We introduce a learning-based approach to optimize a joint constellation for a multi-user MIMO broadcast channel ($T$ Tx antennas, $K$ users, each with $R$ Rx antennas), with perfect channel knowledge. The aim of the optimizer (MAX-MIN) is to maximize the minimum mutual information between the transmitter and each receiver, under a sum-power constraint. The proposed optimization method do neither impose the transmitter to use superposition coding (SC) or any other linear precoding, nor to use successive interference cancellation (SIC) at the receiver. Instead, the approach designs a joint constellation, optimized such that its projection into the subspace of each receiver $k$, maximizes the minimum mutual information $I(W_k;Y_k)$ between each transmitted binary input $W_k$ and the output signal at the intended receiver $Y_k$. The rates obtained by our method are compared to those achieved with linear precoders.

This study introduces a novel approach for learning mixtures of Markov chains, a critical process applicable to various fields, including healthcare and the analysis of web users. Existing research has identified a clear divide in methodologies for learning mixtures of discrete and continuous-time Markov chains, while the latter presents additional complexities for recovery accuracy and efficiency. We introduce a unifying strategy for learning mixtures of discrete and continuous-time Markov chains, focusing on hitting times, which are well defined for both types. Specifically, we design a reconstruction algorithm that outputs a mixture which accurately reflects the estimated hitting times and demonstrates resilience to noise. We introduce an efficient gradient-descent approach, specifically tailored to manage the computational complexity and non-symmetric characteristics inherent in the calculation of hitting time derivatives. Our approach is also of significant interest when applied to a single Markov chain, thus extending the methodologies previously established by Hoskins et al. and Wittmann et al. We complement our theoretical work with experiments conducted on synthetic and real-world datasets, providing a comprehensive evaluation of our methodology.

A common approach for handling the complexity and inherent ambiguities of 3D human pose estimation is to use pose priors learned from training data. Existing approaches however, are either too simplistic (linear), too complex to learn, or can only learn latent spaces from "simple data", i.e., single activities such as walking or running. In this paper, we present an efficient stochastic gradient descent algorithm that is able to learn probabilistic non-linear latent spaces composed of multiple activities. Furthermore, we derive an incremental algorithm for the online setting which can update the latent space without extensive relearning. We demonstrate the effectiveness of our approach on the task of monocular and multi-view tracking and show that our approach outperforms the state-of-the-art.

Often these techniques are sequential in that the measurements are taken one after another. Hence information gained in the past can be used to guide an adaptive design of subsequent measurements, which naturally leads to the notion of sequential adaptive sensing. At the same time, a path to efficient sensing of big data is compressive sensing [4]-[6], which exploits low-dimensional structures to recover signals from a number of measurements much smaller than the ambient dimension of the signals. Early compressed sensing works mainly focus on nonadaptive and one-shot measurement schemes. Recently there has also been much interest in sequential adaptive compressed sensing, which measures noisy linear combinations of the entries (this is different from the direct adaptive sensing, which measures signal entries directly [7]-[10]). Although in the seminal work of [11], it was shown under fairly general assumptions that "adaptivity does not help much", i.e., sequential adaptive compressed sensing does not improve the order of the min-max bounds obtained by algorithms, these limitations are restricted to certain performance metrics. It has also been recognized (see, e.g., [12]-[14]) that adaptive compressed sensing offers several benefits with respect to other performance metrics, such as the reduction in the signalto-noise ratio (SNR) to recover the signal.