How to Simplify Wi-Fi Analysis with LinkIQ™ Duo

Site survey tools that generate heat maps provide a valuable visual representation of Wi-Fi signal strength using a color-coded approach, but they don’t necessarily tell the whole story. When troubleshooting modern Wi-Fi networks in the field, you need to consider additional factors such as channel utilization, co-channel and adjacent channel interference from devices that are on your network, and neighboring networks. The Fluke Networks LinkIQ™ Duo Cable+Wi-Fi+Network Tester gives you this deeper dive, providing clear, comprehensive insights about your entire RF environment.

Understanding the Channel Graphical Interface

The LinkIQ Duo tester lists all available Wi-Fi networks (SSID) by name, along with signal strength, security status, Wi-Fi technology supported, and the number of APs within range. It also shows all available APs, including the name (BSSID) of each AP radio and a summary of the networks and Wi-Fi technology each supports, plus signal strength, security status, frequency bands, and channels. With the LinkIQ Duo tester, you can easily test the signal strength and the transmit and receive rates for specific APs in specific bands — which is quite handy, since phones and other consumer devices don’t let you control which AP you connect to.

Where the LinkIQ Duo tester really excels is in its unique ability to display a combination of channel utilization, signal strength, and interference for AP radios in the 2,4 GHz, 5 GHz, or 6 GHz frequency bands. When you choose “Channels” from the home screen, the LinkIQ Duo tester shows all three of these critical factors in a single intuitive screen for fast analysis. Here is a closer look at that interface.

1. Channel utilization is designated by the light blue bar that corresponds to the left axis. In general, channel utilization below 50% will provide the best performance, especially for high-throughput applications such as video streaming. Here, the LinkIQ Duo tester shows that channels 149 through 161 are currently busy, while channels 144 and 165 have very low utilization. If these channels consistently see such high utilization, users may experience poor performance, and it may make sense to take actions such as moving AP radios to less-busy channels or installing additional APs to handle the traffic.

2. The blue dots denote the number of AP radios using that channel. Here, the LinkIQ Duo tester hears four radios operating on channel 149.

3. AP radios are positioned on the graph according to their signal strength (dBm), which corresponds to the right axis. A higher dBm value (closer to zero) indicates a stronger signal, which correlates with higher data transfer speeds and more reliable connections. A general rule is that a signal strength of -65 dBm or better is preferred to support applications like voice and video. A signal strength of -65 dBm to -75 dBm may be adequate for low-speed applications such as email — anything less is likely too weak to be useful. Here, the LinkIQ Duo tester shows that the AP radio operating on channel 161 has an excellent signal strength of -29 dBm. Also in this location, one radio on channel 149 has a good signal of about -50 dBm, along with three others with weaker signals below -70 dBm. Co-channel interference is present here, as there are multiple radios visible on the same channel. Users of all four radios will share the channel, which could lead to lower performance. If users in this area are using one of the three low-signal radios, their performance will be impacted further. Low signal strength could be due to excessive distance from the APs, physical obstacles, or interference. The 5 GHz and 6 GHz bands are more susceptible to signal weakening by walls, doors, and furniture, especially materials like concrete and metal.

4. Switching on the Channel Overlap feature displays a horizontal line to show the range of channels an AP radio is using so you can see where there is potential channel overlap. AP radios can be set up to use multiple adjacent channels, which increases performance but may interfere with other radios on those channels. For example, the LinkIQ Duo tester shows that the radio operating on channel 161 is using a 40 MHz wide channel (two standard 20 MHz channels) that extends into channel 157. The overlap line shows that this will interfere with any radios operating on that channel. Notice that the radios on channel 149 are using 80 MHz wide channels, so they will all interfere with the radio on channel 161. When two or more APs in the same space have radios using use the same channel(s), they create co-channel interference. APs then share the bandwidth, potentially limiting performance. Overlapping (also known as adjacent channel interference) is potentially a more significant issue. While APs with radios on the same channel will cooperate to share bandwidth, APs with radios using different channels that overlap will not, leading to more dropped packets and retransmissions. Avoiding overlapping channels can therefore result in better performance.

Delving Deeper into the Channel

The LinkIQ Duo tester lets you take a deeper dive from the Channels screen. In the graphic below, selecting channel 149 shows details such as utilization over time and a list of AP radios operating on that channel, with their BSSID, network, and signal strength. You can also see the range of channels for each AP radio and turn on “Adjacent Radios” to see other radios operating on adjacent channels, which can cause interference.

1. Channel utilization over time for channel 149.

2. List of AP radios operating on channel 149 in order of signal strength.

3. Channels for AP radios operating on channel 149. Here, the LinkIQ Duo tester shows that the radio f0:21:e0:f2:89:61 is configured with primary channel 149, and the horizontal line indicates that it is configured to use an 80 MHz wide channel, covering channels 149 through 161.

4. When the Adjacent Radios option is selected, radios with a different primary channel but overlapping the selected channel are displayed. Here, the LinkIQ Duo tester shows an adjacent radio whose primary channel is 157 with an 80 MHz bandwidth, which means it could interfere with the selected channel (149). This radio, however, has too weak a signal to interfere with other devices at this specific location. In fact, the blank signal strength reading -dBm indicates that the LinkIQ had previously “seen” this radio but is not currently seeing any beacons from it.

Gaining Insights into Individual Access Points

Users can select a specific radio from the LinkIQ Duo Channel Details screen to view its Access Point Details. In the graphic below, we’ve selected the radio with BSSID f0:21:e0:f2:89:61 with primary channel 149 to see details such as BSSID, name (if available), country code, all radios operating in each frequency with its primary channel, and the networks supported by the AP. Touching the down arrows to the right of the radio entries will display channel bandwidth (size), channel range, signal strength, and channel utilization over time.

1. Access point details, including BSSID, name (if available), networks, and country code.

2. The Notes section displays potential problems such as overlapping channels, weak encryption, and weak signals.

3. List of all radios in the AP, including their frequency and primary channel. This AP has one radio operating at 2,4 GHz on channel 6 and one operating at 5 GHz on channel 149.

4. List of all networks supported by the AP.

5. Detailed information for the AP radio operating at 2,4 GHz, including signal strength and channel utilization.

6. Detailed information for the AP radio operating at 5 GHz, including signal strength and channel utilization.

Running a Wi-Fi Connection Test

From the Access Point Details screen on the LinkIQ Duo tester, users can touch Test to select a network to see all radios operating on that network and run Wi-Fi connection tests for specific radios to determine signal strength, transmit and receive rates, and latency (ping).

On the screens below, we’ve selected the radio operating at 5 GHz on the network “OliverhouseHS Guest” to run a Wi-Fi connection test. You can easily save the results of a Wi-Fi connection test with descriptive names in the tester or export the data from the tester to Fluke Networks LinkWare™ PC software for storing results and generating PDF reports.

With its simple, easy-to-use Wi-Fi testing interface, the LinkIQ Duo Cable+Wi-Fi+Network Tester lets you confidently navigate the complexities of modern enterprise Wi-Fi. It essentially tells you everything you need to know about your Wi-Fi environment, empowering you to make informed decisions for optimal Wi-Fi coverage and performance, and helping you to pinpoint problem areas easily for quick resolution. And with the LinkIQ Duo tester, you can also test the wired network, cabling, and PoE operation that your Wi-Fi APs rely on.

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