AP, short for Access Point, serves as the creator of a wireless network and the central node of the network. A typical home or office wireless router is an AP.
STA, or Station, refers to every terminal device connected to the wireless network, such as laptops, PDAs, and other user devices capable of network connectivity.
In a Wireless Local Area Network (WLAN), a Station (STA) generally acts as a client. It can be a computer equipped with a wireless network card, a smartphone with a WiFi module, either mobile or stationary. The process of STA accessing the wireless environment includes verifying whether the STA has the permission to establish a link with the Access Point (AP), determining if the STA can access the WLAN, and, after the STA has accessed the WLAN network, authenticating its permission to access the Internet.
During the link establishment between STA and AP, when the STA scans for an accessible Service Set Identifier (SSID) via Beacon frames or Probe response frames, it will select an appropriate SSID to access based on the Received Signal Strength Indication (RSSI) in the received Beacon or Probe response frames.
1. AP (Access Point): The concept of a wireless access point is quite broad. To put it simply, you can think of the CC3200 as a wireless router. This router cannot be plugged into an Ethernet cable, has no Internet access, and can only wait for other devices to connect, with the capacity to connect to only one device, somewhat similar to the peer-to-peer mode.
2. STA (Station): Any device that accesses a wireless AP can be called a station. In plain terms, it's the devices that usually connect to a router.
3. SSID (Service Set Identifier): Every wireless AP should have an identifier for user recognition. The SSID is precisely this name for user identification, which is what we commonly refer to as the WiFi name.
4. BSSID: Every network device has a physical address for identification, known as the MAC address. It usually has a default value when leaving the factory, which can be changed, and follows a fixed naming format, serving as an identifier for device recognition. For STA devices, the MAC address of the AP access point it connects to is the BSSID.
5. ESSID: It is a rather abstract concept. Essentially, it is the same as the SSID (also a string of characters). If several wireless routers share the same name, we can think of it as an expansion of the SSID. So, the common name shared by these routers is called the ESSID. (For example, if the WiFi signal released by a single router is named "China_CMCC", this "China_CMCC" is the SSID; if multiple routers all release this WiFi signal, the name that they all follow, "China_CMCC", is the ESSID.)
6. RSSI: It is easier to understand. It represents the signal strength of the AP site scanned by the STA.
For instance, in a large company, several wireless access points (APs or wireless routers) are installed. Company employees only need to know one SSID to access the wireless network anywhere within the company. The BSSID is, in fact, the MAC address of each wireless access point. When employees move around the company, the SSID remains unchanged. However, the BSSID keeps changing as they switch to different wireless access points.
Metaphorically speaking, the BSSID is like the specific store number (001) or address of a chain store, the SSID is the name or logo of the chain store, and the ESSID is the headquarters, signboard, or brand of the chain store. Usually, the SSID and the ESSID are identical.
AP Application Mode:
When the WIFI serial server is used as an AP, other WIFI serial servers and computers can connect to this WIFI serial server as STAs. Meanwhile, it can also be connected to user devices via UART or GPIO interfaces, as shown in the figure.
Metaphorically speaking, the BSSID is like the specific store number (001) or address of a chain store, the SSID is the name or logo of the chain store, and the ESSID is the headquarters, signboard, or brand of the chain store. Usually, the SSID and the ESSID are identical.
STA Application Mode:
The SC - WE824 serial server, acting as a STA, connects to other APs (such as routers in a local area network), forming a wireless network. All STAs take this AP as the center of the wireless network, and the mutual communication between STAs is completed through the AP's forwarding function, as depicted in the figure.
AP+STA Application Mode:
The SC - WE824 serial server can support one AP interface and one STA interface simultaneously. After enabling the AP+STA function, both the STA and AP interfaces become available. The STA interface of the serial server is connected to the router and further linked to the server in the network via TCPB. At the same time, the AP interface can be connected by mobile phones, PADs, etc. (connected via TCPA).
In this way, the TCP Server in the network, mobile phones, PADs, etc. can all control the serial devices connected to the SC - WE824 serial server or set the parameters of the serial server itself, as shown in the figure.
With the AP+STA function, it is extremely convenient to use handheld devices like mobile phones and PADs to monitor user devices without changing the original network settings.
The AP+STA function also enables easy wireless configuration of the serial server, resolving the previous issue where the serial server could only be configured via the serial port when in STA mode.
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