Cancellation Process Research Articles

Iterative Self-Interference Mitigation in Full-Duplex Wireless Communications

This paper considers a full-duplex wireless communication system in which detection of the desired signal is hindered not only by the self-interference (SI), but also phase noise, in-phase and quadrature-phase imbalance and power amplifier’s nonlinearity distortion. An iterative algorithm is proposed in which the processes of SI cancellation and detection of the desired signal aid each other in each iteration. In each iteration, the SI cancellation process performs widely linear estimation of the SI channel and compensates for physical impairments to improve the detection performance of the desired signal. The detected desired signal is in turn removed from the received signal to improve SI channel estimation and SI cancellation in the next iteration. Simulation results show that the proposed algorithm significantly outperforms existing algorithms in SI cancellation and detection of the desired signal.

Experimental demonstration of blind equalization for OFDM/OQAM-VLC system

Orthogonal frequency-division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) in direct-detection system obtains many benefits such as free of cyclic prefix (CP) and high side-lobe suppression ratio in comparison with CP-OFDM signal. Unfortunately, for OFDM/OQAM signal, it needs an extra interference cancellation process to eliminate the imaginary intrinsic interference (IMI) when using one-tap frequency equalization known as interference approximation method (IAM). Blind equalization without a pilot overhead for OFDM/OQAM signal is proposed and experimentally demonstrated in visible light communication (VLC) system with limited modulation bandwidth. Experimental results show that blind equalization for OFDM/OQAM-VLC can effectively eliminate the IMI effect and can exhibit better symbol error rate on different subcarriers. Furthermore, compared with conventional IAM, it exhibits 3.2 and 2.7 dB overall improvement in Q2-factor using blind equalization based on the constant modulus algorithm and constant norm algorithm, respectively. In addition, the system can achieve a total data rate of 3.96 Gb / s over 5-m free space link with a bit error rate lower than hard-decision forward error correction limit of 3.8 × 10 − 3.

NOISE PROTECTION DEVICE DEVELOPMENT FOR LOCAL NOISE CANCELLATION

Currently the noise factors influence on stationary workplaces is prevalent in the other harmful factors influence total share. The information proposed below reveal the gist of the technical solution related to devices for ensuring the workplace acoustic safety. Noise clipping is provided by digital technology. The technical result is expressed in increasing the noise cancellation efficiency in the device upper local zone, so at the user's head level. The device can be used on stationary workplaces, the technological process implementation on which does not require active physical movements. Product using reduces the load on the human auditory system and ensures its protection. Basic expressions are presented that allow noise control in a noisy space between loudspeakers. The noise protection device contains detecting microphones, a control unit for the active noise cancellation process, loudspeakers and a noise shield located on the frame. A specially designed shield is made in the spherical segment form, to the outer edge of which a rim on flexible brackets is attached with the possibility of detecting microphones free movement along it.The device bearing frame is made in a U-shaped form, in the upper part of which the loudspeakers are mounted with diaphragms facing each other.

Povlačenje i poništenje udela u društvu s ograničenom odgovornošću

Withdrawal and cancellation of business shares is a statute that exists in legislation regulating limited liability companies. The goal of the statute is the withdrawal of membership, or the termination of business shares. The removal of an unwanted member and barring entry to the LLC is done by withdrawing and cancelling shares. The law provides only the basis and possibilities for regulation, but specific cases and the withdrawal and cancellation process need to be defined by the memorandum of association, making them the question of autonomous regulation. The decision of the general meeting of the LLC is required. Automatic withdrawal and cancellation of shares on the basis of the memorandum of association is not allowed. There are two types of withdrawals and cancellations: compulsory, withdrawal and cancellation without the member's consent and withdrawal and cancellation with the member's consent. Withdrawal and cancellation of the share entails carrying out the procedure of lowering the base capital of the limited liability company.

A Solar Eruption with Relatively Strong Geoeffectiveness Originating from Active Region Peripheral Diffusive Polarities

Abstract We report the observations of a moderate but relatively intense geoeffective solar eruption on 2015 November 4 from the peripheral diffusive polarities of active region 12443. We use space-borne Solar Dynamics Observatory and ACE observations. EUV images identified a helical pattern along a filament channel, and we regard this channel as flux-rope structure. Flow velocity derived from tracked magnetograms infers converging motion along the polarity inversion line beneath the filament channel. An associated magnetic cancellation process was detected in the converging region. Further, the pre-eruptive EUV brightening was observed in the converging region, the most intense part of which appeared in the magnetic cancellation region. These observations imply that the converging and canceling flux probably contributed to the formation of the helical magnetic fields associated with the flux rope. A filament-height estimation method suggests that the middle part of the filament probably lies at a low altitude and was consistent with the initial place of the eruption. A thick current channel associated with the flux rope is also determined. For an expanding thick current channel, the critical height of the decay index for torus instability lies in the range of 37–47 Mm. Southward magnetic fields in the sheath and the ejecta induced a geomagnetic storm with a D st global minimum of ∼−90 nT.

ANITA-An active vibration cancellation system for scanning probe microscopy.

The high sensitivity of scanning probe microscopes poses a barrier to their use in noisy environments. Vibrational noise, whether from structural or acoustic sources, can manifest as relative motion between the probe tip and sample, which then appears in the probe position ("Z") feedback as it tries to cancel this motion. Here we describe an active cancellation process that nullifies the appearance of this vibration by adding a drive signal into the existing Z-feedback loop. The drive is digitally calculated from accelerometer-based vibration measurements. By transferring the vibration cancellation effort to this drive signal, vibration-created noise is significantly reduced. This inexpensive and easy solution requires no major instrumental modifications and is ideal for those looking to place their microscopes in noisier environments, coupled, for example, to active refrigeration systems (e.g., pulse tube cryocoolers) or other high-vibration instruments.

Fashion subscription retailing: an exploratory study of consumer perceptions

PurposeFashion subscription service is a newly emerged retailing model that provides an innovative way of shopping to meet consumers’ fashion needs. From the perspective of innovation adoption, the purpose of this paper is to provide an insight of consumers’ perceptions as well as adoption intention of this innovative retailing format.Design/methodology/approachThis research is qualitative in nature, utilizing focus group study approach. In this paper, content analysis was applied to analyze the data.FindingsWhile possessing varying degrees of knowledge about fashion subscription retailing, the participants shared the following perceptions of relative advantages, including convenience, personalization, consumer excitement, opportunities to try new styles, and opportunity to better manage their apparel budget. Concerns mainly focused on missing social shopping experiences and the hassle in the cancellation process. The overall adoption intention was high.Research limitations/implicationsDue to the nature of this research, the sample size was limited and results may not be generalized. This research paid less attention to individual differences, in terms of demographic and psychographic characteristics.Practical implicationsFuture marketing could focus more on educating consumers about the attributes of the services they provide. Retailers can strategically leverage the positively perceived advantages in their marketing communications to enhance consumers’ adoption intention of their services.Originality/valueThe paper fills a gap in the literature on consumer behavior toward fashion subscription retailing and sheds light for companies in their endeavors to excel in this new retailing venue.

Finite-Length Analysis of Irregular Repetition Slotted ALOHA in the Waterfall Region

A finite-length analysis is introduced for irregular repetition slotted ALOHA (IRSA) that enables to accurately estimate its performance in the moderate-to-high packet loss probability regime, i.e., in the so-called waterfall region. The analysis is tailored to the collision channel model, which enables mapping the description of the successive interference cancellation process onto the iterative erasure decoding of low-density parity-check codes. The analysis provides accurate estimates of the packet loss probability of IRSA in the waterfall region as demonstrated by Monte Carlo simulations.

Cancellation of Tollmien–Schlichting Waves in Direct Vicinity of a Plasma Actuator

The active cancellation of Tollmien–Schlichting waves is a promising and energy-efficient laminar flow control technology with the goal of drag reduction by delaying laminar–turbulent transition. This paper analyzes, for the first time, the control mechanism in the direct vicinity of the actuator using particle image velocimetry. Artificial Tollmien–Schlichting waves are generated at a frequency of in a two-dimensional zero-pressure-gradient flat-plate boundary layer (). The Tollmien–Schlichting waves travel downstream and are attenuated with an unsteady dielectric-barrier-discharge plasma actuator force. Phase-locked particle image velocimetry measurements at an acquisition rate of in double-frame mode are conducted in the direct vicinity of the plasma actuator, resolving 16 phase angles of the wave cycle. The use of two cameras allows measurement of two full wavelengths of the Tollmien–Schlichting waves and a detailed analysis of the cancellation process. The phase-averaged velocity fields of the artificially generated Tollmien–Schlichting waves are validated with a linear stability theory. The wavelength, amplification, and shape of the Tollmien–Schlichting wave disturbances and the counterwaves generated by the plasma actuator are analyzed.

Two microphone acoustic feedback cancellation in digital hearing aids: A step size controlled frequency domain approach

The feedback cancellation performance of behind the ear hearing aids can be improved by employing two microphones in the feedback cancellation process. A frequency domain implementation of feedback cancellation in a two microphone behind the ear hearing aid has been proposed in this paper. A frequency domain step size control scheme has been further introduced to improve the convergence behaviour. The implementation of a the frequency domain step size control method requires the microphone input signal as well as the loudspeaker output signal to be uncorrelated. In order to reduce the correlation effects and enable such an implementation, we have incorporated frequency shifting in the forward path. The proposed approach has been shown to provide improved convergence behaviour as well as offer enhanced speech quality. Further, the proposed scheme is expected to offer a reduced computational load for longer feedback paths.

Using Comics to Communicate Legal Contract Cancellation

<p class="p1">This article investigates how comics can be used to adequately communicate the correct process of contract cancellation and whether comics can enhance understanding of the legal process. A survey of pre-owned vehicle buyers of various levels of education in Pretoria, South Africa found that when comics are used to communicate contract cancellation, a significant increase in the comprehension of the legal cancellation process occurs. The results may influence how contracting parties may choose to communicate complex legal issues in future, specifically to consumers with little formal education or when parties are confronted with severe language barriers, which is highly relevant in a country such as South Africa with eleven official languages and generally low levels of education. The article argues that representatives tasked with explaining contractual content to contracting parties should consider making use of comics to aid them in their communication process to ensure proper understanding and execution of terms and conditions, which in turn may lead to fewer disputes and avoid expensive litigation.

Relay selection in two-way full-duplex relay networks over Nakagami-m fading channels

We analyze the outage performance of relay selection in two-way full-duplex amplify-and-forward cooperative systems in the presence of residual loop-interference (LI) over Nakagami-m fading channels. In the proposed system, a relay node is selected according to max-min policy and the physical-layer-network-coding technique is applied for two-way transmission. By using end-to-end signal-to-interference-plus-noise-ratio, a new exact outage probability expression is derived in a single-integral form. The numerical and Monte-Carlo simulation results verify the analysis. Moreover, lower-bound and asymptotic expressions for the outage probability are obtained in closed-form. The numerical results reveal that the max-min selection policy provides a significant performance improvement for two-way full-duplex relaying. We observe that the outage performance can be enhanced as long as either the number of relay nodes, the transmit power, or the efficiency of the LI cancellation process increases.

A new high-speed low-power and low-offset dynamic comparator with a current-mode offset compensation technique

In this paper a new low-power high-speed offset-compensated dynamic latched comparator is presented. The proposed comparator uses a two-stage charge-steering preamplifier to achieve high pre-amplification voltage gain. Higher input voltage range of the latch stage significantly reduces the delay time of the latch and relaxes the need for high current in the regeneration process which ensures low-power structure. In addition, a new digitally controlled offset cancellation circuit based on the current-steering structure is used to reduce the offset of comparator. Offset voltage reduction in the startup time is the key advantage of the proposed calibration technique which does not require refreshing the offset cancellation process. Post-layout simulation results in 0.18µm standard TSMC CMOS process show that the designed comparator dissipates 135µW of power consumption from a 1.2V supply voltage and has the 1mV accuracy while operating at 1GHz clock frequency. The power and delay time of the proposed comparator are less than about 10% of the new state-of-the-art comparator. Furthermore, from the Monte-Carlo analysis, the standard deviation of the input referred offset voltage in typical process corner and temperature is obtained about 17.53/1.09mV before and after offset cancellation, respectively.

Reducing the Phase-Noise In ΔΣ Fractional-N Synthezis – A Simulink Model

Abstract The resolution in fractional-N synthesis results as a fractional part of the reference frequency. This category of synthesizers permits a greater fref and a smaller N, a larger loop bandwidth, faster lock times and reduced output phase-noise. In ΔΣ fractional-N PLL’s the main problem is the specific quantization noise. To reduce them many techniques are used. The paper presents a Simulink model of the influence of the requantisation in the phase-noise cancellation process.

Iterative detection for frequency-asynchronous distributed Alamouti-coded (FADAC) OFDM

We propose a near intercarrier interference (ICI)-free and very low complexity iterative detector for frequency-asynchronous distributed Alamouti-coded (FADAC) orthogonal frequency division multiplexing (OFDM). In the previous cancelation schemes, the entire subcarrier signals from one transmit (TX) antenna are estimated and canceled in the received signal from the other TX antenna and vice versa. However, the reliability of the estimated symbols are revealed to significantly vary across the subcarriers and thus, the poorly estimated symbols lead to the incorrect cancelation. Motivated from this, we first propose a scheme which does not cancel the interfering subcarrier(s) at the half band edges which undergo very high interference in FADAC-OFDM. For further improvement, we propose a so-called selective scheme which instantly measures the reliability of the detected symbols at each iteration and then exclude the unreliable symbols in the estimated interference generation.Moreover, the proposed scheme has a drastically reduced complexity by converting the cancelation process from the subcarrier domain to the time domain. In accordance with the analysis on the considered reliability measures, the numerical results show that the proposed scheme achieves the near ICI-free level only within three or four iterations for wide ranges of SNR, frequency offset, and delay spread.

RF power fading mitigation for an IMDD multicarrier LR-PON.

In an intensity-modulation direct-detection (IMDD) orthogonal frequency division multiplexing (OFDM) signal format, radio frequency (RF) power fading produces non-uniform receiving performance among the subcarriers due to chromatic dispersion. Hence each subscriber experiences distinct quality of service (QoS) in conventional frequency division multiple access (FDMA). In this paper, a multicarrier code division multiple access (MC-CDMA) signal along with multicode interference (MCI) cancellation process is proposed and experimentally demonstrated to enhance the receiving performance in an IMDD long reach passive optical network (LR-PON). With the proposed scheme, the receiving performance of each subcarrier can be equalized so that a universal transmitter design at central office (CO) can support all the subscribers with their locations ranging from back-to-back to 100 km. Our experimental results also reveal that, even under 20 dB RF power fading, the proposed scheme can still provide over 21.7 dB power budget and only approximately 2 dB sensitivity deviation is observed in an IMDD LR-PON system.

Neural and behavioral correlates of selective stopping: Evidence for a different strategy adoption

The present study examined the neural and behavioral correlates of selective stopping, a form of inhibition that has scarcely been investigated. The selectivity of the inhibitory process is needed when individuals have to deal with an environment filled with multiple stimuli, some of which require inhibition and some of which do not. The stimulus-selective stop-signal task has been used to explore this issue assuming that all participants interrupt their ongoing responses selectively to stop but not to ignore signals. However, recent behavioral evidence suggests that some individuals do not carry out the task as experimenters expect, since they seemed to interrupt their response non-selectively to both signals. In the present study, we detected and controlled the cognitive strategy adopted by participants (n=57) when they performed a stimulus-selective stop-signal task before comparing brain activation between conditions. In order to determine both the onset and the end of the response cancellation process underlying each strategy and to fully take advantage of the precise temporal resolution of event-related potentials, we used a mass univariate approach. Source localization techniques were also employed to estimate the neural underpinnings of the effects observed at the scalp level. Our results from scalp and source level analysis support the behavioral-based strategy classification. Specific effects were observed depending on the strategy adopted by participants. Thus, when contrasting successful stop versus ignore conditions, increased activation was only evident for subjects who were classified as using a strategy whereby the response interruption process was selective to stop trials. This increased activity was observed during the P3 time window in several left-lateralized brain regions, including middle and inferior frontal gyri, as well as parietal and insular cortices. By contrast, in those participants who used a strategy characterized by stopping non-selectively, no activation differences between successful stop and ignore conditions were observed at the estimated time at which response interruption process occurs. Overall, results from the current study highlight the importance of controlling for the different strategies adopted by participants to perform selective stopping tasks before analyzing brain activation patterns.

Interference cancellation technique for faster‐than‐Nyquist signalling

The faster-than-Nyquist (FTN) signalling is a bandwidth-efficient technology which has drawn attention in the bandwidth-starved world. However, inter-symbol interference is introduced by transmitting signals at a higher signalling rate than allowed by the Nyquist criterion. Decision feedback equalisation (DFE) cancellation is an efficient signal detection scheme for FTN-based communication system. However, since the DFE interference cancellation is executed by overall matrix computation, the required memory size is very large. In order to reduce the complexity of the interference cancellation process, a novel simple interference cancellation is proposed. Simulation results show that the scheme can perform better than DFE, and its complexity is very low because of the absence of QR decomposition.

A Review on Successive Interference Cancellation-Based Optical PPM-CDMA Signaling

AbstractThis paper presents a comprehensive review of successive interference cancellation (SIC) scheme using pulse position modulation (PPM) for optical code division multiple access (OCDMA) systems. SIC scheme focuses on high-intensity signal, which will be selected after all users were detected, and then it will be subtracted from the overall received signal, hence, generating a new received signal. This process continues till all users eliminated one by one have been detected. It is shown that the random location of the sequences due to PPM encoding can reduce the probability of concentrated buildup of the pulse overlap in any one-slot time, and support SIC to easily remove the effect of the strongest signal at each stage of the cancellation process. The system bit error rate (BER) performance with modified quadratic congruence (MQC) codes used as signature sequence has been investigated. A detailed theoretical analysis of proposed system taking into account the impact of imperfect interference cancellation, the loss produced from the splitting during encoding and decoding, the channel loss and multiple access interference is presented. Results show that under average effective power constraint optical CDMA system using SIC scheme with

Multipath ghost elimination for through‐wall radar imaging

In through-wall radar imaging, the multipath echoes caused by specular reflections at interior walls of an enclosed room will lead to multipath ghosts in the resulting image. The ghosts appear like the true targets and therefore tend to increase the number of false alarms. To solve this problem, a new ghost elimination method that removes multipath echoes from the raw radar data is proposed in this study. With a priori knowledge of the room, a concise multipath model is first developed, based on which the locations of the multipath echoes can be determined. Then, a cancellation process that consists of two steps is performed wherein the multipath echoes are cancelled in a specific order depending on the positions of the targets they correspond to. The major advantage of this method is that it can preserve the true targets while eliminating the ghosts even if the targets overlap with those ghosts. The effectiveness of the proposed method is validated by the processed imaging results using both the finite-difference time-domain-simulated data and the real experimental data.