1 / 37

41st IEEE CDC Las Vegas, Nevada December 9th 2002

41st IEEE CDC Las Vegas, Nevada December 9th 2002. Workshop M-5: Wireless Communication Channels: Modeling, Analysis, Simulations and Applications. Organizers: Charalambos D. Charalambous Nickie Menemenlis. Wireless Communication Channels. Schedule

judd
Download Presentation

41st IEEE CDC Las Vegas, Nevada December 9th 2002

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. 41st IEEE CDC Las Vegas, Nevada December 9th 2002 Workshop M-5: Wireless Communication Channels: Modeling, Analysis, Simulations and Applications Organizers: Charalambos D. Charalambous Nickie Menemenlis

  2. Wireless Communication Channels Schedule • 08:00-08:45 Introduction to Wireless Communication Channels (C.D. Charalambous) • 8:45-9:15 Statistical Analysis of Wireless Fading Channels (C.D. Charalambous) • 9:15-9:25 Break • 9:25 -10:10 Stochastic Differential Equations in Modeling Log-Normal Shadowing (N. Menemenlis) • 10:10-10:55 Stochastic Differential Equations in Modeling Short-Term Fading (N. Menemenlis) • 10:55-11:00 Break • 11:00-12:00 Applications (C.D. Charalambous) • Additional information can be found at: • http://www.site.uottawa.ca/~chadcha/CDC2002

  3. Introduction to Wireless Communication Channels • Shannon’s communication channel • Impulse response of wireless fading channels • Large-scale and small scale propagation models • Log-Normal shadowing channel • Short-term fading channel • Autocorrelation functions and power spectral densities • Assumption: WSSUS • Time spreading • Time variations • Channel classification • Channel simulations

  4. Chapter 1: Shannon’s Wireless Communication System Channel code word Message Signal Modulated Transmitted Signal Source Source Encoder Channel Encoder Mod- ulator Wireless Channel User Source Decoder Channel Decoder Demod- ulator Received Signal Estimate of Message signal Estimate of channel code word

  5. Chapter 1: Large and Small Scale Propagation Models Area 1 Area 2 Short-term fading Log-normal shadowing Transmitter

  6. Chapter 1: Impulse Response Characterization Time variations property t2 t(t2) t1 t(t1) Time spreading property t0 t(t0) • Impulse response: Time-spreading : multipath • and time-variations: time-varying environment

  7. Chapter 1: Multipath Fading Components • Complex low-pass representation of impulse response

  8. Chapter 1: Band-pass Representation of Impulse Response • Band-pass representation of impulse response:

  9. Chapter 1: Representation of Additive Noise Channel • Low-pass and band-pass representation of received signal:

  10. Chapter 1: Large and Small Scale Propagation Models • Large scale propagation models: • T-R separation distances are large • Main propagation mechanism: reflections • Attenuation of signal strength due to power loss along distance traveled: shadowing • Distribution of power loss in dBs: Log-Normal • Log-Normal shadowing model • Fluctuations around a slowly • varying mean

  11. Chapter 1: Large and Small Scale Propagation Models • Small scale propagation: • T-R separation distances are small • Heavily populated, urban areas • Main propagation mechanism: scattering • Multiple copies of transmitted signal arriving at the transmitted via different paths and at different time-delays, add vectotrially at the receiver: fading • Distribution of signal attenuation • coefficient: Rayleigh, Ricean. • Short-term fading model • Rapid and severe signal • fluctuations around a slowly • varying mean

  12. Chapter 1: Log-Normal Shadowing Model

  13. Chapter 1: Log-Normal Shadowing Model

  14. Chapter 1: Log-Normal Shadowing Model • Power path-loss in dB’s, x, and Distributions: x : normal and attenuation coefficient, r, vs d r=ekx : log-normal

  15. Chapter 1: Short-Term Fading Model z z0 nth incoming wave En=:{rn,fn,an,bn}; n=1,…, N O’(x0 ,y0 ,z0) bn O an x x0 y0 g O’’ v y direction of motion of mobile on x-y plane • 3-Dimensional Model [Clarke 68, Aulin 79]

  16. Chapter 1: Short-Term Fading Model • 3-D Model [Clarke 68, Aulin 79] • Transmitted signal: Re{ejwct} • Total field at mobile, or receiving location, O’(x0, y0, z0)

  17. Chapter 1: Short-Term Fading Model • 3-D Model [Clarke 68, Aulin 79] • Total field at receiving location when mobile moves • O’(x0, y0, z0) => (x0+vtcosg, y0 +vtsing, z0), v: velocity of mobile

  18. Chapter 1: Short-Term Fading Model • 3-D Model [Clarke 68, Aulin 79] • Statistical characterization of {I(t), Q(t)}

  19. Chapter 1: Short-Term Fading Model • Statistical characterization of rn

  20. Chapter 1: Short-Term Fading Model • Autocorrelation functions

  21. Chapter 1: Short-Term Fading Model

  22. Chapter 1: Time Delays of Paths • Complex low-pass representation of impulse response: • Typically the time delays are modeled using exponential distribution, implying that the number of paths is a Poisson counting process • In reality this representation is not very accurate.

  23. Chapter 1: Channel Autocorrelation Functions • General expressions for the Autocorrelation function are introduced by Bello ’63 for a widely accepted Wide-Sense Stationary Uncorrelated Scattering (WSSUS) channel • WSS in the time-domain • US attenuation and phase shift of paths i and j are uncorrelated

  24. Chapter 1: Channel Autocorrelation Functions • Time-spreading: Multipath characteristics of channel

  25. Chapter 1: Channel Autocorrelation Functions • Time-spreading: Multipath characteristics of channel

  26. Chapter 1: Channel Autocorrelation Functions • Time-spreading: Multipath characteristics of channel • Multi-path delay spread, Tm • Characterizes time dispersiveness of the channel, • Obtained from power delay-profile, Fc(t) • Indicates delay during which the power of the received signal is above a certain value. • Coherence bandwidth, Bcapprox. 1/ Tm • Indicates frequencies over which the channel can be considered flat • Two sinusoids separated by more than Bc: affected differently by the channel • Indicates frequency selectivity during transmission.

  27. Chapter 1: Channel Autocorrelation Functions • Time variations of channel: Frequency-spreading

  28. Chapter 1: Channel Autocorrelation Functions • Time variations of channel: Frequency-spreading

  29. Chapter 1: Channel Autocorrelation Functions • Time variations of channel: Frequency-spreading • Doppler Spread, Bd • Characterizes frequency dispersiveness of the channel, or the spreading of transmitted frequency due to different Doppler shifts • Obtained from Doppler spectrum, Sc(l) • Indicates range of frequencies over which the received Doppler spectrum is above a certain value • Coherence time, Tcapprox. 1/ Bd • Time over which the channel is time-invariant • A large coherence time: Channel changes slowly

  30. Chapter 1: Channel Autocorrelation Functions Fc(t ) Power Delay Profile |Fc(Df)| t Tm Ft Bc Df Dt=0 Power Delay Spectrum Fc( Dt;t ) Ft FDt |Fc(Dt;Df)| Dt=0 Scattering Function Df WSSUS Channel Sc( l;t ) Dt Sc(l; Df) Ft FDt Df=0 Df=0 Sc(l;t) |Fc(Dt)| Sc( l ) t Doppler Power Spectrum Tc Dt FDt l Bd l

  31. Chapter 1: Channel Classification Based on Time-Spreading • Flat Fading • BS < BCTm < Ts • Rayleigh, Ricean distrib. • Spectral chara. of transmitted • signal preserved • Frequency Selective • BS > BC Tm > Ts • Intersymbol Interference • Spectral chara. of transmitted • signal not preserved • Multipath components resolved Channel Channel Signal Signal BC BS freq. freq. BS BC

  32. Chapter 1: Channel Classification Based on Time-Variations • Fast Fading • High Doppler Spread • 1/Bd@ TC < Ts • Slow Fading • Low Doppler Spread • 1/Bd@ TC> Ts Signal Signal Doppler Doppler BD BS freq. freq. BS BD

  33. Chapter 1: Channel Classification • Underspread channel: TmBd << 1 • Channel characteristics vary slowly (Bd small) or paths obtained within a short interval of time (Tm small). • Easy to extract channel parameters. • Overspread channel: TmBd >> 1 • Hard to extract parameters as channel characteristics vary fast and channel changes before all paths can be obtained.

  34. Chapter 1: Flat Fading Channel Simulations • Flat Fading • a(t): Rayleigh or Ricean

  35. Chapter 1: Frequency Selective Channel Simulations • Frequency Selective

  36. Chapter 1: References • G.L. Turin. Communication through noisy, random-multipath channels. IRE Convention Record, pp. 154-166, 1956. • P. Bello. Characterization of random time-variant linear channels. IEEE Transactions in Communications, pp 360-393, 1963. • J.F. Ossanna. A model for mobile radio fading due to building reflections: Theoretical and experimental waveform power spectra. Bell Systems Technical Journal, 43:2935-2971, 1964. • R.H. Clarke. A statistical theory of mobile radio reception. Bell Systems Technical Journal, 47:957-1000, 1968. • M.J Gans. A power-spectral theory of propagation in the mobile-radio environment. IEEE Transactions on Vehicular Technology, VT-21(1):27-38, 1972. • H. Suzuki. A statistical model for urban radio propagation. IEEE Transactions in Communications, 25:673-680, 1977. • T. Aulin. A modified model for the fading signal at a mobile radio channel. IEEE Transactions on Vehicular Technology, VT-28(3):182-203, 1979. • A.D.Saleh, R.A.Valenzuela. A statistical model for indoor multi-path propagation. IEEE Journal on Selected Areas in Communications, 5(2):128-137, 1987.

  37. Chapter 1: References • M. Gudamson. Correlation model for shadow fading in mobile radio systems. Electronics Letters, 27(23):2145-2146, 1991. • D. Giancristofaro. Correlation model for shadow fading in mobile radio channels. Electronics Letters, 32(11):956-958, 1996. • A.J. Coulson, G. Williamson, R.G. Vaughan. A statistical basis for log-normal shadowing effects in multipath fading channels. IEEE Transactions in Communications, 46(4):494-502, 1998. • E. Biglieri, J. Proakis, S. Shamai. Fading channels: Information-theoretic and communication aspects. IEEE Transactions on Information Theory, 44(6):2619-2692, October 1998. • W.C.Jakes. Microwave mobile communications, New York, Wiley-Interscience, 1974. • K. Pahlavan, A.H. Levesque. Wireless Information Networks, New York, Wiley-Interscience, 1995. • J.G. Proakis. Digital Communications, Mc-Graw-Hill, New-York, 1995. • T.S. Rappaport. Wireless Communications, Prentice Hall, 1996.

More Related