Lecture3 - E4703 Wireless Communications Lecture 3 Outline...

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E4703 Wireless Communications Lecture 3
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Outline Summary of last lecture. Signal representation: bandpass and lowpass. Stochastic processes. Statistical small-scale model: ¾ Multipath statistical model. ¾ Doppler spread and coherence time. ¾ Delay spread. Narrowband channels. ¾ Mean and autocorrelation. ¾ Power spectral density. ¾ Clarke-Jakes uniform scattering environment. ¾ Amplitude and power distributions: Rayleigh, Rician and Nakagami.
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Wideband channels. ¾ Power delay profile. ¾ Coherence bandwidth Depolarization.
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Summary of Lecture 2 Radiation pattern and gain characterize ability to concentrate power in certain directions in detriment of others. Polarization determines orientation of the fields composing the electromagnetic wave. Exact Maxwell equations unsolvable. Approximate (e.g. ray tracing) methods available for controlled environments (indoor). Accuracy entails complexity. More generally, resort to statistical modeling. Regard channel as stochastic. Distinguish between large- scale and small-scale features. Large-scale features: path loss (deterministic) and shadow fading (stochastic).
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Variety of path loss models: LOS, 2-ray, empirical, simplified. Power falloff with d 2 in free space, d 4 in two path model evidencing crucial role of ground. Appealing simple model P r = P t K [ d 0 / d ] γ Random attenuation due to shadowing modeled as log- normal (empirical std). Shadow fading decorrelates over decorrelation distance roughly the size of obstacles. Combined path loss and shadow fading leads to outage probabilities and amoeba-like cell shapes. Cell outage area dictates average % of locations in outage. Cell coverage indicates average % of locations not in outage.
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Announcements Location for TA office hours changed to 8 th floor lounge of the Schapiro building. Need to repeat questions for benefit of CVN students. Please remind.
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