ECE 250: Wireless Communications and Networking Lecture 1

Computer Science Electrical Engineering OSI Model PHYLinkNetworkApplicationSpectrum

Why go wireless ? Advantages  Sometimes it is impractical to lay cables  User mobility  Cost Limitations  Bandwidth  Fidelity  Power  (In)security

Wired Vs. Wireless Communication WiredWireless Low interference (Cross-talk) Each cable is a different channelOne media (cable) shared by all Signal attenuation is low High signal attenuation High interference noise; co-channel interference; adjacent channel interference

Wireless Systems: Range Comparison Satellite Links SW Radio MW Radio FM Radio Mobile Telephony, WLL WLANs Blueooth IR 1,000 Km100 Km10 Km1 Km100 m10 m1 m

Cellular Systems

Growth of Cellular Subscribers

Cellular System Evolution

Understanding wireless communication How does signal propagate ? How much attenuation take place ? How does signal look like at the receiver ? Tx Rx

EM 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

Radio Propagation Three basic propagation mechanisms Propagation effects depend on not only on the specific portion of spectrum used for transmission, but also on the bandwidth (or spectral occupancy) of the signal being transmitted Spatial separation of Tx-Rx Reflection λ << D Diffraction λ  D Scattering λ >> D

Propagation The higher frequencies will usually encounter more “loss” in “real world” situations EE

Path loss in dB 1  W d2 10 W source d1 1 mW Power dB = 10 log (----) P 1 P 2 Path loss from source to d2 = 70dB 1,000 times 40 dB 30 dB 10,000 times

The Cluttered World of Radio Waves walls hallways windows trees vehicles rain hills girders

Wireless Networks Wireless Internet access Nth generation Cellular Wireless Ad Hoc Networks Sensor Networks Wireless Entertainment Smart Homes/Spaces Automated Highways All this and more… Ubiquitous Communication Among People and Devices