Conducted and Wireless Media

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Conducted and Wireless Media

• Chapter 3

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Learning Objectives

• Identify and describe the characteristics,
  advantages, disadvantages, and applications of
  guided or conducted media
• Identify and describe the characteristics,
  advantages, disadvantages, and applications of
  radiated or wireless media
• Identify media selection criteria

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Communications Media

• Guided (physical or conducted)
• Twisted-Pair
• Coaxial cable
• Fiber optic cable

• Radiated (or wireless)
• Terrestrial microwave
• Satellite microwave
• Cellular telephone systems
• Infrared transmission
• Broadband wireless distribution services
• Bluetooth
• Wireless LAN systems
• Zig-bee short-range transmissions

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Twisted Pair wire

• Two or more pairs of single conductor copper
  wires that have been twisted around each other.
• Oldest, simplest, most common
• Types include category 1-5, 5e, 6-7
• Unshielded twister pair (UTP) shielded twisted
  pair (STP)

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Twisted Pair Wire (continued)
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Coaxial cable

• A single wire wrapped in a foam insulation
  surrounded by a braided metal shield, then
  covered in a plastic jacket. Cable can be thick
  or thin.
• Baseband coaxial technology
• Broadband coaxial technology

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Chapter 5 Communications Media, Servers, and
Clients 7
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Fiber optic cable

• A thin glass cable approximately a little thicker
  than a human hair surrounded by a plastic coating
  and packaged into an insulated cable.
• A photo diode or laser generates pulses of light
  which travel down the fiber optic cable and are
  received by a photo receptor.

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Chapter 5 Communications Media, Servers, and
Clients 9
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Wireless media

• Radio, satellite transmissions, and infrared
  light are all different forms of electromagnetic
  waves that are used to transmit data.
• Each source occupies a different set of
  frequencies.
• FCC assigns frequencies for each application
  occasionally auctions unused frequencies.

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Wireless Media (continued)
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Terrestrial Microwave

• Land-based, line-of-sight transmission
• Approximately 15-30 miles maximum between towers
• Transmits data at hundreds of millions of bits
  per second
• Popular with telephone companies and business to
  business transmissions

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Satellite Microwave

• Similar to terrestrial microwave except 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).

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Satellites

• LEO - Low Earth Orbit
• MEO - Middle Earth Orbit
• GEO - Geosynchronous Orbit
• HEO Highly Elliptical Orbit

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Cellular Telephone

• Wireless telephone service, such as cellular
  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.

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Infrared

• Special 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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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

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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 shortcomings 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.
• Transmits voice, data and video over high
  frequency radio signals.

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Bluetooth

• Bluetooth is a Radio Frequency specification for
  short-range, 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 and pagers, modems,
  LAN access devices, headsets, notebooks, desktop
  computers, and PDAs.

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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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Media selection criteria

• Cost
• Initial cost, ROI, maintenance/support cost
• Speed
• Data transfer speed, propagation speed
• Distance and expandability
• Environment
• Security
• Wiretap possible? Need encryption?