Advanced Telecommunications Assignment | My Assignment Tutor

EGH443 – Advanced TelecommunicationsAssignment 2 (30%)Released: 19th April 2021Due: Sunday 30th May 2021Your company recently won a bid to design and implement a multi-carrier wireless communication systems to provide wireless broadband services to a regional city in Queensland. Mobileservice providers have overlooked this community due to economic considerations. Deploymentof standard communications systems are costly and the Queensland government is looking fora cheaper alternative. In this task you will perform following tasks to design and test a viablewireless communication system for the above application.Data collected from an extensive measurement campaign commissioned by Queensland government can be used to place base station antennas at strategic locations to maximize reliabilityand coverage. The channel measurement campaign has found that the wireless channel in theintended coverage area has multi-path characteristics, with a number of delayed paths. A setof measured data is available to estimate the path loss exponent.You can extract the path loss data and the measured channel delay profile parameters byfollowing the instructions in Part 1. Each group will have a unique set of data based on yourstudent IDs.Preliminary InstructionsDownload all files to be used in Assignment 2 from blackboard and place them into one workingdirectory. Please also unzip the contents of into this directory.There are 2 files contained within initialise.m – used to generate the data used in this assignment.2. A2GenData.p – called by initialise.mWorkspace PreparationOpen initialise.m with MATLAB and read its instructions. Proceed to insert your groupnumber and the student IDs into the script and generate your data for this assignment. Thechannel delay profile data will be stored in ‘channel.mat’.The initialise.m script only needs to be executed once.1Part 1 { Estimate Path Loss Exponent of the ChannelLarge scale fading can be modeled as a combination of the path loss and log normal shadowing.The path loss LdB in dB as a function of distance d is calculated by:LdB = L0;dB + 10n log10 dd0 + Xσ;where L0;dB is the path loss in dB obtained at the reference distance of d0 away from thetransmitter, n the path loss exponent and Xσ the shadowing component. The shadowingcomponent is normally distributed when the path loss is specified in dB, and has zero meanwith a standard deviation of σ also specified in dB.In this part you will be estimating the value of n and σ from data in following two variables.• d: This vector corresponds to the distance between transmitter and receiver at which ameasurement was taken. The units are in meters.• LdBShadow: This matrix stores the data captured in a measurement campaign. Each rowof the matrix corresponds to a new measurement trial. The units are in dB.1.1 Present the measured path loss data at different distances in a scatter plot. Describe thereasons for variations observed in the measurement at a given distance.1.2 For each of the distances inside d, calculate the average path loss and plot in a separatefigure.1.3 Fit a linear model for the measured data. Estimate the path loss exponent (n) andpath loss at the reference distance (d0). The fitlm function may be a helpful MATLABfunction.1.4 With a transmitter and receiver antenna gains of 10 dB and 3 dB respectively and areceiver sensitivity of -92 dBm, estimate the minimum transmitted power required if thereceiver is 4 km away from the transmitter. In this calculation you must allow for a 20dB fade margin between the received power and the receiver sensitivity.1.5 For each of the distance inside d, calculate the standard deviation and find an estimatefor the standard deviation of XσPart 2 { Design an OFDM SystemYou are asked to design a fixed wireless access (FWA) system to provide wireless broadbandservices to regional Australia. Your system should be capable of offering a 150 Mb/sec downloadspeed using a 40 MHz band centered around 3.6 GHz spectrum. Remember you need to optimisethe bandwidth usage and choose the smallest possible modulation scheme to offer good biterror-rate performance at low transmit power.2.1 Load the channel channel.mat file and extract the variables pvec and tvec, where pvecand tvec are channel time delay vector in nanoseconds and the delayed relative powervector of the channel in dB respectively. Plot and label the multipath impulse responseof the channel.22.2 Estimate the RMS delay and the coherence bandwidth of the channel.2.3 Design your OFDM system using above information. You need to decide following parameters of your system.{ N – Number of sub-carriers.{ T – OFDM Symbol duration{ Tg – Guard interval{ m – Modulation index (smallest possible.)Justify your selections.NOTE: The guard interval Tg > 10×στ and the Sub-carrier bandwidth ∆(f) ≤ B10c , whereBc is the coherence bandwidth of the channel.2.4 Estimate the maximum data rate of your system if the maximum allowable modulationindex is 10 (1024-QAM). Compare the this data rate with that of a equivalent singlecarrier system and comment on whether this single carrier system would be appropriatefor a fading channel.2.5 Write a MATLAB code to simulate the performance of the OFDM system in AWGNchannel. Simulate and plot the bit error rate performance within the bit-error rate (BER)range from 0.5 to 10-5 and compare with the theoretical bit-error rate performance.You can use built-in MATLAB functions in this step. Some of the useful MATLABfunctions would be, fft, ifft, qammod, awgn and biterr. However, do not use built-inMATLAB functions to implement the OFDM system.2.6 Comment on the observed bit-error-rate performances and describe in detail two methodsthat can be used by a practical communication system to improve the bit error rate atthe receiver.Part 3 { Performance in Fading ChannelsYou are able to meet the required data-rate of the AWGN channel. Now you need to simulatethe performance of above OFDM system in a Rayleigh fading channel with the impulse responsegiven by pvec and tvec.The impulse response of the fading channel follows a Raleigh distribution. Let’s define acomplex Gaussian random variable as h = X +i×Y , where both X and Y are Gaussian randomvariables with zero mean and the same variance. The envelope (square root) of this complexGaussian random variable has a Rayleigh distribution.3.1 Simulate a complex Gaussian random variable, h with variance 1 using the randn command and plot a normalised histogram of its envelope. Compare the normalised histogramagainst the theoretical Rayleigh distribution, given by:fA(a) = aσ2 exp -2aσ223If Xn(n = 1; 2; : : : N) is a vector of modulated symbols, the OFDM signal can be generated by:xk = ifft(Xn); k = 1; 2; : : : NAssuming the fading channel is stationery during the OFDM symbol duration, we can find thefrequency response of the channel using:Hn= fft(h) n = 1; : : : NThe FFT output at the receiver can be expressed as:Yn= HnXn + nnTherefore, the received signal can be recovered using a single tap equalisation:~Xn=Yn Hn= Xn +nnHn= Xn + ~ nnNow, X~n can be demodulated to extract the transmitted data. You can assume that full channelinformation is available at the receiver for the following simulation. In practice, channel needsto be estimated using pilot symbols.3.2 Write MATLAB code to simulate the performance of OFDM system in flat (single path)Rayleigh fading channel within the Eb=N0 range from 0 dB to 30 dB. Simulate and plot thebit error rate performance and compare with the theoretical bit-error rate performancein fading and AWGN channels.The power delay profile of the multipath fading channel is given as:h(τ) = p(τi)δ(t – τi) i = 1 : : : L;where L is the number of paths. For the simulation we need to normalise the power. Thenormalisation factor α can be estimated as:α =1PL i p(τi)Then the variance of each path can be estimated as:σ(τi) = αp(τi)Finally, each path can be generated as below:h(τi) = rσ(2τi) × (randn(1,K) + 1i ∗ randn(1,K))where K is the number of channel samples.3.3 Simulate and plot the performance of the OFDM system in a multipath Rayleigh fadingchannel. Compare bit error rate performances in AWGN channel, flat fading channel andmulti-path fading channel and comment on the observations.You can load the channel.mat file to get the multipath power delay profile of the channel.4Part 4 { Error Detection and Correction5.1 The uncoded OFDM system implemented in Part 3 is not providing the reliability requiredby the Queensland government for Eb=N0 values above ≈ 8 dB.Implement a forward error correction code to improve the reliability of the received data.You can choose any forward error correction method for this section. You can also usebuilt-in MATLAB functions to implement the chosen error control coding method.Simulate and plot the bit-error rate of the coded OFDM system in the above multi-pathfading channel and compare with the bit error rate performance of the uncoded OFDMsystem in the multipath-fading channel.5.2 Discuss the effects that a multipath fading channel has on bit errors in the system compared with a AWGN channel. Does your forward error correction code address theseeffects?5.3 What is the data rate of this system after taking into account the new forward errorcorrection encoding system?5.4 The Queensland government also wants the proposed wireless system to be used for mobilebanking and other financial activities. You have been instructed to update the systemwith an appropriate cyclic-redundancy check code (CRC) to ensure bit errors can bedetected.This CRC should be implemented to detect whether the decoded data after the forwarderror correction code contains any errors. The CRC code should have a word length ofn = 16 and a generator polynomial of length n – k = 5.Demonstrate that this CRC code can detect errors in your system.5.5 Estimate the rate at which a user can transmit data when the system is upgraded withthe chosen error control coding and CRC scheme.Reflection (Mandatory)Each member of the group should write a reflection and appended to the endof your report. Include a short discussion of about 100 words that addresses problemsencountered, any lessons learned and things that you would have done differently. This sectionis mandatory and the assignment is regarded as incomplete if absent. If you had any groupconcerns throughout the duration of your assignment, please address them here.Academic Integrity Declaration (Mandatory)The provided Academic Integrity Declaration must be completed and submitted along with theassignment. Assignments with incomplete or missing declarations are not marked.5Report and Code Presentation (Specific-Question and/orOverall Deductions)This assignment includes elements of written and coding assessment. One assignment reportand one set of code should be submitted for each group or individual (depending on how theassignment has been completed). Marks are based on how easily and effectively ideas are articulated to the reader. The CRA has the outlines to the marking standards.The Report ComponentAn outstanding report demonstrates knowledge and understanding of the subject area. It willcommunicate ideas clearly and logically with a combination of visual, mathematical and codeassets. Correct information not articulated clearly will also attract deductions.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.Document flow and coherency is to be prioritised. Reports that are difficult to navigate aremarked poorly in this criteria. This means avoid the use of see appendix” and refer to .mfile”.It is important that all code and justification for each part is included in yourreport submission. Your report is being marked, your code is included for justification.Mathematical working that shows the logical procedure or justification of how you arrivedat your solutions are required. This working need not be typed but it is expected to be legibleand able be followed in a coherent manner.Include a title page that states the unit name, unit code, assignment number, your nameand student number. Do not include a table of contents, list of figures, nor a list oftables.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 ComponentWorking code is expected to be submitted along side your report to Blackboard. The codeneeds to be executable (in .m) and without run-time error. No error correction will be madeto make your code run”. If an error is encountered at execution, your assignment cannot bemarked. Coding for this assignment should remain within one file (unless otherwise explicitlyinstructed). Only include additional .m files if absolutely necessary. Using a separate file foreach sub section constitutes poor code management.Code should be fully commented to describe intent. Quality comments encapsulate yourunderstanding 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. .6Submission ProtocolSubmission deadline is on Sunday 30 May 2021. This will be a hard deadline and late submissionpenalties will apply. As per QUT policy, late assignments receive 0 marks.Assignments are to be submitted in soft-copy through QUT Blackboard as asingle .zip file that includes the following• A completed and signed academic integrity declaration in PDF format.• The report in PDF format (Handwritten report are not acceptable.)• initialise.m with your student ID/s of you/your team.• channel.mat file generated during workspace preparation.• MATLAB script/s you have developed as a result of explicit assignment instructions.The submission link is accessible through: EGH443 21se1 ! Assessment ! Assignment 2! Assignment 2: Submission. 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.All documents can be reviewed after submission and thus it is your responsibility to verifythat 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. Don’trisk the late penalty and submit early.7


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