Sirindhorn International Institute of Technology Thammasat University at Rangsit. ECS 455: Problem Set 1

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Sirinhorn International Institute of Technology Thammasat University at Rangsit School of Information, Computer an Communication Technology ECS 455: Problem Set 1 Semester/Year: /016 Course Title:

(1 pt) Write your first name an the last three igit of your stuent ID on the upper-right corner of every submitte sheet.

1 Sirinhorn International Institute of Technology Thammasat University at Rangsit School of Information, Computer an Communication Technology ECS 455: Problem Set 1 Semester/Year: /016 Course Title: Mobile Communications Instructor: Asst. Prof. Dr. Prapun Suksompong (prapun@siit.tu.ac.th) Course Web Site: Due ate: February 8, 017 (Wenesay), 4:30 PM Instructions 1. (1 pt) Write your first name an the last three igit of your stuent ID on the upper-right corner of every submitte sheet.. (1 pt) For each part, write your explanation/erivation an answer in the space provie. 3. (8 pt) It is important that you try to solve all non-optional problems. 4. Late submission will be heavily penalize. Questions 1. Cellular communication in the USA was limite by the Feeral Communication Commission (FCC) to one of three frequency bans, one aroun 0.9 GHz, one aroun 1.9 GHz, an one aroun 5.8 GHz [Tse an Viswanath, 005, p. 11]. Fin the corresponing wavelengths. Page 1 of 4

2 . Uner the free-space PL moel, how much receive power is lost when the operating frequency (carrier frequency) is change from fc = 700MHz to fc = 1,800 MHz? 3. Consier a cellular system with operating frequencies aroun fc = 900 MHz, cells of raius 100 m, an nonirectional antennas. a. Uner the free-space path loss moel, what transmit power is require at the base station such that all mobile evices within the cell receive a minimum power of 10 μw? b. How oes this change if the system frequency is 5 GHz? [Example.1 in Golsmith, 005] Page of 4

4. Let us take a look at the microwave ultra-wieban (UWB) impulse raio. UWB is a powerlimite technology in the unlicense ban of 3.1 10.6 GHz.

3 4. Let us take a look at the microwave ultra-wieban (UWB) impulse raio. UWB is a powerlimite technology in the unlicense ban of GHz. For the multiban OFDM (MB- OFDM) UWB systems, there are 5 ban groups whose centers are provie in Table 1 below Table 1: Relationship between center frequencies an coverage range for MB-OFDM UWB systems. Ban Group Center frequency (MHz) Range (meter) 1 3, , ,18 4 8, ,03 Accoring to the Friis equation, given the same transmitte power, propagation attenuation will be ifferent for each ban because they use ifferent frequency. (This variation of receive signal strength can be a bothering factor.) If ban group 1 can cover 10 meters, estimate the coverage ranges for other ban groups in Table 1. Show your calculation an explanation here but put your answers in Table 1. Extra Questions Here are some optional questions for those who want more practice. 5. Consier the set of empirical measurements of Pr/Pt given in Table below for a system operating aroun 900 MHz. Table Path Loss Measurements Distance from Transmitter 10m 0m 50m 100m 300m Pr/Pt -70 B -75 B -90 B -110 B -15 B Page 3 of 4

4 a. Fin the path loss exponent that minimizes the sum of square ifferences between the calculate B power ratio using the simplifie path loss moel an the empirical B power ratio measurements, assuming that 0 = 1 m an K is etermine from the free space path gain formula at this 0. P 10log 10log K 10log, where r 0 Hint: Recall that Pt K 4 0. The values of f an 0 can be use to etermine K an hence b. So, the only unknown parameter is. Here, we are given 5 values of which we will enote by 1,,, 5. For a chosen value of, we can plug these istance values into the formula above to calculate 10log10 Pr P which will be close to (but not exactly the same as) the Pr 10log10 P t provie in the table. Our task, then, is to fin the best that minimize their (average) ifference; that is, we want to mimimize 5 i1 ri 10log K 10log where r i is the empirical power ratio measurements provie in the table. To fin the best, simply fin the root of the erivative wrt.. b. Fin the receive power at 150 m for the simplifie path loss moel with the path loss exponent foun in part (a) an a transmit power of 1 mw (0 Bm). [Example.3 in Golsmith, 005] 6. [Calculus*] Consier the ranom variable R whose ln, 0 i k R for some constant an positive constants k an. (An example of this is the ranom attenuation factor that moels the path loss an shaowing effect in wireless communication.) a. Fin the pf fr r of R. b. Fin the expecte value R. (Hint: Let integration of any pf will always give 1.) z kln r c. Fin the meian of R. (This is the value of r at which. Then, use the fact that the 1 FR r.) t Page 4 of 4

SECONDARY TRANSMISSION POWER OF COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS

SECONDARY TRANSMISSION POWER OF COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS Xiaohua Li 1 1 Department of ECE State University of New York at Binghamton Binghamton, NY 139, USA {xli,jhwu1}@binghamton.eu