http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/105 2026-05-18T03:56:33Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/848 Estimation on efficient of distribute channel allocation schemes for cellular network Do, Huu Tri; Vu, Duy Loi; Bui, Thien Minh The efficient management and sharing of the spectrum among the users is an important issue, frequency channels have to be reused as much as possible in order to support the many thousands of simultaneous call in any typical of mobile system. In cellular architecture, cell is serviced by a base station located at its center. A number of cells are linked to a mobile switching center which also acts as a gateway of the cellular network to the existing wired networks liked PSTN, ISDN or LAN-WAN based networks. A base station communicates with the mobile station through wireless links, and with the MSC’s through wire-line links. This paper deals with some estimations on efficient of distribute channel allocation scheme for cellular networks and then LBSB scheme is selected to improve it’s efficient, that is, the first, channel borrowing is not only neighbours but in compact pattern and the second, when a cell become hot, it repeat to borrow channel until reaching average degree of coldness of networks, that mean X=C.(dc avr-dc). VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 3 (M.P), P. 171-178 2008-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/845 Using high algebra to design frequency divider include hazard Nguyen, Quy Thuong Normally the frequency divider designed by Boole algebra and to design a frequency divider with any divide factor, we have to repeat all over again every design step as the same. So to avoid of wasting time and money, instead of using traditional Boole algebra in digital technical we replace it by mathematical models in high algebra. And because of that we can design frequency dividers use computer. VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 3 (M.P), P. 163-170 2008-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/844 Quantum kinetic equation in the quantum hadrondynamics (QHD-I) model Phan, Hong Lien Within the framework of the Walecka model (QHD-I)[1] the renormalized effective Dirac equation and the kinetic equation for fermion are presented. In fact, the fermion propa- gator in the medium is dramatically different from that in the vacuum. The main feature is the treating of the fermion distribution in non equilibrium, which depends on the interaction rate involving temperature. VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 3 (M.P), P. 145-154 2008-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/839 Oscilation and Convergence for a Neutral Difference Equation Dinh, Cong Huong The oscillation and convergence of the solutions of neutral difference equation (xn + δxn−τ ) + Xr i=1 αi(n)F(xn−mi ) = 0, n = 0, 1, · · · are investigated, where mi ∈ N0, ∀i = 1, r and F is a function mapping R to R. VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 3 (M.P), P. 133-143 2008-01-01T00:00:00Z