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Emerging Wireless Networks

The move is toward fast Internet access so 4G aims at an all-IP solution ... TCP is custom-designed for the wired Internet. But when you have a wireless last-hop. Key: ...

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Emerging Wireless Networks

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    Slide 1:Emerging Wireless Networks

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

    Slide 2:Outline

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

    Slide 3: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)

    Slide 4: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

    Slide 5: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

    Slide 6:Wireless Internet at 75 mph

    Slide 7: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)

    Slide 8:Frequency Spectrum Continuum

    Slide 9: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

    Slide 10:Air Interface Standards

    Slide 11: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

    Slide 12: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

    Slide 13: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!!

    Slide 14:Speed and Environment

    Slide 15: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

    Slide 16: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

    Slide 17:Multipath Propagation

    Slide 18: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

    Slide 19:Network Layer Issues

    Routing and Inter-domain Mobility Management – Mobile IP

    Slide 20: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

    Slide 21: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

    Slide 22: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)

    Slide 23: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

    Slide 24:Some challenges

    User authentication, access control and mobility management

    Slide 25:Some challenges

    User authentication, access control and mobility management Need mechanisms to authenticate unknown users

    Slide 26:Some challenges

    User authentication, access control and mobility management Need to protect network from malicious users

    Slide 27:Some challenges

    User authentication, access control and mobility management Need mechanisms to manage host configuration as users roam between the two networks

    Slide 28:A Public Wireless Network

    Wireless Subnet Local Services Internet

    Slide 29:Public Network Architecture

    Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

    Slide 30:Client Connects to Local Portal

    Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

    Slide 31:Client Authenticates with Global Authenticator

    Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

    Slide 32: Global Authenticator Responds

    Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

    Slide 33:Authorizer Generates Session Key

    Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet Policy

    Slide 34:Client Gains Access Via Verifier

    Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

    Slide 35: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

    Slide 36: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)

    Slide 37: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

    Slide 38: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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