*Article* **Semi-Supervised Adversarial Learning Using LSTM for Human Activity Recognition**

**Sung-Hyun Yang, Dong-Gwon Baek and Keshav Thapa \***

> Department of Electronic Engineering, Kwangwoon University, Seoul 01897, Korea; shyang@kw.ac.kr (S.-H.Y.); whitedk@kw.ac.kr (D.-G.B.)

**\*** Correspondence: kshavthapa@kw.ac.kr

**Abstract:** The training of Human Activity Recognition (HAR) models requires a substantial amount of labeled data. Unfortunately, despite being trained on enormous datasets, most current models have poor performance rates when evaluated against anonymous data from new users. Furthermore, due to the limits and problems of working with human users, capturing adequate data for each new user is not feasible. This paper presents semi-supervised adversarial learning using the LSTM (Long-short term memory) approach for human activity recognition. This proposed method trains annotated and unannotated data (anonymous data) by adapting the semi-supervised learning paradigms on which adversarial learning capitalizes to improve the learning capabilities in dealing with errors that appear in the process. Moreover, it adapts to the change in human activity routine and new activities, i.e., it does not require prior understanding and historical information. Simultaneously, this method is designed as a temporal interactive model instantiation and shows the capacity to estimate heteroscedastic uncertainty owing to inherent data ambiguity. Our methodology also benefits from multiple parallel input sequential data predicting an output exploiting the synchronized LSTM. The proposed method proved to be the best state-of-the-art method with more than 98% accuracy in implementation utilizing the publicly available datasets collected from the smart home environment facilitated with heterogeneous sensors. This technique is a novel approach for high-level human activity recognition and is likely to be a broad application prospect for HAR.

**Keywords:** HAR; semi-supervised learning; adversarial learning; syn-LSTM; smart home
