Single Transmitter Research Articles

Development of a multi frequency impedance measurement system for use in MEMS flow cytometers

A novel MEMS based system for flow cytometry is presented based on a multispectral approach. The solution provides the ability to concurrently generate, detect and analyse the response from a biological cell using multiple narrow band signals with a frequency separation sufficient to evoke different cellular responses. The narrow band approach limits the energy required and provides an improved signal to noise ratio for a given transmitter energy, avoiding wide band signal power dissipation and dilution issues. It requires only a single transmitter and receiver interface to the MEMS device with no duplication of analogue signal paths. The design has the ability to generate a complex multi frequency waveform with a wide frequency separation. A digital approach based on the CORDIC algorithm (Volder, IRE Trans Electron Comput EC-8:330–334, 1959) was used to generate the required sinusoidal waveforms. The digital section of the design was implemented on an FPGA. It utilised a modified digital phase sensitive amplifier to provide enhanced signal to noise performance and harmonic rejection. A novel hybrid, cross channel electrode structure to implement the stimulus and response analysis sub-system has been designed. A fully functional macroscopic test bench has been constructed to demonstrate the viability of the approach. Both physical measurements and finite element data has been used to demonstrate the potential for migration into a MEMS based system.

Radar Sensor Signal Acquisition and Multidimensional FFT Processing for Surveillance Applications in Transport Systems

The design and test of a radio detection and ranging (Radar) sensor signal acquisition and processing platform is presented in this paper. The Radar sensor operates in real time and is suited for surveillance applications in transport systems. It includes a front-end with a continuous-wave frequency-modulated transceiver operating in X-band, with a single transmitter and multiple receivers, and a multichannel high-speed A/D converter. Sensor signal processing and data communication tasks with external hosts are managed by a field-programmable gate array. The signal processing chain includes region of interest selection, multidimensional fast Fourier transform, peak detection, alarm decision logic, data calibration, and diagnostic. By configuring the Radar sensing platform in low-power mode (7-dBm transmitted power), it is possible to detect still and moving targets with a covered range up to 300-m and 30-cm resolution. The measuring range can be increased up to 2 km by adding an extra 34.5-dBm power amplifier. The Radar sensing platform can be configured for a maximum detected speed of 200 km/h, with a resolution of 1.56 km/h, or a speed up to 50 km/h with a resolution of 0.4 km/h. The cross-range resolution depends on the number of receiving channels; a tradeoff can be found between cross-range resolution of the Radar sensor and its complexity and power consumption. With respect to the state of the art of surveillance Radar sensors and light detection and ranging, the proposed solution stands for its high configurability and for the better tradeoff that can be found in terms of covered distance and power consumption.

Pursuit of Neurotransmitter Functions: Being Attracted with Fascination of the Synapse.

In the beginning of the 1970s, only two chemical substances, acetylcholine and γ-aminobutyric acid (GABA), had been definitely established as neurotransmitters. Under such circumstances, I started my scientific career in Professor Masanori Otsuka's lab searching for the transmitter of primary sensory neurons. Until 1976, lines of evidence had accumulated indicating that the undecapeptide substance P could be released as a transmitter from primary afferent fibers into spinal synapses, although the substance P-mediated synaptic response had yet to be identified. Peripheral synapses could serve as a good model and thus, it was demonstrated in the prevertebral sympathetic ganglia by1985 that substance P released from axon collaterals of primary sensory neurons acts as the transmitter mediating non-cholinergic slow excitatory postsynaptic potential (EPSP). At that time, we also found that autonomic synapses were useful to uncover the transmitter role of the opioid peptide enkephalins, whose functions had been unknown since their discovery in 1975. Accordingly, enkephalins were found to serve a transmitter role in mediating presynaptic inhibition of cholinergic fast and non-cholinergic slow transmission in the prevertebral sympathetic ganglia. In 1990s, we attempted to devise a combined technique of brain slices and patch-clamp recordings. We applied it to study the regulatory mechanisms that operate around cerebellar GABAergic inhibitory synapses, because most of the studies then had centered on excitatory synapses and because inhibitory synapses are crucially involved in brain functions and disorders. Consequently, we discovered novel forms of heterosynaptic interactions, dual actions of a single transmitter, and receptor crosstalk, the details of which are described in this review.

Reducing spectrum use in traditional and SFN-based television for uniform and non-uniform deployments

During the last few years, reclaiming TV spectrum for mobile broadband use has been a hotly debated topic in the telecommunications policy agenda. This paper evaluates two ways to improve spectrum efficiency to today's noise-limited single-transmitter broadcast television approach. One way is to increase the transmit power of each broadcaster's only transmitter. The other way is to replace that single transmitter with a multi-transmitter low-power low-tower (LPLT) single frequency network (SFN). In order to quantify their potential benefits, two different scenarios are considered. First, this paper presents the results obtained for a large region in which broadcasters are uniformly distributed, so that the number of TV broadcasts that can be received is roughly the same at any location. In this case, results suggest that increasing power of traditional single-transmitter broadcasters could reduce the amount of spectrum needed for TV by up to 30%, and would be cost-effective for population densities above 30 per square km. A switch to SFNs could reduce the amount of spectrum needed for TV by roughly 60%, but at a higher cost. Results suggest that the LPLT SFN approach could be cost-effective for regions with uniformly distributed broadcasters and population densities above 120 per square km. The study then quantifies spectrum efficiency gains in regions where broadcasters are not uniformly distributed. In particular, it considers the case where U.S. broadcasters in the UHF band continue to serve their coverage areas as of 2015. In this case, the amount of spectrum that can be freed from TV throughout the entire nation using these two approach is considerably smaller, but some additional bands can be freed from TV throughout much of the nation. Moreover, most of these spectrum gains can be obtained when only a minority of broadcasters change their technical approach.

Releasing rate optimization in a single and multiple transmitter local drug delivery system with limited resources

Drug delivery is one of the most important applications of molecular communication. Drug transmitters have limited resources in terms of energy and reservoir and these limitations should be taken into consideration when designing a drug delivery system. Drug molecules may also be expensive and releasing a large amount of them can have harmful effects on the healthy parts of the body. In this paper, we consider a multiple transmitter local drug delivery system in which the nearest transmitters to a randomly located tumor are activated to release drug molecules and guarantee the Least Effective Concentration (LEC) in every part of the tumor. We propose two different scenarios: a single transmitter drug delivery system for which the optimal rate of the transmitting nanomachine and the optimal density of deployed nanomachines are derived through formulations and simulations. Poisson distributed as well as regular square and hexagon grid deployments are investigated. We then extend it to a multiple transmitter drug delivery system for which the optimal allocated rate to each releasing transmitter is derived in order to minimize the total rate of release and maintain LEC in every part of the tumor. It is shown that activating multiple transmitters leads to a reduction in the total optimal release rate of drug molecules as well as improving the time duration between consecutive administrations.

Backward wave separation method in a single transmitter and multi-receiver sensor array for improved damage identification of two-dimensional structures

In this paper, a backward wave separation method is proposed. Since the first backward wave can be considered as the damage reflection, the damage reflected wave peaks are artificially amplified by appropriately shifting and summing signals collected from a series of sensing points aligned along the wave propagating direction. This shifting and summing process aims to present the damage reflected wave peaks more distinctively while offsets randomly distributed environmental interferences. Due to the high signal-to-noise ratio of the treated signal, the application of backward wave separation is able to attain baseline-free damage detection. A circular single transmitter and multi-receiver sensor array is then deployed on a metal plate to identify the crack-like damage. Signals collected by the sensor array with and without the treatment of the backward wave separation method are, respectively, imported to the delay-and-sum imaging algorithm to yield individual damage contours. The comparisons between these contours demonstrate that the backward wave separation method is able to significantly improve the damage identification performance of the sensor array with respect to the damage localization accuracy, noise immunity, and damage sensitivity. Both the finite element modeling and laser measurement are conducted to validate the effectiveness of the proposed backward wave separation method.

An Efficient Global Algorithm for Single-Group Multicast Beamforming

Consider the single-group multicast beamforming problem, where multiple users receive the same data stream simultaneously from a single transmitter. The problem is NP-hard and all existing algorithms for the problem either find suboptimal approximate or local stationary solutions. In this paper, we propose an efficient branch-and-bound algorithm for the problem that is guaranteed to find its global solution. To the best of our knowledge, our proposed algorithm is the first tailored global algorithm for the single-group multicast beamforming problem. Simulation results show that our proposed algorithm is computationally efficient (albeit its theoretical worst-case iteration complexity is exponential with respect to the number of receivers) and it significantly outperforms a state-of-the-art general-purpose global optimization solver called Baron. Our proposed algorithm provides an important benchmark for performance evaluation of existing algorithms for the same problem. By using it as the benchmark, we show that two state-of-the-art algorithms, semidefinite relaxation algorithm and successive linear approximation algorithm, work well when the problem dimension (i.e., the number of antennas at the transmitter and the number of receivers) is small but their performance deteriorates quickly as the problem dimension increases.

Wireless Power Transfer With Three-Ports Networks: Optimal Analytical Solutions

A wireless transfer link between three magnetically coupled resonators has been considered. Two different configurations have been investigated. In one case a single transmitter and two receivers are present. In the other case two transmitters and a single receiver are employed. For each case optimal analytical solutions for the load values that maximize the power delivered to the load(s) and the efficiency have been found and validated by comparisons with circuit simulations.

MIMO wireless power transfer based on magnetic beamforming

Wireless power transfer (WPT) promises to provide sufficient power for multiple users. However, majority of prior works focused on systems with single transmitter or receiver. In this paper, we base our MIMO wireless power transfer MIMO-WPT) system with N transmitters and two receivers on magnetic beamforming which is similar to that in a MIMO system of wireless communication. From the perspective of signal processing and practical application, we formulate an optimisation problem to minimise total power consumed by all transmitters, subject to the minimum power required by both receivers. Furthermore, we demonstrate that the semi-definite relaxation (SDR) of such a quadratically constrained quadratic programming (QCQP) problem is tight, thus can be solved by standard interior-point algorithm. Simulation results show that compared with the uncoordinated baseline scheme of identical current allocation, our MIMO-WPT system has boost power efficiency prominently. In the end, we consider a more general model with N transmitters and M receivers, and the characteristic of the optimal solution is deduced.

Dual-Band Digital Predistortion Using a Single Transmitter Observation Receiver and Single Training Engine

This paper tackles the hardware complexity of a digital predistortion (DPD) system used to linearize a power amplifier (PA) driven with interband carrier aggregated (CA) signals (i.e., two component carriers with different modulation bandwidths and wide frequency separations). It focuses particularly on reducing the required bandwidth, and number of channels, of the transmitter's observation receiver (TOR) as well as the specifications of the underlying building blocks (e.g., speed of the analog-to-digital converter). A novel dualband DPD system using a single TOR was devised. The training of the DPD for each band was carried out in an alternating fashion, using a single training engine following a model-reference adaptive control approach with a recursive least squares algorithm. The proposed approach was experimentally validated by successfully linearizing a 20-W Class F Doherty PA driven with different multistandard CA signals.

The Dirty MIMO Multiple-Access Channel

In the scalar dirty multiple-access channel, in addition to Gaussian noise, two additive interference signals are present, each known non-causally to a single transmitter. It was shown by Philosof et al. that for strong interferences, an independent identically distributed ensemble of codes does not achieve the capacity region. Rather, a structured-codes approach was presented that was shown to be optimal in the limit of high signal-to-noise ratios, where the sum capacity is dictated by the minimal (“bottleneck”) channel gain. In this paper, we consider the multiple-input multiple-output (MIMO) variant of this setting. In order to incorporate structured codes in this case, one can utilize matrix decompositions that transform the channel into effective parallel scalar dirty multiple-access channels. This approach, however, suffers from a “bottleneck” effect for each effective scalar channel and, therefore, the achievable rates strongly depend on the chosen decomposition. It is shown that a recently proposed decomposition, where the diagonals of the effective channel matrices are equal up to a scaling factor, is optimal at high signal-to-noise ratios, under an equal rank assumption. This approach is then extended to any number of transmitters. Finally, an application to physical-layer network coding for the MIMO two-way relay channel is presented.

Optimal Sensor Communications in Presence of Transmission Delays and Bandwidth Limitations

In a distributed sensor (and actuator) network, several sensors may be lumped to a single transmitter or communicate via a remote terminal unit. Due to bandwidth limitations in the network, the transmitter/remote terminal should decide on the communication sequence according to which it sends sensor data. This decision must be based on an appropriate performance criterion. In this paper, we formulize this problem and propose a convex optimization scheme to optimize the estimation variance via choosing the most appropriate communication sequence. The derived communication sequence is then used for designing a Kalman filter to estimate states of the underlying system. Both cases of Zero-Order Hold and Reset To Zero output policies are investigated and compared in the simulation.

Voltage transfer ratio analysis for multi‐receiver resonant power transfer systems

The wireless power transfer characteristics of system architectures with single transmitter and multiple receiver coils are investigated. With multiple receivers in a limited space, couplings within receivers occur. Effective resonant frequency is changed due to such couplings, the desired working region should be adjusted accordingly. An equivalent circuit model is developed to describe the system with a single receiver, and extended to describe the system with two receivers. The circuit model yields transfer frequency responses that are in good agreement with experimental measurements over a range of frequencies that span the resonance. In a multi-receiver system, a method for tracking frequency shifts or retuning the lumped capacitance so as to maximise the efficiency is proposed. The simulation and experimental results well agree with the theoretical analysis.

Precoding Design for Single-RF Massive MIMO Systems: A Large System Analysis

This letter revisits a recently proposed precoding design for massive multiple-input multiple-output (MIMO) systems that is based on the use of an instantaneous total power constraint. The main advantages of this technique lie in its suitability to the recently proposed single radio frequency MIMO transmitter coupled with a very-high power efficiency. Such features have been proven using simulations for uncorrelated channels. Based on tools from random matrix theory, we propose in this letter to analyze the performance of this precoder for more involved channels accounting for spatial correlation. The obtained expressions are then optimized in order to maximize the signal-to-interference-plus-noise ratio (SINR). Simulation results are provided in order to illustrate the performance of the optimized precoder in terms of peak-to-average power ratio and SINR.

Energy Efficient Antenna Arrays for Indoor 3-D Microwave Imaging

A 2-D antenna array, coupled with the range-migration algorithm (RMA), enables 3-D microwave imaging of people and objects in a room. The choice of antenna array configuration, microwave transceiver components, and transmit power has a significant effect on both the energy consumed by the imaging system and the quality of the resulting images. A generic microwave imaging testbed was therefore built to characterize the effect of these antenna array parameters on image quality in the 20-GHz band. The standard, the single-transmitter, and the Doppler RMAs were all compared and were found to produce good quality 3-D images with transmit power levels as low as −30 dBm, achieving an image resolution of 12.5 mm at 0.5-m range. A new figure of merit was also developed to compare how efficiently these algorithms can create an image of given quality and size. The single transmitter imaging system was the most efficient, able to generate an image signal-to-noise ratio of 1330 for each microjoule consumed per voxel in the image. These findings have led to a methodology for designing energy and cost efficient microwave imaging systems.

Energy-Based Modulation for Noncoherent Massive SIMO Systems

An uplink system with a single antenna transmitter and a single receiver with a large number of antennas is considered. We propose a single-shot noncoherent scheme which does not use the instantaneous channel state information (CSI), but rather only the knowledge of the channel statistics, a transmitter that modulates information only in the amplitude of the symbols, and a receiver which measures only the average received energy across the antennas. This system model is motivated by the simplicity of the circuit design and the energy efficiency it entails for both the transmitter and the receiver. We propose constellation designs which are asymptotically optimal with respect to symbol error rate (SER) with an increasing number of antennas, for any finite signal-to-noise power ratio (SNR), under different assumptions on the availability of CSI statistics. We describe in detail the case when there is a bounded uncertainty on the moments of the fading distribution. We present the numerical results on the SER performance achieved by these designs and find that they outperform the existing amplitude-modulation-based noncoherent scheme of amplitude shift keying (ASK). They also achieve a smaller peak-to-average power ratio (PAPR) for scenarios with a low SNR or a large line-of-sight (LOS) component.

Three-dimensional indoor visible light positioning system with a single transmitter and a single tilted receiver

Recently, visible light positioning has gradually become a research hotspot in indoor environments. Based on a single transmitter and a single tilted optical receiver, a three-dimensional (3-D) indoor visible light positioning system is proposed. The tilted optical receiver is installed on a rotatable and retractable platform. The 3-D space is divided many two-dimensional (2-D) planes by lifting the platform of the optical receiver. In each 2-D plane, various azimuth angles can be obtained by rotating the receiver platform, which offers a feasible way to perform multiple measurements with different azimuth angles to achieve the angle gain. According to the difference of the angle gain, a 3-D positioning algorithm is proposed. Experimental results show that the proposed positioning algorithm can provide good positioning accuracy.

Adaptive Random Network Coding for Multicasting Hard-Deadline-Constrained Prioritized Data

Random network coding (RNC) is a promising solution for multicast services over wireless networks. In this paper, we consider the problem of deadline-constrained multimedia multicast from a single transmitter to multiple users over wireless erasure channels. A novel transmission scheduling strategy based on adaptive RNC is developed to maximize the throughput of multicast sessions under a deterministic delay constraint. Particularly, we optimize the number of multimedia data layers under different assumptions on users' feedback. Simulation results show the effectiveness of the proposed methods.

Multipath Assisted Positioning with Simultaneous Localization and Mapping

This paper describes an algorithm that exploits multipath propagation for position estimation of mobile receivers. We apply a novel algorithm based on recursive Bayesian filtering, named Channel-SLAM. This approach treats multipath components as signals emitted from virtual transmitters, which are time synchronized to the physical transmitter and static in their positions. Contrary to other approaches, Channel-SLAM considers also paths occurring due to multiple numbers of reflections or scattering as well as the combination. Hence, each received multipath component increases the number of transmitters resulting in a more accurate position estimate or enabling positioning when the number of physical transmitters is insufficient. Channel-SLAM estimates the receiver position and the positions of the virtual transmitters simultaneously; hence, the approach does not require any prior information, such as a room-layout or a database for fingerprinting. The only prior knowledge needed is the physical transmitter position as well as the initial receiver position and moving direction. Based on simulations, the position precision of Channel-SLAM is evaluated by a comparison to simplified algorithms and to the posterior Cramer-Rao lower bound. Furthermore, this paper shows the performance of Channel-SLAM based on measurements in an indoor scenario with only a single physical transmitter.

Optimal Geometry Analysis for Multistatic TOA Localization

Multistatic time-of-arrival (TOA) localization has recently attracted great attention due to performance advantages offered by multistatic radar. In target localization, the relative sensor-target geometry is an important factor that can significantly affect the localization performance. In this paper, we analyze the optimal geometries for a two-dimensional TOA localization configuration commonly presented in the literature with a single transmitter and multiple receivers. Our analysis is based on minimizing the area of estimation confidence region, which is equivalent to maximizing the determinant of the Fisher information matrix. If the coordinate system is rotated such that the bearing angle of the transmitter with respect to the target is zero, an optimal geometry is obtained when a subset of the receivers are collinear with the target at a bearing angle of $\pi /3$ rad and the remaining receivers at a bearing angle of $-\pi /3$ rad. The arrangement of the receivers on either branch of the bearing angles, i.e., $\pi /3$ rad or $-\pi /3$ rad, is decided based on the measurement noise variances at the receivers. We conclude the study with numerical solutions generated by the genetic algorithm and simulation examples for UAV path optimization to verify the accuracy of the analytical findings.