All-Digital Self-interference Cancellation Technique for Full-duplex Systems

Full-duplex systems are expected to double the spectral efficiency compared to conventional half-duplex systems if the self-interference signal can be significantly mitigated. Digital cancellation is one of the lowest complexity self-interference cancellation techniques in full-duplex systems. However, its mitigation capability is very limited, mainly due to transmitter and receiver circuit's impairments. In this paper, we propose a novel digital self-interference cancellation technique for full-duplex systems. The proposed technique is shown to significantly mitigate the self-interference signal as well as the associated transmitter and receiver impairments. In the proposed technique, an auxiliary receiver chain is used to obtain a digital-domain copy of the transmitted Radio Frequency (RF) self-interference signal. The self-interference copy is then used in the digital-domain to cancel out both the self-interference signal and the associated impairments. Furthermore, to alleviate the receiver phase noise effect, a common oscillator is shared between the auxiliary and ordinary receiver chains. A thorough analytical and numerical analysis for the effect of the transmitter and receiver impairments on the cancellation capability of the proposed technique is presented. Finally, the overall performance is numerically investigated showing that using the proposed technique, the self-interference signal could be mitigated to ~3dB higher than the receiver noise floor, which results in up to 76% rate improvement compared to conventional half-duplex systems at 20dBm transmit power values.Comment: Submitted to IEEE Transactions on Wireless Communication

On Phase Noise Suppression in Full-Duplex Systems

Oscillator phase noise has been shown to be one of the main performance limiting factors in full-duplex systems. In this paper, we consider the problem of self-interference cancellation with phase noise suppression in full-duplex systems. The feasibility of performing phase noise suppression in full-duplex systems in terms of both complexity and achieved gain is analytically and experimentally investigated. First, the effect of phase noise on full-duplex systems and the possibility of performing phase noise suppression are studied. Two different phase noise suppression techniques with a detailed complexity analysis are then proposed. For each suppression technique, both free-running and phase locked loop based oscillators are considered. Due to the fact that full-duplex system performance highly depends on hardware impairments, experimental analysis is essential for reliable results. In this paper, the performance of the proposed techniques is experimentally investigated in a typical indoor environment. The experimental results are shown to confirm the results obtained from numerical simulations on two different experimental research platforms. At the end, the tradeoff between the required complexity and the gain achieved using phase noise suppression is discussed.Comment: Published in IEEE transactions on wireless communications on October-2014. Please refer to the IEEE version for the most updated documen

Nonlocal initial value problems for implicit differential equations with Hilfer–Hadamard fractional derivative

In this paper, the Schaefer's fixed-point theorem is used to investigate the existence of solutions to nonlocal initial value problems for implicit differential equations with Hilfer–Hadamard fractional derivative. Then the Ulam stability result is obtained by using Banach contraction principle. An example is given to illustrate the applications of the main result

A General Study on Langevin Equations of Arbitrary Order

In this paper, the broad study depends on Langevin differential equations (LDE) of arbitrary order.The fractional order is in terms of ψ-Hilfer fractional operator. This work reveals the dynamicalbehaviour such as existence, uniqueness and stability solutions for LDE involving ψ-Hilfer fractionalerivative (HFD). Thus the fractional LDE with boundary condition, impulsive effect and nonlocalconditions are taken in account to prove the result

Gabion basket for reducing scour around a rectangular bridge pier

Riprap, a slit inside the pier, a number of piles located in front of a pier, collars, and other strategies have all been used to control scouring around bridge piers. In this study, a new alternative countermeasure for reducing scour around the rectangular bridge pier was investigated. A gabion basket —a stone basket attached to the upstream face of the pier—was investigated experimentally for reducing scouring depth around the bridge pier as a countermeasure in a clear-water condition. For estimating the efficiency of using the stone basket as a countermeasure for reducing scour, the scour findings of the pier with no modifications were used as a basis for comparison. The findings indicate that the pier using a stone basket significantly reduced the scour depth. According to the findings, the pier with a stone basket size of dg/B = 0.3 lowered the depth of scouring to 50%, and the best relative length of the stone basket was Lg/B = 0.5. Based on the experimental findings, a formula for predicting scour depth at rectangular bridge piers was developed. The results of this study may be used in the field of application for bridge pier protection design

Self-Interference Cancellation with Nonlinear Distortion Suppression for Full-Duplex Systems

In full-duplex systems, due to the strong self-interference signal, system nonlinearities become a significant limiting factor that bounds the possible cancellable self-interference power. In this paper, a self-interference cancellation scheme for full-duplex orthogonal frequency division multiplexing systems is proposed. The proposed scheme increases the amount of cancellable self-interference power by suppressing the distortion caused by the transmitter and receiver nonlinearities. An iterative technique is used to jointly estimate the self-interference channel and the nonlinearity coefficients required to suppress the distortion signal. The performance is numerically investigated showing that the proposed scheme achieves a performance that is less than 0.5dB off the performance of a linear full-duplex system.Comment: To be presented in Asilomar Conference on Signals, Systems & Computers (November 2013

Editorial: Subclinical hypothyroidism in children with Down syndrome: To treat or not to treat???

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