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:
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.
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.
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.
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.
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).
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.
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.
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.
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 Authentication Systems.”