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As a key technology of 5G advanced networks, the reconfigurable intelligent surfaces (RISs) have received widespread attention in the academia and the industry. To provide insights on the application scenarios and standardization roadmap of future-oriented RISs, we analyze characteristics of RISs and summarize white papers, projects and standardization efforts related to RISs. The difficulties and challenges in RIS research and standardization are also analyzed and our forecast on the roadmap of standardization on RIS is given accordingly.

Terahertz has an emphatic effect on increasing data rates, supporting ultra-dense connections, and realizing low-latency transmission. In this paper, we investigate the peculiarity of the terahertz spectrum, study the propagation characteristics of terahertz technology, and discuss its channel modeling feature. Given the unique spectral characteristics of terahertz bands, physical layer waveforms, modulation, coding schemes are designed accordingly to reduce the peak-to-average power ratio (PAPR), increase the spectral flexibility, meet the backward compatibility and improve the system performance. The baseband signal processing of terahertz signals is analyzed and discussed in this paper, inspiring the design of future terahertz communication systems.

In this paper we consider a passive radar system which doesn’t rely on the reception of reference signals from direct paths. A blind channel estimation based method is derived by exploring the relationship among the transmitted signal, the channel response and the received signal. With the help of this novel method, multiple incoming targets illuminated by a non-cooperative transmitter can be detected by a distributed radar system with at least two receivers. Numerical results demonstrate the feasibility and accuracy of the proposed method and some characteristics of the detector, namely, the performance as a function of the signal to noise ratio (SNR) and the number of radar receivers.

This paper investigates statistical quality of service (QoS) guarantee in a downlink non-orthogonal multiple access (NOMA) system with statistical channel state information (CSI). The statistical QoS requirements are based on the theory of effective capacity (EC). To be more specific, we employ joint power and rate allocation to satisfy EC constraints while minimizing the total power consumption of users. As deriving the optimal power and rate allocation through mathematical analysis is nontrivial, we alternatively propose a low-complexity algorithm that can find a feasible solution. The proposed solution is optimal under the provided optimality condition. Besides, a tight lower bound of total power is obtained through analysis. Numerical results validate our analysis.

In the last decade, deep neural networks (DNNs) have shown impressive results in various fields such as image classification, speech recognition, or playing the abstract strategy board game Go. Recently, also an increased interest in the application of DNNs to physical layer problems in digital communications can be observed. We use a DNN for one-shot decoding of convolutional (self-orthogonal) codes. An advantage of this use case is the unlimited amount of labeled data for training. A disadvantage is, that the number of code words to be learned increases exponentially with the dimension of the code. We compare the performance of the DNN-based decoding with iterative threshold decoding (ITD). Here, a discrete-time high-order recurrent neural network (HORNN) is used as a computational model for ITD. Unfolding the HORNN in time, we arrive at a DNN with a special structure as defined by the HORNN. With a training procedure we can optimize the performance of this unfolded HORNN (uHORNN). The advantage of this approach is that the structure of the uHORNN is determined by the structure of iterative threshold decoding. Only a few weights, which are shared within and between the layers, must be adapted to optimize the network. In this way we combine the advantages of both approaches, the structured approach of the HORNN as a computational model, on the one hand, and the training based optimization as given by a DNN on the other hand.

The 5th generation (5G) of wireless communications have stringent requirements on latency and data rate. To support this, the millimeter wave (mmWave) bands above 10 GHz have gained great attraction. However, considering the severe isotropic path loss and the harsh propagation experienced at such high frequencies, a dense base station deployment is required, which may be unrealistic due to the unavailability of fiber drops to provide wired backhauling. Integrated access and backhaul (IAB), where the wireless connection is used for the backhaul connection of base stations instead of fiber, is an attractive solution which could allow easier deployment of a dense network. In IAB, packets may be forwarded by multiple IAB nodes before arriving at the base station. Thus, how to guarantee the Quality of Service (QoS) requirement needs to be studied. In this work, we propose some QoS assurance methods based on three scenarios in IAB network. The first one is integration case, and we propose some methods to accelerate the access of IAB node. We consider that the IAB node is able to forward data for the others in the second scenario. To ensure the QoS requirements for different forwarded packets, we optimize the backhaul radio link control channel setup/modification procedure, and put forward some bearer mapping schemes. IAB node migration is considered as the third scenario due to the vulnerable wireless backhaul links. Simulation results demonstrate that some assistant information, e.g. hop count and load information, may help the integrated IAB node select a suitable parent node and thus satisfy the access latency requirement.

Spectrum resource is a key point for future development of International Mobile Telecommunication (IMT). According to WRC-19 conclusions, 24.25-27.5GHz frequency band is identified to IMT. However, spectrum 25.25-27.5GHz has been allocated to inter-satellite service (ISS). It is essential to ensure the coexistence between IMT and ISS. This paper provides an analysis of the sharing between IMT-2020 (5G) system and geostationary satellite networks in the inter-satellite service (ISS) in the frequency band 25.25-27.5GHz. Moreover, A Monte Carlo simulation methodology is used for assessing the aggregate interference from multiple IMT base stations (BSs) and user equipments (UEs) to a data relay satellite (DRS) in ISS system. The results show that the coexistence between IMT BSs plus UEs and inter-satellite service space station is feasible in this frequency band.

With the deployment of the 5G, lower latency and higher frequency brings not only the users' satisfaction but also the dense deployment of base stations which causes large energy consumption. Thus, energy saving is a challenging issue. Machine learning techniques, which could extract features from raw data in the wireless access network and predict the future state by the previous features, are useful to energy saving. In this paper, we proposed the energy saving scheme based on machine learning techniques to achieve the balance between system performance and energy efficiency. Cell switching-off by load prediction using different algorithms, and dynamic threshold adjustment improve the energy efficiency and thereby reduces the operation cost. By demonstrating the results of experiments in wireless environment, the switch-off duration could reach up to 176% increase, and the energy scheme can save up to 2, 223 RMB electricity saving per week per cell.

In order to grasp the impact of climate change on tea and better develop tea meteorological services, according to the daily meteorological observation data of the National Meteorological Station of Guzhang County from 1981 to 2015 and the quality inspection data of the Tea Research Institute, fuzzy mathematics method and weighted index are used to study the occurrence and development of tea and its impact on Guzhang Maojian tea. The results showed that the annual average temperature increased obviously, the average date of daily mean temperature passing through 10 °was March 24, and the climate tendency rate was -3.8d/10a, and the changes of precipitation and sunshine hours tended to be consistent with those of tea growing season. The main meteorological disasters affecting the production of Guzhang Maojian tea are high temperature heat damage, frost, in which the high temperature heat damage is mainly mild to moderate, most of which occurs in July to August, and the frequency increases after 2000, which has an effect on summer and autumn tea, the number of frost days shows a decreasing trend, and the tendency rate is 1.123 d/10a, which is beneficial to the growth of tea. Climate change had no effect on tea quality. Dryness was less than 0.5, relative humidity was more than 80%, spring tea quality was high, total tea polyphenols, amino acids, caffeine and catechin were 22.41 ~28.85%, 3.79 ~ 7.96, 3.66 ~ 4.63% and 13.28 ~ 19.71, respectively. The quality of autumn tea comes next, and that of summer tea comes next. The research results can provide scientific basis for optimizing tea production layout and adapting to climate change.

In this paper, we introduce a reconfigurable artistic patch antenna with unidirectional circular-polarization (CP) radiation. The novel geometry composed of a Chinese character Meng shaped patch and dual L-shaped feeding probes that are connected to a PIN-diode-based switching circuit. The simulated and experimental results show that the proposed antenna achieves the operating bandwidth from 2.4 to 2.5 GHz that covers dynamically the 14 channels of IEEE 802.11/b/g/b/ax. By switching the L-probes, either left-handed CP or right-handed CP can be generated to cover different seven-channel blocks in order to enhance the channel efficiency. A broadside realized gain varying between 5-6 dBic and an efficiency of -0.5dB were recorded. The proposed antenna holds an overall dimension of 0.72λ0 × 0.72λ0 × 0.12λ0 with an aperture efficiency of 59% at 2.45 GHz.

Terrestrial broadcasting signals have been recognized as promising candidates for positioning and navigation needs. However, in some terrestrial broadcasting networks, which are usually single frequency networks, the transmitter confusion problem poses a huge obstacle to almost all positioning algorithms. Without knowing the transmitter identities, measurements can't be associated to transmitters coordinates properly, thus leaving receiver coordinates unable to be estimated. Meanwhile, as the exact transmission delay is usually hard to estimate, the time difference of arrival (TDoA) based positioning is widely used. In this paper, a novel TDoA based localization method is proposed to realize positioning in single frequency networks. With the proposed method, the receiver can estimate its own position when transmitter identities are missing from the signals. Simulation results verify the feasibility and accuracy of the method and discussions regarding its properties are given.

A new type of microwave planar transmission line is introduced in this paper, wherein a microstrip line (ML) is superimposed onto a coplanar waveguide (CPW) and connected with copper vias. The new planar line is designated as a composite ML/CPW line that owns a unique feature of dual signal path on a single dielectric slab. By employing meander or zigzagging line sections for the design of RF/microwave circuits such as power divider, the substrate slab area can be significantly reduced when compared with conventional planar transmission lines. Through design examples, this paper demonstrates the effectiveness of the transmission line that is well-suited for RF/microwave circuits miniaturization.

This paper introduces Chinese-character-shaped (CCS) patch antennas, wherein a Zhong-, Guo-, and Meng-shaped patch antennas were devised for circular-polarization applications. The novelty is emphasized by the SimHei font of the CCS patches at the antennas' front ends. The artistic patch antennas were singly-fed and cavity-backed by box reflectors to enhance the forward directivity and the front-to-back radiation ratio. In particular, the Guo-shaped patch, which evolved from the Wang-shaped patch and owns a meaning of country, exhibits an axial-ratio bandwidth of 110 MHz that covers the 2.4 GHz wireless local-area network (WLAN) IEEE 802.11b/g/n/ax.

Sensitivity is one of the important parameters to assess the performance of strain sensors. In order to obtain high sensitivity, a novel sensing mechanism made use of circularly-polarized (CP) patch antenna is investigated for strain monitoring. Two-dimensional strain sensing is achieved by a proof-of-concept prototype, namely, a microstrip-line-fed nearly square patch antenna sensor is initiated in this paper. Very encouraging results of high sensitivity were obtained: $+74.2\ \text{ppm}/\mu\varepsilon$ and $-67.5 \text{ppm}/\mu\varepsilon$ for two orthogonal directions whereas the sign indicates the strain direction. The proposed sensor is at least 33 times more sensitive than commercial resistive metal foil strain gages.

This paper introduces a Chinese character-shaped circularly polarized (CP) patch antenna: Zhong-shaped patch printed in SimHei font. In order to enhance the broadside gain and front-to-back radiation, a rectangular metal box is included as the antenna reflector. The Zhong-shaped patch antenna exhibits a maximum gain of 8.3 dBic, axial-ratio (3-dB) bandwidth of 6.4%, return-loss (10-dB) bandwidth of 20.4%, and a gain (7-dB) bandwidth of 17%. More importantly, the achieved operating bandwidth covers the 14 channels of IEEE 801.11 for 2.4-GHz wireless local area network (WLAN).

This paper presents mathematical models for monitoring mix-proportions of Chinese-standard concrete based on dielectric constant measurement. This technique is regarded as nondestructive nature with the meaning of early detection. The measurement makes use of microwave near-field probing technique while computer-aided measurement has been used. The devised models correlate the water-cement ratio (w/c) and the sand-aggregate ratio (s/a) with the measured dielectric constant in respective linear functions. The correlations of these ratios are also examined and the combined effect is found to be subtractive on the measured dielectric constant. As a result of this work, one can make use of these models to develop new diagnosis methods for the monitoring of accurate mix proportions by measuring the microwave permittivity of fresh concrete at early ages.

This article introduces the basic concepts of Kanji patch antennas. We use two novel L-probe-fed Guo-and Meng-shaped patches operating in circular polarization as examples. The main parameters of these symmetrical and asymmetrical shaped patch antennas were studied and optimized via computer-aided simulation.

Broadcasting signals have been recognized as promising candidates for positioning and navigation needs thanks to its many advantages compared to signals in satellite based navigation systems. However, in most single frequency broadcasting networks, the transmitter confusion problem poses a huge obstacle. One of the key steps of the time of arrival (TOA) based positioning is to measure the transmission delay of signals transmitted from all transmitters on line of sight (LOS) path, and to calculate the distance to all transmitters respectively. Without knowing the transmitter identities, the receiver cannot determine the distance to transmitters, thus can no longer determine its own position. In this paper, a novel position determination algorithm is proposed to realize positioning in single frequency networks (SFN) with five or more transmitters. The proposed algorithm can determine the receiver position under transmitter confusion problem. Simulation results show that the proposed algorithm can fulfill positioning tasks in SFN with high accuracy.

Broadcasting signals are considered as promising candidates for positioning and navigation needs thanks to its many advantages. However, most broadcasting networks are single frequency networks (SFN), in which the transmitter confusion problem poses a huge obstacle. Since all transmitters in a SFN broadcast the same signal simultaneously, the receiver cannot obtain the transmitter identities, thus can no longer determine its position. In this paper, a novel angle of arrival (AoA) based position method is proposed to realize positioning in SFN. The proposed method can overcome the transmitter confusion problem without modifications on the broadcasting sequences. Simulation results confirm that the proposed method can realize positioning in SFN with high accuracy.

The visible light communication (VLC) and wireless LAN (WLAN) heterogeneous network is considered as a highly competitive candidate for the next generation indoor wireless communication. VLC can provide high data rate as downlink mechanism while WLAN supports reliable connectivity and covers uplink needs. In such heterogeneous systems, vertical handover (VHO) is critical for the system reliability and performance. This paper proposes an improved design of the dwell timer used in VHO process by introducing a dynamic dwell timer based on prediction. Simulation results show that the proposed design outperforms benchmark designs by avoiding unwise handovers while achieving a longer connection time and higher average data rate. Simulations also prove that the proposed design is applicable to different environments and user behaviors.

Mobile Advertisement propagation has drawn increasing attention in research and industrial area.In this work, we investigate the mobile advertisement popularization for mobile social networks.Previous studies failed to be applied to mobile social networks because of extremely high overhead and low propagation efficiency.In tackling these difficulties, we propose eMAP, (efficient mobile advertisement popularization), an efficient propagation user selection scheme with local information.Two key technologies enable eMAP to achieve efficient and effective mobile Ads popularization.First, we advocate propagation user selection instead of popular user selection, where mobile users with strong information dissemination ability could be selected.Thus the mobile user could be effectively used.Second, we use local information instead of the global information to achieve near optimal performance for propagation.In that, the information potential is leveraged to find the influential users with local information.With extensive experimental study, we find that, eMAP could effectively improve the mobile Ads delivery ratio.Using the propogation instead of popularization is validated in our experimental studies in different aspects of investigations. Moreover, when the budget is constrained, eMAP could still perform fairly well.

Provider policy (e.g., bandwidth rate limits, virtualization, CPU scheduling) can significantly impact application performance in cloud environments. This paper takes a first step towards understanding the impact of provider policy and tackling the complexity of selecting configurations that can best meet the cost and performance requirements of applications. We make three contributions. First, we conduct a measurement study spanning a 19 months period of a wide variety of applications on Amazon EC2 to understand issues involved in configuration selection. Our results show that provider policy can impact communication and computation performance in unpredictable ways. Moreover, seemingly sensible rules of thumb are inappropriate — e.g., VMs with latest hardware or larger VM sizes do not always provide the best performance. Second, we systematically characterize the overheads and resulting benefits of a range of testing strategies for configuration selection. A key focus of our characterization is understanding the overheads of a testing approach in the face of variability in performance across deployments and measurements. Finally, we present configuration pruning and short-listing techniques for minimizing testing overheads. Evaluations on a variety of compute, bandwidth and data intensive applications validate the effectiveness of these techniques in selecting good configurations with low overheads.

In order to solve how to evaluate the pros and cons of different risk assessment methods, this paper gives the definition and implementation of combination evaluation method. First, we use the DEA method based on fuzzy comprehensive evaluation to select the existing risk assessment methods, which selected methods are used to information systems for risk assessment independently, and then DEA method will evaluate the results weighted to obtain a comprehensive assessment conclusions, so to avoid the shortcomings of a single method and synthesize advantages of the various assessment methods, the assessment results have higher credibility and scientific, and achieved good results in the actual implementation of the risk assessment.

Extensive research has been done on traffic forecasting. However, performance of forecasting models is highly influenced by traffic uncertainty and predictability. Traffic uncertainty is important for road users and governors as well. With support of adequate real data from toll stations, we reveal laws in traffic flow uncertainty by employing dispersion coefficient. For further study, Hurst exponent and Approximate Entropy reflect temporal characteristics, indicating long-term randomness and short-term complexity respectively. These measurements all suggest that traffic flow uncertainty drops with the increase of time interval. Our study provides effective measuring methods of uncertainty and theoretical evidence for 15 minutes time horizon in short-term traffic prediction. Daily periodicity exists that highway traffic flow at night is more uncertain than in day time, and off-peak hour flows are more uncertain than peak hour flows. Finally, initial investigation into traffic predictability exhibits acme at 7 a.m. in our case.