USRP Software Radio
Frame content in transmitter / receiver
I have some questions about frame construction in the example "Packet-based Digital Link" from here (In attachment I additionally send all vi's): https://decibel.ni.com/content/docs/DOC-18801
The pramaters of the transmitter frame look like this:
Now my questions are...:
- What are guard bits? Are we receiving these bits at the receiver? What is their application? What are we using them for?
- How is PN order added to the synchronization bits? What is their application? How are they received at the receiver? What does the receiver do with them?
- What is packet number? Is it just a number from 1 to 46 when we send 46 packets?
- What are padding bits? Is it the beginning of a message repeated at the end of a frame? Are they ones alone, or zeros alone? For what purpose we transmit them and how do we receive them?
- What is blank frame? Is it used as an empty packet to ensure the connection is not lost? Is it received by receiver?
Is there any documentation describing the issues with this example? Could someone please explain these concepts to me?
By the way. Does the receiver in this example validate the received frame by checking every bit that is transmitted with every bit that is received? Or does it just check if the frame arrived and count it?
And one last question. What is the "Cyclic padding bits" in the image below? This control is located in "sub_generate_packet_array.vi". As far as I can see this value is copied from the bitstream and entered at the end of the frame. The value of "cycling padding bits" is calculated in "sub_calcpadding-symbolrate.vi" (last image), but why do we divide the "Samples per symbol" value by 160 for this purpose? And on the other side we logarithm this value by log2(x) and then multiply? Where does this come from?
