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.

Comments on "Globally Maximizing, Locally Minimizing: Unsupervised Discriminant Projection with Application to Face and Palm Biometrics"

Abstract: In (Yang et al, 2007), UDP is proposed to address the limitation of LPP for the clustering and classification tasks In this communication, we show that the basic ideas of UDP and LPP are identical In particular, UDP is just a simplified version of LPP on the assumption that the local density is uniform

Resource Allocation in Spectrum-Sharing OFDMA Femtocells With Heterogeneous Services

Abstract: Femtocells are being considered a promising technique to improve the capacity and coverage for indoor wireless users. However, the cross-tier interference in the spectrum-sharing deployment of femtocells can degrade the system performance seriously. The resource allocation problem in both the uplink and the downlink for two-tier networks comprising spectrum-sharing femtocells and macrocells is investigated. A resource allocation scheme for cochannel femtocells is proposed, aiming to maximize the capacity for both delay-sensitive users and delay-tolerant users subject to the delay-sensitive users' quality-of-service constraint and an interference constraint imposed by the macrocell. The subchannel and power allocation problem is modeled as a mixed-integer programming problem, and then, it is transformed into a convex optimization problem by relaxing subchannel sharing; finally, it is solved by the dual decomposition method. Subsequently, an iterative subchannel and power allocation algorithm considering heterogeneous services and cross-tier interference is proposed for the problem using the subgradient update. A practical low-complexity distributed subchannel and power allocation algorithm is developed to reduce the computational cost. The complexity of the proposed algorithms is analyzed, and the effectiveness of the proposed algorithms is verified by simulations.

LTE-V: A TD-LTE-Based V2X Solution for Future Vehicular Network

Abstract: Diverse applications in vehicular network present specific requirements and challenges on wireless access technology. Although considered as the first standard, IEEE 802.11p shows the obvious drawbacks and is still in the field-trial stage. In this paper, we propose long-term evolution (LTE)-V as a systematic and integrated V2X solution based on time-division LTE (TD-LTE) 4G. LTE-V includes two modes: 1) LTE-V-direct and 2) LTE-V-cell. Comparing to IEEE 802.11p, LTE-V-direct is a new decentralized architecture which modifies TD-LTE physical layer and try to keep commonality as possible to provide short range direct communication, low latency, and high reliability improvements. By leveraging the centralized architecture with native features of TD-LTE, LTE-V-cell optimizes radio resource management for better supporting V2I. LTE-V-direct and LTE-V-cell coordinate with each other to provide an integrated V2X solution. Performance simulations based on sufficient scenarios and the prototype system with typical cases are presented. Finally, future works of LTE-V are envisioned.

One-step synthesis of easy-recycling TiO2-rGO nanocomposite photocatalysts with enhanced photocatalytic activity

Abstract: The addition of reduced graphene oxide (rGO) in the TiO2 has been demonstrated to be one of the effective methods to improve the photocatalytic performance of TiO2 photocatalyst. Despite tremendous efforts, developing facile and green synthetic method of TiO2-rGO nanocomposites still remains a great challenge. In this study, a one-step green hydrothermal method for the fabrication of easily recycled TiO2-rGO composites, based on the initial formation of strong-coupling TiO2-GO nanocomposite and the subsequent in situ reduction of GO to rGO during hydrothermal treatment, was developed in the pure water without using any reductant and surfactant. It is found that the TiO2 nanoparticles with a clean surface and a good dispersion are highly required for the formation of the easy-recycling TiO2-rGO composite photocatalyst. Photocatalytic experimental results indicated that compared with the high-efficiency P25 TiO2 precursor, the photocatalytic performance could be obviously improved (about 23%) for the decomposition of phenol after coupling 1-wt% rGO. The enhanced photocatalytic performance can be attributed the cooperation effect of the effective separation of charge carriers via rGO cocatalyst, the enrichment of phenol molecular on the rGO, and the strong coupling interaction between TiO2 nanoparticles and rGO nanosheets. Considering its completely green and facile preparation and recyclable feature from an aqueous solution, the present TiO2-rGO nanocomposite photocatalyst can be regards as one of the ideal photocatalysts for various potential applications.

Fabrication of β-Ga_2O_3 thin films and solar-blind photodetectors by laser MBE technology

Abstract: Laser molecular beam epitaxy technology has been employed to deposit β-gallium oxide (β-Ga2O3) on (0001) sapphire substrates. After optimizing the growth parameters, (2¯01)-oriented β-Ga2O3 thin film was obtained. Ultraviolet-visible absorption spectrum demonstrates that the prepared β-Ga2O3 thin film shows excellent solar-blind ultraviolet (UV) characteristic with a band gap of 5.02 eV. A prototype photodetector device with a metal-semiconductor-metal structure has been fabricated using high quality β-Ga2O3 film. The device exhibits obvious photoresponse under 254 nm UV light irradiation, suggesting a potential application in solar-blind photodetectors.