Adaptive Grouping Scheme Research Articles

An adaptive grouping scheme in ultra-dense IEEE 802.11ax network using buffer state report based two-stage mechanism

IEEE 802.11ax, which is an emerging WLAN standard, aims at providing highly efficient communication in ultra-dense wireless networks. However, due to a large number of stations (STAs) in the ultra-dense device deployment scenarios, the potentially high packet collision rate significantly decreases the communication efficiency of WLAN. In this paper, we propose an adaptive STA grouping scheme to overcome this dense network challenge in IEEE 802.11ax by using Buffer State Report (BSR) based Two-stage Mechanism (BTM). In order to achieve the optimal efficiency of BSR delivery, we analyze the functional relationship between STA number in group and Resource Unit (RU) efficiency. Based on this analysis results, an adaptive STA grouping algorithm with variable group size is proposed to achieve efficient grouping in BTM. The numerical results demonstrate that the proposed adaptive BTM grouping algorithm significantly improves the BSR delivery efficiency and the throughput of overall system and each STA in the ultra-dense wireless network.

Fast multipole method based solution of electrostatic and magnetostatic field problems

Applications of boundary element methods (BEM) to the solution of static field problems in electrical engineering are considered in this paper. The choice of a suitable BEM formulation for electrostatics, steady current flow fields or magnetostatics is discussed from user's point of view. The dense BEM matrix is compressed with an enhanced fast multipole method (FMM) which combines well-known BEM techniques with the FMM approach. An adaptive grouping scheme for problem oriented meshes is presented along with a discussion on the influence of the mesh to the efficiency of the FMM. The computational costs of the FMM algorithm are analyzed for typical problems in practice. Finally, some electrostatic and magnetostatic numerical examples demonstrate the simple usability and the efficiency of the FMM.