Start work on chap. 3: software

doc/smart_home_technical_paper

@@ -33,5 +33,14 @@ Keywords: Smart Home, Presence detection, Node-red, mqtt, gateway, raspberry pi
   To circumvent this limitation, the raspberry pi is used as a wireless access point running a standalone network.
   the sensors will connect to this standalone network, in which the gateway is the host with a static ip-address, and send their gathered data via the network to the gateway for further processing.
   
+  To communicate with commercial sensors the radio-tranciever HM-MOD-RPI-PCB from ELV is used.
+  It provides an easy to use 868,3/869,525 MHz radio tranciever which connects to the raspberry pis GPIO-Pins
+  
 3. THE SETUPS SOFTWARE
   [IMAGE]
+  The smart home environment is comprised of three key layers: 
+  the logic-layer with node-red and node-red-dashboard implements the logic for the presencedetection and the graphical user interface.
+  node-red is used because it provides an easy-to-use flow-based programming interface.
+  data is represented by nodes 
+  mqtt is the protocol used in the networking-layer to relay data coming in from sensors to the logic-layer.
+  the interface-layer is used to connect