Packet Communications
DRAFT (A Work in Progress)
This tutorial presents methods to transmit and receive packet data using burst transmissions. The data can originate from a message source or a stream source. A hardware implementation is shown using BPSK modulation.
Prerequisites
- QPSK Modulation / Demodulation
- BPSK Demodulation
- Polymorphic Types (PMTs)
- Stream Tags
- Message Passing
- Understanding ZMQ Blocks
- Packet Communications
Simulating Baseband Packet Processing
In order to grasp the basics of packet processing, this section presents a transmitter and receiver without any modulation or channel impairments.
Building the flowgraph
Build the following flowgraph using the details given below:
Message Strobe
For the Message Strobe to generate a PDU, the Message PMT must be of the form
pmt.cons(pmt.PMT_NIL,pmt.init_u8vector(9,(71,78,85,32,82,97,100,105,111)))
This specific vector has a length of 9 and the character values of "GNU Radio".
Variable, Id: hdr_format
The Protocol Formatter uses a Format Object to define its parameters. The one used in this example is
hdr_format digital.header_format_crc(len_key, num_key)
Protocol Formatter
The entry for the Format Obj. is 'hdr_format'
Protocol Parser
The entry for the Format Obj. is 'hdr_format'