EE49 Lab 4: Introduction to Demodulation and Decoding: BPSK & QPSK

[ErikL]

Goal

The goal of this lab is to learn about demodulation, and implement the portions of a wireless BPSK receiver for a USRP-to-USRP link. Specifically we will be implementing a simple channel correction scheme, a BPSK symbol de-mapper, a preamble detection scheme, packet decoding, and a CRC error check.

(Learn more about the NI USRP software defined radio platform.)

Lab Overview

Course Overview

This lab is from a course developed at Stanford University entitled Building Networked Systems. The course was first taught with a trial group of students in the Spring 2011 quarter. With the software/hardware combination of LabVIEW and the NI USRP, students were able to build and explore each element of a complete communications system signal chain. The course progression covered topics including channel coding, modulation, demodulation, timing recovery and culminated with students building their own protocol.

Course evaluations affirmed that students were highly engaged in and benefited greatly from the EE 49 class.  “The course evaluations for our class were fantastic,” said Katti. “Students rated the class 4.94/5.0, likely making it one of the highest rated among all classes in the School of Engineering at Stanford.”  To learn more about the course view the case study entitled: Designing Hands-On Wireless Communications Labs With the NI Universal Software Radio Peripheral and ....

These materials are considered a work-in-progress and reflect the first run of the course.  The course is anticipated to run again in the Spring of 2012.

Additional Labs from the Course

EE49 Lab 1: Source Coding Lab: Cosine Transform (DCT), sample quantization, and Huffman coding

EE49 Lab 2: Introduction to Digital Communication Lab: UART Communication, Sync, and Channel Correct...

EE49 Lab 3: Introduction to Modulation: BPSK & QPSK

EE49 Lab 4: Introduction to Demodulation and Decoding: BPSK & QPSK

EE49 Lab 5: Building a Wireless Packet Transmitter and Receiver

Required Components

LabVIEW Full or Pro

LabVIEW Modulaiton Toolkit

Two NI USRP-2920

Experiment

The PDF laboratory procedure is attached along with starting-point VI's for the students.

LaTeX source is included so that it can be customized by the instructor.

Contact Information

Author: Dr. Sachin Katti, Jeff Mehlman, Aditya Gudipati

School/University: Stanford University

[Yu-Cheng_Lai]

Great material for learning digital communication.

I would like to know if there any answer/solution for these exercises.

Or shall I setup an USRP to verify the correctness of my own solution?

[EvangelosK]

Please find the updated version of Demodulation VIs in the attachments.

The TX_lab4 and RX_lab4 vi's are updated on Labview 2012 to support the NI USRP 1.2 drivers as their previous versions may appear as broken in this case.

Thank you.

[Tomielic]

Hi,

great lab.  Just did it.  I am modifying it to use a 256 bit PN gold code instead of the 31 bit code.  I can't see into some modules but, I just removed the 31 bits in the transmitter that I beleive are in indicies 6-37? becasuse of the zero padding?  Anyways I dont understand how then you remove the padding?  Is the 31 length hard coded anywhere else in RX/TX?   I am locking on my new 256 bit code, but the message is not following it correctly so I am unsuccessful right now.  any help thanks.

[js7777]

Whats the password to the sub vi’s, cant open any it just says password protected. Thanks.