Bikash Sadhukhan. M.Tech(CSE)

Lecturer. Dept of CSE/IT

Techno India College of Technology

Mobile Communication

� Entails transmission of data to and from handheld

devices

� Two or more communicating devices

� At least one is handheld or mobile� At least one is handheld or mobile

� Location of the device can vary either locally or

globally

� Communication takes place through a wireless,

distributed, or diversified network

Brief history of Wireless communication

� 1901 Marconi’s first demonstration of transatlantic wireless

communication using electromagnetic waves

� 1907 onwards commercial transatlantic communication

� 1920 discovery of short waves by Marconi

� 1928 many TV broadcast trials

� 1950s-1970s --- Some commercial installations of fixed wireless � 1950s-1970s --- Some commercial installations of fixed wireless

telephony, e.g., A-Netz and Bnertz systems in Germany

� 1970 ALOHANET: first packet radio network (University of Hawaii)

� 1979 Nordic Mobile Telephony (NMT) system

� 1981 start of Global Spéciale Mobile (GSM) specification

� 1982 start of American Advanced Mobile Phone System (AMPS)

specification

� 1984 CT-1 standard (Europe) for cordless telephones

� 1991 Digital European Cordless Telephony (DECT)

Brief history of Wireless communication� 1992 Start of GSM

� 1996 High Performance Radio Local Area Network (HiperLAN)

� 1997 wireless LAN standard IEEE802.11 released

� 1998 specification of the Universal Mobile Telecommunication System

(UMTS) as European proposal for IMT-2000

� 1999 new wireless LAN standards – 802.11b and 802.11a

� 1999 first specification of Bluetooth

� 2000 GSM with higher data rates and first GPRS trials

� 2001 start of third generation (3G) systems

� 2001 specification of the fixed wireless broadband standard IEEE 802.16

(WiMax) released

� 2003 Improved version IEEE 802.16a released

� 2003 IEEE802.11g released

� 2003 IEEE 802.15.4 standard released (which eventually led to the

development of the ZigBee application stack)

Guided Transmission

� Metal wires and optical fibres guided or wired

transmission of data

� Guided transmission of electrical signals takes

place using four types of cables

� Fibre- and wire- based transmission and their � Fibre- and wire- based transmission and their

ranges:

Four types of cables for Guided

Transmission

1. Optical fibre for pulses of wavelength 1.35–1.5 µm

2. Coaxial cable for electrical signals of frequencies up

to 500 MHz and up to a range of about 40 m

3. Twisted wire pairs ─ for conventional (without

coding) electrical signals of up to 100 kHz and up to a coding) electrical signals of up to 100 kHz and up to a

range of 2 km, or for coded signals of frequencies up to

200 MHz and a range of about 100 m

4. Power lines, a relatively recent advent in

communication technology─ used for long-range

transmission of frequencies between 10 kHz and 525

kHz

Guided Transmission Advantages

� Transmission along a directed path from one point to

another

� Practically no interference in transmission from any

external source or path

� Using multiplexing and coding, a large number of

signal-sources simultaneously transmitted along an

optical fibre, a coaxial cable, or a twisted-pair cable

Guided Transmission Disadvantages

� Signal transmitter and receiver fixed (immobile).

� No mobility of transmission and reception points.

� Number of transmitter and receiver systems limits

the total number of interconnections possiblethe total number of interconnections possible

Unguided─ Wireless Transmission

� Electrical signals transmitted by converting them

into electromagnetic radiation

� Radiation transmitted via antennae that radiate

electromagnetic signalselectromagnetic signals

� Various frequency bands within the

electromagnetic spectrum

� Different transmission requirements

� f = c/λ = (300/ λ)MHz [λ in meter]

Classification of wireless networks

Wireless personal area network (WPAN)

� Network between devices carried by a person

Examples

� Interconnection between a mobile phone and a headset

� Interconnection between a laptop and projector

equipmentequipment

� Wearable computing: everything from helmets,

sunglasses to clothes

Technologies

� InfraRed (IrDA)

� IEEE 802.15 radio standards

Wireless local area network (WLAN)

� Network between devices in home and office

environment; typically gives access to a fixed

infrastructure

� Examples:

� Interconnection of stationary and mobile devices such as

desktops, laptops, telephones, television, etc.desktops, laptops, telephones, television, etc.

� Internet access at public venues such as airports,

restaurants, conferences, etc.

� Technologies

� IEEE 802.11 radio standards (WiFi)

� Digital Enhanced Cordless Telephony (DECT)

Wireless metropolitan area network

(WMAN)

Wireless Wide area networks (WWAN)

Range vs. data rate

Wireless transmission fundamentals

Frequency spectrum

Radio propagation

� Signals and antennasSignals and antennas

� Modulation

� Channel conditions

� Effects of mobility

Multiple access

Medium access control

Frequencies for communication

Frequencies for communication

Orderly use of frequency spectra reduces interference

� International Telecommunications Union (ITU) for worldwide

coordination

� Federal Communications Commission (FCC) in the US

� European Conference for Posts and Telecommunications (CEPT) and

European Telecommunication Standards Institute (ETSI) in EuropeEuropean Telecommunication Standards Institute (ETSI) in Europe

� License spectrum is allocated for proprietary use, e.g., cellular

communication

� Unlicensed spectrum is available for general use (with restrictions),

e.g., 2.4 GHz ISM band

Mobile devices

Effects of device portability

Wireless networks in comparison to

fixed networks

Simple reference model used here

Influence of mobile communication

to the layer model

Development of mobile communication

systems

First and Second Generations (1G & 2G)

� First generation wireless devices only voice signals

� Second generation (2G) devices communicate voice as

well as data signals have data rates of up to 14.4 kbps

� The 2.5G and 2.5G+ are enhancements of the second � The 2.5G and 2.5G+ are enhancements of the second

generation and support data rates up to 100 kbps

Third generation (3G) mobile devices

communication

� Higher data rates than 2G and support voice, data,

and multimedia streams

� Facilitates data rates of 2 Mbps� Facilitates data rates of 2 Mbps

� Data rates are higher for short distances and 384 kbps

for long distance transmissions

� Enable transfer of video clips and faster multimedia

communication

AMPS

� AMPS is an analog cellular phone system using

FDMA.

� Invented by Bell Labs and first installed in the United

States in 1982. It was also used in EnglandStates in 1982. It was also used in England

D-AMPS

� The second generation of the AMPS systems is D-

AMPS and is fully digital.

� D-AMPS was carefully designed to co-exist with � D-AMPS was carefully designed to co-exist with

AMPS so that both first- and second-generation

mobile phones could operate simultaneously in the

same cell.

GSM - Global System for Mobile

CommunicationGSM offers

� several types of connections� voice connections, data connections, short message service

� multi-service options (combination of basic services)

Three service domains:

� Bearer Services: � Bearer Services: � Telecommunication services to transfer data between access points

� data service (circuit switched)� synchronous: 2.4, 4.8 or 9.6 kbit/s

� asynchronous: 300 -1200 bit/s

� data service (packet switched)� synchronous: 2.4, 4.8 or 9.6 kbit/s

� asynchronous: 300 -9600 bit/s

GSM service domains

� Telematic Service

� Telecommunication services that enable voice communication via mobile phones

� Offered services

� Mobile telephony: Primary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz telephony offering the traditional bandwidth of 3.1 kHz

� Emergency number: Common number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible)

� Voice mailbox (implemented in the fixed network supporting the mobile terminals)

� Electronic mail (MHS - Message Handling System, implemented in the fixed network)

� Short Message Service (SMS)

GSM service domains

� Supplementary Services

� Services in addition to the basic services, cannot be

offered stand-alone

� Similar to ISDN services besides lower bandwidth due to

the radio link

May differ between different service providers, countries � May differ between different service providers, countries

and protocol versions

� Important services

� identification: forwarding of caller number

� suppression of number forwarding

� automatic call-back

� conferencing with up to 7 participants

� locking of the mobile terminal (incoming or outgoing calls)

Performance characteristics of GSM� Communication

- mobile, wireless communication; support for voice and data services

� Total mobility

- international access, chip-card enables use of access points of different

providers

� Worldwide connectivity

- one number, the network handles localization- one number, the network handles localization

� High capacity

- better frequency efficiency, smaller cells, more customers per cell

� High transmission quality

- high audio quality and reliability for wireless, uninterrupted phone calls

at higher speeds (e.g., from cars, trains)

� Security functions

- access control, authentication via chip-card and PIN

GPRS -General Packet Radio Service

� A packet-oriented service for mobile stations’ data transmission and their access to the Internet

� A speed enhanced data transmission service designed for GSM systems

� Speed enhanced data transmission─ by packetizing data and simultaneous transmission of packets over different channelsdata and simultaneous transmission of packets over different channels

� Uses the unused slots and channels in TDMA mode of a GSM network for packetized transmission from a mobile station

� Data-packets of a single mobile station transmit through a number of time slots

� Advantage: one step towards UMTS, more flexible

� Disadvantage:more investment needed (new hardware)

EDGE (Enhanced Data rates for GSM

Evolution)

� EDGE is a more advanced upgrade tod the GSM

standard and requires the addition of new

hardware and software at existing base stations.

� 8 PSK communication to achieve higher rates of � 8 PSK communication to achieve higher rates of

up to 48 kbps per 200 kHz channel

� High date rates compares to up to 14.4 kbps in

GSM.

� Using coding techniques the rate can be enhanced

to 384 kbps for the same 200 kHz channel

CDMA (Code Division Multiple Access) � CDMA supports high data rates

� Initial evolution of CDMA was 2.5 G. But Nowadays CDMA supports high data

rates and considered as 3G.

� Voice as well as data and multimedia streams.

� CDMA more robust for multi-path delays and provides higher immunity towards

frequency selective fading

� Each mobile station’s or base transceiver’s signals are coded with two or three

codes

� Signals of higher voice and data quality and small bit-error rates

� Soft handover- Soft handover means that an MS at the boundary of two adjacent

cells does not have to drop calls due to signal break during handover at the

boundary region

� CDMA systems provide seamless connectivity to the MS

� CDMA systems perform power control by open loop or close loop methods to solve

the problem of drowning of signals from far mobile terminals by those from the

near terminals

� CDMA systems employ spread spectrum techniques (DSSS and FHSS) for medium

access control thus problems in narrow band transmission not present

UMTS (Universal mobile

telecommunication system)

� Communicates at data rates of 100 kbps to 2 Mbps

� It combines CDMA for bandwidth efficiency and

GSM for compatibility.

� It support several technologies for transmission � It support several technologies for transmission

and gives a framework for security and

management functions.

Comparison of GSM and CDMA

Mobile computing─ A Definition

� The process of computation on a mobile device

� In mobile computing, a set of distributed

computing systems or service provider servers

participate, connect, and synchronize through participate, connect, and synchronize through

mobile communication protocols

� Mobile computing as a generic term describing

ability to use the technology to wirelessly connect

to and use centrally located information and/or

application software through the application of

small, portable, and wireless computing and

communication devices

Mobile computing

� Provides decentralized (distributed) computations

on diversified devices, systems, and networks,

which are mobile, synchronized, and

interconnected via mobile communication interconnected via mobile communication

standards and protocols.

� Mobile device does not restrict itself to just one

application, such as, voice communication

� Offers mobility with computing power

� Facilitates a large number of applications on a

single device

Limitations to mobile computing� Resource constraints: Battery

� Interference: the quality of service (QoS)

� Bandwidth: connection latency

� Dynamic changes in communication environment: � Dynamic changes in communication environment:

variations in signal power within a region, thus link

delays and connection losses

� Network Issues: discovery of the connection-service to

destination and connection stability

� Interoperability issues: the varying protocol standards

� Security constraints: Protocols conserving privacy of

communication