After nearly two decades of advancing Wi-Fi technology and the recent explosion in the number and usage of Wi-Fi enabled devices, planning a commercial Wi-Fi deployment inevitably means confronting a bewildering array of choices:

  • Which is the right technology to use?
  • What type of access points (APs) should I deploy?
  • How many access points will I need?
  • What is the optimal location for each access point?
  • Are there any sources of interference I need to account for?
  • How can I determine the optimal channel and power settings for each access point?
  • How should I manage the resulting Wi-Fi network?

To answer these questions for any but the most basic small office deployment is a non-trivial task that will almost certainly require a comprehensive site survey.

The Site Survey

Site surveys can take the following three basic forms and we would recommend that at least two of these are carried out for any large deployment:

  • Predictive survey
    This is performed using software tools such as the Ekahau Site survey and Planning Tool or the free ZyXEL Wireless Optimizer, in which detailed plans of the deployment site are constructed and then different WLAN configurations simulated to predict the optimal number and location of APs of your chosen brand and model. The value of such a survey will depend to a large degree on the quality of the information input. Greater precision, not only for the various room dimensions but also for the thickness and construction of the walls and ceilings that separate them, will increase the overall predictive accuracy.
  • Pre-deployment survey
    This is a physical survey performed on-site using one or more test APs, together with hardware or pc-based software tools, allowing you to test various AP placements and then, by walking through the building with the laptop or tablet, record and map the resulting signal strength at surrounding points. The resulting map correlating signal strength with a detailed plan of the site, is often referred to as a ‘heat map’. Another useful tool at this stage is a spectrum analyzer, which can help to identify potential sources of interference and measure their likely impact on the network. These tools (also available from vendors such as Ekahau) typically consist of a small USB device working in concert with pc-based software.
  • Post-deployment / Validation survey
    This is a survey performed after full installation of the WLAN, where actual coverage and signal strength is verified at all necessary locations within the building, typically using the same kind of pc-based software tools as in a pre-deployment survey. This type of survey can also be useful when planning an upgrade to an existing WLAN.

In cases where detailed building plans are available, and especially if already familiar with the construction and intended usage of the site, then a predictive survey may be sufficient to broadly estimate the size and scope of a new deployment.

However, in most cases, the greater predictive accuracy achieved through an on-site pre-deployment survey will more than repay the additional investment in time.

Additional information required

No matter which survey methods are chosen, in addition to obtaining detailed floor plans, the following questions will also need to be answered:

  • In which areas of the building is Wi-Fi coverage required / not required?
    For example, kitchens, stairwells and washrooms may not require coverage.
  • How will you supply power to the various access points deployed?
    Some APs can receive power, either from traditional mains adapters or via their Ethernet ports (see PoE – Power over Ethernet). Others, like the WAC6103D-I are PoE only.
  • Of what materials are the walls, partitions and floors constructed?
    The more comprehensive software tools allow you to select the material and thickness for each instance. See also: How much signal attenuation (loss) should I expect from walls and floors?
  • How many concurrent client (access device) connections (peak client device density) need to be supported in each coverage area and how fast might this number grow?
    Note, this may be several times the number of users depending on their usage of smart phones, tablets, and other Wi-Fi-connected devices such as printers and scanners.
  • What applications must these wireless connections carry, and how is this expected to to change over time?
    This is critical since bandwidth and latency demands vary enormously from those of basic email and web-browsing at one end, to real-time voice (VOIP) and video communications at the other.
  • What other electronic equipment that might cause interference will be in operation in and around the site?
    Pagers, hands-free wireless phone speakers, 2-way radios, wireless cameras, wireless motion detectors, and even microwave ovens can interfere with your Wi-Fi coverage, and while most of these may be revealed during your walk-through survey, it is always worth checking whether any other equipment will be in use at other times of the day or week. See - Which band to use?
  • What is the overall budget for the deployment?
    Although the last on our list, this is perhaps one of the first questions to be answered, since it impacts almost every other decision concerning technology and equipment. Ideally, for the sake of future-proofing, we would design all new networks to take advantage of the latest standards and highest possible performance available, but if this takes your client significantly over budget, then some level of compromise is inevitable.

Armed with the above information, the results of a pre-deployment survey, and some of the the aforementioned software tools, it should be possible to predict with a high degree of accuracy, how many of any given type of access point will be required and where they should be positioned for maximum coverage.

This however, still leaves the questions of which technology to use, what type of access points to deploy and how to manage the resulting network.

To fully answer these questions will ultimately depend on a combination of factors including your client’s budget and the pricing and availability of products from your chosen distributor, however the following may help to inform your ultimate decision: