1. Channel width management
Channel width selection in Wi-Fi is an important factor that affects the performance and reliability of the wireless network. ST67W611M1 supports both 20 MHz and 40 MHz in the 2.4 GHz band. To understand how 20 MHz or 40 MHz is selected, the following general key aspects related to channel selection are introduced.
1.1. Channel selection key aspects
1.1.1. Understanding channel widths
Wi-Fi networks can operate on different channel widths, 20 MHz, 40 MHz, 80 MHz, and 160 MHz. The wider the channel, the more data it can carry, but it also becomes more susceptible to interference.
1.1.2. Frequency bands
Wi-Fi operates in different frequency bands, primarily 2.4 GHz and 5 GHz:
2.4 GHz Band: This band has fewer channels (usually 11 in the US) and is more prone to interference from other devices, like microwaves and Bluetooth. For the 5 GHz band, it has more channels (up to 24 non-overlapping channels) and supports wider channel widths, making it less congested and better suited for high-speed applications.
1.1.3. Manual channel width configuration
Network administrators can manually configure the channel width based on specific requirements:
20 MHz: Best for environments with high interference or many overlapping networks
40 MHz: Suitable for moderate interference and good for streaming and gaming
80 MHz and 160 MHz: Ideal for high-speed applications and environments with minimal interference
1.1.4. Client device capabilities
The channel width also depends on the capabilities of client devices. Some older devices may not support wider channels, so the network may need to use narrower channels to ensure compatibility. ST67W611M1 supports 20 MHz and 40 MHz in the 2.4 GHz band.
1.1.5. Regulatory constraints
Different countries have regulations on the use of certain channels and channel widths. Routers must comply with these regulations, which can affect channel width selection.
1.2. Automatic channel selection
Most modern Wi-Fi routers and access points use automatic channel selection (ACS) to dynamically choose the best channel and channel width based on the current network environment. ACS takes into account factors like:
1. Interference: The router scans for interference from other Wi-Fi networks and non-Wi-Fi sources.
2. Channel utilization: It checks how busy each channel is.
3. Signal strength: It measures the signal strength of neighboring networks.
Automatic channel selection (ACS) is a feature in Wi-Fi routers and access points that helps optimize the performance of the wireless network by selecting the best channel to use. Here’s a detailed explanation of how ACS works.
1.2.1. Scanning the environment
The access point periodically scans the available channels in the frequency band (2.4 GHz or 5 GHz) to gather information about the current network environment. This scan includes:
- Detecting interference: It identifies interference from other Wi-Fi networks and non-Wi-Fi devices (e.g., microwaves, cordless phones).
- Measuring signal strength: It assesses the signal strength of neighboring networks.
- Evaluating channel utilization: It checks how busy each channel is by measuring the amount of traffic and the number of active devices.
1.2.2. Analyzing the data
Once the scan is complete, the AP analyzes the collected data to determine the best channel. The analysis includes:
- Interference levels: Channels with lower interference are preferred.
- Signal-to-Noise ratio (SNR): Channels with a higher SNR are preferred, as they indicate a clearer signal.
- Channel utilization: Channels with less traffic and fewer active devices are preferred.
1.2.3. Selecting the best channel
Based on the analysis, the AP selects the channel that offers the best balance between low interference, high SNR, and low utilization. The goal is to choose a channel that provides the best performance and reliability for the network.
1.2.4. Adjusting channel width
In addition to selecting the best channel, ACS may also adjust the channel width (20 MHz, 40 MHz, 80 MHz, or 160 MHz) based on the network environment. Wider channels can provide higher data rates but are more susceptible to interference. The AP may choose a narrower channel width if the environment is congested.
1.2.5. Dynamic adjustment
ACS is not a one-time process. The AP continues to monitor the network environment and can dynamically adjust the channel and channel width as conditions change. This ensures that the network remains optimized even as new devices and sources of interference are introduced.
1.2.6. Timing of ACS
It does not occur during beacon or during normal transmission, ACS may be:
- Scheduled to occur at specific times (e.g., during the night when network usage is low)
- Triggered by specific events (e.g., detection of high interference)
During these times, the AP may briefly interrupt normal operation to perform a channel scan and reselection of channels and channel widths.
1.3. Conclusion for ST67W611M1
ST67W611M1 supports channel widths 20 MHz and 40 MHz in the 2.4 GHz band only. As explained above, the channel width is decided automatically by the AP according to the ACS procedure, or manually by the network admin configuration. In other words, ST67W611M1 application does not control it.