The Key Laboratory of System Control and Information Processing

Shanghai, China

The Key Laboratory of System Control and Information Processing

Shanghai, China
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He J.,Shanghai JiaoTong University | He J.,The Key Laboratory of System Control and Information Processing | Duan X.,Zhejiang University | Cheng P.,Zhejiang University | Shi L.,Hong Kong University of Science and Technology
Automatica | Year: 2017

It is important and challenging to achieve accurate clock synchronization in wireless sensor networks. Various noises, e.g., communication delay, clock fluctuation and measurement errors, are inevitable and difficult to be estimated accurately, which is the main challenge for achieving accurate clock synchronization. In this paper, we focus on how to achieve accurate clock synchronization by considering a practical noise model, bounded noise, which may not satisfy any known distributions. The principle that a bounded monotonic sequence must possess a limit and the concept of maximum consensus are exploited to design a novel clock synchronization algorithm for the network to achieve accurate and fast synchronization. The proposed algorithm is fully distributed, with high synchronization accuracy and fast convergence speed, and is able to compensate both clock skew and offset simultaneously. Meanwhile, we prove that the algorithm converges with probability one, which means that an accurate clock synchronization is achieved. We further prove that the probability of the complete synchronization converges exponentially fast. Experiments and simulations are conducted to verify the noise model and demonstrate the effectiveness of the proposed algorithm. © 2017 Elsevier Ltd


Hu B.,Shanghai JiaoTong University | Hu B.,The Key Laboratory of System Control and Information Processing | Hua C.,Shanghai JiaoTong University | Chen C.,Shanghai JiaoTong University | And 3 more authors.
Wireless Networks | Year: 2017

In this paper, we consider the multi-group multicasting problem in a MIMO wireless cellular system, whereby the base station can generate multiple beampatterns to serve multiple groups simultaneously. Each user is interested in multiple multicast groups, but is only allowed to be assigned to one of them eventually during each transmission interval. We formulate it as a joint optimization problem of multicast beamformer design as well as user grouping, and admission control is also considered to account for the quality of service demands of individual users. To deal with this NP-hard problem, we adopt the big-M formulation method and the semidefinite relaxation scheme to reformulate it to a mixed-integer semidefinite programming problem. Three algorithms are developed to solve the obtained approximate problem with different computational costs. Simulation results are presented to demonstrate the performance of the proposed algorithms in terms of the number of admitted users, power consumption and computation time. © 2017 Springer Science+Business Media New York

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