Emerging Wireless Networks Anand Balachandran

05/18/01Multimedia Systems Outline Introduction Wireless Internet today Some history Access technologies and Standards Radio access technologies Going up the protocol stack Future of Ubiquitous Wireless Internet

05/18/01Multimedia Systems 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)

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems Wireless Internet at 75 mph

05/18/01Multimedia Systems 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)

05/18/01Multimedia Systems Frequency Spectrum Continuum

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems Air Interface Standards

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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 ) in 1990 – based on CSMA/CA We will revisit wireless LANS!!

05/18/01Multimedia Systems Speed and Environment

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems Multipath Propagation

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems Network Layer Issues Routing and Inter-domain Mobility Management – Mobile IP

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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)

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems Some challenges User authentication, access control and mobility management

05/18/01Multimedia Systems Some challenges User authentication, access control and mobility management Need mechanisms to authenticate unknown users

05/18/01Multimedia Systems Some challenges User authentication, access control and mobility management Need to protect network from malicious users

05/18/01Multimedia Systems Some challenges User authentication, access control and mobility management Need mechanisms to manage host configuration as users roam between the two networks

05/18/01Multimedia Systems A Public Wireless Network Wireless Subnet Local Services Internet

05/18/01Multimedia Systems Public Network Architecture Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

05/18/01Multimedia Systems Client Connects to Local Portal Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

05/18/01Multimedia Systems Client Authenticates with Global Authenticator Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

05/18/01Multimedia Systems Global Authenticator Responds Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

05/18/01Multimedia Systems Authorizer Generates Session Key Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet Policy

05/18/01Multimedia Systems Client Gains Access Via Verifier Wireless Subnet Authorizer Gateway Verifier Gateway Global Authenticator Local Services Internet

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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)

05/18/01Multimedia Systems 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

05/18/01Multimedia Systems 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)