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'