Wireless Design Requirements
Wireless has become an expected service. We expect it to work reliably all the time. With mobile vendors imposing strict data maximums, everyone’s first choice is to hop on the strongest wireless signal.
Cisco has recently forecasted Wi-Fi and mobile devices to account for 53% of IP traffic. Research conducted by Mobidia indicates users of iPhones consumed 8.9GB of Wi-Fi data every month in Q3 of 2014.
These numbers show how much we’ve transitioned from wired to wireless. And what I’m alluding to is how we, as wireless engineers, need to design better, more resilient, wireless networks.
How do we do that? First step to any design or implementation is gathering requirements. Yes that means talking to end users and clients. But stay with me here. I will outline as much information as I can.
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Ask and Listen
This is the part where you shut up and take notes. Listening is absolutely key here. You should be prepared with a list of questions.
The purpose of gathering wireless design requirements is to get an idea of how the end user expects to use wireless.
What applications are going to be used? Aside from the common – web browsing, Outlook, file storage.. what you’re trying to find out is if there are any applications that may be sensitive to latency.
Maybe the application is a bandwidth hog. You may need to probe with more questions.
Take a test application, for students, as an example. Each student needed to download a 15 MB file during an exam. There were about 40-60 students and one access point nearby.
Not to mention, other students in the area that could be associating to that access point. A single access point may not be able to fulfill the wireless requirements for this scenario.
The takeaway here: learn how people plan to use the wireless network.
What types of devices will associate to wireless? You can assume the obvious – iPhones, iPads, Surface Pros, Lenovos, MacBooks, etc.
Maybe the end user plans on using scan guns running on legacy radios? Didn’t see that coming!
Find out now before opening day when people are in a frantic scramble to find out why your wireless network “doesn’t work”.
You may need to support wireless voice. That comes with supporting roaming and possibly an increased amount of access points.
It’s perfectly acceptable to hear that the end user may not know what kind of devices will be used. You can get an idea based on the first question, what applications are going to be used?
Takeaway: Learn which devices may need to be on wireless. This becomes important if you need to support legacy radios. There may be other reasons as well which may determine specific hardware recommendations such as external antennas.
What areas need coverage? This used to be the only way we would design a wireless network. If the area was covered by an access point then you were golden. But things have changed.
Wireless is heavily relied upon. People expect wireless to work without a hitch. But now we need to take capacity into consideration.
The end user usually knows which areas need to be covered. What they won’t tell you is how many people will be crammed into said covered areas.
How many clients? Sometimes I rephrase this for the end user and ask how many people would they expect to have in the building. And based on that number I multiply that by 2 or 3.
I assume each person has a laptop, a phone, and maybe a tablet. Each of which they all want wireless on.
Takeaway: Don’t solely rely on coverage. Plan for capacity as well. Sometimes using all omni-directional antennas will fail you. In a high density environment, you may want to use semi-directional patch antennas to create smaller cell sizes.
How many floors are in the building? You’ll want to consider the bleed from access points above and below. Not only just your access points but access points from other tenants. This will tie in with access point placement, which I cover below.
What type of building materials are you dealing with? The strength of a wireless signal diminishes quickly after going through objects. Are all the walls built with drywall, brick, thick glass, concrete, etc? Where are the elevators?
Maybe you’re dealing with an old building made of all brick or concrete. This affects the design of the wireless network which could also blow through the budget.
Takeaway: Do a walkthrough of the environment and take note of any obstructions that could potentially weaken your wireless signal. Mark them on the floor plan.
Where can access points be installed? Most access points are butt ugly. The end users hate looking at them.
Most of them want them tucked away in closets, metal cabinets and above ceiling tiles right next to the HVAC unit.
Be sure to ask the end user if exposing the access points cause any issues to aesthetics. If the end user objects to having access points out in the open, explain to them the downsides of placing access points in less desirable locations.
Explain it to them in a way they would understand – wireless signal would be weaker, download speeds may be slower, application experience will be less than optimal. This all results in loss of productivity and a waste of money on hardware purchases and installation costs.
Takeaway: Access points are an eyesore so be prepared to hide them.
When is the peak usage time and where would it occur? You’ll want to be sure you’ve provided enough coverage and capacity in times during peak usage. An example would be a large conference room. Think of the Cisco Live conference floor.
At Cisco Live 2014, at least 918 access points were used. Be prepared for the amount of users and the dramatic increase in traffic.
What is the growth rate? How many more users are expected to join the wireless network in the near future. Incorporate this growth into the design. Part of requirements gathering is also ensuring you can build for the future growth of the environment.
Then there are requirements to gather that the end user may not know.
Where are the nearest cable drops? Where are the closets located? Are they within 100 meters? Verify that cabling will be able to reach potential access point locations. New cabling will need to be pulled to these locations.
Considering Ethernet cables. With adoption for 802.11ac, would you possibly consider two Ethernet cables for newer access points? This is primarily future proofing.
Imagine if the access points were truly pushing over 1Gbps traffic. We’re obviously not there yet but just a consideration.
Will the switches support PoE? Can they provide 30 watts of power to an access point? Do the switches support 802.3at (PoE+). If existing switches are in place, you may want to have PoE capabilities verified.
Upgrading access points or installing new access points may require an upgrade to the infrastructure as well.
If the switches are not PoE, the access points can be powered by a midspan or power brick.
Takeaway: Due diligence will need to be performed on the wired infrastructure and ensure you have the right amount of power budgeted.
The requirements gathering phase is the most important phase. If you skip this phase be prepared to hear back from end users about their terrible wireless experiences. While a lot of information was given above, keep in mind that this is not a conclusive list. Every environment is different and the important thing here is to consider as many options as possible.
Listen to the end user’s needs carefully. Educate the end user on the wireless implementation process. Explain why you’re gathering information. Provide a very high-level overview on wireless being a half-duplex shared medium.
Gathering requirements should be a two-way conversation. The more information you can gather the better your wireless design can be.
Leave a comment below to include more requirements that should be considered in this phase.