Reconfigurable intelligent surface (RIS) has emerged as a promising technology for enhancing communication systems. This paper investigates a novel flexible-position RIS-assisted communication system, where the RIS is mounted on a slide rail, enabling spatial adaptability. Unlike traditional fixed-position RISs, the proposed system leverages both spatial flexibility and phase reconfigurability to optimize system performance while reducing overhead through strategic position adjustment. To characterize the spatial variations introduced by RIS movement, we propose a generalized RIS channel model that integrates a practical visibility region function with near-field spherical wave propagation. This model captures the spatial correlation characteristics influenced by multipath angular spread, scatterer distribution, and RIS positioning. Furthermore, we introduce a measurement scheme using a multi-state RIS hardware to analyze segmented channels across fixed-position and flexible-position scenarios. Our measurement reveals that the intra-cluster power angular spectrum follows a Gaussian distribution, and in strong scattering environments, spatial correlation exhibits an enhanced degree of freedom due to spatial non-stationarity effects. In particular, the experimental results demonstrate that the gain of the received power varies from 0.4 dB to 5.3 dB across different RIS positions, providing empirical evidence that spatial adaptability of RIS effectively resists channel non-stationarity. These findings highlight the potential of flexible-position RIS to enhance future wireless communication systems.

Reconfigurable intelligent surface (RIS) has garnered significant attention in wireless communications due to its electromagnetic wave manipulation capabilities. In order to ensure the effectiveness of various transmission designs in practical environment, the channel characteristics of RIS-assisted wireless communication systems warrant thorough investigation. While substantial research has been conducted on large-scale channel characteristics, there remains a lack of measurement-based studies on channel small-scale characteristics. This paper conducts channel measurement campaigns, analyzing delay characteristics and multi-cluster properties in multiple indoor and outdoor environments, including square, corridor, and classroom scenarios. The measurement results indicate that the RIS-assisted path (i.e. the virtual line-of-sight (VLOS) path) makes the channels exhibit two-cluster characteristics analogous to conventional line-of-sight channels. Moreover, in classroom scenario, VLOS path generates reflected echoes that degrade the channel delay characteristics. Building on these findings, this paper proposes a small-scale channel modeling framework comprising a two-cluster-based channel impulse response (CIR) model and a K-factor-based CIR model. The simulation and measurement results demonstrate satisfactory agreement, validating the effectiveness and practicality of the proposed framework. Two types of CIR models that are unified with the traditional CIR model form, along with an optional echo component, make this framework flexible and easy to use. The proposed small-scale modeling framework can effectively characterize the power delay profiles of RIS-assisted channels, providing References for future research on RIS-assisted wireless communications.

Reconfigurable intelligent surface (RIS) has gained significant attention as an innovative solution for enhancing communication system performance. This paper proposes a novel fluid RIS-assisted communication system with spatial adaptability, where the RIS is mounted on a slide rail. By leveraging both spatial flexibility and phase reconfigurability, the proposed system overcomes the limitations of conventional fixed-position RIS. To characterize the spatial variations introduced by RIS movement, we establish a novel channel modeling framework that combines near-field spherical wave propagation with practical visibility region functions. Experimental results reveal that dynamic RIS position yields received power gain variations ranging from 0.4 dB to 5.3 dB. This empirical evidence strongly validates the capability of fluid RIS to counteract channel non-stationarity.

In recent years, reconfigurable intelligent surfaces (RISs) have attracted significant attention from both academia and industry due to their ability to manipulate electromagnetic waves in wireless communication. In particular, the characteristics of wireless channels incorporating RISs offer substantial research value. Several previous studies have investigated the path loss characteristics of RIS-assisted wireless channels in practical scenarios. However, these pioneering studies ignore the effect of RIS array gain on path loss. This paper proposes a floating-intercept (FI) path loss model that includes the array gain of the RIS, the distance between the transmitter and the RIS, and the distance between the receiver and the RIS. In this RIS-FI model, the RIS array gain component is related to the reflection coefficients of all the unit cells of RIS. The proposed model can effectively characterize path loss in both the far-field and near-field regions of the RIS. A fabricated 512-element RIS and a vector network analyzer (VNA) are utilized to set up the channel measurement system. The proposed RIS-FI path loss model is validated by using measurement data collected from multiple scenarios, including outdoor square, indoor corridor, and classroom. Compared to other RIS path loss models, the experimental results show that the proposed model offers better accuracy in describing path loss in the near-field region of the RIS. The RIS-FI path loss model presented in this paper may pave the way for further research on RIS-assisted wireless channels.

Reconfigurable intelligent surface (RIS)-empowered communication, has been considered widely as one of the revolutionary technologies for next generation networks. However, due to the novel propagation characteristics of RISs, underlying RIS channel modeling and measurement research is still in its infancy and not fully investigated. In this paper, we conduct multi-scenario broadband channel measurements and modeling for RIS-assisted communications at the sub-6 GHz band. The measurements are carried out in three scenarios covering outdoor, indoor, and outdoor-to-indoor (O2I) environments, which suffer from non-line-of-sight (NLOS) propagation inherently. Three propagation modes including intelligent reflection with RIS, specular reflection with RIS and the mode without RIS, are taken into account in each scenario. In addition, considering the cascaded characteristics of RIS-assisted channel by nature, two modified empirical models including floating-intercept (FI) and close-in (CI) are proposed, which cover distance and angle domains. The measurement results rooted in 2096 channel acquisitions verify the prediction accuracy of these proposed models. Moreover, the propagation characteristics for RIS-assisted channels, including path loss (PL) gain, PL exponent, spatial consistency, time dispersion, frequency stationarity, etc., are compared and analyzed comprehensively. These channel measurement and modeling results may lay the groundwork for future applications of RIS-assisted communication systems in practice.

Reconfigurable intelligent surface (RIS)-empowered communication has recently drawn significant attention due to its superior capability in manipulating the wireless propagation environment. However, the channel modeling and measurement of RIS-assisted wireless communication systems in real environment has not been adequately studied. In this paper, we construct a channel measurement system using vector network analyzer (VNA) is used to investigate RIS-assisted wireless communication channel in outdoor scenarios at 2.6 GHz. New path loss (PL) models including angle domain information are proposed by refining the traditional close-in (CI) and floating-intercept (FI) models. In the proposed models, both influences of the distance from transmitter (TX) to RIS and the distance from receiver (RX) to RIS on the PL, are taken into account. In addition, the value of root mean square (RMS) delay spread of RIS-assisted wireless communication is found to be much smaller than that of the traditional non line-of-sight (NLOS) case, implying that RIS provides a virtual line-of-sight (LOS) link.

In this paper, we propose and design a IOT system that includes wearing glass and walking assistant for the blind people to guide them in daily life. Both the wearing glass design and walking assistant design falls into the scope of internet of things(IOT) design. Firstly, both the wearing glass and walking assistant are illuminated in function design and layout design. Secondly, the diagram of all components design are outlined and communication mechanism are highlighted. Finally, initial simulations are shown to validate our design. The layout design for this glass is demonstrated by figures. Security and privacy issues are paid attentions compared to Google glass design. Key enabling technologies for IOT are used in our design including Clouds computing, ZigBee communications to ensure the design is simple but efficient and of high security and privacy at the same time.

In this paper, we further investigate the spread communication approach using Chrestenson function and consider the practical aspects of it applications in modern communications technologies. First we elucidate the basics we published at reference [1], and outlined the communication basics including Shannon theory etc. Secondly, we highlight the trade-off among security/privacy, speed and authenticity and further investigate the practical aspects that can be applied in spread communications using Chrestenson function. Finally, we illustrate a fast algorithm of Discrete Chrestenson transform and show how it can be exploited to speed up the communication speed rate while keeping a high security. Our paper concentrates on investigating the security and privacy aspects in spread communication by using Chrestenson function.

This paper presents a study of blind system identification using measurements of multiple sensors. The mathematical model we consider here consists of multiple FIR channels driven by an unknown common source. We first show an orthogonal complement system matrix which is very useful in understanding the multi-channel system and developing efficient identification techniques. We then show a fast maximum likelihood method, its relation to a cross-relation method, and a new method utilizing a minimum noise subspace. We also report a study of strict identifiability of the multi-channel system and its relation to existing concepts.

In this paper the power spectral density of p-adic stationary stochastic process under the sense of Chrestenson transform (Ch-transform) and its maximum entropy estimator are studied. The relationship formula between the power spectral density and the entropy rate is first derived. The the normal equations of maximum Ch-entropy spectral estimator in closed expression are obtained. When the number of autocorrelation data is p/sup m/, where p/spl ges/2 and m/spl ges/1 are integers, the maximum Ch-entropy estimator can be directly expressed by the known finite autocorrelation data. These results are quite different from that of Fourier's. Numerical examples are provided to show the effectiveness of the maximum Ch-entropy estimator. General Hadmard ordering is introduced for the Kronecker formulation of the Ch-transform matrix. Such ordering can lead to a fast algorithm proposed in this paper which can reduce the computation complexity front O(p/sup 2m/) to O(mp/sup m/) when the number of autocorrelation data is p/sup m/ (m>1, p/spl ges/2).>