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 Schedule
8:30 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 Agenda
Day 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

1. Older Systems

Broadcasting

Radar

Satellites

Point-To-Point Microwave

Broadcasting
Aspects
♦ One way communication
• Large geographical area
• High power
♦ Frequency allocation
• Bands
• Channels

Older Systems - Broadcasting

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
Carrier
♦ Information
• 6 MHz
Information

Broadcasting
Tuner
From
♦ Part of the antenna

receiver

Tunable
filter
Tunable
oscillator


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


Radar
RAdio Detecting And Ranging
♦ Uses a reflected RF signal to determine
• Distance
• Direction
• Velocity

Older Systems - Radar

Types & Frequency Allocation
Radar 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


Radar
More Tradeoffs
♦ Power vs size


Radar
How It Determines Velocity
♦ Doppler shift

Frequency 1

Frequency 2


Radar
Applications

Altimeter


Radar
Applications

Near Object Adaptive
Detection (NODS) Cruise Control


Satellites
Why?
♦ Long range
communications

Uplink

Downlink

Older Systems - Satellites

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 Satellites
Footprint
♦ "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 Hardware
1) 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 Satellites
System Principal Status

Spaceway Hughes 2003

Astrolink Lockheed 2003

EuroSkyway Alenia (Italy) ???


Point To Point Microwave
What
♦ Licensed frequency bands
♦ "Microwave relay"
♦ Uses directional "dish"
antennas

Older Systems - Point To Point Microwave

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

Fresnel zone
Distance


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

a th
Refle cted p

Direct path


Multipath
Cure
♦ Signal processing
♦ Antenna diversity
• Spatial diversity


Diversity Review
Different Kinds
♦ Frequency
♦ Antenna (spatial)
♦ Polarization
♦ Temporal (time)


Recap
Broadcasting Carrier frequency vs
Information bandwidth frequency

Radar Distance, direction, velocity
Antenna size vs frequency

Satellites Three topologies
Three orbits: GEO, MEO, LEO

Point-to Point Fresnel zones
Multipath
Diversity

2. Mobile Telephony
Overview Cellular Systems

Air Interfaces CDMA In Depth

Block Diagram The Future

2. Mobile Telephony

Overview Cellular Systems

Air Interfaces CDMA In Depth

Block Diagram The Future

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

Differentiators
Frequency Bands
♦ Multiple bands
♦ Multiple providers per band
Modulation Type
♦ Analog and digital
Air Interface
♦ Dividing up the bands

Mobile Telephony - Overview

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


Cellular Systems
Cellular Division
♦ Frequency
♦ Geography

Mobile Telephony - Cellular Systems

Cellular Systems
US Frequency Allocations


Cellular Systems
"Full Duplex"


Cellular Systems
Band Allocations


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
Rural
Geography Statistical Area
(RSA)

Metropolitan
Statistical Area
(MSA)


Cellular Systems
Cell
Structure

Cellular Systems
Cell Structure

Antenna
pattern

Mobile telephony - Cellular Systems

Cellular Systems
Typical Sector 1
Antenna
Pattern
Sector 3

Sector 2


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 Aspects
1) 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


Cell Infrastructure
Sector antennas
"Basestation"

Equipment hut

Telco
Transmitter
Receiver
Controller

Cable
Power supply Batteries

Cell Infrastructure
Spatial Diversity
♦ To overcome multipath

Multiple receive
antennas


Cell Infrastructure
Transmitter
♦ Filter after the HPA

Cavity filter

Most transmitters Basestation transmitters


Cell Infrastructure
Receiver
♦ Filter before the LNA

Low-loss filter

Most receivers Basestation receivers


Cell Infrastructure
Receiver
♦ Filter after the LNA
Cavity or
Superconducting
filter

Cooled LNA

Most receivers Basestation receivers


Cell Infrastructure
Another Issue

Insertion Loss
5 dB?

Telco

Controller


Cell Infrastructure
A Solution
Tower Top
System

Telco

Controller


Cellular Systems
Adding Capacity
1) 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
Repeater

Macrocell


Adding Capacity
Dead Spots


Adding Capacity
1. Repeaters More cells or repeaters


Adding Capacity
2. Superconducting Filters


Adding Capacity
3. Smart Antennas


Air Interfaces
Five
♦ FDMA
♦ TDMA
♦ CDMA
♦ SDMA
♦ CDPD

Mobile Telephony - Air Interfaces

FDMA
Frequency Division
Multiple Access

FDMA


TDMA
Time Division Multiple Access
♦ Each frequency is divided into time
slots
• 3 - 6 different time slots
• Uses buffering

Mobile Telephony - Aire Interfaces

CDMA
Code Division Multiple Access
♦ Conversations share frequencies & are
distinguished by their "address"


CDMA
♦ The envelope gets addressed

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


SDMA
Smart
Antenna
Pattern

Mobile telephony - Air Interfaces

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)

Noise Spectrum Signal Spectrum

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

Mobile Telephony - CDMA

CDMA
Visually

Narrowband
signal


CDMA
Visually

Spread
signal


CDMA
Graphically


CDMA
Graphically
Spectral density
is 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

XOR
Spreading signal


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


Block Diagram

Mobile Telephony - Block Diagram

The Future
Vision For 3G
♦ Global standard
♦ One frequency
♦ Pure packet-based networks
♦ Bandwidth on demand (up to 2 Mbps)
• IMT-2000

Mobile Telephony - The Future

Roadmap To 3G
AT&T
Cingular

Verizon
Sprint

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


Module 3 - Systems I
The end

Introduction to RF & Wireless - Part 3

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Destaque

Destaque (20)

Semelhante a Introduction to RF & Wireless - Part 3

Semelhante a Introduction to RF & Wireless - Part 3 (20)

Introduction to RF & Wireless - Part 3