1. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 1 Chapter 7 Multiple Division Techniques

2. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 2 Outline Frequency Division Multiple Access (FDMA) Time Division Multiple Access (TDMA) Code Division Multiple Access (CDMA) Comparison of FDMA, TDMA, and CDMA Walsh Codes Near-far Problem Types of Interferences Analog and Digital Signals Basic Modulation Techniques Amplitude Modulation (AM) Frequency Modulation (FM) Frequency Shift Keying (FSK) Phase Shift Keying (PSK) Quadrature Phase Shift Keying (QPSK) Quadrature Amplitude Modulation (QAM)

3. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 3 Frequency Division Multiple Access (FDMA) User 1 User 2 User n … Time Frequency Single channel per carrier All first generation systems use FDMA

4. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 4 Time Division Multiple Access (TDMA) User 1User 2User n … Time Frequency Multiple channels per carrier Most of second generation systems use TDMA

5. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 5 Code Division Multiple Access (CDMA) User 1 Time Frequency Users share bandwidth by using code sequences that are orthogonal to each other Some second generation systems use CDMA Most of third generation systems use CDMA User 2 User n Code...

6. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 6 Types of Channels Control channel Forward (Downlink) control channel Reverse (Uplink) control channel Traffic channel Forward traffic (traffic or information) channel Reverse traffic (traffic or information) channel

7. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 7 Types of Channels (Cont’d) MSBS f1’f1’ f2’f2’ fn’fn’ f ’ f … Reverse channel (Uplink) Forward channels (Downlink) f1f1 f2f2 fnfn … Control channels Traffic channels

8. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 8 FDMA MS #1 MS #2 MS #n BS f1’f1’ f2’f2’ fn’fn’ f1f1 f2f2 fnfn … …… Reverse channels (Uplink) Forward channels (Downlink)

9. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 9 FDMA: Channel Structure 123 … N Frequency Total Bandwidth W=NW c Guard Band W g 4 Sub Band W c Frequency Protecting bandwidth … f1’f1’f2’f2’fn’fn’ … f1f1 f2f2 fnfn Reverse channelsForward channels

10. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 10 MS #1 MS #2 MS #n BS … … Reverse channels (Uplink) Forward channels (Downlink) t Frequency f ’ #1 … … Frame Slot … #1 … Frame … t Frequency f Frame … t #2 … … … t #n … … … #2 … … t … #n … … t TDMA

11. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 11 TDMA: Channel Structure … t f #1#2 #n#1#2#n … (a). Forward channel … #1#2 #n Frame … t f ’ #1#2 #n#1#2#n … (b). Reverse channel … #1#2 #n Frame

12. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 12 TDMA: Frame Structure (Cont’d) … Time Frequency f = f ’ #1#2 #n#1#2#n … Forward channel Reverse channel … #1#2 #n Forward channel Frame #1#2#n … Reverse channel Channels in Simplex Mode

13. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 13 TDMA: Frame Structure (Cont’d) … Time Frequency #1#2 #n#1#2#n …… #1#2 #n Frame HeadData Guard time

14. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 14 Code Division Multiple Access (CDMA) MS #1 MS #2 MS #n BS C1’C1’ C2’C2’ Cn’Cn’ C1C1 C2C2 CnCn … …… Reverse channels (Uplink) Forward channels (Downlink) Frequency f ’ Note: C i ’ x C j ’ = 0, i.e., C i ’ and C j ’ are orthogonal codes, C i x C j = 0, i.e., C i and C j are orthogonal codes Frequency f

15. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 15 Comparisons of FDMA, TDMA, and CDMA (Example) OperationFDMATDMACDMA Allocated Bandwidth12.5 MHz Frequency reuse771 Required channel BW0.03 MHz 1.25 MHz No. of RF channels12.5/0.03=416 12.5/1.25=10 Channels/cell416/7=59 12.5/1.25=10 Control channels/cell222 Usable channels/cell57 8 Calls per RF channel14*4* 40 ** Voice channels/cell57x1=5757x4=2288x40=320 Sectors/cell333 Voice calls/sector57/3=19228/3=76320 Capacity vs FDMA1416.8 * Depends on the number of slots ** Depends on the number of codes Delay ? ? ?

16. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 16 Digital signal s(t) Code c(t) Spreading signal m(t) Code c(t) Digital signal s(t) SpreadingDespread Frequency Power TransmitterReceiver Direct Sequence Spread Spectrum for CDMA

17. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 17 Digital signal Hopping Pattern Spreading signal Digital signal SpreadingDespread Frequency Power Hopping Pattern TransmitterReceiver Concept of Frequency Hopping Spread Spectrum

18. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 18 Time Frequency An Example of Frequency Hopping Pattern

19. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 19 Walsh Codes (Orthogonal Codes) Wal (0, t) t Wal (1, t) t Wal (2, t) t Wal (3, t) t Wal (4, t) t Wal (5, t) t Wal (6, t) t Wal (7, t) t

20. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 20 MS 1 MS 2 BS Distance 0 d2d2 d1d1 Received signal strength MS 1 MS 2 BS Near-far Problem

21. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 21 Frequency Baseband signal Frequency Interference baseband signals Spreading signal Frequency Despread signal Interference signals Interference in spread spectrum system in CDMA Types of Interference in CDMA

22. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 22 Adjacent Channel Interference in CDMA f1f1 f2f2 Channel 1 Channel 2 Frequency Power

23. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 23 Power Control in CDMA Controlling transmitted power affects the CIR P t =Transmitted power P r =Received power in free space d =Distance between receiver and transmitter f =Frequency of transmission c = Speed of light  = Attenuation constant (2 to 4)

24. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 24 Modulation Why need modulation? Small antenna size Antenna size is inversely proportional to frequency e.g., 3 kHz  50 km antenna 3 GHz  5 cm antenna Limits noise and interference, e.g., FM (Frequency Modulation) Multiplexing techniques, e.g., FDM, TDM, CDMA

25. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 25 Analog and Digital Signals Analog Signal (Continuous signal)  Digital Signal (Discrete signal) Time Amplitude Time Amplitude 1 1 1 1 0 0 Bit + _ 0 0 S(t)

26. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 26 Hearing, Speech, and Voice-band Channels Voice-grade Telephone channel Human hearing Human speech Frequency (Hz) Pass band Frequency cutoff point Guard band 100 02003,5004,000 10,000..

27. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 27 Amplitude Modulation (AM) Message signal x(t) Carrier signal AM signal s(t) Amplitude of carrier signal is varied as the message signal to be transmitted. Frequency of carrier signal is kept constant. Time

28. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 28 Frequency Modulation (FM) FM integrates message signal with carrier signal by varying the instantaneous frequency. Amplitude of carrier signal is kept constant. Carrier signal Message signal x(t) FM signal s(t) Time

29. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 29 Frequency Shift Keying (FSK) 1/0 represented by two different frequencies slightly offset from carrier frequency Message signal x(t) Carrier signal 2 for message signal ‘0’ Carrier signal 1 for message signal ‘1’ FSK signal s(t) 1 0 1 1 0 1 Time

30. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 30 Phase Shift Keying (PSK) Use alternative sine wave phase to encode bits Carrier signal Message signal x(t) 1 0 1 1 0 1 PSK signal s(t) Time

31. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 31 QPSK Signal Constellation Q I 0,01,1 0,1 1,0 Q I 01 (a) BPSK (b) QPSK

32. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 32 All Possible State Transitions in  /4 QPSK

33. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 33 Quadrature Amplitude Modulation (QAM) Combination of AM and PSK Two carriers out of phase by 90 deg are amplitude modulated