Site Considerations

A wireless site survey is an essential part of designing and implementing a wireless network. Its purpose is to identify obstacles or sources of interference that could negatively impact WLAN performance. Based on the survey results and business requirements, the vendor strategically places access points to ensure adequate Wi-Fi coverage, meet POS bandwidth needs, support roaming, and maintain quality of service. Failure to conduct a wireless site survey may lead to poor network performance.

All surveys are performed by the vendor to achieve the best outcome for the enterprise. The vendor considers various factors when designing and implementing the wireless network, using different techniques and software depending on their approach. An initial survey should be conducted in an empty environment as part of the evaluation process and before installing any wireless hardware. The survey should then be repeated under real-life conditions, when environmental interference and Wi-Fi demand are at their peak.

Important:

All mobile and electronic devices connected to the wireless network affect its performance. Therefore, conducting performance tests during peak demand is essential to accurately assess network limits and capabilities. Survey results from an empty property cannot serve as a performance benchmark and should not be compared to results from surveys conducted in a fully occupied environment.

Access Point (AP) Position

APs should always be installed based on the results of a comprehensive site survey and never placed randomly. Incorrect positioning can negatively affect signal coverage and result in poor network performance. The number of APs required should be determined by the unique factors of each property, not by estimation or standard templates.

Several factors should be considered when designing a wireless network, including:
  • Wireless network purposes to be supported, such as POS, voice, video, and CCTV
  • Wireless network capacity and demand
  • Bandwidth requirements for applications such as VOIP, video calling, and security cameras
  • Number of SSIDs needed for the wireless network
  • The estimated number of concurrent connections per AP, as some APs may experience performance degradation with as few as 20 connected devices
  • Maximum allowed connections per radio on each AP
  • Heavy wireless demand environments, such as areas with high customer usage or extensive VOIP activity
  • Overlapping factors that may compound network challenges
  • Proximity of APs, as APs placed too closely can interfere with each other
  • Neighboring APs, which can cause interference and channel overlap
  • Maximum power output of APs

Note:

Outdoor APs must cover a large area to be effective. Some vendors offer models specifically designed for outdoor environments, providing optimal coverage for business needs.

Wi-Fi Interference

Wi-Fi interference refers to unintended signals emitted from sources other than the WLAN infrastructure. Such interference can impair the normal functioning of the WLAN and should always be identified and mitigated. Interference is a common occurrence in wireless networks, and in some cases, it cannot be completely avoided. It can reduce network performance and availability, as wireless signals may be intercepted, blocked, or disrupted by various factors—potentially preventing devices from connecting efficiently to the network.

Interference from Non-Wi-Fi Devices

Some non-network devices, such as microwave ovens, cordless phones, and wireless CCTV installations, can interfere with wireless channels. These devices most commonly operate on the 2.4 GHz frequency band.

Co-channel Interference

Co-channel interference refers to the total amount of competing in-band signals that prevent APs from receiving the intended signal clearly. When many client devices are located close together on adjacent or overlapping channels, interference levels increase, negatively affecting overall WLAN performance. Proper wireless network design helps ensure that all connected devices have sufficient, uninterrupted communication while minimizing potential collisions and limiting the impact of interference.

Internal Structures

The materials used in a building’s structure can cause varying degrees of wireless signal interference or blockage. Dense materials such as concrete and brick can significantly impede Wi-Fi signals. These factors should be carefully considered when installing APs to ensure optimal wireless coverage.

Mitigating Interference

A thorough site survey should always be performed to identify and address any sources of interference or potential Wi-Fi signal issues. POS devices require uninterrupted bandwidth and a clear communication path with both the CAPS and external networks. Failing to recognize and resolve interference can result in poor Wi-Fi connectivity and unstable performance, leading to financial loss and discrepancies. The interference survey should include the POS SSID and all APs used by the devices.

When assessing interference in the POS environment, tests should be conducted using the actual POS devices, as they provide the most accurate benchmark for performance. Testing with other Wi-Fi devices may yield different results, since wireless devices can respond differently depending on specific conditions. Testing should be conducted in all locations where POS devices operate, such as:
  • Kitchens
  • Corridors
  • Office spaces
  • POS device charging stations

Size and Scale

Wireless performance issues can affect venues of any size if basic best practices are not followed. Large venues may require multiple wireless controllers and hundreds of APs, while smaller venues might operate with just two or three. Regardless of a venue’s size or operational requirements, all wireless infrastructures can encounter problems. Performance can be compromised by both intentional and unintentional factors, making it essential for providers and vendors to proactively address and eliminate potential issues. Smaller venues, in particular, may be vulnerable to coverage gaps and interference from neighboring wireless networks.

Large venues and installations are more likely to encounter the following issues. Pay special attention to these areas when designing and verifying the installation:
  • Channel overlapping
  • Excessive number of APs in close proximity
  • High network demand
  • Bandwidth sizing issues
  • Network latency
  • Client management issues
  • DHCP issues
  • DHCP lease

Parent topic: Wireless Network