1. نیمسال دوّم 93-92 افشین همّت یار دانشکده مهندسی کامپیوتر مقدمه شبکه‌های بی‌سیم (873-40) مقدمه

2. ریز نمرات تمرین‌ها تمرین‌ها تشریحی و تحلیلی 4 نمره هر دو هفته یک تمرین تشریحی و تحلیلی 4 نمره هر دو هفته یک تمرین مطالعه و تحلیل مقاله 4 نمره هر دو هفته یک مقاله مطالعه و تحلیل مقاله 4 نمره هر دو هفته یک مقاله امتحان‌ها امتحان‌ها اول 2 نمره 11 اسفند 1392 اول 2 نمره 11 اسفند 1392 دوم 2 نمره 25 اسفند 1392 دوم 2 نمره 25 اسفند 1392 سوم 2 نمره 7 اردیبهشت 1393 سوم 2 نمره 7 اردیبهشت 1393 چهارم 2 نمره 21 اردیبهشت 1393 چهارم 2 نمره 21 اردیبهشت 1393 پنجم 2 نمره 5 خرداد 1393 پنجم 2 نمره 5 خرداد 1393 ششم 2 نمره 27 خرداد 1393 ششم 2 نمره 27 خرداد 1393 2

3. References  A. Kumar, D. Manjunath, and J. Kuri, Wireless Networking, Morgan Kaufmann Publishers, 2008.  C.M. Cordeiro and D.P. Agrawal, Ad Hoc and Sensor Networks: Theory and Applications, 2nd Ed, World Scientific, 2011. 3

4. Contents Background Wireless communication: concepts, techniques, and models Application models and performance issues Cellular FDM-TDMA Cellular CDMA Random Access and Wireless LANs (WLANs) Mobile Ad-hoc Networks (MANETs) Wireless Mesh Networks (WMNs) Wireless Sensor Networks ( WSNs) 4

5. Wired Vs. Wireless Communications WiredWireless Each cable is a different channelOne media shared by all Low signal attenuationHigh signal attenuation No interferenceHigh interference noise; co-channel interference; adjacent channel interference 5

6.  Advantages Sometimes it is impractical to lay cablesSometimes it is impractical to lay cables User mobilityUser mobility CostCost  Limitations Bandwidth Bandwidth Fidelity Fidelity Power Power Security Security Why Wireless? 6

7. Propagation Principle electric field magnetic field propagation direction 7

8. Electromagnetic Spectrum Propagation characteristics are different in each frequency band. UV 1 MHz 1 kHz 1 GHz 1 THz 1 PHz 1 EHz infrared visible X rays Gamma rays LFHF VHFUHFSHFEHF MF AM radio S/W radio FM radio TV cellular 902 – 928 Mhz 2.4 – 2.4835 Ghz 5.725 – 5.785 Ghz ISM band 30kHz300kHz 3MHz 30MHz 300MHz 30GHz300GHz 10km 1km 100m 10m 1m 10cm 1cm 100mm 3GHz 8

9. Unlicensed Radio Spectrum (ISM: Industrial, Science, Medicine) 902 Mhz 928 Mhz 26 Mhz 83.5 Mhz 125 Mhz 2.4 Ghz 2.4835 Ghz 5.725 Ghz 5.850 Ghz cordless phones baby monitors WaveLan 802.11b Bluetooth Microwave oven 802.11a 33cm 12cm 5cm 9

10. Propagation Mechanisms Non Line-of-Sight Reflection λ << D Diffraction λ  D Scattering λ >> D S D Line-of-Sight 10

11. Propagation in the “Real World” a wave can be absorbed reflect penetrate bend 11

12. Path-loss Models  Path-Loss Exponent Depends on environment: L(d) = L(d 0 )(d/d 0 ) n Free spacen = 2 Urban area cellularn = 2.7 to 3.5 Shadowed urban celln = 3 to 5 In building LOSn = 1.6 to 1.8 Obstructed in buildingn = 4 to 6 Obstructed in factoriesn = 2 to 3 12

13. Networking as Resource Allocation 13

14. Resource Allocation 14  Wireline o Static bit-carrier infrastructure o High quality digital transmission over copper or optical media o Bit pipes with a certain bit rate and very small bit error rate o Dynamically reconfigured based on traffic demands  Wireless o Point-to-point Line-of-sight (same as wireline or higher bit rate) (same as wireline or higher bit rate) o Time-varying channel impairments o Adaptable PHY layer

15. Wireless Networking 15  Our view: All the mechanisms, procedures, or algorithms for efficient sharing of a portion of the radio spectrum so that all instances of communication between the various devices obtain their desired Quality of Service (QoS).

16. Wireless Networks 16

17. Fixed Networks 17  Point to point  Long distance transmission  High gain antennas  Tall masts  Higher bit rate and also higher bit error rate than wireline

18. Mobile and Ad-hoc Networks 18 Access Networks Mesh Network Access Networks Mesh Network

19. Mobile Networks: Circuit Multiplexing 19  GSM (2G) o Narrowband o FDM-TDMA o High SINR o Careful frequency planning to avoid co- channel interference o Call admission control GSM-GPRS (2.5G) Combining TDM Time slots GSM-GPRS (2.5G) Combining TDM Time slots GSM-EDGE (2.75G) Combining TDM Time slots and higher order modulation schemes GSM-EDGE (2.75G) Combining TDM Time slots and higher order modulation schemes

20. Mobile Networks: Centralized Statistical Multiplexing (1) 20  CDMA (IS-95) o Wideband o CDMA (Spread spectrum) o Correlation receivers o No frequency planning o Interference limited o Call admission control  WCDMA (CDMA-2000) o Most widely adapted standard for 3G

21. 21  WiMAX (IEEE 802.16 series) o Wireless access to Internet o Fixed subscriber stations o OFDMA o TDD (uplink & downlink) o Specifications now have been extended to include broadband access to mobile users. Mobile Networks: Centralized Statistical Multiplexing (2)

22. 22  WLAN (IEEE 802.11 series) o Wireless access to Internet o Limited mobility o Statistical TDMA o Few Mbps (over 100s of meter) up to 100Mbps (over a few meters) up to 100Mbps (over a few meters) o MIMO-OFDM (enhancement) Mobile Networks: Distributed Statistical Multiplexing

23. 23  No infra-structure  Multi-hop communication  Point-to-point store and forward traffic  Miniature devices for nodes  Low power, low bit rate digital radio transceiver, and small battery Ad hoc Networks: Internet Access and Sensor Networks

24. 24 General:  Transport of the user’s bits over the shared radio spectrum  Neighbor discovery, association and topology formation, routing  Transmission scheduling (cross layer) Only in ad hoc sensor networks:  Location determination  Distributed computation Technical Elements