Publications

2025

1. IMWUT

   

   Enabling Older Adults to Provide High-quality Activity Labels: Unpacking Accuracy, Precision, and Granularity in Activity Labeling

   Yiwen Wang, Hossein Khayami, Bongshin Lee, Amanda Lazar, Hernisa Kacorri, and 1 more author

   Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, Dec 2025

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   High-quality labels of activity data with broad representations and real-world variability are key to developing activity recognition models tailored to the needs and characteristics of older adults. However, labeling real-world data presents significant challenges, placing a heavy burden on users to provide high-quality labels while staying engaged in their activities. This paper investigates older adults’ perceptions of providing high-quality labels in the context of training their personalized activity trackers. We conducted a co-design study with 12 older adults to envision the labeling process—describing activity names and time spans—using the teachable machines paradigm as a scaffold. We unpack the contextualized definitions of accuracy, precision, and granularity through a thematic analysis of older adults’ perspectives on activity labeling. Our findings present participants’ preferred strategies for obtaining high-quality activity labels with less burden and intrusiveness, including user-initiated labeling and machine-initiated prompting. We discuss design considerations for future data labeling tools that address discrepancies between user perceptions and technical standards in training personalized activity trackers.

2. IMWUT

   

   From Verbal Reports to Personalized Activity Trackers: Understanding the Challenges of Ground Truth Data Collection with Older Adults in the Wild

   Hossein Khayami, Lining Wang, Young-Ho Kim, Bongshin Lee, David E Conroy, and 3 more authors

   Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, Jun 2025

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   Tracking activities holds great potential to improve the well-being of older adults, yet the accuracy of activity trackers for this demographic remains in question. Evaluating this accuracy requires ground-truth data directly from older adults, which has largely been gathered in controlled laboratory settings or labeled by researchers. Moreover, considering the diversity in older adults’ activity engagement and tracking preferences, personalized activity tracking appears necessary. We demonstrate that older adults can benefit from personalized activity trackers by showing that cadence thresholds for stepping intensities vary within this group. However, collecting ground-truth data from older adults in real-world settings poses unique challenges. This paper examines two sources of ground-truth labels for the smartwatch Inertial Measurement Unit (IMU) data collected with older adults. Using verbal self-reports and a thigh-worn activity tracker, we assess their viability as ground-truth sources in natural settings. Additionally, we evaluate the costs and benefits of triangulating these sources as a ground-truth proxy. Our findings reveal two main costs: data shrinkage and notable effort from both contributors and data stewards. Simultaneously, we observe improved data quality and a greater ability to identify error sources when evaluating a trained model.

2024

1. arXiv

   

   IMUOptimize: A Data-Driven Approach to Optimal IMU Placement for Human Pose Estimation with Transformer Architecture

   Varun Ramani, Hossein Khayami, Yang Bai, Nakul Garg, and Nirupam Roy

   arXiv preprint arXiv:2402.08923, Jun 2024

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2. Scientia

   

   A joint encryption-encoding scheme using QC-LDPC codes based on finite geometry

   Hossein Khayami, Taraneh Eghlidos, and Mohammad Reza Aref

   Scientia Iranica, Jun 2024

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   Joint encryption encoding schemes have been released to fulfill both reliability and security desires in a single step. Using Low Density Parity-Check (LDPC) codes in joint encryption encoding schemes, as an alternative to classical linear codes, would shorten the key size as well as improving error correction capability. In this article, a joint encryption encoding scheme using Quasi-Cyclic Low Density Parity-Check (QC-LDPC) codes based on finite geometry is presented. It is observed that our proposed scheme not only outperforms its predecessors in key size and transmission rate, but also remains secure against all known cryptanalyses of code-based secret key cryptosystems. In this paper, we have proposed an idea to make QC-LDPC based cryptosystems secure against reaction attacks. It is subsequently shown that our scheme benefits from low computational complexity. By taking the advantage of QC-LDPC codes based on finite geometry, the key size of our scheme is very close to its target security level. In addition, using the proposed scheme, a wide range of desirable transmission rates are achievable. This variety of codes makes our cryptosystem suitable for a number of different communication and cryptographic standards such as wireless personal area networks (WPAN) and digital video broadcasting (DVB).

2020

1. IEEE WCNC

   

   Dynamic HARQ with Guaranteed Delay

   Mahyar Shirvanimoghaddam, Hossein Khayami, Yonghui Li, and Branka Vucetic

   In 2020 IEEE Wireless Communications and Networking Conference (WCNC), May 2020

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   In this paper, a dynamic-hybrid automatic repeat request (D-HARQ) scheme with guaranteed delay performance is proposed. As opposed to the conventional HARQ that the maximum number of re-transmissions, L, is fixed, in the proposed scheme packets can be re-transmitted more times given that the previous packet was received with less than L re-transmissions. The dynamic of the proposed scheme is analyzed using the Markov model. For delay sensitive applications, the proposed scheme shows a superior performance in terms of packet error rate compared with the conventional HARQ and Fixed retransmission schemes when the channel state information is not available at the transmitter. We further show that D-HARQ achieves a higher throughput compared with the conventional HARQ and fixed re-transmission schemes under the same reliability constraint.

2013

1. IEEE

   

   Cognitive radio ad hoc networks for smart grid communications: A disaster management approach

   Hossein Khayami, Mohsen Ghassemi, Kamyar Ardekani, Behrouz Maham, and Walid Saad

   In 2013 IEEE/CIC International Conference on Communications in China (ICCC), Aug 2013

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   The explosive growth in users’ demand in both areas of wireless communications and power generation has led to design of new key technologies that will be dominant in the near future; cognitive radio networks in communications and smart grid in power field. This paper proposes a novel scenario to marry these technologies together by using a cognitive radio ad hoc network (CRAHN) as the foundation of smart grid communications. It discusses formation and throughput of such a citywide network, the information transferred by the network, and how this structure can be relied upon in disasters, compared to the state-of-the-art.

2012

1. IEEE

   

   Smart plugs for building energy management systems

   Hamed Morsali, Seyed Mohammad Shekarabi, Kamyar Ardekani, Hossein Khayami, Alireza Fereidunian, and 2 more authors

   In Iranian Conference on Smart Grids, May 2012

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   Due to rising value of energy supplies, the need for managing electrical energy sources becomes prominent. In this paper, a smart plug device is presented; which provides features to measure energy consumption and recognizes the type of attached electrical devices. Furthermore, the proposed framework enables home controller systems to monitor and control home energy consumption efficiently. Subsequently an analysis of energy consumption of a pilot house, prior and after the installation of the smart plug, based on a hypothetical scenario, is provided. The results present positive impacts of using the smart plug on energy consumption rate; especially during peak hours.