Relay Selection for Bidirectional AF Relay Network with Outdated CSI

Most previous researches on bidirectional relay selection (RS) typically assume perfect channel state information (CSI). However, outdated CSI, caused by the the time-variation of channel, cannot be ignored in the practical system, and it will deteriorate the performance. In this paper, the effect of outdated CSI on the performance of bidirectional amplify-and-forward RS is investigated. The optimal single RS scheme in minimizing the symbol error rate (SER) is revised by incorporating the outdated channels. The analytical expressions of end-to-end signal to noise ratio (SNR) and symbol error rate (SER) are derived in a closed-form, along with the asymptotic SER expression in high SNR. All the analytical expressions are verified by the Monte-Carlo simulations. The analytical and the simulation results reveal that once CSI is outdated, the diversity order degrades to one from full diversity. Furthermore, a multiple RS scheme is proposed and verified that this scheme is a feasible solution to compensate the diversity loss caused by outdated CSI.Comment: accepted by IEEE Transactions on Vehicular Technolog

Area-minimizing Cones over Grassmannian Manifolds

In this paper, we extend Gary R. Lawlor's original examples of area-minimizing cones over nonoriented manifolds\cite{lawlor1991sufficient}. From the point view of submanifolds themselves, by considering real nonoriented Grassmannians, complex Grassmannians, quaternion Grassmannians and complex, quaternion projective spaces and Cayley projective plane as the Hermitian orthogonal projection operators uniformly, we prove that there exists a family of opposite cones associated with them. These cones are shown area-minimizing by Lawlor's Curvature Criterion, it also can be seen as direct proofs for these cones being area-minimizing under the perspective of isolated orbits of adjoint action and the perspective of symmetric spaces (\cite{kerckhove1994isolated},\cite{hirohashi2000area},\cite{kanno2002area},\cite{ohno2015area}). Additionally, for the left oriented real Grassmannian manifolds-the double cover of the nonoriented cases, by embedding them in the exterior vector spaces as unit simple vectors, we prove these cones are area-minimizing except one

Environmental dynamism, Innovation and dynamic capabilities: the case of China

Based on the resource-based view, creating and maintaining a long-term competitive advantage requires significant attention to developing and nurturing dynamic capabilities in emerging markets. This study considers environmental dynamism as a moderating variable, then builds a theoretical model for innovation strategy and dynamic capabilities, and finally summarizes the building mechanism for dynamic capabilities. The empirical results find that an innovation strategy can build and upgrade dynamic capabilities in both stable and rapidly changing environments. Managerial implications and future research directions are discussed