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MSK vs GMSK Modulation Comparison

This document compares the Minimum Shift Keying (MSK) and Gaussian Minimum Shift Keying (GMSK) modulation schemes. GMSK uses a Gaussian pulse shaping filter to smooth the phase transitions between symbols, improving bandwidth efficiency. The document outlines steps to run a MATLAB simulation that models both modulators and applies additive white Gaussian noise. It then describes the functions of various blocks in the model and how the results are visualized. Specifically, the eye diagrams in the Discrete-Time Eye Diagram Scope blocks show the similarity between clean GMSK and MSK signals, but the increased paths for longer Gaussian pulses, demonstrating GMSK's dependence on previous symbols.

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Vaibhav Tripathi
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370 views2 pages

MSK vs GMSK Modulation Comparison

This document compares the Minimum Shift Keying (MSK) and Gaussian Minimum Shift Keying (GMSK) modulation schemes. GMSK uses a Gaussian pulse shaping filter to smooth the phase transitions between symbols, improving bandwidth efficiency. The document outlines steps to run a MATLAB simulation that models both modulators and applies additive white Gaussian noise. It then describes the functions of various blocks in the model and how the results are visualized. Specifically, the eye diagrams in the Discrete-Time Eye Diagram Scope blocks show the similarity between clean GMSK and MSK signals, but the increased paths for longer Gaussian pulses, demonstrating GMSK's dependence on previous symbols.

Uploaded by

Vaibhav Tripathi
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Comparing between MSK and GMSK

Comparing between MSK and GMSK


Objective: to investigate and compare Gaussian Minimum Shift Keying (GMSK) and
Minimum Shift Keying (MSK) modulation schemes.
Tool: MATLAB simulation program, Simulink with communication and DSP blocksets.
Procedure:
1. Start MATLAB by double-clicking the MATLAB icon

2. Type commgmskvsmsk at the MATLAB prompt to open the commgmskvsmsk


model. Then save the model as xx_msk in the directory where you keep your
work files. (xx could be your first name)
Question 1. What is MSK? What is GMSK? What are the usages of GMSK?
Question 2. Briefly explain the functions of following blocks in the model.

Random Integer block,


Unipolar to Bipolar Converter block
GMSK Modulator Baseband block
MSK Modulator Baseband block
AWGN Channel block
Discrete-Time Eye Diagram Scope block
Discrete-Time Signal Trajectory Scope block

Ya Bao

Page 1

Comparing between MSK and GMSK

Visible Results of the Model


The model illustrate the difference between the two modulation schemes. The DiscreteTime Eye Diagram Scope blocks show the eye diagrams of GMSK and MSK signals
corrupted by noise. The eye diagrams show the similarity between the GMSK and MSK
signals when you set the Pulse length of the GMSK Modulator Baseband block to 1.
Setting the Pulse length to 3 or 5 enables you to view the difference that a partial
response modulation can have on the eye diagram. The number of paths increases
demonstrating that the CPM waveform depends on values of the previous symbols as
well as the present symbol. You can change the pulse length to 2 or 4, but you should
change the Phase offset to pi/4 for a better view of the modulated signal. In order to more
clearly view the Gaussian pulse shape, you must use GMSK vs. MSK Demo scopes that
enable you to view the phase of the signal, as described in CPM Phase Tree Demo on
page 3-11
Analysis and conclusions

Ya Bao

Page 2

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