Bluetooth, IEEE 802.11

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Bluetooth, IEEE 802.11 Cell Phone Systems

• --Arun Radhakrishnan
• --Thierry Fernaine
• --Vipul Gautam

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Overview

• What is Bluetooth? -- Vipul
• Specifications and Protocols
• What is 802.11? -- Arun
• Specifications and Protocols
• 802.11 vs. Bluetooth
• Cellular Phone Systems -- Thierry
• CDMA
• TDMA
• FDMA
• Generations of cell phones (1G to 4G)
• Experiments/Demonstrations
• Summary and Future Plans

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Schedule

• Brainstorming the tasks involved in the project
• 15th February, 2003
• Information on Bluetooth and 802.11
• 25th February, 2003
• Analyzing Bluetooth vs 802.11
• 28th April, 2003
• Obtaining materials on phone systems (CDMA, TDMA,
  FDMA)
• 23rd April, 2003
• Information about 3G and 4G
• 17th April, 2003
• Talking to a professor about doing an experiment
  on wireless
• 10th March, 2003
• Observing the experiment performed by a TA
• 2nd April, 2003

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Bluetooth

• Protocol for the efficient transmission of data
• Designed for devices such as cell phones,
  printers, PDAs, notebook computers, fax machines

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Bluetooth

• Low power link
• Short time data transfers
• Small indoor distances
• Line of Sight is not required
• Better than IR link

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Bluetooth Specification Protocol Stack
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Bluetooth

• Operates in the 2.4GHz band
• Unlicensed band
• Uses frequency hopping
• 2.4 to 2.4385 GHz
• 79 hopping frequencies separated by 1 MHz
• Data rate ? 1Mbps

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Frequency Hopping
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Frequency Hopping

• Characterized by its system of fast frequency
  hops
• 10 different types of hopping sequences are
  defined
• 5 of the 79 MHz range/79 hop system and 5 for
  the 23 MHz range/23 hop system.
• The different range system's hopping sequences
  differ in frequency range 79MHz / 23MHz, and
  segment length 32 hops(79MHz system) / 16
  hops(23MHz system).

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Frequency Hopping

• Assurance of high quality communication in large
  urban centers and high-capacity networks
• The millisecond rhythm with which the change of
  frequency takes place enables interference to be
  eliminated and prevent fading effects.
• Deployed primarily in the military sector as well
  as in diplomatic communications via radio due to
  its unique bug-proof characteristics.

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Data Layer

• Piconets are a collection of devices connected
  via BT technology in an ad hoc fashion.
• Each may have as many as 8 connected devices.
• One unit acts as the master and the others as
  slaves.
• Devices create many overlapping networks called
  Scatternets.
• Formed by multiple independent and
  non-synchronized piconets.

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Data Layer

• Master device-
• Initiates an action or requests a service.
• Clock and hopping sequences are used to
  synchronize all other devices in the piconet.

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What is 802.11

• Wireless standards that specify an interface
  between a wireless client and a central point of
  access and among wireless clients.
• The IEEE 802.11 specifications tailored to
  resolve compatibility issues between
  manufacturers of wireless LAN equipment.
• The original IEEE 802.11 specifications defined
  data rates of 1 Mbps and 2 Mbps via radio waves
• The IEEE 802.11 specifications continue to expand
  and new standards are being considered and
  ratified. The most commonly used wireless
  standard is IEEE 802.11b.

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802.11 Network
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802.11 a-g

• 802.11a
• designed to operate in the 5 GHz band.
• Achieves data transmission rates of 54Mbps.
• Not readily accepted overseas.
• 802.11b
• "High Rate" standard, also known as Wi-Fi (for
  "wireless fidelity)
• The family of IEEE 802.11b specifications allows
  for a wireless data transmission
• rate of 11 Mbps as an unlicensed use of the
  2.4-GHz radio frequency band.
• 802.11g
• The latest wireless networking specification from
  IEEE
• based on 802.11b.
• will broaden 802.11b's data rates to 54 Mbps
  within the 2.4 GHz band using OFDM (Orthogonal
  Frequency Division Multiplexing) technology.
• IEEE 802.11g is backward compatible with IEEE
  802.11b.

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802.11 protocols contd..

• Task Group "C"
• improving the MAC layer to improve bridging
• Task Group "D"
• modifying the Physical layer to meet regulatory
  requirements around the globe.
• Task Group "E"
• enhance the MAC layer to improve quality of
  service (QoS) for time-sensitive applications
  like real-time voice and video.
• Task Group "F"
• improve interoperability of access points from
  different vendors in a distribution system.
• Task Group "H"
• channel selection and transmit power issues to
  ensure that 802.11a is usable in Europe, similar
  to what "D" is doing for 802.11b.
• Some European countries currently do not allow
  802.11a, favoring the European HiperLAN2 5 GHz
  wireless LAN standard instead.
• Task Group "I"
• recently spun-off from Task Group "E" to put more
  emphasis on improving the security and
  authentication mechanisms.

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Motivation for 802.11

• Increased flexibility A conference with an
  ad-hoc network can be set up and dismantled in a
  short time.
• Increased mobility Users can move around without
  restrictions and access LANs from anywhere.
• More economical In old buildings it is more
  economical to put up some wireless stations than
  to break up walls. In factories, putting wires
  may not be feasible.

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What is spread spectrum radio technology?

• Increase reliability
• Boost throughput
• Allow many unrelated products (e.g., microwave
  ovens) to share the spectrum with minimal
  interference.
• 2 spread spectrum techniques
• Frequency hopping spread spectrum (FHSS)
• Direct sequence spread spectrum (DSSS)

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What is spread spectrumradio technology?

• FHSS
• send a short burst of data
• shift frequencies (hop)
• send another short burst.
• DSSS
• communicate by splitting each byte of data into
  several parts
• sending them concurrently on different
  frequencies
• FHSS
• relatively simple radio design
• but limited to speeds of no higher than 2 Mbps
• leads to high amount of hopping.
• DSSS
• uses a lot of the available bandwidth, about 22
  megahertz (MHz)
• capable of much greater speed than FHSS since the
  devices can send a lot more data at the same
  time.

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Security

• SSID
• Each access point is associated with a SSID
  (service set identifier)
• To access the network a client computer should be
  configured with the correct SSID
• MAC
• Each client computer has a unique MAC (Media
  Access Control) address. Each access point is
  programmed with a list of MAC addresses so it
  allows only those to associate with the AP.
• WEP
• Wireless transmissions are easier to intercept
  than transmissions over wired networks.
• WEP (Wired equivalent privacy) employs the
  symmetric key encryption algorithm, Rons Code 4
  Pseudo Random Number Generator (RC4 PRNG).

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802.11 vs. Bluetooth

• Technology
• Bluetooth uses FHSS (Frequency Hopping Spread
  Spectrum )
• 802.11 used FHSS and DSSS. Currently 802.11b
  uses only DSSS for higher data transfer
  capability. 802.11a and 802.11g use a Orthogonal
  Frequency Division Multiplexing (OFDM) scheme in
  the 5 and 2.4-GHz frequency range, respectively
  
• Coverage
• Bluetooth covers a personal area (PAN) the
  space of a room (up to 30 feet).
• 802.11specifications provide coverage for local
  area networks (LANs) an office building or
  parts of a campus using multiple access points
  (APs). Each AP has a range of up to 300 feet.

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Cellular Phone Systems

• TDMA
• FDMA
• CDMA
• Cell Phones Generations
• Specifications
• Improvements
• Future Plans

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Frequency Division Multiple Access(FDMA)
Frequency
Each user is assigned one frequency to
transmit. Example AMPS
W Hz
User 4
User 3
User 2
User 1
Time
T sec
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Time Division Multiple Access(TDMA)
Frequency
W Hz
Time
User 1
User 2
User 3
User 4
T sec
Several users transmit at the same frequency but
in different time slots. Example GSM and
IS-136 Used by ATT and T-Mobile
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Code Division Multiple Access(CDMA)

• Each user transmits all the time over all the
  frequency band, but has a different spreading
  code.
• The base station differentiates users based on
  their codes.
• Example IS-95 (cdmaOne)
• Used by Sprint and Verizon

Code 1
Code 2
Code 3
Code 4
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CDMA Pros Cons

• Advantages
• Interference rejection
• Provides security / privacy
• Simple to add users to system
• Greater coverage with fewer cell sites
• Disadvantages
• Near-Far Problem
• Solution ?

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Frequency Reuse
FDMA TDMA Need frequency planning Adjacent
cells ? Different Frequencies
CDMA NO need for frequency planning Adjacent
cells ? Same freq. Separated by code channels
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The Near-Far Problem

• Nearby mobiles ? strong signal
• Far away mobiles ? weak signals

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Power Control in CDMA

• Mobiles adjust power at which they transmit.
• Base station receives all signals at the
  appropriate power.
• The CDMA network independently controls the power
  at which each mobile transmits.
• Extra advantage Extended battery life

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Generations of Cell Phones
AMPS 1983
GSM 1992 IS-95 1993 IS-136 1996
cdma2000 2002 WCDMA 2002
Higher data rates for integration of mobile
multimedia services
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Comparison of variouscellular standards
Name Year Originated Multiple Access Data Rate
  Introduced From Scheme  
AMPS 1983 US FDMA 19.2 kbps
GSM 1992 Germany TDMA 22.8 Kbps
IS-136 1996 US TDMA 13 Kbps
IS-95 1993 US CDMA 19.2Kbps
cdma2000 2002 US CDMA up to 2.07 Mbps
WCDMA 2002 Europe CDMA up to 2.04 Mbps
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Generations of Cell Phones

• 1G
• Phones are only capable of making and receiving
  voice calls.
• 2G
• Phones can receive and send pieces of data
• E-mails, Web pages, etc
• Updated versions of TDMA and CDMA allow features
  like caller ID and SMS (short message service)
• 3G
• Phones can receive and send both voice and data,
  but at speeds of about 144kbps, which is similar
  to what a broadband Internet connection offers PC
  users.
• Current applications under development include
  geo-location capabilities using Global
  Positioning Systems (GPS), audio and video
  streaming, and other types of entertainment.

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Goals of 3G

• Rates
• 2 Mbps in fixed applications
• Up to 384 Kbps when a device is moving at
  pedestrian speed
• 128 Kbps in a car

• Offer services like
• Increased Bandwidth
• Wireless voice
• Video
• Email
• Web browsing
• Videoconferencing

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Goals of 4G

• Enable mobile phones to be a combined
• Camera
• Video camera
• Computer
• Stereo
• Radio

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CDMA Experiment

• Equipment
• PN Code Generator
• Carrier Frequency
• Oscilloscope

• Antennas (Transmitter Receiver)
• Signal source
• Computers with LAWN software

• Objectives
• Understand concept of CDMA
• Understand how PN code generator works
• Demonstrate jamming / interference

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Summary

• Future for Bluetooth and 802.11
• Can they coexist?
• 802.11 ? Mobile LAN access
• Long term Bluetooth will be built in.
• Currently User has to choose between the two
  technologies.
• Bluetooth is cheap!!!
• 802.11e may have been designed to combat with
  Bluetooth.
• Frequency hopping

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Summary

• Cellular Phone Systems
• CDMA ? wider bandwidth, power efficient,
  interference rejection, security, more
  users. BUT Near-Far Problem !
• Solution Power Control
• TDMA ? Mostly used in Europe, partially in the US
  (ATT and T-Mobile)
• FDMA ? Previously used by AMPS (1G)
• Generations of cell phones (1G to 4G)
• Higher data rates, more multimedia features
  available
• Experiment
• PN Code generator, Frequency Jamming

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References

• a, b, e, and g--What 802.11 means to me (and you,
  too), David Coursey, Executive Editor, AnchorDesk
  
• L.M. Correia and R. Prasad, An Overview of
  Wireless Broadband Communication, IEEE
  Communication Magazine, Jan. 1997, pp.28-33
• Naveen Chandran and Matthew C. Valenti, Three
  generations of cellular wireless systems
• http//www.qualcomm.com/
• http//www-2.cs.cmu.edu/dpwu/books/EE
• Bluetooth versus 802.11, Nick Hunn, TDK Systems,
  www.cellular.co.za
• http//www.palowireless.com
• www.10meters.com/blue_802.html maintained by
  Karen E. Peterson and Caroline Scarborough
• http//www.hoti.org/hoti9_tutorial.html, lecture
  by Pravin Bhagwat, ReefEdge Inc.
• http//grouper.ieee.org/groups/802/11/main.html
• http//www.utexas.edu/its/wireless/faqs/80211
• http//www.oreillynet.com/pub/a/wireless/