Introduction to Wireless: Voice and Data

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Introduction to Wireless Voice and Data

• CS480 Computer Science Seminar
• Fall, 2002

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Wireless Communication

• Communication without wires invisible
  electromagnetic waves are used to transmit
  information (voice or data).

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Brief History of Wireless technology

• 1876 Alexander Graham Bell demonstrated the
  telephone (wired).
• 1880 Bell used reflected sunlight and
  photoelectric selenium detector (receiver) to
  transmit without wire intelligible speech over
  700 feet.
• Heinrich Rudolf Hertz demonstrated the existence
  of electromagnetic waves in the mid 19th century.
• 1886 Guglielmo Marconi received a patent for the
  first practical wireless telegraph.
• 1890 Reginald Fessenden developed wireless voice
  communication.
• 1920 the first commercial radio station KDKA was
  established in Pittsburg, PA.

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Brief History of Wireless technology continued

• 1921first terrestrial mobile application, a
  one-way system was used at the Detroit Police
  Department.
• 1926 John Logie Baier demonstrated B/W
  television.
• 1927 color TV publicly demonstrated.
• Over the last decade, wireless industry has
  experienced exponential growth with cellular
  voice telephony accounts for the vast majority of
  the market. A plethora of new technologies have
  emerged, including Truck Mobile Radio (TMR),
  paging, cordless telephony, Wireless Office
  Communication Systems (WOTS), celluar, wireless
  LANs, Wireless Local Loop (WLL), Low Earth
  Orbiting Satellites (LEOs), Personal
  Communication Services (PCS), Personal Digital
  Assistants (PDAs). Within each technology, there
  exist a number of specific technologies for
  discussion.

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Standard Organizations

• FCC, IEEE (US)
• CEPT/ETSI (Europe)
• ITU-R (international-radio communication sector).
• etc.
• Functions include frequency allocation (spectrum
  management) and power level regulation to avoid
  interference.

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Advantages and disadvantages of wireless

• Advantages
• Reduced cost of installation
• reconfiguration, improved speed of deployment and
  reconfiguration
• Mobile
• Disadvantages
• Spectrum availability (radio operates between 3k
  to 30G Hz
• Multipath interference (MPI) leads to ghosting
  effect

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The cell concept frequency reuse

• Concepts date back in 1947 at Bell labs.
• Assuming 12 channels are available in a
  metropolitan area of 60 miles radius.
• 1 macrocell supports 12 simultaneous
  conversations
• Divide a macrocell into 7 microcells, a reuse
  factor of 128 is realized, allowing 1,536
  conversations.
• Divide a macrocell into 7 picocells, the system
  supports in theory 6, 168 conversations.

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Digital versus analog

• Advantages of digital
• More efficient use of bandwidth thru compression.
• Improved quality of transmission
• Improved security thru encryption
• Improved throughput (due to diminished error)
• Analog still in existence due to
• Incumbent technology
• Expensive and disruptive to completely rip it out

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Multiplexing and access techniques FDMA

• Frequency division multiple access (FDMA)
  divides a frequency range (channel) into multiple
  carriers (sub channels) to support multiple
  conversations guard bands are often required.
• Analog cellular systems use FDMA exclusively,
  e.g., U.S. AMPS (Advanced Mobile Phone System)
  40 MHz total allotted bandwidth is divided into
  666 frequency pairs, each pairs has a bandwidth
  of 60 kHz (30 for forward channel, another 30 kHz
  for reverse channel).

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Multiplexing and access techniques TDMA

• Time division multiple access (TDMA) a digital
  technique that divides each channel into fixed
  number of time slots each of which supports a
  conversation (similar to T-carriers).
• In GSM (Global System for Mobile Communication),
  a channel of 200 kHz has a data rate of approx.
  200 kbps, which is divided into 8 time slots of
  25 kbps, easily supports a low-bit-rate digitized
  voice of 9.6 kbps. Each conversation uses two
  time slots, one for the forward channel and one
  for the reverse channel.

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Multiplexing and access techniquesCDMA

• Code division multiple access (CDMA) is based on
  spread spectrum radio technology patented by
  Heddy Lamar in 1942. In spread spectrum radio, a
  narrow band signal is spread and sent over a much
  wider spectrum of radio frequencies. It may use
  either direct sequence (DS) or frequency hopping
  (FH) techniques.
• Frequency hopping spread spectrum (FHSS) is
  generally preferred today it involves the
  transmission of short burst of packets over a
  range of frequency channels within the wideband
  carrier, with the transmitter and receiver
  hopping from one frequency to another in a
  carefully choreographed hop sequence, which is
  generally under the control of the centralized
  base station antenna.
• CDMA improves BW utilization (201 theoretically,
  around 41 in practice) because many users can
  share the same wideband radio channel.

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CDMA continued

• Qualcomm develops, manufactures, markets, and
  licenses CDMA products. A great number of
  manufacturers and providers of cellular, PCS,
  wireless LANs and other systems and networks have
  licensed CDMA.

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Switched mobile radio (SMR)

• 1921 Detroit Police Department first 2-way mobile
  radio system (AM technology).
• Early 1930s Bayonne, NJ Police followed suit
  (still AM)
• Late 1930s, FM technology replaced the AM.
• 1949, FCC began to allocate spectrum and regulate
  it use.
• 1946 ATT launched commercial application in St.
  Louis. In addition to a 50-mile range centralized
  antenna, the system was connected to PSTN.
• 1960s SMR, also known as TMR (Trunk Mobile
  Radio), marketed as improved mobile telephone
  service.
• SMR/TMR has been largely supplanted by cellular
  service.

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Paging

• Introduced in the 1950s in New York.
• Standards
• 1981 international POCSAG (Post Office Code
  Standardization Advisory Group) can support 2
  millions individual addresses, tone-only,
  numeric, and alphanumeric pagers are supported on
  a one-way basis.
• ERMES (European Radio Message System) 1990, 16
  European countries endorsed it.
• Motorola recently developed FLEX with the hope
  that it will be accepted as the new international
  standard. It supports
• 5 billion addresses
• FLEX 1600 bps, 25 kHz channel, one-way
• ReFLEX 1600, 3200, 6400, and 9600 bps, 25 or 50
  kHz channels downstream and 12.5 kHz upstream,
  two-way.
• InFLEX up to 112 kbps, 50 kHz channels in the
  narrowband PCS range two-way, supported
  compressed voice downstream

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Paging equipment and applications contemporary
and developing

• Opportunities for innovators to come up with new
  applications.

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Cordless telephone and wireless office
telecommunication systems (WOTS)
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Cellular Radio

• Concepts date back in 1947 at Bell labs to meet
  the increasing demand of SMR/TMR radio systems.
• Highly scalable cell size can be flexibly
  changed.
• Cell diameter usually ranges from 1 to 5 miles,
  depending on topography.
• Can switch from one cell to another thru
  hand-off, which is handled by MTSO (mobile
  traffic switching office). MTSOs are
  interconnected and are connected to PTSN.
• Soft hand-off (make and break) or hard hand-off
  (bread and make) both are fine with voice
  communication, but the latter has problem with
  data communication.

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Cellular standards

• Analog cellular G1 cellular systems
• AMPS ATT and Motorola rapidly giving way to
  digital technology worldwide.
• N-AMPS narrow-band AMPS Motorola.
• NMT (Nordic mobile telephone) in scandinavia
• TACS (Total access communication system)
  developed in England.

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Cellular standards continued

• Digital cellular G2 cellular systems
• GSM (Global System for Mobile communication)
  dominates worldwide adopted in 1987 for
  pan-Europe systems operates in the 800 and 900
  MHz ranges and is ISDN compatible 4-cell reuse
  plan and each cell is divided into 12 sectors
  used CDMA supporting roaming from country to
  country.
• D-AMPS (Digital AMPS) AKA US TDMA is the N. Am.
  Standard operates in the same 800 MHz band as
  AMPS and uses the same 30 kHz bands as AMPS
  31improvement on band utilization over AMPS
  co-exists with AMPS data rate up to 28.8 bps.
• Others PDC (Japanese Digital Cellular), PCS
  (Personal digital system).

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The future of cellular radio G3?

• Market increases quickly over the years
  worldwide, often beyond projection.
• Cost continues to drop .45/minute in the early
  90s to 9.4 cents in 2000.
• G3 proposals are under consideration
• Calls for data rate from 144 kbps (fast moving)
  to 384 kbps (pedestrian).
• Supports global roaming

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Wireless data networks packet radio

• Operating at various data rates (4.8 - 19.6 kbps
  77 kbps) and and bands (e.g., 800-900 MHz,
  902-928 MHz, 2.3 and 2.4 GHz) from different
  companies (BellSouth, Ardis, Metricom, etc.)
  data-specific wireless networks have been
  deployed all over the metropolitan areas in the
  US over the last few years.
• Properiety packet protocols are used.

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Wireless LANs or WLANs

• Based largely on spread-sprectrum technology.
• Operate in IR, radio range (e.g., 2.4-2.4834
  GHz).
• Raw bandwidth 4 MHz with effective throughput
  around 2 Mbps per hub. Infrared-based bridges run
  at speed up to 622 Mbps.
• Standards were finalized in 1997 by IEEE (802-11)
• Moderate success over the last few years.

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Wireless local loop (WLL)

• Local loops were owned by ILECs (incumbent local
  exchange carriers). The Telecommunication Act of
  1996 opened the local loops for competition.
• Options
• twisted pair (old and slow) not the way to go
• fiber optimum choice, but too expensive now for
  low capacity application (needs killer
  applications).
• So, Wireless local loops is a good choice. But it
  radio frequency and other electromagnetc
  inteference can be a problem.

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Low-earth orbiting satellites (LEOs)
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