辅导案例-EGB342-Assignment 2

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EGB342 Assignment 2B (25%)
Released: Tuesday, 24th September
Due: Sunday 20th October, 11:59pm (Week 12)
Group Assignment - Group of 3 students
Congratulations! Fraser Island tourism manager Natalie has just confirmed that the commis-
sioning of the communication link between Fraser Island and the mainland was a success. With
the easy access routes to the Island and the commissioning of new communication infrastruc-
ture, Fraser Island has become one of the most sought-after holiday destinations. However, the
Fraser Island tourism board has found that the existing infrastructure is not sufficient to deal
with the increase in tourist numbers. Therefore, they have commissioned your team to design
and test a wireless communications solution to the island.
As you will see from the following tasks, each team will be required to wirelessly send informa-
tion to the mainland. This involves recording an audio message, quantizing, designing a source
encoder and a decoder, transmiting digital data using band pass modulation and implementing
appropriate receivers.
*Reminder* Read the entire document before attempting the questions
Detailed instructions on report format and submission guidelines are provided at the end of
this document. All solutions must be implemented in MATLAB unless instructed otherwise.
The submitted report must be a standalone document that can be read without reference to
this brief, or the submitted code.
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Preliminary Instructions
Download all files to be used in Assignment 2B from blackboard and place them into one
working directory. Please also unzip the contents of Assignment2B.zip into this directory.
There are 3 files contained within Assignment2B.zip:
1. EGB342 A2B Template.m - implement your code solution in this file.
2. initialise.m - generate the data used in this assignment.
3. RecordAudio.p - called by initialise.m.
Workspace Preparation
Open initialise.m with MATLAB and read its instructions. Proceed to insert your group
number and student IDs into the script and generate your data for this assignment. First, you
need to record an emergency audio message using an external microphone or the computer
microphone. Run the initialise.m script and record the following message when prompted.
“Emergency! Emergency! Please vacate the beach immediately..!”
This will record and store 5 seconds of audio into A2BData.mat.
Load A2BData.mat to obtain the recorded audio sample (audio sample) and listen and verify
the quality of your recording using the following command:
Fs=8000;
sound(audio sample,Fs);
If the audio is not recorded properly run the initialise.m script and record the audio again.
Overview
As Wireless spectrum is limited, it is important to improve the spectral efficiency of the trans-
mission.
Figure 1: Process of Converting Analogue Signals to Binary Data
Figure 1 shows the process of converting analogue signal, xc(t), to binary data, c[n]. Sampled
signal, x[n] = xc(nT ) is quantized to get xˆ[n] before binary encoding. Binary encoder could be
pulse coded modulation (PCM) or a suitable source encoder such as Huffman code.
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PCM encoded audio does not use any form of compression. The sampling rate of PCM can
vary between 8000 to 192 000 samples per second and word length of each sample can vary
from 8 to 24 bits. The WAV recording file types contain the unprocessed PCM data. However,
for Part 1 we will initially use a sampling rate of 8000 and a word length of 3 bits.
Huffman code is a lossless code. Lossless coding algorithms allow the exact reconstruction of the
original source data from the compressed data. Lossless coding can provide a reduction in bit
rate compared to the original data, when the original signal contains dependencies or statistical
properties that can be exploited for data compaction. It is also referred to as noiseless coding or
entropy coding. Lossless coding can only be employed for discrete-amplitude and discrete-time
signals.
Your first task is to generate an appropriate Huffman code to encode the recorded audio mes-
sage.
Part 1 – Creating a Source Encoder/Decoder for Audio
Messages
1.1 Load A2BData.mat to obtain the recorded audio sample (audio sample). Use the sam-
pling frequency (Fs) to create a time vector and plot audio sample with correct time
scale.
1.2 Quantize the audio sample using a uniform quantizer with 8 levels. If the number of
levels is L and the step size is ∆, quantized audio samples can be obtained from:
quantized audio =

normalised audio sample + 1


×∆ + ∆
2
− 1
where normalised audio sample = audio sample/max(abs(audio sample))
1.3 Plot and compare the normalised audio sample and quantized audio. Play and in-
spect the quantized sample for intelligibility. You can use the command sound(audio,Fs)
to play audio samples.
1.4 Generate and tabulate the frequency and probability table for the quantized audio sample
values.
1.5 Use this table to construct a Huffman code to transmit the quantized audio sample.
Generate and tabulate the code dictionary. Show your working in the report.
1.6 Write a MATLAB procedures to encode (audio enc) and decode (audio deco) the quan-
tized audio sample and plot the output of the Huffman decoder and compare that with
the quantized audio sample (normalised audio sample).
1.7 Calculate the following for your source encoding and decoding process:
• Entropy and entropy rate of the quantized audio.
• Average codeword length and the efficiency of the code.
• The rate at the output of the Huffman encoder in bits/s.
• The rate required in bits/s if Huffman encoding is not used (PCM output).
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1.8 Investigate and report on the effects of quantization levels and the sampling rate on the
intelligibility of the recorded audio and the complexity of the system. Assume that the
Huffman encoder and decoder are used for this task.
1.9 Research and describe the details of one of the modern speech encoders.
Part 2 – Testing the Wireless Channel
You have been allocated a 25 kHz channel centred around 96 kHz, and therefore, the carrier
frequency (fc) of your transmission needs to be as such. Null-to-Null bandwidth of your mod-
ulated signal should not exceed 24 kHz. In this section you will test the suitability of binary
phase shift keying (BPSK) to transmit the digital audio messages.
Set up your simulation to transmit binary messages from Part 1, with 128 samples (i.e.
NumPts=128) for each transmitted symbol (each bit).
2.1 Define the variable Nb to be the number of bits in your simulation sequence. Set this
variable to length of the binary message created earlier (audio enc).
2.2 Initialise the variables for the carrier frequency (fc), symbol rate (Rs), number of samples
per symbol (Ns), and the sampling rate (fs). Store these values as fc, Rs, NumPts, and
fs respectively. The sampling rate is the symbol rate times the number of samples per
symbol.
2.3 Create a time vector for your signal and store this as t. Additionally, create a frequency
vector for the corresponding FFT and store this as f.
2.4 Create a cosine wave at 96kHz using the cos function (c = cos (2pifct)). The peak
magnitude of the carrier waveform at the transmitter is 1V.
2.5 Convert the binary data to bipolar data and store as x.
2.6 Oversample the bipolar binary data sequence so that each bit is Ns samples in length and
store it as m. You can do this quickly with the kron function, i.e., kron(x, ones(1,Ns)).
Your resulting vector should have a length of Ns×Nb samples. Multiply the oversampled
binary data, m with the carrier waveform c. Store this signal in the variable y. Plot the
first 500µs of this transmission. Comment on your observations.
2.7 Plot the spectrum of y. What is the bandwidth of the signal (the width of the main lobe)?
Does this satisfy the requirements described above. What are the two major issues in
transmitting this signal given the channel constraints?
2.8 Assuming no channel distortions recover the bit sequence using a correlation receiver1.
This can be easily implemented using the reshape and sum functions. Perform this by
multiplying the signal vector again with the cosine wave, and reshape the result to a
Ns × Nb matrix. Summing each column will result in the correlation receiver output.
Normalise the magnitudes by dividing by the number of samples. Recover the binary
data (bipolar) from these samples. Use a single line of MATLAB code to calculate the
bit error. Comment on the calculated result.
1Though mathematically identical to a matched filter, the algorithm described here better matches that of
a correlation receiver.
4
2.9 Convert the received binary bipolar data back to binary format and recover the audio
message using the Huffman decoder constructed in Part 1.
2.10 If the peak magnitude of the carrier at the receiver is 60 µV, estimate the total power
loss in dB due to wireless propagation.
2.11 Re-transmit your BPSK signal with a carrier frequency of 196 kHz. How does varying
fc affect your signal and its spectrum? What are the bandwidth requirements and the
achievable data rates in this case?
2.12 Lower the sampling rate, NumPts, to 64 samples/symbols (with a 96 kHz carrier). How
does varying fs affect your signal and its spectrum? What are the bandwidth requirements
for this sampling rates? You will need to plot the spectrum with an appropriate frequency
range. What is the data rates, and how long would it take to transmit the audio message?
2.13 Simulate and plot the bit error rate performance of the above modulation in the Eb/N0
range 0dB to 12dB. Here:
snr (dB) = EbNo (dB) + 10*log10(2) - 10*log10(NumPts)
Compare the simulated error rate performance with the theoretical bit error rate per-
formance of BPSK. Theoretical bit-error-rate probability of BPSK modulation is given
by;
Pb = Q
(√
2Eb
N0
)
2.14 Mean Opinion Score (MOS) is often used for subjective evaluation of audio quality (in-
telligibility) which listeners rate the quality of the test signal using a five-point numerical
scale shown below.
Rating Speech Quality Level of Distortion
5 Excellent Imperceptible
4 Good Just perceptible, but not annoying
3 Fair Perceptible and slightly annoying
2 Poor Annoying, but not objectionable
1 Bad Very annoying and objectionable
Transmit your Huffman coded message through a channel with Eb/N0 from 0dB, to 12dB
(increment Eb/N0 by 1 dB in each step) and assess the audio quality according to the
MOS score given above. Each member of the group should assess the audio quality
independently and tabulate the results for each of the above Eb/N0 values.
Assuming minimum MOS required is 3, decide the minimum acceptable Eb/N0 required
at the receiver.
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2.15 Assess (each member) and tabulate the received voice quality at Eb/N0 = 0 to 12dB
(increment Eb/N0 by 1 dB in each step) for L = 4 and L = 256 and decide the minimum
acceptable Eb/N0 required at the receiver. Comment on your observations. For this step
you can use following steps to encode and decode using Huffman codes:
• dict = huffmandict(symbol alphabet,symbol probability); Code dictionary
• encoded bits = huffmanenco(quantized audio,dict); Encode
• decoded symbols = huffmandeco(encoded bits,dict); Decode
Part 3 – Performance of Multi-Level Modulation Schemes
While the Fraser Island tourism manager is reviewing your solutions to the previous tasks of
establishing a wireless link, she is investigating the possibility of transmitting the live security
video feed using a wireless link. As video signals from number of security cameras from around
the island is multiplexed before the transmission, the data rate of the wireless channel varies.
Fraser Island tourism was able to secure a 5.25 MHz spectrum around 700 MHz range from the
Australian Communications and Media Authority (ACMA). In this task you need to choose an
appropriate modulation scheme to transmit the video feed with the given data rate using the
allocated radio spectrum (5.25 MHz).
Your team is also tasked to test the performance of a modulation scheme chosen for this
purpose. Raised cosine pulse shaping is assume. You can use built-in MATLAB functions for
this task (useful MATLAB functions: qammod, awgn, scatterplot ). Load A2BData.mat to
obtain the data rate allocated to your team. The data rate in Mb/s is stored in the variable
called ChannelDataRate and the Roll-Off factor of the raised cosine filter, r is stored in the
variable called RollOffFactor.
1. Choose a suitable M -QAM scheme to transmit the data at the given rate, draw the
corresponding constellation diagram, and label the constellation points using appropriate
bit sequences. Justify your selections and constellation point labelling.
2. What is the actual bandwidth required to transmit the given video data using this mod-
ulation scheme and raised cosine pulse shaping?
3. Simulate and plot the bit error rate performance of the modulation scheme in a Eb/N0
range which is suitable to observe the bit-error-rate up to 10−6. Signal-to-Noise Ratio
(SNR) of the signal can be calculated using the following expression. Hint: You can use
base-band simulation without the carrier.
snr = EbNo + 10*log10(k) - 10*log10(NumPts);
Here k is the number of bits per modulated symbol. For based band simulation NumPts=1.
4. Compare the simulated performance to the theoretical error probability, and comment on
the results.
5. Plot the scatter plot of the received noisy signal for Eb/No values of 0dB, 5dB, 15dB,
25dB and 35dB and comment on your observations.
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6. If the maximum acceptable bit-error rate at the receiver is 10−5, calculate the minimum
transmit power required at the Fraser Island transmitter station. Use the following pa-
rameters of the wireless link,
• Transmit antenna gain = 5 dB and Receiver antenna gain = 5 dB
• Cable loss at the transmitter = 2 dB and Cable loss at the receiver = 2 dB
• Path-loss of the wireless link = 80 dB
• Noise power spectral density at the receiver = 10−12 W/Hz
The relationship between received power, Prx and the transmitted power, Ptx is given as;
Prx [dB] = Ptx [dB] + Gains [dB]− Losses [dB]
[Hint: First calculate the Prx using the minimum Eb/N0 required to achieve the bit error
rate of 10−5 based on the modulation scheme you selected.]
7. Describe the advantages and disadvantages of higher order modulation schemes.
Reflection (Mandatory)
A reflection is to be written and appended to the end of your report. Include a short discussion
(150 to 200 words) that addresses problems encountered, and things that you would have done
differently. Identify what concepts this assignment has reinforced, and areas where you can
improve. This section is mandatory and the assignment is regarded as incomplete if absent.
Academic Integrity Declaration and Group Dynamics -
Individual (Mandatory)
Each group member must individually complete the ‘Academic Integrity Declaration and Group
Dynamics’ online form using the provided link on Blackboard. Individual marks will be
withheld if this is not completed, or if the declaration is not agreed to. In the group
dynamics portion, allocate the percentage contribution of each group member. If you wish, you
may add additional text and request the teaching team review member contribution. If you
experience issues with group members before the due date, please contact the teaching team
via email. If your issues are in hindsight, please give details here.
Interview (Mandatory if requested)
Interviews will take place (at the discretion of the teaching team) to assess the conceptual
understanding. This will be a casual discussion. These interviews are compulsory and grades
are withheld until they are completed. Marks may be deducted for poor demonstration of
content/assignment knowledge. These interviews will only be for selected groups, and you will
be notified if you need to take part in an interview.
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Presentation Standards
This assignment includes elements of written and coding assessment. You are expected to work
as a group. Each group is expected to generate and submit one assignment report and one set
of MATLAB code. Marks are based on how easily and effectively ideas are articulated to the
reader.
The teaching team has put together some things to consider -
The Report Component
An outstanding report demonstrates knowledge and understanding of the subject area. It
communicates ideas clearly and logically with a combination of visual, mathematical and code
assets. It demonstrates insight about the underlying concepts and their implications within
telecommunications and signal analysis. Verbose responses, or correct information not articu-
lated clearly, will attract deductions.
Remember that you are writing to inform.
Mathematical working shows a logical procedure (or justification) for the final solutions i.e. All
non-trivial steps are included. It can be typed or handwritten but must be legible and easily
followed.
Code snippets used in-text should only contain relevant lines of code and should rarely have
more than five lines in a snippet.
Present the report so that it can be understood without reference to the assignment brief. Any
figures or code referenced within the code should be no more than one page turn away. Avoid
the use of “see appendix” and “refer to .m file”. Document flow and coherency is to be priori-
tised. Reports that are difficult to navigate are marked poorly in this criteria.
Write the report assuming that the reader only knows concepts from 1st year
engineering and does not have access to your .m file/s.
Include a title page that states the unit name, unit code, assignment number, your name(s)
and student number(s). Do not include a table of contents, list of figures, nor a list of
tables. Convert the report to the PDF file format before submission. This ensures document
typesetting is preserved across different computers running different operating systems.
The Code Component
The submitted code needs to be executable (in MATLAB R2016b or later) and without run-
time error. If an error is encountered at execution, your assignment will only be marked until
the error. No error correction will be made to make your code ‘run’. Coding for this assignment
should remain within one (provided) file (unless otherwise explicitly instructed). Only include
a separate .m file if absolutely necessary.
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Code should be fully commented to describe intent. Comments should contain enough informa-
tion to understand the process without referring to the report. Quality comments encapsulate
your understanding of the topic.
* You may use the code provided in the weekly tutorials to check your solutions, however you
are expected to generate your own code for your assignment. Submitting supplied .p code as
your own work constitutes academic misconduct and will be considered a run-time error. *
Acknowledgement
Front page image from
https://www.frasercoastchronicle.com.au/news/optus-invest-6m-improving-reception/3178731/ .
Submission Check-list
Submission deadline is on the Sunday, 20th October 2019, 11:59 pm. This will be a hard
deadline and late submission penalties will apply. As per QUT policy, late assignments receive
0 marks.
The report, in PDF format, submitted to Turnitin via the Blackboard link (1/3)
A .zip file, submitted directly to QUT Blackboard via the provided link, that contains
(2/3) -
• EGB342 A2B Template.m with your name and ID
• A2BData.mat - [audio sample should be related to task 1.4]
• Functions that are written as a result of explicit assignment instruction
• Any other MATLAB scripts you have developed
Submissions have been re-downloaded from submission portals and run as-is to confirm
successful upload.
Completed Academic Integrity Declaration on-line form (3/3)
Submission FAQ
⇒ You do not need to assign your submission with a special name. Blackboard assigns
unique IDs to all submissions. The submission link is accessible through:
EGB342 19se2 → Assessment → Assignment 2B → Assignment 2B: Submis-
sion.
⇒ You may submit as many times as you like before the deadline. New submissions overwrite
old submissions. Only the latest submission is recorded and marked. Upload in-progress
versions so there is something to mark if your final submission is late.
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⇒ All documents can be reviewed after submission and thus it is your responsibility to verify
that the uploaded documents are not corrupt. Corrupt files are treated as incomplete
assignments.
⇒ Be aware that the electronic time stamp is placed only after all files have uploaded.
Blackboard may experience high traffic or your connection may fail unexpectedly. Begin
your final upload at least an hour before the deadline.
Hardship
If you experience a hardship which affects your ability to complete, or contribute to, this
assignment, please contact the teaching team as soon as it occurs.
QUT also offers counselling services if required.
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EGB342 Assignment 2B: Group 2019



1
Criteria Standards
7+ 7 6 5 4 3 2/1
CR1 - 50% weighting
Theoretical
understanding
Key Milestones
- Huffman
encoding and
Decoding
- Implementing
and recovering
BPSK
- M-QAM
performance
Demonstrates understanding of the
mathematical concepts
underpinning this assignment
beyond the expected ‘7’ level.
Explanations and justifications are
unambiguous, accurate and logical.
Graphical and mathematical tools
are used masterfully to convey
knowledge of all topics. Uses
appropriate terminology.
Has no conceptual errors, but one
minor technical/numerical error
may exist. Discusses all required
concepts and shows evidence of
further research.
Demonstrates in-depth
understanding of the
fundamental concepts in this
assignment. Explanations and
justifications are generally
clear, accurate and logical.
Graphical and mathematical
tools are used fittingly to
convey knowledge of all
topics. Uses appropriate
terminology.
Has no conceptual errors, but
one minor
technical/numerical error may
exist. Discusses all required
concepts.
Demonstrates strong
understanding of the
fundamental concepts in this
assignment. Explanations
and justifications are
generally accurate and
logical. Graphical and
mathematical tools are used
satisfactorily to convey
knowledge of all topics. Uses
appropriate terminology.
Has no conceptual errors, but
minor technical/numerical
errors exist. Discusses all
required concepts.
Demonstrates sound
understanding of the
fundamental concepts in this
assignment. Explanations and
justifications are generally
accurate and logical. Graphical
and mathematical tools are
used satisfactorily to convey
knowledge of most topics.
Uses appropriate key
terminology.
One minor conceptual error
and no more than two
technical/numerical errors may
exist. Discusses all key
concepts.
Demonstrates rudimentary
understanding of the
fundamental concepts in this
assignment. Explanations
and justifications are
generally accurate and
logical but are sometimes
unclear. Graphical and
mathematical tools are used
adequately to convey
knowledge of most topics.
Uses appropriate key
terminology.
Only minor conceptual,
technical or numerical errors
exist. Discusses most key
concepts.
Conceptual
understanding is
not demonstrated
explicitly
OR
Major conceptual
error
OR
Discussion does
not demonstrate
understanding of
the expected ‘4’
level.
Incorrect
interpretation/s
of underlying
concepts i.e.
Multiple major
conceptual
errors. Does
not recognise
basic errors
when discussing
generated
diagrams.
CR2 - 20% weighting
Effective written
communication

Key Milestones
- Informative
- Easy to read
- Clearly explained core
ideas
- Reflection demonstrates
intended learning
outcomes

Professional format, insightful, core
technical ideas are clearly,
accurately and succinctly conveyed.
The report is very easy to read, and
has been written to inform. Only
relevant code included in snippets.
Figures demonstrate intended
point excellently. Referencing is
present, and has been done
correctly (IEEE). Reflection shows
all learning outcomes were
reached.
Professional format, core
technical ideas are clearly and
accurately conveyed. The
report is easy to read, and has
been written to inform.
Mostly relevant code included
in snippets. Figures
demonstrate intended point
very well. Reflection shows all
learning outcomes were
reached.
Professional format, technical
ideas are clearly conveyed,
one minor inaccuracy. The
report is informative and easy
to read. Mostly relevant
code included in snippets.
Figures demonstrate
intended point well.
Reflection shows most
learning outcomes were
reached.
Report format is adequate but
missing some coherence in its
structure. The report is difficult
to read in one or two sections.
Consistently irrelevant code
included in snippets. Figures
demonstrate intended point
satisfactorily. Reflection shows
some learning outcomes were
reached.
Report format is missing
several critical explanations.
The report is difficult to read
in several parts. Large
amounts of irrelevant code
included. Figures
demonstrate intended
points adequately. Little
evidence of reflective
thinking.
Report formatting
was attempted.
Contains little, or
vague, discussion
and lacks
cohesion. Largely a
code and figure
dump. No
evidence of
reflective thinking.
The report has
little or no
structure. No
evidence of
reflective
thinking.
CR3 - 30% weighting
Application using Coding
Key Milestones – For a 7 in this criteria, all milestones must be satisfactorily reached; For a 6, most must be satisfactorily reached, and so on.
• Correct individual-question outputs as per solution-script options
Code appears to give correct outputs if widely-varying solutions are possible
• Code is optimised (i.e. makes use of vectorisation where appropriate)
• Comments are effectively used to describe the code
• No runtime errors
• Uses functions that are within the scope of the assignment
• Code achieves desired output/s on completion

Large sections of code incomplete
OR
Multiple runtime errors
For moderation of overall marks: At the discretion of the teaching team, your group may be selected to attend an interview if the teaching team require clarification about how the group arrived at their solutions, or how individuals
contributed to the overall solution. If selected, you will be notified and given details of the location and time of the interview.
Oral interview Demonstrated knowledge is consistent with submitted report and code. No moderation of marks. Demonstrates knowledge
noticeably below the
standard of the submitted
report and code. Individual
marks may be moderated
down up to 20%.
Demonstrates knowledge significantly
below the standard of the submitted
report and code OR Does not attend
interview. Individual marks may be
moderated down up to 100%.

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