Recall and Precision in Distributed Bandwidth Allocation

Recent work on QoS in Mobile Ad Hoc Networks (MANETs) has shown that bandwidth needs to be reserved in a distributed manner by also including interfering nodes. However, in practice, QoS protocols have difficulties to locally determine the set of nodes that actually interfere with a given transmission. To solve this problem, it is not uncommon to consider all nodes within a distance of k hops (k-neighbors) as interfering nodes. In this paper we use Monte-Carlo methods to study the correlation between the k-neighborhood of a node and the set of interfering nodes. We compute expected values for both reservation recall -the fraction of interfering k-neighbors to all interferers -and reservation precision -the fraction of interfering k-neighbors to all k-neighbors. The two metrics reflect the quality of a reservation and the loss of resources due to over-reservation. We further investigate the impact of different physical layer properties (e.g., fading) and network settings (e.g., network density) on the quality of the reservations. Our results indicate that existing reservation techniques to ensure QoS are inadequate and that new techniques are needed to efficiently implement QoS in MANETs.