3,994 research outputs found
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
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
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
Full-Duplex Systems Using Multi-Reconfigurable Antennas
Full-duplex systems are expected to achieve 100% rate improvement over
half-duplex systems if the self-interference signal can be significantly
mitigated. In this paper, we propose the first full-duplex system utilizing
Multi-Reconfigurable Antenna (MRA) with ?90% rate improvement compared to
half-duplex systems. MRA is a dynamically reconfigurable antenna structure,
that is capable of changing its properties according to certain input
configurations. A comprehensive experimental analysis is conducted to
characterize the system performance in typical indoor environments. The
experiments are performed using a fabricated MRA that has 4096 configurable
radiation patterns. The achieved MRA-based passive self-interference
suppression is investigated, with detailed analysis for the MRA training
overhead. In addition, a heuristic-based approach is proposed to reduce the MRA
training overhead. The results show that at 1% training overhead, a total of
95dB self-interference cancellation is achieved in typical indoor environments.
The 95dB self-interference cancellation is experimentally shown to be
sufficient for 90% full-duplex rate improvement compared to half-duplex
systems.Comment: Submitted to IEEE Transactions on Wireless Communication
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
- …