Binary Phase Shift Keying (BPSK)
Introduction
In this exercise, you will design a BPSK detector to process
modulated data contained in the file bpskdata.mat
Textbook References
Mary QAM: Section 5.3 (pp. 238  260),
discretetime realizations: Section 5.3.2 (pp. 256  260),
partial response pulse shapes: Section A.2 (pp. 682  687).
Specifications

normalized sample rate: 
8 samples/bit 
normalized carrier frequency: 
0.25 cycles/sample 
carrier phase: 
0 degrees 
average energy: 
1 
pulse shape: 
SRRC (50% excess bandwidth, span = 12 symbols) 
symbol clock offset: 
0 
input file 
bpskdata.mat 
input message length: 
154 symbols (154 bits or 22 ASCII characters) 

Preliminary Design
Design the Detector
Design the detector, shown below, using blocks from the Simulink, DSP System,
and Communications System Toolboxes.
Test the Detector Design
You should test the detector you designed by constructing a modulator to produce
a test signal.
The following procedure steps you through this design process:
 Design the modulator shown below to meet the above specifications except
make the input the four symbol sequence 1 0 0 1.

Connect the output of your modulator to the input of your detector.

Connect the output of your detector to a To Workspace block
(be sure to open the Properties Dialog Window and set the Save format to matrix)
and a Scope block.

Set the simulation parameters as follows:
Start Time: 
0.0 
Stop Time: 
(12+4)*81 
Solver Options
Type: 
Fixedstep 
Solver: 
discrete (no continuous states) 
Fixed step size: 
auto 
Tasking and sample time options
Periodic sample time constraint: 
Unconstrained 
Tasking mode for periodic sample times: 
SingleTasking 
Note: the stop time is computed as follows: 12 = 2*(span/2) [the delay of the
pulse shaping filter plus the delay of the matched filter];
4 = the number of data symbols;
8 = the number of samples/symbol.
We subtract because the start time is t = 0.0.
 Run the simulation and plot the demodulator input and the matched filter
output on the same set of axes.
The simulation produces 18 downsampled matched filter outputs 
the last four correspond to the sequence 1 0 0 1.
Check the values in the workspace to see if they agree with input
sequence 1 0 0 1.

Adjust the offset of the Downsample block to obtain the proper
values.
Exercise

Replace the modulator blocks with the From File block and set the
Filename to bpskdata.mat and the sample time to 1.

Set the simulation parameters as follows:
Start Time: 
0.0 
Stop Time: 
(12+154)*81 
Solver Options
Type: 
Fixedstep 
Solver: 
discrete (no continuous states) 
Fixed step size: 
auto 
Tasking and sample time options
Periodic sample time constraint: 
Unconstrained 
Tasking mode for periodic sample times: 
SingleTasking 

Run the simulation.

The detector produces 166 symbol estimates.
The last 154 of these correspond to 22 7bit ASCII characters.
Determine the message using either your Matlab script or an
ASCII Table.

Plot the eye diagram and signal space projections.