Basic Issues Affecting Software Architecture

In this paper, we first comment that the bandwidth consumption in the shortest path tree can be reduced in the heterogeneous wireless networks because the routing of the shortest path tree here is more flexible. The shortest path tree in the heterogeneous wireless networks consists of two parts. The first one is composed of the cell and the wireless technology chosen by each mobile host. The second one is comprised of the wired links that connect the root of the tree and the chosen cells. Therefore, we can change the routing of the shortest path tree by selecting different cells and wireless technologies for the mobile hosts to reduce the bandwidth consumption. Explicitly, we formulate in this paper the selection of the cell and the wireless technology for each mobile host as an optimization problem, which is denoted as the Cell and Technology Selection Problem (CTSP) in the heterogeneous wireless networks for multicast communications. The problem is to select the cell and the wireless technology for each group member to minimize the total bandwidth cost of the shortest path tree. We design a mechanism, which includes an Integer Linear Programming (ILP) formulation, a distributed algorithm, and a network protocol, to solve the CTSP. We use ILP to formulate the CTSP, and the network operator can use our ILP formulation to find the optimal solution for network planning. We show that CTSP is NP-hard, which, in turn, justifies the necessity of designing efficient algorithms for suboptimal solutions. We devise an algorithm LAGRANGE, which is based on Lagrangean relaxation on our ILP formulation. Keywords— Heterogeneous networks, wireless