Signal Multiplexing

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Signal Multiplexing

• Christopher Kruse, Presenter
• Clarke College

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What is multiplexing?

• Multiple data streams over shared medium
• Resource sharing
• Less expensive
• Involves two steps
• MUX and DEMUX
• If for communication, known as Multiple Access
• Think of talking in a crowded room

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Categories of MUX

• Time-Division MUX (TDM)?
• Looks like simultaneous transfer
• Connections take turns on the wire
• Frequency-Division MUX (FDM)?
• Signals use different ranges of frequency
• Completely synchronous

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Rare MUX types

• Wavelength-Division MUX (WDM)?
• Form of FDM
• Used in optical communications
• color is difference
• Spatial MUX
• Used in MIMO connections
• Parallel connection over multiple antennas

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Code-Division MUX (CDM)?

• Digital signals only
• Uses spread spectrum technology
• Takes wider bandwidth (a spectrum)?
• Frequency Hopping SS (FHSS)?
• Variable frequency transmitter
• Need to recieve on different freq. In the
  spectrum
• Direct Sequence SS (DSSS)?
• Uses digitally-encoded chips
• Process used by CDMA cellular phone systems

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Application Cell Phones

• Channel Access methods
• FDMA
• Includes OFDMA
• TDMA
• SSMA
• Includes CDMA
• SDMA

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Cell phone Tech

• 1G
• Provided analog voice transmission
• Used IMTS, AMPS
• Much like wired structure (LATA ? MTSO, IXC ? MSC
• 2G
• Provided digital voice transmission
• Used D-AMPS, GSM, CDMA

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Cell phone Tech 2

• 3G Current
• Provides digital data signals in addition to
  voice
• Uses UTMS, CDMA2000, FOMA (Japan)?
• Had a 2.5G data transfer category
• EDGE Enhanced data for GSM Evolution
• GPRS General Packet Radio Service
• Newer style
• EVDO Evolution Data Optimized

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Cell phone Tech 3

• 4G Upcoming
• No more split!
• Agreement to use one protocol LTE
• LTE Long Term Evolution
• Seamlessly connects to GSM and CDMA
• Uses OFDMA to transfer

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Code Division Multiple Access(CDMA)?

• Name of technology and of cell phone network type
• Cell network that Verizon/Sprint runs on
• Owned by Qualcomm
• Uses spread spectrum to pass multiple signals at
  higher data rates
• More data sent than used for communication
• Underlying tech for 1G, 2G, 3G phones
• Replaced in coming 4G by OFDMA

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Orthogonal Frequency-Division Multiple Access
(OFDMA)?

• Parallel stream FDM
• Uses multiple sub-carriers to carry data
• Uses FFT to lower cost of DSP
• Multiple Access
• A subset of sub-carriers represent a user
• Advantages over CDMA
• Better MIMO support
• Flexibility over many bands of frequency.