Design and Analysis
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      Analyzing Survey Results

      Analyzing the vast amount of data collected from a wireless survey can feel overwhelming. In this article, we’ll walk through sample data, what to examine, key insights to look for, and how to interpret the results. This is not an exhaustive list but rather a starting guide to help you get oriented.

      The Overview Screen

      The overview screen provides a high-level summary of the survey data and is the best place to start. Here’s why:

      • It ensures that SSIDs are correctly assigned to each band (2.4 GHz, 5 GHz, 6 GHz).
      • The color bars offer a quick visual representation of network health.
        • More green in these bars indicates a well-performing network.
        • Yellow and orange are not necessarily bad but signal areas that may need further attention.
        • If green is not the dominant color, potential issues should be investigated.

      By starting with the overview, we can quickly assess the general state of the network before diving into more detailed analysis.

      Evaluating Coverage

      Next, let’s take a look at Coverage. A good starting point for primary coverage is setting the threshold between -65 dBm and -67 dBm. These values serve as a general guideline for assessing adequate signal strength.

      • These thresholds align with VoIP over Wi-Fi best practices, ensuring a strong and stable connection.
      • VoIP over Wi-Fi typically requires a minimum signal strength of -67 dBm with an SNR of at least 25 dB for reliable performance.
      • Setting coverage parameters in this range provides a clear baseline for identifying areas that may need adjustments.

      By establishing these coverage settings, we can create a solid foundation for analyzing network performance before diving into more detailed optimizations.

      If most areas in the environment maintain a signal strength of at least -67 dBm, time-sensitive traffic—such as VoIP or video calls—should have a good user experience from a coverage perspective.

      Understanding the Secondary Threshold (-73 dBm)

      The second coverage is more subjective, but generally:

      • Around -73 dBm, lower-powered mobile clients may start experiencing reduced efficiency.
      • Clients tend to shift to lower QAM rates, impacting throughput.
      • Some clients may begin to experience intermittent disconnects.

      Interpreting the Coverage Map

      As seen below, most areas are displaying green, which indicates strong primary coverage. Areas with yellow or orange may require further analysis to determine if adjustments are needed for improved client performance.

      By keeping these thresholds in mind, we can ensure the network is optimized for both coverage and client connectivity.

      AP Coverage and Power Settings

      When an AP is selected, we can begin a more detailed analysis of its coverage and effectiveness.

      In the image below, a single AP is covering three rooms. While this isn’t necessarily a bad thing, it’s important to consider the intended design—especially if the building is configured with one AP per room.

      Assessing Power Settings

      • If each room has its own AP, but one AP is covering multiple rooms, the current power setting may be too high.
      • The ideal coverage pattern in this scenario would be:
        • The AP primarily covering its designated room.
        • Adjacent rooms receiving moderate coverage.
        • The far edges fading into yellow or orange, indicating a natural signal drop-off.

      By fine-tuning AP power settings to match the building’s deployment strategy, we can ensure better client distribution, reduce interference, and optimize overall performance.

      When analyzing coverage, it’s important to evaluate the signal strength beyond the primary threshold (e.g., -67 dBm). While this value is not directly tied to primary coverage, it plays a significant role in the network's ability to transmit data effectively, particularly as it relates to CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance).

      How CSMA/CA Works

      At a high level:

      1. Before any wireless client or AP can transmit data, it must listen to the channel.
      2. The device checks for:
        • Wi-Fi traffic already transmitting on the channel.
        • Non-Wi-Fi interference on the same frequency.
      3. If the channel is busy, the device must wait before transmitting, helping prevent collisions.

      The Impact of AP Power Levels

      • In dense environments, keeping AP power levels lower is crucial.
      • High power settings can cause overlapping cells on the same channels, which:
        • Increase the chance of interference.
        • Force clients and APs in adjacent cells to wait longer to send traffic, reducing overall efficiency.

      By carefully managing AP power levels, we can minimize these overlapping cells, improve transmission efficiency, and enhance overall network performance, especially in environments with high client density.

      Analyzing Coverage and Channel Bonding

      In the image above, the selected hexagon represents a specific point, displaying the coverage strength and other parameters at that location.

      Key Observations

      1. At this point, the strongest signal is on a 40 MHz bonded channel (36+40).
      2. However, there are areas of interference, as several APs are broadcasting on 80 MHz bonded channels (36+40+44+48).

      Interference and Overlap

      • Green channels in the image represent other APs on the same ESS (Extended Service Set), meaning they are part of the same WLAN as the selected AP.
      • While some overlap is inevitable in any environment, excessive overlap can:
        • Increase interference.
        • Reduce Wi-Fi efficiency due to contention and delays.

      Mitigating Overlap with Power Adjustments

      • Adjusting AP power levels is a practical way to minimize overlap.
      • By reducing the power of APs, especially those on the same channels, we can:
        • Decrease interference.
        • Ensure better signal-to-noise ratios (SNR) for clients.
        • Improve overall Wi-Fi performance in the environment.

      By carefully managing channel bonding and power settings, network efficiency can be significantly enhanced, even in environments with multiple APs and overlapping coverage.

      Understanding the AP Details View

      On the right side of the screen, a detailed view lists all the APs detected at the selected location. This view provides a wealth of information to help analyze network performance and troubleshoot issues.

      Key Information Displayed

      1. AP Name and Manufacturer:

        • Identifies the specific AP and its hardware brand.

      2. Channel and Channel Width:

        • Shows the operating channel (e.g., 36) and the bonded channel width (e.g., 20 MHz, 40 MHz, or 80 MHz).

      3. SSID(s):

        • Displays the network names (SSIDs) being broadcast by each AP.

      4. Received Signal Strength (RSSI):

        • Indicates the strength of the signal received from the AP at this location.

      5. Broadcast Power:

        • Provides insight into the power level the AP is using to transmit.

      Using This View

      This information allows for:

      • Comparing APs in the same location to evaluate which APs provide the strongest signal or are causing interference.
      • Identifying channel overlap or inefficient channel usage.
      • Verifying SSID broadcasts and their corresponding signal strengths.

      By understanding and utilizing this view, you can gain a clearer picture of the wireless environment and make adjustments to optimize performance.

      Key Considerations for Channel Width, RSSI, and Secondary Coverage

      Channel Width

      Monitoring channel width is critical for optimizing network performance. While deploying APs with 80 MHz channels may seem ideal, external factors, such as interference from neighboring buildings, can impact the feasibility of this plan.

      • Neighboring Wi-Fi networks broadcasting on the same channels can disrupt your desired channel plan.
      • In the current environment, 80 MHz channels could likely be deployed with adjustments, but this was only discovered after completing a survey of the neighboring Wi-Fi environment.
      • Takeaway: Always survey the wireless environment to detect external networks that could affect your channel width and adjust your plan accordingly.

      RSSI (Received Signal Strength Indicator)

      Understanding RSSI is essential, as it represents the strength of the signal received by clients. However, there are key considerations to keep in mind:

      • Client Variability: Each client device observes RSSI differently based on its antennas, radios, and programming.
        • This variability limits how much control WLANs have over RSSI-based behavior.
      • Roaming Decisions: Clients use RSSI, among other factors, to decide when to roam to a different AP. Excessive roaming can degrade user experience.
        • Periodically check RSSI levels to ensure clients are not unnecessarily roaming.
      • Calibration: Ensure that the Sidos Wave's offset aligns with the behavior of most clients in your environment for accurate signal strength measurements.

      Secondary Coverage

      In addition to primary coverage, secondary coverage should also be assessed to ensure network resilience.

      • What is Secondary Coverage?
        Secondary coverage represents the signal strength that would remain if an AP were to fail.
      • In the example shown, secondary coverage is excellent, as most areas remain green, indicating strong coverage even in the event of an AP failure.
        • Benefit: This ensures that users experience minimal or no impact, maintaining a seamless experience.

      Summary

      Balancing channel width, RSSI, and secondary coverage is critical for a robust and efficient WLAN.

      • Use surveys to identify external interference and adjust channel width accordingly.
      • Regularly evaluate RSSI to prevent client roaming issues and ensure accurate alignment with client behavior.
      • Prioritize strong secondary coverage to ensure the network remains reliable even during hardware failures.

      By addressing these factors, the overall performance and reliability of the network can be significantly enhanced.

      Secondary Coverage on Adjacent Floors

      When analyzing secondary coverage in this example, we noticed that one of the rooms lacks sufficient secondary coverage.

      Key Observation

      • This does not necessarily indicate a problem, but it’s an important detail to keep in mind.
      • If the AP in this room were to fail, the impact might be more noticeable compared to failures in other rooms with stronger secondary coverage.

      Why This Matters

      • Secondary coverage ensures a seamless user experience even during AP failures.
      • In areas without strong secondary coverage, users may experience degraded service, especially in high-density environments or areas requiring consistent connectivity.

      Actionable Steps

      • Consider adjusting power levels or adding overlapping coverage to reduce the impact of an AP failure in critical areas.
      • Monitor the room's usage patterns and client density to determine if additional adjustments are necessary.

      By being aware of rooms with weaker secondary coverage, we can proactively address potential issues and maintain reliable network performance.

      Analyzing and Addressing Interference

      Let’s shift the focus from coverage to interference. Interference can arise from various sources, including:

      • Neighboring APs
      • Overlapping channels
      • Adjacent channels

      Interference View

      In this view, interference is represented by two colors:

      • Green: Indicates acceptable levels of interference.
      • Red: Highlights areas where interference needs attention.
        By clicking on a hexagon, the channel utilization of the environment provides insight into how interference is distributed.

      Key Observations in This Environment

      • Most of the interference comes from overlapping channels, caused by both internal APs and neighboring APs.
      • The lower four 20 MHz channels are heavily occupied by several APs from neighboring networks. These channels are beyond our control and should be avoided.

      Best Practices for Reducing Interference

      1. Adjust Channel Assignments:

        • Reconfigure your APs to use less congested channels. Avoid heavily occupied channels whenever possible.

      2. Lower AP Broadcast Power:

        • Reducing broadcast power shrinks coverage cells, minimizing overlapping channel interference. This is especially useful in environments with high AP density.

      3. Evaluate Channel Bonding:

        • In environments with significant interference, it may be better to reduce channel width (e.g., from 80 MHz to 40 MHz) to improve coexistence.

      By carefully managing channel plans and adjusting broadcast power, you can significantly reduce interference and enhance overall network performance.

      Using the AP Interference View for Troubleshooting

      On the left side of the window, each detected AP displays how much of its coverage cell is impacted by interference. This is an excellent starting point for identifying and addressing problem areas.

      Why Start Here?

      • The interference data on the left provides a clear breakdown of the most impacted APs.
      • By focusing on APs with the largest interference zones, you can prioritize fixes for the areas with the greatest impact on network performance.

      Cascading Benefits of Fixing Large Areas

      • Resolving interference in larger areas often leads to improvements in smaller surrounding areas.
      • This is because reducing interference at one AP can minimize overlapping channel issues for adjacent APs and improve overall network efficiency.

      How to Proceed

      1. Start with the APs showing the highest interference levels.
      2. Address issues such as:
        • Channel overlap
        • Adjacent channel interference
        • AP broadcast power
      3. Reassess the interference map to verify that smaller areas of interference have also improved.

      By systematically addressing interference starting with the largest problem areas, you can streamline the optimization process and enhance the network's overall performance.