Investigating Inconsistencies in PRNU-Based Camera Identification

PRNU (Photo-response non-uniformity) is widely considered a unique and reliable fingerprint for identifying the source of an image. The PRNU patterns of two different sensors, even if belonging to the same camera model, are strongly uncorrelated. Therefore, such a fingerprint is used as evidence by various law enforcement agencies for source identification, manipulation detection, etc. However, in recent smartphones, images are subjected to significant in-camera processing associated with computational photography. This heavy processing introduces non-unique artifacts (NUA) in such images and masks the uniqueness of the PRNU fingerprint. In this work, we investigate the robustness of PRNU in modern smartphones. We propose a model that explains the unexpected behavior of PRNU in such smartphones. Finally, we present two methods to identify images suffering from NUA. Our methods achieve high accuracy in identifying such images

Gesture Recognition with mmWave Wi-Fi Access Points: Lessons Learned

In recent years, channel state information (CSI) at sub-6 GHz has been widely exploited for Wi-Fi sensing, particularly for activity and gesture recognition. In this work, we instead explore mmWave (60 GHz) Wi-Fi signals for gesture recognition/pose estimation. Our focus is on the mmWave Wi-Fi signals so that they can be used not only for high data rate communication but also for improved sensing e.g., for extended reality (XR) applications. For this reason, we extract spatial beam signal-to-noise ratios (SNRs) from the periodic beam training employed by IEEE 802.11ad devices. We consider a set of 10 gestures/poses motivated by XR applications. We conduct experiments in two environments and with three people.As a comparison, we also collect CSI from IEEE 802.11ac devices. To extract features from the CSI and the beam SNR, we leverage a deep neural network (DNN). The DNN classifier achieves promising results on the beam SNR task with state-of-the-art 96.7% accuracy in a single environment, even with a limited dataset. We also investigate the robustness of the beam SNR against CSI across different environments. Our experiments reveal that features from the CSI generalize without additional re-training, while those from beam SNRs do not. Therefore, re-training is required in the latter case

Multi-modal pose estimation in XR applications leveraging integrated sensing and communication

Abstract: Mobile extended reality (XR) applications are anticipated to generate substantial traffic for 6G. Such applications not only require high data rate and low-latency transmissions, but also accurate and real-time pose estimation to enable interactive and immersive experiences. While sub-6 GHz signals have been exploited for pose estimation, they cannot cope up with multi-gigabit data rates required by XR applications. Instead, mobile communications at mmWave frequencies can potentially support data rates up to several giga-bits per second (Gbps) and, therefore, can be used to deliver XR content wirelessly to the Head-Mounted Display (HMD). Moreover, mmWave frequencies can offer improved sensing due to the large available bandwidth. Therefore, mmWave communications can play a crucial role in enabling device-free interactivity by offering both high-speed communication and accurate sensing capabilities. However, mmWave propagation characteristics are different from sub-6 GHz. Path loss plays a significant role, and can lead to degraded sensing performance. Therefore, our proposal supplements wireless sensing at mmWave frequencies with wireless electromyography (EMG) armbands. By capturing patterns of muscle activities, we can counteract the limitations of mmWave-based pose estimation, thereby enriching the granularity and precision of pose estimation. This paper proposes a conceptual architecture to achieve multi-modal pose estimation for XR applications. Early results highlight the shortcomings of mmWave-based sensing, and we identify future steps and opportunities on integration of both approaches