Pseudorandom Thoughts on WLAN Terminology

Pseudorandom Thoughts on WLAN Terminology

What? Oh, That…

There’s been a some debate lately in the WLAN community about the way different terms are used, and whether or not they are being used correctly. I wanted to add my thoughts to the conversation. If you haven’t noticed it all, you can check out the links below (in chronological order) to catch up.

I have a tendency to be a bit of a Grammarsaurus Rex. We all have terms and phrases that we use among family and close friends that mean a specific thing to that group, but something completely different to anyone outside said group. I have found this with my wife on many occasions; she will use a term that her family uses for one thing, but mine defines differently. A common example of this is the word “dinner“. Another is when she asks me how I like my new Mac PC… I have a canned response when she says “Well, you knew what I meant”. It goes along the lines of, “Yes, but nobody else would.”

Which brings me to my point: words have specific meanings that cannot be changed on the whim of Joe Marketer, or Betty Engineer, or Ivan Salesmanovich. As Glenn said in his Ten Talk, we as a community, nay industry, must agree on standardization of terminology. I’ve outlined my thoughts below. I’m going to start with the definitions of the words survey, design, and plan, as I believe they apply to the process of deploying a wireless LAN (definitions from dictionary.com).

survey (verb) – to view in detail, especially to inspect, examine, or appraise formally or officially in order to ascertain condition, value, etc.

survey (noun) – a formal or official examination of the particulars of something, made in order to ascertain condition, character, etc.

design (verb) – to prepare the preliminary sketch or the plans for (a work to be executed), especially to plan the form and structure of (the object).

design (noun) – an outline, sketch, or plan, as of the form and structure of a work of art, an edifice, or a machine to be executed or constructed.

plan (verb) – to arrange a method or scheme beforehand for (any work, enterprise, or proceeding)

plan (noun) – a scheme or method of acting, doing, proceeding, making, etc., developed in advance

 

Survey

I’m going to start with “survey”, because I think this is the term that is misused the most. To survey something means to view or observe something to determine certain conditions or characteristics. In the wireless world, there are a couple requirements to be met in order for something to be called a survey:

  1. You must be on-site – I come from a two-way radio and WISP background, where the first step of EVERY project was to get on site and familiarize yourself and your crew with the location, possible hazards, cable routes, power availability, and other site-specific characteristics. For Wi-Fi, you must confirm the floor plan is accurate, and determine what type of mounts will be required for the access points, among many other things.
  2. You must be gathering data or measuring something – Whether it be taking pictures, measuring attenuation, locating switch closets or server rooms, validating an install, looking for potential cable routes, or something else, you are recording specific information about the project.

I’m on the fence when it comes to gathering customer requirements – part of a survey, or in it’s own category, perhaps an interview?

 

Plan

In long-distance microwave networks, the process of determining tower location, antenna height, link distance, channel selection and size, etc, is typically referred to as “network planning”. I once interviewed for a job doing just that, of which the title was “Network Planner”. This terminology business really should be a simple thing… According to the definition above, the term “plan” is something we do before going about a task. In that spirit, should WLAN planning encompass the requirements gathering, pre-deployment survey and initial predictive design? IE, is everything we do before deployment part of planning the wireless network? What about after, is it part of the bigger design life cycle?

 

Design

The term “design” has been used interchangeably with “survey” in the past. This must stop! We don’t do predictive surveys! We do predictive designs (or maybe models), based on the data gathered from a site survey. When a structural engineer designs a bridge, they do calculations based on data gathered from the potential site and the materials they will use. Do they call the results of those calculations a survey? NO! They call it a design! What comes to mind when someone says, “I saw some people outside surveying a road”? Do you think, oh, they were sitting on a park bench with laptops, designing a highway? I’d bet not. More likely, you associate surveying with the fine art of walking around with a pointy stick, using a transit to gather data about land or construction projects.

Based on the definitions above, maybe the terms “design” and “plan” can be used to mean the same thing?

The wireless LAN design (noun) is the all-encompassing life cycle consisting of many things, such as:

  • access point placement including height
  • access point and/or external antenna orientation
  • channel plan
  • transmit power levels
  • mandatory/supported data rates
  • SSIDs to be used
  • Security methods to be implemented
  • VLANs
  • IP addressing schemes
  • cable routes

The WLAN design (verb) is also an iterative process, in which there are some key steps:

  1. Gather customer requirements (interview?)
  2. Gather site data (pre-deployment site survey?)
  3. Implement data into planning software (predictive design?)
  4. Deploy network (deploy network?)
  5. Confirm network performance (validation survey?)

 

Clear as Mud

I’ll try to sum up my thoughts for how each term should be used. I think I asked myself more questions than I answered while drafting this post.

  • To call something a survey, it must be performed on-site and it must result in some new information or data about the project.
  • Surveys are a part (oft-repeated) of the iterative WLAN design process
  • There are different types of surveys:
    • pre-deployment – gathering site data such as wall attenuation values, ceiling heights, confirming floor plans,
    • post-deployment or validation – confirming the network design has met requirements such as primary and secondary coverage, and co-channel interference,
    • investigating user complaints or issues where improper channel planning or power levels may be suspected (not to be confused with packet captures! Site surveys are a Layer 1 thing. You might get to packet captures while troubleshooting),
  • A predictive design IS NEVER A SURVEY! But, a good design requires data gathered during a survey.
  • Planning vs. Design – do we need to use both terms? I think no, we don’t. They are basically synonyms, so should we pick one or just let it go?

So, “survey” is a term with a distinct meaning from “design” and “plan”, and it should be used correctly. One last time: a survey is NOT a design!

As for “design” and “plan”, well, maybe they can be used as if they are the same? I feel less strongly about these two.

Thanks for reading, please add your input by commenting!

 

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  • François Vergès

    Like always, great post Steve!

    I totally agree with you for the use of the term “survey” i.e. you have to be on-site gathering/measuring some data. I also totally agree for the misuse of the term “predictive survey” (I think it comes from the fact that we use the same tool to perform the predictive design and the actual on-site survey).
    Hopefully we will all end up using the same terms!

    What about the misuse of CCI 😉 ?

    • Thank you Francois! Good point, using the same tool for surveys and designs probably led to that confusion.

      I think the CCI/CCC debate has stronger advocates than I…

      • François Vergès

        Check out this post by George: http://community.arubanetworks.com/t5/Technology-Blog/Definition-of-WiFi-Interference-and-Contention/ba-p/223976

        I like how he explains the difference between CCI and CCC.

        • Yep, he explains it well.

          • Matthew Bonadies

            I think the same discussion can be had for the term “channel” and “interference”. When the FCC was allocating the 2.4 Ghz ISM band, they didn’t take into account that 802.11 would use 20 Mhz wide “channels”. If this was the case, the all 11 channels wouldn’t overlap. Instead, they listed 11 “center frequencies” that were allowed and called them channels. Oops, semantics issue here causing confusion. It was IEEE that decided on the 20 Mhz bandwidth. CCI could really be understood as “Adjacent Frequency Interference” and is essentially the same thing.

            Interference could be understood as some unintentional or intentional “thing” causing an undesired result. In our case it is 802.11 radios talking to each other. If the RF gets messed up somehow then that causes a whole bunch of issues, mainly slow speeds to the end user. Good discussions!

          • Steve

            Some people use the terms Co-Channel Contention, Co-Channel Congestion or Co-Channel Cooperation instead of Co-Channel Interference to describe what happens when two or more APs are using the same channel; this is because they can decode preamble, NAV timer, etc, and defer per the standard. APs on adjacent channels, such as 6 and 7, cannot decode and defer correctly, so this becomes more of an interference issue than a clear-channel assessment issue.

            There is a basic difference between anything co-channel and adjacent channel. Co-channel indicates devices on the same channel (6 and 6). Adjacent indicates NOT the same channel. Although there have also been discussions regarding adjacent overlapping (6 and 7) versus adjacent non-overlapping (6 and 11).

            I like to think of interference as something that is going to trigger energy-detect and cause a backoff in a transmitter, or something that raises the noise floor at a receiver too high for successful demodulation, and may or may not be an 802.11 signal. I think of 802.11 signals on the same channel not as interference, but as congestion.