Vital signs (e.g., respiration rate or heartbeat rate) sensing is of great importance to implement pervasive in-home healthcare. Traditional vital signs monitoring approaches usually require users to wear some dedicated sensors. These approaches are intrusive and inconvenient to use, especially for elderly people. Some non-intrusive vital signs monitoring approaches based on wireless sensing have been proposed in recent years. However, these approaches require the target user to be in situ during the monitoring process, which greatly limits their utilization in practical scenarios where the target users usually move around. In this paper, we propose RF-RMM, an RFID-based approach to accurate and continuous respiration monitoring for mobile users. The major challenge in respiration monitoring for moving people is that the tiny body displacement caused by the user’s respiration is overwhelmed by the user’s entire body movement. To address this issue, we propose a novel approach that uses a pair of tags to eliminate the effect of the user’s body movement. We fuse the data from the paired tags to cancel the effect of the user’s entire body movement and retain only the displacement caused by the user’s respiration. Another challenging issue in implementing RF-RMM is how to resolve the phase ambiguity problem when the target user moves around, which becomes more serious than in the static case. We propose a distance tracking algorithm to track the phase transition during the user’s movement, according to which the phase ambiguity problem can be well handled. We implement RF-RMM on commercial RFID devices and conduct extensive real-world experiments to evaluate its performance. The results show that RF-RMM achieves accurate respiration rate monitoring with an average error of 0.54 BPM in estimating different users’ respiration rate and an average relative error of less than 13% in estimating the user’s individual breath length.

中文翻译：

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使用商用 RFID 设备为移动用户提供准确的呼吸监测

生命体征（例如，呼吸率或心跳率）感测对于实施普遍的家庭保健非​​常重要。传统的生命体征监测方法通常需要用户佩戴一些专用传感器。这些方法具有侵入性且使用不方便，特别是对于老年人而言。近年来提出了一些基于无线传感的非侵入式生命体征监测方法。然而，这些方法在监控过程中需要目标用户在原地，这极大地限制了它们在目标用户经常走动的实际场景中的使用。在本文中，我们提出了 RF-RMM，这是一种基于 RFID 的方法，可为移动用户提供准确且连续的呼吸监测。移动人呼吸监测的主要挑战是用户呼吸引起的微小身体位移被用户的整个身体运动所淹没。为了解决这个问题，我们提出了一种新颖的方法，它使用一对标签来消除用户身体运动的影响。我们融合来自配对标签的数据，以消除用户整个身体运动的影响，只保留用户呼吸引起的位移。实现 RF-RMM 的另一个具有挑战性的问题是如何解决目标用户移动时的相位模糊问题，这比静态情况下变得更加严重。我们提出了一种距离跟踪算法来跟踪用户移动过程中的相变，据此可以很好地处理相位模糊问题。我们在商用 RFID 设备上实施 RF-RMM，并进行广泛的实际实验以评估其性能。结果表明，RF-RMM实现了准确的呼吸率监测，估计不同用户呼吸率的平均误差为0.54 BPM，估计用户个体呼吸长度的平均相对误差小于13%。