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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