Wireless Wide Area Networks

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Wireless Wide Area Networks 3G/4G - mobile
phones
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Multiplexing (collection of schemes to transmit
multiple signals simultaneously)

• FDM - Frequency-Division Multiplexing - analog,
  modulated to a fixed frequency band, channel.
• TDM - Time-Division Multiplexing - same frequency
  in alternating time slices, each channel makes
  full use of the bandwidth, GSM and D-AMPS use
  TDM
• CDM - Code-Division Multiplexing - makes better
  use of frequency than FDM and TDM. Signals are
  transmitted on the same frequency and same time,
  but have a unique code to identify itself. CDMA
  use CDM, of course.

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Spread Spectrum (signals in a wider band with low
power density (power per frequency), appears as
background noise to others than the receiver.
Used in CDMA and WLANs.)

• DSSS - direct-sequence spread spectrum - a
  chipping sequence code (digital modulation)
  creates a chipping sequence (shorter signals than
  original bits) that is modulated with a carrier
  signal (radio modulation). 802.11b, CDMA uses
  DSSS.
• FHSS - frequency-hopping spectrum - first
  modulates to narrowband signals, then a second
  modulation uses a hopping sequence of frequency
  to send the radio signal. Bluetooth uses FHSS.
• OFDM - orthogonal-frequency-division multiplexing
  - uses multiple subcarriers in parallel to
  transmit data. The subcarriers are orthogonal in
  that they are modulated with their own data
  independently. It is used in ADSL, 802.11a/g
  wireleess LANs, and WiMax.
• DSSS and FHSS can be multiplexed by CDM.

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Cellular generations (from the point of view of
using multiplexing and spread spectrum)

• First generation FDMA (FDM Access), where each
  cell supports a number of channels of equal
  bandwidth, and each cellphone uses two channels
  (one up and another down).
• Second generation in two groups
• TDMA (TDM Access) GSM (Global System for Mobile)
  and D-AMPS (IS-136). GSM is basically
  circuit-switching based, but GPRS (general packet
  radio service) was added to support data SGSN
  (serving GPRS support node) and GSSN (gateway
  GPRS support node).
• CDMA (CDM Access) CDMA comply with IS-95 (also
  known as cdmaOne). Uses DSSS combined with CDM.
  Designed by Qualcomm Inc, which holds IP over
  CDMA.

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Cellular bands for AMPS (1G) an analog cellular
phone system using FDMA
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AMPS reverse communication band
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Second-generation cellular phone systems
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D-AMPS (IS-136, is a digital cellular phone
system using TDMA and FDMA)
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GSM bands (digital cellular phone system using
TDMA and FDMA)
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GSM system (each voice channel is digitized and
compressed to a 13kbps digital signal)
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GSM frame and frequency bands
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IS-95 forward transmission (digital cellular
phone system using CDMA/DSSS and FDMA)
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IS-95 reverse transmission
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IMT-2000 radio interfaces (3G)
GSM
GPRSEDGE
IMT (International Mobile Telecommunication)
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GSM (3G)

• 3G data rate requirements
• 144 kbps at driving speed
• 384 kbps outside stationary speed
• 2Mbps for indoors speed
• GSM GPRS EDGE achieve 3G
• GPRS added to allow dynamic use of multiple
  channels and speeds up to 115 kbps (2.5 G)
• EDGE (Enhanced Data Rates for Global Evolution)
  added to allow speeds up to 384 kbps
• GSM uses SIM (subscriber identity module) cards
  to identify user, network, etc.

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CDMA and GSM Evolution

• CDMA 2000
• Delivered 3G speeds (CDMA-MC)
• CDMA voice and LTE data (1XEV-DO)
• VoLTE in progress
• Verizon to end CDMA in 2021
• GSM after Edge
• UMTS (W-CDMA)
• LTE
• LTE uses SIM
• Gained over 802.16 WiMax and Qualcomms Ultra
  Mobile Broadband.
• LTE co-exists with other standards, allowing in
  theory handoffs between cells supporting LTE and
  cells supporting UMTS, GSM/GPRS, 2G CDMA, CDMA-MC
  or 1XEV-DO

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New generation 4G

• Introduced around 2010
• Typical speed 3 Mbps to 5 Mbps 10 times over 3G
• Designed to give at least 2 Mbps download speeds
  to mobile customers
• Eventually, 100 Mbps to mobile users and 1 Gbps
  to stationary users
• Designed to give at least 100 Mbps download
  speeds to fixed customers
• Sufficient for high-definition video
• Runs over IP
• Wikipedia data rate comparison

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4G Technologies

• WiMAX (Worldwide Interoperability for Microwave
  Access)
• Based on 802.16 standard.
• WiMAX forum promotes it
• 802.16m will eventually provide 100 Mbps to
  mobile users and 1 Gbps to stationary users.
• Clearwire was a pioneer in its deployment
• Bought by Sprint that will shut down WiMax in
  2015
• Long Term Evolution (LTE)
• The 4G technology that most cellular carriers
  have adopted.
• Provide 14 Megabits speeds
• LTE Advanced will provide 100 Mbps to mobile
  users and 1 Gbps to stationary users.

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Differences between Wi-Fi and  3G
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Convergence of Wi-Fi and cellular technologies

• 3G and 4G Mobile Smartphones and tablets
• Often can connect directly to an 802.11 WLAN for
  service
• Typically faster speeds than cellular for data
• Cellular companies like offloading flat-fee
  subscribers to the WLAN
• Some Smart Phones Can Act as 802.11 Access Points
• Several 802.11users can share its capacity.

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Mobile computing growth
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Mobile computing technologies
Worldwide Smartphone Sales to End Users by
Operating System in 2013 (Thousands of Units)
Worldwide Tablet Sales to End Users by Operating
System, 2013 (Units)
Source Gartner (2014) 
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Mobile computing links (a few)

• My on-going series
• UB OTS Lab App
• Creating Android Apps
• Creating iOS Apps
• 16 essential Android apps for IT Professionals
• The 25 Best iPhone Apps from PC Magazine
• The 25 Best Android Apps   from PC Magazine
• Engadget
• CNet news
• Zdnet
• PC World