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Why is a Wireless Site Survey needed?

Why is a Wireless Site Survey needed?

A Wireless Site Survey is recommended when implementing a wireless network. For larger wireless network deployments, a site survey is a must have item. For smaller wireless deployments, a site survey is good to have but sometimes the cost of the site survey becomes an issue. When deploying a wireless network, we are looking for the optimal wireless coverage and performance with the minimal use of equipment. This saves on time, man power and equipment cost. To get optimal wireless coverage and performance, we need to understand the Radio Frequency (RF) behavior of our wireless network deployment site. A wireless site survey will provide this information by revealing places of signal interferences, places where signals are weaker and areas of no signals (dead zones). A wireless survey also helps to avoid interference due to existing radio sources and interferences cause by physical structures such columns, beams, walls, and metal objects. In fact anything can affect the radio signal profile of a site including furniture and people. It is important to remember that the objective of a wireless site survey is to determine the feasibility of deploying a wireless network to meet your needs and to determine how to deploy a wireless network within the constraints of your site.

How does a Wireless Site Survey help?

When deploying a wireless network WiFi access points (APs) are often placed at random but is this add-hoc placement of WiFi APs a good strategy? In small deployments the add-hoc approach is not a problem but with medium to large deployments a wireless site survey is advised and often needed. A wireless site survey helps to determine where to place WiFi APs to avoid interference and avoid overlap coverage from other APs. In practice many network managers just randomly place WiFi APs and simply install extra WiFi APs when extra coverage is needed or when they get complaints about bad WiFi access. In an add-hoc wireless network the network manager has no idea what kind of interference exist and how the site’s radio signal profile changes. By getting a wireless site survey, it will help determine if there are co-channel interferences and how much, where external radio interferences are causing problems and how to minimize the number of WiFi APs needed and where to optimally place the WiFI APs for best coverage. It is important to understand that a wireless site survey is a snap-shot of the site’s radio signal profile at that time. As the site changes with new addition of people, cubicles, furniture, and electronic equipment, its radio signal profile changes and may require a new site survey.

What WiFi standards need to be covered in a site survey?

The most common WiFi standards in use include 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac. The 802.11b and 802.11g standards both use the 2.4GHz band and are the most common supported standards. The difference between the two standards is performance with 802.11b supporting 11Mbps and 802.11g supporting 54Mbps. The next important standard is 802.11n supporting both the 2.4GHz and 5GHz band and with increase performance of up to 600Mbps. The newest standard is 802.11ac supporting the 5GHz band and with increase performance of up to 7Gbps. It is important to note that many new low cost personal computers (PCs) and tablets do not support 802.11n or 802.11ac standard. Many companies may have a wide range of WiFi devices and need to support many generations of WiFi devices from 802.11a through 802.11ac and beyond. A site survey needs to cover all WiFi standards used. Do not assume a site survey for one standard is valid for another.

What are the different types of Wireless Site Surveys used for site surveys?

There are basically three types of wireless site surveys passive, active, and predictive.

A passive site survey tool listens to existing access points and other signal sources for signal strength, interference, and access point (AP) coverage. In a passive site surveys, the listening WiFi adapters does not need to associate to the AP, it just passively listen to give a picture of the Radio Frequency (RF) characteristics of wireless network site. Passive surveys are often perform when upgrading existing wireless networks such as adding additional APs.

In an active site survey, the survey WiFi adapter is associated to the AP(s). This allows gathering of detailed information such as network traffic, throughput packet loss, and data rates. An active site survey is often performed in conjunction with a passive site survey at start of a new wireless network deployment.

A predictive site survey is performed without any type of field measurements. It uses RF planning software tools that can predict wireless coverage of the APs. To perform this site survey, a floor-plan drawing (AutoCAD, JPEG, PDF) is a must-have. Predictive site surveys are used when the site or building is not yet built and are helpful for budgeting purposes.

The goal of all of wireless site surveys is to provide detailed information that addresses the site's radio frequency coverage. Before implementing or attempting to optimize a wireless network, you'll want to understand all the possible areas of interference, AP placements, power considerations, and wiring requirements that are needed. A wireless site survey can provide all of this information and more, so you have the tools you need to design, implement, and optimize your wireless network.

Some Wireless Site Survey tools?

AIRMAGNET - Part of Fluke Networks




METAGEEK - Diagnose and Plan Combo package)

METAGEEK – inSSIDer 4 and inSSIDer Office w/ Wi-Spy Mini


Some free Wireless Site Survey tools?

Heatmapper - is a free software from Ekahau, makers of the Ekahau Site Survey.

  • Wi-Fi coverage on a map
  • Locate access points
  • Supports 2.4 and 5 GHz 802.11n
  • Detects security settings
  • Quickly locate Rogue Access Points
  • This product has a 15 minute survey limit (encourages user to buy Ekahau Site Survey product)

Kismet - is a free and open Wi-Fi stumbler, packet sniffer, and intrusion detection system for Windows, Mac OS X, Linux, and BSD. Kismet is an 802.11 layer2 wireless network detector, sniffer, and intrusion detection system. Kismet will work with any wireless card which supports raw monitoring (rfmon) mode, and (with appropriate hardware) can sniff 802.11b, 802.11a, 802.11g, and 802.11n traffic. Kismet identifies networks by passively collecting packets and detecting standard named networks, detecting (and given time, decloaking) hidden networks, and inferring the presence of nonbeaconing networks via data traffic.

NetSurveyor is a free basic tool developed by Nuts About Nets.

  • NetSurveyor 802.11 Network Discovery Tool - Free
  • WifiExplorer (Android Platform Network Discovery) - Free
  • Netstress Network Benchmarking Tool - Free
  • Touchstone (RF Spectrum Analyzer) - Free

KisMAC - If you're a Mac user, you might consider using the KisMAC stumbler and security tool, similar to Kismet. It also reveals "hidden" SSIDs. Along with the other basic details, it can show the access point's clients (with MAC Addresses, IP addresses and signal strengths). Plus it reports the noise levels and gives you the signal-to-noise (SNR) values. It also supports GPS and mapping, and PC access point import and export. It even includes tools to attack Wi-Fi networks for penetration testing.

Xirrus Wi-Fi Inspector - powerful tools for your Wi-Fi network.

  • Wi-Fi Inspector - Free
  • Wi-Fi Design Cloud - Cloud based tool, Free to try
  • Wi-Fi Designer - Free to demo

Vistumbler - is newer open source stumbler first released in 2007 and updated as lately as 2010. It displays the basic access point details, including the exact authentication and encryption methods, and can even speak the SSID and RSSI of access points. Similar to NetStumbler, you can view a list of all access points or drill down to those categorized by authentication, encryption, channel, network type, and SSID. You can also view graphs of the access point signals in addition to viewing text readouts. It's highly customizable and offers flexible configuration options. For example, you can define and save access point names to better distinguish them in the future. In addition to basic GPS support to record access point locations, it supports live tracking within the application using Google Earth. However unlike NetStumbler, Vistumbler only gives you the signal levels and doesn't include the noise levels. Thus it doesn't report the signal-noise-ratio (SNR) values, which is usually more helpful than just the plain signal levels

NetStumbler - is one of the oldest and most known Wi-Fi stumblers and runs on Windows XP and Windows CE/Mobile. It lists nearby access points and displays their basic details: SSID, channel, speed, MAC address, vendor, and encryption. Unlike most other stumblers, it also shows the signal, noise, and signal-to-noise ratio (SNR) levels. Additionally, it has GPS support to record access point locations when wardriving. It is important to note that NetStumbler hasn't been updated since around 2005. It may not run well on Windows Vista or 7, or even 64-bit Windows XP.