Receiver Pair Research Articles

Near-surface S-wave velocities estimated from traffic-induced Love waves using seismic interferometry with double beamforming

I use ambient noise, especially traffic noise, to estimate the 2D near-surface S-velocity distribution. Near-surface velocities are useful for understanding structure, stiffness, porosity, and pore pressure for engineering/environmental purposes and static correction of active-source imaging. I extract Love waves propagating between each receiver pair from 12 h of traffic noise using seismic interferometry with power-normalized crosscorrelation. The receiver array contained three parallel lines, each of which had 100 transverse-component geophones. I apply double beamforming to the correlations at the parallel lines for improving the signal-to-noise ratio of the extracted Love waves to satisfy the stationary phase assumption for seismic interferometry. I use these Love waves for a dispersion analysis to estimate a 2D near-surface S-wave velocity model based on the multichannel analysis of surface waves. To improve the lateral resolution of the velocity model, I sort the extracted waves according to common midpoints (CMPs) and limited the maximum offset of receiver pairs. The dispersion analysis at each CMP is based on the assumption of layered media, and using all CMPs, I can estimate high-resolution 2D velocities down to 80 m depth. The velocity variations are similar to the location of strong reflectors obtained by a previous study. The main features of the velocity model are recovered even from 1 h of continuous traffic-noise data, which means that the proposed technique can be used for efficient 4D surveys.

Performance Enhancement of Land Vehicle Positioning Using Multiple GPS Receivers in an Urban Area.

The Global Positioning System (GPS) is the most widely used navigation system in land vehicle applications. In urban areas, the GPS suffers from insufficient signal strength, multipath propagation and non-line-of-sight (NLOS) errors, so it thus becomes difficult to obtain accurate and reliable position information. In this paper, an integration algorithm for multiple receivers is proposed to enhance the positioning performance of GPS for land vehicles in urban areas. The pseudoranges of multiple receivers are integrated based on a tightly coupled approach, and erroneous measurements are detected by testing the closeness of the pseudoranges. In order to fairly compare the pseudoranges, GPS errors and terms arising due to the differences between the positions of the receivers need to be compensated. The double-difference technique is used to eliminate GPS errors in the pseudoranges, and the geometrical distance is corrected by projecting the baseline vector between pairs of receivers. In order to test and analyze the proposed algorithm, an experiment involving live data was performed. The positioning performance of the algorithm was compared with that of the receiver autonomous integrity monitoring (RAIM)-based integration algorithm for multiple receivers. The test results showed that the proposed algorithm yields more accurate position information in urban areas.

Acoustic characterization of the new Arctic during Ice Exercise 2016

The Naval Postgraduate School (NPS) participated in Ice Exercise 2016 (ICEX-16), a multi-national naval exercise conducted in the Beaufort Sea during March 2016. Operating at a remote ice camp, NPS deployed several conductivity, temperature and depth (CTD) sensors to capture oceanographic variability to 500 m depth while performing a series of propagation tests. Mobile and dipped mid-frequency sources transmitted signals to a pair of vertical line array receivers positioned in the field to investigate depth, range, angular and specular characteristics of acoustic propagation and their correlation to variability in oceanographic structure and under-ice conditions. CTD data indicate there was significant variability in sound speed at 50m depth where cold, fresh mixed-layer water interfaces with contrasting warm, saline Pacific Summer Water (PSW) that lays immediately below it. The data also show a persistent and stable subsurface sound channel existed as a result of the PSW with peak temperature at 80 m situated above colder Pacific Winter Water (PWW), resulting in a sound channel axis near 140 m depth. Both features have important implications on sonar performance in the Arctic. Modeled and measured transmission loss are compared to quantify the effects.

Optical probe utilizing the cross-beam method for measuring solids

The cross-beam method has been used in calculations of load distribution, flow velocity, ultrasonic speed, and so on. This paper shows that the method is also mostly feasible to be utilized in optics-based measurement of suspended solids in liquid. We present a prototype of a measurement probe that has a set of two near-infrared emitter–receiver pairs and employs the cross-beam method. Our laboratory experiments, focused on measurements of H2O−SiO2 solid solution, show that the developed probe has good sensitivity and can linearly measure the concentration of suspended solids with a wide dynamic range. The presented prototype is suitable for a broad range of applications. In particular, we demonstrate its suitability for monitoring sedimentation in water.

On the secrecy of the cognitive interference channel with partial channel states

AbstractThe secrecy problem in the state‐dependent cognitive interference channel is considered in this paper. In our model, there are a primary and a secondary (cognitive) transmitter–receiver pairs, in which the cognitive transmitter has the message of the primary one as side information. In addition, the channel is affected by two channel state sequences, which are known at the cognitive transmitter and the corresponding receiver, separately. The cognitive transmitter should cooperate with the primary one, and it wishes to keep its message secure at the primary receiver. The achievable equivocation‐rate regions for this channel are derived using two approaches: the binning scheme coding and superposition coding. Then, comparisons between the results using two coding approaches, in Gaussian case, shows that there is a trade‐off between the achievable rate of the primary transmitter and the equivocation rate of the cognitive one. Moreover, the outer bounds on the capacity of the channel are derived. Copyright © 2016 John Wiley & Sons, Ltd.

Coordinated Shared Spectrum Precoding With Distributed CSIT

In this paper, the operation of a licensed shared access system is investigated, considering downlink communication. The system comprises a multiple-input-single-output (MISO) incumbent transmitter (TX)–receiver (RX) pair, which offers a spectrum sharing opportunity to a MISO licensee TX-RX pair. Our main contribution is the design of a coordinated transmission scheme, inspired by the underlay cognitive radio (CR) approach, with the aim of maximizing the average rate of the licensee, subject to an average rate constraint for the incumbent. In contrast to most prior works on the underlay CR, the coordination of the two TXs takes place under a realistic channel state information (CSI) scenario, where each TX has solely access to the instantaneous direct channel of its served terminal. Such a CSI knowledge setting brings about a formulation based on the theory of Team Decisions, whereby the TXs aim at optimizing a common objective given the same constraint set, on the basis of individual channel information. Consequently, a novel set of applicable precoding schemes consisting in letting the two TXs cooperate on the basis of the statistical information is proposed. We verify by simulations that this novel, practically relevant, coordinated precoding scheme outperforms the standard underlay CR approach.

Strategic Power Allocation With Incomplete Information in the Presence of a Jammer

In this paper, distributed competitive interactions between a secondary user (SU) transmitter–receiver pair and a jammer are investigated using a game-theoretic framework under physical interference restrictions, power budget constraints, and incomplete knowledge of channel gains. In this game, the SU transmitter is expected to choose its power strategy with the objective of satisfying a minimum signal-to-interference plus noise ratio (SINR) at the corresponding receiver. Similarly, the jammer’s objective is to strategically allocate its power so that the SINR constraint of the SU is not satisfied. Due to a lack of complete information, this strategic power allocation problem between the two players is modeled as a Bayesian game for which the self-enforcing strategies of the SU transmitter–receiver pair and the jammer are analyzed. Furthermore, probability distributions are employed by the corresponding players to model the incomplete nature of the game. The solution of the game corresponds to Nash equilibria points. Equilibrium analysis is carried out by considering the mixed strategy solution space and numerical examples are presented for illustration.

Maximum Secondary Stable Throughput of a Cooperative Secondary Transmitter–Receiver Pair: Protocol Design and Stability Analysis

In this paper, we investigate the impact of cooperation between a secondary transmitter–receiver pair and a primary transmitter on the maximum stable throughput of the primary–secondary network. Each transmitter, either primary or secondary, has a buffer for storing its own traffic. In addition to its own buffer, the secondary transmitter has a buffer for storing a fraction of the undelivered primary packets due to channel impairments. Moreover, the secondary destination has a relaying queue (buffer) for storing a fraction of the undelivered primary packets. In our proposed cooperative system, the secondary transmitter and the secondary destination increase the spectrum availability for the secondary packets by relaying the unsuccessfully transmitted packets of the primary transmitter. We consider two multiple-access strategies to be used by the secondary transmitter and the secondary destination to utilize the silence sessions of the primary transmitter. Numerical results demonstrate the gains of our proposed cooperative system over the noncooperation case and the systems when the secondary transmitter is the only cooperating node in the network.

Digital linear chirp receiver for high chirp rates with high resolution time-of-arrival and time-of-departure estimation

The use of chirp signals in modern radar and ranging systems have numerous benefits. They are extensively used to improve signal-to-noise ratio and range resolution. The performance capabilities of these signals are directly related to their time-bandwidth product, i.e., the duration and bandwidth of the pulse. Ultra-wideband chirp signals are further desirable because they span a large bandwidth, making them resistant to narrowband environmental interference. The accurate detection and measurement of high chirp signals is difficult due to the necessity of a high-sampling analog-digital converter, a target measurement platform with high computational power, and a time-of-arrival (TOA) estimator with high temporal resolution. The difficulty of the problem is further compounded with the requirement that no a priori knowledge of the signal, noise, or operating environment is known. This paper presents a practical approach and implementation of a high linear chirp rate receiver and TOA estimator pair capable of detecting and measuring stationary radio frequency pulses as well as linear chirp rates up to 1.18 GHz in 400 ns. The high-resolution TOA algorithm and linear chirp receiver have been prototyped, synthesized, and placed and routed for a Virtex 6 SX475 FPGA.

Optimal power allocation over parallel Gaussian channels in cognitive radio and jammer games

Cognitive jammers are able to deploy advanced strategies that degrade the performance of cognitive radio (CR) user communications. In this study, the authors study the problem of power allocation in CR user and jammer games, over parallel Gaussian channels. They model the interaction between a communicator (a transmitter–receiver pair) and a jammer using zero-sum games with continuous action sets; they describe unilateral, Nash and Stackelberg games. They compare the Nash equilibrium (NE), the Stackelberg equilibrium and the minmax/maxmin optimal power allocations through the simulation of the diverse game scenarios. Finally, they give the theoretical proof of existence and uniqueness of the NE.

Outage Performance of Cognitive Relay Networks With Wireless Information and Power Transfer

In this paper, we consider underlay cognitive radio (CR) networks with one primary receiver, one cognitive transmitter–receiver pair, and one energy harvesting relay. The transmission power of the secondary source is opportunistically determined by its interference to the primary receiver, and the relay transmission is powered by the energy harvested from the radio-frequency observations at the relay. For the considered CR networks with simultaneous wireless information and power transfer (SWIPT), we derive analytical expressions for the outage probability, as well as their high signal-to-noise ratio (SNR) approximations in closed form. The developed analytical results demonstrate that the use of SWIPT will not cause any loss in diversity gain, but the outage probability achieved by the SWIPT-CR scheme asymptotically decays as ${\log \mbox{SNR}}/\mbox{SNR}$ , whereas a decaying rate of ${\mbox{1}}/\mbox{SNR}$ is achieved by a conventional CR network. Computer simulation results are also provided to demonstrate the accuracy of the presented analysis.

Wireless Power Transfer System for Biomedical Devices by using Magnetic Resonance Coupling Technique

Aim of this work is to study the energy transfer wirelessly using a pair of transmitter and receiver coil. The system aims to generate magnetic coupling resonance between two coils. Wireless power transfer system can eliminate wire connection during energy transmission. Many researchers show great interest on wireless power transfer technique for biomedical devices. This technique is important to be applied and integrated into biomedical devices such as pacemakers, defibrillators, Left Ventricular Assist Devices (LVAD) to ease the transfer system. Basically, there are two ways to power up the biomedical devices such as external power cord and batteries. However, batteries had its limited capacity and external power cord limit patient’s freedom and might lead to infection. Therefore in this study, two coil wireless transfer system was designed in order to solve the problem. Two 30 cm diameter coils transmitter and receiver pairs had been designed to provide 72.7% of efficiency up to 37 cm of transmission distance. It can be concluded that this system is suitable for long range power transmission with good efficiency.

The emergence of spurious arrivals in Green’s function extraction and passive imaging

Cross-correlations of ambient noise at two receivers can extract the two-point Green’s function, given that the wave-field is spatially uniform. The presence of scatterers that act as uncorrelated secondary sources can destroy this condition. We retrieve the Green’s function in one-sided noise with a scatterer in an aeroacoustic experiment, using a pair of microphones (separation 1 m) parallel to the beach which generate one-sided surf noise. The scatterer is a 20-cm-radius polyvinyl chloride pipe 2.5 m to the landside of the microphone pair. We cross correlate 400–2000 Hz noise to retrieve the Green’s function. The results show that spurious scattered arrival emerges in the cross-correlation functions when the source distribution is limited. This causes the generalized optical theorem to break down, and thus, there is no guarantee that the spurious scattered arrival cancels. However, the spurious waves have a geometric interpretation, which are useful for inversion. By combining the travel times of the spurious and physical scattered waves, only a pair of receivers is sufficient to locate the scatterer passively.

Jamming Bandits—A Novel Learning Method for Optimal Jamming

Can an intelligent jammer learn and adapt to unknown environments in an electronic warfare-type scenario? In this paper, we answer this question in the positive, by developing a cognitive jammer that adaptively and optimally disrupts the communication between a victim transmitter–receiver pair. We formalize the problem using a multiarmed bandit framework where the jammer can choose various physical layer parameters such as the signaling scheme, power level and the on-off/pulsing duration in an attempt to obtain power efficient jamming strategies. We first present online learning algorithms to maximize the jamming efficacy against static transmitter–receiver pairs and prove that these algorithms converge to the optimal (in terms of the error rate inflicted at the victim and the energy used) jamming strategy. Even more importantly, we prove that the rate of convergence to the optimal jamming strategy is sublinear, i.e., the learning is fast in comparison to existing reinforcement learning algorithms, which is particularly important in dynamically changing wireless environments. Also, we characterize the performance of the proposed bandit-based learning algorithm against multiple static and adaptive transmitter–receiver pairs.

Performance analysis of simultaneous communications in bacterial nanonetworks

Utilizing biological components for data transfer is considered as a promising technique for communications at nanoscales. The ability to store data in its DNA strands as well as natural mobility make flagellated bacteria a good candidate for such systems. The use of advanced mechanisms such as replication-based encoding and conjugation to improve the performance of bacterial nanonetworks as well as stochastic bacteria movement pattern make their performance assessment a non-trivial task. Universal analytical frameworks taking into account these mechanisms are still missing. The situation is complicated by the possibility of having more than a single transmitter–receiver (Tx–Rx) pair communicating in the environment of interest. In this paper, we develop a framework to characterize performance of the bacterial networks taking all the abovementioned mechanisms into account and capable to address the case of simultaneous communications between a number of Tx–Rx pairs. The framework is based on the absorbing Markov chains theory and allows to reveal inherent trade-offs related to delay performance of bacterial nanonetworks.

An Airborne and Ground-Based Study of a Long-Lived and Intense Atmospheric River with Mesoscale Frontal Waves Impacting California during CalWater-2014

Abstract The wettest period during the CalWater-2014 winter field campaign occurred with a long-lived, intense atmospheric river (AR) that impacted California on 7–10 February. The AR was maintained in conjunction with the development and propagation of three successive mesoscale frontal waves. Based on Lagrangian trajectory analysis, moist air of tropical origin was tapped by the AR and was subsequently transported into California. Widespread heavy precipitation (200–400 mm) fell across the coastal mountain ranges northwest of San Francisco and across the northern Sierra Nevada, although only modest flooding ensued due to anomalously dry antecedent conditions. A NOAA G-IV aircraft flew through two of the frontal waves in the AR environment offshore during a ~24-h period. Parallel dropsonde curtains documented key three-dimensional thermodynamic and kinematic characteristics across the AR and the frontal waves prior to landfall. The AR characteristics varied, depending on the location of the cross section through the frontal waves. A newly implemented tail-mounted Doppler radar on the G-IV simultaneously captured coherent precipitation features. Along the coast, a 449-MHz wind profiler and collocated global positioning system (GPS) receiver documented prolonged AR conditions linked to the propagation of the three frontal waves and highlighted the orographic character of the coastal-mountain rainfall with the waves’ landfall. A vertically pointing S-PROF radar in the coastal mountains provided detailed information on the bulk microphysical characteristics of the rainfall. Farther inland, a pair of 915-MHz wind profilers and GPS receivers quantified the orographic precipitation forcing as the AR ascended the Sierra Nevada, and as the terrain-induced Sierra barrier jet ascended the northern terminus of California’s Central Valley.

Multiuser Wireless Power Transfer via Magnetic Resonant Coupling: Performance Analysis, Charging Control, and Power Region Characterization

Magnetic resonant coupling (MRC) is an efficient method for realizing the near-field wireless power transfer (WPT). Although the MRC-enabled WPT (MRC-WPT) with a single pair of transmitter and receiver has been thoroughly studied in the literature, there is limited work on the general setup with multiple transmitters and/or receivers. In this paper, we consider a point-to-multipoint MRC-WPT system with one transmitter delivering wireless power to a set of distributed receivers. We aim to introduce new applications of signal processing and optimization techniques to the performance characterization and optimization in multiuser WPT via MRC. We first derive closed-form expressions for the power drawn from the energy source at the transmitter and that delivered to the load at each receiver. We identify a “near-far” fairness issue in multiuser power transmission due to receivers' distance-dependent mutual inductance with the transmitter. To tackle this issue, we propose a centralized charging control algorithm to jointly optimize the receivers' load resistance to minimize the total transmitter power drawn while meeting the given power requirement of each individual load. For ease of practical implementation, we also devise a distributed algorithm for the receivers to adjust their load resistance independently in an iterative manner. Last, we characterize the power region that constitutes all the achievable power-tuples of the loads via controlling their adjustable resistance. In particular, we compare the power regions without versus with the time sharing of users' power transmission, where it is shown that time sharing yields a larger power region in general. Extensive simulation results are provided to validate our analysis and corroborate our study on the multiuser MRC-WPT system.

Impact of Sun glint on the SMOS Retrieved Brightness Temperature Maps for Almost Four Years of Data

Abstract The European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite was launched on November 2nd, 2009. The purpose of this mission is to retrieve global maps of soil moisture and ocean surface salinity. The single payload on board the SMOS satellite is a two-dimensional L-band interferometer, the Microwave Imaging Radiometer with Aperture Synthesis (MIRAS). This instrument measures the cross-correlations of the signals between many pairs of receivers distributed in a Y-shaped array. After de-normalization and image reconstruction, these cross-correlations yield brightness temperature images whose usable portion extends over a swath nearly 1000 km across. Geophysical retrieval algorithms are applied to these images to yield soil moisture (SM) over land and sea surface salinity (SSS) over the ocean. This paper examines the impact of sun glint on these images, focusing on the open ocean, where sun glint is shown to have a major impact on the images in descending passes from December through January. The consistency between the sun glint present in the data and that predicted by the model developed prior to launch is assessed in terms of both spatial variation across the swath and temporal variation from June 2010 to February 2014.

Apparent source levels and active communication space of whistles of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary and Beibu Gulf, China.

Background. Knowledge of species-specific vocalization characteristics and their associated active communication space, the effective range over which a communication signal can be detected by a conspecific, is critical for understanding the impacts of underwater acoustic pollution, as well as other threats.Methods. We used a two-dimensional cross-shaped hydrophone array system to record the whistles of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in shallow-water environments of the Pearl River Estuary (PRE) and Beibu Gulf (BG), China. Using hyperbolic position fixing, which exploits time differences of arrival of a signal between pairs of hydrophone receivers, we obtained source location estimates for whistles with good signal-to-noise ratio (SNR ≥10 dB) and not polluted by other sounds and back-calculated their apparent source levels (ASL). Combining with the masking levels (including simultaneous noise levels, masking tonal threshold, and the Sousa auditory threshold) and the custom made site-specific sound propagation models, we further estimated their active communication space (ACS).Results. Humpback dolphins produced whistles with average root-mean-square ASL of 138.5 ± 6.8 (mean ± standard deviation) and 137.2 ± 7.0 dB re 1 µPa in PRE (N = 33) and BG (N = 209), respectively. We found statistically significant differences in ASLs among different whistle contour types. The mean and maximum ACS of whistles were estimated to be 14.7 ± 2.6 (median ± quartile deviation) and 17.1± 3.5 m in PRE, and 34.2 ± 9.5 and 43.5 ± 12.2 m in BG. Using just the auditory threshold as the masking level produced the mean and maximum ACSat of 24.3 ± 4.8 and 35.7 ± 4.6 m for PRE, and 60.7 ± 18.1 and 74.3 ± 25.3 m for BG. The small ACSs were due to the high ambient noise level. Significant differences in ACSs were also observed among different whistle contour types.Discussion. Besides shedding some light for evaluating appropriate noise exposure levels and information for the regulation of underwater acoustic pollution, these baseline data can also be used for aiding the passive acoustic monitoring of dolphin populations, defining the boundaries of separate groups in a more biologically meaningful way during field surveys, and guiding the appropriate approach distance for local dolphin-watching boats and research boat during focal group following.

Scheduled-links multicast routing protocol in MANETs

Dynamically changing of network topology due to node movement is considered a main challenge in providing reliable and low-cost paths in one to many ends of communication in mobile ad hoc networks. To address this challenge, this paper proposes a scheduled-links multicast routing protocol (SLMRP) based on mobility prediction. SLMRP constructs multiple scheduled paths between multicast sources and receivers. SLMRP scheduled paths are subject to reliability and quality of service requirements in load-balance strategy. Multiple loop-free and node-disjoint paths are constructed for each source–receiver pair during route discovery process. To control the activation and deactivation of these paths, we introduce multicast routing activation timer (MRAT) and path timeout timer (PTT). MRAT and PTT are computed according to the route expiration time for the set of the discovering paths. Performance comparison results demonstrate that the proposed protocol outperforms PUMA, MAODV, and PMRP.