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—Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without upper layer data encryption. However, they are hampered by wireless channel conditions: absent feedback, they are typically feasible only when the source-destination channel is better than the source-eaves-dropper channel. Node cooperation is a means to(More)
A novel approach of blind channel estimation for OFDM systems is proposed. A linear transformation is applied on each block before it enters the OFDM system. The transform imposes a correlation structure on the transmitted blocks, which is exploited at the receiver to recover the channel via simple cross-correlation operations. The proposed approach is(More)
—We present a novel frequency-domain framework for the identification of a multiple-input multiple-output (MIMO) system driven by white, mutually independent, unobservable inputs. The system frequency response is obtained based on singular value decomposition (SVD) of a matrix constructed based on the power-spectrum and slices of polyspectra of the system(More)
We address the problem of improving the spatial resolution of ultrasound images through blind deconvolution. The ultrasound image formation process in the RF domain can be expressed as a spatio-temporal convolution between the tissue response and the ultrasonic system response, plus additive noise. Convolutional components of the dispersive attenuation and(More)
— A novel cross-correlation based framework is proposed for the problem of blind equalization in communications. We assume that we have access to two observations obtained either by sampling, at the symbol rate, the outputs of two sensors or by oversampling, by a factor of two, the output of a single sensor. In either case, the two observations correspond(More)
—This work presents an energy efficient, low-overhead scheme for cooperative beamforming in ad hoc networks. Collaborating nodes retransmit local signals to faraway destinations, multiplying the received analog waveform by a complex weight chosen (in a distributed fashion) to maximize the received SNR. The improvement in SNR is explicitly derived for a(More)
A physical layer approach to security for wireless networks is considered. In single-antenna wireless systems, such approaches are hampered by channel conditions in the presence of one or more eavesdroppers. Cooperation has the potential to overcome this problem and improve the security of of wireless communications. In this paper, an amplify-and-forward(More)
—This paper studies secrecy rate optimization in a wireless network with a single-antenna source, a multi-antenna destination and a multi-antenna eavesdropper. This is an unfavorable scenario for secrecy performance as the system is interference-limited. In the literature, assuming that the receiver operates in half duplex (HD) mode, the aforementioned(More)