References q A Kumar D Manjunath and J

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

Contents n n n n n 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) 3

Wired Vs. Wireless Communications Wired Wireless Each cable is a different channel One media shared by all Low signal attenuation High signal attenuation No interference High interference noise; co-channel interference; adjacent channel interference 4

Why Wireless? Ø Advantages • Sometimes it is impractical to lay cables • User mobility • Cost Ø Limitations • • Bandwidth Fidelity Power Security 5

Propagation Principle electric field propagation direction magnetic field 6

Electromagnetic Spectrum ISM band 30 k. Hz 10 km 1 km TV ce llu la r di TV FM ra ra W S/ MF 300 k. Hz o o di ra AM LF 902 – 928 Mhz VHF HF 3 MHz 30 MHz 100 m 10 m 2. 4 – 2. 4835 Ghz 5. 725 – 5. 785 Ghz UHF 300 MHz 1 m SHF 3 GHz EHF 30 GHz 300 GHz 1 cm 100 mm 10 cm X rays infrared visible UV 1 k. Hz 1 MHz 1 GHz 1 THz 1 PHz Gamma rays 1 EHz Propagation characteristics are different in each frequency band. 7

Unlicensed Radio Spectrum (ISM: Industrial, Science, Medicine) 33 cm 26 Mhz 902 Mhz 12 cm 83. 5 Mhz 2. 4 Ghz 928 Mhz cordless phones baby monitors Wave. Lan 2. 4835 Ghz 802. 11 b Bluetooth Microwave oven 5 cm 125 Mhz 5. 725 Ghz 5. 850 Ghz 802. 11 a 8

Propagation Mechanisms Line-of-Sight S D Non Line-of-Sight Reflection Diffraction λ << D λ D Scattering λ >> D 9

Propagation in the “Real World” a wave can be absorbed penetrate reflect bend 10

Path-loss Models Ø Path-Loss Exponent Depends on environment: n L(d) = L(d 0)(d/d 0) Free space Urban area cellular Shadowed urban cell In building LOS Obstructed in building Obstructed in factories n n n = = = 2 2. 7 to 3. 5 3 to 5 1. 6 to 1. 8 4 to 6 2 to 3 11

Networking as Resource Allocation

Resource Allocation Ø 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 Ø Wireless o Point-to-point Line-of-sight (same as wireline or higher bit rate) o Time-varying channel impairments o Adaptable PHY layer

Wireless Networking Ø 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 (Qo. S).

Wireless Networks

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

Mobile and Ad-hoc Networks Access Networks Mesh Network

Mobile Networks: Circuit Multiplexing Ø GSM (2 G) o Narrowband FDM-TDMA High SINR Careful frequency planning to avoid cochannel interference o Call admission control o o o ü GSM-GPRS (2. 5 G) Combining TDM Time slots ü GSM-EDGE (2. 75 G) Combining TDM Time slots and higher order modulation schemes

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

Mobile Networks: Centralized Statistical Multiplexing (2) Ø Wi. MAX o o (IEEE 802. 16 series) Wireless access to Internet Fixed subscriber stations OFDMA TDD (uplink & downlink) o Specifications now have been extended to include broadband access to mobile users.

Mobile Networks: Distributed Statistical Multiplexing Ø WLAN (IEEE 802. 11 series) Wireless access to Internet Limited mobility Statistical TDMA Few Mbps (over 100 s of meter) up to 100 Mbps (over a few meters) o MIMO-OFDM (enhancement) o o

Ad hoc Networks: Internet Access and Sensor Networks Ø Ø Ø 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

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