The Wireless Testbed Academy contains source code that can be run on open wireless experimental testbeds. The following open experimentation/testing facilities are supported:

• iMinds w-iLab.t
• TUB TWIST
• TCD IRIS
• TUD
• JSI LOG-a-TEC

The channel gain experiment shows how the gain between a transceiver and a receiver can be measured on a real testbed such as the ones mentioned above. Simple cognitive radio source code

##Methodology for measuring the gain between two nodes

We consider a system formed by a single transmitter-receiver pair: TXi - RXj

    	+------+          +------+
		| TXi  | --hij--> | RXj  |
		+------+          +------+ 
		   |		         |
           |                 |
          _|_               _|_
          
     Fig. 1 hij - the channel gain between
                  transmitter i and receiver j

The procedure for measuring the channel gain is as follows:

• First, the receiver RXj measures the received power Pnoise knowing that the transmitter TXi is silent.

• Secondly, the receiver measures the received power PRXj knowing that the transmitter is transmiting with a given power PTXi

• The gain is then computed according to the formula:

      hij = (PRXj - Pnoise) / (PTXi) where:
  
                            - PRXj [W] is the power received at receiver j
                            - PTXi [W] is the power transmitted by transmitter i
                            - Pnoise [W] is the noise power.
  
     +------+                          +------+
     | TXi  | ----------hij----------> | RXj  |
     +------+                          +------+ 
  
     Fig.2 Ideal situation, where in the system there is no noise power
  
                    hij = PRXj / PTXi
  
  
  
     +------+                   +-----+        +------+
     | TXi  | ----------hij-----| ADD |------> | RXj  |
     +------+                   +-----+        +------+ 
                                   ^
                                   |
                                   |
                               +-------+
                               | noise |
                               +-------+
  
    Fig.3 Real situation, where the noise signal adds to the transmitted signal
  
                    hij = (PRXj - Pnoise) / (PTXi)
  

1. Measure the noise power. No signal should be generated by the transmitter during this step.
2. Generate a signal.
3. Measure the received signal
4. Calculate hij gain

For more details, browse the testbed specific CR code, including the respective README file and comments from the source code.

Videos of demos and tutorials on the facilities are available on the project web site and on the Youtube channel.

This work was partly funded by the EC under grant agreement n°258301 - Cognitive Radio Experimentation World.