Conducted and Wireless Media - PowerPoint PPT Presentation


Title: Conducted and Wireless Media


1
Lecture 03
  • Conducted and Wireless Media

2
Introduction
  • Communications are conducted through a medium,
  • For example, we talked, our voice transmitted
    through air
  • Thus, the world of computer networks would not
    exist if there were no medium by which to
    transfer data
  • The two major categories of media include
  • Conducted media
  • Wireless media
  • How to subscribe them for organizations?
  • Selection criteria

(to p4)
(to p28)
(to p65)
(to p3)
Application examples
3
Application examples
  • Conducted
  • Example 1
  • Example 2
  • Wireless
  • Example 1
  • Example 2
  • Example 3

(to p71)
(to p73)
(to p74)
(to p75)
(to p77)
4
Conducted media
  • Physical connection between source and sink
    points
  • Three common media
  • i) wire
  • ii) coaxial cable
  • iii) optical fiber
  • Comparison between their transmission speeds

(to p5)
(to p10)
(to p13)
(to p27)
(to p2)
5
i) wire
  • usually made of copper with a pair of wire
  • Or called twisted pair of wire
  • the pairs of wires are almost insulated with
    plastic coating and twisted together -- known as
    twisted pair wires
  • (see Figure 9-6)
  • Categorizations
  • the twisting has the effect of electrically
    canceling the signals radiating form each wire
    ---- prevents the signals on one pair of wires
    from interfering the adjacent pair
  • the effect is known as crosswalk

(to p6)
(to p9)
(to p4)
6
FIGURE 9-6 Twisted pair wires are the most
commonly used medium for communications
transmission.
(to p5)
  • As to oppose different layout as shown in Figure
    3.2
  • Different ways of twisted pair way adopted in
    industries

(to p7)
(to p5)
(to p8)
7
(to p6)
8
(to p6)
9
(to p5)
10
ii) coaxial cable
  • Cable that made of several layers of material
    around a central core, which often a copper wire
  • (see Figure 9-8)
  • has a very wide bandwidth (400 Mhz to 600 Hhz),
    thus carries a very high data capacity
  • one coaxial cable carries up to 10,800 voice
    conversations or over 50 television channles
  • Its max capacity is dependent on the thickness of
    the copper wire
  • Two main applications

(to p12)
(to p11)
11
ii) coaxial cable (cont.)
  • It has two main applications
  • 1) Baseband coaxial technology uses digital
    signaling in which the cable carries only one
    channel of digital data
  • 2) Broadband coaxial technology transmits analog
    signals and is capable of supporting multiple
    channels
  • Disadv it is easy to tape and thus lack of a
    high security measure

(to p4)
12
FIGURE 9-8 Parts of a coaxial cable.
(to p10)
13
iii) optical fiber
  • Is a new media for comm
  • is a very thin glass fiber which core provides
    the transmission capability
  • the core is surrounded by another type of glass
    called cladding, which protected by a plastic
    coating
  • (see Figure 9-9) (to p14)
  • data is placed on with a light source or a laser.
    Light source stays in the core as the cladding
    has a low refractive index

(to p17)
14
FIGURE 9-9 Parts of optical fiber cable.
(to p13)
(to p15)
Alternative view
15
(to p16)
Thin vs. Thick fiber optic cable
(to p13)
16
Fiber-Optic Cable (continued)
  • Fiber-optic cable is capable of supporting
    millions of bits per second for 1000s of meters
  • Thick cable (62.5/125 microns) causes more ray
    collisions, so you have to transmit slower. This
    is step index multimode fiber. Typically use LED
    for light source, shorter distance transmissions
  • Thin cable (8.3/125 microns) very little
    reflection, fast transmission, typically uses a
    laser, longer transmission distances known as
    single mode fiber

(to p15)
17
iii) optical fiber (cont.)
  • Two primary types of fiber
  • a) single mode
  • b) multi mode
  • How more lights can be traveled together
  • Layout of optical fiber worldwide
  • Fiber optic cable is difficult to splice -
    requires a reflectometer to detect such work
  • SONET concept
  • Adv
  • Disv

(to p18)
(to p19)
(to p20)
(to p22)
(to p24)
(to p25)
(to p4)
18
(to p17)
19
Wavelength division
  • Wavelength division multiplexing
  • A technique which allows many light beams of
    different wavelengths can travel along a single
    fiber simultaneously without interfering with one
    another

(to p17)
20
FIGURE 9-10a The worlds undersea cable
network.
(to p21)
21
FIGURE 9-10b Continued
(to p17)
22
SONET
  • Synchronous Optical Network
  • A technique facilitates easy to connect carriers
    that using different brands/products of their
    optical networks
  • It is a standard for the ANSI (American National
    Standard Institute)
  • Transmission rate at Gpbs
  • Data speed for different networks

(to p23)
(to p17)
23
FIGURE 9-11 Comparative data rates for the
SONET and ITU-T optical fiber transmission
standards.
(to p22)
24
iii) optical fiber (cont.)
  • Advantages
  • 1) do not radiate signal as all electrical
    devices do
  • 2) fiber is of light weight
  • 3) cost of fibers is getting cheaper
  • 4) high bandwidth - high data capability
  • 5) little lost of signal strength
  • 6) excellent isolation between parallel fiber -
    crossed-talk between fiber does not exist
  • 7) very secure, difficult to tape

(to p17)
25
Disv
  • Because fiber-optic cable is susceptible to
    reflection (where the light source bounces around
    inside the cable) and refraction (where the light
    source passes out of the core and into the
    surrounding cladding), thus Fiber-optic cable is
    not perfect either. Noise is still a potential
    problem

(to p26)
Concepts of refraction and reflection
(to p17)
26
Fiber-Optic Cable (continued)
(to p25)
27
Conducted Media
(to p4)
28
Wireless media
  • Technically speaking in wireless transmissions,
    space is the medium
  • Radio, satellite transmissions, and infrared
    light are all different forms of electromagnetic
    waves that are used to transmit data
  • Their frequencies of transmission
  • Different types of applications
  • Comparisons

(to p29)
(to p30)
(to p63)
(to p2)
29
Wireless Media (continued)
(to p28)
30
Applications
  • i) microwave radio
  • ii) satellite
  • iii) cellular phones
  • Iv) Infrared Transmissions
  • v) Wireless Application Protocol (WAP)
  • Broadband Wireless Systems
  • Bluetooth
  • Wireless Local Area Networks
  • Free Space Optics and Ultra-Wideband

(to p31)
(to p35)
(to p43)
(to p52)
(to p53)
(to p56)
(to p59)
(to p60)
(to p61)
(to p28)
31
iv) microwave radio
  • Is a medium most common carriers for long
    distance comm (how it looks like )
  • transmit in the range of 4-28 Ghz freq range
  • up to 6000 voice circuits are carried in a 30 Mhz
    wide radio channel
  • travel in a straight line - ie must transmit and
    receive in a direct line of sight , and signals
    will not pass through solid objects
  • requirement

(to p32)
(to p33)
(to p34)
32
Terrestrial Microwave Transmission (continued)
(to p31)
33
Terrestrial Microwave Transmission (continued)
(to p31)
34
iv) microwave radio (cont.)
  • requires to set up an antenna in the range of 20
    to 30 miles
  • Capable to carry either analog and digital form
  • Disadv
  • may interfere by the weather condition (why?)

(to p30)
35
v) satellite
  • Use of microwave radio, the signal travels from a
    ground station on earth to a satellite and back
    to another ground station
  • Satellites can be classified by how far out into
    orbit each one is (LEO, MEO, GEO, and HEO)
  • radio signal is beamed to the satellite on a
    specific frequency called uplink where
    rebroadcast on a different frequency called
    downlink

(to p36)
(to p39)
36
Satellite Microwave Transmission (continued)
  • LEO (Low-Earth-Orbit) 100 to 1000 miles out
  • Used for wireless e-mail, special mobile
    telephones, pagers, spying, videoconferencing
  • MEO (Middle-Earth-Orbit) 1000 to 22,300 miles
  • Used for GPS (global positioning systems) and
    government
  • GEO (Geosynchronous-Earth-Orbit) 22,300 miles
  • Always over the same position on earth (and
    always over the equator)
  • Used for weather, television, government
    operations
  • HEO (Highly Elliptical Earth orbit) satellite
    follows an elliptical orbit
  • Used by the military for spying and by scientific
    organizations for photographing celestial bodies

Their positions on the orbit
(to p35)
(to p37)
37
Satellite Microwave Transmission (continued)
(to p38)
(to p36)
38
Satellite Transmission (continued)
(to p37)
39
v) satellite (cont.)
  • Due to the security reason, information that
    being sent is first encrypted so that tapping and
    interpret its content is difficult
  • there exists a delay of receiving information ---
    called propagation delay, is called as
  • distance apart of comm device
  • ------------------------------------
    -----
  • speed in which data is transmitted
  • example

(to p40)
40
v) satellite (cont.)
  • If satellite is 22,300 mile from the ground and
    speed sending data is 186,000 miles per second,
    then
  • 2 x 22,300
  • Propagation delay ----------------
  • 18,6000
  • 0.2398 sec
  • Classifications by their configuration

(to p41)
41
Satellite (continued)
  • Satellite microwave can also be classified by its
    configuration
  • Bulk carrier configuration
  • Multiplexed configuration
  • Single-user earth station configuration (e.g.
    VSAT)

Their semantic view
(to p42)
(to p30)
42
Satellite Microwave Transmission (continued)
(to p41)
43
Cellular Telephones
  • Wireless telephone service, also called mobile
    telephone, cell phone, and PCS
  • To support multiple users in a metropolitan area
    (market), the market is broken into cells
  • Each cell has its own transmission tower and set
    of assignable channels
  • Different generations of MP

(to p44)
(to p45)
(to p46)
44
Cellular Telephones (continued)
(to p43)
45
Cellular Telephones (continued)
(to p43)
46
Cellular Phones
  • 1st generation
  • 2nd generation
  • 2.5 generation
  • 3rd generation

(to p47)
(to p48)
(to p49)
(to p50)
(to p30)
47
Cellular Telephones (continued)
  • 1st Generation
  • AMPS (Advanced Mobile Phone Service) first
    popular cell phone service used analog signals
    and dynamically assigned channels
  • D-AMPS (Digital AMPS) applied digital
    multiplexing techniques on top of AMPS analog
    channels

(to p46)
48
Cellular Telephones (continued)
  • 2nd Generation
  • PCS (Personal Communication Systems)
    essentially all-digital cell phone service
  • PCS phones came in three technologies
  • TDMA Time Division Multiple Access
  • CDMA Code Division Multiple Access
  • GSM Global System for Mobile Communications

(to p46)
49
Cellular Telephones (continued)
  • 2.5 Generation
  • ATT Wireless, Cingular Wireless, and T-Mobile
    now using GPRS (General Packet Radio Service) in
    their GSM networks (can transmit data at 30 kbps
    to 40 kbps)
  • Verizon Wireless, Alltel, U.S.Cellular, and
    Sprint PCS are using CDMA2000 1xRTT (one carrier
    radio- transmission technology) (50 kbps to 75
    kbps)
  • Nextel uses IDEN technology

(to p46)
50
Cellular Telephones (continued)
  • 3rd Generation
  • UMTS (Universal Mobile Telecommunications System)
    also called Wideband CDMA
  • The 3G version of GPRS
  • UMTS not backward compatible with GSM (thus
    requires phones with multiple decoders)
  • 1XEV (1 x Enhanced Version) 3G replacement for
    1xRTT
  • Will come in two forms
  • 1xEV-DO for data only
  • 1xEV-DV for data and voice

(to p46)
51
(No Transcript)
52
Infrared Transmissions
  • Transmissions that use a focused ray of light in
    the infrared frequency range
  • Very common with remote control devices, but can
    also be used for device-to-device transfers, such
    as PDA to computer

(to p30)
53
Wireless Application Protocol (WAP)
  • WAP is a set of protocols that allows wireless
    devices such as cell phones, PDAs, and two-way
    radios to access the Internet
  • WAP is designed to work with small screens and
    with limited interactive controls
  • WAP incorporates Wireless Markup Language (WML)
    which is used to specify the format and
    presentation of text on the screen
  • Their applications

(to p54)
(to p55)
54
Wireless Application Protocol (WAP) (continued)
(to p53)
55
Wireless Application Protocol (WAP) (continued)
  • WAP may be used for applications such as
  • Travel directions
  • Sports scores
  • E-mail
  • Online address books
  • Traffic alerts
  • Banking and news
  • Possible short-comings include low speeds,
    security, and very small user interface

(to p30)
56
Broadband Wireless Systems
  • Delivers Internet services into homes and
    businesses
  • Designed to bypass the local loop telephone line,
    in a metropolitan area
  • Transmits voice, data, and video over high
    frequency radio signals
  • Past and future trends

(to p57)
(to p58)
57
Broadband Wireless Systems (continued)
(to p56)
58
Broadband Wireless Systems (continued)
  • Multichannel multipoint distribution service
    (MMDS) and local multipoint distribution service
    (LMDS) looked promising a few years ago but died
    off
  • Now companies are eyeing Wi-Max, an IEEE 802.16
    standard initially 300 kbps to 2 Mbps over a
    range of as much as 30 miles forthcoming
    standard (802.16e) will allow for moving devices

(to p30)
59
Bluetooth
  • Bluetooth is a specification for short-range,
    point-to-point or point-to-multipoint voice and
    data transfer
  • Bluetooth can transmit through solid, non-metal
    objects
  • Its typical link range is from 10 cm to 10 m, but
    can be extended to 100 m by increasing the power
  • Bluetooth will enable users to connect to a wide
    range of computing and telecommunication devices
    without the need of connecting cables
  • Typical uses include phones, pagers, modems, LAN
    access devices, headsets, notebooks, desktop
    computers, and PDAs

(to p30)
60
Wireless Local Area Networks (IEEE 802.11)
  • This technology transmits data between
    workstations and local area networks using
    high-speed radio frequencies
  • Current technologies allow up to 54 Mbps
    (theoretical) data transfer at distances up to
    hundreds of feet
  • Three popular standards IEEE 802.11b, a, g
  • More on this in Chapter Seven (LANs)

(to p30)
61
Free Space Optics and Ultra-Wideband
  • Free space optics
  • Uses lasers, or more economically, infrared
    transmitting devices
  • Line of sight between buildings
  • Typically short distances, such as across the
    street
  • Newer auto-tracking systems keep lasers aligned
    when buildings shake from wind and traffic
  • Current speeds go from T-3 (45 Mbps) to OC-48
    (2.5 Gbps) with faster systems in development
  • Major weakness is transmission thru fog
  • A typical FSO has a link margin of about 20 dB
  • Under perfect conditions, air reduces a systems
    power by approximately 1 dB/km
  • Scintillation is also a problem (especially in
    hot weather)

(to p62)
62
Free Space Optics and Ultra-Wideband (continued)
  • Ultra-wideband
  • UWB not limited to a fixed bandwidth but
    broadcasts over a wide range of frequencies
    simultaneously
  • Many of these frequencies are used by other
    sources, but UWB uses such low power that it
    should not interfere with these other sources
  • Can achieve speeds up to 100 Mbps but for small
    distances such as wireless LANs
  • Proponents for UWB say it gets something for
    nothing, since it shares frequencies with other
    sources. Opponents disagree
  • Cell phone industry against UWB because CDMA most
    susceptible to interference of UWB
  • GPS may also be affected
  • One solution may be to have two types of systems
    one for indoors (stronger) and one for outdoors
    (1/10 the power)

(to p30)
63
Wireless Media (continued)
more
(to p64)
64
Wireless Media (continued)
(to p28)
65
Media Selection Criteria
  • Cost
  • Speed
  • Distance and expandability
  • Environment
  • Security

(to p66)
(to p67)
(to p68)
(to p69)
(to p70)
(to p2)
66
Cost
  • Different types of costs
  • Initial cost what does a particular type of
    medium cost to purchase? To install?
  • Maintenance / support cost
  • ROI (return on investment) if one medium is
    cheaper to purchase and install but is not cost
    effective, where are the savings?

(to p65)
67
Speed
  • Two different forms of speed
  • Propagation speed the time to send the first
    bit across the medium
  • This speed depends upon the medium
  • Airwaves and fiber are speed of light
  • Copper wire is two thirds the speed of light
  • Data transfer speed the time to transmit the
    rest of the bits in the message
  • This speed is measured in bits per second

(to p65)
68
Expandability and Distance
  • Certain media lend themselves more easily to
    expansion
  • Dont forget right-of-way issue

(to p65)
69
Environment
  • Many types of environments are hazardous to
    certain media

(to p65)
70
Security
  • If data must be secure during transmission, it is
    important that the medium not be easy to tap

(to p65)
71
Conducted Media in Action Example 1
  • First example simple local area network
  • Hub typically used
  • To select proper medium, consider
  • Cable distance
  • Data rate
  • Layout

(to p72)
72
Conducted Media in Action Example 1
(to p3)
73
Conducted Media in Action Example 2
  • Second example company wishes to transmit data
    between buildings that are one mile apart
  • Is property between buildings owned by company?
  • If not consider using wireless
  • When making decision, need to consider
  • Cost
  • Speed
  • Expandability and distance
  • Environment
  • Security

(to p3)
74
Wireless Media In Action Example 1
  • First example you wish to connect two computers
    in your home to Internet, and want both computers
    to share a printer
  • Can purchase wireless network interface cards
  • May consider using Bluetooth devices

(to p3)
75
Example 2
  • Second example company wants to transmit data
    between two locations, such as Beijing and
    Shanghai
  • Company considering two-way data communications
    service offered through VSAT satellite system
  • Layout

(to p76)
(to p3)
76
Wireless Media In Action Three Examples
(continued)
(to p3)
77
Wireless Media In Action Example 3
  • Third example second company wishes to transmit
    data between offices two miles apart
  • Considering terrestrial microwave system
  • Layout

(to p78)
78
Wireless Media In Action Three Examples
(continued)
(to p3)
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Conducted and Wireless Media

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Transcript and Presenter's Notes

Title: Conducted and Wireless Media


1
Lecture 03
  • Conducted and Wireless Media

2
Introduction
  • Communications are conducted through a medium,
  • For example, we talked, our voice transmitted
    through air
  • Thus, the world of computer networks would not
    exist if there were no medium by which to
    transfer data
  • The two major categories of media include
  • Conducted media
  • Wireless media
  • How to subscribe them for organizations?
  • Selection criteria

(to p4)
(to p28)
(to p65)
(to p3)
Application examples
3
Application examples
  • Conducted
  • Example 1
  • Example 2
  • Wireless
  • Example 1
  • Example 2
  • Example 3

(to p71)
(to p73)
(to p74)
(to p75)
(to p77)
4
Conducted media
  • Physical connection between source and sink
    points
  • Three common media
  • i) wire
  • ii) coaxial cable
  • iii) optical fiber
  • Comparison between their transmission speeds

(to p5)
(to p10)
(to p13)
(to p27)
(to p2)
5
i) wire
  • usually made of copper with a pair of wire
  • Or called twisted pair of wire
  • the pairs of wires are almost insulated with
    plastic coating and twisted together -- known as
    twisted pair wires
  • (see Figure 9-6)
  • Categorizations
  • the twisting has the effect of electrically
    canceling the signals radiating form each wire
    ---- prevents the signals on one pair of wires
    from interfering the adjacent pair
  • the effect is known as crosswalk

(to p6)
(to p9)
(to p4)
6
FIGURE 9-6 Twisted pair wires are the most
commonly used medium for communications
transmission.
(to p5)
  • As to oppose different layout as shown in Figure
    3.2
  • Different ways of twisted pair way adopted in
    industries

(to p7)
(to p5)
(to p8)
7
(to p6)
8
(to p6)
9
(to p5)
10
ii) coaxial cable
  • Cable that made of several layers of material
    around a central core, which often a copper wire
  • (see Figure 9-8)
  • has a very wide bandwidth (400 Mhz to 600 Hhz),
    thus carries a very high data capacity
  • one coaxial cable carries up to 10,800 voice
    conversations or over 50 television channles
  • Its max capacity is dependent on the thickness of
    the copper wire
  • Two main applications

(to p12)
(to p11)
11
ii) coaxial cable (cont.)
  • It has two main applications
  • 1) Baseband coaxial technology uses digital
    signaling in which the cable carries only one
    channel of digital data
  • 2) Broadband coaxial technology transmits analog
    signals and is capable of supporting multiple
    channels
  • Disadv it is easy to tape and thus lack of a
    high security measure

(to p4)
12
FIGURE 9-8 Parts of a coaxial cable.
(to p10)
13
iii) optical fiber
  • Is a new media for comm
  • is a very thin glass fiber which core provides
    the transmission capability
  • the core is surrounded by another type of glass
    called cladding, which protected by a plastic
    coating
  • (see Figure 9-9) (to p14)
  • data is placed on with a light source or a laser.
    Light source stays in the core as the cladding
    has a low refractive index

(to p17)
14
FIGURE 9-9 Parts of optical fiber cable.
(to p13)
(to p15)
Alternative view
15
(to p16)
Thin vs. Thick fiber optic cable
(to p13)
16
Fiber-Optic Cable (continued)
  • Fiber-optic cable is capable of supporting
    millions of bits per second for 1000s of meters
  • Thick cable (62.5/125 microns) causes more ray
    collisions, so you have to transmit slower. This
    is step index multimode fiber. Typically use LED
    for light source, shorter distance transmissions
  • Thin cable (8.3/125 microns) very little
    reflection, fast transmission, typically uses a
    laser, longer transmission distances known as
    single mode fiber

(to p15)
17
iii) optical fiber (cont.)
  • Two primary types of fiber
  • a) single mode
  • b) multi mode
  • How more lights can be traveled together
  • Layout of optical fiber worldwide
  • Fiber optic cable is difficult to splice -
    requires a reflectometer to detect such work
  • SONET concept
  • Adv
  • Disv

(to p18)
(to p19)
(to p20)
(to p22)
(to p24)
(to p25)
(to p4)
18
(to p17)
19
Wavelength division
  • Wavelength division multiplexing
  • A technique which allows many light beams of
    different wavelengths can travel along a single
    fiber simultaneously without interfering with one
    another

(to p17)
20
FIGURE 9-10a The worlds undersea cable
network.
(to p21)
21
FIGURE 9-10b Continued
(to p17)
22
SONET
  • Synchronous Optical Network
  • A technique facilitates easy to connect carriers
    that using different brands/products of their
    optical networks
  • It is a standard for the ANSI (American National
    Standard Institute)
  • Transmission rate at Gpbs
  • Data speed for different networks

(to p23)
(to p17)
23
FIGURE 9-11 Comparative data rates for the
SONET and ITU-T optical fiber transmission
standards.
(to p22)
24
iii) optical fiber (cont.)
  • Advantages
  • 1) do not radiate signal as all electrical
    devices do
  • 2) fiber is of light weight
  • 3) cost of fibers is getting cheaper
  • 4) high bandwidth - high data capability
  • 5) little lost of signal strength
  • 6) excellent isolation between parallel fiber -
    crossed-talk between fiber does not exist
  • 7) very secure, difficult to tape

(to p17)
25
Disv
  • Because fiber-optic cable is susceptible to
    reflection (where the light source bounces around
    inside the cable) and refraction (where the light
    source passes out of the core and into the
    surrounding cladding), thus Fiber-optic cable is
    not perfect either. Noise is still a potential
    problem

(to p26)
Concepts of refraction and reflection
(to p17)
26
Fiber-Optic Cable (continued)
(to p25)
27
Conducted Media
(to p4)
28
Wireless media
  • Technically speaking in wireless transmissions,
    space is the medium
  • Radio, satellite transmissions, and infrared
    light are all different forms of electromagnetic
    waves that are used to transmit data
  • Their frequencies of transmission
  • Different types of applications
  • Comparisons

(to p29)
(to p30)
(to p63)
(to p2)
29
Wireless Media (continued)
(to p28)
30
Applications
  • i) microwave radio
  • ii) satellite
  • iii) cellular phones
  • Iv) Infrared Transmissions
  • v) Wireless Application Protocol (WAP)
  • Broadband Wireless Systems
  • Bluetooth
  • Wireless Local Area Networks
  • Free Space Optics and Ultra-Wideband

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31
iv) microwave radio
  • Is a medium most common carriers for long
    distance comm (how it looks like )
  • transmit in the range of 4-28 Ghz freq range
  • up to 6000 voice circuits are carried in a 30 Mhz
    wide radio channel
  • travel in a straight line - ie must transmit and
    receive in a direct line of sight , and signals
    will not pass through solid objects
  • requirement

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Terrestrial Microwave Transmission (continued)
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Terrestrial Microwave Transmission (continued)
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iv) microwave radio (cont.)
  • requires to set up an antenna in the range of 20
    to 30 miles
  • Capable to carry either analog and digital form
  • Disadv
  • may interfere by the weather condition (why?)

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35
v) satellite
  • Use of microwave radio, the signal travels from a
    ground station on earth to a satellite and back
    to another ground station
  • Satellites can be classified by how far out into
    orbit each one is (LEO, MEO, GEO, and HEO)
  • radio signal is beamed to the satellite on a
    specific frequency called uplink where
    rebroadcast on a different frequency called
    downlink

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36
Satellite Microwave Transmission (continued)
  • LEO (Low-Earth-Orbit) 100 to 1000 miles out
  • Used for wireless e-mail, special mobile
    telephones, pagers, spying, videoconferencing
  • MEO (Middle-Earth-Orbit) 1000 to 22,300 miles
  • Used for GPS (global positioning systems) and
    government
  • GEO (Geosynchronous-Earth-Orbit) 22,300 miles
  • Always over the same position on earth (and
    always over the equator)
  • Used for weather, television, government
    operations
  • HEO (Highly Elliptical Earth orbit) satellite
    follows an elliptical orbit
  • Used by the military for spying and by scientific
    organizations for photographing celestial bodies

Their positions on the orbit
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Satellite Microwave Transmission (continued)
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Satellite Transmission (continued)
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v) satellite (cont.)
  • Due to the security reason, information that
    being sent is first encrypted so that tapping and
    interpret its content is difficult
  • there exists a delay of receiving information ---
    called propagation delay, is called as
  • distance apart of comm device
  • ------------------------------------
    -----
  • speed in which data is transmitted
  • example

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40
v) satellite (cont.)
  • If satellite is 22,300 mile from the ground and
    speed sending data is 186,000 miles per second,
    then
  • 2 x 22,300
  • Propagation delay ----------------
  • 18,6000
  • 0.2398 sec
  • Classifications by their configuration

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41
Satellite (continued)
  • Satellite microwave can also be classified by its
    configuration
  • Bulk carrier configuration
  • Multiplexed configuration
  • Single-user earth station configuration (e.g.
    VSAT)

Their semantic view
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42
Satellite Microwave Transmission (continued)
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43
Cellular Telephones
  • Wireless telephone service, also called mobile
    telephone, cell phone, and PCS
  • To support multiple users in a metropolitan area
    (market), the market is broken into cells
  • Each cell has its own transmission tower and set
    of assignable channels
  • Different generations of MP

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44
Cellular Telephones (continued)
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45
Cellular Telephones (continued)
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46
Cellular Phones
  • 1st generation
  • 2nd generation
  • 2.5 generation
  • 3rd generation

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47
Cellular Telephones (continued)
  • 1st Generation
  • AMPS (Advanced Mobile Phone Service) first
    popular cell phone service used analog signals
    and dynamically assigned channels
  • D-AMPS (Digital AMPS) applied digital
    multiplexing techniques on top of AMPS analog
    channels

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48
Cellular Telephones (continued)
  • 2nd Generation
  • PCS (Personal Communication Systems)
    essentially all-digital cell phone service
  • PCS phones came in three technologies
  • TDMA Time Division Multiple Access
  • CDMA Code Division Multiple Access
  • GSM Global System for Mobile Communications

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Cellular Telephones (continued)
  • 2.5 Generation
  • ATT Wireless, Cingular Wireless, and T-Mobile
    now using GPRS (General Packet Radio Service) in
    their GSM networks (can transmit data at 30 kbps
    to 40 kbps)
  • Verizon Wireless, Alltel, U.S.Cellular, and
    Sprint PCS are using CDMA2000 1xRTT (one carrier
    radio- transmission technology) (50 kbps to 75
    kbps)
  • Nextel uses IDEN technology

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50
Cellular Telephones (continued)
  • 3rd Generation
  • UMTS (Universal Mobile Telecommunications System)
    also called Wideband CDMA
  • The 3G version of GPRS
  • UMTS not backward compatible with GSM (thus
    requires phones with multiple decoders)
  • 1XEV (1 x Enhanced Version) 3G replacement for
    1xRTT
  • Will come in two forms
  • 1xEV-DO for data only
  • 1xEV-DV for data and voice

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51
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52
Infrared Transmissions
  • Transmissions that use a focused ray of light in
    the infrared frequency range
  • Very common with remote control devices, but can
    also be used for device-to-device transfers, such
    as PDA to computer

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53
Wireless Application Protocol (WAP)
  • WAP is a set of protocols that allows wireless
    devices such as cell phones, PDAs, and two-way
    radios to access the Internet
  • WAP is designed to work with small screens and
    with limited interactive controls
  • WAP incorporates Wireless Markup Language (WML)
    which is used to specify the format and
    presentation of text on the screen
  • Their applications

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Wireless Application Protocol (WAP) (continued)
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55
Wireless Application Protocol (WAP) (continued)
  • WAP may be used for applications such as
  • Travel directions
  • Sports scores
  • E-mail
  • Online address books
  • Traffic alerts
  • Banking and news
  • Possible short-comings include low speeds,
    security, and very small user interface

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Broadband Wireless Systems
  • Delivers Internet services into homes and
    businesses
  • Designed to bypass the local loop telephone line,
    in a metropolitan area
  • Transmits voice, data, and video over high
    frequency radio signals
  • Past and future trends

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57
Broadband Wireless Systems (continued)
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58
Broadband Wireless Systems (continued)
  • Multichannel multipoint distribution service
    (MMDS) and local multipoint distribution service
    (LMDS) looked promising a few years ago but died
    off
  • Now companies are eyeing Wi-Max, an IEEE 802.16
    standard initially 300 kbps to 2 Mbps over a
    range of as much as 30 miles forthcoming
    standard (802.16e) will allow for moving devices

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59
Bluetooth
  • Bluetooth is a specification for short-range,
    point-to-point or point-to-multipoint voice and
    data transfer
  • Bluetooth can transmit through solid, non-metal
    objects
  • Its typical link range is from 10 cm to 10 m, but
    can be extended to 100 m by increasing the power
  • Bluetooth will enable users to connect to a wide
    range of computing and telecommunication devices
    without the need of connecting cables
  • Typical uses include phones, pagers, modems, LAN
    access devices, headsets, notebooks, desktop
    computers, and PDAs

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60
Wireless Local Area Networks (IEEE 802.11)
  • This technology transmits data between
    workstations and local area networks using
    high-speed radio frequencies
  • Current technologies allow up to 54 Mbps
    (theoretical) data transfer at distances up to
    hundreds of feet
  • Three popular standards IEEE 802.11b, a, g
  • More on this in Chapter Seven (LANs)

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61
Free Space Optics and Ultra-Wideband
  • Free space optics
  • Uses lasers, or more economically, infrared
    transmitting devices
  • Line of sight between buildings
  • Typically short distances, such as across the
    street
  • Newer auto-tracking systems keep lasers aligned
    when buildings shake from wind and traffic
  • Current speeds go from T-3 (45 Mbps) to OC-48
    (2.5 Gbps) with faster systems in development
  • Major weakness is transmission thru fog
  • A typical FSO has a link margin of about 20 dB
  • Under perfect conditions, air reduces a systems
    power by approximately 1 dB/km
  • Scintillation is also a problem (especially in
    hot weather)

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62
Free Space Optics and Ultra-Wideband (continued)
  • Ultra-wideband
  • UWB not limited to a fixed bandwidth but
    broadcasts over a wide range of frequencies
    simultaneously
  • Many of these frequencies are used by other
    sources, but UWB uses such low power that it
    should not interfere with these other sources
  • Can achieve speeds up to 100 Mbps but for small
    distances such as wireless LANs
  • Proponents for UWB say it gets something for
    nothing, since it shares frequencies with other
    sources. Opponents disagree
  • Cell phone industry against UWB because CDMA most
    susceptible to interference of UWB
  • GPS may also be affected
  • One solution may be to have two types of systems
    one for indoors (stronger) and one for outdoors
    (1/10 the power)

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63
Wireless Media (continued)
more
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64
Wireless Media (continued)
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65
Media Selection Criteria
  • Cost
  • Speed
  • Distance and expandability
  • Environment
  • Security

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66
Cost
  • Different types of costs
  • Initial cost what does a particular type of
    medium cost to purchase? To install?
  • Maintenance / support cost
  • ROI (return on investment) if one medium is
    cheaper to purchase and install but is not cost
    effective, where are the savings?

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67
Speed
  • Two different forms of speed
  • Propagation speed the time to send the first
    bit across the medium
  • This speed depends upon the medium
  • Airwaves and fiber are speed of light
  • Copper wire is two thirds the speed of light
  • Data transfer speed the time to transmit the
    rest of the bits in the message
  • This speed is measured in bits per second

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68
Expandability and Distance
  • Certain media lend themselves more easily to
    expansion
  • Dont forget right-of-way issue

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69
Environment
  • Many types of environments are hazardous to
    certain media

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70
Security
  • If data must be secure during transmission, it is
    important that the medium not be easy to tap

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Conducted Media in Action Example 1
  • First example simple local area network
  • Hub typically used
  • To select proper medium, consider
  • Cable distance
  • Data rate
  • Layout

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Conducted Media in Action Example 1
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73
Conducted Media in Action Example 2
  • Second example company wishes to transmit data
    between buildings that are one mile apart
  • Is property between buildings owned by company?
  • If not consider using wireless
  • When making decision, need to consider
  • Cost
  • Speed
  • Expandability and distance
  • Environment
  • Security

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74
Wireless Media In Action Example 1
  • First example you wish to connect two computers
    in your home to Internet, and want both computers
    to share a printer
  • Can purchase wireless network interface cards
  • May consider using Bluetooth devices

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75
Example 2
  • Second example company wants to transmit data
    between two locations, such as Beijing and
    Shanghai
  • Company considering two-way data communications
    service offered through VSAT satellite system
  • Layout

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76
Wireless Media In Action Three Examples
(continued)
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77
Wireless Media In Action Example 3
  • Third example second company wishes to transmit
    data between offices two miles apart
  • Considering terrestrial microwave system
  • Layout

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78
Wireless Media In Action Three Examples
(continued)
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