Hasil untuk "Telecommunication"

HUAN Hao, REN Kexue

To efficiently evaluate the performance of M-APSK modulation scheme over an additive white Gaussian noise channel, a theoretical bit error rate analysis model was proposed based on total probability formula. Firstly, the constellation plane was divided into regions according to the distribution of constellation points and their encoding characteristics. Then, the probability expression of the decision error of each bit was derived from the probability of the received symbol falling in the corresponding region. Finally, the exact closed-form solution of theoretical bit error rate was obtained. Taking 16APSK and 32APSK as examples, the theoretical bit error rate formula of all kinds of constellations was derived, which was in excellent agreement with Monte Carlo simulation. This model is universal, PSK, QAM, PAM, APSK and other modulation methods can use this model to obtain the exact closed-form solution of theoretical bit error rate. Compared with the complex two-dimensional probability integral method which relies on a large number of numerical calculations, the proposed model can give the bit error rate performance of M-APSK more conveniently.

J. S. Clowes, E. S. Page

Pengfei Ren, Lijun Jiang, Ping Li

In this work, several representative terahertz (THz) graphene holographic impedance surface antenna are presented. Different to the conventional impedance surface antenna that manipulates the surface impedance via varying the patch size in each unit cell, the surface impedance of the proposed antenna in this paper is readily controlled by applying a tunable DC biasing to each graphene patch cell, the physics behind which is that the conductivity of the graphene is a function of imposed voltage. Thus, the graphene patches of the proposed antenna have same size as well as equal spacing, which makes the modeling process more convenient and efficient. Furthermore, for the purpose of beam scanning, the proposed THz graphene holographic antenna can be easily reached by varying the DC supply. Besides, due to the excellent mechanical property of graphene, the proposed THz graphene holographic antenna can be designed conformal to required platforms. To validate and verify the proposed above ideas, a linear polarized with beam scanning capability, a circularized and a conformal THz graphene holographic antenna are designed and simulated via full-wave commercial software HFSS, the simulation results are in good agreements with the design theories.

Roxana ROȘCĂNEANU, Robert STRECHE, Filip OSIAC et al.

In recent years, the Internet of Things concept has rapidly spread in most fields because of the benefits it offers, motivating viticulturists to implement new technologies that increase crop production and quality, as well as streamline production costs. The study’s purpose is to monitor, using Internet of Things technology, two methods of identifying vine-specific diseases, which can be determined by environmental conditions (temperature, humidity, rainfall) or by analyzing diseased leaves from the vine. The first method is associated with a field study that involves placing Internet of Things sensors inside crops to measure environmental and plant parameters, which are then sent and stored in the Cloud. Based on these parameters, a correlation is made with the values that determine the occurrence of a specific vine disease (powdery mildew, downy mildew, and grey rot). The second method involves the use of Unmanned Aerial Vehicle imaging to take images containing healthy and diseased leaves from different parts of the vine. To analyze these images, a web page has been developed integrating a machine learning algorithm that detects the leaf state from the drone image footage. After the analysis all the values are stored in a database and the results are displayed as graphs and charts that are visualized by the viticulturist so that he can take the necessary actions. This study is an important step in the implementation of Internet of Things technology in viticulture, helping to monitor the main environmental and plant parameters, as well as detecting the occurrence of diseases among the vine cultures.

Dorenda Slof, Flavius Frasincar, Vladyslav Matsiiako

Abstract Due to low switching costs and stiff competition, customer relationship management has become a central component in the marketing strategy of telecommunication service providers. Since the costs of acquiring a new customer are five times higher than the costs of maintaining an existing customer, telecommunication service providers are eager to reduce the churn rate. A solid understanding of customer churn behavior can help to address this problem. Reducing the churn rate can translate into significant revenue gains and might provide the edge to outperform the competitor. In this paper, we predict the propensity to churn for customers of a Dutch telecommunication service provider by employing a duration model. While predicting churn, we simultaneously predict the reason for which the customer churns, using a competing risks model. Since the telecommunication service provider has valuable textual data based on transcripts of calls between customers and the customer service center, we incorporate topics extracted from this textual data as variables in our models, by employing Latent Dirichlet Allocation (LDA). We compare four models and find that the models that have incorporated topic variables usually yield the best churn forecasts. Also, the investigated models beat the considered benchmark model, which is the model currently deployed at the telecommunication service provider.

Ankur Tiwari, Raj Kumar, Abhishek Saxena

–Fiber optic systems are important telecommunication infrastructure for world-wide broadband networks. Wide bandwidth signal transmission with low delay is a key requirement in present day applications. Optical fibers provide enormous and unsurpassed transmission bandwidth with negligible latency, and are now the transmission medium of choice for long distance and high data rate transmission in telecommunication networks. This paper gives an overview of fiber optic communication systems including their key technologies, and also discusses their technological trend towards the next generation.

Zihao Fu, Yu Zhang, Xiongwen Zhao et al.

Abstract In this work, an artificial neural network (ANN) based time‐varying channel modeling framework is proposed, including a playback model and a prediction model. The purpose of the ANN‐based modeling framework is to playback 5G measured radio channels at certain measurement positions, and further predict large scale channel parameters (LSCPs) at unmeasured positions with limited amount of measurement data. 28 GHz channel measurements were also conducted at a high‐voltage substation for the first time worldwide to meet with 5G radio system deployment for China Energy Internet. Meanwhile, the performance of the playback channels is evaluated by comparison with the measurements and traditional geometry based stochastic modeling (GBSM) simulated channels. An optimized radial basis function (ORBF) ANN is applied in the prediction model, and the predicted LSCPs are compared with the other approaches, which shows that the ORBF has the best performance. This work offers a solution to predict radio channels and parameters in case of big measured or simulated channel datasets.

Guo Li

Abstract A scenario of uplink transmissions from multiple single‐antenna users to a base‐station with large number of antennas is considered in this letter. Based on the conditional statistic properties of the received signals, a maximum likelihood‐based detector without prior channel state information is firstly presented. In order to estimate the whole transmitted symbols successfully, the optimal signal design can be equivalently converted to a max–min problem based on the conditional covariance matrix of the received signals. From the asymptotic performance analyses with the lower and upper bounds of the pairwise error probability, we show that the pairwise error probability decays exponentially with the number of receiver's antennas, which we define as the asymptotic full‐receiver‐diversity order in non‐coherent massive MIMO systems. In addition, we present the numerical results and illustrate the comparisons with several non‐coherent transmission schemes in the state‐of‐the‐art to verify the performance of our proposed scheme.

R. Kaur, V. Krishnasamy, N. Kandasamy

V. A. Prabhala, B. Baddipadiga, P. Fajri et al.

This paper examines existing and future direct current (DC) distribution systems with a wide range of applications in data centers, telecommunication systems, commercial buildings, residential homes, electric vehicles, spacecraft, and aircrafts. DC distribution systems have many advantages and disadvantages over their alternating current (AC) counterparts. There are a few surviving examples of DC distribution systems; among them are the telecommunication systems and data centers that use the low-voltage 48 Vdc systems. However, recently, there has been a move towards higher DC bus voltages. In this paper, a comparative study of different DC distribution architectures and bus structures is presented and voltage level selection is discussed for maximizing system efficiency and reliability, reducing system costs, and increasing the flexibility of the system for future expansion. Furthermore, DC distribution systems are investigated from a safety standpoint and the current global market for these distribution systems is also discussed.

Li Zhen, Teng Sun, Guangyue Lu et al.

This paper deals with the crucial issue of random access (RA) preamble design and detection for fifth generation new radio (5G NR) enabled satellite communication systems. In consideration of the characteristics of satellite environment and system compatibility, a long preamble sequence is first constructed by cascading multiple different root Zadoff-Chu (ZC) sequences with large sub-carrier interval in time domain. Then, we further present a multiple sequence joint correlation (MSJC) based one-step timing detection scheme to effectively estimate the value of timing advance (TA), which is capable of flexibly adjusting the number of available ZC sequences involved in correlation operation. The superiority of the proposed method is mathematically validated in terms of robustness to carrier frequency offset (CFO), mitigation of noise, as well as computational complexity. Numerical results in a typical low-earth-orbit (LEO) based non-terrestrial network (NTN) scenario demonstrate that the proposed method, without the pre-compensation of timing and frequency offset, can achieve a remarkable timing performance improvement in comparison with the existing methods.

Yuanyuan Xu

Abstract Multiple description coding (MDC) provides a favorable solution for human-centered image communication, which takes into account people’s varying watching situations as well as people’s demand for real-time image display. As an effective technique for MDC, three-description lattice vector quantization (3D-LVQ) is considered for image coding in this paper. Based on intra- and inter-correlation in the 3D-LVQ index assignment as well as wavelet intra-subband correlation, a novel predictive decoding method for 3D-LVQ-based image coding is proposed to enhance side decoding performance, which attempts to predict lost descriptions (sublattice points) in a good way for better reconstructions of wavelet vectors (fine lattice points) in the side decoding. Experimental results validate effectiveness of the proposed decoding scheme in terms of rate-distortion performance.

Harshali Zodpe, Ashok Sapkal

Data transferred in an electronic way is vulnerable to attacks. With an aim to protect data for secure communication, a new Hybrid non pipelined Advanced Encryption Standard (AES) algorithm based on traditional AES algorithm with enhanced security features is proposed in this work. Abysmal analysis of the AES algorithm implies that the security of AES lies in the S-box operations. This paper presents a new approach for generating S-box values (modified S-box) and initial key required for encryption/encryption (improved key generation) using PN Sequence Generator. The AES algorithm with proposed modifications shows significant improvement in the encryption quality as compared to traditional AES algorithm. The traditional AES algorithm equipped with proposed novel modified S-box technique and improved key generation technique gives an avalanche effect of 60% making it invulnerable to attacks. The proposed design is synthesized on various Field Programmable Gate Array (FPGA) devices and compared to the existing designs resulting in significant improvement in throughput. The proposed design is implemented on Spartan6 FPGA device. Keywords: Advanced Encryption Standard (AES), Field Programmable Gate Array (FPGA), PN Sequence Generator

Devendra Kumar, R. Sharma

D. Schall, D. Neumaier, M. Mohsin et al.

I. Colak, E. Kabalcı, G. Fulli et al.

Xiaojun Zhang, V. Venkatesh

J. V. Beek, P. Börjesson, M. Boucheret et al.

June-Seok Lee, Kyo-Beum Lee

Preeti K. Dalvi, Siddhi K. Khandge, Ashish Deomore et al.