نیمسال دوّم افشین همّت یار دانشکده مهندسی کامپیوتر مقدمه شبکه‌های بی‌سیم (628-40) 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 ( تهران ) امتحان‌ها ( تهران ) اول 2 نمره 10 اسفند 1393 اول 2 نمره 10 اسفند 1393 دوم 2 نمره 24 اسفند 1393 دوم 2 نمره 24 اسفند 1393 سوم 2 نمره 6 اردیبهشت 1394 سوم 2 نمره 6 اردیبهشت 1394 چهارم 2 نمره 20 اردیبهشت 1394 چهارم 2 نمره 20 اردیبهشت 1394 پنجم 2 نمره 3 خرداد 1394 پنجم 2 نمره 3 خرداد 1394 ششم ( پایان‌ترم )2 نمرهخرداد 1394 ششم ( پایان‌ترم )2 نمرهخرداد

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 ( کیش ) امتحان‌ها ( کیش ) اول 2 نمره 14 اسفند 1393 اول 2 نمره 14 اسفند 1393 دوم 2 نمره 20 فروردین 1394 دوم 2 نمره 20 فروردین 1394 سوم 2 نمره 3 اردیبهشت 1394 سوم 2 نمره 3 اردیبهشت 1394 چهارم 2 نمره 17 اردیبهشت 1394 چهارم 2 نمره 17 اردیبهشت 1394 پنجم 2 نمره 31 اردیبهشت 1394 پنجم 2 نمره 31 اردیبهشت 1394 ششم ( پایان‌ترم )2 نمرهخرداد 1394 ششم ( پایان‌ترم )2 نمرهخرداد

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 Cellular OFDMA-TDMA Random Access and Wireless LANs (WLANs) Mobile Ad-hoc Networks (MANETs) Wireless Mesh Networks (WMNs) Wireless Sensor Networks ( WSNs) 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 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? 7

Propagation Principle electric field magnetic field propagation direction 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 – Ghz – Ghz ISM band 30kHz300kHz 3MHz 30MHz 300MHz 30GHz300GHz 10km 1km 100m 10m 1m 10cm 1cm 100mm 3GHz 9

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 10

Propagation Mechanisms Non Line-of-Sight Reflection λ << D Diffraction λ  D Scattering λ >> D S D Line-of-Sight 11

Propagation in the “Real World” a wave can be absorbed reflect penetrate bend 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 13

Networking as Resource Allocation 14

Resource Allocation 15  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 16  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 17

Fixed Networks 18  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 19 Access Networks Mesh Network Access Networks Mesh Network

Mobile Networks: Circuit Multiplexing 20  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) 21  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

22  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)

23  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

24  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

25 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