3.1 Scanning

A transmitted signal is subject to reflections and refraction on walls, surfaces, and so forth. The receiving node sees signals differing in phase and amplitude. All these signals superposition at the RX antenna, causing an effect called “fading”. Using more than one antenna allows the evaluation of different multipath scenarios to avoid or reduce the effects of fading and interferences.

Scanning is a process Wi-Fi devices use to detect other remote Wi-Fi devices (usually detection of access points before connection). This process can also be used for environment status or other measurements.

There are three primary scan types: Table 11 describes their different purposes and execution. Each scan completes in a different amount of time, depending on variables such as scan type, configuration, and regulatory rules.

The scan execution in the system is independent and can be executed between other Wi-Fi activities. When a scan is executed in parallel to those activities, it can impact things such as throughput or multi-role (MR) scenarios.

Some typical examples:

• Multi-role scenario, where STA and AP roles run traffic to remote devices. Executing a scan impacts the throughput by up to 80% (during the scan itself) each time a channel is scanned off.
• Multi-role scenario where STA is connected and AP is idle. Executing a scan could lower the connection success rate of a remote STA to less than 100%.

This should be taken into account when frequently executing scans.

The examples in Table 11 describe the shortest, typical, and longest scan process.