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/.