Receiver Pair Research Articles

Cognitive Relaying Cooperation in Satellite-Terrestrial Systems With Multiuser Diversity

This paper investigates the outage performance of an overlay multiuser hybrid satellite-terrestrial spectrum sharing system. Herein, we exploit both direct and relay links from a primary satellite source to multiple terrestrial users with the coexistence of a secondary transmitter–receiver pair on the ground. Based on an overlay approach, the secondary transmitter provides an amplify-and-forward-based relay cooperation to the primary satellite network that employs opportunistic scheduling of multiple users. The underlying user scheduling strategy is based on satisfying the criterion of minimal outage probability (OP) for the primary network and, eventually, exploring more opportunities of the spectrum sharing for the secondary terrestrial network. By considering the widely adopted Shadowed-Rician fading model for the satellite links while the Nakagami- $m$ fading model for the terrestrial links, we derive the analytical expressions for the OP of the primary satellite network and the secondary terrestrial network and further highlight the corresponding achievable diversity orders. We also examine the impact of power splitting factor for spectrum sharing between primary and secondary networks.

Synchronization of low-cost distributed spectrum sensing nodes for multilateration-based geolocation

In this work, we show how a distributed sensing network consisting of very low-cost nodes can also be used to locate radio transmitters without prior knowledge of which waveform is used. This information can aid in increasing location awareness among cognitive radios, as well as provide assistance in locating offending transmitters. The low accuracy of the internal clocks of these low-cost receivers as well as the geographical distribution of the nodes result in significant challenges regarding the synchronization of the receivers in order to position the source with adequate accuracy. In this article, we synchronize the nodes to an arbitrary modulated RF signal, after which we calculate estimated time differences of arrival to an unknown transmitter. We describe the implementation as well as give results on measurement accuracy in various scenarios using a prototype network of nodes spread out in the city of Turku, Finland. In the individual distance measurements of receiver pairs, the errors in distances vary between 30 and 900 m, depending on channel conditions.

On Link Scheduling in Dual-Hop 60-GHz mmWave Networks

We tackle the problem of minimizing the maximum expected delivery time of all transmission pairs in 60 GHz mmWave networks. The network is dual-hop with multiple transmitter-receiver pairs, relays, and a centralized controller (termed PicoNet coordinator). We jointly optimize relay and link selection for the transmitter–receiver pairs to minimize delivery time, while the reflected non-line-of-sight transmission links are exploited to get around obstacles. To reduce computational complexity, we develop a decomposition principle to transform the joint-optimization problem into a link selection subproblem and a relay assignment subproblem when there are a sufficient amount of relays. A tight performance bound for the proposed algorithm is proved. We also develop a heuristic scheme to handle the case when there are no enough relays. The superior performance of our proposed algorithms is validated with extensive simulations and comparisons with benchmark schemes.

On the accuracy of the GPS L2 observable for ionospheric monitoring

The introduction of the unencrypted global positioning system (GPS) L2 civil (L2C) signal has the potential to improve measurements made with the L2 frequency, an important observable in GPS-based ionospheric research and monitoring. Recent work has shown significant differences between the legacy L2P(Y) and L2C-derived total electron content rate of change index (ROTI). This difference is observed between L2P(Y) and L2C-derived ROTI with certain receiver models and between zero-baseline receiver pairs. We discuss the likely cause for these differences: L1-aided tracking used to track both the L2P(Y) and L2C signals. We also present L2C data that are confirmed to be from tracking independent of L1. Using the ionospheric-free linear combination, we show that the independently tracked carrier phase dynamics are significantly more accurate than the L1-aided observables. This result is confirmed by comparing the behavior of the L2C and L2P(Y) carrier phase observables upon a sudden antenna rotation.

0.4 THz Photonic-Wireless Link With 106 Gb/s Single Channel Bitrate

To accommodate the demand of exponentially increased global wireless data traffic, the prospective data rates for wireless communication in the market place will soon reach 100 Gb/s and beyond. In the lab environment, wireless transmission throughput has been elevated to the level of over 100 Gb/s attributed to the development of photonic-assisted millimeter wave and terahertz (THz) technologies. However, most of recent demonstrations with over 100 Gb/s data rates are based on spatial or frequency division multiplexing techniques, resulting in increased system's complexity and energy consumption. Here, we experimentally demonstrate a single channel 0.4 THz photonic-wireless link achieving a net data rate of beyond 100 Gb/s by using a single pair of THz emitter and receiver, without employing any spatial/frequency division multiplexing techniques. The high throughput up to 106 Gb/s within a single THz channel is enabled by combining spectrally efficient modulation format, ultrabroadband THz transceiver and advanced digital signal processing routine. Besides that, our demonstration from system-wide implementation viewpoint also features high transmission stability, and hence shows its great potential to not only decrease the system's complexity, but also meet the requirements of prospective data rates for bandwidth-hungry short-range wireless applications.

GPS receiver phase biases estimable in PPP-RTK networks: dynamic characterization and impact analysis

The integer ambiguity resolution enabled precise point positioning (PPP-RTK) has been proven advantageous in a wide range of applications. The realization of PPP-RTK concerns the isolation of satellite phase biases (SPBs) and other corrections from a network of Global Positioning System (GPS) reference receivers. This is generally based on Kalman filter in order to achieve real-time capability, in which proper modeling of the dynamics of various types of unknowns remains crucial. This paper seeks to gain insight into how to reasonably deal with the dynamic behavior of the estimable receiver phase biases (RPBs). Using dual-frequency GPS data collected at six colocated receivers over days 50–120 of 2015, we analyze the 30-s epoch-by-epoch estimates of L1 and wide-lane (WL) RPBs for each receiver pair. The dynamics observed in these estimates are a combined effect of three factors, namely the random measurement noise, the multipath and the ambient temperature. The first factor can be overcome by turning to a real-time filter and the second by considering the use of a sidereal filtering. The third factor has an effect only on the WL, and this effect appears to be linear. After accounting for these three factors, the low-pass-filtered, sidereal-filtered, epoch-by-epoch estimates of L1 RPBs follow a random walk process, whereas those of WL RPBs are constant over time. Properly modeling the dynamics of RPBs is vital, as it ensures the best convergence of the Kalman-filtered, between-satellite single-differenced SPB estimates to their correct values and, in turn, shortens the time-to-first-fix at user side.

BER analysis and power control for interfering visible light communication systems

This paper studies the error performance of visible light communication systems consisting of multiple transmitter–receiver pairs, where mutual interference exists. Unlike the traditional method which approximates the interference signal as a Gaussian random process and express the bit error rate (BER) as a function of the signal-to-interference-plus-noise power ratio (SINR), we conduct a detailed analysis that captures the signal structure of the interference in terms of the number of light sources, and derive the BER explicitly. Simulation results show that under a realistic small-room scenario with basic illumination requirement, the BER predicted by the Gaussian model is much higher than the exact BER. To provide an alternative metric for resource allocation purpose, we also propose a new approximate expression for the BER. A power control problem is further investigated to ensure that the system is operated in an effective manner.

반복적 연산을 이용하는 Distributed MIMO 레이다 시스템의 위치 추정 기법

This paper presents a target localization scheme for distributed Multi-input Multi-output(MIMO) radar system using ToA measurements obtained from multiple transmitter and receiver pairs. The proposed method can locate the target from an arbitrary initial point by iteratively finding the Taylor linear approximation equation. The simulation results show that proposed method achieves the better mean square error(MSE) performance than the existing target localization methods, and furthermore, attains Cramer-Rao Lower Bound(CRLB).

Acoustic characterization of the new Arctic using mobile acoustic sources

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 the remote Ice Camp SARGO, NPS deployed several conductivity, temperature and depth (CTD) sensors to capture oceanographic variability to 500 m depth while performing a series of propagation tests. Four mobile mid-frequency sources transmitted signals for approximately 10 hours each 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 indicated significant variability in sound speed at 50 m 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 pe...

Epitaxial PMnN-PZT/Si MEMS ultrasonic rangefinder with 2 m range at 1 V drive

In this study, we successfully developed a high signal-to-noise ratio (SNR) rangefinder based on a piezoelectric micromachined ultrasonic transducer (pMUT). A c-axis-oriented Pb(Mn1/3,Nb2/3)O3-Pb(Zr,Ti)O3 (PMnN-PZT) epitaxial thin film was employed as a piezoelectric transducer considering its outstanding figures-of-merit for SNR, due to the high piezoelectric coefficient and small relative permittivity (typical values: e31,f=−14C/m2, εr=200–300). The pMUTs was based on an epitaxial PMnN-PZT/Si diaphragm structure and prototyped from a SOI substrate; its rangefinding ability was evaluated with a pair of devices, specifically, transmitter and receiver, respectively. As a result, the maximum range was estimated to be over 2m at a low actuating voltage of 1Vp-p, when 12dB was set as the threshold SNR. The energy consumption of the transmitter was as small as ∼5nJ for the generation of a 50-cycle ultrasonic burst. The noise analysis of the receiver’s charge amplifier circuit indicated that this system could be improved by the optimization of bandwidth and by eliminating external noise. We believe that this high performance pMUT rangefinder will be utilized in various applications of consumer electronics or as an alternative to the bulk piezoelectric ceramic rangefinder in the near future.

Simultaneous Teleportation of Arbitrary Two-qubit and Two Arbitrary Single-qubit States Using A Single Quantum Resource

In this paper we present a teleportation protocol by which the multitask of transfer of a two-qubit and two single-qubit quantum states is performed simultaneously with the help of a single entangled channel. The protocol is under the supervision of a controller. There are three pairs of senders and receivers who are connected among themselves along with the controller by a single entangled state. The teleportation protocol is perfect.

Secure Degrees of Freedom of the Asymmetric Gaussian MIMO Interference Channel

We study the secure degrees of freedom (s.d.o.f.) for a two-user multiple-input multiple-output (MIMO) Gaussian interference channel with confidential messages, each transmitter–receiver pair of which intends to keep secret from the other pair. Different from existing works on symmetric scenario, in this paper, an asymmetric system is considered, where transmitters have $M_1$ , $M_2$ antennas and receivers have $N_1$ , $N_2$ antennas, respectively. The channel is assumed to be fast fading and channel matrices are fixed and full rank. We subdivide the problem into several regimes based on the configuration of antennas at each node and present the exact secure degrees of freedom of corresponding regime. To prove a converse, the outer bound is developed by combining information theoretic derivation and the results of fundamental models. We also provide the achievable schemes based on zero forcing, real interference alignment, and cooperative jamming. One part of private signal is sent in the null space, while the other part is sent in a way that it aligns with cooperative jamming signal at unintended receiver, but leaves the secret message intact at intended receiver. As a consequence of the scheme, the objective s.d.o.f. can be achieved and the system ensures that the confidential messages cannot be eavesdropped by unintended receivers.

Performance of uncoordinated coexistence mechanisms in adhoc networks

Dynamic spectrum sharing between uncoordinated devices is impaired by interference. Simple coexistence mechanism can reduce this interference and improve network performance. We analyze performance of some simple coexistence mechanisms in detail, where the decision to transmit a packet by a given device to its intended receiver is taken solely by the transmitter receiver pair without any central control. Accurate interference models are developed assuming a large number of transmitter-receiver pairs that are randomly distributed according to a Poisson spatial point process. These are used to derive accurate expressions for packet error rates in the case of direct sequence code division multiple access physical layer model and slotted packet transmission schemes. These results are then used to study the performance of the coexistence mechanisms and compare them with each other.

Improving Wireless Physical Layer Security Using Constant Envelope Chirped OFDM

The broadcasting nature of wireless communication creates challenges in attaining secure communication. Different approaches have been implemented to increase security in wireless communication with physical layer security being affordable choices as it attains secure communication with the same throughput and easily integrated with higher level security measures. Different physical characteristics of wireless channels can be exploited to implement physical layer security and in our research channel attenuation between transmitter and receiver were used. To provide cost effective and secure wireless communication we used constant envelope chirped OFDM (CE-chirped OFDM) with its subcarriers dynamically arranged based on the wireless channel response between the transmitter and a legal receiver. The security is further increasing by assigning identification number for each transmitter–receiver pair and the identifications numbers are boost arrangement of the subcarriers and increase system security. Different simulations were conducted and the simulations shows increase of system security when wireless channel attenuation of CE chirped OFDM is used to secure the communication between transmitter and legal receiver with the same symbol error rate as convectional OFDM and chirped OFDM.

MIMO Cooperative Cognitive Radio Relay Networks With Uniquely Factorable Signal Transmission

In this paper, we consider a cooperative cognitive radio relay network (CCRRN), in which there is a pair of primary transmitter (PT) and primary receiver (PR) with each having a single antenna, a secondary transmitter (ST) equipped with two antennas and a secondary receiver (SR) having a single antenna. We assume that ST operates in a half-duplex mode with an amplify-and-forward cooperative transmission scheme adopted. For such a system, a novel transmission scheme for CCRRN based on uniquely-factorable constellation pair is proposed, which enables ST to transmit its own information to SR without knowing its channel links to PR and SR while assisting PT transmission. It is shown that one of the significant advantages of our proposed new scheme is that, in a noise-free case, PR and SR are able to decode their own signals uniquely and that, in a Gaussian noise case, they are still able to reliably decode their own signals with full diversity. In addition, a tight upper bound of average pairwise error probability for the maximum-likelihood detector is derived, showing that full diversity is achieved. With this, an optimal power allocation strategy is proposed that minimizes the worst-case upper bound.

Damage Detection Through Pipe Bends

Axial pipeline defects are detectable from torsional guided wave reflections through 90 deg elbows. This paper demonstrates that detection of localized damage in carbon steel pipes with a so-called standard long and very long radius elbow is possible using a single permanently installed source–receiver pair. We use dispersion imaging to determine why this is not possible in a short radius elbow pipe. Although the remote damage is detected in a standard short radius bend pipe, there is not enough signal to detect localized damage. Since pipeline bends are normally of at least standard long radius, the acoustical behavior is similar to that previously determined in straight pipes. The reflective method can thus be applied fruitfully to monitor structural health beyond industrial pipeline bends.

Physical-Layer Cryptography Through Massive MIMO

We propose the new technique of physical-layer cryptography based on using a massive MIMO channel as a key between the sender and desired receiver, which need not be secret. The goal is for low-complexity encoding and decoding by the desired transmitter-receiver pair, whereas decoding by an eavesdropper is hard in terms of prohibitive complexity. The decoding complexity is analyzed by mapping the massive MIMO system to a lattice. We show that the eavesdropper's decoder for the MIMO system with M-PAM modulation is equivalent to solving standard lattice problems that are conjectured to be of exponential complexity for both classical and quantum computers. Hence, under the widely-held conjecture that standard lattice problems are hard to solve in the worst-case, the proposed encryption scheme has a more robust notion of security than that of the most common encryption methods used today such as RSA and Diffie-Hellman. Additionally, we show that this scheme could be used to securely communicate without a pre-shared secret and little computational overhead. Thus, by exploiting the physical layer properties of the radio channel, the massive MIMO system provides for low-complexity encryption commensurate with the most sophisticated forms of application-layer encryption that are currently known.

Probabilistic Jamming/Eavesdropping Attacks to Confuse a Buffer-Aided Transmitter–Receiver Pair

We assume that a buffer-aided transmitter communicates with a receiving node in the presence of an attacker. We investigate the impact of a radio-frequency energy-harvesting attacker that probabilistically operates as a jammer or an eavesdropper. We show that even without the need for an external energy source, the attacker can still degrade the security of the legitimate system. We show that the random data arrival behavior at the transmitter and the channel randomness of the legitimate link can improve the system’s security. We design a jamming scheme for the attacker and investigate its impact on the secure throughput of the legitimate system. The attacker designs his power splitting parameter and jamming/eavesdropping probability based on the energy state of the attacker’s battery to minimize the secure throughput of the legitimate system.

An Efficient Weighted Least Squares Estimator for Elliptic Localization in Distributed MIMO Radars

Elliptic localization is an active range-based positioning technique that employs multiple transmitter–receiver pairs, each of which is able to provide separate bistatic range (BR) measurement. In this letter, an algebraic closed-form method for locating a single target from BR measurements using a distributed multiple-input multiple-output (MIMO) radar system is proposed. First, a set of linear equations is established by eliminating the nuisance parameters, and then, a weighted least squares estimator is employed to obtain the target position estimate. To refine the localization performance, the error in the initial solution is estimated in the sequence. The proposed method is shown analytically and corroborated by simulations to be an approximately unbiased estimation, which is able to reach the Cramer–Rao lower bound accuracy under mild noise conditions. Numerical simulations demonstrate the superiority of this algorithm over the existing methods.

Physical Layer Security in Wireless Ad Hoc Networks Under A Hybrid Full-/Half-Duplex Receiver Deployment Strategy

This paper studies physical layer security in a wireless ad hoc network with numerous legitimate transmitter–receiver pairs and eavesdroppers. A hybrid full-duplex (FD)/half-duplex receiver deployment strategy is proposed to secure legitimate transmissions, by letting a fraction of legitimate receivers work in the FD mode sending jamming signals to confuse eavesdroppers upon their information receptions, and letting the other receivers work in the half-duplex mode just receiving their desired signals. The objective of this paper is to choose properly the fraction of FD receivers for achieving the optimal network security performance. Both accurate expressions and tractable approximations for the connection outage probability and the secrecy outage probability of an arbitrary legitimate link are derived, based on which the area secure link number, network-wide secrecy throughput, and network-wide secrecy energy efficiency are optimized, respectively. Various insights into the optimal fraction are further developed, and its closed-form expressions are also derived under perfect self-interference cancellation or in a dense network. It is concluded that the fraction of FD receivers triggers a non-trivial tradeoff between reliability and secrecy, and the proposed strategy can significantly enhance the network security performance.