is preferred for video streaming. If the signal drops to -80 dBm or lower, it is too weak for most applications and may prevent connecting altogether. Table 3 shows the service quality for various signal strengths.
Interference is a primary cause of Wi-Fi performance issues. Adjacent channel interference happens when wireless APs use overlapping channels, causing them to talk over each other. This occurs within the 2.4 GHz band where channels overlap, which is why APs should be configured to use non-overlapping channels 1, 6, and 11. Co-channel interference can happen in the 2.4, 5, and 6 GHz bands and when two or more APs near one another use the same channel. High transmit power can increase the risk of co-channel interference by expanding the coverage area and the potential for overlap. Lowering transmit power or increasing the distance between APs on the same channel can help prevent overlapping coverage areas. While the non-overlapping nature of 5 GHz and 6 GHz channels enables bonding multiple smaller 20 MHz channels into wider 40 MHz, 80 MHz, or 160 MHz channels for improved throughput, using wider channels also increases the risk of overlapping channels that lead to co-channel interference. For example, an AP operating on the 80 MHz wide channel 42 (i.e., channels 36, 40, 44, and 48) can experience interference with another AP operating on the 40 MHz wide channel 38 (i.e., channels 36 and 40). Carefully configuring a mix of channel widths in the same environment is essential to avoiding co-channel interference in these bands. Wi-Fi interference can also occur due to other nearby wireless signals and electromagnetic radiation from external sources operating at the same frequency, leading to slower network speeds and connection delays. Interference from other sources typically impacts the 2.4 GHz band, since microwave ovens, cordless phones, Bluetooth devices, and even some lighting can emit noise at this frequency. Poor Wi-Fi signal strength, measured in decibel milliwatts (dBm) and expressed as a negative value, can also cause performance issues. A higher dBm value (closer to zero) indicates a stronger signal, which correlates with higher data transfer speeds and more reliable connections. A signal strength of -67 dBm or better generally supports most applications like voice and email, while a signal strength of -50 dBm or better
TABLE 3: Wi-Fi signal strength quality (Source: Fluke Corporation)
Factors that can lead to poor signal strength include:
• Excessive distance from an AP, such as in high-ceiling environments where APs are mounted too high. APs may need to be mounted lower using threaded rod or cable hanging kits to improve signal strength. Horizontal AP orientation is also recommended for stronger signals. • Obstructed line of sight and physical obstacles can degrade signal strength. While the 2.4 GHz band is more congested and prone to interference, it offers better range and propagation (i.e., the ability to penetrate building materials) due to lower signal path loss. The 5 GHz and 6 GHz bands are more susceptible to signal weakening by walls, doors, and furniture, especially dense materials like concrete and metal. Conducting a Wi-Fi site survey before deployment can help determine optimal AP placement in a facility. If signal strength is a problem after deployment, the environment may have changed, or there may be an interference issue.
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January/February/March 2025
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