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					  Emerging Wireless Networks




        Anand Balachandran
http://www-cse.ucsd.edu/users/abalacha/
  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 AT&T 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 today’s 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




    Local Services                          Wireless Subnet

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      Public Network Architecture



   Global                       Authorizer
Authenticator   Internet         Gateway




                                   Verifier
                                  Gateway
        Local Services                          Wireless Subnet

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      Client Connects to Local Portal



   Global                       Authorizer
Authenticator   Internet         Gateway




                                   Verifier
                                  Gateway
        Local Services                          Wireless Subnet

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      Client Authenticates with
      Global Authenticator



   Global                       Authorizer
Authenticator   Internet         Gateway




                                   Verifier
                                  Gateway
        Local Services                          Wireless Subnet

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      Global Authenticator Responds



   Global                       Authorizer
Authenticator   Internet         Gateway




                                   Verifier
                                  Gateway
        Local Services                          Wireless Subnet

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      Authorizer Generates Session Key
                                Policy




   Global                       Authorizer
Authenticator   Internet         Gateway




                                   Verifier
                                  Gateway
        Local Services                          Wireless Subnet

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      Client Gains Access Via Verifier


   Global                       Authorizer
Authenticator   Internet         Gateway




                                   Verifier
                                  Gateway
        Local Services                          Wireless Subnet

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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 (ISP’s
      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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There’s 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)

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