Mobile Technologies

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
AC
HLR
VLR
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/
  .