Aalto University School of Electrical Engineering. ELEC-E4750 Radiowave Propagation and Scattering Session 8: Cellular links (1)

Transcription

1 ELEC-E4750 Radiowave Propagation and Scattering Session 8: Cellular links (1) ELEC-E

2 Schedule Wk Date Location New topics, lectures and deadlines Tue. 25 Oct. R037/TU Thu. 27 Oct. Tue. 01 Nov. Thu. 03 Nov. Clicker lecture 7 Topic 7: wireless and cellular systems Tue. 08 Nov. Topic 8: cellular links (1) Thu. 10 Nov. Clicker lecture 8 Tue. 15 Nov. Topic 9: cellular links (2) Thu. 17 Nov. Clicker lecture 9; threshold deadline of topics 5-8 Tue. 22 Nov. Topic 10: cellular links (3) Thu. 24 Nov. Clicker lecture 10 Suzan leads on 25 and 27 Oct. Usman is away for Usman and Suzan lead on 24 Nov. 2

3 Books, Topics and Exercises Books Main books S. Saunders, Antennas and Propagation for Wireless Communication Systems, Chapters 3, 5, 6-8, 10, 12 15, Wiley. H. L. Bertoni, Radio propagation for modern wireless systems, Chapters 2-6, Prentice Hall. A. F. Molisch, Wireless Communications, Chapters 1 and 8, Wiley. John A. Richards, Radio wave propagation, an introduction for the non-specialist, Chapter 3, Springer. Hardcover or paperback copies of both books are available in AaltoELEC and main library. Supplemental books: D. M. Pozar, Microwave, Chapter 1, Wiley. Topic 7: Wireless and cellular systems (Ch. 1 of Molisch) Exercise 1: Wireless systems Exercise 2: Radio standardization Topic 8: Cellular links (1) (Ch. 8 and 12, Ch. 6) Exercise 1: Empirical pathloss models Exercise 2: Physical pathloss models 3

4 Contact Sessions for Topic 8 Goals of the present exercise problems are to Get acquainted with the cellular concepts of mobile communications and their most relevant propagation mechanisms (problem 1) Be able to use physical models and compare their merits with respect to empirical models (problem 2) During the contact sessions, you are solving the exercise problems by referring to relevant parts of the course books. A limited number of course books are available in the room. encouraged to discuss with other students and teachers. asked to contact teachers once your solutions are ready. If you prepare exercise solutions in an electronic format (recommended), upload the solution to MyCourses first and then contact teachers. asked to propose points for your ready solutions to the teachers. not given exercise points without discussing with teachers. The discussions MUST happen in the contact sessions. reminded that the threshold deadline of Topic 5-8 exercises is November 17 th.

5 Cellular Scenarios Macrocells Microcells Satellite links (Mega cells) Pico cells 5

6 Q1a: which statement is incorrect? A. Megacells are usually communica2ons between a satellite and ground, like the global posi2oning systems. B. Macrocells are more suitable for serving dense users than picocells. C. Microcell and macrocell base sta2ons are usually placed on building walls and roo?ops, respec2vely. D. The need of microcells and picocells emerged more recently than macrocells.

7 Q1b: which statement is incorrect? A. Megacells are usually communica2ons between a satellite and ground, like the global posi2oning systems. B. Macrocells are more suitable for serving dense users than picocells. C. Microcell and macrocell base sta2ons are usually placed on building walls and roo?ops, respec2vely. D. The need of microcells and picocells emerged more recently than macrocells.

8 Q2a: which statement is incorrect? A. Megacell communica2ons usually rely only on line-of-sight. B. Higher radio frequencies are more suitable for macrocells than for microcells. C. Microcell radio propaga2on is dominated by reflec2ons from walls in a so-called street canyon. D. Pathloss of microcells for indoor users is mainly affected by diffrac2on into building and penetra2on inside the building.

9 Q2b: which statement is incorrect? A. Megacell communica2ons usually rely only on line-of-sight. B. Higher radio frequencies are more suitable for macrocells than for microcells. C. Microcell radio propaga2on is dominated by reflec2ons from walls in a so-called street canyon. D. Pathloss of microcells for indoor users is mainly affected by diffrac2on into building and penetra2on inside the building.

10 Pathloss Models: Applicability Can we use the plane-earth pathloss model for studying the pathloss in macro, micro and picocells? From exercise problem 5.1 TX h b Plane earth RX h m Pathloss [db] PEL FSL 1 d 4 d Distance [m] 10

11 Empirical Models: Based on Measurements (called Channel Sounding) Okumura-Hata model (1968) The most popular empirical model in cellular wireless design Based on measurements made in and around Tokyo Validity range of the model: Frequency f between 150 MHz and 1500 MHz Transmit antenna height h b between 30 and 200 m Receive antenna height h m between 1 and 10 m Transmit-receive antenna distance r between 1 and 10 km COST 231-Hata model (1999) Extension of the Okumura-Hata model for medium to small cities to cover 1500 MHz to 2000 MHz 11

12 Okumura-Hata Model Urban areas : L db = A + B log 10 R E Suburban areas : L db = A + B log 10 R C Open areas : L db = A + B log 10 R D A = log 10 f c log 10 h b B = log 10 h b C = 2 ( log 10 ( f c / 28 )) D = 4.78 ( log 10 f c ) log 10 f c E = 3.2 ( log 10 ( h m )) E = 8.29 ( log 10 ( 1.54 h m )) E = ( 1.1 log 10 f c 0.7 ) h m ( 1.56 log 10 f c 0.8 ) for large cities, f c 300MHz for large cities, f c < 300MHz for medium to small cities 12

13 Empirical Pathloss Estimation Example of macrocellular measurement data from suburban area, and its pathloss model 13

14 Q3a: which statement is incorrect? A. The pathloss model has much greater errors at Tx-Rx distance of 6000 m than at 1000 m. B. The great uncertainty of the pathloss model is due to mobile loca2on variability, which we would need other models to describe them. C. This pathloss model may be used reliably even when we move the base sta2on antenna from roo?op to building wall. D. The pathloss exponent of the fined line is greater than 2.

15 Q3a: which statement is incorrect? A. The pathloss model has much greater errors at Tx-Rx distance of 6000 m than at 1000 m. B. The great uncertainty of the pathloss model is due to mobile loca2on variability, which we would need other models to describe them. C. This pathloss model may be used reliably even when we move the base sta2on antenna from roo?op to building wall. D. The pathloss exponent of the fined line is greater than 2.

16 Ikegami Model Defines excess losses due to rooftop-to-street coupling, on top of free space pathloss (r -2 dependence) " L E =10log 10 f c +10log 10 (sinϕ) + 20log 10 (h 0 h m ) 10log 10 w 10 log % $ 2 ' 5.8 # L r & Φ = angle between the street and the direct line from base to mobile L r = reflection loss =

17 COST231 Walfish-Ikegami Model Restrictions : Frequency f between 800 MHz and 2000 MHz T X height h Base between 4 and 50 m R X height h Mobile between 1 and 3 m T X - R X distance d between 0.02 and 5 km 17

18 Q4a: which statement is incorrect? A. Empirical models are simple in their forms, but are prone to measurement uncertain2es and hence are less accurate than physical models. B. Physical models can calculate pathloss at specific sites more accurately than empirical models, at the expense of greater model complexity. C. The Okumura-Hata model works for different environments with variable terrain profiles. D. The Ikegami model assumes that energy from a base sta2on comes mainly through diffrac2on over roo?ops near the mobile sta2on.

19 Q4b: which statement is incorrect? A. Empirical models are simple in their forms, but are prone to measurement uncertain2es and hence are less accurate than physical models. B. Physical models can calculate pathloss at specific sites more accurately than empirical models, at the expense of greater model complexity. C. The Okumura-Hata model works for different environments with variable terrain profiles. D. The Ikegami model assumes that energy from a base sta2on comes mainly through diffrac2on over roo?ops near the mobile sta2on.

20 Q5a: we have four propaga<on paths between base and mobile sta<ons. Which of the following are the most probable path power order? A. 2 > 1 > 4 > 3. B. 4 > 1 > 2 > 3. C. 3 > 2 > 4 > 1. D. 2 > 4 > 1 > 3. E. No idea. Base station 10 m Plane earth m m 1 m 10 m 4 Mobile

21 Q5b: we have four propaga<on paths between base and mobile sta<ons. Which of the following are the most probable path power order? A. 2 > 1 > 4 > 3. B. 4 > 1 > 2 > 3. C. 3 > 2 > 4 > 1. D. 2 > 4 > 1 > 3. Base station 10 m Plane earth m m 1 m 10 m 4 Mobile

22 Contact Sessions for Topic 8 Goals of the present exercise problems are to Get acquainted with the cellular concepts of mobile communications and their most relevant propagation mechanisms (problem 1) Be able to use physical models and compare their merits with respect to empirical models (problem 2) During the contact sessions, you are solving the exercise problems by referring to relevant parts of the course books. A limited number of course books are available in the room. encouraged to discuss with other students and teachers. asked to contact teachers once your solutions are ready. If you prepare exercise solutions in an electronic format (recommended), upload the solution to MyCourses first and then contact teachers. asked to propose points for your ready solutions to the teachers. not given exercise points without discussing with teachers. The discussions MUST happen in the contact sessions. reminded that the threshold deadline of Topic 5-8 exercises is November 17 th.