EECS 380: Wireless Communications Week 1

1
EECS 380 Wireless CommunicationsWeek 1
Michael L. Honig Department of EECS Northwestern
University
March 2007
2
Outline

• Background and history
• Overview of current wireless services and
  standards
• Whats on the horizon?

3
Outline

• Background and history
• Overview of current wireless services and
  standards
• Whats on the horizon?

4
Early Digital Wireless Communications
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What is Wireless?
Examples of wireless communications systems
1. Garage door openers 2. Remote controllers
(TV, VCR, etc.) 3. Walkie-talkies 4. Broadcast
TV, radio 5. Police radio, dispatch 6. Telemetry
(RF tags) 7. Amateur radio, CB
8. Satellite systems 9. Pagers 10. Cordless
telephones 11. Cellular 12. Wireless Data (data
entry, messaging, email, internet) 13.
Wireless Local Area Networks (LANs) 14.
Wireless Personal Area Networks (PANs)
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Wireless Information Networks (8-14)

• Properties
• Mobility or portability (tetherless
  communications)
• Access to network resources
• - Public Switched Telephone Network (PSTN)
• - Internet
• - Local Area Network

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Cellular Subscribers
8
Subscriber Growth (cont.)
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Market Trends

• Both cellular and cordless have experienced very
  rapid growth (gt30 per year during the late 90s)
• Number of subscribers exceeds 2 billion.
• GSM 1.8 B CDMA2000 280 M WCDMA 63 M
  (rapidly growing)
• Income of wireless industry exceeds income of
  wired telephone industry
• Dominated by cellular revenues.
• Penetration exceeds 30 in Europe (and U.S.?)
• Wireless penetration expected to equal wireline
  penetration in 15 years
• Future growth will probably depend on new
  services.
• Broadband wireless internet access
• Voice over IP

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Why So Much Growth ?

• Technological advancements
• VLSI microprocessors, Digital Signal Processors
  (DSPs)
• Low power Radio Frequency (RF) circuits
• Signal processing algorithms
• (voice compression)
• Rechargeable batteries
• System concepts
• Cellular networks
• Coding/modulation
• Multiple-access
• Networking advancements
• Stored program (computer-controlled)
  call-setup/switching
• Digital control of wireless links(channel
  assignment, handoff, call setup)

• Market demand
• Higher productivity
• (mobile office)
• Increased dependence on
• email, PC applications

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Communications Evolution
User applications
Games Network computing
Text files
Multi-media
Images
Business data
Entertainment Information access
Video Conference
voice
Broadband Wireless, 4G cellular Ultra-wideband
Wireless
AMPS Cellular 1983
Digital Cellular, CDMA
Cordless Telephones
Packet Data
1950
1970
1960
1980
2000
2010
1990
1940
Mobile Radio 1946
Improved Mobile Telephone Service
PCS
3G IMT-2000 Bluetooth WiFi
Paging
Wireless LANs
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Historical Notes

• Original mobile radio systems used a single,
  high-powered transmitter to cover a radius
  greater than 50 km
• Early systems used FM with 120 kHz bandwidth for
  a 3 kHz voice signal. This was later reduced to
  60 kHz, then to 30 kHz.
• Improved Mobile Telephone Service (IMTS) --
  introduced trunking
• (Many mobiles shared a single channel)
• Demand for mobile telephony greatly exceeded
  system capacity By 1976, Bell Mobile phone
  service for NYC market (approximately 10,000
  people) had only 12 channels, and could serve 543
  paying customers over 1000 square miles. The
  waiting list was greater than 3,700!
• The FCC finally allocated additional spectrum for
  mobile telephony in the late 70s by moving UHF TV
  channels

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Cellular Concept
Low power Transmitters
Cellular Switch (MTSO)
Location Database
PSTN
Handoff
Micro- cells
Enables frequency reuse!
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Cellular Hierarchy
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Wireline Call Setup
Switch
wire pair
PSTN
Helens phone
network address
Bobs phone
Information Flow
off hook
dial tone
keystrokes
alert signal
ring indication
off hook
remove ring indication
conversation
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Cellular Call Setup
1. Call Request
2. Send numbers to switch
3. Page Receiver
4. Request Channel
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Cellular Call Setup (cont.)
5. Switch assigns channels
6. Cellular conversation is set up
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Information Flow for Cellular Call
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The Personal Communications Concept
Wired and wireless networks
Communications between people and/or
machines anytime, anywhere, any place.
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Personal Communications Services (PCS)

• Originally a vision for the extension and
  integration of wired and wireless
  telecommunications network capabilities (1980s).
• Wireless cellular, cordless, paging, PBX,
  satellite, air-to-ground
• Wireline PSTN, internet, LANs, private networks
• More than wireless (service concept)
• Service profile management
• Customized service profile follows user.
• Single, personal ID (Universal Personal Telephone
  number)
• Supports both personal mobility and terminal
  mobility/portability.
• Provides interoperability among wireline,
  wireless networks
• Encompasses all cellular hierarchies (pico
  through macro)
• Integrated services (voice, data, message
  broadcast, multimedia)

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Challenges to PCS1. Integration of
Micro-/Macro-Cells
Macro-cell (1-2 mile radius)
High power (expensive) Transmitters
Micro-cell (e.g., city block)
Low power (inexpensive) transmitters
Handoffs and interference management are major
issues!
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PCS Challenges 2. Spectrum Allocation

• Global, transparent service requires that the
  same spectrum be available everywhere.
• Must have an international standards body to
  allocate spectrum for this purpose.

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International PCS Spectrum Allocation

• Task of the International Telecommunications
  Union (ITU)
• Standards body for United Nations
• Headquarters in Geneva, Switzerland
• International Mobile Telecommunications (IMT)
  2000
• Initiative for Third Generation mobile telephony
  within the ITU
• World Administrative Radio Conference (WARC)
• Targeted 230 MHz for IMT 2000 in 1992(1885-2025
  MHz, 2110-2200 MHz)
• Targeted additional 329 MHz for 3G networks in
  2000(2500-2690 MHz, 1710-1885 MHz, 806-960 MHz)
• Targeted 255 MHz in 5 GHz band for unlicensed
  spectrum (WLAN) in 2003

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PCS Spectrum Allocation (1993)
Wavelengths too long propagates too far

• FCC ruling, September 1993
• 40 MHz unlicensed PCS spectrum
• 20 MHz for voice products (WPBXs)
• 20 MHz for data products (WLANs)
• 120 MHz licensed spectrum
• For public service providers
• 7 licenses auctioned

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U.S. Frequency Allocations

• U.S. frequency allocations

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PCS Spectrum Allocation Notes

• Emerging technologies band 220 MHz (2 GHz band)
• Applies to either Major or Basic Trading
  Areas
• 51 Major Trading Areas 492 Basic Trading Areas
• Shared with incumbent micro-wave (fixed
  point-to-point) systems for transition period (lt3
  years).
• Licensed spectrum assigned via auctions
• More than 30 Billion netted by U.S. government
  in mid-90s
• 3G auctions postponed in U.S. in 2001
• European auctions occurred well before 2000
• England netted 35.5 Billion USD (5 licenses)
  Germany netted 46 Billion USD (4 licenses)
• Unlicensed allocations
• Industrial, Scientific, and Medical (ISM) bands
  (mid 80s)
• 902-928 MHz, 2400-2483.5 MHz, 5150-5350 MHz
• Used by Wireless LANs (802.11), Bluetooth,
  proprietary systems for wireless access
• Unlicensed National Information Infrastructure
  (UNII) band (1997)
• Additional 300 MHz in ISM bands 5150-5350 MHz and
  5725-5825 MHz

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PCS Challenges3. Interoperability

• Multiple cellular standards (North American,
  European, Japanese, Chinese)
• Multiple vendor-specific air interfaces.
• Heterogeneous network architectures with multiple
  vendors complicates control signaling,
  maintenance, network management, and security.

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Potential Solution Software Radio

• Software controllable and flexible
  transmitter/receiver architecture
• Radio functions implemented via digital signal
  processing and re-configurable hardware
• Flexible selection of frequency bands.
• Modulation, coding, multiple access
• Ability to download an air-interface architecture
  and dynamically reconfigure the user terminal
• Multimode or multi-standard support
• Proposed implementations
• Real-time compiler of air-interference software
• Smart cards
• Universal control channel for accessing software
• Increases lifetime of handset
• Evolution to cognitive radio
• Automatically selects frequency band, configures
  transmitter to avoid interference adapts to user
  preferences

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PCS Challenges4. Economics

• Providing a density of base stations is
  expensive!
• Demand for services is uncertain

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Outline

• Background and history
• Overview of current wireless services and
  standards
• Whats on the horizon?

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Wireless Standards A Sampling
2G
802.16e
WiMax
EDGE
802.22
1xEVDO
UMTS
802.20
Zigbee
LMDS
UWB
1xEVDV
WiFi
3G
802.11g
CDMA2000
802.15
GSM
WCDMA
802.11a
IS136
802.11b
1G
HSDPA
Bluetooth
IS95
GPRS
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Wireless Standards
Cellular
PAN
MAN
LAN
Sensor
GSM GPRS iDEN CDMA2000 WCDMA UMTS 1xEVDO 1xEVDV 1G
/2G/3G/4G 3GPP/3GPP2
WiFi 802.11a/b/g Hiperlan
802.16 802.16e WiMax 802.20 Blackberry LMDS MMDS
Bluetooth 802.15 UWB
ZigBee RF ID
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Why Have a Standard?

• Allows equipment from different vendors to work
  together in a network.
• Enables competition.
• Provides more choices for service providers.
• Helps small companies (e.g., chip vendors,
  software houses) enter large markets.
• Create mass markets for equipment, economies of
  scale.
• Can potentially share intellectual property.

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Standard Development Process
Implementation groups IEEE 802, T1
Regional organizations ETSI (Europe), TIA
(U.S.), ARIB (Japan)
Global organizations ITU
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Classification of Wireless Information Systems
Voice-oriented (circuit-switched)
Data-oriented (packet-switched)
Cordless (low power, local area)
Cellular (high power, wide area)
LANs/PANs (high speed, local area)
Mobile Data (low to moderate speeds wide area)
IEEE 802.11 (WiFi) HIPERLAN Ricochet Bluetooth Hom
e networks Ultra-wideband (802.15.3) Broadban
d access LMDS, MMDS
AMPS (1G) GSM (2G) IS-136 (2G) IS-95 (2G) iDEN
(Nextel) CDMA 2000 (3G) UMTS (3G) Satellite
systems
Telepoint CT-1, CT-2 2G PCS standards
PACS, PHS, DECT Wireless local loop WiMax (802.16)
CDPD Narrowband PCS (Paging systems) ARDISBlac
kberry GPRS 3G Cellular
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Classification of Wireless Systems

• Cellular
• Wireless Local Area Networks (WLANs)
• Wireless Metropolitan Area Networks (WMANs)
• Wireless Personal Area Networks (WPANs)
• Sensor Networks

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Classification of Wireless Systems

• Cellular
• Wireless Local Area Networks (WLANs)
• Wireless Metropolitan Area Networks (WMANs)
• Wireless Personal Area Networks (WPANs)
• Sensor Networks

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Three Generations of Cellular Systems (and
counting)
Narrowband AMPS Digital cellular IS-136
(USDC), GSM, IS-95 Digital Cordless CT2,
DECT PHS, PACS
IMT 2000 Wideband CDMA CDMA 2000
Analog cellular(AMPS, TACS, NTT) Cordless
phones Paging
First (1970s, 1980s)
Third (2001)
Second (early 1990s)
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Cellular Spectrum (50 MHz)
uplink
825
824
835
845
846.5
849
A
A
B
A
B
869
870
880
890
891.5
894
downlink

• 30 kHz AMPS (1G) Channels
• 416 FDD Channels
• 395 FDD voice channels
• 21 FDD control channels

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Problems With First Generation (1G) Cellular
Cellular
Cordless

• Limited capacity
• Limited roaming(big problem in Europe)
• Voice only

• Limited range
• Susceptible to interference
• Poor security
• Not interoperable

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The Multiple Access Problem
How can multiple mobiles access (communicate
with) the same base station?

• Frequency-Division (AMPS)
• Time-Division (IS-136, GSM)
• Code-Division (IS-95, 3G)

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Time-Division Multiple Access (TDMA)
. . .
N time slots H Frame Header
H
1
2
N
H
frame
Direct-Sequence (DS) Code-Division Multiple
Access (CDMA)
Narrowband (14.4 kbps)
Data
spread
Code (chips)
Transmitted Signal
Wideband (1.25 MHz)
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Duplexing (Two-way calls)
Frequency-Division Duplex (FDD)
Channel 1
Channel 2
Time-Division Duplex (TDD)
Time slot (frame) 1
Time slot (frame) 2
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Second Generation (2G) CellularTDMA Standards
GSM
IS-136

• Global System for Mobile Communications
• Originated in Europe
• Incompatible with 1G systems
• More than an air-interface standard specifies
  wireline interfaces/functions

• North Americal Digital Cellular (NADC)
• Fits into existing AMPS standard
• Air-interface only
• Another standard, IS-41, specifies networking
  functions

• TDMA/FDMA, FDD
• Dynamic frequency assignment
• 50 MHz allocated (890-960 MHz)
• 200 kHz channels
• 270.833 kbps

• TDMA/FDMA, TDD
• Fixed frequency assignment
• 50 MHz allocated (824-894 MHz)
• 30 kHz channels
• 48.6 kbps

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2G CDMA IS-95 or cdmaOne

• Introduced by Qualcomm (San Diego)
• Direct-Sequence Spread Spectrum signaling
• FDD
• Wideband channels (1.25 MHz)
• Tight, closed-loop power control
• Sophisticated error control coding
• Multipath combining to exploit path diversity
• Noncoherent detection
• Soft handoff
• High capacity
• Air-interface only uses IS-41

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Problems with Second Generation Cellular

• Data services
• limited to voice rate
• circuit-switched
• Interoperability
• GSM, IS-136, CDMA are incompatible standards
• Solution multi-mode phones!

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Third Generation Cellular Objectives

• Wide range of services
• Wireless email, web browsing, e-commerce
• Corporate LAN access, videoconferencing
• Interactive video, infotainment
• Wide range of data rates
• 144 kbps for users in motor vehicles (high-tier
  mobility)
• 384 kbps for pedestrians (low-tier mobility)
• 2 Mbps for office use
• Support for asymmetric links
• Support for both circuit- and packet-switched
  data services
• Increase in spectral efficiency
• Global roaming
• Operation in all radio environments

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Some 3G Terminology

• CDMA 2000
• 3G standard developed for deployment in the U.S.
• 1.25 MHz bandwidth
• WCDMA (Wideband CDMA)
• 3G standard developed for deployment in Europe,
  but also being deployed in the U.S.
• also called UMTS (Universal Mobile
  Telecommunications System)
• 5 MHz bandwidth
• Third Generation Partnership Project (3GPP)
• International effort to harmonize the evolution
  of 3G systems

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1x/3x Technologies
1xEV-DO
Refers to 1.25 MHz unit of bandwidth. (3x is
3.75 MHz)
EVolutionary
Data Only (rates up to 2 Mbps)
1xEV-DV
Data and Voice
1x/3x RTT
Radio Transmission Technology
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Third Generation Standards Some Important
Acronyms

• ITU International Telecommunications Union
• Standards body for the United Nations
  headquartered in Geneva
• IMT-2000 International Mobile Telecommunications-
  2000
• Initiative for 3G mobile systems within the ITU
• TIA Telecommunications Industry Association
  (U.S.)
• ETSI European Telecommunications Standards
  Institute
• UMTS Universal Mobile Telecommunication System
• European version of IMT-2000
• UTRA UMTS Terrestrial Radio Access
• UMTS without the satellite component
• ARIB Association of Radio Industries and
  Businesses (Japan)
• 3GPP Third Generation Partnership Project
  (www.3gpp.com)

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3G Air Interfaces
cdma2000
Wideband (W)-CDMA

• Also referred to as multicarrier CDMA
• 1X Radio Transmission Technology (RTT) 1.25 MHz
  bandwidth (1 carrier)
• Supports 307 kbps instantaneous data rate in
  packet mode
• Expected throughput up to 144 kbps
• 3X RTT 3.75 MHz bandwidth (3 carriers)
• Data rates can exceed 2 Mbps
• 1xEV (Evolutionary) High Data Rate standard
  introduced by Qualcomm
• 1xEV-DO data only, 1xEV-DV data and voice
• Radio channels assigned to single users (not
  CDMA!)
• 2.4 Mbps possible, expected throughputs are a few
  hundred kbps
• 1xEV-DV has twice as many voice channels as IS-95B

• Also referred to as Universal Mobile
  Telecommunications System (UMTS)
• European proposal to ITU (1998)
• Backwards compatibility with 2G GSM and IS-136
  air interfaces
• Network and frame structure of GSM
• Always on packet-based data service
• Supports packet data rates up to 2 Mbps
• Requires minimum 5 MHz bandwidth, FDD, coherent
  demodulation
• 6 times spectral efficiency of GSM

52
2.5G Technologies Evolution to 3G

• HCSCD High Speed Circuit Switched Data
• Enhancement to GSM which allows multiple time
  slots/user
• GPRS General Packet Radio Service
• Provides a packet network on dedicated GSM or
  IS-136 radio channels.
• always on
• Peak data rate of 21.4 kbps per dedicated time
  slot
• Can assign multiple time slots
• No new Radio Frequency (RF) hardware needed!
• EDGE Enhanced Data rates for GSM (or Global)
  Evolution
• More advanced upgrade to GSM
• Adaptively selects modulation and coding scheme
  (MCS)
• Higher-order modulation (8-PSK) achieves up to
  384 kbps
• IS-95B (2.5G CDMA standard)
• Allows multiple codes per user
• Practical throughput of 64 kbps

53
Upgrade Paths 2G to 3G
2G
2.5G
3G
3GPP
3GPP2
W-CDMA/UMTS
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Service Providers and Technologies (2005)
1Merged with ATT. 2Currently merging with Sprint.
3Plans to roll out UMTS in N. America. 4Wideband
version of iDEN.
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Cellular Subscribers by Standards
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Classification of Wireless Systems

• Cellular
• Wireless Local Area Networks (WLANs)
• Wireless Metropolitan Area Networks (WMANs)
• Wireless Personal Area Networks (WPANs)
• Sensor Networks

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Comparison of Wireless Systems
58
Wireless Local Area Networks (WLANs)

• Low mobility, high data rates within confined
  region (building or campus)
• Competitive with other wireless data systems
  (3G, fixed wireless access)
• Unlicensed bands
• Industrial, Scientific, Medical (ISM) 2.4 GHz
• National Information Infrastructure (UNII) 5
  GHz
• Must accept interference, therefore uses spread
  spectrum signaling, or random access with
  collision avoidance.

59
WLANS are not Ethernet

• Different Equipment
• Access Points instead of LAN switches
• WLAN adapter cards instead of LAN card
• Different Technology
• Different Physical Layer
• Different MAC layer
• Different Use Model
• WLAN Suitable for Nomadic and Mobile Usage
• LAN Suitable for Stationary Use

60
WLANs Take Off

• Routers, access points, WLAN cards are
  inexpensive.
• 802.11 standards enable a public LAN (publan)
• Nationwide infrastructure of WLAN access points
  offered by a Wireless Internet Service Provider
  (WISP) (MobileStar, Wayport)
• Product interoperability (Wireless Ethernet
  Compatibility Alliance)
• Always-on internet access with a public service
  fee
• Advantages for the enterprise
• Enables mobility
• Easy to maintain (no wiring)
• Advantages for the residence
• Provides broadband services
• Home media gateway appliance
• 802.11a/b from gateway to home electronics/devices
  
• Spectrum sharing model works for wireless data.
• Concerns
• Security
• Interference

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Overview of 802.11 Standard
2 Mbps 4GFSK
62
WLAN Family of Standards 802.11

• 802.11 2 Mbps (with fallback to 1 Mbps), 1997
  1999
• Products available
• 802.11b (Wi-Fi) provides additional 5.5 and 11
  Mbps rates (2.4 GHz)
• Products available
• 802.11a provides up to 54 Mbps in the 5 GHz band
• Products available
• 802.11g Supports roaming, higher rate, backward
  compatible with 802.11b
• Products available
• HomeRF 10 Mbps using frequency-hopping
• Recently disbanded!
• Analogous standard in Europe High Performance
  Radio Local Area Network (HIPERLAN)

63
802.11 Standards in Progress

• 802.11e QoS Security Enhancements
• 802.11f Inter Access Point Protocol (IAPP)
• 802.11h Power Management for 5 GHz in Europe
• 802.11i Security enhancements
• 802.11j Enhancements to 802.11a for operation in
  Japan.
• 802.11k Radio resource management
• 802.11m Technical corrections and clarifications
• 802.11n High-throughput enhancements
• 802.11u Interfacing with external networks
• 802.11v Upper layer interface for managing
  802.11 equipment

64
802.11a/b/g Comparison
Comparison table
65
Orthogonal Frequency Division Multiplexing (OFDM)
used in 802.11a/g
Modulate Carrier f1
substream 1
Split into M substreams
Modulate Carrier f2
substream 2
source bits
substream M
OFDM Signal

Modulate Carrier fM
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Integrated WLAN-Cellular Network
67
Integrated WLAN/Cellular Network

• High data rates at hot spots covered by WLANs.
• Lower data rates elsewhere provided by cellular.
• Single account single bill
• Roaming
• Session mobility
• Common applications and services

68
Classification of Wireless Systems

• Cellular
• Wireless Local Area Networks (WLANs)
• Wireless Metropolitan Area Networks (WMANs)
• Wireless Personal Area Networks (WPANs)
• Sensor Networks

69
Emerging Broadband Wireless Access

• Competitive with wired broadband access
• 1300 MHz in the 27-31 GHz band was auctioned
  off by the U.S. government in 1998 (netted
  500 M)

70
Comparison of Spectrum Allocations
60 GHz Unlicensed, 5000 MHz, 1998
LMDS, 1300 MHz, 1998
Cellular, 50 MHz, 1983
UNII, 300 MHz 1997
PCS, 150 MHz 1995
71
Local Multipoint Distribution Service (LMDS)

• Uses spectrum in the 28-31 GHz range.
• Prototype systems involve hub transceivers on
  towers spaced a few kilometers apart. Each hub
  serves customers with rooftop antennas.
• gt 100 LMDS licensees in 1999
• Applications include local exchange telephone
  service, internet access, and other broadband
  services for businesses, residences, schools,
  libraries, health care providers, and rural
  communities.
• High frequencies (short wavelengths) highly
  attenuated by rain and snow.
• Short propagation path implies large frequency
  reuse.
• Air interface standards are being developed
• Analogous efforts are underway in other countries.

72
Wireless Digital Subscriber Line
73
IEEE 802.16

• Wireless Metropolitan Area Network (WMAN)
  standard being developed.
• Longer distances, broader coverage than WiFi
• Promoted by WiMax (Worldwide Interoperability
  for Microwave Access) forum, or industry
  consortium.
• Supports point-to-multipoint data connections in
  the 10-66 GHz range, data rates up to 120 Mb/s
  (requires line-of-sight).
• Standard being developed for both licensed and
  unlicensed spectrum.
• Dynamic bandwidth allocation via TDMA
• Access points and cards for PCs, PDAs wont be
  available until mid-2004 at the earliest...
  (still not available)
• 802.16a/d recently developed for
  non-line-of-sight in 2-11 GHz.
• 802.16e in progress to support mobility.

74
Flarions Flash OFDM

• 1.5 Mbps (avg)
• with 1.25 MHz FDD
• Ubiquity of cellular
• Flat rate pricing, low cost
• WAN WLAN (WiFi) interoperability
• Cell-to-cell handoff
• Initiated 802.20 standard
• Competes with 802.16?
• Flarion bought by Qualcomm, January 2006

75
Classification of Wireless Systems

• Cellular
• Wireless Local Area Networks (WLANs)
• Wireless Metropolitan Area Networks (WMANs)
• Wireless Personal Area Networks (WPANs)
• Sensor Networks

76
Personal Area Networks (PANs)
77
Bluetooth A Global Specification for Wireless
Connectivity

• Wireless Personal Area Network (WPAN).
• Provides wireless voice and data over short-range
  radio links via low-cost, low-power radios
  (wireless cable).
• Initiated by a consortium of companies (IBM,
  Ericsson, Nokia, Intel)
• IEEE standard 802.15.1

78
Bluetooth Specifications

• Allows small portable devices to communicate
  together in an ad-hoc piconet (up to eight
  connected devices).
• Frequency-hopped spread-spectrum in the 2.4 GHz
  UNII band.
• Packet switching with 1600 hops/s over 1 MHz
  channels.
• Range set at 10m.
• Gross data rate of 1 Mbps (TDD), with second
  generation plans for 2 Mbps.
• 64 kbps voice channels
• Maximum asymmetric data transfer rate of 721 kbps
  in either direction,or 432.6 kbps symmetric
  link
• Interferes with 802.11.
• Competes with 802.11?

79
Classification of Wireless Systems

• Cellular
• Wireless Local Area Networks (WLANs)
• Wireless Metropolitan Area Networks (WMANs)
• Wireless Personal Area Networks (WPANs)
• Sensor Networks

80
Sensor Networks

• Lots of hype,
• one of the top 21 technologies for 21st
  centutry Business Week.
• Many applications envisioned
• Security, remote environmental sensing.
  structural monitoring, asset tracking, building
  automation, industrial monitoring, agricultural
  monitoring
• Numerous startups also commercial interest from
  large companies
• Standards activities
• IEEE 802.15.4 (ZigBee)
• Large research investment
• DARPA, NSF, ..
• Lots of academic activities
• Conferences, journals, research centers

81
Properties of Sensor Networks

• Small sensor nodes referred to as motes
• Low power
• Low maintenance
• Cheap (around 1 per node for high density
  applications)
• Combined with MEMS (Micro Electro-Mechanical
  Systems) technology

82
Example (Crossbow mote)

• Crossbow MICA2 Multi-Sensor Module
• Light, Temperature,Microphone, Sounder,Tone
  Detection Circuit, 2-Axis Accelerometer, 2-Axis
  Magnetometer
• Contains memory (lt 1MB) transmits up to 250 kbps
• 2 AA batteries
• 100

83
RFID (Radio Frequency Identification)

• A close cousin to sensor network technology.
• Generally, RFID tags are cheaper, but less
  intelligent than sensor nodes.
• Can be active (generate own power) or passive
  (reflect transmitted signal)
• Lots of applications
• Inventory control (Walmart, military)
• Toll collection (I-Pass) / mass transit
• Passport control
• Implanted IDs
• Smart cards (electronic cash)

84
RFID Systems

• Main components
• Tags (transponders).
• -microchip antenna
• Tag reader
• decoder antenna
• (in some cases separate)

85
ZigBee

• Sensor net standard (IEEE 802.15.4)
  specification for a suite of communication
  protocols using small, low-power digital radios
• ZigBee Alliance consortium of companies
  interested in setting requirements for compliance
  and testing.
• Over 200 members (includes control systems
  companies like Honeywell, Johnson Controls,
  Siemens)
• Intended for home networking applications (e.g.,
  wireless light switch, security, networked
  appliances)
• http//www.spectrum.ieee.org/oct06/4666/zigbeef1
• Can transmit up to 250 kbps in ISM band.

86
ZigBee and 802 protocols
WWAN
IEEE 802.22
IEEE 802.20
WMAN
WiMax IEEE 802.16
Range
WLAN
WiFi 802.11
ZigBee 802.15.4
802.15.3 802.15.3a 802.15.3c
Bluetooth 802.15.1
WPAN
0.01
0.1
1
10
100
1000
Data Rate (Mbps)
87
Outline

• Background and history
• Overview of current wireless services and
  standards
• Whats on the horizon?

88
Edholms Law of Bandwidth
89
Cellular Evolution
90
Fourth Generation Drivers

• Higher data rate services
• Enhanced video services
• Home medical care, remote diagnoses
• Sensor networks
• Ubiquity
• Seamless mobility between WLAN, cellular

91
4G System Objectives(Tachikawa article)

• High-speed transmission (peak 50 100 Mb/s,
  average 200 Mb/s)
• Larger capacity ( 10 X greater than 3G)
• Next-generation Internet support (IPv6, QoS)
• Seamless service
• Flexible network architecture (cellular ??
  peer-to-peer)
• Use of microwave band (3 6 GHz)
• Low system cost (1/100 1/100 of 3G)

92
WiFi Evolution 802.11n

• Supports data rates up to 540 Mbps
• Could replace USB 2.0 connections.
• Longer range than Ultra-wideband
• Four competing proposals, completed standard not
  expected before 2007
• Technology based on OFDM with multiple antennas
  at the transmitter and receivers
• Multi-Input/Multi-Output (MIMO) channels

93
Ultrawideband Signals

• FCC definition Any signal that occupies at least
  500 MHz between 3.1 and 10.6 GHz.
• Must radiate lt 0.56 mW (cellular limit 3 mW).
• Interference and security are concerns.

94
Comparing Ultrawideband

• Standard under development (802.15.3).
• Competing technologies proposed by Motorola
  (pulse modulation) and Intel consortium (OFDM).
• May kill Bluetooth.

95
Is Spectrum a Scarce Resource?
96
Concept Develop both the system concepts and the
enabling technology to dynamically assign
spectrum.
97
Opportunistic Spectrum Sharing(from
www.darpa.mil)

• Increase spectrum usage by dynamically sensing
  and adapting in frequency, time and space
• Top Technical Challenges
• Sense Low-power, wide-band spectrum monitoring
• React Time-frequency agile transmissions
• Adapt Dynamic spectral access and control

98
Spectrum Allocation

• Most bands are quiet most of the time.
• FCC would like to reclaim spectrum via
• Reallocation (e.g., from government to new
  services)
• Leasing (e.g., to third parties) relaxing
  service limitations (e.g., hybrid satellite and
  terrestrial)
• Sharing (more unlicensed spectrum for shared
  servies)
• Available bandwidth for video and mobile wireless
  services may increase by more than 1500 Mhz and
  300 MHz, respectively.
• Additional efficiencies created through
  technological advances (spread spectrum,
  interference mitigation techniques, cooperative
  relays)
• Many technical, regulatory, and marketing issues.

99
Cooperative Wireless Networks
Cell Boundary
relay node
relay node
(alternative path)

• Requires less power
• Creates less interference
• Total capacity increases with users

100
Cooperative Mesh Networks

• Sophisticated modulation, coding, diversity
  schemes (multiple antennas)
• Hierarchical routing
• Low cost relay nodes

101
Cooperative Networking Challenges

• Interference
• Design issues signaling, multiple access,
  routing, etc.
• Network management, cost of relays
• How does the network capacity increase with
  number of users?
• Spectrum policy ownership vs. sharing
• Ownership associated with cellular, sharing
  associated with WiFi
• Sharing can exploit spectrum holes

102
Wireless Challenges