Multibeam Transmitter Research Articles

Non-Orthogonal Transmission Techniques for Multibeam Satellite Systems

Non-orthogonal transmission is a promising technology enabler to meet the requirements of 5G communication systems. Seminal papers demonstrated that non-orthogonal multiplexing techniques outperform orthogonal schemes in terms of capacity, latency, and user fairness. Since it is envisioned that satellites will be an integral component of the 5G infrastructure, it is worth studying how satellite communication systems can benefit from the application of non-orthogonal transmission schemes as well. Contrary to common perception, current communications through a satellite present a different architecture and face different impairments than those in the wireless terrestrial links. In particular, this work aims to describe different non-orthogonal schemes that are suitable for the forward link (i.e., satellite to user). In contrast with the return link of the satellite (i.e., user to satellite), where the use of non-orthogonal transmission schemes has been widely studied, less effort has been devoted to the forward link. In light of this, this article provides an overview and a novel taxonomy that is based on the forward link of different non-orthogonal multibeam transmission schemes. Finally, guidelines that open new avenues for research in this topic are provided.

Multi-Beam Transmission and Dual-Band Cooperation for Control/Data Plane Decoupled WLANs

With dramatically increased data traffic, the traditional low-frequency (LF) wireless local area networks (WLAN) are facing several difficulties, particularly, limited available spectrum resources and low network efficiency. While the use of millimeter-wave (mmWave) could bring more spectrum, WLAN in high-frequency (HF) suffers poor reliability. In addition, the current distributed WLAN architecture and the coupled data and control planes lead to inefficient management and poor performance with increased network scale, which cannot meet the stringent requirements from diverse applications. In overcoming these difficulties, the control plane and data plane decoupled network architecture and sub-6 GHz and mmWave dual-band cooperation are considered to be the critical solutions to improve the system performance in 5th-Generation (5G) and beyond networks. Therefore, to improve the throughput and reliability of the future WLAN, we propose a control plane and data plane decoupled WLAN architecture in this paper that supports both sub-6 GHz and mmWave based on the existing control plane and data plane decoupled WLAN concept. Furthermore, new multi-beam transmission and sub-6 GHz and mmWave dual-band cooperation mechanisms are developed to improve the throughput and reliability in our proposed WLAN architecture. Performance analysis and simulation show that with the multi-beam transmission and sub-6 GHz and mmWave dual-band cooperation mechanisms in our proposed WLAN architecture, throughput and reliability are both significantly improved when compared with the traditional distributed WLAN architecture and operation mechanism.

Single Radio-Over-Fiber Link and RF Chain-Based 60 GHz Multi-Beam Transmission

An efficient multi-user transmission scheme at 60 GHz using a single-feed leaky wave antenna (LWA) and hence requiring only a single radio-over-fiber link and single RF chain is presented. A subcarrier multiplexed signal carrying different users’ data is transported over 2.2 km of optical fiber and then upconverted to the 60 GHz band for transmission to multiple spatially separated users through the beam steering characteristics of the LWA. An overall sum data rate, the combined rate from all users, of 10.6 Gb/s using 16-QAM modulation serving ten users over a transmission bandwidth of 3.05 GHz or 20 users with QPSK over 6.1 GHz span, is achieved experimentally. The theoretical sum data rates for 6.1 GHz bandwidth for different numbers of users are calculated, considering the SNR degradation due to the angularly dispersed LWA beam, showing that data rates over 30 Gb/s can be obtained. Finally, a system design that improves coverage and spectrum efficiency through operating multiple LWAs with a single RF chain is demonstrated.

Sequence Design for Multi-Beam Transmission from an Electronic Transmitter in Millimeter Wave Systems

Sequence Design for Multi-Beam Transmission from an Electronic Transmitter in Millimeter Wave Systems

Design and Implementation of Multi-beam Transmitter

The multi-beam sounding technology has been carrying out a revolution in underwater survey. Compared with traditional equipment’s, the multi-beam sounding system has a huge advantage in efficiency, accuracy and resolution. According to the beam-forming theory, the paper designs a phase-control signal formulation circuit based on FPGA (Field Programmable Gate Array), and the experiments show that the multi-beam transmitter has a high performance and can fully meet the needs.

Beam Management for Millimeter-Wave Beamspace MU-MIMO Systems

Millimeter-wave (mm-wave) communication has attracted increasing attention as a promising technology for 5G networks. One of the key architectural features of mm-wave is the possibility of using large antenna arrays at both the transmitter and receiver sides. Therefore, by employing directional beamforming, both mm-wave base stations (MBSs) and mm-wave user equipments (MUEs) are capable of supporting multi-beam simultaneous transmissions. However, most of the existing research results have only considered a single beam. Thus, the potentials of mm-wave have not been fully exploited yet. In this context, in order to improve the performance of short-range indoor mm-wave networks with multiple reflections, we investigate the challenges and potential solutions of downlink multi-user multi-beam transmission, which can be described as a beamspace multi-user multiple-input multiple-output (MU-MIMO) technique. We first exploit the characteristic of MBS/MUEs supporting multiple beams simultaneously to improve the efficiency of multi-user BF training. Then, we analyze the inter-user interference to avoid beam selection conflicts. Furthermore, we propose blockage control strategies and multi-user multi-beam power allocation solutions for the beamspace MU-MIMO. The theoretical and numerical results demonstrate that the beamspace MU-MIMO compared with single beam transmission can largely improve the rate performance and robustness of mm-wave networks.

Angular drift of the high current relativistic multi-beam in the hollow cylindrical waveguide

Multi-beam klystron (MBK) is a promising high power microwave device with the traits of high power, high efficiency, high frequency, etc. For the high power relativistic MBK, the multi-beam rotation around an axis may reduce the transmission efficiency obviously due to the effect of space electromagnetic field. In previous researches, the influence of mirror-image electromagnetic field is ignored, which can play a leading role in some cases. In this study, we present a method by taking into account the mirror-image effect to analyze the angular drift of multi-beam in the hollow cylindrical waveguide. The hollow cylindrical waveguide is a part of relativistic MBK such as input cavity and transition section, which is just behind the diode. In this method, the equation of the multi-beam angular drift is deduced and analyzed quantitatively. Based on the equation, the expression of the angular velocity about the multi-beam in the waveguide is derived, meanwhile the minimum equilibrium magnetic field, called Brillouin magnetic field, is obtained. To verify the effectiveness of the method, numerical simulations are carried out by the three-dimensional (3D) code and the results show good agreement with the theoretical results. The theoretical analysis and simulation results show that the mirror-image electromagnetic field can dominate the multi-beam angular motion in some conditions, especially when the number of the multi-beams and the distance between the conducting wall and the multi-beam are both small. In this case, the mirror-image electromagnetic field can be much higher than the self-induced electromagnetic field. Nevertheless, as the the number of the multi-beams or the distance between the conducting wall and the multi-beam increases, the mirror-image electromagnetic field decreases and approaches to zero rapidly and the self-induced electromagnetic field controls the angular movement. Interestingly, in general cases, it is found that the change rate of the angular speed is not related to the number of multi-beams, nor the radius of waveguide, nor the distance between the multi-beam, nor waveguide, etc, except for the accelerating voltage. In addition, we experimentally investigate the angular drift of the multi-beam at a voltage of about 670 kV, current of about 7 kA and length of waveguide about 100 mm. The experimental results show that the multi-beam distorts obviously, which changes the beam spot shape from circle to ellipse. To solve this problem, we simultaneously investigate the multi-beam emission and transmission in simulation experiment. The analogue results not only reveal that the distortion is mainly caused by the emission of the multi-cathode rods, but also provide a new phenomenon that the angular drift distance in the accelerating gap of the diode is twice as large as that in the cylindrical hollow waveguide due to the low beam speed along the axis and high electrostatic field in the accelerating region. It is also found that the distortion is more evident as the rod radius decreases. Furthermore, we propose an optimization design to improve the relativistic multi-beam system by inclining the multi-cathode rods, which is proved to be effective by simulation. This study could provide theoretical basis for studying the relativistic MBK.

Preparation and performance of 1–3 multi-element piezoelectric composites

A 1–3 type multi-element piezoelectric composite was fabricated using silicon as decoupling material to ensure the independence of transmitted acoustic beam and strengthen the signal power. The consistency and acoustic coupling of all elements in the composite were investigated. The results showed that the piezoelectric, dielectric and ferroelectric properties, and the electromechanical coupling properties of each element in the composite exhibited excellent consistency. The good decoupling effect of the silicon filled in the composite increased the response signal decay rates larger than 98%, which effectively decreased the acoustic coupling between adjacent elements. Therefore, the composite showed a potential use in multi-beam transmitter arrays.

Four-phase closure algorithm for coherent field imaging

According to the realization principle of phase closure in coherent field imaging, a new four-phase closure (FPC) algorithm is proposed for T-array multi-beam transmitter system. A type of four-item measurement radio of closure phase is first defined, and then the validity of FPC is confirmed in cancelling out the random atmospheric phase aberrations as well as eliminating atmospheric scintillation effect on degradation of the reconstructed image. Simulations prove the effectiveness of FPC, providing a new approach in removing atmospheric aberrations for multi-beam coherence field imaging.

Space and time diversity in indoor wireless optical links achieving higher data rate

Multispot diffusing configuration (MSDC) in optical wireless links provide uniform optical power needed for multiaccess and spatial dependence that can be used to allow space diversity techniques over the link. The spatial channels are furnished in MSDC through utilizing multibeam transmitter that produces spatially confined diffusing spots, and a multibranch receiver with small enough branch field-of-view (FOV) to restrict the number of diffusing spots within its FOV. Here, we study different encoding techniques that use space and time diversity to reduce the bit error rate. An improved technique, constellation rotation, is proposed for pulse amplitude modulated (PAM) to increase the Euclidian distance between signal points, and thus reduce bit error. Our study shows that when a cap is placed on the amount of power allocated per channel, the performance of the improved 4-PAM using three spatial channels and soft binary decision provide the optimal performance. When the power allocated per user is restricted, the best performance is obtained through soft binary decision and by using symbols identified by their level and spatial channel to carry 2 bits per signal level-channel.

Performance Analysis of Optical Wireless Communication System Employing Neuro-Fuzzy Based Spot-Diffusing Techniques

The spot-diffusing technique provides better performance compared to conventional diffuse system for indoor optical-wireless communication (OWC) system. In this paper, the performance of an OW spot-diffusing communication system using Neuro-Fuzzy (NF) adaptive multi-beam transmitter configuration has been proposed. The multi-beam transmitter generates multiple spots pointed in different directions, hence, forming a matrix of diffusing spots based on position of the receiver and receiver mobility. Regardless of the position of the transmitter and receiver, NF controller target the spots adaptively at the best locations and allocates optimal power to the spots and beam angle are adapted in order to achieve better signal-to-noise plus interference ratio (SNIR). Maximum ratio combining (MRC) is used in the imaging receiver. The proposed OW spot-diffusing communication system is compared with other spot-beam diffusion methods proposed in literature. Performance evaluation revels that the proposed NF based OW spot-diffusing communication system outperforms other spot-beam diffusion methods.

Preliminary study of the characteristic of multi-beam in intense multi-beam relativistic klystron

Compared with the conventional klystron, high power multi-beam klystron makes use of many low perveance beams, then it has a high output efficiency and low operating voltage, but it brings new problems. There fore, the multi-beam intense relativistic electron beam transmission in the multi-beam klystron is investigated by experiment and simulation. The results show that the multi-beam rotates around the center of the system due to the interaction of the multi-beam, and simultaneously the multi-beam rotates around its own center due to the space charge effect of each beam's own. All the process can result in electron beams loss.

Research on Modeling Multi-Beam Transmission Channel under the Atmospheric Turbulence

Abstract The atmospheric turbulence is an important factor which affects the laser atmosphere communication. Particularly, the probability distribution of the light intensity fluctuation is the focus of the research when the laser transfers in the strong turbulence or long distance transmission. And the multi-beam transmission is one of the most important ways to settle the impact on the atmospheric turbulence. This paper takes the negative exponential distribution, I-K distribution as the basis to establish the distribution model of the light intensity under the weak and strong turbulence. Moreover, it uses the test result of related document s for verification. The result shows that the simulation result agrees with the test result relatively; the distribution curve is corresponded; and the degree of fitting is relatively high. With the increase of the beams, the function value for the light intensity distribution is increased; and with the increase of the receiving aperture, the function value for the light intensity distribution is increased.

Design of an Omnidirectional Multibeam Transmitter for High-Speed Indoor Wireless Communications

For future high speed indoor wireless communication, diffuse wireless optical communications offer more robust optical links against shadowing than line-of-sight links. However, their performance may be degraded by multipath dispersion arising from surface reflections. We have developed a multipath diffusive propagation model capable of providing channel impulse responses data. It is aimed to design and simulate any multibeam transmitter under a variety of indoor environments. In this paper, a multi-beam transmitter system associated with hemisphere structure is proposed to fight against the diverse effects of multipath distortion albeit, at the cost of increased laser power and cost. Simulation results of multiple impulse responses showed that this type of multi-beam transmitter can significantly improve the performance of BER suitable for high bit rate application. We present the performance and simulation results for both line-of-sight and diffuse link configurations. We propose a design of power radiation pattern for a transmitter in achieving uniform and full coverage of power distributions for diffuse indoor optical wireless systems.

Optical Wireless Systems Employing Adaptive Collaborative Transmitters in an Indoor Channel

We propose a novel optical wireless (OW) system based on a power adaptive multibeam spot-diffusing transmitter serving multiple seven-segment maximum ratio combining (MRC) angle diversity receivers. A feedback link is assumed between the transceivers so that each receiver conveys to the multibeam transmitter the new beams transmit power weights to be used to achieve the best signal quality at a given receiver location. Two cases involving three and five receivers are considered. Four different configurations for the placement of the three-receiver case in the room are also examined. The system's performance in each case is evaluated in terms of signal-to-noise ratio (SNR) and is compared with the single receiver scenario with and without power adaptation. In the presence of one receiver, the transmit spot powers can be adjusted for optimum performance at that receiver location. For multiple receivers, there is conflict, and we propose spot power adaptation based on the average requirements (power distribution in spots), i.e., transmit equal gain combining (EGC) of spot power or MRC of transmit spot powers. The results show that the three receivers benefit most from an adaptive transmitter when each is placed at a corner of the room. In this case, an SNR increase of as much as 2.6 dB is achieved for all three receivers at the corners by both MRC and EGC. Moreover, when all receivers are placed away from the line of diffusing spots, our proposed MRC collaborative approach is 1 dB better than the noncollaborative system. This gain reduces the difference from the upper bound set by the single receiver adaptation, which is 3 dB. For a mobile transmitter, MRC also significantly improved the SNR for the farthest receivers at the opposite end from the transmitter located near one room corner.

A QoS-Based Dynamic Queue Length Scheduling Algorithm in Multiantenna Heterogeneous Systems

The use of real-time delay-sensitive applications in wireless systems has significantly grown during the last years. Therefore the designers of wireless systems have faced a challenging issue to guarantee the required Quality of Service (QoS). On the other hand, the recent advances and the extensive use of multiple antennas have already been included in several commercial standards, where the multibeam opportunistic transmission beamforming strategies have been proposed to improve the performance of the wireless systems. A cross-layer-based dynamically tuned queue length scheduler is presented in this paper, for the Downlink of multiuser and multiantenna WLAN systems with heterogeneous traffic requirements. To align with modern wireless systems transmission strategies, an opportunistic scheduling algorithm is employed, while a priority to the different traffic classes is applied. A tradeoff between the maximization of the throughput of the system and the guarantee of the maximum allowed delay is obtained. Therefore, the length of the queue is dynamically adjusted to select the appropriate conditions based on the operator requirements.

Experimental study of parametric transmission: Simultaneous generation of two beams

In order to respond to the buried mines threat, an approach of GESMA (Groupe d'Etudes Sous‐Marines de l'Atlantique) is to take advantage of the parametric transmission in sonar imagery. This technique allows producing narrow beamwidths at low frequencies. Such a parametric transmitter has been designed and calibrated in collaboration with an academic laboratory of Paris VI, and the targeted benchmark is fulfilled: 2° @ 20 kHz, with sufficient source level. The design of the complete sonar system is based on a sequential multibeam transmission associated with a synthetic aperture technique at receive. However, the shortfall of the sweeping technique lies in the timing limitation. One solution to increase the coverage rate is the simultaneous generation of several parametric beams in different directions. Experimentations have been conducted in a tank with different signals: CW, LFM, Ricker. This presentation addresses the results of these experimentations in the context of buried mines detection and classification.

Mobile adaptive multi-beam spot-diffusing indoor optical wireless system

Multi-beam spot-diffusing optical wireless systems have been shown to offer performance improvement over conventional diffuse systems. In this work, the authors introduce a new adaptive technique to adjust the transmit power for each beam produced by a multi-beam optical transmitter aimed at the room ceiling so as to optimise the received signal-to-noise ratio (SNR) at a given receiver location. The transmitter receives computed tap weights for transmit powers from the receiver through a feedback link between the transceivers. In addition to a single spot power adaptation, adaptation of the power of clusters of five, ten and twenty spots (which reduces the complexity of the adaptation process) was used and the performance was evaluated. The effect of transmitter mobility was investigated with the system employing an angle diversity receiver. Performance comparison with the results of a non-adaptive transmitter system is presented in terms of SNR and delay spread. The adaptive method achieved a considerable gain in SNR, especially at the weakest links for both the mobile and non-mobile transmitters. Over 6 dB increase in SNR is achieved when the distance between the transceivers is largest for the non-mobile transmitter and over 3 dB for the same situation in the case of a mobile transmitter. The influence of the field of view of a multidetector receiver was examined with the adaptive transmitter. The adaptive technique can be used with a two-dimensional multi-beam clustering having clusters of spots on the walls as well as on the ceiling. This is currently under investigation.

Autonomous underwater vehicles (AUVs) and investigations of the ice–ocean interface in Antarctic and Arctic waters

AbstractLimitations of access have long restricted exploration and investigation of the cavities beneath ice shelves to a small number of drillholes. Studies of sea-ice underwater morphology are limited largely to scientific utilization of submarines. Remotely operated vehicles, tethered to a mother ship by umbilical cable, have been deployed to investigate tidewater-glacier and ice-shelf margins, but their range is often restricted. The development of free-flying autonomous underwater vehicles (AUVs) with ranges of tens to hundreds of kilometres enables extensive missions to take place beneath sea ice and floating ice shelves. Autosub2 is a 3600 kg, 6.7 m long AUV, with a 1600 m operating depth and range of 400 km, based on the earlier Autosub1 which had a 500 m depth limit. A single direct-drive d.c. motor and five-bladed propeller produce speeds of 1–2 m s−1. Rear-mounted rudder and stern-plane control yaw, pitch and depth. The vehicle has three sections. The front and rear sections are free-flooding, built around aluminium extrusion space-frames covered with glass-fibre reinforced plastic panels. The central section has a set of carbon-fibre reinforced plastic pressure vessels. Four tubes contain batteries powering the vehicle. The other three house vehicle-control systems and sensors. The rear section houses subsystems for navigation, control actuation and propulsion and scientific sensors (e.g. digital camera, upward-looking 300 kHz acoustic Doppler current profiler, 200 kHz multibeam receiver). The front section contains forward-looking collision sensor, emergency abort, the homing systems, Argos satellite data and location transmitters and flashing lights for relocation as well as science sensors (e.g. twin conductivity–temperature–depth instruments, multibeam transmitter, sub-bottom profiler, AquaLab water sampler). Payload restrictions mean that a subset of scientific instruments is actually in place on any given dive. The scientific instruments carried on Autosub are described and examples of observational data collected from each sensor in Arctic or Antarctic waters are given (e.g. of roughness at the underside of floating ice shelves and sea ice).

Ultrasonic transmitting and receiving apparatus

An ultrasonic transmitting and receiving apparatus for performing the multibeam transmission capable of suppressing the increase in withstand voltage of the ultrasonic transducers and power consumption with increase of the number of transmission beams. This apparatus includes an ultrasonic probe, a drive waveform synthesizing unit for generating information on a synthesized drive waveform obtained by synthesizing the drive waveforms with respect to the respective ultrasonic transducers in order to allow the ultrasonic probe to transmit the ultrasonic beams simultaneously in the different directions, transmitting circuits for generating the drive signals according to the information generated by the drive waveform synthesizing unit and in which plural kinds of maximum output voltages are determined so as to correspond to the maximum amplitudes of the drive signals supplied to the respective ultrasonic transducers, and receiving circuits for processing the detection signals outputted from the ultrasonic transducers received the ultrasonic echoes, respectively.