Following Design Processes

    It is important to use proper design methodology when designing wireless networks. WiFi has evolved numerous times since it was first implemented, yet I still see very outdated or flat out wrong ways of designing a wireless network. The biggest thing I find is that many places do not follow the design process when choosing to install a new or update an existing WLAN. Essentially we are throwing hardware at a design problem and expecting it to work. In this post, I'll cover the proper way to design a wireless network according to CWNP's guidance. Thank you CWDP-303 official study guide from CWNP for providing me with the ability to do so!

 Define

    This might be one of the most overlooked parts of the design process. This step in the process sets the foundation for a good, well thought out design. Instead of simply getting a floor plan and jumping straight into a network planner, let's understand who or what we are designing for. During this stage, meeting with the customer or stakeholders are very important. You will be asking them a laundry list of questions, and for good reason! You need to understand from their perspective how the network will be used, and then ask again how it will really be used. The reason I say this is because you might hear something like this for a K-12 in this example:

"We use WiFi everywhere, all parts of the building should be covered. Each student will have a chromebook, and 2 other devices, assume 3 devices per student and account for growth."

    Wi-Fi everywhere may not be possible due to budget constraints. Do they mean every maintenance closet and bathroom needs -67 RSSI or basic connectivity? Are they prepared to purchase additional APs to make this happen. What applications are the students using? Are they streaming video, and if so what quality? How many devices can a student actively use at one time? Typically one device is used and others are just associated to the AP, not being actively used. There is a maximum to the amount of devices we can use at once, most of us only have two hands and our attention spans might only handle so much.

    You may also see the requirement for a certain speed. This is potentially dangerous thinking as the customer may be expecting the speeds of their home network that uses 80MHz channels or of their old, improper design that used too wide of channels. Now that you're designing the network, you may be increasing AP density to where only 20 MHz channels are possible. I ran into this personally at a university that was used to 80MHz channels everywhere. Dropping to 20 or 40 MHz channels meant a "50% or greater decrease in speeds". Basically downplaying the multitude of co-channel interference that was experienced day by day. It is important to have a conversation with the customer to set expectations and give your reasoning. 

Asking more than just "What do you use the network for?" is imperative. Ask follow up questions and deeply understand their network, how they are using it, and how they intend to use it in the future. This design may be in use for at least the lifetime of the APs being installed, potentially through the lifecycles of multiple AP replacements.

Design

    During this step, you'll take the information gathered from the Define phase and begin the process of designing the network. You'll probably go on site as well to discover more about the location and do surveys. Taking pictures of expected mounting locations, doing AP on a stick surveys to validate installation locations, and measure wall attenuation. You may also want to validate any floor plans given to you to ensure there are no differences between the floor plan and the actual location, renovations do happen and often floorplans are forgotten about.

    Keep in mind you'll need to evaluate the wired network as well. Old switching that cannot provide 30W of power or with only a 1Gbps uplink is not adequate for modern 6E networks. Many 6E APs even require greater than 30W of power as well! Cabling may need to be updated as well. This information may be gathered during the Define phase as well.

Implement

    As the name suggests, you'll get to take your awesome new WLAN design and implement it! This may include installing new cabling, switches, and mounting APs. You'll need to adequately configure each AP and switch if you're tasked with the LAN portion as well. Configuring controllers, radio profiles, SSIDs, AP groups, etc. All of this will need to be documented as you may not be running the network after implementation or for the long term. The network needs to be maintained by someone, and they will need documentation on how it is currently running. Everything you do and configure should be documented and handed over to the customer. This will enable them to manage the network without your intervention.

Validate and Optimize

    An often, and most likely most often forgotten about step is validating the WLAN. What you created in Ekahau or Hamina might be great, but the real world might be different. If there are coverage holes or insufficiencies with the deployment, that needs to be addressed. The best way to validate your WLAN design is by doing a full site survey. More than just basic validation of services like DHCP/DNS to check for configuration issues. Maybe an AP was installed incorrectly, or is missing altogether. Maybe a cable is crimped incorrectly and only providing 100Mbps to the AP. Any number of issues can occur during an install. You could have a 'perfect' design, but the installation was botched, the customer could see it as your fault even though it is not a design problem. It is your job to validate the installation as it can only benefit both you and the customer to do so. You will walk away with a job well done and a happy customer if you follow this process.

Source:

CWNP CWAP-303 Official Study Guide