Presentation on theme: "EE359 – Lecture 10 Outline Announcements: Project proposals due this Friday at 5pm (post, email link) Midterm will be Nov. 7, 6-8pm, Room TBD, no HW due."— Presentation transcript:
EE359 – Lecture 10 Outline Announcements: Project proposals due this Friday at 5pm (post, email link) Midterm will be Nov. 7, 6-8pm, Room TBD, no HW due that week. Exam is open book/notes. More MT announcements next week (practice MTs) Example of P_out Average P s (P b ) MGF approach for average P s Combined average and outage P s
Review of Last Lecture Linear modulation more spectrally efficient but less robust than nonlinear modulation P s approximation in AWGN: Probability of error in fading is random Characterized by outage, average Ps, combination Outage probability Probability P s is above target; Probability s below target Fading severely degrades performance PsPs P s(target) Outage TsTs t or d Used when T c >>T s
Average P s Expected value of random variable P s Used when T c ~T s Error probability much higher than in AWGN alone Alternate Q function approach: Simplifies calculations (Get a Laplace Xfm) PsPs PsPs TsTs t or d
Combined outage and average P s Used in combined shadowing and flat-fading P s varies slowly, locally determined by flat fading Declare outage when P s above target value Ps(s)Ps(s) P s target Ps(s)Ps(s) Ps(s)Ps(s) Outage
Main Points In fading P s is a random variable, characterized by average value, outage, or combined outage/average Fading greatly increases average P s or required power for a given target P s with some outage Alternate Q function approach simplifies P s calculation, especially its average value in fading Average P s becomes a Laplace transform. In fast/slow fading, outage due to shadowing, probability of error averaged over fast fading pdf Need to combat flat fading or waste lots of power Adaptive modulation and diversity are main techniques to combat flat fading: adapt to fading or remove it
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