Benefits of a Wireless Survey

Surprisingly, We’ve recently spoken to a number of other resellers who do not carry out onsite wireless surveys.. This is asking for trouble!

All too often we speak to end users who are experiencing issues with their wireless network, the mojority of the time when we investigate the route cause it stems back to the very beginning of the planning stages, where an IT reseller did not conduct a wireless survey onsite.

Why get a site survey?

Site surveys determine signal coverage, throughput requirements, interfering sources, dead spots, potential roaming behavior, etc. and helps determine:

  • How many access points are needed for the best wireless coverage
  • Where to deploy access points
  • How to configure each access point to ensure optimal coverage for all end users

Without site surveys it is difficult to determine the capital investment needed to deploy the wireless network in a timely and cost efficient manner.

Site surveys are performed using professional grade tool kits such as AirMagnet Survey Pro. Without the use of a professional site survey tool, it is virtually impossible to plan and implement a robust and reliable wireless system that extends beyond two or three AP’s in a small single floor area. The purpose of these surveys in regards to channel planning should be to ensure adequate coverage without causing additional channel utilization or interference.

Some other considerations when surveying the network:

  • It is important to note that 2.4GHz and 5GHz have different characteristics that must be taken into account when deploying dual-band AP’s (2.4GHz and 5GHz capable) access points. The 2.4GHz signal can travel further and has better penetration capabilities than 5GHz. Thus the radius of a coverage cell on 2.4GHz is longer than on 5GHz. This could lead to dead zones in 5GHz coverage if only 2.4GHz coverage is measured in a site survey, and will likely require different power settings for each radio to equalize coverage cells.
  • In some deployments, multiple SSID’s are enabled on an a single AP. Some SSID’s may have legacy bit rates disabled which shortens the coverage radius on 2.4GHz or the SSID may only have 5GHz enabled. The site survey should measure the coverage cells of each SSID independently within the extended service set to determine if adequate coverage is met.
  • For high-density deployments, manually tune 2.4 & 5.4GHz channels and power settings based off of site survey data.

Channel Planning

There are 14 channels designated on the 2.4 GHz spectrum which are 20 MHz wide. The channel centers are separated by 5 MHz, and the entire spectrum is only 100 MHz wide total. This means that the channels have to squeeze into the 100 MHz available, and in the end, overlap.

However, there are three channels that don’t overlap: 1, 6 and 11, as you can see in the image below. Co-channel interference is where devices take turns talking, so the more devices on one channel, the longer it takes for a device to talk since it has to wait for its turn.

WiFi WLAN Channel Planning wireless survey

Using overlapping channels causes errors, which results in packet re-transmissions and significantly decreased network performance.

The same problem exists when using more than one access point on the same channel in the same physical area.  This is called co-channel interference.  Co-channel interference should be avoided as it can have a dramatic effect on network performance

Main causes of WiFi interference:

Wireless interference

Co-Channel interference isn’t a major problem until there are too many WiFi devices on the same channel. Adjacent-Channel interference on the other hand is where you run into problems and channel selection becomes critical. Luckily, these channel related interference’s can be reduced or eliminated by selecting the proper WiFi channel for your network.

Using a spectrum analyzer like AirMagnet Spectrum XT will allow you to see this wireless environment, so you can either select the right channel or mitigate WiFi interference. Ultimately, improving your WLAN network performance.

RF signals are very unpredictable. If an access point is placed in an open environment without obstacles, the signals usually maintain an omni-directional pattern. However, when obstacles and walls are introduced, the RF signals are disrupted and access point coverage varies based on location.

It is important not to generalise every wireless deployment in terms of requirements. For example, in an office environment where file and print services and Internet access are the primary needs, a few dead spots may be tolerable. But in a healthcare environment where medical personnel require unrestricted wireless access to patient information this is unacceptable.

Without a wireless survey it would be virtually impossible to determine if the technical requirements of the business can be supported!

What will Iris Networks do onsite?

Gather requirements — An initial planning session will be held to review preliminary design requirements, confirm your objectives and goals for assessment. We will also identify and confirm the in-scope and out-of-scope areas for design, in-scope areas that have AP mounting restrictions and review floor plans to bring attention to any potential trouble areas

Perform the survey — Indoor & outdoor surveys, active surveys enabling real-world measurements, spectrum analysis and Voice over Wi-Fi (VoFi) surveys if needed

Deliver the results — Comprehensive and easy-to-understand report with a bill of materials for complete installation

What does the site assessment include?
The site assessment includes:

    • Network verification and validation per specifications. Expert recommendation and advice provided in order to achieve desired specifications
    • Spectrum Analysis to identify RF interference sources from non-WLAN sources in a single survey
      • Visualization of RF energy at any location and identification and display of non-802.11 devices interfering with WLAN
    • Voice over WiFi (VoFi) survey. Coverage maps built specifically for voice networks includes call quality, phone roaming zones (roaming stats), channel utilization and voice-readiness validation

We can provide this for a range of:

New installations — Determine capital investment and obtain the number and preferred location of access points for the best coverage before the initial deployment

Existing installations — Verify the number of access points required versus the number actually deployed and validate their location to ensure optimal performance for all end users

Ongoing optimisation — Ensure optimal performance by conducting periodic site surveys in order to account for changes in the WLAN environment

Iris Networks site assessment service uses software and industry best practices to locate and map authorised and unauthorised wireless access points, review any corporate access point deployment, analyze the environment for interference and design and plan a WLAN network.

If you are a reseller, distributor or a systems integrator that needs an experienced partner to deliver wireless projects on your behalf, whether it be for small or large scale customers contact us to discuss your requirements.

NetAlly- AirMagnet Survey Pro
NetAlly – AirMagnet Spectrum XT
NetAlly – AirMagnet WiFi Analyzer
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