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.

Energy Efficiency Optimization for OFDM-Based Cognitive Radio Systems: A Water-Filling Factor Aided Search Method

Abstract: Conventional designs of OFDM-based cognitive radio (CR) systems mainly focus on the system throughput. Since nowdays the energy efficiency (EE) of wireless systems becomes more and more important, this paper intends to improve the system throughput for unit-energy consumption in OFDM-based CR systems. The energy-efficient power allocation problem of OFDM-based CR systems is studied under the total power constraint, the interference power constraint and the rate constraint. Since the energy-efficient power allocation problem is non-convex, in order to find the optimal power allocation at each subcarrier, we propose a novel method named water-filling factors aided search (WFAS) to solve the EE optimization problems with multiple constraints. The global e-optimality and the convergence of the proposed method are presented. The numerical results confirm the theoretical conclusions. The comparisons of the energy-efficient power allocation and the spectrum-efficient power allocation in OFDM-based CR systems are given under different constraints via numerical simulations as well.

Multiuser Diversity in Multiuser Two-Hop Cooperative Relay Wireless Networks: System Model and Performance Analysis

Abstract: Cooperative communications significantly improve the performance of wireless networks with the help of relay nodes, whereas multiuser diversity (MUD) is a kind of diversity inherent in multiuser systems. In this paper, we present a framework to analyze the performance of MUD in the multiuser two-hop cooperative relay networks (TCRNs). Based on this framework, we derive tight closed-form expressions of outage probability and symbol error probability (SEP) for the amplify-and-forward (AF), fixed decode-and-forward (DF), and selective DF protocols with MUD. Both the theoretical analysis and simulations show that in multiuser TCRNs, MUD orders of 2K, K, and 2K can be achieved for AF, fixed DF, and selective DF, respectively (where K is the number of users).

Local indistinguishability of orthogonal product states

Abstract: In the general bipartite quantum system $m\ensuremath{\bigotimes}n\phantom{\rule{0.16em}{0ex}}(m,n\ensuremath{\ge}3)$, Y.-L. Wang et al. [Phys. Rev. A 92, 032313 (2015)] presented $3(m+n)\ensuremath{-}9$ orthogonal product states which cannot be distinguished by local operations and classical communication (LOCC). In this paper, we aim to construct less locally indistinguishable orthogonal product states in $m\ensuremath{\bigotimes}n$. First, in the $3\ensuremath{\bigotimes}n\phantom{\rule{0.28em}{0ex}}(3ln)$ quantum system, we construct $3n\ensuremath{-}2$ locally indistinguishable orthogonal product states which are not unextendible product bases. Then, for $m\ensuremath{\bigotimes}n\phantom{\rule{0.28em}{0ex}}(4\ensuremath{\le}m\ensuremath{\le}n)$, we present $3n+m\ensuremath{-}4$ orthogonal product states which cannot be perfectly distinguished by LOCC. Finally, in the general bipartite quantum system $m\ensuremath{\bigotimes}n\phantom{\rule{0.28em}{0ex}}(3\ensuremath{\le}m\ensuremath{\le}n)$, we show a smaller set with $2n\ensuremath{-}1$ orthogonal product states and prove that these states are LOCC indistinguishable using a very simple but quite effective method. All of the above results demonstrate the phenomenon of nonlocality without entanglement.

Goodput-Aware Load Distribution for Real-Time Traffic over Multipath Networks

Abstract: Load distribution is a key research issue in deploying the limited network resources available to support traffic transmissions. Developing an effective solution is critical for enhancing traffic performance and network utilization. In this paper, we investigate the problem of load distribution for real-time traffic over multipath networks. Due to the path diversity and unreliability in heterogeneous overlay networks, large end-to-end delay and consecutive packet losses can significantly degrade the traffic flow’s goodput , whereas existing studies mainly focus on the delay or throughput performance. To address the challenging problems, we propose a G oodput- A ware L oad distribu T i ON (GALTON) model that includes three phases: (1) path status estimation to accurately sense the quality of each transport link, (2) flow rate assignment to optimize the aggregate goodput of input traffic, and (3) deadline-constrained packet interleaving to mitigate consecutive losses. We present a mathematical formulation for multipath load distribution and derive the solution based on utility theory. The performance of the proposed model is evaluated through semi-physical emulations in Exata involving both real Internet traffic traces and H.264 video streaming. Experimental results show that GALTON outperforms existing traffic distribution models in terms of goodput, video Peak Signal-to-Noise Ratio (PSNR), end-to-end delay, and aggregate loss rate.

Convergence of Satellite and Terrestrial Networks: A Comprehensive Survey

Abstract: The explosive growth of various services boosts the innovation and development in terrestrial communication systems for the implementation of the next generation mobile communication networks. However, simply utilizing limited resources in terrestrial communication networks is difficult to support the massive quality of service (QoS) aware requirements and it is hard to guarantee seamless coverage in far remote regions. Leveraging the intrinsic merits of high altitude and the ability of multicasting or broadcasting, satellite communication systems provide an opportunity for novel mobile communication networks with its tight interaction and complementary characteristics to traditional terrestrial networks. It is believed that the convergence of satellite and terrestrial networks can solve the problems existing in current mobile communication systems and make a profound effect on global information dissemination. In this paper, we make a comprehensive survey on the convergence of satellite and terrestrial networks. First, motivations and requirements of satellite-terrestrial network convergence are identified. Then, we summarize related architectures of existing literature, classify the taxonomy of researches on satellite-terrestrial networks, and present the performance evaluation works in different satellite-terrestrial networks. After that, the state-of-the-art of standardization, projects and the key application areas of satellite-terrestrial networks are also reviewed. Finally, we conclude the survey by highlighting the open issues and future directions.