Digital Cellular Telephony - PowerPoint PPT Presentation

Loading...

PPT – Digital Cellular Telephony PowerPoint presentation | free to download - id: 5832a1-ZDBmM



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Digital Cellular Telephony

Description:

Title: Chapter 1: A First Look at Windows 2000 Professional Subject: A Guide to Windows 2000 Professional Author: Anne D. Ketchen Last modified by – PowerPoint PPT presentation

Number of Views:448
Avg rating:3.0/5.0
Slides: 57
Provided by: Ann1169
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Digital Cellular Telephony


1
Digital Cellular Telephony
  • Chapter 8

2
Learning Objectives
  • Describe the applications that can be used on a
    digital cellular telephone
  • Explain how cellular telephony functions
  • List and describe the features of the generations
    of cellular telephony
  • List and describe the four types of client
    software used on a digital cellular telephone
  • Discuss the issues surrounding 3G implementation

3
Digital Cellular Telephony
  • Although commonplace, digital cellular telephony
    is most competitive and complex of all wireless
    telephony
  • Variety of competing technologies such as GSM and
    CDMA2000 1XEVDO rather than single standard
  • Competing carriers each push a specific
    technology
  • Governments have even auctioned off part of
    wireless spectrum to highest bidder

4
Applications
  • New and expanded features and applications are
    pushing wireless digital cellular networks beyond
    just voice communications
  • Digital cellular telephony can be used for
    Internet access, e-mail, video conferencing, and
    running a variety of programs

5
Short Message Services (SMS)
  • Short Message Services (SMS) delivers text-based
    messages up to 160 characters directly between
    wireless devices without using the Internet
  • SMS is popular in Europe and Japan with over 200
    billion messages sent annually
  • SMS is slow in reaching the US because of
    profusion of other wireless digital alternatives

6
How Cellular Telephony Works
  • Two keys to cellular telephone networks
  • Coverage area is divided into cells, each with a
    cell transmitter connected to base station that,
    in turn, is connected to mobile
    telecommunications switching office (MTSO)
  • See Figure 8-1
  • All the transmitters and cell phones operate at
    low power level to prevent signals from
    interfering with other cells that may use same
    frequencies
  • See Figure 8-2

7
Cellular Network
8
Frequency Reuse
9
Cellular Telephone Codes
  • Special codes are associated with cell phones
  • Codes identify phone, phones owner, and carrier
    or service provider
  • Table 8-1 summarizes the codes

10
Cellular Telephone Codes
11
Cellular Telephone Handoffs and Roaming
  • When telephone user moves within same cell, base
    station handles transmissions
  • Handoff is when user moves to another cell and is
    automatically associated with base station of
    that cell
  • Roaming is when user moves beyond coverage area
    of entire cellular network into remote area, as
    seen in Figure 8-3
  • Network in remote area contacts home network to
    verify that user can make calls and is charged
    appropriately

12
Handoff and Roaming
13
How a Cellular Phone Receives a Call
  • Cell phone listens for SID transmitted by base
    station on control channel
  • If SID matches that programmed into phone, cell
    phone transmits registration request to base
    station that MTSO uses
  • If SID does not match, cell phone is roaming and
    MTSO of remote network contacts MTSO of home
    network to confirm SID is valid

14
How a Cellular Phone Receives a Call
  • MTSO locates phone and selects frequency which is
    sent to phone over control channel
  • As user moves to edge of cell, base stations
    coordinate through MTSO and instruct phone to
    change frequencies as it is handed off to another
    cell
  • See Figure 8-4

15
Receiving a Call
16
Digital Cellular Telephony
  • Existing since the early 1980s in the United
    States, cellular telephony is divided into
    several generations
  • First Generation
  • Second Generation
  • 2.5 Generation
  • Third Generation

17
First Generation
  • 1G uses analog signals and has 9.6 KHz maximum
    transmission speed
  • Based on Advanced Mobile Phone Service (AMPS), 1G
    uses 800-900 MHz frequency
  • Each channel is 30 KHz wide with 45 KHz passband
  • 832 frequencies are available, with 790 used for
    voice traffic and 42 for control channel
  • Two frequencies are required for conversation,
    so there are actually only 395 voice channels
    and 21 control channels

18
First Generation
  • AMPS uses Frequency Division Multiple Access
    (FDMA), as illustrated in Figure 8-5
  • User is allocated single channel at a time and
    is switched to another channel if original one
    deteriorates or has interference
  • 1G networks use circuit-switching technology
  • Because analog signals are prone to interference,
    1G is used basically for voice
  • It has been replaced with improved digital
    technology

19
FDMA
20
Second Generation
  • Started in early 1990s, 2G uses digital
    transmissions to transmits data between 9.5 Kbps
    and 14.4 Kbps in 800 MHz and 1.9 GHz frequencies
  • Offers several advantages over analog, including
  • More efficient uses of frequency spectrum
  • Quality of voice transmission does not degrade
    over distance
  • Better security more difficult to decode
  • Requires less transmitter power
  • Uses smaller and less expensive individual
    receivers and transmitters

21
Second Generation
  • 2G cellular networks use three different multiple
    access technologies summarized in Table 8-2
  • Time Division Multiple Access (TDMA), shown in
    Figure 8-6, allows 3 times as many calls over a
    single channel as FDMA
  • Code Division Multiple Access (CDMA) allocates
    entire spectrum all the time, as seen in Figure
    8-7
  • Global Systems for Mobile Communications (GSM)
    divides a 25 MHz channel into 124 frequencies,
    each 200 KHz, and then uses 8 time slots to
    transmit up to 9.6 Kbps

22
TDMA
23
CDMA
24
2G Technologies
25
2.5 Generation
  • 2.5G is regarded as an interim generation
  • Sparsely deployed 2.5G networks operate at 384
    Kbps
  • Packet-switched 2.5G networks have two advantages
    over circuit switched networks
  • More efficient, increasing traffic from 3 to 5
    times over that of circuit-switching
  • Always on with connection kept open all the time

26
2.5 Generation
  • 2.5G networks use three technologies
  • General Packet Radio Service (GPRS) uses 8 time
    slots in a 200 KHz spectrum to transmit at speeds
    up to 114 Kbps
  • Enhanced Data Rates for Global Evolution (EDGE)
    uses new modulation technique to transmit up to
    384 Kbps
  • CDMA2000 1XRTT supports 144 Kbps packet data
    transmissions

27
Third Generation
  • 3G is intended to be a uniform global worldwide
    standard for cellular wireless communication
  • International Telecommunications Union (ITN) has
    outlined standard data rates for wireless digital
    networks
  • 144 Kbps for a mobile user
  • 386 Kbps for slowly moving user
  • 2 Mbps for stationary user

28
Third Generation
  • Transition from CDMA2000 1XRTT is to CDMA200
    1XEVDO with data transmission rates of 2.4 Mbps
  • Must be coupled with CDMA2000 1XRTT for both
    voice and data transmissions
  • CDMA2000 1XEVDV will send both voice and data
  • Transition from EDGE is Wideband CDMA (WCDMA)
  • Adds packet-switching data channel to
    circuit-switched voice channel to transmit at 2
    Mbps in fixed position and at 300 Kbps when mobile

29
Third Generation
  • Several 3G technologies not yet tested
  • Actual technologies may be different from those
    currently proposed
  • Figure 8-8 shows digital wireless cellular
    migration paths
  • Table 8-3 summarizes digital cellular technologies

30
Digital Wireless Cellular Migration Path
31
Digital Cellular Technologies
32
Client Software
  • Client software that functions on wireless
    digital cellular devices provide function and
    user interface to display or manipulate data
  • Some client software is unique to cellular
    telephones
  • Other software may be used in a variety of
    different applications

33
Wireless Application Protocol (WAP)
  • WAP provides standard way to transmit, format,
    and display Internet data on cellular phones
  • Display only textual data because of slow
    transmission speed and smaller viewing area, as
    seen in Figure 8-9
  • Has a microbrowser that uses Wireless Markup
    Language (WML) instead of HTML, as seen in Figure
    8-10
  • A WAP Gateway, also called a WAP Proxy, changes
    HTML into WML before forwarding it to cell phone,
    as seen in Figure 8-11

34
WAP Display
35
HTML Code
36
WAP
37
HTML and WML Differences
  • HTML controls layout, color, font, and styling,
    while WML controls only font size and basic font
    attributes, as seen in Figure 8-12
  • WML uses Extensible Markup Language (XML) and
    tags that specify how content should be formatted
  • WML document, called a deck, contains one or more
    blocks called cards that contain small parts of a
    text document and navigation controls
  • One card is displayed on the cell phone at a time
    as seen in Figure 8-13

38
WML Code
39
WML Deck
40
i-Mode
  • i-Mode, a Japanese-owned Internet access system,
    is based on compact HTML (cHTML)
  • Has its own set of tags and attributes
  • Users are charged for the service by amount of
    information downloaded plus a service charge
  • Expect i-Mode and WAP to merge into one
    technology in the future

41
Java
  • Developed by Sun Microsystems, Java is an
    object-oriented language that runs on almost any
    hardware platform
  • Java 2 Micro Edition (J2ME) was specifically
    developed for programming wireless devices
  • Allows cellular phone to access remote
    applications and email
  • Can also run programs on cellular phone itself

42
Binary Runtime Environment for Wireless (BREW)
  • BREW, a runtime environment, is a thin software
    interface, that resides on wireless device
  • Users can download programs and run them on
    BREW-enabled devices
  • BREW uses memory efficiently, occupying only a
    small amount of flash memory and dynamically
    allocating RAM
  • Can be used in combination with other operating
    systems and any kind of browser

43
Limitations and the Future
  • WAP and i-Mode allow remote access to the
    Internet
  • They do not support a rich set of graphics
  • J2ME and BREW are expected to become major
    platforms for variety of wireless devices

44
Digital Cellular Issues and Outlook
  • Several issues face digital cellular telephony
    that prevent its rapid acceptance
  • Competing technologiesno single road to 3G
    digital telephony competing technologies are
    incompatible
  • Limited spectrum availabilityNo part of spectrum
    is designated exclusively for 3G is enough
    spectrum available to meet needs

45
Digital Cellular Issues and Outlook
  • Several issues face digital cellular telephony
    that prevent its rapid acceptance
  • High infrastructure costs3G telephones may cost
    as much as 300 with 90 monthly charge carriers
    will spend billions for infrastructure necessary
    for 3G
  • Competition from other wireless
    optionsBluetooth, IrDA, and 802.11a WLANs are
    less-expensive choices

46
Chapter Summary
  • Two keys to cellular telephone networks are
    dividing coverage area into cells and using low
    power levels for transmission
  • At the center of each cell is a cell transmitter
    that sends and receives radio frequency (RF)
    signals
  • Low-power levels enable signals to stay confined
    to the cell and not interfere with other cells
    that use the same frequencies

47
Chapter Summary
  • All cell phones have special codes that identify
    the owner and carrier or service providers
  • Handoff is when user moves to another cell and is
    automatically associated with base station of new
    cell

48
Chapter Summary
  • Roaming occurs when a user moves beyond coverage
    area of entire cellular network and connects to
    network in remote area
  • Remote area network communicates with home area
    to verify that user can make calls and is charged
    appropriately

49
Chapter Summary
  • First generation of wireless cellular technology,
    known as 1G, uses analog signals and transmits at
    a maximum speed of 9.6 Kbps
  • 1G uses Advanced Mobile Phone Service (AMPS)
    standard
  • Operates in 800-900 MHz frequency
  • Uses Frequency Division Multiple Access (FDMA)
  • Is circuit-switching technology

50
Chapter Summary
  • Second generation, known as 2G, transmits data
    between 9.6 Kbps and 14.4 Kbps in 800 MHz and
    1.9 GHz frequencies
  • Circuit-switched digital technology
  • Use three different multiple access technologies
  • Time Division Multiple Access (TDMA)
  • Code Division Multiple Access (CDMA)
  • Global Systems for Mobile (GSM) communications

51
Chapter Summary
  • Currently, three variations in 2.5G interim
    generation of packet-switching network
    technologies
  • General Packet Radio Service (GPRS) is for TDMA
    or GSM 2G networks
  • Enhanced Data Rates for Global Evolution (EDGE)
    is considered a booster for GPRS systems and
    can transmit up to 384 Kbps using a new
    modulation technique
  • CDMA2000 1XRTT supports 144 Kbps packet data
    transmission and doubles voice capability of
    current CDMA networks

52
Chapter Summary
  • 3G digital networks transmit at higher speeds and
    provide new or expanded applications and features
  • Will require major changes to network
    infrastructures and a new generation of mobile
    cellular devices
  • Widely used in Europe and Japan, Short Message
    Services (SMS) allows delivery of text-based
    messages directly between wireless devices

53
Chapter Summary
  • Client software on cell phone is necessary for
    Internet surfing or videoconferencing
  • Wireless Application Protocol (WAP) provides a
    standard way to transmit, format, and display
    Internet data without requiring rich user
    interface
  • WAP cell phone runs microbrowser that uses
    Wireless Markup Language (WML) to display
    text-based Web content
  • A WAP Gateway must translate between WML and HTML

54
Chapter Summary
  • I-mode, another client technology, is based on
    compact HTML (cHTML)
  • It has its own set of tags and attributes
  • Expected I-mode and WAP to merge into one
    technology in the future
  • Java 2 Micro Edition (J2ME) is a Java subset for
    programming wireless devices
  • Allows cellular phones to access remote
    applications and e-mail programs as well as run
    programs

55
Chapter Summary
  • Binary Runtime Environment for Wireless (BREW), a
    thin software interface layer, resides on a
    wireless device
  • Allows users to download programs and run them on
    BREW-enabled devices
  • Competing cellular technologies, lack of
    standards, spectrum limitations, and high costs
    of implementing 3G technology have prevented
    rapid acceptance of advanced generations of
    digital cellular telephony

56
Chapter Summary
  • 3G networks have competition from other wireless
    technologies
  • Top speed for 3G is 2 Mbps standing still, but
    802.11a WLANs offer speeds over 100 Mbps while
    mobile
  • Some carriers install less-expensive stable WLANs
    in high-traffic hot spots in selected cities as
    alternative to 3G
About PowerShow.com