2001 prentice hall, inc. all rights reserved. 1 chapter 10, wireless communications technologies:...

2001 Prentice Hall, Inc. All rights reserved.

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Chapter 10, Wireless Communications Technologies: Part 2

Outline10.1 Introduction10.2 Wireless Access Technologies

10.2.1 Frequency Division Multiple Access (FDMA) 10.2.2 Time Division Multiple Access (TDMA) 10.2.3 Code Division Multiple Access (CDMA)

10.3 First Generation Technology (1G) and AMPS10.4 Second Generation Technologies (2G)

10.4.1 Personal Communications Services (PCS)10.4.2 Global System for Mobile Communications (GSM)10.4.3 CdmaOne10.4.4 TDMA Technology Family10.4.5 Orthogonal Frequency Division Multiplexing (OFDM)

10.5 2.5G & Third Generation (3G) Technologies10.5.1 High Speed Circuit-Switched Data (HSCSD) 10.5.2 General Packet Radio Service (GPRS)10.5.3 Enhanced Data Rates for Global Evolution (EDGE)10.5.4 CDMA200010.5.5 Wideband Code Division Multiple Access (W-CDMA)


2Chapter 10, Wireless Communications Technologies: Part 2

Outline10.6 Wireless Platforms and Programming Languages

10.6.1 Handheld Devices Markup Languages (HDML)10.6.2 WAP & WML10.6.3 Compact HTML (cHTML) & I-mode10.6.4 Java & Java 2 Micro Edition (J2ME)10.6.5 XML & XHTML10.6.6 EPOC 10.6.7 Binary Run Time Environment for Wireless

(BREW)10.7 SyncML Initative10.8 Future of Wireless Technologies

10.9 Internet and World Wide Web Resources


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10.1 Introduction

• Wireless communications challenges– Standardization

– Security

– Cost of development

• Wireless technology generations– 1G, 2G, 2.5G, 3G, 4G

• Wireless technologies– AMPS, PCS, GSM, FDMA, CDMA and TDMA

• Programming languages and platforms for wireless– WAP, J2ME, cHTML, XML, XHTML


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10.2 Wireless Access Technologies

• Access technologies are used to control and establish how communications take place as well as define guidelines for network development

• Three key access technologies– Frequency Division Multiple Access (FDMA)

– Time Division Multiple Access (TDMA)

– Code Division Multiple Access (CDMA)


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10.2.1 Frequency Division Multiple Access (FDMA)

• One of the first access technologies developed for communications networks

• FDMA assigns each communications transmission to different frequency slots or channels.


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10.2.1 Frequency Division Multiple Access (FDMA)

• Frequency slots are divided into uplinks (channels that handle transmissions from users to base stations) and downlinks (transmissions from base stations to users)

• FDMA searches the available frequency slots and assigns a channel to a user for the duration of the uplink or downlink session.

• No other users can use a channel that is already assigned until the transmission is complete

• FDMA encounters interference problems, inefficiency and transmission interruptions.


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10.2.2 Time Division Multiple Access (TDMA)

• Used worldwide with GSM, CDMA and other popular network technologies

• TDMA takes multiple calls and assigns each call to a different time slot on the same radio frequency


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10.2.2 Time Division Multiple Access (TDMA)

• Two technologies are used by TDMA– Frequency-Division Duplex (FDD)

– Time-Division Duplex (TDD)

• TDD – Uses on frequency band for all stations

– Each station assigned a time slot on the band

• FDD – Uses two separate frequency bands

– Each station is assigned two time slots (one for receiving signals and one for sending signals)

– Time slots are staggered


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10.2.3 Code Division Multiple Access (CDMA)

• One of the more popular standards in the U.S. and internationally

• Uses spread-spectrum technology– Breaks up signals and spreads them over their entire

bandwidth

– Increases capacity up to 3 times that of any other digital system and 20 times that of an analog one

• Uses packet-switched data transmissions– Data is sent and received over a network in groups called

packets

– Packets can be sent on one channel and received on another


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10.2.3 Code Division Multiple Access (CDMA)

• Advantages of CDMA– Less power to transmit signals which increases talk time and

battery life

– Interference and background noise are reduced

– Require fewer cell cites thus reducing network construction time as compared to wireline and other wireless networks


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10.3 First Generation Technology (1G) and AMPS

• First-generation technology uses analog signals: wave-like radio transmissions– Wave sent to base where broken down and routed

– When destination determined, signal recreated and sent

– Quality threatened by recreation errors

• Advanced Mobile Phone Service– Used in areas without digital coverage

– Backup in case of digital system failure

• Coverage– Cells surround base station, base only communicates with

users in cell

– When user switches cells, bases handoff signal


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10.2 First Generation Technology (1G) and AMPS

Original Signal Reproduced Signal

An analog signal before and after being processed at the base station.


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10.4 Second Generation Technologies (2G)

• Second Generation technologies most widely used today and will be primary support for future generations


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10.4.1 Personal Communications Services (PCS)

• 2G digital signals– Binary coding: digital signal form, based on sequence of 0s

and 1s

– Error rate greatly reduced from analog

• Personal Communications Service (PCS)– One of first US digital services

– Uses cells and base stations• Cells broken into microcells (picocells)

• Creates better network coverage and reduces interference


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• PCS types– Narrowband PCS

• 2-way paging, credit card verification, location services, GPS and voice and text paging

– Broadband PCS• Portable computer communications

• GSM is form of PCS network• Sprint PCS

– Driven by CDMA technology– Internet access through cell phones– Can use phone as modem for laptop


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Original Signal Reproduced Signal

Digital signal transmission and reproduction.

A cell that is divided into microcells forPCS communications

Cell Network

MicrocellsCells


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10.4.2 Global System for Mobile Communications (GSM)

• Global System for Mobile Communications: digital communications network– More calls on same frequency and faster data speeds

– Roaming technology: complete communication from anywhere in world

• Providers establish roaming areas: higher cost for users when outside home area

– GSM offers SMS service

• GSM accepted as standard in Europe and Asia


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10.4.3 CdmaOne

• CdmaOne: technologies and standards associated with CDMA– Telecommunications Industry Association (TIA) and

International Telecommunications Union (ITU) regulate standards

– Part of the IS-95 Standards group

• CDMA is building block for 2.5G and 3G networks


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10.4.4 TDMA Technology Family

• TDMA is used with other technologies like FDMA and CDMA

• First digital system that transitioned from AMPS to the digital age is D-AMPS– Based on a combinations of FDMA and TDMA

– Also known as TDMA IS-136

• TDMA systems are used worldwide in areas including Latin America and the Middle East


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10.4.5 Orthogonal Frequency Division Multiplexing (OFDM)

• Orthogonal Frequency Division Multiplexing: first used by military, now commercial– Frequency division multiplexing: gives each channel its own

frequency

– Compact signals use less spectrum

– Support both data and voice

– Uses multiple carrier waves to transmit signals, limiting interference and delay

– Wideband OFDM (W-OFDM): development of 3G and 4G technologies using OFDM


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10.5 2.5G & Third Generation (3G) Technologies

• 2.5G Technology: intermediate step between 2G and 3G

• 3G Technology: seven times faster than 56kps modem

• Factors behind growth of these technologies– Spectrum allocation

– Infrastructure development

– Standardization


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10.5.1 High Speed Circuit-Switched Data (HSCSD)

• 2.5G technology• Alternative to packet-switched data• An upgrade to GSM


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10.5.2 General Packet Radio Service (GPRS)

• General Packet Radio Service– Enhances GSM networks

– 2.5G technology

– Packet data traffic channels (PDCHs)• Transmit data packets (like SMS)

• Always on connectivity


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10.5.3 Enhanced Data Rates for Global Evolution (EDGE)

• Enhanced Data Rates for Global Evolution– Transmission speed of 384kbps (3G)

– Always on connectivity

– Built over existing networks• Leads to bandwidth and channel allocation limitations

– Data only transmissions and voice technologies


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10.5.4 CDMA2000

• 2.5G alternative• CDMA2000 is family of technology types

– CDMA 1xMC Similar to EDGE• 1xMC upgrades voice and data capacity

– CDMA 1xEV• Separates voice and data into two separate channels

• 1xEV-DO: data only transmissions

• 1xEV-DV: expands DO to handle voice

– CDMA 3xMC• Upgrade 1xMC to 3G networks

• Similar to UMTS – voice and data


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10.5.4 CDMA2000

• Drawback to CDMA2000– Competing companies develop different versions within

CDMA2000 family• No standardization

– CDMA2000 is in direct competition with W-CDMA


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10.5.5 Wideband Code Division Multiple Access (W-CDMA)

• 3G CDMA technology• ITU’s Universal Mobile Telecommunications

System standard and new frequency spectrum• W-CDMA supports circuit-switched and packet-

switched data– All transmissions use same frequency

– Determines signal’s speed and path individually

• Developed by NTT DoCoMo• Uses single wave transmissions

– Short-bursts instead of continuous

– Occupy channels briefly


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10.6 Wireless Platforms & Programming Languages

• No unifying standard• Protocols, platforms and languages are important

developmental/implementation tools


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10.6.1 Handheld Devices Markup Language (HDML)

• Handheld Devices Markup Language (HDML)– One of first languages for handheld devices

– Similar to HTML

– Evolved into WAP and WML

• HDML no longer manufactured, but still present in many devices


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10.6.2 WAP and WML

• Wireless Access Protocol (WAP)– Set of protocols enabling communication between different

wireless devices

– Intended for phones, pagers and other handhelds

• Wireless Markup Language (WML)– Creates web content for wireless devices, based on XML

– Microbrowsers: access web via wireless internet

– WML supports WAP

– Deck: a WML document made up of cards

– Image support and telephone support through telephony tags


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10.6.2 WAP and WML

• WAP limitations– Security breaches and unreliability

– Limited bandwidth• Can’t handle multimedia and overloaded easily

• WAP communications– WAP-enabled mobile device

– WAP gateway

– Web server

WAP Communications Architecture. (Courtesy of Jason Manger, WAPuSeek)


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10.6.3 Compact HTML (cHTML) & i-mode

• i-mode: popular service in Japan for voice, text, graphics and web-browsing– Uses cHTML, subset of HTML

– NTT DoCoMo has over 30,000 cHTML pages on own servers – eliminates translation


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10.6.4 Java and Java 2 Micro Edition (J2ME)

• Java: one of most widely used programming languages

• Java 2 Micro Edition (J2ME): programming platform for mobile devices– Facilitates development of applications on wireless devices

– Compensates for WAP’s drawbacks


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10.6.5 XML & XHTML

• XML: an open technology for data exchange– XML documents contain data, applications decide how data

is displayed

– Markup languages created with XML• XHTML

• XHTML Basic

• VoiceXML

• WBXML

– Markup documents• Tags mark and describe data

• Documents are highly portable

• Human and machine readable


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10.6.5 XML & XHTML

• XHTML– Markup language identifies page’s elements

– Equipped to represent complex data on wireless internet

– Strict syntax and well-formed code


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10.6.6 EPOC

• EPOC: a platform for next generation wireless devices– Supports phone and PDA for 2.5G and possibly 3G

technologies

– Supports C++, Java, WAP and the internet; TCP/IP protocols, GSM, Bluetooth and infrared

Ericsson R380 phone which uses the EPOC operating system. (Courtesy of Ericsson)


3710.6.7 Binary Runtime Environment for Wireless

(BREW)• Qualcomm’s platform enables applications

accessible by variety of wireless devices– Ease of use and development – lower costs and production

times

– Many possible applications• Navigation

• E-wallets

• Games

• Music


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10.7 SyncML Initiative

• Synchronization– Sharing information in multiple areas among non-compatible

devices

• SyncML Initiative– Formed by 8 companies to develop standard protocol for

information exchange regardless of time, place or device

– Remote synchronization: application used by two devices at same time

– Works with fixed, infrared, cable or Bluetooth wireless technology networks

– Divides synchronization areas into client-side and server-side

– SyncML based on WBXML version of XML


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10.7 SyncML Initiative

Sync Type Description

2-way sync Updates information on both the client and server side.

1-way sync from client only Allows user to download information from the server that has changed but the server is not updated with new information from the client

1-way sync from server only Allows server to access information from the client but the new information from the server is not updated on the client.

Refresh from client only Special case in which the server updates the information on the client without a request.

Refresh from server only Special case in which the client updates information on the server without a request.

Server Alert Message Server message to notify client it is ready for a syncing process.

Client Alert Message Client message to notify server that it is ready for syncing process.

Fig. 10.9 Types of synchronizations and messages associated with SyncML. (Courtesy of SyncML).


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10.8 Future of Wireless Technologies

• Advances in transmission speed and types of information– 3G standards, technologies and protocols in development

– Possibly 4G technologies by 2010

• Multimedia communications will be dominant transmission type of future