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Mobile Technologies
2110472 Computer Networks
Natawut Nupairoj, Ph.D.
Department of Computer Engineering
Chulalongkorn University
Outline
Overview How Cell Phones Work.
GSM (2G). GPRS (2.5G). 3G and Other Technologies.
Overview
Mobile Cells
BSC
BSC M
SCACHLR VLR EIR
PSTNPSTN
Mobile station
BSC basic station controllerMSC mobile switching centerHLR home location registerVLR visitor location registerAC access controlEIR equipment identity register
Mobile Architecture
Transmission Techniques
Encoding Schemes Analog. Digital.
Multiplexing Schemes FDMA. TDMA. CDMA.
CDMA
Code Division Multiple Access. Good for digital encoding. Frequency hopping style.
One band for all users in the cell. Modulate with a unique code for each user.
Analogy: several people in a room speaking different languages to each other.
CDMA
Pros More capacity than FDMA/TDMA. Require low power for Handset (0.2 Watts).
Cons Complicated. Expensive (both handset and cell equipment).
Multiplexing Schemes
Additional Terminologies
Mobile Originator. Mobile Terminator. Hand-off. Roaming.
Global System for Mobile communication. The dominated mobile standard
400 network operators in 182 countries. Over 700 million customers (June 2002). Considered “2G”.
Transmission Techniques Digital encoding. Extended Time Division Multiple Access
(ETDMA).
ETDMA
TDMA with Signal compression. Silence suppression
Use time slot when there are speeches.
Similar to frequency hopping.
Handset Market Share
Nokia, 37.20%
Motorola, 17.30%
Samsung, 9.80%
Seimens, 8.50%
Sony-Ericsson,
5.20%
GPRS
General Packet Radio Service Packet switching for Mobile
Typical call session (voice) is circuit switched. More efficient.
IP-enabled. “Always on”, pay as you send/receive. Speed: 14.4Kbps – 115Kbps. Considered “2.5G” – path to 3G.
114 Kbps
2 Mbps
384 Kbps
3G Mobile
New mobile architecture is coming For multimedia and internet applications. Up to 2 Mbps bandwidth for data.
Standards Universal Mobile Telecommunication System
(UMTS). Wide-band Code Division Multiple Access
(WCDMA).
Killer Applications
Short Message Service (SMS) – 2G Become increasingly popular
User: easy to use. Operator: bandwidth efficient.
Currently being used for Communication. Entertainment (download logo / ringtones). Interactive applications.
Future Multimedia Message Service (MMS).
SMS Architecture
SMS MechanismMobile Terminated Side
SMS MechanismMobile Originated Side
Mobile Internet Comparing to typical Internet
Bandwidth limitation with long latency. Screen size. Simple browser.
Wireless Access Protocol For mobile with limited HTML edition – WML.
WML
The Wireless Markup Language (WML) WMLScript
Adhering to XML standards. Do not assume a QWERTY keyboard or a
mouse. Designed for small screen displays.
WML documents divided into a set of units of interaction, called cards User navigate back and forth between cards. Reduce long latencies.
Smaller set of markup tags (comparing to HTML).
WML
WAP Stack
HTTP vs. WSP Overheads
Iridium
Global Personal Communication Any place, any time.
Use Low Orbit Satellites (LEO) 66 LEO with 6 spares. Each covers small areas. Satellites handoff.
References J. Kurose and K. Ross, Computer Networking: A Top-Down
Approach Featuring the Internet, Addison Wesley, 2001. M. Eng and L. Kirchoff, How Cellular Phone Technologies Compare,
http://www.ee.washington.edu/class/498/sp98/final/marsha/final.html, 1998. About.Com, Digital Technologies (CDMA, TDMA, and GSM),
http://cellphones.about.com/cs/technologies/.