introduction to rf & wireless - part 4

Introduction to RF & Wireless

Two Day Seminar

Module 4

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 4 - Systems 2

1. Broadband Fixed Wireless

2. Wireless Networks

3. Mobile Internet

4. The Future


Choices

Air Link Transmission Technologies

Broadband Fixed Wireless - Choices

Local Loop

Telephonelocal loop

Cablelocal loop

Wirelesslocal loop


Local Loop

Broadband Fixed Wireless Exists to compete in the local loop Used primarily for Internet access Line of sight is an issue Multipath is an issue Two configurations Four choices


Configurations

Point-To-Point


Configurations

Point-To-Multipoint


Choices

Broadband Fixed Wireless MMDS LMDS Unlicensed Wireless fiber


MMDS

Multichannel Multipoint

Distribution Service Licensed 2.6 GHz 2 Mbps Point-to-multipoint 35 miles


LMDS

Local Multipoint

Distribution Service Licensed 31GHz 155 Mbps Point-to-point 3 miles

Atmospheric

Attenuation


Unlicensed

Unlicensed Spread Spectrum No license required ISM frequency bands ??? Mbps Point-to-point and point-to-multipoint ??? miles


ISM Frequency Bands

Overview 900 MHz, 2.4 GHz, 5.8 GHz Industrial, scientific, medical equipment 100s of MHz of bandwidth Limited output power Must use spread spectrum Open usage


Unlicensed

Good News No license required

Bad News Interference from non-RF items Interference from RF items Interference from competitors Limited output power


UnlicensedTypical

Deployment

ISP

Pt to Pt

Pt to Multipoint2.4 GHz

5.8 GHz


Unlicensed

Other Issues Inexpensive RF hardware Expensive customer premises equipment (CPE) Questionable market acceptance

• Businesses

• Single family homes

• MDUs and MTUs


Wireless Fiber

Free Space Optics Unlicensed Infrared frequency 622 Mbps Point to point Less than 1 mile


Wireless Fiber Transceiver


Wireless Fiber

Other Issues Data rates compete with fiber Adversely effected by rain and fog Well defined market

• Campuses

• Building to building

• Emergency bandwidth

Recap

MMDS LMDS Unlicensed WirelessFiber

Frequency 2.6 GHz 31 GHz 900 MHz2.4/5.8 GHz

10,000 THz

Configuration PmP P2P P2PPmP

P2P

Range 35 miles 3 miles 25 miles5 miles

< 1 mile

Data Rate 2 Mbps 155 Mbps 1 Mbps100 Mbps

622 Mbps


Choices


Braodband Fixed Wireless - Air Link Transmission Technologies


Challenge Some wireless services are allocated a single

lump of frequency• Unlike cellular

How to do two-way communications


Two Way Communications

Simplex One frequency One party transmits at a time

• Walkie-talkies

Frequency 1

Frequency 1



Half Duplex Two frequencies One party transmits at a time

• Wireless LANs

Frequency 1

Frequency 2



Full Duplex Two frequencies Both parties can transmit at the same time

• Cellular phones

Frequency 1

Frequency 2



What To make optimum use of available bandwidth To overcome transmission problems

Choices FDD TDD OFDM


FDD

Frequency Division Duplexing Dividing the allotted frequency into sub-bands Each sub-band has a designated direction


FDD

ISM band


FDD


FDD + FDMA


TDD

Time Division Duplexing Dividing the allotted frequency into time slots Each time slot goes in one of two directions


TDD

ISM band


TDD


Multipath Is A Problem

Direct path

Reflected path

So Is Line Of Sight

Direct path

Reflected path


OFDM

Orthogonal Frequency Division Multiplexing Solves multipath Deals with Non-Line Of Sight (NLOS) situations

How By dividing up a broadband signal into multiple signals

• Which slows it down


OFDM

Visually

OFDM Example

RecapWhat Comments

FDD Divides a frequency bandinto sub-bands for two-waycommunications

Good for telephony

TDD Divides a frequency bandinto time slots for two-waycommunictions

Optimum use ofbandwidth

OFDM Divides a broadband signalinto multiple narrowbandsignals

To overcomemultipath and NLOS

Broadband Fixed Wireless

The end




3. Mobile Internet

4. The Future


Local Area Networks

Personal Area Networks

Home Networks

Wireless Networks - Local Area Networks

Local Area Networks (LAN)

Parameters Limited area

• Floor or campus

Some mobility• Walking around

Server centric


Basic Architecture


Basic Architecture

Basic Service Set BSS


Basic Architecture

BSSBSS

Extended Service Set


Access Point


Local Area Networks

Frequency Unlicensed bands

• ISM bands

Air Interface Mostly Spread spectrum

• Direct sequence

• Frequency hopping


FHSS

Frequency Hopping Spread Spectrum Uses a PN signal to generate a series of

random carrier frequencies• Transmitter and receiver use the same PN signal


FHSS


FHSS

How


Comparison

FHSS vs DSSS FHSS has better noise immunity DSSS has higher instantaneous bandwidth

• 10 MHz vs 1 MHz

FHSS deals better with multipath

Choices

802.11 Originated in the US Based in Ethernet Shared frequency

HiperLAN Originated in Europe Based in GSM Unique frequency


DetailsSystem Band Data Rate Technology

802.11 2.4 GHz 2 Mbps FHSS or DSSS

802.11b 2.4 GHz 11 Mbps DSSS + CCK

802.11a 5.8 GHz 54 Mbps OFDM

HiperLAN 5.8 GHz 20 Mbps GMSK

HiperLAN II 5.8 GHz 50 Mbps OFDM

Wi Fi


Local Area Networks


Home Networks

Wireless Networks - Personal Area Networks

Personal Area Networks (PAN)

Parameters Unlimited area

• Where ever you go

Some mobility• Walking around

Person centric• You become the AP



Requirements Interoperability

• Mobiles talking to mobiles

Short range• Low power/low interference

Self discovery• Auto initiate



Applications Impromptu

networks

Piconet



Applications Cell phone as wireless modem


PAN Standards

Bluetooth Developed by Ericsson (Sweden) Based on 802.11 Voice + data Designated 802.15 Internationally accepted standard &

frequency


BluetoothParameter Specification

Data Rate 1 Mbps

Range 30 feet

Frequency 2.4 GHz

Technology FHSS

2.4 GHz Redux

Who Uses 2.4 GHz Microwave ovens Cordless phones Broadband fixed wireless providers Wireless networks Bluetooth networks


Local Area Networks


Home Networks

Wireless Networks - Home Networks

Home Networks

Two Systems HomeRF

• For the home

IrDA• For the home and the office


HomeRF

Parameters Limited area

• The home

Some mobility• Within the home

Home centric• Information appliances


HomeRF

Requirements Low cost

• Consumer market

Versatile• Data, voice, audio, video

Interoperability• 802.11 + DECT

HomeRF Vision


Infrared Data Association (IrDa)

Parameters Very limited area

• A few feet

Almost no mobility• A few inches

Decentralized• Point to point


IrDa

Description An industry standard

• For data only

• Uses infrared light

• Good for about 3 feet

Embedded in most gadgets


IrDA

Applications Wireless synching


IrDA

Applications Upload digital photos

Network Comparison

802.11b Bluetooth HomeRF IrDA

Frequency 2.4 GHz 2.4 GHz 2.4 GHz IR

Technology DSSS FHSS FHSS IR

Range 300 feet 30 feet 150 feet 3 feet

Data Rate 11 Mbps 1Mbps 1.6 Mbps 4 Mbps

Voice None Some Good None

No of nodes 127 8 127 2

Recap

Area Mobility Center

LAN Floor Walking Server

PAN Everywhere Walking Person

Home RF Home Walking Home

IrDA Few feet None Decentralized

Wireless Networks

The end




3. Mobile Internet

4. The Future

Mobile Internet

Wireless Internet

Mobile Internet - Technology

Mobile Internet

Defined Mobile devices

• Cell phones, PDAs, laptops

Wide area• City, state, country

High mobility• Driving around speed


Mobile Internet

Challenges Data rate

• Depends on the device

Screen size• Different content

Ubiquity• I want it everywhere


Mobile Internet Candidates

Cellular LEOsISM


Mobile Internet Candidates

PROS CONS

Cellular Existing infrastructureExisting customer base

Not much bandwidthNeed a license

ISM Lots of bandwidthNo license required

Build from the ground upLimited power

LEOs Use it anywhereHeavy frequency reuse

Very expensive buildoutRequires more power


Mobile Internet

Infrastructure Changes Wireless portion Internet portion


Mobile Internet

Wireless Infrastructure Changes Mobile switching center

• Gateway for separating voice from data

• Packet switching

Mobile device• Microbrowser


Mobile Internet

Packet Switching Shared access to a given channel More efficient use of spectrum Better for bursty (Internet) traffic Higher instantaneous data rates


Mobile Internet

Internet Infrastructure Changes New markup language

• C-HTML (web guys)

• WML (phone guys)

Multiple servers (possibly)• Unique content

New protocols• WAP (non-proprietary)

Mobile Internet

Visually

Mobile Internet - WAP

WAP

Wireless Access Protocol1) Wireless Markup Language (WML)

• No tables, frames, other fancy stuff

2) Protocols• WDP (wireless datagram protocol)

• WTP (wireless transaction protocol)

• WSP (wireless session protocol)


WAP

Infrastructure WAP gateways

• Remote access server for WAP

• wap.company.com

WAP servers• Stores WAP data

• Some translate pages on the fly

WAP

Visually

WAP WAPServer


WAP

Works Over all technologies

• Mobile telephony

• Bluetooth

Over all frequencies• Cellular

• PCS

• ISM

Mobile Internet - M-Commerce

M-Commerce

Mobile Commerce A trillion dollar business (some day) Take advantage of unique aspects of mobility Not meant to replace e-commerce

Mobile Internet - M-Commerce

M-Commerce

Possibilities Comparison shopping Location-specific services Advertising Financial transactions Entertainment

Mobile Internet - Status

Mobile Internet

Status Cellular

• i-Mode in Japan

ISM• Ricochet died

LEOs• Stay tuned

Mobile Internet

The end




3. Mobile Internet

4. The Future

4. The Future

New Technologies

Security Issues

Health Concerns

The Future - New Technolgoies

New Technologies

Five1) Ultrawideband

2) MEMS

3) BLAST

4) RFID

5) Telematics


Ultrawideband

What Periodic single sine wave

• Monocycle

Covers multiple licensed bands• Must not interfere

Not yet approved by the FCC


Ultrawideband

Visually

Monocycles


Ultrawideband

Problem

Same frequency


Ultrawideband

Result


Ultrawideband

What If

Time hopping spread spectrum


Ultrawideband

Result


Ultrawideband

One More Problem A single sine wave contains no information

• Where's the modulation?


Ultrawideband

What If


MEMS

MicroElectroMechanical Systems Semiconductors that can physically move

• Superior electrical properties

• Low cost manufacturing (in volume)

Switch Comparison

PIN Electromechanical MEMS

Insertion loss 1 dB 0.1 dB 0.1 dB

Switching speed Microsec Millisec Microsec

Size Small Big Tiny

Power Moderate Substantial Tiny

Price Low High Very low


BLAST

Bell Labs LAyered Space Time Dramatically increased data rate Send multiple signals over one frequency

• Takes advantage of multipath

More of a signal processing trick


BLAST


RFID

Radio Frequency IDentification Control, detect and track objects Uses unique numerical codes Not a new technology (1980s) Ubiquitous


RFIDSystem

Interrogator Transponder ("Tag")

TransponderInterrogator

Tx

Rx

Tx

Rx

Numericalcode


RFID

Types Of Transponders Active

• Onboard power source (i.e., battery)

Passive• No onboard power source

• Receives power from the transponder

RFID ComparisonActive Passive

Transponderpower source

Battery Interrogator

Interrogatorouptut power

Low High

Range 250 feet 1.5 feet

Frequency ISM Low frequency

Numerical code Re-programmable Factory programmed


RFID

Applications Inventory tracking Toll road readers Cashless payments Electronic article surveillance

The Future - New Technologies

Telematics

What Using position-locating technology for value-

added automobile services• OnStar™

4. The Future

New Technologies

Security Issues

Health Concerns

The Future - Security Issues

Wireless Security

Unique Challenges Mobile devices Limited computing power Limited bandwidth Interface weakness


Wireless Security

Some Solutions Point to point systems Encryption

Point-To-Multipoint

Recall


Smart Antennas

A Better Solution


Encryption

Two Protocols Wired Equivalent Privacy (WEP)

• For use with 802.11 networks

• Weakness: Shared key

Wireless Layer Transport Security (WLTS)• For use with WAP

• Weakness: Wireless-wired interface


Encryption

How Is It Done Just like DSSS PN replaced by encryption key

Data signal

Encryption key

4. The Future

New Technologies

Security Issues

Health Concerns

The Future - Health Concerns

Health Concerns

Status Evidence inconclusive Results statistical in nature


Adverse Health Effects

Two 1) Ionization

• Molecular changes

2) Thermal• Body heating


Health Concerns

RF Factors Effecting Heating Frequency

• It depends

Power density• High is bad

Time of exposure• Long is bad


Frequency

Bad Frequencies 30 -300 MHz

• Most efficient absorption by body

2.4 GHz• Efficient absorption by water


Power Density

In Perspective 100 mW/cm2 = microwave oven 1 mW/cm2 = measurable body heating 1 W/cm2 = at the bottom of a cell tower


Time

Key Issue Can the body dissipate the heat

• Depends on blood flow

• Some areas more vulnerable than others


FCC

Exposure Guidelines Whole body

• Power density (mW/cm2)

• Averaged over 30 minutes

Partial body• Specific absorption rate (W/Kg)

• 1.6 W/Kg maximum


The Bottom Line

You're more likely to be injured in a car crash

while you're talking on your cell phone than you are from its RF radiation

The Future

The end

Module 4 -Systems 2

The end

Good

introduction to rf & wireless - part 4

Documents

wireless services

wireless networks3

time wireless lans frequency

broadband signal

allotted frequency

singlelump of frequency

ism frequency bandsoverview

time cellular phones