Cancellation Stage Research Articles

A switched full duplex MIMO architecture with digital linear and nonlinear cancellation

Enabling full duplex (FD) in MIMO systems is challenging due to increased hardware complexity and increased training overhead required for canceling not only self-interference (SI) but also cross-link-interference (CLI) signals, considering both linear and nonlinear effects on each stream. In this paper, we propose switched FD MIMO (FD-SW-MIMO) architecture as a low-complexity, low-overhead solution, which enables stream-based nonlinear estimation to be performed independently from channel estimation, so that those nonlinear reference signals are fed to linear SI and CLI cancellation stages. For improved performance at high transmit power levels, the Random Fourier Features - Least Mean Squares (RFF-LMS) algorithm is employed on the residual SI and CLI signals per stream. Our experiments conducted on a software-defined radio based 2x2 FD MIMO test setup reveal that the proposed FD-SW-MIMO architecture can provide up to 12 dB enhancement over linear only digital cancellation. The proposed architecture requires only minor hardware modification(s), avoiding active analog cancellation circuitry and extra Tx/Rx chains. Requiring the same training overhead as linear only cancellation, FD-SW-MIMO architecture can quadruple the rate of HD SISO for low to moderate transmit power levels, and for high transmit power levels, the HD SISO rate is tripled due to slightly increased overhead.

Improving Isolation in Monostatic Simultaneous Transmit and Receive Systems Using a Quasi-Symmetrical Self-Interference Cancellation Architecture

For simultaneous transmit (Tx) and receive (Rx), it is a common practice, with monostatic full duplex (FD) systems, to use a single antenna and a circulator to provide isolation between the transmit and receive radio chains. However, most circulators currently on the market are designed to provide 12 to 20 dB of Tx/Rx port isolation, which is not sufficient for full duplex (FD) microwave communication. In fact, it is necessary to provide at least <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 30 dB of isolation to prevent the receiver desensitization that is caused by the leakage of high-power transmit signals. For this reason, practical simultaneous transmit and receive (STAR) systems require additional cancellation stages. In this paper, we present a novel STAR system that incorporates two circulators, a hybrid coupler, and a self-interference cancellation (SIC) circuit, based on a Finite Impulse Response (FIR) topology. Our design achieves an average Tx/Rx port isolation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 37 dB over a 25 MHz bandwidth ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">viz.</i> 2.395–2.42 GHz) in simulation, with a minimum and maximum cancellations of 35 dB and 41 dB, respectively. A prototype was fabricated and tested showing good agreement with the simulations. All in all, the prototype achieved an average cancellation of 36 dB, with a cancellation range of 33 dB to 42 dB.

Effects of Subsidy Cancellations on Investment Strategies of Local Governments and New Energy Vehicle Manufacturers: A Study Based on Differential Game

The intensity of China’s new energy vehicle (NEV) subsidies has gradually declined since 2017 and is expected to end in the next few years, thereby causing market fluctuations and affecting the investment strategies of both local governments and automotive enterprises. In order to examine the effects of a subsidy cancellation, this study introduced it as an external disturbance to establish a differential game model, in which a random arrival process is used to represent the occurrence of a cancellation. The model incorporated both decentralized and centralized modes at the pre- and post-subsidy cancellation stages. A numerical simulation showed that the investments of both parties, the market demand, and the system benefits in both modes would be lower when compared to the scenario in which the subsidy is not canceled, but continued. The performance of the centralized mode was superior to that of the decentralized one, implying that the centralized mode was capable of realizing Pareto optimality. A sensitivity analysis of the model’s parameters showed that the timing of the subsidy cancellation would not affect the investment levels of either party in either stage, but losses of market demand and system benefits would occur shortly after the cancellation and continue until stabilizing.

On the Use of Reciprocal Filter Against WiFi Packets for Passive Radar

This article derives a novel unified signal processing scheme for WiFi-based passive radar in order to limit its complexity and enhance its suitability for short range civilian applications. To this purpose, the exploitation of a reciprocal filtering (RpF) strategy is investigated as an alternative to conventional matched filtering at the range compression stage. Along with the well-known advantage of a remarkable sidelobes control capability for the resulting range-Doppler response, the use of a RpF is shown to provide additional benefits for the specific sensor subject of this article. Specifically, it allows to streamline the disturbance cancellation stage and to implement a unified signal processing architecture which is capable to handle the different modulation schemes typically adopted in WiFi transmissions. Appropriate adjustments are also proposed to the theoretical RpF in order to cope with the inherent loss in terms of signal-to-noise power ratio. The effectiveness of the proposed signal processing scheme encompassing the RpF strategy is proved against both simulated and experimental datasets.

A Two-Stage Wideband RF Cancellation of Coupled Transmit Signal for Bi-Static Simultaneous Transmit and Receive System

Wireless technology is growing at a fast rate to accommodate the expanding user demands. Currently, the radio frequency (RF) spectrum is overcrowded. Hence, it is more susceptible to signal fratricide and interference. To enhance spectrum access, in-band full duplex systems are implemented to achieve simultaneous transmission and reception (STAR) and double the spectral efficiency. However, STAR systems require suppression of the high power transmit signals that can leak into the receiver chain. This type of self-interference (SI) can significantly reduce the receiver.s dynamic range and often leads to its desensitization. Therefore, successful STAR implementation requires considerable isolation between the transmitter and receiver to reduce the SI signal. To do so, RF self-interference cancellation (RFSIC) stages are considered. In this paper, we present a two-stage SIC system that includes transmit and receive antennas isolation and RFSIC filter stages. Notably, the isolation between the transmit and receive antennas is based on a novel symmetric suppression technique. The RFSIC filter is based on a hybrid finite impulse response (FIR) filter and resonator architecture. Adding a resonator to the FIR filter provides improved matching to approximate and suppress the direct SI coupling. Our design achieves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 52 dB isolation on average across a 500 MHz bandwidth ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">viz.</i> 1-1.5 GHz) in simulation. Simulation results show a minimum cancellation of 41 dB and a maximum cancellation of 65 dB. A prototype was fabricated and tested, showing an average of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 44 dB cancellation which is in good agreement with our simulation.

A Quasi-Balanced Power Amplifier With Feedforward Linearization

In this letter, a feedforward (FFW) linearized power amplifier (FFW PA) composed of quasi-balanced PA (QBPA) and cancellation stages is proposed by suppressing the third-order intermodulation (IM3) tones. The QBPA stage is used for extracting the IM3 tones and the FFW technique is used for suppressing IM3 tones in the cancellation stage. Compared to the conventional FFW amplifier, the proposed FFW PA does not require a phase shifter and attenuator in the QBPA stage and does not need to employ a high-gain auxiliary amplifier in the cancellation stage. The measured output-referred 1-dB gain compression point of the proposed FFW PA is +30.8 dBm at 3.5 GHz, which is 3.8 dB higher than the single PA used in the FFW PA. In two-tone measurement at 7.8-dB back-off output power (+20 dBm/tone), the IMD3 level of the FFW PA is −54.6 dBc, which is lower by 14 dB compared to that of the conventional balanced PA. In the LTE evaluation with a 64 quadrature amplitude modulation signal in 20-MHz bandwidth and +23-dBm transmitting power, the measured output spectra of the proposed FFW PA exhibit an adjacent channel leakage ratio of −48.7 dB, which is a 6.6-dB improvement over the conventional balanced PA.

A Coordinated Direct AF/DF Relay-Aided NOMA Framework for Low Outage

This paper investigates the performance of a new framework for low-outage downlink non-orthogonal multiple access (NOMA) using a coordinated direct and relay transmission (CDRT) scheme with direct links to both the near-user (NU) and the far-user (FU). Both amplify-and-forward and decode-and-forward relays are considered. In this framework, the NU combines the signals from base-station and relay at each stage of the successive interference cancellation (SIC) to attain good outage performance. For both NU and FU, the expressions for outage probability and throughput are derived in closed form. We also derive the high-SNR expressions for the outage probability to demonstrate that with the proposed framework, both users harness a diversity of two without feedback bits (this is the only framework to achieve this). We demonstrate that the choice of power allocation coefficient and target symbol rates is crucial to maximizing the NU throughput while ensuring a desired target FU throughput. We demonstrate that CDRT with the proposed framework outperforms known schemes in terms of outage probability, sum throughput, and energy efficiency. Moreover, we also show that optimal rate selection is important to maximize the energy efficiency. Monte Carlo simulations validate the accuracy of the derived analytical expressions.

Impact of Self-Energy Recycling and Cooperative Jamming on SWIPT-Based FD Relay Networks With Secrecy Constraints

This paper investigates the secrecy performance of a power splitting-based simultaneous wireless information and power transfer cooperative relay network in the presence of an eavesdropper. The relay is considered to operate in full-duplex (FD) mode to perform both energy harvesting and information decoding simultaneously. To accomplish that, the relay is assumed to employ two rechargeable batteries, which switch between power supplying mode and charging mode at each transmission block. We also assume that the self-interference inherent of the FD mode is not completely suppressed. Therefore, it is assumed that, after some stages of passive and active self-interference cancellation, there is still a residual self-interference (RSI). A portion of this RSI (remaining after passive cancellation) is recycled for energy harvesting. In order to improve the system secrecy performance, it is considered that the relay can split its transmit power to send the information signal and to emit a jamming signal to degrade the eavesdropper&#x2019;s channel. The secrecy performance is evaluated in terms of the secrecy outage probability and the optimal secrecy throughput. Tight-approximate and asymptotic expressions are obtained for the secrecy outage probability, and the particle swarm optimization method is employed for addressing the secrecy throughput optimization problem. From numerical results, we show that the secrecy performance can be increased depending on the self-energy recycling channel condition. Finally, our derived expressions are validated via Monte Carlo simulations.

Improving Code Word Interference Cancellation (CWIC) Technique in Heterogeneous Network

This paper first examines performance of (code word interference cancellation) CWIC for downlink non orthogonal multiple access (NOMA) combined with 2-by-4&nbsp; multi-user (MU)-MIMO, taking into account the disadvantages of the CWIC receiver, such as complex receiver structure, high volumes of network overhead and high delay, we offer a way to improve the efficiency of the CWIC receiver. CWIC receiver detects, decodes and cancels all interference signals in several steps, from large to small, respectively. The number of interference cancellation stages depends on the number of interference signals. The proposed receiver only cancels the intense interference signal. That's why it's called CWIC-II (Intense Interference). Finally, using simulation, we show that CWIC-II receiver reduces latency and improves throughput. The complexity problem of the CWIC receiver structure is also resolved. In the end, a method has been developed to resolve the problems of the proposed receiver.

New Image Transmission Schemes for DST-Based MC-CDMA System

In recent years, one important research area for multimedia broadcasting is how to encrypt images over communication systems. However, wireless transmission is usually under many constraints and limitations like multipath fading, InterSymbol Interference and jitter especially for such applications require relatively high data rates compared to voice transmissions. Interleaving techniques with multicarrier code division multiple access system are used to combat multi-path fading environment. This paper proposes three new transmission schemes of encrypted images for downlink discrete sine transform-based multi-carrier code division multiple access (DST-MC-CDMA) system. For each one of them, two or three stages are added to the DST-MC-CDMA system to combat the wireless transmission problems. The three stages are called Randomization stage, Interleaving stage, and PIC stage. The randomization stage encrypts the image using a two dimensional chaotic map before the DST-MC-CDMA modulation. The interleaving stage interleaves the DST-MC-CDMA signal before the transmission. The stage of parallel interference cancellation is used to cancel the multiple access interference from the received image. The main aim is to clarify the received image by combating the wireless channel weaknesses. The results of the experiments reveal that the proposed schemes are superior to conventional one that uses only equalization. Moreover, a significant performance improvement in terms of the mean square error and peak to signal and noise ratio values when applying the proposed schemes is shown in the results.

MIMO In-Band-Full-Duplex PLC: Design, Analysis and First Hardware Realization of the Analog Self-Interference Cancellation Stage

In-band full-duplex (IBFD) is an attractive solution for increasing the throughput of Power Line Communication (PLC) systems. In IBFD, each network node is allowed to transmit and receive simultaneously in the same frequency band. This paper discusses the importance of defining figures of merit to analyze IBFD performance, which is often forgotten by the literature that addresses IBFD from a pure system level and signal processing perspective. This is because in IBFD hardware-related aspects are of great importance. The focus is then given to the first self-interference (SI) cancellation stage, namely the analog coupling and self-interference cancellation stage (ASICS). Two architectures are considered. A detailed analysis is offered by taking into account circuit-level aspects. A broadband multiple conductor PLC scenario is assumed to enable multiple-input multiple-output (MIMO) IBFD communication. The first considered architecture performs SI subtraction exploiting operational amplifiers. The second proposed architecture exploits the characteristics of a three ports magnetic circuit together with a signal generator to remove the SI. Design, analysis, and hardware realization of these circuits have been done to compare and show the practical feasibility of the ASICS for PLC, well known to be challenged by its line impedance matching problems and severe frequency selective channel characteristics. This paper is the first documented contribution of the IBFD ASICS for 2×2 MIMO broadband PLC physically realized and tested in the field.

A low noise current readout architecture with 160 dB transimpedance gain and 1.3 MHz bandwidth

This paper proposes a low-noise readout circuit with a noise floor of 11 fArms/sq(Hz) and a bandwidth of 1.3 MHz. The novel electrostatic discharge (ESD) leakage current cancellation stage allows the circuit to detect sub-pA range current input. A total trans-impedance gain of 160 dB is obtained by a current preamplification stage with a 100 × current gain followed by a transimpedance amplifier (TIA) with a 1 Mohm feedback resistive gain. The reader is designed in a 0.18 μm CMOS process and consumes 5.6 mW from a 1.8 V supply.

DVB-T-Based Passive Forward Scatter Radar: Inherent Limitations and Enabling Solutions

This article investigates the target detection capability of a passive forward scatter radar (PFSR) exploiting a digital video broadcasting - terrestrial (DVB-T) transmitter as illuminator of opportunity. By means of theoretical and simulated analyses, it is shown that conventional processing schemes might suffer from significant performance degradation when exploiting orthogonal frequency division multiplexing (OFDM) waveforms of opportunity compared to other broadcast transmissions (e.g., frequency modulation radio broadcast). Specifically, the direct application of conventional processing approaches to the case of a DVB-T PFSR is demonstrated to yield: 1) a nonnegligible increase of the competing background level and 2) a steeper fading of the target response due to the intrinsic characteristics of the exploited waveforms of opportunity, above all the modulation scheme and the signal spectral characteristics. Therefore, appropriate signal processing techniques are proposed to avoid these effects which jeopardize the target detection capability. The conceived processing scheme exploits the digital nature of the employed waveforms and a subband approach for improving both the interference cancellation stage and the target signature extraction. The benefits of the proposed approach are illustrated by means of theoretical and simulated analyses. The application of the resulting processing scheme against experimental data proves its effectiveness in practical scenarios.

Adaptive Learning Rate Tuning Algorithm for RF Self-Interference Cancellation

Future wireless systems that take advantage of in-band full-duplex (IBFD) technology require that the consequential self-interference (SI) be sufficiently mitigated for successful operation. Many IBFD designs utilize a multitap RF cancellation stage that necessitates the optimal configuration of multiple weights to accurately replicate real-world multipath SI channels. The nonconvex error surfaces generated by these channels present different features that can be challenging to navigate for canceller tuning algorithms. This article introduces a novel adaptive learning rate approach that utilizes a target error and a gradient estimation that is progressively forgotten over time to accelerate convergence speed and maximize cancellation performance. The tuning characteristics of a prototype system using this algorithm to set the weights of a two-tap canceller were measured over a 20-MHz bandwidth centered at 2.5 GHz and produced an average of more than 35 dB of cancellation for various SI channels with tuning times that are significantly less than previous approaches. The performance of this unique method was also studied against other tuning techniques, and results indicate that it could supplant traditional adaptive learning approaches for future IBFD systems.

A 0.02–4.5-GHz LN(T)A in 28-nm CMOS for 5G Exploiting Noise Reduction and Current Reuse

In this article, a new noise reduction/cancellation technique is proposed to improve noise figure (NF) of a broadband low-noise transconductance amplifier (LNTA) for 5G receivers. The LNTA combines a common-gate (CG) stage for wideband input matching and a common-source (CS) stage for canceling the noise and distortion of the CG stage. Yet, another noise reduction is applied to reduce the channel thermal noise of the noise cancellation stage itself. The technique further exploits current reuse and increases transconductance of the CS transistor while keeping its power consumption low. Fabricated in 28-nm CMOS, the proposed LNTA is capable of driving an external 50-Ω load and achieves a NF of 2.09-3.2 dB and input return loss (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) better than -10 dB over the 3-dB bandwidth of 20 MHz-4.5 GHz while consuming 4.5 mW from a single 1-V power supply. The achieved gain (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> ) and IIP3 are 15.2 dB and -4.6 dBm, respectively.

Low complexity interference compensation for DFRFT‐based OFDM system with CFO

Discrete fractional Fourier transform (DFRFT) based orthogonal frequency division multiplexing (OFDM) system significantly outperforms the conventional discrete Fourier transform (DFT) based OFDM system in the presence of carrier frequency offset (CFO). However, to achieve the interference-free performance, the residual interference remaining after the channel equalisation in the fractional Fourier domain needs to be compensated. To enable this residual interference compensation with low complexity after DFRFT at the receiver, an accurate and generalized expression for inter-carrier interference (ICI) coefficient from interfering to the desired subcarrier is derived over a multipath fading channel with CFO. The derived ICI coefficient is validated at the DFRFT angle equal to π / 2 (i.e., for DFT-OFDM system) and over AWGN and flat channel. Monte Carlo simulation of symbol error rate (SER) over the Rayleigh fading channel is also carried out to verify the derived theoretical closed-form ICI coefficient for different values of the DFRFT angle. At the receiver, a low complexity residual interference cancellation stage is introduced by utilizing the banded matrix implementation of the derived closed-form residual ICI matrix for the DFRFT-OFDM system which only needs to perform O ( N ) operations for closely preserving the interference-free performance.

Ultra‐wideband complementary metal‐oxide semiconductor low noise amplifier using CS‐CG noise‐cancellation and dual resonance network techniques

In this paper, a low power ultra-wideband (UWB) low noise amplifier (LNA) with high and flat voltage gain is proposed using CS-CG noise-cancellation and dual resonance network techniques based on TSMC 180 nm technology. The CS-CG noise cancellation technique reduced the noise figure in 3-10.6 GHz frequency band, and the dual resonance network technique is applied to reach an acceptable input matching. In order to reduce the number of inductors, the active inductor is used in the noise cancellation stage. Also, to control voltage gain and input return loss, a resistor is connected in parallel to channel length modulation resistance of the transistor in the first stage. The developed LNA circuit provides a high and flat voltage gain of 12.75 dB with 0.65 dB variation, which is the result of using two stages common-source topology. An average noise figure of 2 dB, with its maximum value of 2.3 dB, an IIP3 of -8 dBm are obtained from 3 to 10.6 GHz, respectively. The obtained input and output matching value are better than -10 dB. The layout of proposed LNA occupies an area of 0.55 mm2 including ring pad and this structure consumes 11.56 mW from 1-V dc supply.

Techniques for Achieving High Isolation in RF Domain for Simultaneous Transmit and Receive

With the growth of wireless data traffic, additional spectrum is required to meet consumer demands. Consequently, innovative approaches are needed for efficient management of the available limited spectrum. To double the achievable spectral efficiency, a transceiver can be designed to receive and transmit signals simultaneously (STAR) across the same frequency band. However, due to the coupling of the high power transmitted signal into the collocated receiver, the receiver’s performance is degraded. For successful STAR realization, the coupled high-power transmit (Tx) signal should be suppressed by 100-120 dB over the entire operational bandwidth. So far, most STAR implementations are narrowband, and not useful for ultra wideband (UWB) communications. In this paper, we present a review of novel approaches employed to achieve improved cancellation across wide bandwidths in RF and propagation domains. Both single and multi-antenna systems are considered. Measurements show an average cancellation of 50 dB using two stages of RF signal cancellation.

THE IMPLICATIONS OF THE EXISTENCE OF THE ALLEGED CRIMINAL ACTS OF CORRUPTION TOWARDS THE IMPLEMENTATION OF THE CONSTRUCTION CONTRACT

&lt;p&gt;Construction contracts are civil relations, and is an agreement, principle principle in Book III Civil Code, and in construction contracts are generally used for the achievement of common goals. Fulfilling the needs of goods and services is an important part of governance, In connection with this the emergence of negative implications on the problem of the neglect of construction services in the process constrained indications of corruption. Contract cancellation stage in legal doctrine in Indonesia is only limited to contract and pre contract phase but also possible in the implementation phase by considering the principle of presumption of innocence as well as the principle of legal certainty, the implementation of construction contracts should proceed accordingly without having to override the legal process that runs from parties that are indicated to be corrupt. In the event that the construction contract is carried out in accordance with the basic principles of government procurement of goods / services that are efficient, effective, open and competitive, transparent, fair and accountable, in order to achieve development goals equally and in accordance with the mandate of the constitution of the Republic of Indonesia.&lt;/p&gt;

The Implications of The Existence of The Alleged Criminal Acts of Corruption Towards the Implementation of The Construction Contract

Construction contracts are civil relations, and is an agreement, principle principle in Book III Civil Code, and in construction contracts are generally used for the achievement of common goals. Fulfilling the needs of goods and services is an important part of governance, In connection with this the emergence of negative implications on the problem of the neglect of construction services in the process constrained indications of corruption. Contract cancellation stage in legal doctrine in Indonesia is only limited to contract and pre contract phase but also possible in the implementation phase by considering the principle of presumption of innocence as well as the principle of legal certainty, the implementation of construction contracts should proceed accordingly without having to override the legal process that runs from parties that are indicated to be corrupt. In the event that the construction contract is carried out in accordance with the basic principles of government procurement of goods / services that are efficient, effective, open and competitive, transparent, fair and accountable, in order to achieve development goals equally and in accordance with the mandate of the constitution of the Republic of Indonesia.