Three-dimensional geometric data play fundamental roles in many computer vision applications. However, their scale-dependent nature, i.e. the relative variation in the spatial extents of local geometric structures, is often overlooked. In this paper we present a comprehensive framework for exploiting this 3D geometric scale variability. Specifically, we focus on detecting scale-dependent geometric features on triangular mesh models of arbitrary topology. The key idea of our approach is to analyze the geometric scale variability of a given 3D model in the scale-space of a dense and regular 2D representation of its surface geometry encoded by the surface normals. We derive novel corner and edge detectors, as well as an automatic scale selection method, that acts upon this representation to detect salient geometric features and determine their intrinsic scales. We evaluate the effectiveness and robustness of our method on a number of models of different topology. The results show that the resulting scale-dependent geometric feature set provides a reliable basis for constructing a rich but concise representation of the geometric structure at hand.

This paper illustrates how networking protocols can inadvertently exacerbate obstacles to providing real-time guarantees for distributed problem solving in wireless mobile and sensor networks. We analyze the effects of control packet timing on providing quality of service guarantees. Inappropriate timing of control packets gives rise to synchronizations that result in sharp increases and decreases in throughput with small changes in node speed. Such synchronizations can seriously jeopardize network performance with direct effect on real-time guarantees. This paper introduces these synchronizations, analyzes them and suggests ways to modify the control packet timing to overcome them. These analyses include investigating the role of buffering at the network layer and its impact on network throughput. We analyze these effects and evaluate our protocol enhancements through simulation studies.

The ability of a mobile ad hoc network (MANET) to provide adequate quality of service (QoS) is limited by the ability of the underlying routing protocol to provide consistent behavior despite the inherent dynamics of a mobile computing environment. In this paper we study three MANET routing protocols: OLSR, DSR and AODV, with an emphasis on the effect they have on various QoS metrics. We describe and analyze how the protocols differ in the mechanisms they use to select paths, detect broken links, and buffer messages during periods of link outage. The effects of these differences are quantified in terms of packet delivery ratio, end-to-end hop count, end-to-end latency, and mechanism overhead. We show that the proactive protocol, OLSR, builds paths with consistently lower hop counts than the reactive protocols, AODV and DSR, a fact that leads to a reduction in end-to-end latency that assists a QoS model in meeting timing requirements and improves global network performance. We further show the impact of broken link detection latency on the packet delivery ratio. A routing protocol that can not quickly recover from link breakage caused by mobility renders a QoS model incapable of meeting delivery requirements. Finally, we analyze the effect of mobility on the distribution of end-to-end latencies. Traditionally, reactive protocols are criticized for buffering during the building of routes, however we also study buffering phenomenon caused by the proactive mechanisms of OLSR.