Multi-Tier Ad Hoc Mesh Networks with Radio Forwarding Nodes

This paper investigates a three-tier hierarchical hybrid wireless network designed to provide significant improvements in system capacity and performance relative to conventional "flat" ad hoc and two-tier "hybrid" networking approaches. The analytical results illustrate that in a three-tier hierarchical network with n_A access points (AP), n_F dual-radio forwarding nodes (FN), and n_M mobile nodes (MN), linear scaling of low-tier capacity can be achieved when the low-tier transmission range satisfies r_L = O(1/radic(n_F)); linear scaling of high-tier capacity can be approached in the scaling regime n_A = Omega(radic(n_F)) and n_A = O(n_F/log n_F), when the high-tier transmission range satisfies r_H = O(1/radic(n_A)). The scaling properties of the three-tier hierarchical ad hoc network are studied using ns-2 based system simulation models. In particular, we investigate the impact of relative node densities and traffic pattern on the scalability of the network. The simulation results are consistent with the analysis, and demonstrate that system throughput can be scaled by using the right proportions of FN\´s and AP\´s, making it possible to design high-capacity, low-cost mesh networks with a moderate number of radio FN\´s and only a few wired AP\´s.