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

2. Mobile Telephony

1. Older Systems

Broadcasting

Satellites

Point-To-Point Microwave

1. Older Systems

Broadcasting

Satellites

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

Satellites

Older Systems - 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

How It Determines Distance

Distance = Velocity x Time

How It Determines Direction

Beamwidth

Tradeoffs

Atmospheric

Attenuation

More Tradeoffs Power vs size

How It Determines Velocity Doppler shift

Frequency 1

Frequency 2

Applications

Altimeter

Applications

Near ObjectDetection (NODS)

AdaptiveCruise Control

1. Older Systems

Broadcasting

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

How It Works

Distance = Velocity x Time

How It Works

Satellites

LEO Low Earth Orbit

• Low power

• No time delay

• Telephony

• Internet

How It Works: Approach 1

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

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

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

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

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

Cellular Systems

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

One Upstream Band

Solution Divide up the band

• Frequency Division Multiple Access (FDMA)

• An air Interface

Cellular Systems

Geography

MetropolitanStatistical Area

RuralStatistical Area

Cellular Systems

Topology

Cellular Systems

Structure

Mobile telephony - Cellular Systems

Cellular Systems

Cell Structure

Antennapattern

Cellular Systems

Cell Structure

Antennapattern

Cellular Systems

Typical

Antenna

Pattern

Sector 1

Sector 2

Sector 3

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

Mobility

Handoff

Maximum data rate depends on speed

Cellular Systems

Infrastructure Area Cell Transmitter/Receiver Adding capacity

Area Infrastructure

Cell Infrastructure

"Basestation" Sector antennas

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

Controller

Insertion Loss5 dB?

Cell Infrastructure

A Solution

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

Frequency Division

Multiple Access

Mobile Telephony - Aire Interfaces

Time Division Multiple Access Each frequency is divided into time

slots• 3 - 6 different time slots• Uses buffering

TDMA + FDMA

Code Division Multiple Access Conversations share frequencies & are

distinguished by their "address"

CDMA The envelope gets addressed

CDMA + FDMA

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

Mobile telephony - Air Interfaces

Antenna

Pattern

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

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

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

Visually

Narrowbandsignal

Visually

Spreadsignal

Graphically

Spectral densityis constant

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

What Is Spreading Another modulation

• Much higher frequency

• Chipping rate

Data signal

Spreading signal

This Kind Of Spreading Direct sequence spread spectrum (DSSS)

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

• Random

• Pseudo

Every user has their own unique PN signal

Spreading Example

De-Spreading

Where Does De-Spreading Occur

De-Spreading Example

Receiving Someone Else's Signal

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

introduction to rf & wireless - part 3

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