UWB_Lecture04_v2 - 1 1 Ultrawideband systems: Fundamentals...

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Unformatted text preview: 1 1 Ultrawideband systems: Fundamentals and Standardization Lecture 4 Min-Kuan Chang National Chung Hsing University 教育部通訊教改計畫 教育部通訊教改計畫 2 Outline • Introduction • Simplified UWB multipath channel model • Path loss model • Two-ray UWB propagation model • Modified Saleh-Valenzuela (SV) model 2 3 Introduction • To implement UWB system in realistic world, two things have to be taken care of – Modeling the channel – Understanding the propagation effects Help to understand the performance of UWB systems in real world! Help to understand the performance of UWB systems in real world! ! 4 Introduction • Typical UWB propagation channel is based on the geometry of the environment – The rough knowledge of surroundings is needed – Deterministic channel model • Stochastic channel model – No particular assumption is made – Modeling a random process 3 5 Introduction • The main difference between UWB and traditional channel modeling techniques – Frequency-dependent effects should be included – The wide span of UWB in frequency domain – Reflection, path loss, penetration, and so on should be considered frequency-variant 6 Introduction • Example – Effect of propagation channel model on RAKE receiver 1 t 2 t 3 t time 4 7 Introduction Propagation scenario LOS and NLOS impulse responses Transmitter Receiver NLOS channel Individual path impulse responses LOS channel 10 20 30 B=7.5 GHz B=7.5 GHz 8 Introduction Example of a power delay profile Observed effects • Exponential time decay of power • Strong rays • Clusters of rays, composing path impulse responses • Exponential time decay of ray energy frequency band 1 - 11 GHz Source: ACORDE & Univ. of Cantabaria 5 9 Introduction Lognormal Depends on TR- distance and number of reflections Cluster magnitude Poisson process with arrival rate < 0.5 ns-1 Depends on transmitter, receiver,reflecto r positions Cluster arrival time Clusters of rays Indepent Rayleigh with uniform phase Discrete time equidistant (Nyquist rate) Discussed path loss model Independent lognormal Poisson process with arrival rate <3 ns-1 Exponential: decay constant 1.6 - 13 ns Ray amplitude distribution Time decay of ray power Ray arrival times Path loss Individual rays within clusters Overview on the modeling of different channel properties 10 Simplified UWB multipath channel model 6 11 Simplified UWB multipath channel model • Discrete time, multipath, impulse response model – Same as traditional multipath model – Locations of ceilings, walls, doors and etc. in indoor environment result in multipath reception of the transmitted signal – Mathematical representation ( ) ( ) ∑ − = − = 1 L m T t t h A A A δ α Amplitude attenuation factor The minimum resolution time Multipath intensity profile Multipath intensity profile 12 Simplified UWB multipath channel model • Primary parameters to characterize the indoor channel – Number of resolvable multipath component...
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This note was uploaded on 09/27/2010 for the course UWB 164 taught by Professor Minkuan during the Fall '01 term at National Cheng Kung University.

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UWB_Lecture04_v2 - 1 1 Ultrawideband systems: Fundamentals...

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