1. 1 EMLAB Wireless propagations

2. 2 EMLAB channel RF DSP 데이터 송신 RF DSP 수신 데이터 1. Wireless channel model 무선 통신 기기 사이의 전파 송수신 예측 어려움. 단말기 설계를 위해 channel 특성 파악 필요.

3. 3 EMLAB 근사 모델 #1: Free space model (Friis formula) 거리 감쇄 효과만 고려. 초기 설계에 유용.

4. 4 EMLAB Antenna modeling 안테나에서 나온 신호 는 거리 R 떨어진 지점 에서 진폭이 1/R 로 줄 어들고 시간 지연이 R/c 만큼 생긴다.

5. 5 EMLAB Field test route (outdoor) Guidelines for drive testing to accurately estimate average cell radius or for tuning a path loss model.

6. 6 EMLAB Field test route (indoor) Typical in-building measurement route and signal strength.

7. 7 EMLAB Measured path loss

8. 8 EMLAB Physical model Impulse response Time Measurement Simplified model

9. 9 EMLAB Propagation channel model Impulse response Time Spectrum Frequency Amplitude variation time spread Mathematical model α i (t), τ i (t) 가 channel 특성 결정.

10. 10 EMLAB Hierarchical fading process : statistical model

11. 11 EMLAB Propagation loss mechanisms : scaled model 1.Large Scale Fading: due to distance 2. Medium Scale Fading: shadowing and obstacles 3. Small Scale Fading : due to multipath

12. 12 EMLAB The three scales of mobile signal variation

13. 13 EMLAB (1) Large scale fading ( 거리와 path loss 를 fitting 하여 β 값을 찾음.)

14. 14 EMLAB 근사 모델 #2 : Two-ray Ground Reflection

15. 15 EMLAB Measure PL(d 0 ) or calculate Free Space Path Loss. Take measurements and derive  empirically. 근사 모델 #3 : Log-Distance Model EnvironmentExponent (β) Free space2 Urban area2.7~3.5 Shadowed urban area3~5 Indoor LOS1.6~1.8 Indoor non-LOS4~6

16. 16 EMLAB Classification of large scale propagation models 1.Macro cell model ① Empirical model a.Log-distance path loss b.Okumura-Hata ② Physical model a.COST231/Walfisch-Ikegami Model ③ ITU-R model 2. Micro cell model ① Empirical model a.Dual slope model ② Physical model a.Two-ray model b.Street canyon model c.Random waveguide model d.Ray tracing model ③ ITU-R model 3. Pico cell model ① Empirical model ② Physical model

17. 17 EMLAB Okumura-Hata model (COST207) 1.150MHz~1.5GHz 에서 유용. 2. 측정을 통해 얻은 데이터임. 3.Open area, Suburban area, Urban area 로 분류함. For large cities For medium to small cities Urban areas : Suburban areas : Open areas :

18. 18 EMLAB COST231-Hata model 1.1.5GHz~2GHz 로 Hata 모델 확장 2. 측정을 통해 얻은 데이터임. 3.Open area, Suburban area, Urban area 로 분류함.

19. 19 EMLAB Walfisch-Ikegami Propagation Model L f : free space loss L msd :multiple knife edge diffraction L sd : single diffraction

20. 20 EMLAB (2) Medium scale model : shadowing

21. 21 EMLAB Typical variation of shadowing with mobile position at fixed BS distance Probability density function of shadowing. Measured values are produced by subtracting the empirical model. Log-normal distribution : shadowing

22. 22 EMLAB Shadowing effect on coverage

23. 23 EMLAB (3) Small scale fading Probability density function of real part of NLOS fading signal→ Gaussian Multi-path fading : NLOS

24. 24 EMLAB Equal delay ellipse : multi-path fading

25. 25 EMLAB Complex samples of NLOS fading signal Theoretical and experimental Rayleigh distributions Rayleigh fading

26. 26 EMLAB Rician fading Rice factor :

27. 27 EMLAB 동일한 전자기 현상이지만 관찰 자의 상대적 운동에 의해 E, H, k, 주파수 등이 변한다 Frequency shift by Doppler effect

28. 28 EMLAB Beat frequency due to Doppler effect 다중 경로 신호의 주파수가 달라져 beat frequency 관찰됨.

29. 29 EMLAB The received signal of a time varying channel where the transmitted signal is a time-harmonic signal with frequency f =10Hz. Time varying channel – Doppler shift

30. 30 EMLAB Time varying channel : auto-correlation Power spectral density ( f D : maximum Doppler frequency.) Jakes model For time delay profile Coherence time :

31. 31 EMLAB Wideband fast fading

32. 32 EMLAB Multi-path Fading Impulse response Time Flat fading : low data rate. Ex) AMPS, ASK,... Time Impulse response Frequency selective fading : high data rate 인 경우에 생김. Ex) WCDMA, DMB 등... Inter-symbol interference Symbol Time

33. 33 EMLAB Multi-path Fading Multi-path Fading 의 영향 협대역 신호인 경우 영향이 작다. 광대역 신호인 경우 신호 spectrum 에 미치는 영향이 크다.

34. 34 EMLAB …shift in time … …shift in frequency … … attenuation… (this causes small scale time variations) paths Wide-band fast fading channel model

35. 35 EMLAB Channel sounding Coherent B. W. :

36. 36 EMLAB Overcoming narrow band fading Diversity

37. 37 EMLAB Overcoming wide band fading Linear equalizer

38. 38 EMLAB Adaptive equalizer

39. 39 EMLAB OFDM receivers OFDM Subcarriers in the Frequency Domain

40. 40 EMLAB... 각도 추정... RF, modem 다중 빔 안테나 각도 추정 알고리즘다중 빔 생성 Adaptive antenna