supplimental concurrent mode doc

docs/Concurrent_Mode.md

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+2021-12-03
+
+What is Concurrent Mode?
+
+Concurrent Mode creates 2 wireless network interfaces (wlan0, wlan1) and those
+two interfaces share the same WiFi adapter.
+
+This feature allows performing 2 separate wireless tasks at the same time with a
+single WiFi adapter.
+
+For example:
+
+Use station mode (called managed or client mode also) to connect with an
+AP to access the internet at the same time as it also performs as an AP
+to allow other devices to connect to the second interface.
+
+Note: Only supports 3 combinations
+
+1. Station mode + Station mode
+2. Station mode + AP mode
+3. Station mode + P2P mode
+
+-----
+
+How do I Enable Concurrent Mode?
+
+Run the following as instructed during the installation process:
+
+```
+./cmode-on.sh
+```
+
+Once the driver is fully installed and you have rebooted the system, you
+can verify that this works by typing the “iw dev” command, You should
+see two wireless interfaces, and the MAC address of secondary interface
+is nearly the same as the first except for one digit.
+
+-----
+
+FAQ:
+
+Q: Which wireless interface can run in station mode? Which
+wireless interface can run in AP mode?
+
+A: It is recommended to run station mode in wlan0 and AP or P2P mode in
+wlan1.
+
+Q: How is the throughput with 2 wireless interfaces in concurrent mode?
+
+A: Because there is only one physical hardware device, the two wireless
+interfaces (wlan0, wlan1) will share the transmit bandwidth.
+
+For example:
+
+Assume the throughput limitation of current environment is 85Mb/s,
+then the throughput of wlan0 + the throughput of wlan1 is basically
+equal or smaller than 85Mb/s.
+
+Q: Everything is fine when I only start hostapd, but when I start running
+station mode in the other interface at the same time, hostapd will disconnect
+for a moment then will reconnect again, however ,the channel is differ from
+before. Is something wrong?
+
+A: Don’t worry, it is fine! As mentioned before, those two wireless interfaces
+share the same physical hardware device. That means those 2 wireless interfaces
+must use the same channel. The AP/P2P interface should use the same channel as
+the station interface. If both interfaces are running in station mode, the
+connected APs MUST be on same channel.