6,692 research outputs found
Sidelobe Suppression for Capon Beamforming with Mainlobe to Sidelobe Power Ratio Maximization
High sidelobe level is a major disadvantage of the Capon beamforming. To
suppress the sidelobe, this paper introduces a mainlobe to sidelobe power ratio
constraint to the Capon beamforming. it minimizes the sidelobe power while
keeping the mainlobe power constant. Simulations show that the obtained
beamformer outperforms the Capon beamformer.Comment: 8 pages, 2 figure
Enhanced Compressive Wideband Frequency Spectrum Sensing for Dynamic Spectrum Access
Wideband spectrum sensing detects the unused spectrum holes for dynamic
spectrum access (DSA). Too high sampling rate is the main problem. Compressive
sensing (CS) can reconstruct sparse signal with much fewer randomized samples
than Nyquist sampling with high probability. Since survey shows that the
monitored signal is sparse in frequency domain, CS can deal with the sampling
burden. Random samples can be obtained by the analog-to-information converter.
Signal recovery can be formulated as an L0 norm minimization and a linear
measurement fitting constraint. In DSA, the static spectrum allocation of
primary radios means the bounds between different types of primary radios are
known in advance. To incorporate this a priori information, we divide the whole
spectrum into subsections according to the spectrum allocation policy. In the
new optimization model, the minimization of the L2 norm of each subsection is
used to encourage the cluster distribution locally, while the L0 norm of the L2
norms is minimized to give sparse distribution globally. Because the L0/L2
optimization is not convex, an iteratively re-weighted L1/L2 optimization is
proposed to approximate it. Simulations demonstrate the proposed method
outperforms others in accuracy, denoising ability, etc.Comment: 23 pages, 6 figures, 4 table. arXiv admin note: substantial text
overlap with arXiv:1005.180
Sidelobe Suppression for Robust Beamformer via The Mixed Norm Constraint
Applying a sparse constraint on the beam pattern has been suggested to
suppress the sidelobe of the minimum variance distortionless response (MVDR)
beamformer recently. To further improve the performance, we add a mixed norm
constraint on the beam pattern. It matches the beam pattern better and
encourages dense distribution in mainlobe and sparse distribution in sidelobe.
The obtained beamformer has a lower sidelobe level and deeper nulls for
interference avoidance than the standard sparse constraint based beamformer.
Simulation demonstrates that the SINR gain is considerable for its lower
sidelobe level and deeper nulling for interference, while the robustness
against the mismatch between the steering angle and the direction of arrival
(DOA) of the desired signal, caused by imperfect estimation of DOA, is
maintained too.Comment: 10 pages, 3 figures; accepted by Wireless Personal Communication
Lexically Constrained Decoding for Sequence Generation Using Grid Beam Search
We present Grid Beam Search (GBS), an algorithm which extends beam search to
allow the inclusion of pre-specified lexical constraints. The algorithm can be
used with any model that generates a sequence , by maximizing . Lexical
constraints take the form of phrases or words that must be present in the
output sequence. This is a very general way to incorporate additional knowledge
into a model's output without requiring any modification of the model
parameters or training data. We demonstrate the feasibility and flexibility of
Lexically Constrained Decoding by conducting experiments on Neural
Interactive-Predictive Translation, as well as Domain Adaptation for Neural
Machine Translation. Experiments show that GBS can provide large improvements
in translation quality in interactive scenarios, and that, even without any
user input, GBS can be used to achieve significant gains in performance in
domain adaptation scenarios.Comment: Accepted as a long paper at ACL 201
Themed issue: Optofluidics
The term optofluidics defines a growing
research area that integrates optics and
microfluidics in ways that enable unique
strengths and advantages for a broad range
of applications. The First International
Conference on Optofluidics (Optofluidics-
2011) organized by Xiβan Jiaotong
University and Lab on a Chip on 11β12
December 2011 featured work in this field,
with an exciting two-day program of presentations
and discussions. We are happy
that Lab on a Chip, a major publication
destination for optofluidic research, has
scheduled this themed issue on Optofluidics.
We are especially heartened that the optofluidics
community has responded enthusiastically
with a large number of excellent
manuscript submissions
- β¦