Transcript Emerging Wireless Networks

Emerging Wireless Networks
Anand Balachandran
http://www-cse.ucsd.edu/users/abalacha/
Outline
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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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Multimedia Systems
The New mobile mantra
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Anywhere
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Anytime
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between any number of persons anywhere in the
world
Any device
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day or night
Anyone
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home, office, car, mall, top of Mt. Everest
Pager, cell phone, pocket computer, wireless
watch, sensor badges, earrings
Any service
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multi-media (voice, video, data)
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What is the Wireless Internet?
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Wireless access to WWW services and
content – no, not quite!
Wireless Internet
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Access Technologies
Architecture
Protocols
Devices
Heterogeneous blend of standards bodies,
companies and industry forums
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Wireless Internet (contd.)
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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
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First wireless line of sight communications
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First radio transmission
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Demonstrated by Marconi in 1895
First wireless voice communication
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Early pioneers used smoke signals, mirrors, flares,
semaphores
Between NYC and SFO in 1915
First public mobile telephone service
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Introduced in 25 US cities in 1946 (very inefficient)
Multimedia Systems
Frequency Spectrum Continuum
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Cellular Family Tree
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First Generation introduced by AT&T in 1983
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Analog cellular telephony
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AMPS
FDMA
Divided the frequency band into 30 channels
2G introduced in 1987 in Europe
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Digital cellular services at data rates upto 14.4 Kbps
Three primary wireless standards
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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
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2.5G (Here and Now)
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In support of faster wireless data services
HSCSD (High Speed Circuit-switched Data)
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GPRS (Generalized Packet Radio Service)
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Extension to GSM – 57.6 Kbps
Another extension to GSM – 100 Kbps
Cellular Subscriber growth
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Currently ~300 million worldwide
Heterogeneous standards
Dual mode or Multimode phones
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Cellular family tree – 3G
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3G (some time this year – we hope)
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ITU IMT-2000 Project
Will transmit at
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Multiple proposals (US, Europe and Japan)
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144 Kbps for fast moving vehicular users
384 Kbps for slow moving pedestrian users
2 Mbps for fixed location
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
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First packet radio network, Hawaii, 1971
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Better media access protocols
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Transmitted voice and data
Channel access control was done through aloha
Precursor for today’s 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
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Limited Resources
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Limited Bandwidth
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2-10 Mbps in the LAN, wired is 100 Mbps
Higher error rates
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Scarce and expensive spectrum (FCC-regulated)
Can be as poor as 10^-2!!
Wired BER at 10^-12
Limited Power
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Short battery life – transmission and sensing are
power-guzzling
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Major Challenges in Wireless
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Highly fluctuating channel conditions
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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…
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User mobility
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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
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Routing and Inter-domain Mobility Management –
Mobile IP
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Transport Layer Issues
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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)
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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
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Intelligent Adaptation to help Multimedia data
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Images – hierarchical coding
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Video – layered encoding
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Progressive JPEG, Alternative 1, Alternative 2
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?
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Promise of Wireless LANs – anywhere,
anytime access at almost any place
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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?
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Of course!
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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
Global
Authenticator
Internet
Local Services
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Authorizer
Gateway
Verifier
Gateway
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Wireless Subnet
Client Connects to Local Portal
Global
Authenticator
Internet
Local Services
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Authorizer
Gateway
Verifier
Gateway
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Wireless Subnet
Client Authenticates with
Global Authenticator
Global
Authenticator
Internet
Local Services
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Authorizer
Gateway
Verifier
Gateway
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Wireless Subnet
Global Authenticator Responds
Global
Authenticator
Internet
Local Services
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Authorizer
Gateway
Verifier
Gateway
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Wireless Subnet
Authorizer Generates Session Key
Policy
Global
Authenticator
Internet
Local Services
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Authorizer
Gateway
Verifier
Gateway
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Wireless Subnet
Client Gains Access Via Verifier
Global
Authenticator
Internet
Local Services
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Authorizer
Gateway
Verifier
Gateway
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Wireless Subnet
Service Models
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Model 1: Free access to local resources
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Does not require authentication but needs a valid
IP address
Allow access to the Intranet
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e.g. Mall portal, splash screens, indoor navigation
service, Starbucks coffee ordering etc.
Model 2: Authenticate and pay
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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
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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
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Quality of Service
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Power Conservation and control
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Energy-efficient channel access protocols
Anonymity
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Resource reservation and efficient bandwidth
allocation
Providing differentiated services with guarantees
Keep user identity hidden (zero knowledge
algorithms)
Secure location tracking
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There’s lot more info and lot less
time
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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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