Adam M Hess
Digital Communications

Soft Acoustic Modem

Context:

This project was completed as a part of the graduate level Digital Communication course taught by Dr. Xiaohua(Edward) Li. This was a team project (credited in the presentation powerpoint) Most of my contributions were the creation of the presentation and large chunks of the receiver code (namely the Viterbi Decoder) and the modulation scheme.

Summary:

The goal of this project was to design a Soft Acoustic Modem (SAM) digital communication system to transmit from one computer's speaker to another computer's microphone. This was to be designed and implemented in Matlab.

Included is a presentation of the project and the Matlab code used to implement the project.
When you run the code in Matlab there are onscreen prompts to syncronize the transmitter and receiver.

Modem Specifications
Transmission rate: 200 bits/sec (100 bit/s per I and Q channels)
Carrier frequency: 100 Hz
Root-raised Cosine filter roll off factor: 0.35
Quadrature Phase Shift Keying (QPSK)
Convolutional Encoding
Viterbi Algorithm
Differential Encoding (eliminates need for carrier signal synchronization)

Results:

Presentation
Transmitter Code
Receiver Code