How To: Conduct A Wireless Site Survey?

In wireless systems, it is very difficult to predict the propagation of radio waves and detect the presence of interfering signals without using test equipment. Even if the system implements an omnidirectional antenna, radio waves do not actually travel the same distance in all directions. Instead, ramparts, doors, elevator shafts, people and other obstacles provide varying degrees of attenuation, and RF (radiofrequency) radiation patterns become irregular and unpredictable. Therefore, before installing an access point, you must conduct a wireless site survey (also known as an RF site survey) to fully understand the operation of radio waves in your operating environment.

Site Survey Concept

The ultimate goal of a wireless site survey is to regulate the number and location of admission points (or mesh nodes) that provide adequate signal coverage in a facility or city. For most implementations, "good coverage" means admitting data transmission speed or lower performance. For a survey to be successful, the required performance must be related to the values ​​measured by a survey tool such as SNR. Surveys of wireless sites also detect the presence of RF interference from other sources that can degrade the performance of the wireless LAN.

The need and complexity of a wireless site survey will vary from one facility to another. For example, a small three-bedroom office may not require a site survey. In this scenario, a single Wi-Fi access point (or router) somewhere in the office is probably sufficient but still maintains sufficient coverage. If the access point finds RF interference from another nearby WLAN, you can select a different channel to eliminate the problem.

Large facilities, such as offices, airports, hospitals, warehouses or outdoor areas, such as cities, generally require extensive sites of wireless survey. Without research, users will likely have poor coverage and performance will degrade in some areas.

When Conducting A Wireless Site Survey, Consider The Following:

1. Understand The Wireless Requirements. Determining the best location for an access point or mesh node requires in-depth knowledge of the specific requirements of your network that will affect signal coverage. For example, the maximum range between a client device and an access point decreases as data speeds and resulting performance increase. Therefore, to correctly interpret the results, you must know your target data rate (and performance). In addition, the transmission power of the customer's device can be relatively low and must be taken into account when using most site inspection tools. Identify the technologies that your network implements, such as 802.11g and 802.11n, and conduct your research taking these technologies into account.

2. Acquire The Installation Map. Before going too far with the site survey, find a set of construction plans or city maps. If none are available, prepare a drawing that shows the location of walls, hallways, etc. The wireless site survey tool imports diagrams in various image formats. Of course, the mapping software is suitable for outdoor city surveys. If all else fails during a survey in the building, consider taking digital photographs of fire evacuation maps, usually on the corridor walls.

3. Visually Inspect The Facilities. Before testing to verify the accuracy of the installation diagram, examine the installation in detail. This is a good opportunity to know the possible attenuation barriers that can affect the propagation of the RF signal. For example, visual inspection reveals damage to the signal of elements that are not normally visible in planes, such as metal racks and partitions. Also, consider the places where access points can be mounted, such as on tiles or columns. In urban outdoor environments, the location and availability of street lighting and water towers for the assembly of mesh nodes and recoil equipment should be carefully evaluated. These actions will make your subsequent tests work better.

4. Evaluate Your Existing Network Infrastructure. Determine the capacity of an existing wired network that can interact with access points or mesh nodes. Most buildings have Ethernet and sometimes even fiber-optic networks. Determine how much of your existing network can be used to support your wireless network site survey.