1. 1 WCA102 Fundamentals of Digital Modulation Digital Modulation – Introduction Digital Modulation in Wireless Communications

2. Agenda  Introductions  Who Cares?  What is Modulation  IQ Modulation Types  Filters and How Things Go Wrong  Measurements

3. Advantages of Digital Modulation  Spectral efficiency – use of a narrow bandwidth to send a large amount of data  Effective use of limited frequency resources  Good privacy and security features  Digital encryption techniques may be employed  Lower power consumption  Repeatable, more easily produced  Reduced device size

4. Modulation for Wireless  Media  Carrier  The 3 essential parameters  Amplitude value A(t)― Amplitude Modulation  Frequency value f(t)― Frequency Modulation  Phase value φ(t)― Phase Modulation V(t) = A cos(2πfc t + Φ)

5. Analog Modulation  Amplitude Modulation  AM radio  Frequency Modulation  FM radio, TV audio signal  Phase Modulation  TV color image signal (including Amplitude Modulation)

6. Transmission of a Digital Message  Basically, it’s the same as Analog Modulation Methods  ASK:Amplitude shift keying  FSK:Frequency shift keying  PSK:Phase shift keying  Digital modulation: Amplitude, frequency and/or Phase are used to represent a digital state V(t) = A(t) cos(2πfc t + Φ) V(t) = A(t) cos(2πf(t) t + Φ) V(t) = A(t) cos(2πf(t) t + Φ(t))

7. ASK  Amplitude shift keying  1’s or 0’s represented by different amplitudes  Could be accomplished with an AM system = +

8. ASK in IQ domain  ASK(OOK)  I: In phase component  Q: Quadrature component I Q 0 0 I Q Amplitude variation on I axis (0) (1)

9. FSK  Frequency shift keying  Select frequency based on each bit, 0 or 1  Could be done with simple FM system + =

10. FSK in IQ I Q  Frequency change causes constant-rate phase change versus the reference carrier  Amplitude remains constant on the IQ circle  If the phase change is 90 degrees in one symbol period, the modulation type is called Minimum Shift Keying (remember this one) 1Sp2Sp3Sp4Sp5Sp Time Phase π －π－π Pos offsetNeg. OffsetPos. Offset 1 Symbol only turns π(ex)

11. PSK  Phase shift keying  At the bit transitions invert the phase by 180° + =

12. Representation of PSK in IQ  PSK  Specifically, BPSK(Binary Phase Shift Keying) I Q 0 0 I Q Change Phase to 180° Relative to reference (1) (0)

13. 13 Digital Modulation in Modern Wireless Systems

14. Digital Modulation Block Diagram Compression, Error Correction, Encryption Raw Data 110101 011010100101 Convert to Symbols 01 10 10 10 01 01 00 01 10 11 Modulation Mapping I - Signal Q - Signal Low Pass Filter To IQ Modulator I - Signal Q - Signal Modulation, Upconversion RF Amplifier

15. Raw Data Conversion  Raw data comes from the user  Digitized voice, keystrokes, jpegs…  Compression is employed for efficiency  Error correction is applied for transmission quality  Interleaving creates signal-dropout resistance  Encryption is applied for security Compression, Error Correction, Interleaving, Encryption Raw Data 110101 011010100101 Convert to Symbols

16. Data Bits, to Symbols  Symbols are represented by the possible states of digital modulation  Higher order modulation allows more bits per symbol  What in the world does that mean?  Mapping symbols to I and Q Compression, Error Correction, Encryption Raw Data 110101 011010100101 Convert to Symbols 01 10 10 10 01 01

17. IQ Mapping  What is Mapping:  Translate a Symbol to a point in the IQ space  Example I Q (00) (11) (10) (01) 00 01 10 11 Modulation Mapping

18. Differential Modulation  QPSK(Quadrature PSK)  Assign the value to points in IQ Space  DQPSK(Differential QPSK)  The value is based on the transitions between 2 points I Q I Q (00) (11) (10) (01) (11) (10) (00) 00= 0 01= +90 10= -90 11= +180

19. Higher Order Modulation  8PSK(8-PSK)  Assign the value to points in IQ Space  3 points per symbol   /4 DQPSK  The value is based on the transitions between 2 points  Eliminates Zero Crossings I Q (000) (011) (010) (001) (111) (101) (110) (100) I Q (00) (10) (01) (11) 00= -45 01= +135 10= -135 11= +45

20. More Higher Order Modulation  16QAM(16-Quadrature Amplitude Modulation)  Each IQ symbol location is represented by 4 data bits  64QAM (64-Quadrature Amplitude Modulation)  Each symbol is now worth 5 bits I Q (0000)(0100)(1100)(1000) (0001)(0101)(1101)(1001) (0011)(0111)(1111)(1011) (0010)(0110)(1110)(1010) I Q (011011)(010011)(110011)(111011) (011010)(010010)(110010)(111010) (011110)(010110)(110110)(111110) (011111)(010111)(110111)(111111) (000011)(001011) (000010)(001010) (000110)(001110) (000111)(001111) (101011)(100011) (101010)(100010) (101110)(100110) (101111)(100111) (011101)(010101)(110101)(111101) (011100)(010100)(110100)(111100) (000101)(001101) (000100)(001100) (101101)(100101) (101100)(100100) (011000)(010000)(110000)(111000) (011001)(010001)(110001)(111001) (000000) (001000) (000001)(001001) (101000)(100000) (101001)(100001)

21. Why Not Just Keep Going?  Errors in IQ modulation create symbol errors in transmission  Vector Errors are created (what’s that?)  Noise in the transmission channel create symbol errors  Inaccuracies in the receiver creates errors  Signal-to-noise requirements increase with higher order modulations I Q (0000)(0100)(1100)(1000) (0001)(0101)(1101)(1001) (0011)(0111)(1111)(1011) (0010)(0110)(1110)(1010) I Q (00) (11) (10) (01)

22. The World’s Most Popular Modulation  Gaussian Minimum Shift Keying  Gaussian Filtered Form of FSK  Sum of I and Q results in a constant amplitude circle

23. Symbol Rate and Bit Rate  Modulation type determines number of bits per symbol  BPSK1 bit/symbol  DBPSK1 bit/symbol  QPSK2 bit/symbol  p/4 DQPSK2 bit/symbol  DQPSK2 bit/symbol  8PSK3 bit/symbol  16QAM4 bit/symbol  64QAM5 bit/symbol  256QAM6 bit/symbol  For a fixed symbol rate, having more bits will provide a faster transfer rate  Setting up a WCA requires you to know the modulation type and symbol rate, not the bit rate

24. Others (for evening reading….)  32QAM  ADSL etc  256QAM  Microwave Communication  Some Cable Modem  1024QAM  Still experimental  OQPSK  Offset QPSK  Used to avoid zero crossings  DQPSK  HPSK  Hybrid Phase Shift Keying  Also known as Orthogonal Complex Quadrature Phase Shift Keying (OCQPSK)  Used in CDMA2000 (1xRTT) reverse link  VSB  Vestigial Side Band  8VSB, 16VSB  US Digital Broadcast TV

25. Filters, For Spectrum Control 00 01 10 11 Modulation Mapping I - Signal Q - Signal Low Pass Filter To IQ Modulator

26. Sources of Error Compression, Error Correction, Encryption Raw Data 110101 011010100101 Convert to Symbols 01 10 10 10 01 01 00 01 10 11 Modulation Mapping I - Signal Q - Signal Low Pass Filter To IQ Modulator I - Signal Q - Signal Modulation, Upconversion RF Amplifier

27. Sources of Error  IQ Quadrature modulation 90 Q I fc 90° sin(2πfct) cos(2πfct) LPF BPF

28. Errors Receiving the Signal  IQ Quadrature demodulation  This could be your customers receiver, or it could be a WCA vector spectrum analyzer cos(2πfct) 90 Q I fc 90° sin(2πfct) LPF BPF

29. 29 Common Measurements

30. What data was sent?  Data Display  Time vs. Amplitude  Error Summary

31. Error Summary  Error Vector Magnitude  Magnitude and Phase Error  Freq. Error  IQ offset

32. Modulation Errors vs. Time  Amplitude errors correlated to EVM  WCA is especially good at this

33. What can a WCA do?  Modulation types  Symbol rates  Filter types  One button setups  Standards

34. Summary  Digital modulation is cheaper, faster, more accurate, more efficient, more secure  Higher order modulation is used for greater transmission rates in the same spectrum occupancy  Higher order modulation is more susceptible to noise  Baseband filters are used to control spectrum  Wireless Communications Analyzers are used to evaluate modulation quality  WCA is particularly good at connecting effects in multiple domains

35. Product Line Contact Information  Dedicated Regional Contacts  Kurt Krukenberg phone: +1 503-627-5039 Regional Product Manager Americas  Dean Miles phone: +44 1344-392249 Regional Product Manager EMEA  Charles Wu phone: +852 258-56774 Product Line Representative Asia/PacRim  Worldwide Factory Contacts  Dave McDonald phone: +1 503-627-1279 TSC Primary Contact WCA200A and WCA300  Tommy Sakurada phone: +81 3-3448-3272 Product Manager WCA200A & Wireless Apps  Jerry Harris phone: +1 503-627-4827 Product Manager WCA300 & Non-Wireless Apps

36. 36 Slide Archive (extras)

37. Filters Alter The Signal 00 01 10 11 Modulation Mapping I - Signal Q - Signal Low Pass Filter To IQ Modulator

38. Common Filter Types  Gaussian  Raised Cosine  Root Raised Cosine  Setting up the WCA requires knowledge of what filter is used

39. Effect of Roll-off  Usually α is between 0.2 - 0.5  α determines the bandwidth α=0.0α=1.0 BW = (1+α) *Symbol rate

40. Put IQ on the Carrier Wave  IQ Quadrature modulation 90 Q I fc 90° sin(2πfct) cos(2πfct) LPF BPF

41. Structure of Tx/Rx Scrambling Error correction encoding Interleaving 1stInterleaving 2nd Data stream IQ mappingIQ modulation Scrambling Error correction decoding De-interleaving 1st De-interleaving 2nd Data stream IQ de-mappingIQ demodulation Encode