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Huang S.,National University of Defense Technology | Li H.,University of British Columbia | Wu J.,National Digital Switching System Engineering Technical Researching Center | Leung V.C.M.,University of British Columbia
IEEE Transactions on Wireless Communications | Year: 2012

Simulcasting involves transmitting the same signal simultaneously over several antennas on the same carrier frequency. We derive the optimal grouping condition for simulcasting over a massively distributed antenna system (DAS) employing orthogonal space-time block coding (STBC), where the order of the STBC coding matrix n o is smaller than the number of remote antenna units (RAUs). While the optimum grouping minimizes the average bit error rate (BER) in the coverage area, we further propose two heuristic grouping rules and derive the corresponding stream-balanced grouping schemes in three DAS topologies, namely, linear, hexagonal and square lattice, to achieve low average BER across the area covered by the DAS. Simulation results for the different topologies confirm the superiority of the proposed grouping schemes compared with the other grouping methods. Also, when either n o or the RAU density increases, the average BER decreases. © 2012 IEEE.

Yao J.,Shanghai JiaoTong University | Costanzo G.T.,Technical University of Denmark | Zhu G.,Ecole Polytechnique de Montreal | Wen B.,National Digital Switching System Engineering Technical Researching Center
IEEE Transactions on Industrial Electronics | Year: 2015

This paper presents a control scheme for thermal management in smart buildings based on predictive power admission control. This approach combines model predictive control with budget-schedulability analysis in order to reduce peak power consumption as well as ensure thermal comfort. First, the power budget with a given thermal comfort constraint is optimized through budget-schedulability analysis which amounts to solving a constrained linear programming problem. Second, the effective peak power demand is reduced by means of the optimal scheduling and cooperative operation of multiple thermal appliances. The performance of the proposed control scheme is assessed by simulation based on the thermal dynamics of a real eight-room office building located at Danish Technical University. © 1982-2012 IEEE.

Luo W.,National Digital Switching System Engineering Technical Researching Center
IEEE Wireless Communications and Networking Conference, WCNC | Year: 2013

The unstable characteristic of ill-conditioned system is used to guarantee wireless security in this paper. The use of ill-conditioned theory to protect wireless transmissions is proposed as a way to secure wireless networks at physical layer. Firstly, the problem of randomized transmission is converted to that of solving ill-conditioned equation to guarantee wireless transmissions with inherent low-probability-of interception (LPI). Secondly, a conditional ill-conditioned optimization function is constructed. The function of legitimate node is stable because of its matched channel. But the function of eavesdropper is randomized because that she has not the legitimate conditions, which relate to the wireless medium contains domain-specific information. In this context, we propose a security scheme for wireless security in time-variant channels. In this scheme, the variable part of channels is converted to additional conditions, which can be solved by optimizing parameters. In contrast to conventional physical-layer security techniques, the scheme exploits the redundancy of ill-conditioned problem's solutions instead of array redundancy for deliberate signal randomization, which effectively randomizes the eavesdropper's received signals but not the authorized receiver's signals. Extensive simulations and analysis results show that our proposed scheme is useful for securing wireless transmissions. © 2013 IEEE.

Liu Q.,National Digital Switching System Engineering Technical Researching Center | Wang B.-Q.,National Digital Switching System Engineering Technical Researching Center | Xu K.,Tsinghua University
Jisuanji Xuebao/Chinese Journal of Computers | Year: 2010

In order to keep consistency and coherence of network's development, the next-generation network does a lot of attempts to integrate the underlying network heterogeneity of existing communication infrastructure, support information for all areas, and ensure network management, controllability, and reliability. The paper analyzes the development direction of existing network and the next-generation network, and proposes the construction principle of the component based hierarchical reconfigurable networks. The reconfiguration principle, model, function entity cooperate scheme, and the specific implement scheme are introduced so that the autonomy, reactivity and initiative in the construct and reconfiguration process is ensured. Experiments prove the flexibility and scalability of the reconfigurable network.

Zhang Y.-Y.,National Digital Switching System Engineering Technical Researching Center | Yu H.-Y.,National Digital Switching System Engineering Technical Researching Center | Zhang J.-K.,McMaster University | Zhu Y.-J.,National Digital Switching System Engineering Technical Researching Center | Wang T.,National Digital Switching System Engineering Technical Researching Center
Optics Letters | Year: 2016

We consider an indoor multi-input single-output (MISO) visible light communication (VLC) system without channel state information at the transmitter. For such a system, an energy-efficient time-collaborative modulation (TCM) constellation is first designed by minimizing a total optical power subject to a fixed minimum Euclidean distance. Then, a new space-time transmission scheme is proposed. Comprehensive computer simulations indicate that our proposed design always has better average error performance within illumination coverage area than the currently available schemes for this application.

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