As the core component of modern wireless communication, the working mode of WiFi module directly determines the networking capability and application scenarios of the device. AP (Access Point), STA (Station) and AP+STA (mixed mode) are the three most common working modes, which correspond to different network roles and functions. This article will explain the principles, application scenarios, technical comparison and future trends to help beginners fully understand the characteristics of these three modes.

Ⅰ. AP mode

1. Working principle
The core of AP mode is to serve as the central node of the wireless network, responsible for creating and managing an independent wireless network.
(1) Signal broadcast: The AP module will continuously broadcast the SSID (network name) to allow other devices to discover and connect.
(2) Data forwarding: All communications between devices (STA) connected to the AP must be forwarded through the AP, for example, the communication between mobile phone A and mobile phone B must be forwarded by the AP.
(3) Typical architecture: The home router is a typical representative of the AP mode. It accesses the Internet through a wired network and then distributes the network signal wirelessly to mobile phones, computers and other terminals.
2. Application scenarios
Smart home control: Smart speakers, smart lights and other devices provide local wireless networks through AP mode, and users can directly connect to configure.
Temporary network construction: In conference scenarios, projectors or printers quickly create networks through AP mode for participating devices to access.
Industrial Internet of Things: Factory equipment is networked through AP mode to achieve centralized monitoring and management.

Ⅱ. STA mode

1. Working principle
STA mode defines the device as a client of the wireless network, which needs to rely on the network provided by the AP for communication.
(1) Active connection: The STA device scans the AP signals around it, selects the target network and accesses it through authentication (such as password).
(2) Data transmission: The STA device accesses the Internet or LAN resources through the AP, such as browsing the web after connecting a mobile phone to a router.
(3) Automatic reconnection: If the network is interrupted, the STA device will automatically try to reconnect to the saved AP after the signal is restored.
2. Application scenarios
Mobile device networking: Mobile phones, tablets, etc. connect to home or public WiFi through STA mode.
IoT terminals: Smart sensors, cameras and other devices upload data to cloud servers through STA mode.
Embedded systems: Industrial controllers connect to the enterprise intranet through STA mode to achieve remote monitoring.

III. AP+STA mode

1. Working principle
AP+STA mode allows the device to act as both AP and STA at the same time, with the dual functions of network creator and client.
(1) Parallel operation: On the one hand, the device connects to an external AP (such as a home router) as a STA, and on the other hand, it creates a local network as an AP for other devices to access.
(2) Data bridging: The data of the local network can be forwarded to the external network through the STA connection to achieve seamless expansion. For example, a smart home gateway connects to the router through STA and acts as an AP for other smart devices to access.
2. Application scenarios
Wireless repeater: When extending the WiFi coverage, the repeater connects to the main router through STA and then broadcasts the signal in AP mode.
Smart device configuration: When the smart socket is used for the first time, the mobile phone is directly connected to configure the network parameters through AP mode, and then switched to STA mode to connect to the network.
Internet of Vehicles: The vehicle-mounted device acts as an AP for passengers to connect, and at the same time connects to the cellular network through STA mode to provide real-time navigation.

Ⅳ. Selection of three models

(1) Select AP mode when independent networking is required (such as temporary conference network).
(2) Select STA mode when only access to the network is required (such as smart socket).
(3) Select AP+STA mode when both network connection and network extension are required (such as wireless repeater).