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We propose the cross-layer based opportunistic multi-channel medium access control (MAC) protocols, which integrate the spectrum sensing at physical (PHY) layer with the packet scheduling at MAC layer, for the wireless ad hoc networks. Specifically, the MAC protocols enable the secondary users to identify and utilize the leftover frequency spectrum in a way(More)
We propose a quality-of-service (QoS) driven power and rate adaptation scheme over wireless links in mobile wireless networks. Specifically, our proposed scheme aims at maximizing the system throughput subject to a given delay QoS constraint. First, we derive an optimal adaptation policy by integrating information theory with the concept of effective(More)
By expressing two genes (hTERT and Cdk4), we have developed a method to reproducibly generate continuously replicating human bronchial epithelial cell (HBEC) lines that provide a novel resource to study the molecular pathogenesis of lung cancer and the differentiation of bronchial epithelial cells. Twelve human bronchial epithelial biopsy specimens obtained(More)
We formulate three intuitive semantic properties for top-k queries in probabilistic databases, and propose Global-Topk query semantics which satisfies all of them. We provide a dynamic programming algorithm to evaluate top-k queries under Global-Topk in simple probabilistic relations. For general probabilistic relations, we show a polynomial reduction to(More)
To clarify the brain mechanism for multifeature stimulus comparison, subjects matched the features of two serial visual stimuli in pairs. Stimulus pairs were of four categories: C-S-, color same, shape same (match); C-S+, color same, shape different (shape mismatch); C+S-, color different, shape same (color mismatch); C+S+, color different, shape different(More)
As the novel and effective approach to improving the utilization of the precious radio spectrum, cognitive radio technology is the key to realize the dynamic spectrum access (DSA) networks, where the secondary (unlicensed) users can opportunistically utilize the unused licensed spectrum in a way that confines the level of interference to the range the(More)
We propose a quality-of-service (QoS) driven power and rate adaptation scheme for multichannel communications systems over wireless links in mobile networks. In particular, we use the multichannel communications to model the conceptual architectures for either diversity or multiplexing systems, which play a fundamental role in physical-layer evolutions of(More)
We study physical-layer security in wireless ad hoc networks and investigate two types of multi-antenna transmission schemes for providing secrecy enhancements. To establish secure transmission against malicious eavesdroppers, we consider the generation of artificial noise with either sectoring or beamforming. For both approaches, we provide a statistical(More)
One of the biggest challenges in content based image retrieval is to solve the problem of “semantic gaps” between low-level features and high-level semantic concepts. In this paper, we aim to investigate various combinations of mid-level features to build an effective image retrieval system based on the bag-offeatures (BoF) model. Specifically, we study two(More)