Routing in Ad-Hoc Networks Using Minimum Connected Dominating Sets

1 Motivation An ad-hoc network is a multihop wireless network in which mobile hosts communicate over a shared, scarce wireless channel. An ad-hoc network is characterized by the absence of a wired backbone or any sort of centralized network management system to maintain routes as hosts move or turn oo or on. Since routes change quickly not only because end nodes move but also because intermediate nodes move, ad-hoc routing algorithms must react quickly to topology changes. Most of the recent work on routing in ad-hoc networks has focused on unicast datagram routing. This work can be grouped into two broad categories: routing on demand, also known as loose source routing CE 95, CMB 96, DRWT 96, JM 96, To 96]; and shortest-paths routing KCVP 95, MG 95, PB 94]. Typically, shortest-paths routing generates route updates upon host mobility, creating more overhead, while routing on demand uses cached routes whenever possible, resulting in a low route update overhead at the expense of possibly stale routes. Thus far, none of the currently proposed ad-hoc routing algorithms seek to exploit a structure similar to the wired backbone of packet cellular networks. In packet cellular networks , taking advantage of the backbone, routing algorithms can support ows, multicasting, and even fault-tolerant routing for mobile computers. In this paper, we impose a virtual backbone structure on the ad-hoc network, in order to support unicast, multicast, and fault-tolerant routing within the ad-hoc network. This virtual backbone diiers from the wired backbone of cellular networks in two key ways: (a) it may change as nodes move, and (b) it is not used primarily for routing packets or ows, but only for computing and updating routes. The primary routes for packets and ows are still computed by a shortest-paths computation; the virtual backbone can, if necessary, provide backup routes to handle interim failures. Because of the dynamic nature of the virtual backbone, our approach splits the routing problem into two levels: (a) nd and update the virtual backbone, and (b) then nd and update routes. The key contribution of this paper is to describe several alternatives for the rst part of nding and updating the virtual backbone. In this paper, to keep the virtual backbone as small as possible , we use an approximation to the minimum connected dominating set (MCDS) of the ad-hoc network topology as the virtual backbone. The hosts in the MCDS maintain local …