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

Azimuthal anisotropy (v2v_{2}) of high-pT_{T} π0\pi^{0} and direct γ\gamma in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

Preliminary results from the STAR collaboration of the azimuthal anisotropy $(v_{2})$ of $\pi^{0}$ and direct photon ($\gamma_{dir}$) at high transverse momentum (p$_{T}$) from Au+Au collisions at center-of-mass energy $\sqrt{s_{_{NN}}}=200$~GeV are presented. A shower-shape analysis is used to select a sample free of direct photons ($\pi^0$) and a sample rich in direct photons $\gamma_{rich}$. The relative contribution of background in the $\gamma_{rich}$ sample is determined assuming no associated charged particles nearby $\gamma_{dir}$. The $v_{2}$ of direct photons ($v_{2}^{\gamma_{dir}}$) at mid-rapidity ($|\eta^{\gamma_{dir}}|<1$) and high p$_{T}$ ($8< p_{T}^{\gamma_{dir}}<16$~GeV/$c$) is extracted from those of $\pi^{0}$ and neutral particles measured in the same kinematic range. In mid-central Au+Au collisions (10-40$\%$), the $v_{2}$ of $\pi^0$ ($v_{2}^{\pi^{0}}(p_{T})$) and charged particles ($v_{2}^{ch}(p_{T})$) are found to be $\sim$ 0.12 and nearly independent of p$_{T}$. The measured $v_{2}^{\gamma_{dir}}(p_{T})$ is positive finite and systematically smaller than that of $\pi^{0}$ and charged particles by a factor of $\sim$ 3. Although the large $v_{2}^{\pi^{0}}$ at such high p$_{T}$ might be partially due to the path-length dependence of energy loss, the non-zero value of $v_{2}^{\gamma_{dir}}$ indicates a bias of the reaction plane determination due to the presence of jets in the events. Systematic studies are currently in progress.Comment: 4 pages, 2 figures, Hot Quarks 2010, LaLonde Franc