ELE4606 Assignments 2014 PDF

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Assessments

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3. Assessments 3.1 Assessment policies 3.1.1 Policy on late assessments The University policy on Assignment extensions is detailed in section 5.6.3.4 of the Academic Regulations, which are published in the University Calendar. The penalty for late submission in the absence of extenuating circumstances is the loss of 5% of the total mark per working day late. In normal circumstances it would be expected that students apply in advance for extension of assignment due dates. Applications should be in writing, and accompanied by appropriate documentary evidence of extenuating circumstances.

3.1.2 Policy on academic misconduct Cheating in examinations and plagiarism of assignment work are both examples of academic misconduct. These are defined in detail in section 5.1 of the Academic Regulations which are published in the University Calendar. Plagiarism is presenting another persons work as if it were your own. For this reason assignment cover sheets include a declaration by the student that the attached submission is entirely his own work. No assessment will be accepted and graded unless this declaration is properly completed. Breaches of examination and assessment regulations will be dealt with as per section 5.10 of the Academic Regulations.

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ELE4606 – Communication systems

3.2 Assessment Assignment 1 Description Assignment 1

Marks out of

Wtg (%)

Due date

200

20%

29 August 2014

This assessment is intended to give you practice in applying some of the more difficult concepts in study book 1, so that you can receive some feedback. When completing this assessment, it is not necessary to reproduce proofs or text from the study materials. Any equation from the study books may be used as a starting point, as long as you give the reference to show where it came from. The problems are intended to be quite short, so that it should be possible to answer each in one to two pages of working. You are reminded that all the assessments in this course should be entirely your own work. You must not collaborate with other students, or copy material from the Internet. Copying all or part of an assessment from another student, or from the web, is unacceptable. Plagiarism may result in loss of marks, or other penalties as determined by the Academic Misconduct Policy: http://policy.usq.edu.au/documents.php?id=14132PL It is strongly suggested that you review the following pages: http://www.usq.edu.au/current-students/assessment/assignments/referencing-plagiarism http://www.usq.edu.au/current-students/assessment/assignments/submitting Please submit your assignments electronically via EASE.

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Problem 1

Figure 1: Question 1 – Receiver Block Diagram Figure 1 depicts a block diagram of the front end of a communication receiver. The noise characteristics of the critical receiver components are as follows: Antenna noise temperature 29 K RF Bandpass filter passband loss 0.2 dB, physical temperature 30 Co Low Noise Amplifier gain 25 dB, noise figure 0.5 dB RF Amplifier gain 23 dB, noise figur 3.3 dB The noise performance of subsequent components should have virtually no effect on the overall noise performance. Therefore, these details are not specified. Calculate: (a)

(i)

The overall noise temperature of the receiver

(ii)

The overall noise factor

(iii)

The overall noise figure in dB

(iv)

The system noise temperature 40 marks

(b) If the receiver equivalent noise bandwidth is 65 MHz, and the signal to strength at the antenna connection to the RF band pass filter is 7pW (710−12W), calculate the signal to noise ratio in dB at the receiver output to the demodulator. 10 marks

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ELE4606 – Communication systems

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Problem 2 Each student will use a unique sequence of 8 dibits. The sequence is generated by converting the last 5 digits of the student ID into a binary format. If the 5 digit number is larger than 65536 this will lead to more than 16 bits. In this case additional leading bits should be ignored. The windows calculator or the ”dec2bin(’ID’,16)” function in MATLAB, can be used to do the conversion. Assume that this sequence, continuously repeated, is applied to the QPSK modulator shown in Figure 2. The corresponding constellation is shown in Figure 3. Both bits of each dibit are presented simultaneously to the product modulators and these levels are maintained for the duration of the symbol time T s. This is coherent QPSK, with exactly two cycles of carrier occurring during each symbol. The carrier frequency is 1600H z.

Figure 2: QPSK modulator and demodulator (all components are ideal)

Tasks i.

Write a computer simulation to calculate the waveforms at points A, B, C, D, E, F, G, H, I on the modulator/demodulator block diagrams (Figure 1) and print or plot these one beneath the other in their correct time relationship. Ensure that they are labelled unambiguously with the appropriate letter. In the case of the integrator outputs (H and I) the instantaneous waveforms are required. These will resemble figure 2.8 in Study Book 1. NB: You may not use a commercial simulation package, or a MATLAB toolbox.

ii. Use a Fast Fourier Transform (FFT) algorithm to calculate the print or plot the frequency spectrum of the repeated transmitted modulated carrier E. Use as many repetitions of the waveform as possible.

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Assessments

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Figure 3: Constellation NB: You may obtain the FFT code from another source or use the MATLAB fft function.

Presentation The computer program is required to be properly modularised and commented. A code listing is required to demonstrate this, which should be an appendix to your report. The report should be properly structured and organised, e.g. as required by the Faculty of Engineering & Surveying Communications policy.

Allocation of marks Complete timing diagram with waveforms A to I inclusive

80

Spectrum

30

Discussion, presentation and programme documentation

40

Sub-total

150

NB: the discussion should demonstrate that you can interpret the waveforms and spectrum.

Advice and suggestions Any high level programming language is acceptable, providing it has graphing facilities. 1. MATLAB is recommended. You may not use a simulation package, or a MATLAB toolbox. 2. It will be necessary to sample all waveforms at regular instants of time. It will be easier to compute the spectrum if the number of samples per cycle is a power of two. 3. The carrier frequency is 1600 Hz. There are two cycles of carrier per symbol, so the baud rate (symbol rate) is 800 symbols per second. The duration of each symbol, or segment of carrier, is therefore 1.25 ms. Any waveforms which do not comply with these parameters must be incorrect.

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ELE4606 – Communication systems

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4. To check and calibrate the FFT algorithm you are using, supply it with a long duration 1600 Hz sinusoidal signal, and observe the output. This should allow you to check the frequency scale. 5. The spectrum of the modulator output should show the frequency range from DC to 6400 Hz. You may present additional plots with different frequency scales if you think it necessary. 6. From the nature of the signal at the modulator output you should have some idea what to expect in the frequency spectrum. Ask yourself: ●

What is the repetition rate of the time waveforms, and what effect will this produce in the frequency domain?

●

What is the frequency spectrum of the rectangular pulses applied to the product modulators, and how will this affect the spectrum of the modulator output? Remember that a product modulator produces a double sideband suppressed carrier output.

7. You may obtain FFT code from another source or use the MATLAB fft function. All other code should be entirely your own work. You must not collaborate with any other student. ________________ End of Assignment

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Assessments

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Assignment 2 Description Assignment 2

Marks out of

Wtg (%)

Due date

200

20%

03 October 2014

This assignment is an individual assignment. Copying all or part of an assessment from another student, or from the web, is unacceptable. Plagiarism may result in loss of marks, or other penalties as determined by the Academic Misconduct Policy: http://policy.usq.edu.au/documents.php?id=14132PL It is strongly suggested that you review the following pages: http://www.usq.edu.au/current-students/assessment/assignments/referencing-plagiarism http://www.usq.edu.au/current-students/assessment/assignments/submitting Please submit your assignments electronically via EASE.

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ELE4606 – Communication systems

Problem Cellular telephony has forever changed the way people communicate with one another, being one of those exciting technologies that has directly and significantly influenced our everyday life. The characteristics of wireless signal changes as it travels from the transmitter antenna to the receiver antenna. These characteristics depend upon the distance between the two antennas, the path(s) taken by the signal, and the environment (buildings and other objects) around the path. The profile of received signal can be obtained from that of the transmitted signal if we have a model of the medium between the two. This model of the medium is called channel modeling. Rayleigh fading is a statistical model for the effect of a propagation environment on a radio signal, such as that used by wireless devices. Rayleigh fading is a reasonable model when there are many objects in the environment that scatter the radio signal before it arrives at the receiver. Rayleigh fading is exhibited by the assumption that the real and imaginary parts of the response are modelled by independent and identically distributed zero-mean Gaussian processes so that the amplitude of the response is the sum of two such processes. Question 1 Random variable R is Rayleigh distributed if R Y : N (0,

2

X 2 Y 2 , where X : N (0,

2

) and

) are independent normal random variables.

Derive theoretically the probability density function (PDF) and cumulative density function (CDF) of the Rayleigh distribution as well as its amplitude, and plot the figures in MATLAB. Question 2 If a channel is not changing with time, it does not fade and instead remains at some particular level. Separate instances of the channel in this case will be uncorrelated with one another, owing to the assumption that each of the scattered components fades independently. Once relative motion is introduced between any of the transmitter, receiver, and scatterers, the fading becomes correlated and varying in time. The normalised autocorrelation function of a Rayleigh faded channel with motion at a constant velocity is a zeroth-order Bessel function of the first kind: R( ) at delay

J o (2 f d ) when the maximum doppler shift is fd .

The Jakes model is a well-known and popularly used channel model in simulating a Rayleigh fading channel. The Jakes model has the following characteristics: ●

approximate the Rayleigh fading process by summing a set of complex sinusoids;

●

the sinusoids are weighted so as to produce an accurate approximation of desired channel Doppler spectrum;

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Jakes shows that the theoretical Doppler spectrum for the isotropic scattering mobile radio channel can be well approximated by a summation of relatively small number of sinusoids with frequencies and relative phases of the sinusoids set according to a specific formulation.

Write a MATLAB program to simulate a wireless channel based upon the Jakes model with Doppler shifts of 10 Hz, 100 Hz, and 1000 Hz. You should plot the amplitude of the wireless fading and compare with the theoretical results in Question 1. Comment on the comparison.

Allocation of marks Question 1

50

Question 2

150

Total

200

NB: the discussion should demonstrate that you can interpret the waveforms.

Additional resources You may find the following references useful in completing this assignment: [1] http://en.wikipedia.org/wiki/Rayleigh_fading#Jakes.27_model [2] Rapport, TS 2002, Wireless Communications Principle and Practice , Prentice Hall, New Jersey. [3] Turin, W, Rittwik, J, Martin, C & Winters, J 2001, Modeling Wireless Channel Fading, IEEE , 2001. [4] Steele, R & Hanzo, L 1999, Mobile Radio Communications, Wiley. [5] Patzold, M 2002, Mobile Fading Channels, John Wiley. [6] Jakes, WC 1974, Microwave Mobile Communications, Wiley, New York. ________________ End of Assignment

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ELE4606 – Communication systems

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