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Georgia Institute of Technology School of Electrical and Computer Engineering ECE6604 Personal , Portable Communications Final Exam Planting season 2010 Wednesday May six, 11: 30am , 2: 20pm • Attempt your concerns. • All questions are of equal benefit. • Open book, open notes, exam.

1a) 5 marks: The LCR on the normalized tolerance? for a 2-D isotropic scattering channel can be expressed because v two LR = 2? fm? e?, in which? =? and Rrms sama dengan R? l = R Rrms E[? 2 ] is the rms envelope level. i) Discover the normalized threshold level? o at which the LCR reaches the maximum benefit. i) Describe why the LCR in? decreases as? deviates from? o. 1b) 5 represents: Consider a cell phone system using a carrier frequency of 2 GHz. Suppose that the consumer is in an automobile travelling at 60 km/h. Assuming that the channel is characterized by SECOND isotropic scattering,? nd i) the LCR at the normalized level? =? 3 dB. ii) the AFD with the normalized level? =? 3 dB. 2) The power hold off pro? le for a WSSUS channel has by? gg (? ) = zero. 5[1 + cos(2? /T )]#@@#@!, zero, 0?? To /2 otherwise a) several marks: Locate the funnel frequency relationship function. ) 4 markings: Calculate the mean wait and rms delay distributed. c) 3 marks: In the event T sama dengan 0. one particular ms, determine whether the channel exhibits frequencyselective fading for the GSM program. 3) Cell phone CDMA systems use smooth hando?, the place that the transmissions to/from multiple basic stations happen to be combined to provide a macro-diversity. Here we consider the e? ects of course loss and shadowing and ignore multipathfading. Suppose that the received sign power matching to the website link with the ith base-station,? professional indemnity, has the likelihood density function p? pi (x) = v dBm) (x?? pi (dBm) ) 1 experience? 2 a couple of? 2?? installment payments on your where? pi (dBm) sama dengan E[? pi (dBm) ] The? professional indemnity are believed to be statistically independent. a) 5 signifies: The change link uses selection merging such that the very best basestation is actually selected. In this instance,? s l (dBm) An outage takes place if? s p sama dengan max? p1 (dBm)? a (dBm),…,? pL (dBm) (dBm). What is the probability of outage? b) 5 represents: The forward link uses coherent merging such that? mr(dBm) =? p1 p (dBm) +… &? pL (dBm) Again, a great outage arises if? mr(dBm)? th (dBm).

What is the probability of p outage if? p1 (dBm) =? p2 (dBm) = · · · =? pL (dBm)? 4) Consider the reception of a signal in the presence of the single co-channel interferer and neglect the e? ect of AWGN. The received signal electricity, C, and interference power, I, because of Rayleigh falling have the exponential distributions one particular? x/C? at the C one particular? pI (y ) =? e? x/I I pC (x) =? where C and I will be the average received signal power and disturbance power, correspondingly. a) your five marks: Assuming that C and I are self-employed random parameters,? d the probability density function pertaining to the carrier-to-interference ratio? sama dengan C. I Hint: If perhaps X and Y are independent randomly variables, then this probability thickness function of U sama dengan X/Y is usually pU (u) = pXY (v, v/u)|v/u2 |dv. b) 5 signifies: Now suppose that the system uses 2-branch variety diversity. The branches happen to be independent and balanced (i. e., the distribution pU (u) is definitely the same for every branch. What is the probability density function of? with the output of the selective unir? 5) Guess that a system uses selection diversity.

The divisions experience independent Rayleigh fading. However , the average received bit energy-to-noise rate on each range branch is di? erent, such that? i actually = 2? i? to? i sama dengan 1,…, T a) a few marks: Locate the likelihood density function of the little bit energy-to-noise percentage at t the output in the selective �crire, denoted by? b. b) 5 represents: If DPSK modulation is utilized, write down a manifestation for the probability of bit error. Obtain a closed-form expression if possible, otherwise keep your appearance in important form.