Beijing University of Posts and Telecommunications

About: Beijing University of Posts and Telecommunications is a education organization based out in Beijing, Beijing, China. It is known for research contribution in the topics: MIMO & Quality of service. The organization has 39576 authors who have published 41525 publications receiving 403759 citations. The organization is also known as: BUPT.

On reliability-optimized controller placement for Software-Defined Networks

Abstract: By decoupling control plane and data plane, Software-Defined Networking (SDN) approach s i m p l i f i e s network management and speeds up network innovations. These benefits have led not only to prototypes, but also real SDN deployments. For wide-area SDN deployments, multiple controllers are often required, and the placement of these controllers becomes a particularly important task in the SDN context. This paper studies the problem of placing controllers in SDNs, so as to maximize the reliability of SDN control networks. We present a novel metric, called expected percentage of control path loss, to characterize the reliability of SDN control networks. We formulate the reliability-aware control placement problem, prove its NP-hardness, and examine several placement algorithms that can solve this problem. Through extensive simulations using real topologies, we show how the number of controllers and their placement influence the reliability of SDN control networks. Besides, we also found that, through strategic controller placement, the reliability of SDN control networks can be significantly improved without introducing unacceptable switch-to-controller latencies.

Mining Spectrum Usage Data: A Large-Scale Spectrum Measurement Study

Abstract: Dynamic spectrum access has been a subject of extensive study in recent years. The increasing volume of literatures calls for a deeper understanding of the characteristics of current spectrum utilization. In this paper, we present a detailed spectrum measurement study, with data collected in the 20 MHz to 3 GHz spectrum band and at four locations concurrently in Guangdong province of China. We examine the statistics of the collected data, including channel vacancy statistics, channel utilization within each individual wireless service, and the spectral and spatial correlation of these measures. Main findings include that the channel vacancy durations follow an exponential-like distribution, but are not independently distributed over time, and that significant spectral and spatial correlations are found between channels of the same service. We then exploit such spectrum correlation to develop a 2D frequent pattern mining algorithm that can predict channel availability based on past observations with considerable accuracy.

Situation and development tendency of indoor positioning

Abstract: This paper introduces the significance of indoor positioning and analyzes the related problems. The latest research on indoor positioning is introduced. Further, the positioning accuracy and the cost of typical local and wide area indoor positioning systems are compared. The results of the comparison show that Time & Code Division-Orthogonal Frequency Division Multiplexing (TC-OFDM) is a system that can achieve real-time meter-accuracy of indoor positioning in a wide area. Finally, in this paper, we indicate that the seamless high-accuracy indoor positioning in a wide area is the development trend of indoor positioning. The seamless Location Based Services (LBS) architecture based on a heterogeneous network, key technologies in indoor positioning for decimeter-accuracy and seamless outdoor and indoor Geographic Information System (GIS) are elaborated as the most important research fields of future indoor positioning.

Cross-Domain Recommendation via Cluster-Level Latent Factor Model

Abstract: Recommender systems always aim to provide recommendations for a user based on historical ratings collected from a single domain (e.g., movies or books) only, which may suffer from the data sparsity problem. Recently, several recommendation models have been proposed to transfer knowledge by pooling together the rating data from multiple domains to alleviate the sparsity problem, which typically assume that multiple domains share a latent common rating pattern based on the user-item co-clustering. In practice, however, the related domains do not necessarily share such a common rating pattern, and diversity among the related domains might outweigh the advantages of such common pattern, which may result in performance degradations. In this paper, we propose a novel cluster-level based latent factor model to enhance the cross-domain recommendation, which can not only learn the common rating pattern shared across domains with the flexibility in controlling the optimal level of sharing, but also learn the domain-specific rating patterns of users in each domain that involve the discriminative information propitious to performance improvement. To this end, the proposed model is formulated as an optimization problem based on joint nonnegative matrix tri-factorization and an efficient alternating minimization algorithm is developed with convergence guarantee. Extensive experiments on several real world datasets suggest that our proposed model outperforms the state-of-the-art methods for the cross-domain recommendation task.

Transformations for a generalized variable-coefficient nonlinear Schrodinger model from plasma physics, arterial mechanics and optical fibers with symbolic computation

Abstract: Describing space and laboratory plasmas, arterial mechanics and optical fibers, a generalized variable-coefficient nonlinear Schrodinger model is hereby under investigation. Four transformations have been constructed from such a model to the known standard and cylindrical nonlinear Schrodinger equations with the relevant constraints on the variable coefficients presented. Symbolic computation is performed. Specialities of those transformations are discussed. Analytic solutions of such a generalized variable-coefficient model can be obtained via those transformations from the analytic solutions of the standard and cylindrical ones.