Wireless Range in Data Networking Applications

When designing cellular or Wi-Fi networks, a question often gets asked is the effective range of a device from the wireless network transmitter. However, as with many aspects of wireless networking, the answer is not straightforward and depends on various factors.

In this blog post, we will explore the key parameters that determine the range in a wireless communication system, using Wi-Fi as an example for clarity, and provide the equation for determining the range. We'll also delve into the connection between the client device and the infrastructure, highlighting the importance of designing both ends of the communication path.

In any wireless communication system, the range between a transmitter and receiver is determined by several parameters:

• Transmit Output Power of transmitter and receiver
• Receiver Sensitivity of transmitter and receiver
• Antenna Gain of transmitter and receiver
• Antenna Cable Length/Type and Antenna Connectors at the transmitter and receiver
• Frequency in use

This means that the client side of the equation has just as much impact as the infrastructure side and needs to be considered when designing the wireless network. Each side of the connection possesses its own range, which must intersect properly for communication to succeed.

In the following image, the client device is within the range of the access point, but the access point is not within the range of the client:

In this case, the client can "see" the access point, but the access point cannot "see" the client, meaning that data transmitted to the client from the access point is received, but data sent back to the access point from the client is lost in transit. Since different client devices have different antennas, transmit output power, and receive sensitivity, the answer of what the range may be will differ for each client device.

This illustrates the need for designing both ends of the communications path to achieve data transmission objectives.

To determine range, an equation is used that considers both the transmission and receive sides of the communication path.

The equation used is as follows:

The following is an explanation of the components of the equation:

• PTX = Transmitter Output Power
• GTX = Transmitter Antenna Gain
• LTX = Transmitter Losses in antenna cables and connectors
• LFS = Free Space Path Loss, which is the degradation of signal over distance
• LM = Miscellaneous Losses (Fade Margin, Body Loss, etc.)
• GRX = Receiver Antenna Gain
• LRX = Receiver Losses in antenna cables and connectors
• d = Calculated distance from the transmitter

This equation illustrates how changes in any of the components can impact the available range of the wireless system.

In an existing system, some things can be done to improve the range of the communications system, such as using a more focused antenna at either end of the system. Additionally, using less antenna cable length or upgrading to a better quality cable can improve the connection by reducing the signal loss over cable length. Removing obstructions can also yield significant performance improvements.

While the equation is a good baseline for determining range, other factors must be considered. For example, since the physical environment - specifically any structural or natural obstructions, interference, RF reflection, and refraction - also impacts communication, the equation is used mainly to guide design efforts. In order to gain a thorough understanding of how to design the RF aspect of wireless communication, an onsite RF survey is required.

USAT offers onsite RF Survey services to provide designs for any cellular or Wi-Fi network infrastructure.