Multiplexing

1
Multiplexing
2
Multiplexing

• Sharing by Multiple Sources or Users
• Example Stereo FM
• Principle of Orthogonality Minimize
  Interference
• Quadrature phase
• Polarization
• Frequency spectrum (FDM)
• Pulse timing (TDM)
• User code (CDMA)
• Schemes
• Fixed
• Dynamic or on demand

3
FDM

• Individual Carrier
• Filters bandpass, tunable
• Multiplexer
• Demultiplexer
• Multi Carrier OFDM
• Wireless multipath delay, interference, fading
• OFDM bwrc.eecs.berkeley.edu/
• Classes/EE225C/Lectures/Lec16_ofdm.pdf
• FFT

4
OFDM

• Mobile Environment
• Multi-path
• Time domain echo and delay
• Frequency dependent loss and phase
• OFDM
• Multi carriers at low data rate
• Delay ltlt symbol time
• Efficient use of bandwidth
• Efficient use of resources
• FFT versus local oscillators and mixers
• Orthogonality
• Frequencies N / Symbol period

5
OFDM Block Diagram

• Transmitter
• Serial to parallel conversion
• Signal mapping
• IFFT
• Guard or
• cyclic prefix
• Parallel to serial
• D/A
• RF
• Receiver
• RF
• A/D
• Serial to parallel
• FFT
• Sub-band detection
• Parallel to serial

6
OFDM Projects

• http//cegt201.bradley.edu/projects/proj2001/ofdma
  bsh/
• http//eesof.tm.agilent.com/pdf/wireless_networkin
  g_04.pdf

7
FDM

• Mux
• Linear Summing Amplifier
• Demux
• Mixer and Low Pass Filter
• Similar to AM or FM detection

8
FDM

• Source Tomasi Electronic Comm

9
FDM

• Frequency Separator / Combiner
• Diplexer
• Source Filter Solutions

10
TDM

• Pulse Interleaving
• Clock
• Synchronous
• Asynchronous
• Dynamic, on demand
• Source Forouzan Data Network

11
TDM Mux Circuits

• Parallel to Serial
• Mux Switch
• 74151 81 mux chip

12
TDM De-Mux Circuits

• Serial to Parallel
• Shift Register
• Demux Switch

13
High Speed Mux Chip

• Mux, demux chips
• Infineon 15 G/s

14
Digital Telephone Hierarchy

• North American Digital Hierarchy
• DS-0 1 64 Kbits/sec
• DS-1 24 1.544 Mbits/sec
• DS-3 672 44.736 Mbits/sec
• OC-1 1 DS-3 51.84 Mbits/sec
• OC-3, 12, 48, 192, 768
• Source Forouzan Data Network

15
Phone TDM

• T1 Line Signaling
• Source Tomasi Electronic Comm

16
Analog Telephone Hierarchy

• CCITT FDM Hierarchy
• Channel 1 channel (4kHz)
• Group 12 channels (48 kHz)
• SuperG (5 G) 60 channels (240 kHz)
• MasterG (5 SG) 300 channels (1.2 MHz)
• JumboG (3 MG) 900 channels (3.6 MHz)
• Analog

17
Spread Spectrum

• Direct Sequence
• Data
• Narrow band
• Chips
• Pseudoramdon
• Broadband
• Correlation
• Balanced modulator
• Frequency Hop
• Pseudorandom carrier
• http//www.sss-mag.com/pdf/Ss_jme_denayer_intro_pr
  int.pdf
• http//www.maxim-ic.com/appnotes.cfm/appnote_numbe
  r/1890

18
CDMA

• Full Spectrum, All the Time
• Code
• Chip rate gt Data rate
• Advantages
• No. of users
• Interference
• http//www.tsp.ece.mcgill.ca/Telecom/Docs/cdma.htm
  l

19
CDMA Code

• Code Generators
• http//www.mathworks.com/access/helpdesk/help/tool
  box/commblks/ug/fp42065.html
• http//www.maxim-ic.com/appnotes.cfm/appnote_numbe
  r/918

20
Pseudorandom Number Generator

• Simple Linear Feedback Shift Register
• Maximum length or M-sequence
• Cross correlation
• Orthogonality and crosstalk
• Auto correlation
• Multipath

21

• Gold Code
• Kasami Code
• Hadamard-Walsh Codes

22
http//www.maxim-ic.com/appnotes.cfm/appnote_numbe
r/918
23
CDMA Receiver

• Matched Filter
• http//cnx.rice.edu/content/m12464/latest/
• Rake Receiver
• http//www.comlab.hut.fi/opetus/238/lecture4_Intro
  _to_WCDMA.pdf

24
Adaptive Filtering

• Time Varying Channel
• Tracking
• Channel Estimation
• Prediction
• Adaptation
• Correction
• Optimization
• Algorithms
• http//www.mathworks.com/matlabcentral/fileexchang
  e/loadFile.do?objectId9259objectTypefile

25
Optical Multiplexing

• Coarse WDM
• 20 nm
• Coupler
• Micro-optics
• Dense WDM
• 200 GHz, 100 GHz
• Thin film
• Array waveguide
• Fiber Bragg grating
• Applications
• http//www.wavesplitter.com/products/index.htm

26
Chapter Review

• Multiplexing
• Orthogonality
• FDM
• Summing amplifier
• Add drop filter
• TDM
• Logic gates
• Shift register
• Serial to parallel and vice versa
• CDMA
• WDM
• CWDM
• DWDM