Multipath Fading Problem Research Articles

A New Method of Lung Nodule Detection in CT Scans using 3D U-Net Convolutional Neural Network

Automatic detection of lung nodules in CT scans has attracted significant research interest in computer-aided diagnosis (CAD) system because it can help improve the early and accurate diagnosis, therefore reducing lung cancer mortality. The aim of this paper is to propose a new method of lung nodule detection in CT scans by using 3D U-Net convolutional neural networks (CNNs) which can successfully reflect the 3D characteristics of CT scans. We use 3D U-Net architecture for CNNs in order to accurately and automatically detect the lung nodules in CT scans. We employ the masked Lung Image Database Consortium (LIDC) dataset containing 400000 CT images of over 1000 patients for training the 3D U-Net model. We introduce an integrated loss function in order to detect lung nodules with different sizes and prepare 3D input data by the use of 2D CT images fixing the hyper parameters of CNNs. Our method successfully detects the lung nodules with different sizes ranging from 3mm to 30 mm exhibiting higher sensitivity of 93.2, 94.5 and 94.8% at 1.0, 2.0 and 3.0 FPs per patient, respectively than the state-of-the-art methods. The proposed method of using 3D U-Net CNNs and integrated loss function is effective for early diagnosis of lung nodules in different sizes with improved sensitivity

Research on Mine OFDM Intelligent Receiver Based on Deep Learning

coal is an important energy. Coal mining needs a series of equipment, among which communication equipment can ensure the safety of underground workers in the mining process and improve production efficiency. Aiming at the problems of multipath fading and anti-interference of signal transmission in coal mine, researchers propose to optimize the quality of signal transmission in coal mine with OFDM technology. Compared with traditional OFDM technology, this paper proposes a method of mine OFDM intelligent receiver based on deep learning, which aims to use deep learning technology to replace the signal recovery process of the receiver of traditional OFDM technology. The simulation results show that in terms of bit error rate, the signal recovery of the receiver based on deep learning technology is obviously better than that of the traditional OFDM receiver. This will improve the economic benefits of coal mining in the future.

Analysis and Evaluation of Channel-Hopping-Based MAC in Industrial IoT Environment

Owing to the development of the Internet-of-Things (IoT) paradigm, channel hopping is the most widely used method for solving multipath fading problem caused by various structures in industrial environments or by external interference of communication devices using the same frequency band. To meet these demands, IPv6 over the time slotted channel hopping (TSCH) mode of IEEE 802.15.4e (6TiSCH) has emerged as the standard for low power lossy networks in industrial IoT environments. TSCH supports slot-based channel hopping with the IEEE 802.15.4e standard and ensures reliable connection from external interference through strong time synchronization. Wireless Smart Utility Network (Wi- SUN), which constructs a Field Area Network (FAN), proposes non-slotted channel hopping and specifies only minimum constraints. However, there is limited existing research on these networks. Therefore, in this study, we analyze and evaluate the performance of channel-hopping-based medium access control (MAC) in an industrial environment. Simulation results in various environments show that non-competitive MAC provides reliable and efficient transmission.

Channel Estimation for Broadband Millimeter Wave MIMO Systems Based on High‐Order PARALIND Model

Channel state information (CSI) is important to improve the performance of wireless transmission. However, the problems of high propagation path loss, multipath, and frequency selective fading make it difficult to obtain the CSI in broadband millimeter‐wave (mmWave) system. Based on the inherent multidimensional structure of mmWave multipath channels and the correlation between channel dimensions, mmWave multiple input multiple output (MIMO) channels are modelled as high‐order parallel profiles with linear dependence (PARALIND) model in this paper, and a new PARALIND‐based channel estimation algorithm is proposed for broadband mmWave system. Due to the structural property of PARALIND model, the proposed algorithm firstly separates the multipath channels of different scatterers by PARALIND decomposition and then estimates the channel parameters from the factor matrices decomposed from the model based on their structures. Meanwhile, the performance of mmWave channel estimation is analysed theoretically. A necessary condition for channel parameter estimation is given based on the uniqueness principle of PARALIND model. Simulation results show that the proposed algorithm performs better than traditional compressive sensing‐based channel estimation algorithms.

Comparison of Hybrid Diversity and Space Diversity for Microwave Link Between Islands

The development of telecommunications technology today, so that some islands are still not affordable from telecommunications technology. The considerable distance between islands requires the efficiency and flexibility of the technology used. The microwave communication system is a technology that is widely implemented as a cellular network backhaul network because it has advantages in the simplicity of installation and can reach remote areas that are difficult to reach. But on the receiving side, the signal received not only comes from the LOS (Line of Sight) signal but the signal is also reflected by the surface of the Earth. The signal from some of these reflections is called multipath, the signal will cause interference that can cause fading or changes in the electromagnetic waves received. To overcome multipath fading that is too high, it is necessary to optimize antenna diversity using hybrid diversity and space diversity techniques. At maximum optimization of hybrid diversity with 135λ and 300 MHz, RSL -34.54 dBm is obtained, the fading margin is 33.70 dB, and availability is 99.99987%, the optimization is better than space diversity at maximum optimization with 135λ. Optimization of hybrid diversity has met ITU-R standards, with RSL values below -30 dBm and availability above 99.900% - 99.9966%, for the value of fading margins still do not meet the standards but can overcome multipath fading problems.

Wireless Network Planning and Optimal Radio Placement Using Egly Empirical Model

Path loss and outages are crucial in networking and need to be put into consideration in wireless network planning. The recommendation of a network layout for a particular area should be given careful thought and analysis. Preparing the design of wireless communication networks require a detailed understanding of radio propagation over the specific environment. In general, there are two basic problems of multipath fading of the radio link and interference from other users in the cellular reuse environment. In this paper, Egly propagation model was used for network planning and management to achieve optimum resource usage and minimize outages by effectively reducing path loss through empirical transmitter and receiver placement. Keywords- Empirical Model, Network Planning, Path Loss, Radio Placement

Improved Vivaldi Antenna with Radiation Pattern Control Features

Vivaldi antenna has been considered as a mitigation to the scattering effect of an antenna. However, the current performance of Vivaldi antenna suffers from multipath effect, interfering signals and radiation pattern control. This paper proposed an improved Vivaldi antenna which combined triple radiating slot to enable control of radiation pattern features. This is accomplished by controlling the position of the radiating element through the asymmetric arrangement of ideal switches to steer the beam in three desired-directions. The Using operating frequency lied between 900 MHz and 2.5GHz, the proposed design was fabricated and tested. Depending on the radiating element, the proposed antenna covered about ±90o with an almost equal gain at the three different focal in contrast to ±45o coverage of traditional rectangular microstrip antenna beam. The results satisfied pattern reconfigurability and the proposed design can be very useful for wireless communications where multipath fading problems are frequently encountered.

Time-Reversal Based Secure Transmission Scheme for 5G Networks over Correlated Wireless Multi-Path Channels

Broadband wireless communication users for 5G networks are primarily implemented in a complicated environment; the complex environment of time-varying multi-path propagation characteristics will seriously affect the performance of communication. One of the core technologies to overcome this problem is to introduce the environment adaptive technique--time reversal in the wireless link. Further, the problem of a Wiretap Channel in physical layer security research has become a popular research topic in recent years. To resolve the physical layer wiretap channel and multi-path fading problems in wireless channels, a novel concept of combining time reversal technology with physical layer security technology is proposed. In this paper, a physical layer secure transmission scheme based on the joint time reversal technique and artificial noise at the sending end is proposed for the wireless multi-path channel. First, in a typical wiretap channel model, the time reversal technique is used to improve the security of the information transmission process by using the properties of spatial and temporal focusing. Second, as the information is easily eavesdropped near the focus point, artificial noise is added to the sending end to disrupt the eavesdropping capability of the eavesdropper. Finally, due to the complexity of the multi-path channels, the influence of the antenna correlation on the system security performance is considered. Compared with the existing physical layer security schemes, theoretical analysis and simulation results show that the proposed scheme has a higher secrecy signal-to-noise ratio, a higher rate of secrecy, and a lower bit error rate of legitimate user.

Performance Analysis of New Spectrum Sensing Scheme Using Multiantennas with Multiuser Diversity in Cognitive Radio Networks

The spectrum detection (SD) is a critical step in cognitive radio (CR) to identify the available spectrum and avoid interference and harm to primary users (PUs). Nonetheless, the practical detection process is often compromised with problems of receptors uncertainty, shadows, and multipath fading. To overcome these problems, a cooperative SD scheme is proposed by exploiting the system multiantenna (MUA) with the multiuser diversity (MUD). The SD gives unlicensed secondary users (SUs) the opportunity to use the licensed spectral band until the PU makes its appearance. By allowing the cooperation between the SUs of the same spectral band, the time of the detection is reduced and increases the general dexterity, which is the strong point of cooperative SD. In this paper, we proposed an SD scheme using a new MUA design. The scheme proposed is a clear difference compared to other systems because in this design weight of quantification is multiplied by each receiving antenna. The scheme has the ability to detect low‐level signals to facilitate sharing between the SU and PU system. The numerical results are made to prove the performance of the proposed system compared to the conventional system. The results obtained confirm the efficiency of the proposed scheme.

ANALISIS MIMO UNTUK PENINGKATAN KAPASITAS SISTEM SELULER 4G LTE PADA SISTEM KOMUNIKASI HIGH ALTITUDE PLATFORM STATION

The development of technology has opened up a new wireless infrastructure to complement the satellite and terrestrial networks. High Altitude Platforms (HAPs) is a communications infrastructure that uses air balloon as a solution between terrestrial and satellite communications systems with medium coverage and low cost o f launching and maintenance. HAPs can be joined with a Long Term Evolution (LTE) technology standardized by the Third Generation Partnership Project (3GPP). LTE uses orthogonal frequency division multiplexing (OFDM) technology for downlink. OFDM technology is a technology that uses multicarrier and bring the data in parallel and the bandwidth is divided into several subcarrier. To improve the performance of LTE in an increase in capacity, coverage, and speed of data, then it can use MIMO techniques. MIMO is a technique using multiple antenna transmitter and receiver antennas that are used to overcome the problem of multipath fading and increase the capacity of the system to be serviced. MIMO support the achievement of high transmission speed. In the simulation, signals generated by the modified jakes model into a ricean channel using the K factor 1.41, 1.99, 2.33, 2.66, 4.61, 6.35, 9.21, 12.15, 16.77 dB with elevation angle of 1 0 ° to 90°. The larger the K factor, the smaller the shift doppler at each speed. Elevation angle have a relationship to the coverage area of HAPs, the smaller the elevation angle of the wider the coverage area, and the higher the position, the wider HAPs coverage area too. In ergodic capacity, the smaller the K factor, the smaller the elevation angle so that the capacity is also greater. System without estimation for the K factor o f 1.41dB and K 9.21dB is necessary for channel estimation and the Bit Error Rate (BER) o f the same system that made channel estimation has a better performance compared with the existing channel without estimation with the SNR improvement o f about 18 dB.

Performance assessment of precoded OFDM using discrete cosine-based DOST transform

Orthogonal frequency division multiplexing (OFDM) is conceivably the most reliable as well as most spectrally efficient transmission technique investigated so far for communication-oriented applications. By virtue of its orthogonal multi-carrier transmission scheme, it provides a sound robustness against the problem of multipath fading. Despite all these advantages, High peak-to-average power ratio (PAPR) is a major bottleneck that degrades the performance of OFDM. In this, research article an innovative precoding method has been proposed based on Discrete Cosine-based DOST (DCST) to lessen the High PAPR values in OFDM systems. DCST, which is a variant of Discrete Orthonormal Stockwell Transform (DOST), helps to reduce the PAPR values by virtue of orthonormal basis, multiple scales, and an absolutely referenced phase. The proposed scheme reduces the PAPR as well as improves the BER performance significantly without increasing the system complexity that much. The proposed system has been simulated on MATLAB and simulation clearly shows that the conventional FFT based OFDM is outperformed by on both the aspects i.e. PAPR reduction as well as BER performance enhancement.

An Efficient Course Resolution Multiple-Receiver Approach for Reception of Slow Fading Signals in Digital Wireless Communication Systems

Multiple-receiver digital wireless communication systems employ several receivers and a digital central receiver with data fusion to reduce the effect of multipath fading problems. The multiple receiver observations are processed at individual receivers and sent to a digital central receiver. The digital central receiver fuses all the individual receiver data to form global data on which symbol was transmitted. In this study, an efficient course resolution multiple-receiver approach for reception of slow fading signals in digital wireless communication systems is proposed. Each individual receiver observation is represented by course resolution data rather than high resolution data. The proposed approach is investigated for the case of no coherent frequency-shift keying in slow Rayleigh fading and additive Gaussian noise. The performance of the proposed approach is evaluated and compared to that of the optimum low resolution and high resolution approaches. Simulation results indicate that the proposed course resolution approach is efficient and cost effective. The results also indicate that the proposed approach can be used instead of high resolution approach without noticeable performance degradation which highly simplifies the construction and design of the digital wireless communication systems.

A Hybrid Mimo Technique for Better Ber in High Data Rate Wireless Communication System

The need for high data rate and better quality of service in wireless communications has become imperative in the past few years judging by user demand. Obtaining these requirements has become very challenging for wireless communication systems due to the problems of channel multi-path fading, higher power and bandwidth limitations. One of the most promising solutions to this problem is the Multiple Input Multiple Output (MIMO) system. This paper proposed a combined spatial multiplexing MIMO scheme with beamforming for high data rate wireless communication. The proposed transmission scheme combines the benefits of both techniques resulting in the system ability to transmit parallel data streams as well as provide beamforming gain. Actually, these diverse techniques, share the same requirement of multiple antenna elements, but differ in the antenna element spacing necessary for the different schemes to work. Thus, smart antenna arrays were proposed as a possible solution and were adopted at both the transmitter and the receiver. The proposed hybrid technique provides better Bit Error Rate (BER) performance than the conventional MIMO, spatial multiplexing or beamforming technique alone under the same simulation environment.

On the Research of Adaptive Frequency Hopping in the Wireless Communication

The multipath fading and interference problems in the wireless communication lead to the link quality decrease severely. However, the conventional frequency hopping scheme cannot solve the problems in an effective way. Adaptive frequency hopping scheme, which is based on the automatically link quality analysis, can avoid the bad frequencies and guarantee the desired level of channel quality. The system is analyzed based on the adaptive frequency hopping model equipped with link quality analyzer which is different from the traditional one. In the paper, some newly proposed adaptive frequency hopping schemes have been summarized, which provide an important reference for the practical application.

Avoiding Self Nulling by Using Linear Constraint Minimum Variance Beamforming in Smart Antenna

The beam forming technique is important in smart antenna systems to enhance the data rates, null steering and coverage. This study presents two methods of beamformeing algorithm; Minimum Variance Distortion less Response (MVDR) and Linear Constraint Minimum Variance (LCMV). MVDR and LCMV techniques form radiation beams based on the received weight vector of the desired signal. The LCMV technique is found to be efficient than the MVDR in self-null even if the interference signal is closer from the desired signal. Simulation has been carried out to validate these two techniques. The four elements of the linear array smart antenna are used in our simulation program with the operation frequency around 2.3 GHz, noise power 0.5dB and the spacing between elements is 0.5 λ. The result of the simulation reveals that both the modes are capable of providing high output power; however they need the direction of all the incoming sources, which is practically difficult to obtain. Nevertheless the MVDR beam forming minimizes the multi-path fading problem, by adding the multi-path signal, which increases the strength of the desired signal and nullifies the interference.

Design and Implement of the Out-of-Position Alarm System Based on CC2430

The paper put forward a detail design of the out-of-position alarm system based on ZigBee technology and communication chip CC2430 to protect valuables from leaving safe position. It introduced the hardware and software design of the system, implemented short-range wireless communication, established the functional relationship between received signal strength indication (RSSI) and wireless communication distance, solved the problem of multipath fading by software method. Then it presented a series of experiments to prove the system can steadily communicate information to meet security requirement.

A Frequency Diverse Gen2 RFID System with Isolated Continuous Wave Emitters

The “Gen2” specification for UHF passive RFID systems released by EPCglobal has become an intense research interest. A Gen2 tag derives its power from the RF wave emitted by a Gen2 RFID reader and responds its modulated backscatter signals to the reader. Due to the large propagation loss, the accessible range of a Gen2 tag is hence limited. Moreover, the readability of a Gen2 tag is often influenced by the multipath fading problem. In order to mitigate the problems, a multi-carrier UHF passive RFID system utilizing the frequency diverse backscatter ability of a Gen2 tag is proposed in a prior work. In this work, a thorough analysis of the system is given. Especially, the appropriate powers of the transceiver and CWEs are derived to make the system more feasible in practical applications.

The implementation of channel diversity in mobile software radio receivers

A novel channel diversity concept is proposed and demonstrated, which avoids receiving signal deterioration due to multipath fading in mobile receivers. The system is based on coherent superposition of the signals received from several transmitters supplying the same information at different frequencies. Based on a software radio architecture this concept may increase the quality of mobile reception in modern car receivers considerably. Compared with multiantenna-receivers which overcome the multipath fading problem by simultaneously receiving the same program with several antennas, the proposed solution is advantageous, since it requires only a single antenna.

Time statistics of propagation over the ocean surface: a numerical study

Temporal evolution of the ocean surface affects the received signal characteristics in a shipboard communication system. Predicting these time-varying properties is important in studying multipath fading problems. A statistical channel description to the second order is provided by knowledge of the coherent and incoherent power levels as well as the power spectrum of the received field. Several other time-dependent properties of a Gaussian channel can be determined from these statistics. In this paper, a method of moments (MoM) model for propagation over a one-dimensional (1D) time-evolving, perfectly conducting rough surface is applied to numerically study time statistics of propagation over the ocean. The ocean surface is described by a Pierson-Moskowitz spectrum and evolves in time according to a linear hydrodynamic dispersion relation. Due to the large size of propagation geometries in terms of the electromagnetic wavelength, an efficient numerical method is required to complete the simulation in a reasonable time. The recently developed forward-backward method with a novel spectral acceleration (F-B/NSA) technique is applied and enables time-evolving simulations for many realizations to be calculated so that reasonable statistics are obtained. Numerically obtained results for the coherent and the incoherent powers are illustrated. These results are compared with available analytical approximations to investigate the success of the approximate methods. Particular emphasis is placed on comparison with the Kirchhoff approximation, which provides reasonable predictions for smoother surface profiles and larger grazing angles.

Adaptive antenna array utilizing the conjugate gradient method for multipath mobile communication

This paper addresses a multipath fading problem occurring in mobile communications. At each antenna element, there arrives a number of clusters of signals each of which consists of a large number of signal components with their own arrival angles. The clusters are distinguished from each other by distinct group delays. This paper suggests a new efficient method of eliminating the multipath fading that can be used regardless of modulation technique. Since the problem is formulated independently from the arrival angle of each signal component, the array can resolve the multipath effects with a reasonable number of antenna elements even when there exist a large number of signal components. The angles of arrival may be distributed very closely to each other. In fact, the array designed in this paper can reduce the multipath effects once the number of antenna elements is equal to the number of distinct clusters. The new method utilizes a modified conjugate gradient method (CGM) for iteratively computing the optimal weights of the antenna elements. To generate the excitation vector which is required by the CGM, it is assumed that a set of known symbols are sent at each frame. This paper includes many practical examples of various PSKs and 16QAM, and the array performances are shown in many different signal environments in terms of bit-error-rate (BER) performance. From the extensive analysis and various computer simulations, we conclude that the CGM shown in this paper is suitable to adapt for an antenna array in an efficient way for mobile communication.