EE 552/452 Wireless Communications (and Networks) Lecture Notes 2007 PDF

EE 552/452, Spring, 2007 Wireless Communications (and Networks) Zhu Han Department of Electrical and Computer Engineering Class 6 Feb. 1st, 2007  Outline  Call procedure  Introduct...

EE 552/452, Spring, 2007 Wireless Communications (and Networks) Zhu Han Department of Electrical and Computer Engineering Class 6 Feb. 1st, 2007  Outline  Call procedure  Introduction to radio wave propagation – Free space – Reflection EE 552/452 Spring 2007  Example  Dz/Rz=7, but D/R is 3.  2.33 times capacity gain EE 552/452 Spring 2007  Brief Outline of Cellular Process  Telephone call to mobile user – Step 1 – The incoming telephone call to Mobile X is received at the MSC. – Step 2 – The MSC dispatches the request to all base stations in the cellular system. – Step 3 – The base stations broadcast the Mobile Identification Number (MIN), telephone number of Mobile X, as a paging message over the FCC throughout the cellular system. – Step 4 – The mobile receives the paging message sent by the base station it monitors and responds by identifying itself over the reverse control channel. – Step 5 – The base station relays the acknowledgement sent by the mobile and informs the MSC of the handshake. – Step 6 – The MSC instructs the base station to move the call to an issued voice channel within in the cell. – Step 7 – The base station signals the mobile to change frequencies to an unused forward and reverse voice channel pair. – At the same time, another data message (alert) is transmitted over the forward voice channel to instruct the mobile to ring. EE 552/452 Spring 2007  Telephone Call Placed by Mobile  Step 1 – When a mobile originates a call, it sends the base station its telephone number (MIN), electronic serial number (ESN), and telephone number of called party. It also transmits a station class mark (SCM) which indicates what the maximum power level is for the particular user.  Step 2 – The cell base station receives the data and sends it to the MSC.  Step 3 – The MSC validates the request, makes connection to the called party through the PSTN and validates the base station and mobile user to move to an unused forward and reverse channel pair to allow the conversation to begin. EE 552/452 Spring 2007  Roaming  All cellular systems provide a service called roaming. This allows subscribers to operate in service areas other than the one from which service is subscribed.  When a mobile enters a city or geographic area that is different from its home service area, it is registered as a roamer in the new service area.  Registration – MSC polls for unregistered mobiles – Mobiles respond with MINs – MSC queries mobile’s home for billing info  Calls – MSC controls call and bills mobile’s home EE 552/452 Spring 2007  Speed, Wavelength, Frequency  Light speed = Wavelength x Frequency = 3 x 108 m/s = 300,000 km/s System Frequency Wavelength AC current 60 Hz 5,000 km FM radio 100 MHz 3m Cellular 800 MHz 37.5 cm Ka band satellite 20 GHz 15 mm Ultraviolet light 1015 Hz 10-7 m EE 552/452 Spring 2007  Type of waves EE 552/452 Spring 2007  Radio Frequency Bands Classification Band Initials Frequency Range Characteristics Extremely low ELF < 300 Hz Infra low ILF 300 Hz - 3 kHz Ground wave Very low VLF 3 kHz - 30 kHz Low LF 30 kHz - 300 kHz Medium MF 300 kHz - 3 MHz Ground/Sky wave High HF 3 MHz - 30 MHz Sky wave Very high VHF 30 MHz - 300 MHz Ultra high UHF 300 MHz - 3 GHz Space wave Super high SHF 3 GHz - 30 GHz Extremely high EHF 30 GHz - 300 GHz Tremendously high THF 300 GHz - 3000 GHz EE 552/452 Spring 2007 Large-scale small-scale propagation EE 552/452 Spring 2007  Models are Specialized  Different scales – Large scale (averaged over meters) – Small scale (order of wavelength)  Different environmental characteristics – Outdoor, indoor, land, sea, space, etc.  Different application areas – macrocell (2km), microcell(500m), picocell EE 552/452 Spring 2007  Free space propagation model  Assumes far-field (Fraunhofer region) – d >> D and d >>  , where  D is the largest linear dimension of antenna   is the carrier wavelength  No interference, no obstructions  Black board 4.2  Effective isotropic radiated power  Effective radiated power  Path loss  Fraunhofer region/far field  In log scale  Example 4.1 and 4.2 EE 552/452 Spring 2007  Relating power to Electric Field  Blackboard equations EE 552/452 Spring 2007  Antenna Model  Example 4.3 EE 552/452 Spring 2007  Radio Propagation Mechanisms  Refraction – Conductors & Dielectric materials (refraction) – Propagation wave impinges on an object which is large as compared to wavelength - e.g., the surface of the Earth, buildings, walls, etc.  Diffraction – Fresnel zones – Radio path between transmitter and receiver obstructed by surface with sharp irregular edges – Waves bend around the obstacle, even when LOS (line of sight) does not exist  Scattering – Objects smaller than the wavelength of the propagation wave - e.g. foliage, street signs, lamp posts – “Clutter” is small relative to wavelength EE 552/452 Spring 2007  Refraction  Perfect conductors reflect with no attenuation – Like light to the mirror  Dielectrics reflect a fraction of incident energy – “Grazing angles” reflect max* – Steep angles transmit max* – Like light to the water  Reflection induces 180 phase shift – Why? See yourself in the mirror  r t EE 552/452 Spring 2007  Reflection from smooth surface   0 r  j ' EE 552/452 Spring 2007 Typical electromagnetic properties EE 552/452 Spring 2007  Superposition for polarization  Equation 4.19-4.25 EE 552/452 Spring 2007  Reflection coefficients  Equation 4.26, example 4.4, Brewster angle, perfect conductors EE 552/452 Spring 2007  Classical 2-ray ground bounce model  One line of sight and one ground bound EE 552/452 Spring 2007  Method of image EE 552/452 Spring 2007  Vector addition of 2 rays EE 552/452 Spring 2007  Simplified model  Far field simplified model ht2 hr2  Example 4.6 Pr Pt Gt Gr 4 d EE 552/452 Spring 2007  Questions? EE 552/452 Spring 2007