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

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

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

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

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

 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

Propagation Principle electric field magnetic field propagation direction 7

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 – Ghz – Ghz ISM band 30kHz300kHz 3MHz 30MHz 300MHz 30GHz300GHz 10km 1km 100m 10m 1m 10cm 1cm 100mm 3GHz 8

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

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

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

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

Networking as Resource Allocation 13

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

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).

Wireless Networks 16

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

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

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

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  WiMAX (IEEE 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  WLAN (IEEE 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  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 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