Emerging Wireless Networks

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Emerging Wireless Networks

• Anand Balachandran
• http//www-cse.ucsd.edu/users/abalacha/

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Outline

• Introduction
• Wireless Internet today
• Some history
• Access technologies and Standards
• Radio access technologies
• Going up the protocol stack
• Future of Ubiquitous Wireless Internet

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The New mobile mantra

• Anywhere
• home, office, car, mall, top of Mt. Everest
• Anytime
• day or night
• Anyone
• between any number of persons anywhere in the
  world
• Any device
• Pager, cell phone, pocket computer, wireless
  watch, sensor badges, earrings
• Any service
• multi-media (voice, video, data)

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What is the Wireless Internet?

• Wireless access to WWW services and content no,
  not quite!
• Wireless Internet
• Access Technologies
• Architecture
• Protocols
• Devices
• Heterogeneous blend of standards bodies,
  companies and industry forums

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Wireless Internet (contd.)

• Advances in Integrated Circuits
• Displays
• Embedded Operating Systems
• Lightweight portable devices (form factor)
• Radio Access technologies
• Wireless networking protocols
• Services and software technologies

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Wireless Internet at 75 mph
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How it all Started

• First wireless line of sight communications
• Early pioneers used smoke signals, mirrors,
  flares, semaphores
• First radio transmission
• Demonstrated by Marconi in 1895
• First wireless voice communication
• Between NYC and SFO in 1915
• First public mobile telephone service
• Introduced in 25 US cities in 1946 (very
  inefficient)

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Frequency Spectrum Continuum
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Cellular Family Tree

• First Generation introduced by ATT in 1983
• Analog cellular telephony
• AMPS
• FDMA
• Divided the frequency band into 30 channels
• 2G introduced in 1987 in Europe
• Digital cellular services at data rates upto 14.4
  Kbps
• Three primary wireless standards
• TDMA (Time Division Multiple Access)
• GSM (Global System for Mobile Communications)
• CDMA (Code Division Multiple Access)
• Cellular Digital Packet Data (CDPD) at 19.2 Kbps

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Air Interface Standards
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Cellular Family Tree 2.5G

• 2.5G (Here and Now)
• In support of faster wireless data services
• HSCSD (High Speed Circuit-switched Data)
• Extension to GSM 57.6 Kbps
• GPRS (Generalized Packet Radio Service)
• Another extension to GSM 100 Kbps
• Cellular Subscriber growth
• Currently 300 million worldwide
• Heterogeneous standards
• Dual mode or Multimode phones

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Cellular family tree 3G

• 3G (some time this year we hope)
• ITU IMT-2000 Project
• Will transmit at
• 144 Kbps for fast moving vehicular users
• 384 Kbps for slow moving pedestrian users
• 2 Mbps for fixed location
• Multiple proposals (US, Europe and Japan)
• W-CDMA
• cdma2000
• UMTS
• The move is toward fast Internet access so 4G
  aims at an all-IP solution

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Packet Radio History

• First packet radio network, Hawaii, 1971
• Transmitted voice and data
• Channel access control was done through aloha
• Precursor for todays protocols
• Better media access protocols
• Slotted aloha
• Carrier sense multiple access (CSMA)
• Number of problems with detection
• Led to Wireless LAN standard (IEEE 802.11) in
  1990 based on CSMA/CA

We will revisit wireless LANS!!
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Speed and Environment
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Major Challenges in Wireless

• Limited Resources
• Scarce and expensive spectrum (FCC-regulated)
• Limited Bandwidth
• 2-10 Mbps in the LAN, wired is 100 Mbps
• Higher error rates
• Can be as poor as 10-2!!
• Wired BER at 10-12
• Limited Power
• Short battery life transmission and sensing are
  power-guzzling

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Major Challenges in Wireless

• Highly fluctuating channel conditions
• Multipath fading, noise, signal attenuation
• Time-varying changes
• Dependent on environmental conditions
• Impose severe limitations on range, data rates
  and reliability of communications
• - e.g. a radio for an indoor user at walking
  speeds will support much higher data rates than
  an outdoor user channel that operates in the
  shadow of tall buildings and where the user moves
  at high speeds

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Multipath Propagation
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And finally

• User mobility
• Need to locate the user
• Need to support routing to a moving user
• Need to continuously track the change in the
  location and deliver data while the user is
  roaming
• Need to manage the scarce resources in an fair
  and efficient manner while catering to varying
  user demands

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Network Layer Issues

• Routing and Inter-domain Mobility Management
  Mobile IP

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Transport Layer Issues

• TCP is custom-designed for the wired Internet
• But when you have a wireless last-hop
• Key Packet loss is not due to congestion
• Channel errors
• User handoffs
• TCP source scales back thinking there is a
  congestion (congestion control kicks in)
• Solutions
• Split the connection and use 2 TCP connections
  source to Base station, Base station to mobile
• Rexmit at the link-layer, hide loss from sender

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Application layer Issues

• Intelligent Adaptation to help Multimedia data
• Images hierarchical coding
• Progressive JPEG, Alternative 1, Alternative 2
• Video layered encoding
• Base layer, enhancement layers in MPEG-2
• Selective transmission of I, P, B frames
• Dynamic Rate Shaping DCT coefficients
• Trans-coding of images into different formats

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So where are we?

• Promise of Wireless LANs anywhere, anytime
  access at almost any place
• High Bandwidth (11 Mbps today and expected to
  grow 10-fold in three year)
• Provides accessibility at home, offices, and
  public places like sports arenas, airports,
  malls, university campuses, and hospitals
• Can extend the network to most places where
  people are likely to spend their time
• Need to extend connectivity beyond homes and
  offices to public places

Solution Public-area Wireless Networks (PAWNS)
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Can you do better than 4G?

• Of course!
• 50X difference in data rates
• 4G will not work as well indoors
• Cannot provide desirable form factor and variety
  of applications other than Web and email

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Some challenges

• User authentication, access control and mobility
  management

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Some challenges

• User authentication, access control and mobility
  management

Need mechanisms to authenticate unknown users
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Some challenges

• User authentication, access control and mobility
  management

Need to protect network from malicious users
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Some challenges

• User authentication, access control and mobility
  management

Need mechanisms to manage host configuration as
users roam between the two networks
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A Public Wireless Network
Internet
Wireless Subnet
Local Services
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Public Network Architecture
AuthorizerGateway
GlobalAuthenticator
Internet
VerifierGateway
Wireless Subnet
Local Services
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Client Connects to Local Portal
AuthorizerGateway
GlobalAuthenticator
Internet
VerifierGateway
Wireless Subnet
Local Services
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Client Authenticates withGlobal Authenticator
AuthorizerGateway
GlobalAuthenticator
Internet
VerifierGateway
Wireless Subnet
Local Services
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Global Authenticator Responds
AuthorizerGateway
GlobalAuthenticator
Internet
VerifierGateway
Wireless Subnet
Local Services
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Authorizer Generates Session Key
Policy
AuthorizerGateway
GlobalAuthenticator
Internet
VerifierGateway
Wireless Subnet
Local Services
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Client Gains Access Via Verifier
AuthorizerGateway
GlobalAuthenticator
Internet
VerifierGateway
Wireless Subnet
Local Services
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Service Models

• Model 1 Free access to local resources
• Does not require authentication but needs a valid
  IP address
• Allow access to the Intranet
• e.g. Mall portal, splash screens, indoor
  navigation service, Starbucks coffee ordering
  etc.
• Model 2 Authenticate and pay
• Allow access to the Internet
• Allow applications like location-based buddy
  list, spontaneous sales that are based on
  profiles etc.
• Differentiated charging

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A very viable model

• Information at the fingertips (end users win)
• WLAN hardware sold (hardware vendors win)
• Backbone network resources get used (ISPs win)
• Building attracts more people (store owners win)
• Software sold (software vendors win)

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Unsolved Issues

• Quality of Service
• Resource reservation and efficient bandwidth
  allocation
• Providing differentiated services with guarantees
• Power Conservation and control
• Energy-efficient channel access protocols
• Anonymity
• Keep user identity hidden (zero knowledge
  algorithms)
• Secure location tracking

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Theres lot more info and lot less time

• Exciting area to be in
• You will define the future of networking (Oh!
  Well)
• Read papers from ACM Mobicom, and Infocom
• Several workshops on Mobile Multimedia (WowMom,
  Momuc)