Sarkar, Abhishek
Machine Learning (ML)-assisted Beam Management in millimeter (mm)Wave Distributed Multiple Input Multiple Output (D-MIMO) systems
M, Karthik R, Hegde, Dhiraj Nagaraja, Sarajlic, Muris, Sarkar, Abhishek
Beam management (BM) protocols are critical for establishing and maintaining connectivity between network radio nodes and User Equipments (UEs). In Distributed Multiple Input Multiple Output systems (D-MIMO), a number of access points (APs), coordinated by a central processing unit (CPU), serves a number of UEs. At mmWave frequencies, the problem of finding the best AP and beam to serve the UEs is challenging due to a large number of beams that need to be sounded with Downlink (DL) reference signals. The objective of this paper is to investigate whether the best AP/beam can be reliably inferred from sounding only a small subset of beams and leveraging AI/ML for inference of best beam/AP. We use Random Forest (RF), MissForest (MF) and conditional Generative Adversarial Networks (c-GAN) for demonstrating the performance benefits of inference.
LogAnMeta: Log Anomaly Detection Using Meta Learning
Sarkar, Abhishek, Sen, Tanmay, Kundu, Srimanta, Sarkar, Arijit, Wazed, Abdul
Modern telecom systems are monitored with performance and system logs from multiple application layers and components. Detecting anomalous events from these logs is key to identify security breaches, resource over-utilization, critical/fatal errors, etc. Current supervised log anomaly detection frameworks tend to perform poorly on new types or signatures of anomalies with few or unseen samples in the training data. In this work, we propose a meta-learning-based log anomaly detection framework (LogAnMeta) for detecting anomalies from sequence of log events with few samples. LoganMeta train a hybrid few-shot classifier in an episodic manner. The experimental results demonstrate the efficacy of our proposed method
Non-negative matrix factorization algorithms greatly improve topic model fits
Carbonetto, Peter, Sarkar, Abhishek, Wang, Zihao, Stephens, Matthew
We report on the potential for using algorithms for non-negative matrix factorization (NMF) to improve parameter estimation in topic models. While several papers have studied connections between NMF and topic models, none have suggested leveraging these connections to develop new algorithms for fitting topic models. Importantly, NMF avoids the "sum-to-one" constraints on the topic model parameters, resulting in an optimization problem with simpler structure and more efficient computations. Building on recent advances in optimization algorithms for NMF, we show that first solving the NMF problem then recovering the topic model fit can produce remarkably better fits, and in less time, than standard algorithms for topic models. While we focus primarily on maximum likelihood estimation, we show that this approach also has the potential to improve variational inference for topic models. Our methods are implemented in the R package fastTopics.
Causal Mediation Analysis Leveraging Multiple Types of Summary Statistics Data
Park, Yongjin, Sarkar, Abhishek, Nguyen, Khoi, Kellis, Manolis
Genome-wide association studies (GWAS) identify statistically significantcorrelations between genetic and phenotypic variables. In the era of Biobank GWAS, phenotypes can be virtually any variables measurable across millions of individuals in the database, of which examples includediagnosis codes, routine laboratory test results, familyhistory of complex disorders, and even socioeconomical status. Significant signals of well-executed GWAS implicate unidirectional causal relationship from the tagged genomic variants to phenotypes, not the other way. In biological information cascade, using GWAS, we can establish links between the very first (genetics) and the last (phenotypes) layers,and we normally expect the effect sizes are typically minuscule; and necessary statistical significance can be achieved in studies involving at least hundreds of thousands of individuals. Nonetheless, a large number of GWAS summary statistics data are already made publicly available.Geneticists have already uncovered more than 24k unique associations between single nucleotide polymorphism (SNP) markers and complex phenotypes [16].
DiGrad: Multi-Task Reinforcement Learning with Shared Actions
Dewangan, Parijat, Phaniteja, S, Krishna, K Madhava, Sarkar, Abhishek, Ravindran, Balaraman
Most reinforcement learning algorithms are inefficient for learning multiple tasks in complex robotic systems, where different tasks share a set of actions. In such environments a compound policy may be learnt with shared neural network parameters, which performs multiple tasks concurrently. However such compound policy may get biased towards a task or the gradients from different tasks negate each other, making the learning unstable and sometimes less data efficient. In this paper, we propose a new approach for simultaneous training of multiple tasks sharing a set of common actions in continuous action spaces, which we call as DiGrad (Differential Policy Gradient). The proposed framework is based on differential policy gradients and can accommodate multi-task learning in a single actor-critic network. We also propose a simple heuristic in the differential policy gradient update to further improve the learning. The proposed architecture was tested on 8 link planar manipulator and 27 degrees of freedom(DoF) Humanoid for learning multi-goal reachability tasks for 3 and 2 end effectors respectively. We show that our approach supports efficient multi-task learning in complex robotic systems, outperforming related methods in continuous action spaces.