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The FundamentalConcepts of Mobile

Communication

Dr. Abhijit MitraDepartment of Electronics & Communication

Engineering

Indian Institute of Technology (IIT) Guwahati

Guwahati - 781039, India.E-mail: a.mitra@iitg.ernet.in

A Refresher Course at GU

Indian Academy of Sciences Indian National

Science Academy The NationalAcademy of Sciences

Bangalore New Delhi India, Allahabad

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Main Topics to be

Discussed

Introduction to mob. com. systems

Fundamentals of cellular systemengg.

Free space propagation of wrls.

signals

Improvement of mob. syst.performnc

A few other handset technologies

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Introduction What is mobile

communication?

Why mobile communication?

How many types?

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How many types of mobilecommunication?

(a) Simplex (b) Half-duplex (c) Duplex

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A Refresher Course at GU

What is the basic cellular structure?

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How a mobile phone call is made Let us say, mobile-to-mobile call

FVC, RVC, FCC and RCC

Scan available FCCs to search BS

Mobile identification number (MIN)

Responds by RCC BS MSC A pair of voice channel assigned

Now the receiver gets alert ring

International Mobile Subscriber Identity (IMSI)

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Cellular Systems

Engineering Frequency reuse

Hexagonal Geometry

Adjacent cells cannot use same channels

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System capacity enhancement

T: number of available channels

N: number of cells forming a cell-cluster

S: number of channels per cell

Repeat the cell-cluster by R times

Total no. of users: C = R.T = R.N.S

Only for these N:

N = x2 + y2 + 2xy; x,y >0

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Handoff strategies

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A few practical problems in handoff

Wide range of velocities

Umbrella cell approach

Cell dragging problem

Threshold power & radio coveragearea

Intersystem handoff

Roaming facility

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Free Space PropagationEM wave power (P) reduces with thesquare of the distance (d) it travels, i.e.,

For NLOS communication, it is

Small scale path loss, or, simply fading

Multipath propagation Doppler shift effect

Main objectiveof mobile systems is to

overcome these adverse effects

P

d-2

P d-n

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Improvement of Mobile System

PerformanceTransmitter techniques

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A Few Other Technologies Battery

Li-Ion battery 27 gm, 1100 mAh

Talk time: over 7 hours

In a study in August 2005 across15 global countries, 2/3 of mobile

users rated 2 days of battery lifeduring active use as the mostimportant feature

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VLSI/Processor/Memory

VLSI chips, e.g., 5 mm x 5 mm

300 MHz processor

A lot of storage space/memory

128 MB embedded flash ROM

64 MB embedded SDRAM

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Antenna

Low-power high-frequency planarantenna

Planar inverted-F antenna (PIFA)

Very low profile monopole antenna

Embedded GPS antenna

GPS radio IC and a small singlefeed balanced antenna

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Display

Passive/Active-matrix Organic LED(OLED)

Thin film transistor LCD (TFT-LCD)

Quarter VGA (QVGA), 240 x 320 pixels,16-bit color

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Conclusion Present:

Two key parameters: volume, weight

Standard incompatibility: GSM/IS136/PDCand CDMA

Future: Another two key parameters: power

consumption, component count B3G technologies

All computing facilities with artificialintelligence

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ReferencesReferences

Wireless Digital Communications: Modulation and Spread Spectrum

by K. Feher; Prentice Hall of India, 2002.

Mobile Communication: The Basic Concepts

by A. Mitra; Breakthrough, vol. 11, no. 3, Feb. 2006.

Wireless Communications: Principles and Practiceby T. S. Rappaport; Pearson Education, 2002.

Digital Communications

by J. G. Proakis; McGraw Hill, 2000.

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Mobile Computing: Past, Present and Future

by V. Koudounas; [Online].

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IMEI International Mobile Equipment IdentityAs of 2004, IMEI format is 14 decimal digits plus a check digit