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Mobile Technologies

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. Mobile Architecture. Mobile station.

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Mobile Technologies

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  1. Mobile Technologies 2110472 Computer Networks Natawut Nupairoj, Ph.D. Department of Computer Engineering Chulalongkorn University

  2. Outline • Overview • How Cell Phones Work. • GSM (2G). • GPRS (2.5G). • 3G and Other Technologies.

  3. Overview

  4. Mobile Cells

  5. Mobile Architecture Mobile station BSC PSTN BSC MSC BSC basic station controllerMSC mobile switching centerHLR home location registerVLR visitor location registerAC access controlEIR equipment identity register HLR VLR AC EIR

  6. Transmission Techniques • Encoding Schemes • Analog. • Digital. • Multiplexing Schemes • FDMA. • TDMA. • CDMA.

  7. 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.

  8. CDMA • Pros • More capacity than FDMA/TDMA. • Require low power for Handset (0.2 Watts). • Cons • Complicated. • Expensive (both handset and cell equipment).

  9. Multiplexing Schemes

  10. Additional Terminologies • Mobile Originator. • Mobile Terminator. • Hand-off. • Roaming.

  11. 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).

  12. ETDMA • TDMA with • Signal compression. • Silence suppression • Use time slot when there are speeches. • Similar to frequency hopping.

  13. Handset Market Share

  14. 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. 2 Mbps 384 Kbps 114 Kbps

  15. 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).

  16. 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).

  17. SMS Architecture

  18. SMS MechanismMobile Terminated Side

  19. SMS MechanismMobile Originated Side

  20. 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.

  21. 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).

  22. WML

  23. WAP Stack

  24. HTTP vs. WSP Overheads

  25. Iridium • Global Personal Communication • Any place, any time. • Use Low Orbit Satellites (LEO) • 66 LEO with 6 spares. • Each covers small areas. • Satellites handoff.

  26. 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/.

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