The numbers in parentheses indicate the number of marked items (1 mark each). Annotations in the marked PDF indicate the number of marks deducted. A red X "(see solutions)" indicates one mark was deducted. Quizzes Quiz 1 (12) Q1 - correct rho in dB - correct rho in linear units - correct probability Q2 - correct f_m (2) - correct tau-bar - correct bits Q3 - correct excess delays, dB to power conversion and normalized levels (3) - correct mean excess delay - correct RMS delay spread Quiz 2 (9) Q1 - use of mutual information equation - correct joint probabilities - correct marginal probabilities - correct answer Q2 - correct equation - correct answer Q3 - correct G(x) as bit sequence - correct method - correct result Quiz 3 (12) Q1 (3) - sampling rate = 10 MHz - guard time - 1000ns/100ns = 10 samples - subcarrier spacing = 10 MHz / 256 ~= 39.1 kHz Q2 (6) (lambda = 300e6/3e9 = 0.1m, 4pi d ~= 1e5) - path loss = (1e-1/1e5)^2 = 1e-12 = 120dB - received signal power is 30 + 15 - 120 = -75 dBm - received noise power -174 + 2 + 62 = -110 dBm - SNR = 35 dB - link margin = 10 dB - YES Q3 (3) - OIP3 is 40dB/2 = 20 dB above output - need 20 dBm output - need 40 dBm OIP3 Midterm Exam 1 (marked out of 15) [Unlike Quiz 1, if the wrong method/equation was used or a mistake was made in a previous part of the same question, I deducted marks for subsequent wrong answers as well.] Q1 - only positive frequencies - "bathtub" shape - correct f_m=30 Hz Q2 - equation - result = 0.92 Q3 - convert to threshold (-20/10) - equation - answer = 2.3% Q4 - probability w/o ~0.1 - probability w/ ~0.1E-3 Q5 - equation - wavelength & loss in linear units 2/3m, 1/4 - received power ~18nW or ~-48 dBm Q6 - switching - why (only receive/monitor one branch) Midterm Exam 2 (marked out of 19) Q1 (3) - used AWGN capacity formula - capacity ~= 40 Mb/s - conclusion is "not plausible" Q2 (3) - n=5 k=3 - transmitted codeword = [ 1 0 1 0 1 ] - parity check matrix = [ 1 1 1 1 0 ; 0 1 1 0 1 ] Q3 (4) - G = [ 1 0 0 1 ; 0 1 1 1 ] - codewords = 0000 0111 1001 1110 - distances = 3 2 3 ; 3 2 ; 3 - minimum distance = 2 [or some other reasonable explanation for dmin = 2] Q4 (4) - Eb/No with coding (2) (-2 if code rate not taken into account) - Eb/No without coding - coding gain ~= 3 or 4.8 dB Q5 (5) - duration ( = 102.4 us + 2 * 10 = 122.4 us) (2) - bps ~= 10E6 (~15 if had wrong duration) - bandwidth ~= 6 MHz - spectral efficiency ~= 1.7 b/s/Hz (~2.5 if had wrong duration) Final Exam Q1 (3) - use of Rayleigh CDF (no marks deducted here if got probabilites "backwards" although 1 mark was deducted for wrong answer final answer) - solve CDF equation for rho & compute the mean - correct answer and units (no marks deducted if also computed correct RMS voltage of the envelope) Q2 (5) - convert distance to time - convert to powers to linear units - compute normalized delays - compute excess delay spread - OFDM guard time Q3 (5) - correct wavelength - correct path loss - correct area of circle, correct gain from Ae - convert (or give) power to dBm - correct power Q4 (2) - correct normalized weights - correct resulting SNR Q5 (2) - correct capacity equation for BSC - correct result Q6 (2) - a correct generator matrix - the parity-check matrix for this generator matrix Q7 (3) - correct method (e.g. output level in dBm - difference/2) - correct OIP3 - correct IIP3 Q8 (1) - correct answer (FHSS) and explanation Q9 (1) - correct answer (MIMO) and explanation Labs Lab 1 (3) - a plot of amplitude vs time - a histogram of the amplitude and a fit Rayleigh - a log-log plot of path loss vs distance [The calculation of the path loss exponent was not marked for reasons that will be explained in a lecture.] Lab 2 (8) - four results (GUI and spectrum analyzer captures) (4) - basic - frequency shift - increased PRBS period - disabling the low-pass filter - answers to questions (4): - one frequency equal to the sum - any correct differences - periods are 500/7 ~= 71 kHz and 500/255 ~= 2 kHz - no anti-alising Lab 3 (6) - GRC flowgraph without FEC - GRC flowgraph with FEC - screen capture with showing signals - spreadsheet with data - plot - calculation of coding gain Lab 4 (5) - GRC flow graph - frequency spectra for N=128, 32 subcarrier, 1 MHz - " for N=256 & explanation - " for nc=64 & explanation - " for fs=2 MHz & explanation Lab 5 (3) - successful publishing of secret (2) - screen capture of RSSI display in report (1)