Customer Environment

Symptoms

1. Sticky Clients: Some clients may stick to a particular AP even when a closer, stronger signal is available from another AP. This can result in suboptimal performance and connectivity issues as the client fails to roam effectively.
2. Frequent Roaming: Conversely, some clients may roam excessively between APs, causing disruptions in connectivity and affecting network performance for both the client and other users.
3. Signal Strength Fluctuations: Clients experiencing roaming issues may exhibit erratic signal strength behavior, showing sudden drops or spikes as they connect and disconnect from different APs.
4. Performance Degradation: Roaming issues often lead to degraded network performance, increased latency, and intermittent connectivity problems for affected clients.

Troubleshooting Steps

After determining the statement of the issue, identify if this happens in every area or in a specific area. Identify if this happens with all devices, or with only a specific device.

In case the roaming issue is with a specific device, check the below item:

1.Client Configuration Checks

• Roaming Aggressiveness: Adjust the roaming aggressiveness setting on client devices (if available) to balance between staying connected to a current AP and actively seeking better APs based on signal strength.
• Driver and Firmware Updates: Ensure client devices have the latest network drivers and firmware updates to improve roaming algorithms and overall performance.
• Client device support: Verify that client devices support all channels permitted in the network configuration. For instance, some devices may not function properly on DFS (Dynamic Frequency Selection) channels. In such cases, clients will not roam to APs utilizing these channels, potentially causing connectivity issues

In case the roaming issue is with all devices, it should be something with the AP configuration or AP design deployment, check the below items:

2. Access Point Configuration and Design

• Optimizing AP Placement: This is crucial for ensuring seamless client roaming and overall network performance. APs should be strategically placed to provide adequate coverage overlap without causing excessive interference. Many roaming issues stem from poor AP placement, leading to shadow areas or overlapping AP signals that confuse devices and disrupt connectivity. Requesting a floor plan or conducting a site survey helps determine optimal AP positions. Additionally, isolating problem areas and analyzing neighboring AP signals via the AP dashboard can reveal potential design flaws such as excessive neighboring APs. While certain configurations can mitigate issues temporarily, a well-planned network design remains fundamental for optimal WLAN performance, emphasizing the importance of addressing design issues for a robust wireless network.
• Shutdown some APs: While there's a common belief that more APs equate to better Wi-Fi, the reality is more nuanced. Excessive AP density can lead to interference issues, especially in environments with numerous neighboring APs. If attempts to optimize channel selection using Automatic Channel Selection (ACS) do not sufficiently mitigate interference, consider strategically shutting down some APs. Although this action may temporarily impact throughput, it can significantly improve roaming performance by reducing interference and signal confusion. This can serve as a diagnostic measure, indicating potential issues with AP placement or density that require optimization for optimal Wi-Fi performance.
• Physical Obstructions: Evaluate physical obstructions like walls, large equipment, or metallic structures that can attenuate or block Wi-Fi signals, that can lead to hidden node problem.
• Channel and Power Settings: Check if the APs are utilizing all available channels. High airtime and retry rates may indicate congestion, so consider reducing channel bonding (40MHz or even 20MHz). When adjusting transmit power levels, activate Auto Cell Sizing (ACS) to ensure optimal performance. Be cautious when manually assigning power changes to each access point, as the wireless environment is dynamic. Manual configurations may temporarily resolve issues but can lead to recurrent problems. Only set AP power manually if a thorough site survey is available and neighboring AP interference is minimal.

• Interference Sources: Identify and mitigate sources of RF interference such as neighboring Wi-Fi networks, microwave ovens, Bluetooth devices, and cordless phones that can disrupt wireless connectivity and roaming.

• Roaming Assistance Features: You can enable features such as Fast Roaming (e.g., 802.11r/k/v) to facilitate seamless and faster client roaming between APs within the same network. Please check all customer device models to see if it supports the fast roaming feature.
• BSS min rate: Adjusting the BSS minimum rate impacts how devices maintain connectivity in a Wi-Fi network. Increasing this rate requires devices to have a stronger signal, promoting faster roaming decisions as devices move away from an AP. This helps them switch to a closer AP with a stronger signal promptly. Conversely, lowering the BSS minimum rate allows devices to stay connected at lower data rates, which is beneficial in areas with weaker signals. This reduces premature roaming due to temporary signal fluctuations, ensuring more stable connectivity in challenging signal environments.

• Client load balance: The load balancing feature may force clients to roam to less congested APs, even if the current connection is stable. This forced roaming can lead to frequent disconnections and reconnections as clients move between APs. Consider disabling this feature if clients are roaming frequently without a clear reason. This feature should only be used in environments where devices are stationary and some APs are close to each other, such as offices.
• Smart Roam: This feature disconnects clients when they reach a specific RSSI level. However, forcing clients to disconnect can worsen the situation. You should only use this feature as a last resort, such as when the customer is unwilling to change their AP deployment design.

• Wireless Packet Capture: Use packet capture tools to analyze roaming events, signal handoffs, and client behavior during roaming transitions. Look for anomalies such as delays or failed handoffs that may indicate potential roaming issues. Conduct an over-the-air (OTA) capture using two devices or a dual-channel scanning device. Select the channels of two adjacent APs that the device should roam between and perform the OTA capture.
• Analyze the OTA: Examine whether the client sends a reassociation frame and observe the AP's response. This analysis can reveal whether the client is attempting to reassociate, if the AP is rejecting the request, ignoring it, or not receiving the frame at all.
  You can filter in wireshark by using the filter: wlan.fc.type == 0
  This is what you should expect of a good roaming:
  
  Authentication request from client -> Authentication response from AP
  Reassociation request from client -> Reassociation response from AP (code: successful)
  

If the client sends an association frame instead of a reassociation frame, it will go through the entire authentication process again (not a seamless roaming). However, if the client sends a reassociation frame, the AP response will include a status code indicating the cause (e.g., 'Client rejected due to load balancing').

Workaround

• Shutdown some APs
• Activate ACS
• Activate roaming assistance feature
• Modify BSS min rate

Resolution

Based on the troubleshooting steps, you may encounter different resolutions. Here are the most common scenarios:
For Specific Device Issues:

• Follow troubleshooting steps to adjust client settings.
• If the issue persists, analyze OTA data for status codes and reassociation frames. Customer may have to contact the client device vendor for firmware fixes.

• Typically, network roaming issues stem from suboptimal AP placement rather than configuration or software issues (confirmed via OTA analysis).
• Consider adjusting channel bonding, activating Auto Cell Sizing (ACS), modifying BSS minimum rates, client load balancing, or utilizing smart roaming features.
• Although these adjustments can help in the roaming, a permanent solution requires optimizing AP placement through comprehensive site surveys or detailed floor plans.

Related Articles