Added docs and img folders

radio_module_identify.md and related images added.

Author: peknis01

docs/img/Radio_Identifications.png

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+## Radio module identification
+
+* Make sure that you are using the same radio modules on both server and client sides:
+
+	* If the radio module on the gateway router supports the 2.4 GHz frequency band, the client side must have an mbed 6LoWPAN shield that uses a 2.4 GHz radio module (such as Atmel AT86RF233).
+
+	* If the radio module on the gateway router supports the sub-GHz frequency band, the client side must have an mbed 6LoWPAN shield that uses a sub-GHz radio module (such as Atmel AT86RF212B).
+
+* An easy way to identify which frequency band your setup uses is to check the **Antenna size** on the radio module:
+
+	* The sub-GHz band antenna is larger than the 2.4 GHz antenna.
+
+	* For the client side (mbed 6LoWPAN shield connected to an FRDM-K64F board), see the image below:
+  ![](img/Radio_Identifications.png) 
+
+	* For the gateway router, see the image below:
+  ![](img/Radio_Identifications_GW.png)