Proposed Transmission System Research Articles

Hybrid tree-and-multiple-ring radio-over-fiber transmission system for a 5G network in metropolitan areas

What we believe to be a novel radio-over-fiber (RoF) transmission system with a hybrid tree-and-multiple-ring network structure is developed and experimentally demonstrated to support broadband wireless signal transmission among the central office (CO) and densely distributed 5G base stations (BS) in urban areas. With the assistance of an advanced network structure and a unique single-line bidirectional optical add/drop multiplexer (SBOADM), the transmission system can utilize a hybrid tree-and-ring-topology fiber network to simultaneously support multiple 5G BS-Groups constructed as sub-ring-networks. Furthermore, the system manager is able to simultaneously utilize wavelength/time division multiplexing techniques to support the connected BSs and to dynamically embed extra sub-ring-networks to the main-ring-network or extra BSs to the sub-ring-network by using the RoF transmission system. Needing no backup fiber link, the transmission system enjoys intrinsic robust resilience against fiber link failures. Experimental results proved that the proposed RoF transmission system enables prompt recovery of interrupted optical fiber connection and guarantees the expected quality of service (QoS) by adjusting a few preinstalled optical switches when fiber link failure happens in the main-ring-network, in each sub-ring-network, or even in both of the above scenarios. The induced power penalty for maintaining unchanged bit error rate performance is less than 2 dB. In sum, the proposed transmission system proves to be a great network architecture suitable for supporting 5G signal transmission between the CO and BSs in an urban area due to the dynamically extensible network size and the well-protected transmission that ensures the QoS by simple operation.

Efficient Index Modulation-Based MIMO OFDM Data Transmission and Detection for V2V Highly Dispersive Channels

Vehicle-to-vehicle (V2V) communication networks are based on vehicles that wirelessly exchange data, traffic congestion, and safety warnings between them. The design of new V2V systems requires increasingly energetically and spectrally efficient systems. Conventional multiple-input–multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems have been used successfully for the last decade. However, MIMO-OFDM systems need to be improved to face future communication networks in high-mobility environments. This article proposes an efficient index modulation (IM)-based MIMO-OFDM system for V2V channels. The proposed transmission system is evaluated in high Doppler-spread channels. The results demonstrate that the proposed scheme reduces the required computational complexity in data detection and exhibits gains of up to 3 dB in bit error rate (BER) performance when compared to the conventional MIMO-OFDM system under the same conditions and parameters, along with achieving superior spectral efficiency. The results show the viability of implementing the proposed system in practical applications for high-transmission-rate V2V channels.

Index Coded - NOMA in Vehicular Ad Hoc Networks

The demand for multimedia services is growing day by day in vehicular ad hoc networks (VANETs), resulting in high spectral usage and network congestion. Non-orthogonal multiple access (NOMA) is a promising wireless communication technique to solve the problems related to spectral efficiency effectively. The index coding (IC) is a powerful method to improve spectral utilization, where a sender aims to satisfy the needs of multiple receivers with a minimum number of transmissions. By combining these two approaches, in this work, we propose a novel technique called index coded NOMA (IC-NOMA), where we apply NOMA techniques on index coded data to reduce the number of transmissions further. This work shows that the IC-NOMA system demands a specific design for index codes to reap the advantages of NOMA. We have done the feasibility analysis of the proposed method in a general scenario and proposed an index code design to integrate IC over NOMA for the best efficiency. Through detailed analytical studies it is validated that the proposed transmission system provides improved spectral efficiency and power saving compared to conventional IC systems.

Technical and Economic Analysis of an HVDC Transmission System for Renewable Energy Connection in Afghanistan

Aged and insufficient domestic power plants and insecure, unreliable and expensive power imports pose significant challenges for the power sector of Afghanistan. On the other hand, due to the absence of a suitable transmission grid, the internal renewable energy resources are not adequately developed, despite their abundant resource potential throughout the country. This paper proposes a voltage source converter (VSC)-based high-voltage direct current (HVDC) transmission link to connect the Herat province in the west, which has huge solar and wind energy potential, to Kabul, the capital of the country and the main load center. A techno-economic analysis of this HVDC against high-voltage alternating current (HVAC) technology was performed to determine the suitability and effectiveness of the proposed transmission system. The active, reactive and corona losses were calculated as the technical parameters and the discounted cash flow (DCF) method was deployed to economically compare both technologies. The outcomes of the paper disclose that the implementation of this transmission project is techno-economically feasible, and can result in the energy security and economic stability of the country.

Design of reliable video image transmission system for underwater vehicle

In order to improve the transmission performance of underwater vehicle motion video image, a reliable transmission system of underwater vehicle motion video image is designed. The hardware part of the system includes the design of the transmission server and the design of the transmission client; the software part of the system mainly includes two parts: compression processing and lossless transmission of the motion video image of the underwater vehicle, which completes the software design of the system and realises the design of the whole system. The test results show that the proposed transmission system has good transmission performance for the motion video image of the vehicle in shallow water.

Power efficient Space Division Multiplexing–Wavelength Division Multiplexing system using multimode EDFA with elevated refractive index profile

SummarySpace division multiplexing (SDM) is an endowment technology to increase the collective bandwidth of multimode transmission in wavelength division multiplexing (WDM) system. In this paper, four wavelength signals from 229.6 to 232.6 THz are transmitted. For each wavelength, three linearly polarized (LP) modes are multiplexed using SDM. These 12 LP modes are transmitted through four parallel Multimode Step Index (MSI) fibers and received by four optical network units (ONUs). A multimode erbium doped fiber amplifier (MMEDFA) with elevated refractive index profile (ERIP) is used as preamplifier to this SDM–WDM system. This ERIP is complying with ITU‐T G.651.1 standard fiber in dispersion performance. The pumping power of 10 mW is adequate for this MMEDFA which is very low and cost effective. LP modes are transmitted, and performance of proposed transmission system is evaluated in terms of spatial electric fields, pumping power requirement, output optical power, and bit error rate (BER).

Study on 1-THz Sine Waveguide Traveling-Wave Tube

In this article, a 1-THz traveling-wave tube (TWT) based on flat-roofed sine waveguide (SWG) slow wave structure (SWS) has been studied theoretically and experimentally, and parts of the component have been fabricated. First, the flat-roofed SWG SWS has been optimized for working at 1 THz, the normalized phase velocity is around 0.287, and the interaction impedance is over 3.5 Ω in the frequency range of 1.02-1.04 THz. Meanwhile, the performance of the designed TWT has been simulated, whose saturated output power is 720 mW and the corresponding gain is 28.57 dB. What is more, to decrease the transmission loss of the high-frequency structure, the input and output structures have been designed and a transition structure that transforms the waveguide to standard rectangular waveguide has been proposed. The simulation results show that the reflection coefficient of the novel proposed transmission system is less than -20 dB, and the insertion losses of the transition structure with the input and output waveguides are 2.45 and 1.68 dB, respectively. Finally, the designed SWS has been fabricated by deep reactive-ion etching (DRIE) and tested; S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> is generally less than -10 dB in the frequency range of 1020-1040 GHz.

Study of transmission system for compressed and encrypted image

An evolutionary asymmetric cryptosystem is proposed using QWT + SPIHT and AES. This system is based on the Quincunx wavelet transform coupled with progressive encoder SPIHT (QWT + SPIHT) and encrypted by the algorithm “Advanced Encryption Standard” (AES). The numerical results demonstrate that the proposed system is feasible and effective for encryption. The characteristics of the proposed transmission system are as follows. First, the progressive SPIHT encoder performs partial encryption on the compressed image and hash of the image to obtain secure deduplication of the image. Second, the use of the AES encryption algorithm can greatly improve security, such as an attack without phase recovery and information disclosure. The proposed method effectively prevents information leakage. However, adopting a Quincunx wavelet transformation reduces the amount of data, which is more conducive to data transmission and increases the practicability of the system.

Investigation of 340-Gbps terrestrial FSO link incorporating spectral-efficient DP-QPSK-PolSK hybrid modulation scheme

A high-capacity spectral-efficient dual-polarization quadrature phase-shift keying (DP-QPSK)-polarization shift-keying (PolSK) hybrid modulation scheme for terrestrial free-space optics (FSO) transmission link is proposed and investigated. A DP-QPSK signal modulated at 300 Gbps and a PolSK signal modulated at 40 Gbps are simultaneously transmitted using a single optical carrier over the FSO link. The proposed link performance is investigated under different weather conditions, where the bit error rate metric is used to evaluate the performance of the PolSK modulated signal and the error vector magnitude parameter is used for the DP-QPSK signal. The FSO link range and the required received power are carefully explored. The conducted numerical simulations of the proposed system showed reliable 340-Gbps data transmission over link ranges varying from 1.6125 to 50 km depending on the weather conditions. The impact of the channel scintillation due to atmospheric turbulence is also investigated. The proposed high-speed FSO transmission system offers a promising solution for high-bandwidth hungry systems used for the internet of things, 5G, and smart cities. It can also be used in developing fronthaul/backhaul links for future wireless networks and optical access networks. The performance of the proposed transmission system is compared with recently published work in the literature.

Implementation of Multi-Wavelength Source for DWDM-PON Fiber Optical Transmission Systems

Abstract Four-wave mixing (FWM) is one of the well-known nonlinear optical effects (NOE), and it is considered as an adverse impact in fibre optical communication lines. This nonlinear optical effect as a productive one can be used in fibre optical communication systems for various optical processing functions, like wavelength conversion, high-speed time-division multiplexing (TDM), pulse compression, fibre optical parametric amplifiers (FOPA), etc. In most of the fibre optical communication systems, each data transmission channel requires one light source (e.g., laser) as a carrier, which can make these transmission systems expensive. For example, to provide operation of 4-channel dense wavelength-division-multiplexed (DWDM) system four separate lasers at specific operation wavelengths are needed. On the contrary, through the FWM effect, which can be obtained in highly nonlinear optical fibre (HNLF) by using two high-power pump lasers, the generation of new multiple carriers forming the laser array or a multi-wavelength source is possible. Accordingly, within the present research, we investigate the latter approach for FWM light source implementation in DWDM passive optical networks (DWDM-PONs). We analyse up to 16-channel 50 GHz spaced DWDM-PON system with a bitrate of up to 10 Gbit/s per channel, constructed on the basis of two high-power continuous wave (CW) pump lasers. We evaluate the system performance against the number of its channels by changing it from 4 to 16 and in each case find the most optimal HNLF fibre length (for a 4-channel system it is 0.9 km; for an 8-channel system – 1.39 km; and for a 16-channel system – 1.05 km) and laser pump powers (for a 4-channel system it is 20 dBm; for an 8-channel system – 24.1 dBm; and for a 16-channel system – 26.3 dBm). These optimal parameters were found in order to get the highest system performance, respectively, the lowest BER (threshold BER≤10−10), and minimal power fluctuations among FWM generated carriers. The obtained results show that the proposed transmission system can be a promising solution for next-generation high-speed PONs.

Hybrid Optical-Radio Transmission System Link Quality: Link Budget Analysis

From the last few decades' radio frequency (RF) spectrum remained attractive for wireless/wire-line applications. RF spectrum becomes dense and occupied, which makes its availability difficult to other broadband channels. Free space optical (FSO) communication, which was used for messaging/indication in the ancient days, now becomes more popular and attractive in the new era. The popularity of FSO is due to its freely available large spectrum, inherited secure links and ease of deployment. However, FSO link has to face certain challenges, e.g., line-of-sight (LOS) requirement, link attenuation due to atmospheric turbulence and severe weather conditions. To overcome the issues of FSO communication, hybrid optical-radio transmission system is proposed by which we can get maximum benefits of both spectrum. Considering the proposed transmission system link quality, link budget analysis is done in the presented work. Link budget design of transmission system is important to analyze and give recommendations.

A passively regulated full-toroidal continuously variable transmission

This work presents a novel self-regulated toroidal continuously variable transmission (ART-CVT) that features a passive control of the speed ratio, achieved with no need for supplementary actuation system. The proposed transmission system is based on a full-toroidal CVT topology which combines a specially shaped geometry of the conjugate profiles with a pre-load system to create a correlation between the speed ratio and the input torque. Such a solution is conceived to reduce the complexity that is usually associated with active regulated systems and it is envisaged to be applicable to low-power/low-cost systems such as small wind turbines, powered-two-wheelers, or bicycles. We illustrate a simplified mathematical model that is able to describe the response of the proposed ART-CVT in quasi-static steady-state operational conditions. Additionally, we propose a case-study in a realistic scenario: a design for an ART-CVT that matches the requirements of a low-power wind turbine coupled with a synchronous generator directly connected to the grid without additional power converters. The achieved results show that an ART-CVT is able to reach working conditions close to the maximum theoretical aerodynamic performance without any active regulation.

Loader power-split transmission system based on a planetary gear set

In hydraulic mechanical transmission loaders, a hydraulic torque converter can prevent an engine from stalling due to overloading of the loader during the spading process; however, the hydraulic torque converter also reduces the loader’s fuel economy because of its low transmission efficiency. To address this issue, the study designs an output-power-split transmission system that is applied to a hybrid loader. The designed transmission system removes the hydraulic torque converter in the power transmission system of a traditional loader and adopts a planetary gear set with a compact structure as the dynamic coupling element, thus allowing the output power of the loader to be split transmitted. During shoveling, the loader power-split transmission system based on a planetary gear set can prevent the motor from plugging and over-burning under conditions that ensure that the traction does not decrease. In addition, the transmission efficiency and loader fuel economy are higher in the proposed transmission system than in the power transmission system of a traditional loader. The test results show that the transmission efficiency of the designed system was 13.2% higher than that of the traditional hydraulic mechanical transmission loader.

System for Transmitting Reference Frequency and Time Signals to Measurement Resources of the Glonass Ground Complex by Optical Cable

We present a system of transmission of reference frequency and time signals to non-interrogating and interrogating measuring facilities of the ground-based GLONASS complex for control of onboard time scales of the navigation system spacecraft. The proposed transmission system is implemented using fiberopticcommunication lines. We present results of experimental studies of the error in the transmission of reference frequency and time signals using fiber-optic communication lines.

Electromagnetic Design and Analysis of a Novel Transmission System Supporting Multi-Path Power Flows for Electric Vehicles

This paper proposes a novel transmission system supporting multi-path power flows for electric vehicles (EVs). It mainly consists of a coaxial magnetic gear (CMG), a lock, a clutch, and two electric machines (EMs). The key feature of the CMG is that its modulating ring can rotate freely. One of the EMs is integrated with the CMG, which constitutes an integrated magnetic gear permanent magnet machine. And the other is connected to the inner rotor of the CMG through a clutch and a shaft with a lock. By toggling the clutch, controlling the states of the lock and the two EMs, the proposed transmission system can achieve flexible power splits. It is very interesting that one of the EM can play the role of a flywheel storage device when necessary, which is capable of buffering the energy from regenerative braking, so as to protect the battery. In this paper, the configuration of the transmission system is illustrated; its operating principle is elaborated. Then, the electromagnetic design is conducted to meet the demands arising from EVs. Finally, the electromagnetic performances are analyzed by using finite-element method, which verifies the rationality of the electromagnetic design.

Optimized Cross-Layered Unequal Error Protection for SPIHT Coded Wireless Video Transmission

Transmission of coded video over erroneous channels (e.g., Internet and wireless networks) is always a challenging task. Error control strategies, to combat the channel errors, are generally applied at individual network layers leading to inefficient utilization of resources. The cross-layer design has emerged as alternative for efficient utilization of the available resources, such as bandwidth, delay, and transmission power to provide best quality of the reconstructed video. Furthermore, to efficiently utilize the resources, cross-layer error control parameters need to be optimized. Since, the optimal error control parameters change with channel conditions, new optimal values need to be calculated every time the channel condition changes. However, optimization of the parameters at the time of video transmission requires very high computational processing power otherwise it may induce a large transmission delay which is intolerable in video communication. In this paper, we propose an optimized cross-layered unequal error protection (UEP) scheme targeted for hand-held devices which have low processing power, uses pre-computed look-up table (LUT) that stores the optimal cross-layer error control parameters for a range of channel conditions. LUT is constructed using offline optimization of the parameters. For real time video communication, given a channel condition, the corresponding error control parameters are read from a LUT and are passed to the corresponding network layers. Thus, the proposed transmission system is simple and delivers best end-to-end quality of the video. Simulation results show that the proposed cross-layered UEP system can achieve up to 14–17 dB and 2–4 dB improvement in video quality over individual application layer optimized UEPs in additive white Gaussian noise and fading channel respectively at very poor channel conditions. Furthermore, the proposed system outperforms other contemporary methods.

On the utility of MIMO multi-relay networks for modulation identification over spatially-correlated channels

The necessity to perfectly monitor the intercepted signals for spatially-correlated multiple-input multiple-output (MIMO) systems, involves modulation identification algorithms. In this paper, we present an algorithm dedicated to the modulation identification for correlated MIMO relaying broadcast channels with direct link using multi-relay nodes. By modeling spatially-correlated MIMO channels as Kronecker-structured and the imperfect channel state information of both the source-to-destination and the relay-to-destination errors as independent complex Gaussian random variables, we firstly derive the ergodic capacity of the proposed transmission system. It turns out that the ergodic capacities improve with the number of relay nodes. Based on a pattern recognition approach using the higher order statistics features and the Bagging classifier, we show that the probability to distinguish among M-ary shift keying linear modulation types without any priori modulation information is enhanced compared to the decision tree (J48), the tree augmented naive Bayes, the naive Bayes using discretization and the multilayer perceptron classifiers. We also study the effect of increasing the number of relay nodes. Numerical simulations show that the proposed algorithm using the cooperation of multi-relay nodes with the source node can avoid the performance deterioration in modulation identification caused by both spatial correlation and imperfect CSI.

Bidirectional optical single-sideband modulation and phase remodulation radio-on-fiber transport systems with fiber nonlinearity and injection-locked laser technology

We propose a bidirectional transmission system based on stimulated Brillouin scattering effect and injection-locked distributed feedback laser to achieve an optical single-sideband modulation for downlink transmission. We reuse the transmitted light through phase modulation for uplink transmission to avoid interference of both signals in a bidirectional transport. After a 25-km single-mode fiber transmission is completed, a sideband power ratio of >15 dB is observed in the downlink transmission, and the power penalty of the system is <1 dB. In our proposed bidirectional transmission system, the performances of bit error rate analysis are good.

Wireless data transmission using visual codes

In this paper, a new approach for wireless data transmission within an aircraft cabin is presented. The proposed application enables the transmission of data to a passenger’s user device. As wireless in-flight applications are subject to strict frequency and electromagnetic compatibility (EMC) regulations, the data is transferred by optical wireless transmission, specifically by two-dimensional visual codes. To this end, black-and-white or colored visual code sequences are displayed on the in-flight entertainment screen. These visual codes are captured by the built-in camera of the passenger’s mobile device and are decoded to reconstruct the transmitted data. In order to compensate for frame losses caused by effects like occlusion and motion blur, a temporal forward error correction coding scheme is applied. Transmission experiments within an Airbus A330 cabin mock-up demonstrate the functionality of the implemented system under realistic conditions such as ambient illumination and geometric configuration. Representative user devices are used for evaluation; specifically, a low-cost and a high-end smartphone are employed as receivers. Performance evaluations show that the proposed transmission system achieves data rates of up to 120 kbit/s per individual passenger seat with these user devices. As the user device has no physical connection to the sensitive on-board system, the proposed transmission system provides an intrinsic safety feature.

Exploiting joint synergy for actuation in a lower‐limb active orthosis

PurposeLower‐limb exoskeletons and powered orthoses are external devices that assist patients with locomotive disorders to achieve correct limb movements. Current batteries cannot meet the long‐term power requirements for these devices, which operate for long periods of time. This issue has become a major challenge in the development of these portable robots. Conversely, legged locomotion in animals and humans is efficient; to emulate this behaviour, biomimetic actuation has been designed attempting to incorporate elements that resemble biological elements, such as tendons and muscles, in the mechanical systems. The purpose of this paper is to present a mechanism that resembles a human tendon to achieve and utilise the synergic actuation of the leg joints.Design/methodology/approachIn this paper, we present a mechanism that resembles a human tendon to move the ankle joint and utilise the synergic actuation of hip and knee joints. Implementation of the proposed transmission system in the ATLAS active orthosis prototype allowed for a better ankle gait fit, which resulted in a more natural stride and, as expected, optimised energy consumption in the locomotion cycle and actuation energy requirements.FindingsThe fitted passive ankle motion provides toe‐off impulse, increases support force, and helps provide ground clearance.Originality/valueA synergetic underactuated movement in the ankle joint, implemented by two cables in each leg, improves the functionality of the device without increasing the leg weight and while maintaining a reduced size. To achieve a correct and efficient motion in the ankle of an active orthosis, two steel cables were attached in the ATLAS orthosis. These cables act as a synergic biarticular linkage and transfer motion from the hip and knee joints. Synergic ankle motion provides impulse in the toe‐off, increases support force, and provides ground clearance. These goals are achieved with low energy expenditure because of synergical actuation, and high inertia is prevented in the more distal limb.