###### Abstract
When the application goes beyond positioning, the more general term of visible light sensing (VLS) is used for the latter arrangement. VLS in its most general specification refers to a technology that performs various tasks, such as pose detection [11] or gesture recognition [12], by analyzing the intensity and/or the spectral composition of the impinging light on the photosensitive device. VLS can be broken down into two main categories: the categories of line-of-sight systems and non-line-of-sight systems [13]. The term \"Backscattered VLS\" is also often used for non-line-of-sight scenarios. Identical to the descriptions given in the field of VLP, also in the literature regarding VLS, the line of sight is understood as a straight line between the light source(s) and the receiving element(s), and therefore, in non-line-of-sight systems, the emitted light must be at least reflected (or backscattered) once in order to reach the receiving element [13]. In this work, we focus on such a backscattering approach, which again can be divided into two subcategories. These two subcategories are distinguishable by means of whether the object or the person is intentionally equipped with purposive materials (codes) to reflect the light with a distinct intensity and/or spectral composition, or if the object or person remains unmodified (is not equipped with target-oriented codes). The latter consequently means that the reflections are solely based on the geometrical shapes and the \"natural\" compositions of the object or person's surfaces themselves. From the viewpoint of comfort, this second subcategory, that leaves the object or person's surfaces unmodified, is the more favorable one, but has some limitations when different objects that have similar shapes and surface compositions have to be distinguished. Therefore, in our work, we focus on the first of these subcategories in which we place so-called \"markers\" on the object. For the realization of these markers, we chose off-the-shelf retroreflective foils in distinct size configurations, which are cheap and easy to handle and apply. Consequently, we can argue that the utilization of these markers also causes only minimal effort and cost. This work is an extension and continuation of our previous studies presented in [14, 15]. In these studies, we showed that the identification and speed estimation of an indoor moving object can be performed successfully and accurately by means of visible light sensing in a backscattering VLS setup by utilizing the bespoken off-the-shelf retroreflective foils. The main concept of our previous studies and also of this study is that light emitted from the light source impinges on the retroreflective foils and is consequently reflected toward the utilized photosensitive device, collocated in close vicinity to the light source, with no direct line of sight between the light source and the photosensitive device, but with the implication that there is no obstruction present in the path from the light source toward the retroreflective foils, as well as in the path from the retroreflective foil toward the photosensitive element. In [14], we introduced the concept of VLS in combination with retroreflective foils mounted on a moving object, based on an algorithm that computes the Euclidean distance between the stored reference curves and current acquired data in order to perform the tasks of identification and speed estimation. As we describe later in Section 2, we refer to this also as classification since the class to be determined incorporates the applied foil in the applied size configuration (identification) and the inferred speed of the moving object in the respective class name. The moving object is an adapted Lego platform. Basically, a Lego train moves on tracks under a sender/receiver unit that we call the VLS unit. Details of the components and the setup are given in Section 2.