scholarly journals Hierarchical beam alignment in SU-MIMO terahertz communications

2021 ◽  
Vol 2 (7) ◽  
pp. 63-80
Author(s):  
Yifei Wu ◽  
Johannes Koch ◽  
Martin Vossiek ◽  
Wolfgang Gerstacker
Keyword(s):  
Line Of Sight ◽  
Noise Power ◽  
High Data ◽  
Single Carrier ◽  
Terahertz Communications ◽  
Optimal Beam ◽  
Speed Up ◽  
Single User ◽  
Simulation Results ◽  
Propagation Scenario

Single-Carrier Frequency Division Multiple Access (SC-FDMA) is a promising technique for high data rate indoor Terahertz (THz) communications in future beyond 5G systems. In an indoor propagation scenario, the Line-Of-Sight (LOS) component may be blocked by the obstacles. Thus, efficient THz SC-FDMA communications require a fast and reliable Beam Alignment (BA) method for both LOS and Non-Line-Of-Sight (NLOS) scenarios. In this paper, we first adopt the hierarchical discrete Fourier transform codebook for LOS BA, and introduce the hierarchical k-means codebook for NLOS BA to improve the beamforming gain. Simulation results illustrate that the hierarchical DFT codebook and the hierarchical k-means codebook can achieve the beamforming gain close to that of the maximum ratio transmission in LOS and NLOS cases, respectively. Based on these two codebooks, we propose a Multi-Armed Bandit (MAB) algorithm named Hierarchical Beam Alignment (HBA) for single-user SC-FDMA THz systems to reduce the BA latency. HBA utilizes a hierarchical structure in the adopted codebook and prior knowledge regarding the noise power to speed up the BA process. Both theoretical analysis and simulation results indicate that the proposed BA method converges to the optimal beam with high probability for both the hierarchical DFT codebook and the hierarchical k-means codebook in the LOS and NLOS scenarios, respectively. The latency introduced by HBA is significantly lower when compared to an exhaustive search method and other MAB-based methods.

scholarly journals Efficient OFDM transceiver design for VLC sys-tems in fading channel

2018 ◽  
Vol 7 (1.8) ◽  
pp. 245
Author(s):  
Jayakumari J ◽  
Rakhi K J
Keyword(s):  
Fading Channels ◽  
Bit Error Rate ◽  
Fading Channel ◽  
Visible Light Communication ◽  
Communication Security ◽  
Rf Systems ◽  
High Data ◽  
Data Rates ◽  
Simulation Results ◽  
Rich Spectrum

With the widespread effective usage of LEDs the visible light communication (VLC) system has brought out an increasing interest in the field of wireless communication recently. VLC is envisioned to be an appealing substitute to RF systems because of the advantages of LEDs such as high communication security, rich spectrum, etc. For achieving bearable inter symbol interference (ISI) and high data rates, OFDM can be employed in VLC. In this paper, the performance of VLC system with popular unipolar versions of OFDM viz. Flip-OFDM and ACO-OFDM is analyzed in fading channels. From the simulation results it is seen that the Flip-OFDM-VLC system outperforms the ACO-OFDM-VLC system in terms of bit error rate and is well suited for future 5G applications.

scholarly journals Stability and Manoeuvrability Simulation of a Semi-Autonomous Submarine Free-Running Model SUBOFF with an Autopilot System

2021 ◽  
Vol 11 (1) ◽  
pp. 410
Author(s):  
Yu-Hsien Lin ◽  
Yu-Ting Lin ◽  
Yen-Jun Chiu
Keyword(s):  
Optimal Control ◽  
Experimental Tests ◽  
Degree Of Freedom ◽  
Line Of Sight ◽  
Pd Controller ◽  
Free Running ◽  
Simulation Results ◽  
Guidance Algorithm ◽  
Logic Operations ◽  
Six Degree Of Freedom

On the basis of a full-appendage DARPA SUBOFF model (DTRC model 5470), a scale (λ = 0.535) semi-autonomous submarine free-running model (SFRM) was designed for testing its manoeuvrability and stability in the constrained water. Prior to the experimental tests of the SFRM, a six-degree-of-freedom (6-DOF) manoeuvre model with an autopilot system was developed by using logic operations in MATLAB. The SFRM’s attitude and its trim polygon were presented by coping with the changes in mass and trimming moment. By adopting a series of manoeuvring tests in empty tanks, the performances of the SFRM were introduced in cases of three sailing speeds. In addition, the PD controller was established by considering the simulation results of these manoeuvring tests. The optimal control gains with respect to each manoeuvring test can be calculated by using the PID tuner in MATLAB. Two sets of control gains derived from the optimal characteristics parameters were compared in order to decide on the most appropriate PD controller with the line-of-sight (LOS) guidance algorithm for the SFRM in the autopilot simulation. Eventually, the simulated trajectories and course angles of the SFRM would be illustrated in the post-processor based on the Cinema 4D modelling.

scholarly journals Interference Mitigation for Visible Light Communications in Underground Mines Using Angle Diversity Receivers

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 367 ◽  
Author(s):  
Pablo Palacios Játiva ◽  
Milton Román Cañizares ◽  
Cesar A. Azurdia-Meza ◽  
David Zabala-Blanco ◽  
Ali Dehghan Firoozabadi ◽  
...  
Keyword(s):  
Visible Light ◽  
Mine Working ◽  
Channel Model ◽  
Underground Mining ◽  
Cumulative Distribution ◽  
Line Of Sight ◽  
Delay Spread ◽  
Noise Power ◽  
Working Face ◽  
Angle Diversity

This paper proposes two solutions based on angle diversity receivers (ADRs) to mitigate inter-cell interference (ICI) in underground mining visible light communication (VLC) systems, one of them is a novel approach. A realistic VLC system based on two underground mining scenarios, termed as mining roadway and mine working face, is developed and modeled. A channel model based on the direct component in line-of-sight (LoS) and reflections of non-line-of-sight (NLoS) links is considered, as well as thermal and shot noises. The design and mathematical models of a pyramid distribution and a new hemi-dodecahedral distribution are addressed in detail. The performances of these approaches, accompanied by signal combining schemes, are evaluated with the baseline of a single photo-diode in reception. Results show that the minimum lighting standards established in both scenarios are met. As expected, the root-mean-square delay spread decreases as the distance between the transmitters and receivers increases. Furthermore, the hemi-dodecahedron ADR in conjunction with the maximum ratio combining (MRC) scheme, presents the best performance in the evaluated VLC system, with a maximum user data rate of 250 Mbps in mining roadway and 120 Mbps in mine working face, received energy per bit/noise power of 32 dB and 23 dB, respectively, when the bit error rate corresponds to 10 − 4 , and finally, values of 120 dB in mining roadway and 118 dB in mine working face for signal-to-interference-plus-noise ratio are observed in a cumulative distribution function.

Performance of LED for line-of-sight (LoS) underwater wireless optical communication system

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Alaa G. Nasser ◽  
Mazin Ali A. Ali
Keyword(s):  
Optical Communication ◽  
Link Quality ◽  
Line Of Sight ◽  
Modulation Scheme ◽  
Underwater Communication ◽  
Optical Communication System ◽  
High Data ◽  
Wireless Optical Communication ◽  
Noise Rate ◽  
Wireless Optical Communications

AbstractUnderwater wireless optical communications (UWOC) recently emerge as a solution to the problem of underwater communication for link with a high data rate, low delay, safety, and high immunity. In this study, the line of sight (LoS) method based on LED used for UWOC with different modulation schemes. The bit error rate (BER), signal-to-noise rate, and quality factor are used for assessing system performance and link quality. Besides the effect of transmitting angle, distance link (d), and transmitting power (PT) are analysed. Results show that 8-pulse position modulation (PPM) is the best modulation scheme for achieving a good link in the LoS method.

The Ship Track Keeping With Roll Reduction Using a Multiple-States PD Controller on the Rudder Operation

2008 ◽  
Vol 45 (01) ◽  
pp. 21-27
Author(s):  
Ming-Chung Fang ◽  
Jhih-Hong Luo
Keyword(s):  
Numerical Model ◽  
Line Of Sight ◽  
Pd Controller ◽  
Input Multiple Output ◽  
Maneuvering In Waves ◽  
Single Input ◽  
Reduction Function ◽  
Simulation Results ◽  
Guidance Technique ◽  
Present Simulation

The paper presents a nonlinear hydrodynamic numerical model with multiple-states proportional-derivative (PD) controllers for simulating the ship's tracking in random sea. By way of the rudder operation, the track-keeping ability of the PD controller on the ship is examined using the line-of-sight (LOS) guidance technique. Furthermore, the roll-reduction function using the rudder control is also included in the PD controller. From the present simulation results, the single-input multiple-output (SIMO) heading/roll PD controller including LOS technique developed here indeed works, either for the roll reduction or for track keeping while the ship is maneuvering in waves.

scholarly journals Impact of accelerometer based in physical layer wireless networks

2018 ◽  
Vol 7 (2.5) ◽  
pp. 15
Author(s):  
Zuhanis Mansor ◽  
Muhammad Khairulanwar bin Zulkafli
Keyword(s):  
Wireless Communication ◽  
Landscape Position ◽  
Line Of Sight ◽  
Noise Power ◽  
Signal Power ◽  
Propagation Channel ◽  
Signal To Noise ◽  
Downlink Throughput ◽  
The Impact ◽  
Non Line Of Sight

The initial deployments of antenna in the handset consist of fixed non-rotated antenna for transmitting and receiving the signal in the wireless communication scenario. However, link correlation at the UE shows very bad performance when the handset rotates in landscape position. This paper evaluates the impact of accelerometer on the downlink propagation channel of 3G smartphone for non-line-of-sight links. The performance average received signal power is studied for user equipment. Results show that the exploitation of an accelerometer provide better performance in terms of received signal power when the handset rotated from portrait to landscape position. It can be concluded that the deployment of accelerometer can be used to improve existing 3G smartphone received signal. Results also indicate that accelerometer can be used to improve downlink throughput since the signal-to-noise-power is increased by approximately 16%.

Long-Term Evolution (LTE)

Data Mining ◽  
2013 ◽  
pp. 336-365
Author(s):  
Bing He ◽  
Bin Xie ◽  
Sanjuli Agrawal ◽  
David Zhao ◽  
Ranga Reddy
Keyword(s):  
Cellular Networks ◽  
Orthogonal Frequency Division Multiplexing ◽  
New Technologies ◽  
Network Capacity ◽  
Long Term Evolution ◽  
High Data ◽  
Term Evolution ◽  
Input Multiple Output ◽  
Speed Up

With the ever growing demand on high throughput for mobile users, 3G cellular networks are limited in their network capacity for offering high data services to a large number of users. Consequently, many Internet services such as on-demand video and mobile TV are hard to be satisfactorily supported by the current 3G cellular networks. 3GPP Long Term Evolution (LTE) is a recently proposed 4G standard, representing a significant advance of 3G cellular technology. Attractively, LTE would offer an uplink data speed up to 50 Mbps and a downlink speed up to 100 Mbps for various services such as traditional voice, high-speed data, multimedia unicast, and multimedia broadcasting. In such a short time, it has been broadly accepted by major wireless vendors such as Verizon-Vodafone, AT&T, NTT-Docomo, KDDI, T-Mobile, and China Mobile. In order for high data link speed, LTE adapts new technologies that are new to 3G network such as Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO). MIMO allows the use of more than one antenna at the transmitter and receiver for higher data transmission. The LTE bandwidth can be scalable from 1.25 to 20 MHz, satisfying the need of different network operators that may have different bandwidth allocations for services, based on its managed spectrum. In this chapter, we discuss the major advance of the LTE and its recent research efforts in improving its performance. Our illustration of LTE is comprehensive, spanning from the LTE physical layer to link layer. In addition, the LTE security is also discussed.

Improving Energy Efficiency and Throughput in Heterogeneous Mobile Ad Hoc Networks

2011 ◽  
pp. 37-49
Author(s):  
Manu J. Pillai ◽  
M. P. Sebastian
Keyword(s):  
Ad Hoc ◽  
Transmission Rate ◽  
Mac Protocol ◽  
Signal Loss ◽  
High Data ◽  
Communication Links ◽  
Adhoc Networks ◽  
Simulation Results ◽  
Demand Routing ◽  
Hoc Networks

The nodes are expected to transmit at different power levels in heterogeneous mobile adhoc networks, thus leading to communication links of different length. Conventional MAC protocols that unconditionally presume that links are bi-directional and with unvarying energy distribution may not succeed or execute badly under such circumstances. Interference and signal loss resulting out of distance and fading diminish the entire throughput attained in heterogeneous networks to a greater extent. This article presents a MAC protocol, which adaptively transmits data frames using either the energy efficient nodes or a list of high data rate assistant nodes. In addition, a cross-layer based energy level on-demand routing protocol that adaptively regulates the transmission rate on basis of congestion is projected as well. Simulation results illustrate that the proposed protocols considerably diminish energy consumption and delay, and attain high throughput in contrast with the Hybrid MAC and traditional IEEE 802.11 protocols

QoS-Constrained Resource Allocation Scheduling for LTE Network

2015 ◽  
Vol 4 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Hung-Chin Jang ◽  
Yun-Jun Lee
Keyword(s):  
Resource Allocation ◽  
Data Transmission ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
High Mobility ◽  
System Throughput ◽  
Frequency Division ◽  
High Data ◽  
Single Carrier ◽  
Allocation Method

The goal of LTE (Long Term Evolution) is to provide high data transmission rate, scalable bandwidth, low latency, high-mobility, etc. LTE employs OFDM (Orthogonal Frequency Division Multiplexing) and SC-FDMA (Single Carrier - Frequency Division Multiple Access) for downlink and uplink data transmission, respectively. As to SC-FDMA, there are two constraints in doing resource allocation. First, the allocated resource blocks (RBs) should be contiguous. Second, those of the allocated RBs are forced to use the same modulation technique. The aim of this research is to propose a QoS-constraint resource allocation scheduling to enhance data transmission for uplink SC-FDMA. The proposed scheduling is a three-stage approach. In the first stage, it uses a time domain scheduler to differentiate user equipment (UE) services according to their distinct QoS service requirements. In the second stage, it uses a frequency domain scheduler to prioritize UE services based on channel quality. In the third stage, it limits the number of times of modulation downgrade of RBs allocation in order to enhance system throughput. In the simulations, the proposed method is compared to fixed sub-carrier dynamic resource allocation method and adaptive dynamic sub-carrier resource allocation method. Simulation results show that the proposed method outperforms the other two methods in terms of throughput, transmission delay, packet loss ratio, and RB utilization.

Sign in / Sign up

Export Citation Format

Share Document