On the Scalability of Ad Hoc Wireless Networks

considers the problem of scaling ad hoc wireless networks now being applied to ur-ban mesh and sensor networks scenarios. Ad hoc networks involve multi-hop communication which has inherent scaling problems in that throughput per node drops as the square root of the number of nodes in the network. We investigate mechanisms for improving performance and scalability of multi-hop wireless networks, with focus on system architecture and routing protocol aspects. First we propose a generalized multi-tier hierarchical hybrid network with three tiers of radio nodes: low-power end-user mobile nodes (MN) at the lowest tier, higher power radio forwarding nodes (FN) that support multi-hop routing at intermediate level, and wired access points (AP) at the highest level. We present an analytical model for the capacity of the proposed network and identify conditions on transmission range and node density for scalability to be maintained. From the derived upper and lower bounds, it is shown that the low-tier capacity increase linearly with the number of FN’s, and the high-tier capacity grows linearly with the number of AP’s in the scaling region. The analytically obtained capacity results are validated with detailed system simulations for dense network scenarios. The simulation study also examines the allocation of separate channels t