Carrier Interference Research Articles

Utilizing orthogonal frequency division multiple access technology to mitigate carrier and symbol interference in wireless communication networks

Utilizing orthogonal frequency division multiple access technology to mitigate carrier and symbol interference in wireless communication networks

Emergent normal fluid in the superconducting ground state of overdoped cuprates

The microscopic mechanism for the disappearance of superconductivity in overdoped cuprates is still under heated debate. Here we use scanning tunneling spectroscopy to investigate the evolution of quasiparticle interference phenomenon in Bi2Sr2CuO6+δ over a wide range of hole densities. We find that when the system enters the overdoped regime, a peculiar quasiparticle interference wavevector with arc-like pattern starts to emerge even at zero bias, and its intensity grows with increasing doping level. Its energy dispersion is incompatible with the octet model for d-wave superconductivity, but is highly consistent with the scattering interference of gapless normal carriers. The gapless quasiparticles are mainly located near the antinodes and are independent of temperature, consistent with the disorder scattering mechanism. We propose that a branch of normal fluid emerges from the pair-breaking scattering between flat antinodal bands in the quantum ground state, which is the primary cause for the reduction of superfluid density and suppression of superconductivity in overdoped cuprates.

Simultaneous Separation of Protactinium-230 and Uranium-230 Isotopes from a Proton-Irradiated Thorium Matrix.

The use of radioisotopes in cancer therapy is becoming increasingly important. As a potential candidate for targeted alpha therapy, 230U (t1/2 = 20.8 d), the decay daughter of 230Pa (t1/2 = 17.4 d) is currently being investigated for cancer treatment. For radioisotopes to be used in biomedicine, they must be radiochemically pure and free from carrier interference. This can be challenging given their short half-life. Thus, radiological separation methods for harvesting isotopes for use in biomedicine must be simple, fast, and capable of obtaining the required purity levels. Herein, we demonstrate a new rapid method for the separation of 230U and 230Pa from a proton-irradiated 232Th metal target and from coproduced fission products with high recovery and purity. A dual-column approach was used, in which the first column was an anion exchange (AX) column and the second column was a DGA column. The MP-1 AX resin was used for the primary separation of the three major components (U, Pa, and Th, as well as fission products), and the DGA column was used for further purification of the separated 230U. The method is simple and allows for straightforward separation of U, Pa, Th, and fission products; also, the entire process from target dissolution to shipment of 230U could be completed in 3 days with an overall 230U recovery yield of 96 ± 3%. Additionally, separated 230Pa fractions can be used to harvest ingrown 230U after initial separation.

MagSonic: Hybrid Magnetic-Ultrasonic Wireless Interrogation of Millimeter-Scale Biomedical Implants With Magnetoelectric Transducer.

Wireless interrogation (power and data transfer) of biomedical implants, miniaturized to millimeter (mm) dimensions, is critical for their chronic operation. Achieving simultaneous wireless power and data transfer at deep sites reliably within safety limits for closed-loop sensing/actuation functions of mm-sized implants is challenging. To enable this operation, a hybrid magnetic-ultrasonic interrogation approach (called MagSonic) is realized through a single magnetoelectric (ME) transducer at the implant that can generate and receive both magnetic field and ultrasound. The fabricated mm-sized bar-shaped ME transducer (5.2×2×1.6 mm3) operates at acoustic wave resonance, functioning at sub-MHz frequencies. For the first time, we demonstrate wireless power reception through one modality (magnetic field or ultrasound) and simultaneous uplink data transmission using the other. At 40 mm depth, the MagSonic link could achieve 100 kbps uplink data rate (bit error rate ≤ 10-5) using 190 pJ/bit transmitted energy and 8 mW delivered power in tissue. The robustness of the MagSonic interrogation link against power carrier interference and misalignments is also demonstrated.

A Novel Machine Learning Approach for Blind Carrier Offset Estimation in OFDM Systems

As wireless networks continue to evolve with the emergence of sixth-generation networks and beyond, OFDM technology is expected to be an essential system component for providing reliable connectivity in an increasingly complex environment. Its high spectrum efficiency, efficiency against impulse noise, and resilience against frequency-selective multipath fading channels make it an invaluable component. Although OFDM technology has various capabilities and uses and is widely used, it has some issues and challenges, and one of these challenges is Carrier Frequency Offset (CFO). The CFO destroys orthogonality between subcarriers and causes subcarrier misalignment at the receiver, resulting in Inter- Carrier Interference (ICI) in OFDM systems. This interference impairs system performance by introducing errors and degrading signal-to-noise ratios (SNR). In this paper, a novel approach to estimate the CFO in OFDM systems via Feedforward Neural Network (FNN) has been proposed. The architecture is precisely designed for regression tasks, with a focus on accurately estimating the continuous parameter φ based on the input features. The multiple hidden layers facilitate the extraction of intricate patterns, while careful training options ensure efficient optimization and monitoring of the training process. The performance of the proposed FNN algorithm is assessed and compared with other subspace-based methods, ESPRIT, PM(MUSIC), and QR. Remarkably, the results demonstrate that the FNN algorithm consistently outperforms all subspace methods, especially in low SNR scenarios.

Photo-Cleavable Polycations-Wrapped Upconversion Nanoparticles for Efficient siRNA Delivery and Cancer Therapy

RNA interference (RNAi) therapy is a promising approach for cancer therapy. However, due to the weak binding affinity between a carrier and small interference RNA (siRNA) and complicated tumor environment, efficient loading and release of siRNA still remain challenging. Here, we design photo-cleavable polycations-wrapped upconversion nanoparticles (PC-UCNPs) for spatially and temporally controllable siRNA delivery. The PC-UCNPs are synthesized by in situ reversible addition−fragmentation chain transfer (RAFT) polymerization of photo-cleaved 5-(2-(dimethylamino)ethoxy)-2-nitrobenzyl acrylat (MENA) monomer and poly(oligo(ethylene oxide) methyl ether acrylate (OEMA) mononer through a chain transfer agent that anchored on the surface of silica-coated upconversion nanoparticles (UCNPs@SiO2). After reacting with CH3I, siRNA and hyaluronic acid (HA) are adsorbed on the particle surface to prepare PC-UCNPs/siRNA/HA. The reaction with cell-secreted hyaluronidase (HAase) achieves the intracellular delivery of PC-UCNPs/siRNA/HA, and 980 nm laser irradiation causes siRNA release, which effectively improves the gene silencing efficiency in vitro and suppresses tumor growth in vivo; therefore, these processes have a promising potential application in precision medicine.

Effect of block size on BER performance of inverse filtering based MIMO FBMC

Filter bank multicarrier (FBMC) is a novel next-generation data transfer technique. FBMC has a large number of benefits over conventional orthogonal frequency division multiplexing (OFDM) techniques. The FBMC scheme suffers from imaginary interference, which degrades the bit error rate (BER) performance at the receiver. In the recent past, inter carrier interference (ICI)-free Alamouti-coded FBMC frame and block repetition schemes for BER improvement were discussed. However, in the analysis, various interfering terms are neglected. In this work to reduce ICI and inter symbol interference (ISI), the concept of inverse filtering is applied while considering other interfering terms. Inverse filtering can be used to reduce the negative impacts of the ICI and ISI. This is determined by mathematical modelling that includes the ICI, ISI, and other interfering parameters. The simulation is performed in MATLABR software. The obtained BER at an SNR of 15 dB is 2.3 × 10−4.The simulation results are also compared with some of the recent methods, and it has been found that the proposed scheme is better in comparison to the considered recent methods.

Plasmon enabled Claisen rearrangement with sunlight.

Plasmonic-heat generated from the solar irradiation of gold nanoparticles is used as the thermal energy source for the Claisen rearrangement of allyl phenyl ether to 2-allylphenol, which is conventionally performed with electrical heating at 250 °C. The use of a closed reactor enables the physical separation of the reactants from the source of plasmonic-heat, thereby preventing the interference of the hot-charge carriers in the plasmon-driven Claisen rearrangement. In this way, the sole effect of plasmonic-heat in driving a high temperature organic transformation is demonstrated. Our study reveals the prospects of plasmonic nanostructures in conducting energy intensive chemical synthesis in a sustainable fashion.

Selective Mapping Scheme for Universal Filtered Multicarrier

The next step in mobile communication technology, known as 5G, is set to go live in a number of countries in the near future. New wireless applications have high data rates and mobility requirements, which have posed a challenge to mobile communication technology researchers and designers. 5G systems could benefit from the Universal Filtered Multicarrier (UFMC). UFMC is an alternate waveform to orthogonal frequency-division multiplexing (OFDM), in filtering process is performed for a sub-band of subcarriers rather than the entire band of subcarriers Inter Carrier Interference (ICI) between neighbouring users is reduced via the sub-band filtering process, which reduces out-of-band emissions. However, the UFMC system has a high Peak-to-Average Power Ratio (PAPR), which limits its capabilities. Metaheuristic optimization based Selective mapping (SLM) is used in this paper to optimise the UFMC-PAPR. Based on the cognitive behaviour of crows, the research study suggests an innovative metaheuristic optimization known as Crow Search Algorithm (CSA) for SLM optimization. Compared to the standard UFMC, SLM-UFMC system, and SLM-UFMC with conventional metaheuristic optimization techniques, the suggested technique significantly reduces PAPR. For the UFMC system, the suggested approach has a very low Bit Error Rate (BER).

Compensation of Optical Pump Magnetometer Using the Improved Mayfly Optimization Algorithm

In order to solve the problem that the cesium optical pump magnetometer is disturbed by the carrier’s interference magnetic field during magnetic field anomaly detection, an interference magnetic field compensation method based on an improved mayfly optimization algorithm (IMOA) was proposed in this paper. First, by combining the measurement results of the attitude sensor with the geomagnetic inclination and magnetic declination in the locality, the measurement results of the optical pump magnetometer can be decomposed into the component values under the three axes of the carrier coordinate system. A compensation model including the carrier interference magnetic field was established. Then, considering the poor global search performance that existed in the mayfly optimization algorithm (MOA), an elite chaotic reverse learning strategy and Levy mutation strategy were introduced to improve the MOA. The compensation performance of the IMOA was estimated with a series of field experiments and compared with the stretching particle swarm optimization algorithm. The experiment results indicated that these two methods can effectively compensate the magnetometer’s measurement values, and that the IMOA method more easily jumps out of the local optimum, and has higher compensation accuracy.

OFDM and MIMO wireless communication performance measurement using enhanced selective mapping based partial transmit sequences

The great spectral efficiency to mitigate multipath fading of OFDM (orthogonal frequency division multiplexing) made more accepted for broadband communication systems with some drawbacks such as high PAPR (Peak-to-Average Power Ratio), ISI (Inter-Symbol Interference) and ICI (Interiv Carrier Interference). High PAPR forces the operations of the HPA amplifier to work beyond its linear region causing in-band distortion as well as out-band noise and are overcome by using an amplifier with a large dynamic range. In this method, OFDM symbols are partitioned into multiple disjoint sub-blocks which are independently rotated in phase by optimum phase weighting factors. The resultant OFDM signal has less PAPR when compared to that of original OFDM signal in wireless communication. To minimize computational complexity, a modified PTS technique is proposed to enhance PAPR reduction and power amplifier efficiency in OFDM and MIMO (multiple inputs, multiple outputs)-OFDM methods through Selective Mapping based PTS (SMPTS) method combined with PAPR reduction methods.

Impact of Subcarrier Allocation and User Mobility on the Uplink Performance of Multiuser Massive MIMO-OFDM Systems

This paper considers the uplink performance of a multi-user massive multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system with mobile users. Mobility brings two major problems to a MIMO-OFDM system: inter carrier interference (ICI) and channel aging. In practice, it is common to allot multiple contiguous subcarriers to a user as well as schedule multiple users on each subcarrier. Motivated by this, we consider a general subcarrier allocation scheme and derive expressions for the ICI power, uplink signal to interference plus noise ratio and the achievable uplink sum-rate, taking into account the ICI and the multi-user interference due to channel aging. We show that the system incurs a near-constant ICI power that depends linearly on the ratio of the number of users per subcarrier to the number of subcarriers per user, nearly independently of how the UEs distribute their power across the subcarriers. Further, we exploit the coherence bandwidth of the channel to reduce the length of the pilot sequences required for uplink channel estimation. We consider both zero-forcing and maximal-ratio combining at the receiver and compare the respective sum-rate performances. In either case, the proposed subcarrier allocation scheme leads to significantly higher sum-rates compared to previous work, owing to the near-constant ICI property as well as the reduced pilot overhead.

Precoded SLM and PTS Scheme for Reduced PAPR in OFDM for Wireless Communications

Orthogonal Frequency Division Multiplexing (OFDM) contribute high data rates in current as well as future wireless communication systems but it aches from high Peak to Average Power Ratio (PAPR). But this high PAPR makes the High-Power Amplifier (HPA) complex which increases the cost of it and leads to the drawbacks like Inter Carrier Interference (ICI) and rise in out of band radiation. Even though many techniques are there to decrease the complexity of HPA by reducing the PAPR, Selected Mapping (SLM) and the Partial Transmit Sequence (PTS) provides less PAPR with low complexity. In this paper, both PTS and SLM are combined with Discrete Sine Transform (DST) and their PAPR and efficiencies are also compared with OFDM signal. The proposed hybrid DST-PTS and DST-SLM provides less PAPR compared to OFDM, SLM and PTS techniques with low complexity. Also, the bit error rate for DST-SLM and DST-PTS techniques are compared for different values of SNR. In future wireless communication systems, these proposed techniques can be used as they provide less bit error rate and less PAPR with low complexity

Performance analysis of massive multiple input multiple output for high speed railway

This paper analytically reviews the performance of massive multiple input multiple output (MIMO) system for communication in highly mobility scenarios like high speed Railways. As popularity of high speed train increasing day by day, high data rate wireless communication system for high speed train is extremely required. 5G wireless communication systems must be designed to meet the requirement of high speed broadband services at speed of around 500 km/h, which is the expected speed achievable by HSR systems, at a data rate of 180 Mbps or higher. Significant challenges of high mobility communications are fast time-varying fading, channel estimation errors, doppler diversity, carrier frequency offset, inter carrier interference, high penetration loss and fast and frequent handovers. Therefore, crucial requirement to design high mobility communication channel models or systems prevails. Recently, massive MIMO techniques have been proposed to significantly improve the performance of wireless networks for upcoming 5G technology. Massive MIMO provide high throughput and high energy efficiency in wireless communication channel. In this paper, key findings, challenges and requirements to provide high speed wireless communication onboard the high speed train is pointed out after thorough literature review. In last, future research scope to bridge the research gap by designing efficient channel model by using massive MIMO and other optimization method is mentioned.

An ASK Data Demodulator Circuit for Implantable Medical Devices Supporting a Minimum Modulation Depth of 0.034.

Amplitude shift keying (ASK) data demodulation method has been widely used for simultaneous wireless data and power transfer in implantable medical devices (IMDs). Small amplitude modulation depth (MD) is usually preferred as it helps promote energy harvesting efficiency. This paper presents an ASK data demodulator that has good immunity to disturbances and can demodulate ultra-low MD ASK signal. A three-stage amplifying structure (3SAS) is proposed, in which the common-mode level of each amplifier is set between the high and low levels of its input signal envelope to prevent amplifier gain saturation and maximize the amplification of the envelope difference. Two envelope detectors (EDs) are used before and after the 3SAS respectively. The first one is to obtain a coarse envelope for 3SAS input and the second one is to further suppress the residual carrier interference and get a fine envelope. The proposed demodulator is implemented in 0.18-μm high-voltage Bipolar-CMOS-DMOS (BCD) technology. The detectable MD is measured as low as 0.034%, showing that the proposed demodulator can work smoothly and robustly in some extreme cases of simultaneous data and power transferring.Clinical Relevance- The ASK data demodulator proposed in this paper supports ultra-low modulation depth. This reduces the bit error rate of the data link and keeps a highly power conversion efficiency for wireless power and data transfer in implantable medical devices.

Research on aeromagnetic three-component error compensation technology for multi-rotor UAV

Aeromagnetic three-component data contain a large amount of geomagnetic information, which can help to obtain a quantitative interpretation of a magnetic anomaly and to improve the identification accuracy of an abnormal body. However, aeromagnetic three-component data of an unmanned aerial vehicle (UAV) include the carrier fixed interference error, inductive interference error, eddy current interference error, and attitude error. Therefore, carrier interference compensation and attitude compensation are necessary to obtain three-component data in a geographical coordinate system. This paper analyzes the difference of six types of attitude conversion matrices for the mutual conversion between the geographic and carrier coordinate systems. Based on the analysis results, the yaw-pitch-roll sequence has the smallest error when calculating the attitude conversion, so the compensation sequence of the roll-pitch-yaw is selected for attitude compensation. The characteristics of the UAV carrier interference error are also analyzed. A low-pass filter is set up for data preprocessing according to the high-frequency characteristics of the carrier eddy current interference, and carrier fixed interference and induction interference compensation models are constructed based on the Tolles-Lawson model. The aeromagnetic three-component comprehensive compensation error objective function is established by integrating attitude compensation and carrier interference compensation. In addition, an adaptive step-size cuckoo algorithm is proposed to obtain the minimum value of the objective function to solve 12 compensation parameters so that the accurate three-component data can be obtained quickly, efficiently, and accurately. Finally, a comprehensive compensation experiment is performed on the three-component aeromagnetic data, and the mean error of the three-component data after compensation is reduced to less than 0.72 nT.

Flexible and fast multi‐level modulation format identification using optical orthogonal frequency division multiplexing redundancy subcarriers

AbstractCompared with the orthogonal frequency division multiplexing (OFDM) communication system, the subcarrier‐index modulation OFDM communication system can alleviate the problem of peak‐to‐average power ratio and the frequency offset sensitivity. Therefore, the problem of inter carrier interference (ICI) and low power of the radio frequency amplifier in OFDM communication system can be solved to some extent. A fast and flexible modulation format recognition (MFR) scheme utilizing OFDM redundancy subcarriers is proposed in order to solve the MFR problem in coherent optical OFDM transmission. The scheme uses the silent subcarrier position of OFDM to carry modulation format information (MFI) and the receiving end decodes the MFI index by comparing the modulus values of the redundant symbols. It can recognize the phase shift keying (PSK) and multiple quadrature amplitude modulation (M‐QAM) modulation formats block by block. The number of symbols required by the proposed MFR is equal to the number of OFDM subcarriers, and the average time to get the recognition result in a block is O(1). We numerically investigate the proposed MFR among 20 Gbaud 4/16/32/64 QAM and 8/16 PSK. The results show that the correct recognition rate of the proposed scheme is not affected by the modulation formats. In particular, the proposed MFR is a potential solution for future flexible optical networks.

A Performance Analysis of Wavelet based LTE-OFDM with Multi-equalizers

A rapid change in usage of mobile data and mobile based applications such as online gaming, mobile TV etc. motivates the mobile wireless communication system to work on new emerging trends Long Term Evolution (LTE). LTE-4G architecture provides an optimized packet based radio access technology. The basic signal format of LTE is Orthogonal Frequency Division Multiplexing (OFDM) Modulation. This modulation scheme satisfies the spectrum flexibility requirement in LTE. LTE-MIMO-OFDM with IFFT and FFT transform introduced to provide the cost-effective solution for very wide carriers with high PAPR. Inter-symbol Interference (ISI) and inter carrier interference (ICI) are predominant factors which exist in the wireless communication channel. Existing methods of ISI and ICI reduction to improve signal quality have been achieved using conventional OFDM techniques. However, a better modulation scheme is required to achieve high data rate, low latency and flexible bandwidth deployment. This paper has proposed a Wavelet based LTE-MIMO-OFDM modulation scheme with multi equalizer that improves the performance of system by reducing PAPR and BER in MCM. Experimental results show the performance of this scheme and the results is compared with existing MMSE and Multi equalizer MMSE and achieves a flexible spectral efficiency with reduction of PAPR and BER.

A modified convolutional neural network-based signal demodulation method for direct detection OFDM/OQAM-PON

Orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) is a promising modulation candidate for passive optical network (PON) due to its high flexibility, better time–frequency focusing characteristic, great resistance to the inter symbol and inter carrier interferences and higher spectrum efficiency compared to OFDM. However, the intrinsic imaginary interference together with linear and nonlinear distortions make it more difficult to recover the transmitted OFDM/OQAM signal at the receiver side. To mitigate the transmission impairments, a modified convolutional neural network (CNN) is utilized to learn the channel state information and the constellation demapping mechanism for OFDM/OQAM-PON. The distorted received signals are equalized implicitly to obtain the transmitted binary bits directly. The simulation results show that the CNN based receiver (Rx) can compensate the linear and nonlinear distortions more effectively compared to traditional pilot-based Rx, especially for the high order modulation long-reach PON.

Performance Enhancement of Gaussian Minimum Shift Keying Using Optimum Phase Sampling Technique for Turbulent Free-Space Optical Communication

In this paper, analytical performances of Gaussian minimum shift keying (GMSK) are studied for free space optical communication system. Authors propose an innovative sampling technique called, optimum phase sampling technique to investigate the bit error performance of GMSK modulation. Subsequently, performances of GMSK like, bit error rate (BER), power spectral density, and adjacent carrier interference (ACI) have also been investigated and compared with other modulation techniques. Furthermore, return to zero (RZ) coding input bit stream prior to GMSK technique improves the ACI performance of GMSK. To end with, we present the improvement of degradation parameter (γ) in a tabular form through phase sampling technique. Moreover, both optimum phase sampling and narrow pulse shaping of RZ-GMSK obtains near optimal result of BER. The numerical results show, that the proposed phase sampled RZ-GMSK of 70% duty cycle at BT = 0.6 has a degradation value of 0.979, which is comparable to GMSK at BT = ∞. Moreover, the proposed RZ-GMSK achieves lower ACI value and has an error rate of 7 × 10−7, which is lower than the GMSK of 1 × 10−6 BER value.