1、About the Course Principles of Modern Wireless Communications 现代无线通信原理全册配套现代无线通信原理全册配套 完整精品课件完整精品课件 About the Course Principles of Modern Wireless Communications Chapter 1 Introduction to Wireless Communications About the Course Principles of Modern Wireless Communications 2 Contents: About the Cour
2、se History Services Requirements Technical Challenges About the Course Principles of Modern Wireless Communications About the Course About the Course Principles of Modern Wireless Communications 4 Objectives Study principles unique to wireless commun. Wireless channel modeling Digital modulation OFD
3、M )( )( ) c n jft nn n hta t et 2( )2 ( ) ( )( ) ( ) Re( )( ) c nc l nn n jftjf t nln n r t r ta t s tt a t es tte Technical Challenges Principles of Modern Wireless Communications Small-Scale Fading (Cont.) 59 Given sl(t) = 1, we have the received signal expressed as 2( )( ) ( )( )( ) c nn jftjt ln
4、n nn r ta t ea t e Notes: a) The received signal consists of the sum of a number of time-variant phasors. b) The phase n(t) = 2fcn(t) will change by 2 whenever n changes by 1/ fc. c) The signal can be modeled as a random process, i.e. a complex-valued Gaussian random process according to the central
5、 limit theorem. d) The signal fading, i.e. amplitude variations, may be destructive or constructive, which is primarily a result of the time variations in the n(t). Technical Challenges Principles of Modern Wireless Communications Power Delay Profile 60 Assume that h(;t) is wide-sense stationary, th
6、e autocorrelation of h(;t) is * 1212 112 1 ( ,;)( ; ) (;) 2 ( ;) () h h tE ht htt t Note the scattering at two different delays are uncorrelated. Let t = 0, the resulting autocorrelation function is h(; 0) h(), i.e. the average power output of the channel as a function of the time delay . h() is cal
7、led power delay profile. Generally speaking, h(; t) gives average power output of the channel as a function of and the difference t in observation time. Hence, the PDP may be time varying. Technical Challenges Principles of Modern Wireless Communications Time-varying impulse response 61 Technical Ch
8、allenges Principles of Modern Wireless Communications Measured impulse responses 62 Technical Challenges Principles of Modern Wireless Communications Frequency Selectivity of Channel 63 The FT of h(;t) with respect to (w.r.t.) yields the time-variant transfer function H(f;t) as 2 ( ; )( ; ) jf H f t
9、ht ed Since H(f;t) has the same statistics as h(;t), we have the autocorrelation function * 1212 1 (,;)(; )(;) 2 (;) H H fftE Hf t H f tt ft resulting from the uncorrelation of different rays. Technical Challenges Principles of Modern Wireless Communications Frequency Selectivity of Channel (Cont.)
10、64 For t = 0, H(f; 0) H(f), which can be derived from the FT of h() 2 ()( ) jf Hh fed which provides us with a measure of the frequency coherence of the channel. The coherence bandwidth of the channel is measured as max 1 c B where max denotes the multipath delay. If the bandwidth of the transmitted
11、 signal Bs Bc, the channel is frequency-selective. Otherwise, the channel is frequency-nonselective, i.e. flat fading. Technical Challenges Principles of Modern Wireless Communications Time Selectivity of Channel 65 The FT of H(f; t) w.r.t. t gives the function as 2 (; )(;)() jt HH Sfft edt If f = 0
12、, SH(f; ) SH(), which is the Doppler power spectrum given by 2 ( )(0;)() jt HH St edt The coherence time of the channel is related to the Doppler spread Fd as 1 c d T F Technical Challenges Principles of Modern Wireless Communications Time-Varying CFR 66 Technical Challenges Principles of Modern Wir
13、eless Communications Scattering Function Understand the variables (; f) as well as (t; ) The FT between H(f; t) and h(; t) The FT between H(f; t) and SH(f; ) A closed-loop relationship is obtained by defining a new function, i.e. the scattering function of the channel. 67 22 2 2 ( ; )(;)() () ( ;)()
14、 (; )() jtjf H jt h jf H Sft eedt df t edt Sfedf Technical Challenges Principles of Modern Wireless Communications Two Independent Fading Issues 68 Technical Challenges Principles of Modern Wireless Communications Time Dispersion (flat) 69 Technical Challenges Principles of Modern Wireless Communica
15、tions Time Dispersion (selec.) 70 Technical Challenges Principles of Modern Wireless Communications Doppler Shift Geomerty 71 From X Y, the phase difference 22 cos cc lv t The frequency variation is the Doppler shift 1 coscos 2 c d c vvf f tc Technical Challenges Principles of Modern Wireless Commun
16、ications Channel Statistics 72 For each resolvable path, the channel gain is considered as a sum of M components, of which the amplitude and the phase are random processes. 1 11 (cossin n M jt n n MM nnnn nn IQ u tut e uttjutt utjut If M 8, we consider R.V. , then u(t) follows Rayleigh distribution.
17、 2 ,(0,) IQ ututN 2 2 2 2 , 0 u u p ueu Technical Challenges Principles of Modern Wireless Communications Channel Statistics 73 In the presence of a LOS ray or a specularly reflected path, we have 00 1 2 2 (2) 0 ( ) c jff mmjm t e tt () IIQQ r tu tm t utmtj utmt Then, the envelope is Ricean distribu
18、tion. 22 0 2 0 2 2 0 2 r () r p r reI Technical Challenges Principles of Modern Wireless Communications Channel Statistics 74 RayleighRicean Technical Challenges Principles of Modern Wireless Communications Channel Statistics 75 2 00 ()(2) uum RtJft The correlation function of channel-response envel
19、ope 2 0 2 ( ),| 1() um m m Sfff f f f Then the Doppler power spectrum Other kinds of Doppler spectrum may be applied, like Gaussian spectrum in the COST207 TU channel model. Technical Challenges Principles of Modern Wireless Communications Channel Statistics 76 -100-80-60-40-20020406080100 0 0.01 0.
20、02 0.03 0.04 0.05 0.06 0.07 0.08 f/Hz S ii(f) 00.0050.010.0150.020.0250.030.0350.040.0450.05 -0.5 0 0.5 1 /s R ii() Auto-correlation functionDoppler spectrum Technical Challenges Principles of Modern Wireless Communications Modeling Wireless Channels Technical Challenges Principles of Modern Wireles
21、s Communications About Path Delay Propagation delay 2) Zero-pole filter shapes the Doppler power spectrum. Technical Challenges Principles of Modern Wireless Communications II. Frequency-Domain Shaping 86 Technical Challenges Principles of Modern Wireless Communications II. Frequency-Domain Shaping
22、High-efficiency IFFTs make fast fading simulator. Increasing spectral resolution requires large-size IFFT. Singular spectrum at fm necessitates high- resolution lines. Block-wise processing needs large-size storage. 87 Technical Challenges Principles of Modern Wireless Communications III. Method of
23、Sum-Of-Sinusoids (SOS) 88 Clarke Model: 1 2 ( )exp cos() N mnn n g tjt N Note the angle of arrival (AoA) n and the initial phase n are independent RVs, and n, n U-, ) . Jakes Model: 1) Simplify the AoA: n = 2n/N 2) Introduce phase relation between rays M = (N-2)/4 sinusoids Technical Challenges Prin
24、ciples of Modern Wireless Communications 89 Technical Challenges Principles of Modern Wireless Communications III. Method of Sum-Of-Sinusoids (SOS) 90 -100-50050100 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 Technical Challenges Principles of Modern Wireless Communications III. Method of Sum-Of-Sinusoids (SO
25、S) 91 00.511.522.53 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Amplitude Simulator of Jake Model r/ P(r) 2=0.5 theoretical N=8 N=16 N=34 Technical Challenges Principles of Modern Wireless Communications III. Method of Sum-Of-Sinusoids (SOS) 92 00.050.10.150.2 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 AutoC
26、orrelation of Jake Model /s Rx() theoretical N=8 N=24 N=50 Technical Challenges Principles of Modern Wireless Communications III. Method of Sum-Of-Sinusoids (SOS) Jakes model is a non-stationary process, resulting from the dependent initial phases. The modified Hoeher model adopts random frequencies
27、 and phases for each rays in one delay cluster. 93 , 1 , 1 , , 2 ( )cos(sin(/2) 2 ( )cos(sin(/2) ,(0,1 ,(, N ImI pI p p N QmQ qQ q q I pQ q I pQ q g ttu N gttu N uuU U Technical Challenges Principles of Modern Wireless Communications Simulation of Doubly Selective Channel 94 Technical Challenges Pri
28、nciples of Modern Wireless Communications Example 95 COST207 TU6 channel model 0123456 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Time delay ( s) Amplitude | h( )| -3-2-1012345678 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Time delay ( s) Amplitude | c( )| Technical Challenges Principles of Modern Wireless Communicat
29、ions 96 Technical Challenges Principles of Modern Wireless Communications 97 0 0.5 1 1.5 2 2.5 3 3.5 00.10.20.30.40.50.60.70.80.91 The average power of received samples Time (s) Carrier frequency 500MHz, Velocity 72km/h Technical Challenges Principles of Modern Wireless Communications Exercises Tech
30、nical Challenges Principles of Modern Wireless Communications Chapter 3 Digital Modulation and Demodulation 刘光辉 Technical Challenges Principles of Modern Wireless Communications 100 Contents: Digitally Modulated Signals Spectral Characteristics Optimum Receiver for AWGN Error-Probability Performance
31、 Exercises Technical Challenges Principles of Modern Wireless Communications Digitally Modulated Signals Technical Challenges Principles of Modern Wireless Communications Requirements of Digital Modulation Compact power density spectrum Narrow main lobe Fast roll-off of side-lobes Reliable communica
32、tion Measured by the received SINR Robust against channel impairments Envelope properties Power amplifier nonlinearities Constant envelope modulation is desired 102 Technical Challenges Principles of Modern Wireless Communications Bandpass Modulated Signal 103 Three expressions: 1) complex-envelope
33、form 2) Quadrature form 3) amplitude-phase form where Technical Challenges Principles of Modern Wireless Communications 104 where Technical Challenges Principles of Modern Wireless Communications Complex-envelope signal 105 For any digitally modulated signal, we have Note: 1) xn, complex data symbol
34、s, chosen from a finite alphabet 2) K, the modulation order 3) b(t, xn), the generalized shaping function Technical Challenges Principles of Modern Wireless Communications Pulse Shaping 106 Consider a popular modulation scheme Design the shaping function ha(t): 1) The matched filter at the receiver
35、side 2) The baud rate is 1/T 3) The condition of the ISI-free transmission 4) The frequency-domain design of the shaping function to meet the ISI-free condition 5) Two types of shaping functions: sinc function; root-raised cosine pulse Technical Challenges Principles of Modern Wireless Communication
36、s Root-Raised Cosine Pulse 107 Technical Challenges Principles of Modern Wireless Communications M-QAM Signal 108 The complex envelope of the transmitted waveform The transmitted waveform at each baud epoch Technical Challenges Principles of Modern Wireless Communications QAM Constellations 109 Tech
37、nical Challenges Principles of Modern Wireless Communications PAM Constellations 110 Technical Challenges Principles of Modern Wireless Communications PSK Signal 111 Technical Challenges Principles of Modern Wireless Communications OQPSK Signal 112 Technical Challenges Principles of Modern Wireless
38、Communications /4DQPSK Signal 113 Phase trajectories Technical Challenges Principles of Modern Wireless Communications Continuous Phase Modulation (CPM) 114 Technical Challenges Principles of Modern Wireless Communications Binary CPFSK 115 Phase trellis (linear excess phase trajectories) Technical C
39、hallenges Principles of Modern Wireless Communications Minimum Shift Keying (MSK) 116 Technical Challenges Principles of Modern Wireless Communications Spectral Characteristics Technical Challenges Principles of Modern Wireless Communications Bandpass to Baseband 118 Technical Challenges Principles
40、of Modern Wireless Communications PSD of Complex BB signal 119 PSD of stochastic process Autocorrelation function Complex-envelope of digitally modu. signal FFT Average over a sample period Technical Challenges Principles of Modern Wireless Communications PSD Simple Form 120 When the data symbols ar
41、e zero-mean stochastic process, whose samples are i.i.d. RVs, we have the simple form of the PSD Only depends on the shaping filter Technical Challenges Principles of Modern Wireless Communications PSD of QAM 121 PSK, OPSK, DPSK, and PAM Have the same form of PSD. Technical Challenges Principles of
42、Modern Wireless Communications PSD for MSK 122 Technical Challenges Principles of Modern Wireless Communications PSD of GMSK 123 Narrow main lobe Fast roll-off of side lobes Technical Challenges Principles of Modern Wireless Communications Spectral Efficiencies 124 Technical Challenges Principles of
43、 Modern Wireless Communications Optimum Receiver for AWGN Technical Challenges Principles of Modern Wireless Communications PSD for Bandpass Noise 126 Technical Challenges Principles of Modern Wireless Communications Assumptions for Optimum Receivers All transmit symbols are equally likely. The modu
44、lation format does not have memory. The channel is an AWGN channel, and both absolute channel gain and phase rotation are completely known. Without loss of generality, we assume henceforth that phase rotation has been compensated completely, so that the channel attenuation is real, so that = |. 127
45、Technical Challenges Principles of Modern Wireless Communications MAP & ML Detectors 128 The MAP detector with Bayes rules If all symbols are equiprobable, the MAP is identical to the ML detector: Technical Challenges Principles of Modern Wireless Communications Structure of Optimum Receiver 129 Tec
46、hnical Challenges Principles of Modern Wireless Communications Decision Boundary 130 Technical Challenges Principles of Modern Wireless Communications Union Bound for Symbol Error 131 Technical Challenges Principles of Modern Wireless Communications Optimum Receiver for Noncoherent Det 132 Technical
47、 Challenges Principles of Modern Wireless Communications Error-Probability Performance Technical Challenges Principles of Modern Wireless Communications Error Probability 134 For the binary orthogonal signals Technical Challenges Principles of Modern Wireless Communications Error Probability 135 Tec
48、hnical Challenges Principles of Modern Wireless Communications Error Probability 136 For the M-ary orthogonal signals Technical Challenges Principles of Modern Wireless Communications The M-ary PAM Signal 137 Technical Challenges Principles of Modern Wireless Communications The M-ary PSK Signal 138
49、Technical Challenges Principles of Modern Wireless Communications The BPSK & DBPSK Mod 139 Technical Challenges Principles of Modern Wireless Communications SER for the QAM Signals 140 Technical Challenges Principles of Modern Wireless Communications Comparison of Mod Methods 141 Technical Challenge
50、s Principles of Modern Wireless Communications Chapter 4 - I Frequency-Domain Signal Processing for Wireless Communications - Introduction to OFDM Guanghui Liu Technical Challenges Principles of Modern Wireless Communications 143 Contents What is OFDM? The History of OFDM Basics of OFDM Technical Ch
