How to plan a Wi-Fi deployment: Coverage and Capacity
In this series, we are looking at the process of determining what you need in your WLAN network
When planning to deploy a wireless network, you must first determine the number of clients you expect to serve, the type of traffic you expect on the network, the amount of throughput you want the network to provide, and the number of access points you need and where to mount them for optimal coverage.
This blog is the first in a 3-part series summarizing these initial steps up to the point where you have gathered network needs and assessed RF environment conditions.
Setting Coverage and Capacity Goals
The major initial tasks of any wireless deployment involve setting coverage and capacity goals, creating a predictive model that calculates how many access points (APs) you need and where to place them to satisfy those goals within the physical environment of the site, verifying the accuracy of the predictions by performing a manual site survey, and then making any adjustments as necessary.
How to Determine Network Needs
Determine network needs by interviewing stakeholders and, if replacing an existing network, by using network monitoring tools to learn about its characteristics.
The following factors must be considered when determining the type and number of APs to deploy:
- the maximum number of client devices that will be concurrently transmitting and receiving traffic on each SSID
- the types and capabilities of the client devices
- the types of applications they will use
- the mobility of users while on the network
- the minimum throughput levels you want to provide
A common way to gather this information is to interview people such as site managers as well as the people who will be using the network. You can conduct interviews in person as well as send questionnaires to them.
- For new wireless deployments, start by asking the people at each site to estimate how many users—and, more importantly, how many wireless devices--they anticipate will be active on the network simultaneously. Ask them what types of devices will be used and what the users’ objectives are. Managers’ estimates about employees and company devices should be fairly accurate because they already know how many employees and devices will be on the network, the device types, and their intended uses.
- Regarding the number of visitors using wireless devices, estimates will necessarily be less precise but still worth gathering. Ask not only about their immediate requirements but what they imagine they will need five years from now. In many cases, you will receive business objectives (shorter checkout lines in stores) that you must translate into technical objectives (suggest using mobile POS). Educating people about how technical solutions can satisfy business objectives is part of the planning process.
- When replacing an existing wireless network, ask the same questions but in addition to collecting future estimates, also get statistics and observations about the network being replaced. Activity and performance on the current network can be measured with various network monitoring tools that regularly poll, probe, and scan networks; remote collectors that get data from agents running on network devices; and inline appliances that monitor and analyze the packets that flow through them. Try to obtain access to such measurements if they are available.
- You can then take the information you have gathered and check LAN and WLAN traffic studies to develop bandwidth targets for the different types of users, client devices, and traffic types. Also, because you are replacing an existing network, it must have had some shortcomings that prompted the change. Find out what problems people had with the network and where in the building they tended to occur.
- It is also important to learn as much as you can about the wired network with which the wireless devices must integrate, such as its addressing scheme and topology.
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