1,202 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
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
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
A Robust Beamformer Based on Weighted Sparse Constraint
Applying a sparse constraint on the beam pattern has been suggested to
suppress the sidelobe level of a minimum variance distortionless response
(MVDR) beamformer. In this letter, we introduce a weighted sparse constraint in
the beamformer design to provide a lower sidelobe level and deeper nulls for
interference avoidance, as compared with a conventional MVDR beamformer. The
proposed beamformer also shows improved robustness against the mismatch between
the steering angle and the direction of arrival (DOA) of the desired signal,
caused by imperfect estimation of DOA.Comment: 4 pages, 2 figure
Rezension zu: Alon, Ilan: China Rules: Globalization and Political Transformation. Basingstoke, 2009
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Born global firms’ growth and collaborative entry mode: the role of transnational entrepreneurs
Purpose
The purpose of this paper is to investigate the role of transnational entrepreneurs in growing born global firms, with a focus on the growth process facilitated by collaborative entry mode.
Design/methodology/approach
The author chose the solar photovoltaic industry as the empirical setting. This industry is a particularly good context for the study because many firms in this industry sell knowledge-intensive products internationally from their inception. The primary data consist of 32 in-depth interviews with entrepreneurs, industry association representatives, research institute scholars, and professional service firms.
Findings
The study highlights the importance of transnational entrepreneurs who develop born global firms to maturity by using their technological knowledge, international connections, and bicultural advantages to navigate and leverage institutional complexity. Collaborative entry mode with distributors enables born global firms’ high growth rapidly, whereas transnational entrepreneurs play a central role in building and expanding international network. Initial public offering in overseas stock exchange accelerates the high growth trajectory of born global firm by signalling its maturity.
Research limitations/implications
The author took a process perspective by examining the growth and maturity of born global firms by collaborative partnership; the author’s focus on the role of transnational entrepreneurs highlighted entrepreneurs’ sensitivity to institutional complexity along the growth trajectory.
Practical implications
The author recommends both incumbent and entrepreneurial firms in developed economies collaborate with transnational entrepreneurs in various business areas. Industry firms may be able to cooperate on product and marketing development, and professional service firms can offer services to expand born global firms further, because transnational entrepreneurs follow the global “rules of the game”.
Originality/value
The author shed important light on the role of transnational entrepreneurs throughout the growth of born global firms via collaborative entry mode. Furthermore, the author develops a multilevel framework for analysing the combined influence of transnational entrepreneur and institutional complexity on the growth of born global firm
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