Testing, Validation, and Debugging

Testing

Taking Measurements

The coverage area of access points (APs) should be evaluated by measuring the data rate or signal quality for all broadcasting APs at various distances and locations, rather than relying solely on signal strength shown in the heat map open-plan view.

Understanding Wi-Fi Heat Maps

An open-plan heat map provides a visual overview of Wi-Fi coverage across the entire area. However, this type of measurement does not allow for monitoring or analyzing individual SSIDs or specific MAC (Media Access Control) addresses.

Recognizing Service Set Identifiers (SSIDs)

Each AP broadcasts the SSID MAC address, which is different from the hardware MAC address of the AP itself. Wi-Fi monitoring applications cannot monitor a specific AP directly; they monitor all SSIDs that the AP broadcasts. APs can be configured to broadcast multiple SSIDs, such as those for open public networks, internal staff networks, and dedicated POS networks.

Grouping All SSIDs

Not all wireless networks are visible, so analyzing both visible and hidden SSIDs is necessary to accurately identify and group all networks configured to broadcast from each AP. Grouping all detected MAC addresses helps estimate the correct number of individual networks in a given area, since neighboring SSIDs from nearby locations may also appear within the designated coverage area.

Creating a Wireless Network Map

You can create a wireless network map by analyzing the following information:
  • Hidden and visible MAC addresses in the 2.4 GHz and 5 GHz bands
  • Hidden and visible SSID channels in the 2.4 GHz and 5 GHz bands
  • Amplitude (dBm) of hidden and visible SSIDs channels in the 2.4 GHz and 5 GHz bands

This analysis helps you visualize network coverage, identify signal strength, and detect possible interference in your wireless environment.

Creating a MAC Address Map

You can create a Wi-Fi map using the MAC addresses in the 2.4 GHz and the 5 GHz bands.

SSID MAC addresses can be grouped by identifying and comparing similarities among them. This helps in organizing and distinguishing networks that may belong to the same AP or network segment.

The following table demonstrates how four different SSIDs, all originating from a single access point, have similar MAC addresses. This similarity helps identify that these SSIDs are broadcast by the same device.

Table 7-5 Example of SSID MAC Address Grouping for 2.4 GHz and 5 GHz Wi-Fi Bands

Wi-Fi Band Example SSIDs, MAC Addresses, and Channels
2.4 GHz Band

SSID1 MAC Address 1C:59:9B:A6:74:01 Hidden SSID Channel 1

SSID2 MAC Address 1C:59:9B:A6:74:02 Visible SSID Channel 1

SSID3 MAC Address 1C:59:9B:A6:74:03 Hidden SSID Channel 1

SSID4 MAC Address 1C:59:9B:A6:74:04 Visible SSID Channel 1
5 GHz Band

SSID1 MAC Address 1C:59:9B:A6:74:20 Hidden SSID Channel 46

SSID2 MAC Address 1C:59:9B:A6:74:21 Visible SSID Channel 46

SSID3 MAC Address 1C:59:9B:A6:74:22 Hidden SSID Channel 46

SSID4 MAC Address 1C:59:9B:A6:74:23 Visible SSID Channel 46

Creating a Hidden and Visible SSID Channel Saturation Map

The channel saturation factor should only be considered for adjustment if the dBm levels are similar within the specific area being tested. Saturation levels can vary depending on the tester and the position of the AP; therefore, channel saturation identified in one area should not be assumed to affect all areas.

Channel saturation varies in different areas, and is dependent on three factors:
  1. Number of APs installed in the area
  2. Number of APs in the neighboring area
  3. APs configured with static channels

The following table illustrates channel 1 saturation, with varied amplitude (dBm) signal levels broadcast from several APs in the area. The dBm levels differ significantly between SSIDs, so this scenario does not pose a problem for devices if the roaming threshold is set correctly. POS devices in this sample area will connect to the AP with the strongest signal and will only switch to another AP if a stronger signal is detected.

Table 7-6 Example of Hidden and Visible SSID Channels for 2.4 GHz and 5 GHz Wi-Fi Bands

Wi-Fi Band Example Hidden and Visible SSID Channels
2.4 GHz Band

SSID1 MAC Address 1C:59:9B:A6:74:01 Hidden SSID Channel 1 dBm -30

SSID2 MAC Address 1B:01:00:C6:80:AB Visible SSID Channel 1 dBm -65

SSID3 MAC Address 1A:00:02:01:AA:03 Hidden SSID Channel 1 dBm -78

SSID4 MAC Address AA:60:9C:A1:04:C1 Visible SSID Channel 1 dBm -81
5 GHz Band

SSID1 MAC Address 1C:59:9B:A6:74:AA Hidden SSID Channel 46 dBm -30

SSID2 MAC Address 1B:01:00:C6:80:AB Visible SSID Channel 46 dBm -65

SSID3 MAC Address 1A:00:02:01:AA:AC Hidden SSID Channel 46 dBm -78

SSID4 MAC Address AA:60:9C:A1:04:A4 Visible SSID Channel 46 dBm -81

Creating a Hidden and Visible SSID Amplitude dBm Map

The following table demonstrates channel overlap caused by four APs positioned in close proximity. This situation often results from a poorly configured Wi-Fi network or manual channel assignments. Devices connected to these APs may experience interference and connection instability. To reduce interference, each AP should be assigned a unique channel, taking into account its distance from other APs in the area.

Table 7-7 Example of Hidden and Visible SSID Amplitude dBm for 2.4 GHz and 5 GHz Wi-Fi Bands

Wi-Fi Band Example Hidden and Visible SSID Amplitude dBm
2.4 GHz Band

SSID1 MAC Address 1C:59:9B:A6:74:01 Hidden SSID Channel 1 dBm -55

SSID2 MAC Address 1B:01:00:C6:80:AB Visible SSID Channel 1 dBm -58

SSID3 MAC Address 1A:00:02:01:AA:03 Hidden SSID Channel 1 dBm -52

SSID4 MAC Address AA:60:9C:A1:04:C1 Visible SSID Channel 1 dBm -54
5 GHz Band

SSID1 MAC Address 1C:59:9B:A6:74:AA Hidden SSID Channel 46 dBm -55

SSID2 MAC Address 1B:01:00:C6:80:AB Visible SSID Channel 46 dBm -58

SSID3 MAC Address 1A:00:02:01:AA:AC Hidden SSID Channel 46 dBm -52

SSID4 MAC Address AA:60:9C:A1:04:A4 Visible SSID Channel 46 dBm -54

Debugging

When troubleshooting POS device performance issues, always collaborate with the Wi-Fi provider, as external tools can only capture a small portion of the overall network infrastructure. Logs and reports from the Wi-Fi provider are essential for effective troubleshooting because many details cannot be obtained through external observation alone.

The approach should be divided into the following sections:

Entire Wireless Enterprise
  • Learn about the entire wireless network and do not focus only on the POS network.
  • Obtain information from the wireless provider about the entire infrastructure.
POS Network Focus
  • Segregate the POS network from the enterprise and test its position within the infrastructure.
  • Perform tests from within the POS environment instead of focusing on the entire network.
  • Test POS network performance using POS devices and follow the communication path.
POS Data Capture
  • Gain an understanding of the POS data traffic and follow its complete path.
  • Use appropriate tools to capture data and seek assistance from the wireless provider when access to the internal network is limited.
Monitoring
  • Monitoring tests should occur during peak times when the network demand is highest.
  • Expand the monitoring field to all POS devices during the tests to capture more data.
  • Do not use a single POS device for monitoring as the results may be skewed by the POS device itself.
  • Do not use different Wi-Fi capable devices when testing wireless performance, as not all devices respond the same way.

Parent topic: Wireless Network