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Christopher Hansen

Christopher Hansen, Ph.D. is a Silicon Valley consultant in wireless communications and signal processing. He has 25 years of experience including design of Wi-Fi/IEEE 802.11 physical layers, international standards, and intellectual property. He has held technical positions at Apple, Broadcom, and AT&T Bell Laboratories. He holds a Ph.D. in electrical engineering from UCLA.

How to Design Nonlinear Approximations for DSP

Status: Not yet available - Stay tuned!

Nonlinear functions, such as arctangent, logarithm, and square root are commonly used in Digital Signal Processing. In practice, a textbook approximation algorithm is often used to compute these functions. These approximations are typically of mysterious origin and optimized for a certain application or implementation. Consequently, they may not be ideal for the application at hand. This talk describes a method for designing approximations using Chebfun (www.chebfun.org), an open-source software system for numerical computation with functions. With Chebfun, it is possible to quickly determine polynomial and rational approximations for any function with as many interpolation points as needed. This talk will cover a few basic topics in approximation theory and then work through several practical examples that can be directly employed in fixed point and floating point DSP applications.

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802.11/Wi-Fi Channel Estimation

Status: Available Now

This talk presents an overview of channel estimation theory and techniques for IEEE 802.11 / Wi-Fi systems. It includes a review of the 802.11 preamble formats, estimation of SISO and MIMO channels, and a discussion of how channel estimates are used in demodulation and decoding. It concludes with recent results in semi-blind channel estimation for 802.11.

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