1. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 1 Telephone Communications

2. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 2 Internet Communications Largely carried on telephone network Lately quite a bit of privately owned fiber –communication carriers –electric companies –private organizations Some carried over television cables New conveyance by wireless providers

3. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 3 Present Telephone Conveyance ATM backbone (long distance) ATM switching at core T1 data lines to businesses (1.544 Mb/s) Copper “last mile” –voice grade lines –DSL possible using residual bandwidth outside the voice channel - has distance limitations

4. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 4 Terms ATM - Asynchronous Transfer Mode DSL - Digital Subscriber Line DSLM - DSL Modem DSLAM - DSL Access Module POTS - Plain Ordinary Telephone System SONET - Synchronous Optical NETwork

5. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 5 TelCo Network Interface

6. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 6 Residential Data Lines POTS line with modem –56 kb/s –rate depends on line quality DSL line with splitter/modem* – Advanced, up to 1.5M / 128K$59.95/month –Premium, up to 384K / 384K $69.95/month –Professional, up to 1.5M / 384K$79.95/month ------------------------------------------------------------- *Speed depends on distance to TelCo office

7. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 7 Digital Data Transmission Binary data Transmitted as pulses Pulses shaped by line bandwidth Pulses have high frequency components Limiting bandwidth limits data rate

8. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 8 Fourier Series of Bandlimited Pulse

9. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 9 Fourier Transform of Pulse

10. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 10 Notes: First crossover of spectral amplitude is at B 2B is effective bandwidth needed to transmit through noiseless channel.

11. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 11 Nyquist Bit Rate Relates three transmission variables: –Channel Capacity (C) –Bandwidth (B) –Signal levels (L) – quantization levels –Formula: C = 2Blog 2 [L] Noise-free channel assumed

12. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 12 Nyquist Example: Formula: 2BLog 2 [L] Example: L = 1 (binary signals) B = 3000 Hz (300 – 3300 Hz) C = 2*6000*1 = 6000 [bits/s] Note: Applies to noise-free channel only

13. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 13 Shannon Formula C = B log 2 (1 + SNR) Example: –B = 3000 Hz (300 – 3300 Hz) –SNR = 3163 (35 dB power ratio) –C = 34,882 [bits/s]

14. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 14 All Digital Telephony Voice-to-Digital conversion coding at transmitter Digital transmission Digital-to-Voice code conversion at receiver Conversions performed by COder-DECoder (CODEC) module at each end of line

15. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 15 Voice-Data Conversion CODEC VoiceDataVoice (8 bits)

16. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 16 Digital Data Frame on T1 Line Voice lines are low-pass filtered to 3.1 KHz CODEC output is 8 bits wide Sampling rate is about 8000 samples/s Data rate is thus about 64000 bits/sec 24 lines carried on T1 link (1.544 Mb/s)

17. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 17 T1 Time-Division Multiplexing Data frame starts with framing bit Data samples (8 bits each) 24 lines each supply a data sample every 125 microseconds (0.000125 sec) Samples are sequentially multiplexed 193 bits per data frame 1.544 Mb/s total data rate

18. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 18 Time Division Multiplexing Multiplexer Line 1 Line 2 Line n... Line 1Line 1 Line 2Line 2 Line nLine n

19. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 19 Time Division De-Multiplexing De-Multiplexer Line 1 Line 2 Line n... Line 1Line 1 Line 2Line 2 Line nLine n

20. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 20 De-Multiplexing Data samples are redistributed into lines Low-pass filter recovers analog voice

21. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 21 High-Speed Backbone 28 T1 streams merged to T3 stream ATM cells repackage data at core –53 octets/cell 5 octets of header information 48 octets of data SONET frames –8 x 810 = 6480 bits sent 8000 times per second –51.85 Mb/s data rate (some frame overhead)

22. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 22 ATM Cell Transmission Time ATM Cell... ATM Cell

23. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 23 TelCo Standard Data Rates T11.544 Mb/s (24 voice circuits) T344.736 Mb/s (672 voice circuits) OC-3155.52 Mb/s (2430 voice circuits) OC-12622.08 Mb/s (9720 voice circuits) OC-482488.32 Mb/s (19440 voice circuits) OC-1929953.28 Mb/s (38880 voice circuits)

24. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 24 Future Network Interface

25. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 25 - Network Backbone fiber combines 16 OC-192 lines Each is given a different wavelength All data streams merged into single fiber Streams split by wavelength 16 OC-192 lines out Switches to TelCo customers

26. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 26 Optical-Data Conversion LASERDIODE CopperFiberCopper ( )

27. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 27 Optical Data Conversion Data on wire drives tunable laser Laser emits photon pulses Photons propagate down fiber Photon energy activates receiving diode Diode produces voltage or current Amplifier drives wire

28. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 28 Transmission Problems Photons lost at fiber coupling Photons lost in fiber due to scattering Photons per pulse deteriorates with length Repeater amplifiers needed

29. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 29 Optical-Data Link LASERDIODE Copper Fiber Copper ( ) Repeater Fiber ( )

30. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 30 More Problems Repeaters require external power Photons need conversion to voltage, amplification, and then reconversion to photons - data rate bottleneck!

31. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 31 Repeater for Fiber Optic Line DiodeLaser Fiber Copper Fiber ( ) Amplifier Copper ( )

32. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 32 Wave Division Multiplexing Laser Line 1 Line 2 Line n... Laser WDM Fiber

33. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 33 Wave Division Multiplexing Incoming data converted to photons Photon streams have individual frequencies Streams can be merged onto single fiber Streams propagate without interference

34. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 34 WDM Problems Limited number of “colors” of photons Repeaters must work on all “colors”

35. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 35 Repeaters for WDM Must amplify all photon “colors” Must not cause interaction between photon streams

36. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 36 Pumped Laser Repeater Pumped Laser Fiber ( ) Pump PhotonEnergy

37. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 37 Pumped Laser Repeater Rare-earth doped glass Pumped by external light Photons receive excitation and are amplified Amplification of all photon “colors”

38. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 38 WDM De-multiplexing Photon stream split by “colors” Separated streams may be converted to voltage pulses

39. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 39 Wave Division De-Multiplexing Line 1 Line 2 Line n... WDM Fiber DIODE 1 2 n

40. 9/9/2015© 2010 Raymond P. Jefferis IIILect 02 - 40 WDM Routing Data streams must be switched Ideally this should be optical Optical switching of SONET frames? Electro-optics? State-of-the-art - developments taking place rapidly (Lucent, Nortel, others)