example, a project meant to create a specific graphical user interface (GUI) for nurses to access healthcare records from a centralized database would require a detailed analysis of the business processes the nurses work involves. A project that creates a wireless network infrastructure for off-the-shelf applications, however, would not need such detail. In that case, you only need to examine high-level business processes and product requirements in order to select the correct wireless components.
Although the system analyst is generally responsible for specifying requirements, the rest of the project team should be involved as well. This chapter describes the types of requirements you need to define and discusses the following steps that the project team should take when defining requirements:
- Elicit information
- Define the requirements
- Update the project plan
Types of Requirements
Before eliciting information, you should have an understanding of the type of requirements you are attempting to define. Figure 6.2 lists common requirement types. Knowing the requirement types helps you focus on gathering the best information related to user needs and system requirements.
Figure 6.2 Common types of requirements.
User Profile and Interface Requirements
The user profile requirement identifies the attributes of each person who will be utilizing the system, providing human factors that designers can use to better select or develop applications. A persons in-depth experience with Windows-based applications, for example, would prompt the design team to procure or develop standard Windows applications. In addition, the profile assists the installation team when assigning user names. The user profile should identify the persons name, job title and description, level of networking experience, and knowledge of applications. Users will require some form of interface to the systems databases and other resources. Most interfaces today are graphical client-serverbased applications that run on Microsoft Windows. The user interface requirement should indicate screen layouts and leveling of menus.
Functional Requirements
Functional requirements describe what the users and the organization expect the system to do. Therefore, functional requirements run parallel to the tasks and actions users perform. For example, the need to enter packing slip information from all received shipments into a database is a functional requirement. In most cases, application software implements functional requirements.
Application Requirements
Application requirements specify that the system can utilize specific applications. For instance, an organization that uses Microsoft Office for word processing and spreadsheets should indicate that standard as an application requirement. An organization moving from paper-based inventory control to a centralized computer system, however, would probably delay the selection of the actual application until the beginning of the design phase (after all other requirements are known).
Information Flow Requirements
Business processes within companies depend heavily on communications. To complete their tasks, people need to communicate with other people and systems. Because the networks primary role is the support of communication, you must fully define information flow requirements. For this requirement, specify the information path flow between people and systems, types and formats of information sent, frequency of information transmission, and maximum allowable error rates. These requirements will provide a basis for the selection of network components, such as the network interface card, medium, and so forth.
Mobility Requirements
Mobility requirements describe the movement of the users when performing their tasks. Mobility requirements should distinguish whether the degree of movement is continuous or periodic.
When the user or network component must have the capability to utilize network resources while physically moving, they are said to be in continuous movement. Examples of users requiring access to network resources while continuously moving include emergency vehicles, military personnel on a battleground, delivery services, and healthcare professionals.
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