How to: Define Wireless Network Requirements

August 22, 2008

The first step in implementing a wireless network is defining the network’s requirements. In this tutorial, Wi-Fi expert Jim Geier offers guidance on how to identify valid requirements.

Requirements define what a wireless network must do, which provides the foundation for the design. Requirements for a wireless network include needs, such as signal coverage in elevators and support for voice telephony. Leave the technical details, such as specific technologies (such as 2.4GHz vs. 5GHz 802.11n), components, and configuration settings to the designers after all requirements are well-defined and agreed upon.

Requirements to consider

Before implementing a wireless network, consider the following types of requirements:

Applications

Ultimately, the wireless network must support user applications, so be sure to fully define them in the requirements. They could be general office applications, such as Web browsing, e-mail, and file transfer, or they could be wireless patient monitoring in a hospital or voice telephony in a warehouse. Be as specific as possible. The application requirements enable designers to specify applicable throughput, technologies, and products when designing the system.

Environment

Provide a description of the environment where the wireless network will operate. For buildings, include the floor plan, type of construction, and possible locations for mounting access points. For outdoor areas, include satellite images, aerial photographs, or drawings. Walk through the areas to verify accuracy of these items. Take lots of photos. In addition to a visible inspection, consider performing an RF site survey. All of this will capture the environment in a way that will help designers choose the right technical elements.

Coverage areas

This describes where users will need access to the wireless network. They might only need connectivity in their offices and conference rooms, but they may also need connectivity inside power utility rooms and the cafeteria. Also, carefully think about whether coverage is needed in stairwells, elevators, and parking garages. These are difficult-to-cover areas and can drive the cost of the wireless network very high. By properly specifying coverage areas, you’ll avoid the unnecessary expense of installing access points where they’re not needed. Unless obvious, also identify the country where the wireless network will operate. This impacts channel planning and product availability.

End users

Be sure to identify whether users are mobile or stationary, which provides a basis for including enhanced roaming in the design. Mobile users will move about the facility and possibly roam across IP domains, creating a need to manage IP addresses dynamically. Some users, however, may be stationary, such as those using wireless desktops.

Client devices

You should specify the client devices (and existing client radios) to ensure the solution accommodates them in the most effective manner. For example, you could specify that users will have laptops running Microsoft Vista with integrated 802.11b/g radios. This provides a basis for deciding on the type of client radios to specify for other client devices during the design and whether there’s a need to support legacy devices (i.e., 802.11b/g).

Existing infrastructure

Be certain to describe all existing applicable infrastructure. Identify locations and availability of communications closets, switch types, and available ports, PoE interfaces, fiber runs, conduit, authentication servers, VPN ports, and operational support systems.

Security

Describe the sensitivity of the information that will traverse the wireless network. If possible, cite existing corporate wireless security policies. You’ll likely need to require encryption and authentication of all client devices. Be sure to give security requirements plenty of thought so that you design a solution that will protect the company’s valuable resources.

Funding

The requirements stage of a wireless network project is a good time to ask how much money is available. If funding limits are known, then you’ll know how much there is to work with when designing the system. In most cases, however, a company will ask how much the system will cost. You’ll then need to define the requirements and design the system before giving a cost estimate. In this situation, consider stating requirements with options, such as with and without signal coverage provided in parking garages. You can then provide two separate cost estimates based on optional signal coverage.

Schedules

Of course a company will generally want the wireless network installed “yesterday,” but we all know that’s impossible. You’ll need to nail down a realistic completion date, though, and plan accordingly. For example, you may be defining requirements in July, and a retail store will likely demand that a wireless price marking application be installed by the end of September.

After defining these elements, you should have enough information to design the solution. Before proceeding, though, ensure you have consensus from all stakeholders, such as executives, users, and the operational support organization. If requirements are not clear enough, you should do some prototyping or pilot testing to fully understand requirements before spending money on the design and installation.

For more tutorials by Jim Geier, read “Troubleshooting 802.1x Missing Supplicant Problems (Part I),” “Minimize WLAN Interference,” and “Troubleshooting 802.1x Port-Based Authenti c ation Systems.”

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Jim Geier

Jim Geier is an independent consultant and author with 30 years experience planning, designing, analyzing and implementing communications systems, wireless networks, and mobile devices. Jim is the author of over a dozen books on mobile and wireless topics, such as including Designing and Deploying 802.11ac Wireless Networks (Cisco Press), Implementing 802.1X Security Solutions (Wiley), Wireless Networking Handbook (New Riders) and Network Re-engineering (McGraw-Hill). He has been an active participant within IEEE standards organizations, such as the IEEE 802.11 Working Group, and the Wi-Fi Alliance. He has served as Chairman of the IEEE Computer Society, Dayton Section, and various conferences. He has served as a testifying expert for patent litigation cases focusing on technologies dealing with Wi-Fi, Bluetooth, mobile devices, cellular systems, wireless network protocols, network security mechanisms, location systems, and application data management protocols. Jim’s education includes bachelor’s and master’s degrees in electrical engineering, with emphasis in mobile devices / systems and wireless communications.