On the Scalability of Hierarchical Hybrid Wireless Networks

This paper presents an analysis of the scaling properties of a three-tier hierarchical hybrid wireless network. The network under consideration, which arises in mesh networking scenarios such as 802.11s, aims to achieve better capacity than ad hoc networks without infrastructure support, and also reduces the investment on wired infrastructure. In particular, the hierarchical hybrid network has three tiers consisting of mobile nodes, radio forwarding nodes and wired access points. For a three-level network of n₁, access points, n₂ forwarding nodes and n₃ mobile nodes, we analyze throughput in terms of two tiers of packets: those transmitted by mobile nodes (low-tier) and those transmitted by forwarding nodes and access points (high-tier). It is shown that low-tier capacity increases linearly with n₂, and high-tier capacity increases linearly with n₁ when n₁ grows asymptotically faster than radicn₂. These results, which are consistent with earlier simulation studies, demonstrate the value of adding radio forwarding nodes to improve scaling behavior and reduce the required number of wired access points. In order to model the capacity of the proposed network, we also study the capacity and traffic distribution of random aggregate networks.