Weak Interference Research Articles

A Review on Missing Tags Detection Approaches in RFID System

Radio Frequency Identification (RFID) system can provides automatic detection on very large number of tagged objects within short time. With this advantage, it is been using in many areas especially in the supply chain management, manufacturing and many others. It has the ability to track individual object all away from the manufacturing factory until it reach the retailer store. However, due to its nature that depends on radio signal to do the detection, reading on tagged objects can be missing due to the signal lost. The signal lost can be caused by weak signal, interference and unknown source. Missing tag detection in RFID system is truly significant problem, because it makes system reporting becoming useless, due to the misleading information generated from the inaccurate readings. The missing detection also can invoke fake alarm on theft, or object left undetected and unattended for some period. This paper provides review regarding this issue and compares some of the proposed approaches including Window Sub-range Transition Detection (WSTD), Efficient Missing-Tag Detection Protocol (EMD) and Multi-hashing based Missing Tag Identification (MMTI) protocol. Based on the reviews it will give insight on the current challenges and open up for a new solution in solving the problem of missing tag detection.

Secrecy Sum-Rate Enhancement in the Interference Channel via Price-Based Power Splitting

This letter proposes a game-theoretic model to jointly optimize artificial noise and information signals in a two-user weak Gaussian interference channel. In this channel, each receiver not only is interested in its related transmitter’s message, but also it is an eavesdropper for the other link. Transmitters may broadcast noise in addition to data in order to confuse eavesdroppers. In this context, the secrecy rate is referred to as the utility, and the Nash equilibrium outcome in the related non-cooperative power splitting game is inefficient. By introducing a novel price-based potential game, we obtain Pareto improvement in the secrecy sum-rate. Numerical results confirm our analytical development.

Propagation law of hydraulic fractures during multi-staged horizontal well fracturing in a tight reservoir

Abstract A novel laboratory simulation method for modeling multi-staged fracturing in a horizontal well was established based on a true tri-axial hydraulic fracturing simulation system. Using this method, the influences of net pressure in hydraulic fracture, stage spacing, perforation parameter, horizontal stress bias and well cementation quality on the propagation geometry of multiple fractures in a tight sandstone formation were studied in detail. The specimen splitting and analogy analysis of fracturing curve patterns reveals: Multiple fractures tend to merge under the condition of high horizontal stress bias and short stage spacing with pre-existing hydraulic fractures under critical closure situation, and the propagation of subsequent fractures is possibly suppressed because of high net pressure in pre-created fractures and asymmetric distribution of fracture width. And the subsequently created fractures are situated in the induced stress decreasing zone due to long stage spacing, leading to weak stress interference, and perforation with intense density and deep penetration facilitates the decrease of initiation fracture pressure. The deflection angle of subsequent fracture and horizontal stress variation tend to be amplified under low horizontal bias with constant net pressure in fractures. The longitudinal fracture is likely to be initiated at the interface of wellbore and concrete sample with poor cementation quality. The initiation fracture pressure of the different stages increases in turn, with the largest increase of 30%. Pressure quickly declines after initiation with low propagation pressure when the transverse hydraulic fracture is formed. The pressure reduces with fluctuation after the initiation of fracture when the fracture deflects, the extension pressure is high, and the fracture formed is tortuous and narrow. There is a violently fluctuant rise of pressure with multiple peak values when longitudinal fracture created, and it is hard to distinguish the features between the initiation stage and propagation stage.

Determination of antimony in soil using laser-induced breakdown spectroscopy assisted with laser-induced fluorescence.

Antimony (Sb) in soil is attracting attention in the research community due to its potential toxicity and carcinogenicity. Traditional methods of detecting Sb lack the ability of rapid and nondigestion analysis, which hinders their development and application. Moreover, it is still a challenge for laser-induced breakdown spectroscopy (LIBS) to detect Sb in soil due to the weak intensities and intense interference of spectral lines. Here, LIBS, assisted with laser-induced fluorescence (LIBS-LIF), was used to selectively enhance the Sb's characteristic spectral lines under optimal parameters. The quantitative analysis performance was notably improved with a determination coefficient (R2) of 0.991, the limit of detection of 0.221μg/g, and root mean square error of cross validation of 3.592μg/g. These results demonstrate that LIBS-LIF has the potential to realize the rapid and accurate analysis of Sb in soil.

Communications System Performance and Design in the Presence of Radar Interference

Increasing demands for spectrum have necessitated the coexistence of communications and radar systems within the same band. This paper investigates how an unaltered radar system affects the performance of a communications receiver. For a single-carrier communications system, it is shown that a low power radar signal can be treated as Gaussian noise while a strong radar signal can be subtracted off the received signal, but in doing so one of the two signal dimensions is lost. Complex-valued constellation design problems are next proposed, with the goal of either minimizing the error rate under a power constraint, or maximizing the transmission rate under both error rate and power constraints. Numerically, the designed constellation is shaped as a concentric hexagon for weak radar interference while it morphs into an uneven pulse amplitude modulation for strong interference. A multi-carrier orthogonal frequency division multiplexing communications system is lastly considered. Due to the radar interference, the received signal becomes correlated over time and across carriers. To reduce the complexity of the optimal receiver, several suboptimal decoders are analyzed, among which the one that discards the correlations between subcarriers is numerically found to perform close to the optimal one.

Engineered photoelectrochemical platform for the ultrasensitive detection of caffeic acid based on flower-like MoS2 and PANI nanotubes nanohybrid

As a newly emerged and rapidly developing analysis technique, photoelectrochemical detection has received increasing attention due to its satisfactory sensitivity, weak background interference signal and remarkable analytical performances. Accordingly, a novel photoelectrochemical platform for the ultrasensitive detection of caffeic acid has been developed based on flower-like MoS2 and PANI nanotubes nanohybrid. Remarkably, owing to the sufficient photogenerated electron-hole pairs originated from the flower-like MoS2 and efficient electron transfer on PANI under visible light irradiation, the linear range of caffeic acid was found to be 0.2 to 110.51μM, 110.51 to 482 μM with a detection limit of 0.13 μM by DPV technique and meanwhile the linear range of caffeic acid was found to be 1.02 to 520 μM with detection a limit of 0.76 μM by i-t curves. More interestingly, the PANI nanotubes supported flower-like MoS2 also exhibited high durability with negligible decay after long-term detection, showing an excellent photo-current enhanced performance to the photoelectrochemical detection.

Interference identification in smart grid communications

The TD-LTE wireless private network for electric power systems is an important component of smart grids, and coverage analysis and interference identification are essential in operating and optimizing of power wireless private networks. This paper presents an approach to analyzing indoor and outdoor coverage scopes of cell radio signals and recognizing locations and sources of intra-network interference in the network deployed in a dense urban environment. This approach takes scenario modeling to represent terrain and on-ground objects given by digital maps, utilizes ray tracing to track the signal propagation trajectories, and calculates strength attenuation of radio signals due to signal propagation such as direct transmission, reflection, diffraction and refraction. The uniform grid is employed as the acceleration structure to speed up tracing signal propagation paths, and drive-testing measurement data and scenario-oriented propagation model calibration are used to improve analysis accuracy. Weak coverage spots and interference defect spots are defined and used to identify interference types and sources. We applied the approach to a tentative TD-LTE power wireless private network in a southern city in China, proving that the ray-tracing-based scheme is able to make precise analysis on coverage and interference in practical networks.

State-Dependent Interference Channel With Correlated States

This paper investigates the Gaussian state-dependent interference channel (IC) and Z-IC, in which two receivers are corrupted respectively by two different but correlated states that are noncausally known to two transmitters but are unknown to the receivers. Three interference regimes are studied, and the capacity region boundary or the sum capacity boundary is characterized either fully or partially under various channel pa- rameters. In particular, the impact of the correlation between states on cancellation of state and interference as well as achievability of capacity is explored with numerical illustrations. For the very strong interference regime, the capacity region is achieved by the scheme where the two transmitters implement a cooperative dirty paper coding. For the strong but not very strong interference regime, the sum-rate capacity is char- acterized by rate splitting, layered dirty paper coding and successive cancellation. For the weak interference regime, the sum-rate capacity is achieved via dirty paper coding individually at two receivers as well as treating interference as noise.

Downlink Beamforming for Energy-Efficient Heterogeneous Networks With Massive MIMO and Small Cells

A heterogeneous network (HetNet) of a macrocell base station equipped with a large-scale massive multi-in multi-out (MIMO) antenna array overlaying a number of small cell base stations (small cells) can provide high quality of service (QoS) to multiple users under low transmit power budget. However, the circuit power for operating such a network, which is proportional to the number of transmit antennas, poses a problem in terms of its energy efficiency (EE). This paper addresses the beamforming design at the base stations to optimize the network EE under the QoS constraints and a transmit power budget. Beamforming tailored for weak, strong, and medium cross-tier interference HetNets is proposed. In contrast to the conventional transmit strategy for power efficiency in meeting the users’ QoS requirements, which suggest the use of a few hundred antennas, it is found out that the overall network EE quickly drops if this number exceeds 50. It is found that, for a given number of antennas, HetNet is more energy efficient than massive MIMO when considering the overall energy consumption.

Across-wind excitation mechanism for interference of twin tall buildings in staggered arrangement

This paper explores the excitation mechanism for across-wind force interference of two tall buildings in staggered arrangement through detailed measurement of turbulent flow fields past the two buildings and concurrent pressure measurement on the downstream principal building. Analysis of the instantaneous flow fields and wall pressure distributions reveals a synchronization process between the sideway oscillation of the upstream building wake with vortex development and shedding from the downstream principal building. Further analysis using the phase averaging technique confirms that the synchronization of five quasi-periodic aerodynamic phenomena is responsible for the magnification of across-wind force fluctuations in a region of building arrangements centered at a longitudinal building separation of 5 building breaths (D) and a lateral separation of 2.5D. In addition to this “wake interference region I”, three other flow regions of staggered arrangement are classified, namely, “wake interference region II” in which wake development on the principal building is affected by impingement of the meandering upstream building wake in a close lateral separation, “proximity interference region” which is characterized by channeled flow through a narrow gap between the two buildings, and “weak interference region”.

Pressure-Transient Behavior of Multisegment Horizontal Wells With Nonuniform Production: Theory and Case Study

Field data indicate production profile along horizontal wells is nonuniform. This paper develops an analytical model of multisegment horizontal wells (MSHWs) to estimate rate distribution along horizontal wellbore, interpret the effective producing length (EPL), and identify underperforming horizontal sections using bottom-hole pressure (BHP) data. Pressure solutions enable to model an MSHW with nonuniform distribution of length, spacing, rate, and skin factor. The solution is verified with the analytical solution in commercial software. Type curves are generated to analyze the pressure-transient behavior. The second radial-flow (SRF) occurs for the MSHWs, and the duration of SRF depends on interference between segments. The pressure-derivative curve during SRF equals to 0.5/Np (Np denotes the number of mainly producing segments (PS)) under weak interference between segments. The calculated average permeability may be Np times lower than accurate value when the SRF is misinterpreted as pseudoradial-flow regime. The point (0, 0, h/2) are selected as the reference point, and symmetrical cases will generate different results, enabling us to distinguish them. Finally, field application indicates the potential practical application to identify the underperforming horizontal segments.

Throughput analysis of wireless-powered decode-and-forward relay systems with interference

This paper investigates the throughput of a wireless-powered dual-hop relaying system with the presence of co-channel interference. Specifically, an energy-constrained source node communicates with a destination node through an energy-constrained decode-and-forward relay node. Considering a time-splitting approach, both source and relay are first powered by a dedicated power beacon (PB), whereas the relay further exploit the benefit from the interfering signals as a plentiful power supply. Then, source transmits information to the destination with the help of the relay. The instantaneous throughput of the system is maximized by optimizing the time-split parameter. In order to determine the average throughput of the system in delay-limited transmission mode, analytical expressions for the outage probability are derived. In addition, we present asymptotic outage expressions under strong interference conditions. Our results, reveal that by energy harvesting from the interfering signals at the relay, the instantaneous throughput is increased compared with the case where the relay is only powered by the PB. Moreover, under strong interference conditions the optimal time-split that maximize the throughput of the the delay-limited transmission mode is much higher than that for weak interference condition.

On the Capacity of the AWGN Channel With Additive Radar Interference

This paper investigates the capacity of a communications channel that, in addition to additive white Gaussian noise, also suffers from interference caused by a co-existing radar transmission. The radar interference (of short duty-cycle and of much wider bandwidth than the intended communication signal) is modeled as an additive term whose amplitude is known and constant, but whose phase is independent and identically uniformly distributed at each channel use. The capacity achieving input distribution, under the standard average power constraint, is shown to have independent modulo and phase. The phase is uniformly distributed in $[0,2\pi]$. The modulo is discrete with countably infinitly many mass points, but only finitely many in any bounded interval. From numerical evaluations, a proper-complex Gaussian input is seen to perform quite well for weak radar interference. We also show that for very large radar interference, capacity is equal to $1/2\log (1 + S)$ and a proper-complex Gaussian input achieves it. It is concluded that the presence of the radar interference results in a loss of half of the degrees of freedom compared to an AWGN channel without radar interference.

The Generalized Degrees of Freedom Region of the MIMO Z-Interference Channel With Delayed CSIT

The generalized degrees of freedom (GDoF) region of the multiple-input multiple-output (MIMO) Gaussian Z-interference channel with an arbitrary number of antennas at each node is established under the assumption of delayed channel state information at transmitters (CSIT). The GDoF region is parameterized by $\alpha$ , which links the interference-to-noise ratio (INR) to the signal-to-noise ratio (SNR) via $\mathrm {INR}=\mathrm {SNR}^{\alpha }$ . A new outer bound for the GDoF region is established by maximizing a bound on the weighted sum-rate of the two users, which in turn is obtained by using a combination of genie-aided side-information and an extremal inequality. The maximum weighted sum-rate in the high SNR regime is shown to occur when the transmission covariance matrix of the interfering transmitter has full rank. An achievability scheme based on block-Markov encoding and backward decoding is developed which uses interference quantization and digital multicasting to take advantage of the channel statistics of the cross-link, and the scheme is separately shown to be GDoF-optimal in both the weak ( $\alpha \leq 1$ ) and strong ( ${\alpha >1}$ ) interference regimes. This is the first complete characterization of the GDoF region of any interference network with delayed CSIT, as well as the first such GDoF characterization of a MIMO network with delayed CSIT and arbitrary number of antennas at each node. For all antenna tuples, the GDoF region is shown to be equal to or larger than the degrees of freedom (DoF) region over the entire range of $\alpha$ , which leads to a V-shaped maximum sum-GDoF as a function of $\alpha$ , with the minimum occurring at $\alpha =1$ . The delayed CSIT GDoF region and the sum-DoF are compared with their counterparts under perfect CSIT, thereby characterizing all antenna tuples and ranges of $\alpha$ for which delayed CSIT is sufficient to achieve the perfect CSIT GDoF region (or sum-DoF). It is also shown that treating interference as noise is not, in general, GDoF-optimal for the MIMO Z-IC, even in the weak interference regime.

Two-Timescale User-Centric RRH Clustering and Precoding Optimization for Cloud RAN via Local Stochastic Cutting Plane

In a cloud radio access network (C-RAN), many distributed remote radio heads (RRHs) are connected to a centralized baseband unit pool via high-speed fronthaul links. Such an architecture improves the spectral efficiency but suffers from huge implementation costs. We propose a mixed timescale radio interference processing framework to optimize the tradeoff between the average weighted sum rate and the implementation cost in the C-RAN downlink. The radio interference processing is decomposed into short-term precoding and long-term user-centric RRH clustering (UCRC) subproblems. The short-term precoding subproblem can be solved using a modified weighted minimum mean squared error approach. To solve the challenging UCRC subproblem, we first propose a novel approximate stochastic cutting plane algorithm . Then, we bound the optimality gap of the proposed overall solution, and establish its asymptotic optimality in the weak interference and high SNR regimes. Simulations show that the proposed two-timescale solution achieves a better tradeoff performance than the baselines.

Blind separation of asymmetric signals based on Synchrosqueezing Wavelet Transform

A blind separation algorithm based on synchronous squeezing wavelet transform is proposed to solve the blind separation problem of single channel asymmetric signals in satellite communications. First, the algorithm is used to synchronize the strong signal. Then, the signal time-frequency curve is extracted by synchronous extrusion wavelet transform. Finally, the weak signal interference is filtered out from the mixed signal except the noise and the main frequency of the strong signal. Therefore, the ber of the strong signal demodulation is reduced. The algorithm has the characteristics of blind separation of single channel asymmetric signals without prior information sequence sent by cooperative communicators. The simulation results show that the performance of strong signal demodulation error is better than that of mixed signal direct hard decision.

Temperature and impurity effect on parallel field magnetoconductance of bulk insulating topological insulator (Bi1−xSbx)2Te3

We have performed a systematic parallel field magnetotransport studies of (Bi1−xSbx)2Te3 to understand the temperature and impurity effect on the interference of bulk conductance on the surface states of highly insulating topologically insulating compound Bi2Te3. The compound exhibits a weak antilocalization effect (WAL) at low temperature and low magnetic field. WAL weakens and a weak localization effect is observed to be developed in the compound with the increase in temperature due to the creation of topologically trivial 2D electron gas states. Strong interlayer interference and coupling of bulk carriers with surface states are observed at low temperature. A similar temperature effect is observed for all concentrations of Sb. Topologically protected surface states enhance with the increase in Sb contents up to x = 0.3; however, a further increase in Sb concentration leads to a decrease in surface states. The data has been analysed via the generalised Altshuler and Aronov model for parallel field transport anticipating weak antilocalization and interlayer interference.

Fully differential study of dissociative single capture and Coulomb explosion through double capture in p+H2 collisions

We have measured fully differential cross sections for dissociative single capture and Coulomb explosion through double capture in 75 keV $p+{\mathrm{H}}_{2}$ collisions. Data were analyzed for fixed kinetic energy releases and molecular orientations as a function of scattering angle. Two-center interference was identified for dissociative single capture. The interference pattern is not inconsistent with the symmetry of the dissociative electronic state affecting the phase angle of the interference term. No clear signatures of single-center interference were observed for either process. For double capture at most only a very weak two-center interference structure was found. This very small (or zero) visibility can probably be attributed to a convolution of two independent scatterings of the projectile with the two electrons yielding the measured scattering angle.

Multiple-Layer Power Allocation for Two-User Gaussian Interference Channel

Interference has been a key challenge to wireless networks. As a fundamental transmission unit, the Gaussian interference channel (GIC) provides much insight on understanding the optimal transmission policy and the transmission limit over wireless networks. This paper investigates the multiple-layer power allocation of GIC that maximizes the system sum-rate. First, we derive the optimal signal-layer power allocation and the corresponding sum-rate in closed form for all cases of weak interference GIC based on the rate splitting scheme. Theoretical result indicates that: 1) In low power and asymmetric power regimes, the rate splitting scheme degrades to the pure public or private message transmission at transmitters and simple successive decoding process is efficient enough at receivers and 2) the signal-layer sum-rate is not concave for weak interference GIC and a frequency division scheme brings strict positive sum-rate gain for some power constraints. Second, we specify the relationship between the optimal bandwidth-power allocation of the frequency division scheme and the concave envelope of signal-layer sum-rate in the subband-layer. Finally, considering general GIC with time-varying flat fading, we present an optimal channel-state-layer power allocation associated with rate splitting and frequency division. Numerical results demonstrate that the comprehensive power allocation over the signal-layer, the frequency subbands, and the channel states can largely increase the sum-rate of weak interference GIC in most scenarios.

On the Capacity and the Optimal Sum-Rate of a Class of Dual-Band Interference Channels

We study a class of two-transmitter two-receiver dual-band Gaussian interference channels (GIC) which operates over the conventional microwave and the unconventional millimeter-wave (mm-wave) bands. This study is motivated by future 5G networks where additional spectrum in the mm-wave band complements transmission in the incumbent microwave band. The mm-wave band has a key modeling feature: due to severe path loss and relatively small wavelength, a transmitter must employ highly directional antenna arrays to reach its desired receiver. This feature causes the mm-wave channels to become highly directional, and thus can be used by a transmitter to transmit to its designated receiver or the other receiver. We consider two classes of such channels, where the underlying GIC in the microwave band has weak and strong interference, and obtain sufficient channel conditions under which the capacity is characterized. Moreover, we assess the impact of the additional mm-wave band spectrum on the performance, by characterizing the transmit power allocation for the direct and cross channels that maximizes the sum-rate of this dual-band channel. The solution reveals conditions under which different power allocations, such as allocating the power budget only to direct or only to cross channels, or sharing it among them, becomes optimal.