Environmental Requirements

There are several factors that are critical to deploying a successful wireless network. System Transmission Requirements, RF Line of Sight and RF Operating Environment will determine what hardware is used and the mounting location of each device.

  • Line of sight- A common misconception is a visual line of sight is the same as radio frequency line of sight; it is not. Radio Frequencies travel in an ellipsoid shaped area between the Access Point (AP) and the Client(s). This ellipsoid shape is called the Fresnel Zone, shown in the diagram below. As the distance (d) between AP and Client increases the radius (r) at the mid-point also increases and so the antenna need to be placed at a height greater than r above any obstruction. You will need to make sure your Fresnel zone is clear of any obstructions between the AP and the Client(s), as with only 20% obstruction, you start seeing signal loss. A good rule of thumb is not to exceed 40% obstruction as you will start to see significant signal loss above this figure. These obstructions can range from buildings, trees and even the the earth. It is also worth noting that water absorbs radio waves so while a tree may be a minimal obstruction, the water on the leaves will absorb the radio waves and have a big impact on signal quality if in the Fresnel zone.
  • RF Environment – It is important to understand the RF Environment you are going to install your wireless products in. Other Access Points, Cell Towers, and further wireless devices can create a noisy RF environment that can cause interference to your signal. The Netwave wireless products default channel width is 20/40MHz. The AP will determine automatically how much interference there is and auto rate to either 20 or 40MHz. You may want to override the default setting and select a desired channel width. More information is detailed below. It is also essential to have the proper antenna for your deployment. Antenna with wide beamwidths are ideal for Point-to-MultiPoint deployments but they will pick up more interference than narrow beam antenna. Narrow beamwidth antennas are good for Point-to-Point, long distance and scenarios where you want to avoid the noise and interference.
  • Ethernet Cable length - while determining where to mount the wireless device, it is necessary to approximate the CAT5/6 cable run from the wireless unit to the Power Injection Module (PIM) then to the network. The total length should not exceed 90m. If the cable run exceeds 90m, please contact Comnet Technical Support and we will design a solution for you.