introduction to rf & wireless - part 3

Why are 1988 pennies worth more than 1983 pennies?

Introduction to RF & Wireless

Two Day Seminar

Module 3

Daily Schedule8:30 am – 10: 00 am Fun

10:00 am – 10:15 am Break

10:15 am – 11:45 am Fun

Noon – 1:00 pm Lunch

1:00 pm – 2:30 pm Fun

2:30 pm – 2:45 pm Break

2:45 pm – 4:15 pm Fun

Course AgendaDay One

• Morning (Module 1)– Introduction to RF

• Afternoon (Module 2)– RF hardware

Day Two• Morning (Module 3)

– Older systems & mobile telephony

• Afternoon (Module 4)– Newer systems & the future

Module 3 - Systems I

1. Older Systems

2. Mobile Telephony

1. Older Systems

Broadcasting

Radar

Satellites

Point-To-Point Microwave

Older Systems - Broadcasting

Broadcasting

Aspects One way communication

• Large geographical area

• High power

Frequency allocation• Bands

• Channels


Broadcasting

US Band Allocations


Broadcasting

US Channel Allocations

Service Channel Allocatiion

AM Radio 10 KHz

FM Radio 200 KHz

Television 6 MHz

Broadcasting

Signal Carrier

• 181 MHz

Information• 6 MHz

Carrier

Information


Broadcasting

Tuner Part of the

receiver

Tunableoscillator

Tunable filter

Fromantenna


Broadcasting

Before The

Filter


Broadcasting

After The

Filter


Broadcasting

After The

Mixer Baseband

0-6 MHz


Broadcasting

One Problem Line of sight

• Receiver must be able to "see" transmitter

• Antenna may have to be readjusted

• Tall buildings may cause ghosts

• Earth's curvature is a limitation

1. Older Systems

Broadcasting

Radar

Satellites


Older Systems - Radar

Radar

RAdio Detecting And Ranging Uses a reflected RF signal to determine

• Distance

• Direction

• Velocity


Types & Frequency AllocationRadar Band Frequency Uses

UHF 200 MHz Early warning

VHF 400 MHz Satellite

L-band 1000 MHz Air traffic control

S-band 2 GHz Shipboard

C-band 5 GHz Altimeter

X-band 10 GHz Weather, police

Ku-band 14, 15 GHz Airborne fighter


Radar

How It Determines Distance

Distance = Velocity x Time


Radar

How It Determines Direction


Radar

Beamwidth

Tradeoffs

Atmospheric

Attenuation


Radar

More Tradeoffs Power vs size


Radar

How It Determines Velocity Doppler shift

Frequency 1

Frequency 2


Radar

Applications

Altimeter


Radar

Applications

Near ObjectDetection (NODS)

AdaptiveCruise Control

1. Older Systems

Broadcasting

Radar

Satellites


Older Systems - Satellites

Satellites

Why? Long range

communications

Uplink

Downlink


Satellites

Where Geosynchronous Orbit (GEO)

• Approximately 22,000 miles up

• Only at the equator


GEO Satellites

Band Frequency Allocation

C-band downlink 3.7 – 4.2 GHz

C-band uplink 5.925 – 6.425 GHz

Ku-band downlink 11.7 – 12. 2 GHz

Ku-band uplink 14.0 – 14. 5 GHz

Ka-band downlink 27.5 –29.5 GHz

Ka-band uplink 29.5 – 31.0 GHz


GEO SatellitesFootprint

"Antenna pattern"• CONUS


GEO Satellites

3 Topologies Point to point

• Telephony, backhaul


GEO Satellites

3 Topologies Point to multipoint

• Direct to home (DTH) TV


GEO Satellites

3 Topologies Multipoint to point

• VSAT


GEO Satellites

Spacecraft Hardware1) Antennas

2) Transponders


GEO Satellites

Spacecraft Antennas Frequency vs size tradeoff

• Ku-band must be CONUS


GEO Satellites

Transponders "Bent pipe"


Satellites

Ground Hardware Dish antennas

• "Funnel reflectors"


Satellites

Dish Antennas Bigger the dish = higher the power

• Transmitting• Receiving


Satellites

GPS Global Positioning System

• Run by DOD

• 24 satellites

• Medium Earth Orbit (MEO)

• Used to determine location


GPS

How It Works

Distance = Velocity x Time


GPS

How It Works


Satellites

LEO Low Earth Orbit

• Low power

• No time delay

• Telephony

• Internet


LEO

How It Works: Approach 1


LEO

How It Works: Approach 2

Local Earth station


LEO Constellations

System # Sats Principal Status

Skybridge 80 Alcatel Delayed

Globalstar 48 Loral Working

Teledesic 288 Lockheed 2005

Iridium 66 Motorola Dead

ICO Global 12* McCaw 2003


Satellites

Next Generation GEO Two way Ka-band

• Spot beams• Internet


Satellites

Next Generation Pluses

• Internet + programming

Minuses• Expensive satellites

• Susceptible to rain fade

• Time delay


Ka Band SatellitesSystem Principal Status

Spaceway Hughes 2003

Astrolink Lockheed 2003

EuroSkyway Alenia (Italy) ???

1. Older Systems

Broadcasting

Radar

Satellites


Older Systems - Point To Point Microwave

Point To Point Microwave

What Licensed frequency bands "Microwave relay" Uses directional "dish"

antennas


Point To Point Microwave

Uses Voice backhaul Video backhaul

Limitations Line of sight Fresnel zones Multipath


Fresnel Zones

What Elliptical areas Contain much of the RF energy Result of using dish antennas Size is a function of

• Distance• Frequency


Fresnel Zones

Visual Depiction

RF energy


Fresnel Zones

Visual Depiction

DistanceFresnel zone


Fresnel Zones

Consequences


Fresnel Zones

Cure High

antennas


Multipath

What A result of reflection Transmitted signal can take multiple paths to

receiver Signals may be out of phase


Multipath

Visual Depiction

Direct path

Reflected path


Multipath

Cure Signal processing Antenna diversity

• Spatial diversity


Diversity Review

Frequency Antenna (spatial) Polarization Temporal (time)

Different Kinds

Recap

Broadcasting Carrier frequency vsInformation bandwidth frequency

Radar Distance, direction, velocityAntenna size vs frequency

Satellites Three topologiesThree orbits: GEO, MEO, LEO

Point-to Point Fresnel zonesMultipathDiversity

Older Systems

The end


1. Older Systems

2. Mobile Telephony

2. Mobile Telephony

Overview Cellular Systems

Air InterfacesCDMA In Depth

Block Diagram The Future

2. Mobile Telephony

OverviewCellular Systems



Current Worldwide Systems

United States AMPS, D-AMPS, SMR, CDMA, PCS

• 800 MHz, 900 MHz, 1900 MHz

Europe NMT, TACS, GSM, DCS

• 450 MHz, 900 MHz, 1800 MHz

Japan JTACS, PDC

• 800 MHz, 1500 MHz

Mobile Telephony - Overview

Differentiators

Frequency Bands Multiple bands Multiple providers per band

Modulation Type Analog and digital

Air Interface Dividing up the bands


Generations

1G

2G

2.5G

3G

4G


Future Differentiators

Switching Type Circuit vs packet

Offerings Voice through multimedia

Data Rate 14 Kbps to 2 Mbps


A Quick Comparison

1G 2G 2.5G 3G

Modulation Analog Digital Digital Digital

Switching Circuit Circuit Circuit/Packet Packet

Offerings Voice Messaging Internet Multimedia

Data Rate - 14 Kbps 144 Kbps 384 Kbs – 2 Mbps

2. Mobile Telephony




Mobile Telephony - Cellular Systems

Cellular Systems

Cellular Division Frequency Geography


Cellular Systems

US Frequency Allocations


Cellular Systems

"Full Duplex"


Cellular Systems

Band Allocations

Band Allocations

Upstream

One Upstream Band

Problem Too much bandwidth

One Upstream Band

Solution Divide up the band

• Frequency Division Multiple Access (FDMA)

• An air Interface


Cellular Systems

Geography

MetropolitanStatistical Area

(MSA)

RuralStatistical Area

(RSA)

Cellular Systems

Topology

Cellular Systems

Cell

Structure

Mobile telephony - Cellular Systems

Cellular Systems

Cell Structure

Antennapattern


Cellular Systems

Typical

Antenna

Pattern

Sector 1

Sector 2

Sector 3

Recap

CELLULAR DIVISION

Frequency Upstream & downstream

Streams Bands (different providers)

Bands Individual calls (FDMA)

U.S. MSAs & RSAs

Areas Cells

Cells Sectors


Cellular Systems

Unique Aspects1) Frequency reuse

2) Mobility

3) Low power


Frequency Reuse

What The ability to use the

same frequency more than once, at the same time, in an MSA or RSA


Frequency Reuse

Cell Spacing Depends on S/N ratio Varies from 4 to 21


Mobility

What Is It The ability to change the receiver you

communicate with as you move• Handoff


Handoff

How All basestations periodically transmit a pilot signal

• Cell phone uses power discrimination

Pilot Pilot


Handoff

How Cell phone requests handoff

• Uses access signal

Access


Mobility

Handoff


Mobility

Handoff

Maximum data rate depends on speed


Cellular Systems

Infrastructure Area Cell Transmitter/Receiver Adding capacity

Area Infrastructure

Cell Infrastructure

"Basestation" Sector antennas

Cable

Equipment hut

Power supply Batteries

Receiver

TransmitterTelco

Controller


Cell Infrastructure

Spatial Diversity To overcome multipath

Multiple receiveantennas


Cell Infrastructure

Transmitter Filter after the HPA

Most transmitters Basestation transmitters

Cavity filter


Cell Infrastructure

Receiver Filter before the LNA

Most receivers Basestation receivers

Low-loss filter


Cell Infrastructure

Receiver Filter after the LNA

Most receivers Basestation receivers

Cavity orSuperconducting

filter

Cooled LNA

Cell Infrastructure

Another Issue


Telco

Controller

Insertion Loss5 dB?

Cell Infrastructure

A Solution


Telco

Controller

Tower TopSystem


Cellular Systems

Adding Capacity1) Within a cell

2) Areas without coverage in an MSA or RSA


Adding Capacity

Within A

Macrocell


Adding Capacity

Microcells

Picocells


Adding Capacity

Areas Without Coverage In buildings In tunnels Obstructed areas Fringe areas Dead spots


Adding Capacity

Use Repeaters

Macrocell

Repeater


Adding Capacity

Dead Spots


Adding Capacity

1. Repeaters More cells or repeaters


Adding Capacity

Dead Spots


Adding Capacity

2. Superconducting Filters


Adding Capacity

Dead Spots


Adding Capacity

3. Smart Antennas

2. Mobile Telephony




Mobile Telephony - Air Interfaces

Air Interfaces

Five FDMA TDMA CDMA SDMA CDPD

FDMA

Frequency Division

Multiple Access


FDMA

Mobile Telephony - Aire Interfaces

TDMA

Time Division Multiple Access Each frequency is divided into time

slots• 3 - 6 different time slots• Uses buffering

TDMA + FDMA


CDMA

Code Division Multiple Access Conversations share frequencies & are

distinguished by their "address"

CDMA The envelope gets addressed

CDMA + FDMA


SDMA

Spatial Division Multiple Access Subdividing cell sectors into subsectors Uses smart antennas

Mobile telephony - Air Interfaces

SDMA

Smart

Antenna

Pattern


CDPD

Cellular Digital Packet Data Used for data only (no voice) Uses unused frequencies and unused time slots

Recap

FDMA Divides a frequency band into sub-bands

TDMA Divides a sub-band into time slots

CDMA Overlapping conversations, unique addresses

SDMA Divides an antenna sector into subsectors

CDPD Uses unused frequencies & time slots (data only)

2. Mobile Telephony


Air Interfaces

CDMA In Depth


Noise Spectrum Signal Spectrum

Mobile Telephony - CDMA

CDMA

What Takes the energy contained in a narrowband

signal and spreads it over a larger bandwidth• Spread spectrum

As a consequence, the power level drops• It appears to be noise


CDMA

Visually

Narrowbandsignal


CDMA

Visually

Spreadsignal


CDMA

Graphically


CDMA

Graphically

Spectral densityis constant


CDMA

Why Spread Spread signals drop down into the noise Noise is noise Up to a point, noise signals can be piled on top

of each other without effecting anything


Spreading

Where Does Spreading Occur


CDMA

What Is Spreading Another modulation

• Much higher frequency

• Chipping rate

Data signal

Spreading signal

XOR


CDMA

This Kind Of Spreading Direct sequence spread spectrum (DSSS)

XOR


CDMA

Spreading Signal Spreading signal is a pseudo random Noise (PN) signal

• Random

• Pseudo

Every user has their own unique PN signal


CDMA

Spreading Example


De-Spreading

Where Does De-Spreading Occur


CDMA

De-Spreading Example


CDMA

Receiving Someone Else's Signal


CDMA

PN Signals One continuous looping signal

• Everyone uses the same looping signal, BUT

• They start at a different point in the loop

Must be synchronized• Basestation to cell phone

• Basestation to basestation


PN Synchronization

How GPS

Voice + Synch + Pilot

2. Mobile Telephony




Mobile Telephony - Block Diagram

Block Diagram

2. Mobile Telephony



Block Diagram

The Future

Mobile Telephony - The Future

The Future

Vision For 3G Global standard One frequency Pure packet-based networks Bandwidth on demand (up to 2 Mbps)

• IMT-2000

Roadmap To 3GAT&T

Cingular

VerizonSprint


The Future

Problems On The Road To 3G No global standard Multiple frequencies Ground up vs upgrade Real world vs the lab How to make money


The Future

3G To Date 3G services vs 3G networks Asia

• i-Mode in Japan

Europe• Under construction

US• 2003-2007


The Future

What About 4G Improved modulation Smart antennas >2 Mbps Video on demand Pure IP 2006 - 2010

Mobile Telephony

The end


The end

introduction to rf & wireless - part 3

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