SOURCEFORGE » RALF » 2015 SDR for rapid prototyping of radio communications

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h1. *Channel and Coding Implementation*

h2. *AWGN Channel*

After establishing a basic channel, AWGN was then added as shown on Figure 5.5. The AWGN function has an Eb/No input, which is the target Eb/No of the signal (the Eb/No received).

p=. !{width: 60%}https://sourceforge.isae.fr/attachments/download/1503/withAWGN.png(AWGN Implementation)!

_Figure 5.5 Communication Diagram_

h2. *Coding*

In order to further improve the communication chain,  coding is applied to this channel, a illustrated in figure 6. The BER function in LabVIEW compares the received bit stream to the Galois generated PN sequence. At this point, as mentioned in the limitations, synchronization between the two USRP was an issue. From the time the Vi was ran, there was a delay of 3 seconds on the receiving side, plotting noise, before correcting plotting the constellation. The received bits did not maintain a fixed value (since the transmitter and receiver were continuously transmitting and receiving) but rather kept changing (between 0 and 1) throughout the test, giving a BER of 1. For this reason, it was necessary to calculate the BER without the use of USRPs. 

p=. !{width: 60%}https://sourceforge.isae.fr/attachments/download/1505/withCoding.png(Channel and Coding)!

_Figure 5.6 AWGN and Coding_