E716_lec10

7th Year, Integrated Technical Education Cluster AlAmeeria‎
lec#10, Mobile Communication Systems

Transcript

1. Lecture #10 Effects of Mobile Radio Propagation (p1) Instructor: Dr. Ahmad El-Banna December 2014 E-716-A Mobile Communications Systems Integrated Technical Education Cluster At AlAmeeria‎ © Ahmad El-Banna 1
2. Agenda Types of waves Propagation Mechanisms Path Loss 2 E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
3. Speed, Wavelength, Frequency System Frequency Wavelength AC current 60 Hz 5,000 km FM radio 100 MHz 3 m Cellular 800 MHz 37.5 cm Ka band satellite 20 GHz 15 mm Ultraviolet light 1015 Hz 10-7 m Light speed = Wavelength x Frequency = 3 x 108 m/s = 300,000 km/s E-716-A, Lec#10 , Nov 2014 © Ahmad El-Banna 3 3
4. 4 Types of Waves Earth Sky wave Space wave Ground wave Troposphere (0 - 12 km) Stratosphere (12 - 50 km) Mesosphere (50 - 80 km) Ionosphere (80 - 720 km) E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
5. Radio Frequency Bands Classification Band Initials Frequency Range Characteristics Extremely low ELF < 300 Hz Ground wave Infra low ILF 300 Hz - 3 kHz Very low VLF 3 kHz - 30 kHz Low LF 30 kHz - 300 kHz Medium MF 300 kHz - 3 MHz Ground/Sky wave High HF 3 MHz - 30 MHz Sky wave Very high VHF 30 MHz - 300 MHz Space wave Ultra high UHF 300 MHz - 3 GHz Super high SHF 3 GHz - 30 GHz Extremely high EHF 30 GHz - 300 GHz Tremendously high THF 300 GHz - 3000 GHz E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna 5
6. 6 Propagation Mechanisms • Reflection • Propagation wave impinges on an object which is large as compared to wavelength - e.g., the surface of the Earth, buildings, walls, etc. • Diffraction • Radio path between transmitter and receiver obstructed by surface with sharp irregular edges • Waves bend around the obstacle, even when LOS (line of sight) does not exist • Scattering • Objects smaller than the wavelength of the propagation wave - e.g. foliage, street signs, lamp posts • Shadowing ! distance sender transmission detection interference E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
7. 7 Radio Propagation Effects Transmitter d Receiver hb hm Diffracted Signal Reflected Signal Direct Signal Building reflection scattering diffraction shadowing refraction E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
8. Free-space Propagation • The received signal power at distance d: where Pt is transmitting power, Ae is effective area, and Gt is the transmitting antenna gain. Assuming that the radiated power is uniformly distributed over the surface of the sphere. Transmitter Distance d Receiver hb hm 2 r 4 P d P G A t t e   E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna 8
9. 9 Antenna Gain • For a circular reflector antenna Gain G =  (  D /  )2  = net efficiency (depends on the electric field distribution over the antenna aperture, losses, ohmic heating , typically 0.55) D = diameter thus, G =  ( D f /c )2, c =  f (c is speed of light) Example: • Antenna with diameter = 2 m, frequency = 6 GHz, wavelength = 0.05 m G = 39.4 dB • Frequency = 14 GHz, same diameter, wavelength = 0.021 m G = 46.9 dB * Higher the frequency, higher the gain for the same size antenna E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
10. 10 Land Propagation • The received signal power: where Gr is the receiver antenna gain, L is the propagation loss in the channel, i.e., L = LP LS LF L P G G P t r t r  Fast fading Slow fading Path loss E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
11. 11 Path Loss (Free-space) • Definition of path loss LP : Path Loss in Free-space: where fc is the carrier frequency. This shows greater the fc , more is the loss. , r t P P P L  ), ( log 20 ) ( log 20 45 . 32 ) ( 10 10 km d MHz f dB L c PF    E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
12. 12 Path Loss (Land Propagation) • Simplest Formula: Lp = A d-α where A and α: propagation constants d : distance between transmitter and receiver α : value of 3 ~ 4 in typical urban area E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
13. 13 Example of Path Loss (Free-space) Path Loss in Free-space 70 80 90 100 110 120 130 0 5 10 15 20 25 30 Distance d (km) Path Loss Lf (dB) fc=150MHz fc=200MHz fc=400MHz fc=800MHz fc=1000MHz fc=1500MHz E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
14. 14 Path Loss (Urban, Suburban and Open areas) • Urban area: where • Suburban area: • Open area:     ) ( log ) ( log 55 . 6 9 . 44 ) ( ) ( log 82 . 13 ) ( log 16 . 26 55 . 69 ) ( 10 10 10 10 km d m h m h m h MHz f dB L b m b c PU                                    city medium small for MHz f for m h MHz f for m h city e l for MHz f m h MHz f m h c m c m c m c m & , 400 , 97 . 4 ) ( 75 . 11 log 2 . 3 200 , 1 . 1 ) ( 54 . 1 log 29 . 8 arg , 8 . 0 ) ( log 56 . 1 ) ( 7 . 0 ) ( log 1 . 1 ) ( 2 10 2 10 10 10  4 . 5 28 ) ( log 2 ) ( ) ( 2 10          MHz f dB L dB L c PU PS   94 . 40 ) ( log 33 . 18 ) ( log 78 . 4 ) ( ) ( 10 2 10     MHz f MHz f dB L dB L c c PU PO E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
15. 15 Path Loss • Path loss in decreasing order: • Urban area (large city) • Urban area (medium and small city) • Suburban area • Open area E-716-A, Lec#9 , Dec 2014 © Ahmad El-Banna
16. • For more details, refer to: • Chapter 2, A. Goldsmith, Wireless Communications, 2004. • The lecture is available online at: • https://speakerdeck.com/ahmad_elbanna • For inquires, send to: • ahmad.elbanna@feng.bu.edu.eg 16 E-716-A, Lec#10 , Nov 2014 © Ahmad El-Banna