Sparse and Redundant Representations and Their Applications in Signal and Image Processing (236862) Section 4: MAP vs. MMSE Estimation Winter Semester, 2018/2019 Michael (Miki) Elad
Meeting Plan Quick review of the material covered Answering questions from the students and getting their feedback Discussing a new material – MMSE Estimation via the Stochastic Resonance Concept – Given by Dror Simon Administrative issues
Overview of the Material Sparseland: An Estimation Point of View A Strange Experiment A Crash-Course on Estimation Theory Sparseland: Approximate Estimation MMSE: Back to Reality
Your Questions and Feedback Answer: MAP Estimation and the Relation to OMP: In the slides we derive the MAP estimation and get a strange looking expression, and yet we claim that OMP approximates it. We did see that for |s|=1 the two align, but is there a clearer view of the connection between the estimation approach and the OMP or the pursuit we saw so many times in this course? Answer: Let’s Try … Here is an attempt to clarify this connection. It will be obtained by deriving the MAP little bit differently, and by relying on different assumptions
Your Questions and Feedback Lets define our estimation goal: In this step we add the support as an unknown, so that we search for the most probable representation and its support TOGETHER Using Bayes rule we obtain:
Your Questions and Feedback Returning to our MAP goal:
Your Questions and Feedback So, this is what we just got: Suppose that this is our probability Elastic Net This leads to: which is the P0 we kept advocating, with a twist
Your Questions and Feedback
New Material? MMSE Estimation: Another Point of View We are hooked to the idea that noise is … noise, i.e. an annoying disturbance to be avoided For example, consider the previous chapter about denoising … Could noise be helpful in engineering processes? Are you aware of cases in which noise (or randomness) is beneficial? Observe that the RandOMP described in this chapter used randomness to achieve its MMSE estimation How could we offer a parallel to the RandOMP that is BP-based? This brings us to Dror Simon’s presentation on Stochastic Resonance
Administrative Issues Lets talk about the following: Your feedback is very much needed in the Technion’s course 236862 (MISHAAL HAMARTZE) & (+ free text comments) Are there questions about the final project?