45508612
A unifying look at clustering in mobile ad hoc networks
In recent years, a significant number of clustering schemes have been proposed in the literature. Most of them treat cluster initialization and cluster maintenance differently as if they were two entirely different undertakings. The main contribution of this work is a unifying way of looking at clustering in MANET. We make an important point: there is no difference between cluster initialization and cluster maintenance, and one algorithm should gracefully blend into the other. To illustrate the feasibility of this concept, we propose a novel tree-based clustering algorithm for MANET based on a number of properties of diameter-2 graphs. The algorithm is cluster-centric and, unlike the vast majority of algorithms in the literature, works in the presence of node mobility. Extensive simulation results show the effectiveness of our algorithm when compared to other clustering schemes proposed in the recent literature. Copyright © 2004 John Wiley & Sons, Ltd.
11087297
Fairness in DQDB revisited: a new solution
The main contribution of this work is to a new way of looking at fairness in a DQDB system. Our scheme is very simple and efficient to implement and compares favorably with the leading rate-controlled schemes proposed in the literature. In addition, simulation results show that in the presence of non-uniform loads, such as a file server being brought up, our scheme converges rapidly to a fair steady state.<<ETX>>
9333297
A two-zone hybrid routing protocol for mobile ad hoc networks
Recently, an elegant routing protocol, the zone routing protocol (ZRP), was proposed to provide a hybrid routing framework that is locally proactive and globally reactive, with the goal of minimizing the sum of the proactive and reactive control overhead. The key idea of ZRP is that each node proactively advertises its link state over a fixed number of hops, called the zone radius. These local advertisements provide each node with an updated view of its routing zone - the collection of all nodes and links that are reachable within the zone radius. The nodes on the boundary of the routing zone are called peripheral nodes and play an important role in the reactive zone-based route discovery. The main contribution of this work is to propose a novel hybrid routing protocol - the two-zone routing protocol (TZRP) - as a nontrivial extension of ZRP. In contrast with the original ZRP where a single zone serves a dual purpose, TZRP aims to decouple the protocol's ability to adapt to traffic characteristics from its ability to adapt to mobility. In support of this goal, in TZRP each node maintains two zones: a crisp zone and a fuzzy zone. By adjusting the sizes of these two zones independently, a lower total routing control overhead can be achieved. Extensive simulation results show that TZRP is a general MANET routing framework that can balance the trade offs between various routing control overheads more effectively than ZRP in a wide range of network conditions.
42702929
A Fair Resource Allocation Protocol for Multimedia Wireless Networks
Wireless networks are expected to support real-time interactive multimedia traffic and must be able, therefore, to provide their users with quality-of-service (QoS) guarantees. Although the QoS provisioning problem arises in wireline networks as well, mobility of hosts and scarcity of bandwidth makes QoS provisioning a challenging task in wireless networks. It has been noticed that multimedia applications can tolerate and gracefully adapt to transient fluctuations in the QoS that they receive from the network. The additional flexibility afforded by the ability of multimedia applications to tolerate and adapt to transient changes in QoS can be exploited by protocol designers to significantly improve the overall performance of wireless systems. This paper presents a fair resource allocation protocol for multimedia wireless networks that uses a combination of bandwidth reservation and bandwidth borrowing to provide network users with QoS in terms of guaranteed bandwidth, call blocking, and call dropping probabilities. Our view of fairness was inspired by the well-known max-min fairness allocation protocol for wireline networks. Simulation results are presented that compare our protocol to similar schemes.
31459718
Sequential and Parallel Meta-Heuristics for Solving the Single Row Routing Problem
The design of multi-layer printed circuit boards is vital in the construction of complex electronic systems. Wire routing is a crucial step in the overall design process, which can be decomposed into a number of single row routing (SRR) problems. This paper proposes an approach to solve the SRR problem based on parallel meta-heuristics. The development of this technique involves the design of an encoding strategy that allows all possible routings to be uniquely represented and the derivation of cost functions that maximizes the quality of the developed solutions. Further, parallelization of the proposed approach is attempted to improve the computational efficiency. The different stages of the development are backed by experiments to show the pros and cons of the sequential and parallel implementations.
14933759
Classifying matrices separating rows and columns
The classification problem transforms a set of N numbers in such a way that none of the first N/2 numbers exceeds any of the last N/2 numbers. A comparator network that solves the classification problem on a set of r numbers is commonly called an r-classifier. We show how the well-known Leighton's Columnsort algorithm can be modified to solve the classification problem of N=rs numbers, with 1 /spl les/ s /spl les/ r, using an r-classifier instead of an r-sorting network. Overall, the r-classifier is used O(s) times, namely, the same number of times that Columnsort applies an r-sorter. A hardware implementation is proposed that runs in optimal O(s+logr) time and uses an O(rlogr(s + logr)) work. The implementation shows that, when N= rlogr, there is a classifier network solving the classification problem on N numbers in the same O(logr) time and using the same O(rlogr) comparators as an r-classifier, thus saying a logr factor in the number of comparators over an (rlogr)-classifier.
11519290
Linear Time Algorithms for Dominating Pairs in Asteroidal Triple-free Graphs
An independent set of three vertices is called an asteroidal triple if between each pair in the triple there exists a path that avoids the neighborhood of the third. A graph is asteroidal triple-free (AT-free) if it contains no asteroidal triple. The motivation for this investigation is provided, in part, by the fact that AT-free graphs offer a common generalization of interval, permutation, trapezoid, and cocomparability graphs. 
Previously, the authors have given an existential proof of the fact that every connected AT-free graph contains a dominating pair, that is, a pair of vertices such that every path joining them is a dominating set in the graph. The main contribution of this paper is a constructive proof of the existence of dominating pairs in connected AT-free graphs. The resulting simple algorithm, based on the well-known lexicographic breadth-first search, can be implemented to run in time linear in the size of the input, whereas the best algorithm previously known for this problem has complexity O(|V|3) for input graph G=(V,E). In addition, we indicate how our algorithm can be extended to find, in time linear in the size of the input, all dominating pairs in a connected AT-free graph with diameter greater than 3. A remarkable feature of the extended algorithm is that, even though there may be O(|V|2) dominating pairs, the algorithm can compute and represent them in linear time.
37000292
Wings and perfect graphs
Abstract An edge uv of a graph G is called a wing if there exists a chordless path with vertices u , v , x , y and edges uv , vx , xy . The wing-graph W ( G ) of a graph G is a graph having the same vertex set as G ; uv is an edge in W ( G ) if and only if uv is a wing in G . A graph G is saturated if G is isomorphic to W ( G ). A star-cutset in a graph G is a non-empty set of vertices such that G — C is disconnected and some vertex in C is adjacent to all the remaining vertices in C . V. Chvatal proposed to call a graph unbreakable if neither G nor its complement contain a star-cutset. We establish several properties of unbreakable graphs using the notions of wings and saturation. In particular, we obtain seven equivalent versions of the Strong Perfect Graph Conjecture.
18454010
A charming class of perfectly orderable graphs
Abstract We investigate the following conjecture of Vasek Chvatal: any weakly triangulated graph containing no induced path on five vertices is perfectly orderable. In the process we define a new polynomially recognizable class of perfectly orderable graphs called charming. We show that every weakly triangulated graph not containing as an induced subgraph a path on five vertices or the complement of a path on six vertices is charming.
9433006
No antitwins in minimal imperfect graphs
Abstract It is customary to call vertices x and y twins if every vertex distinct from x and y is adjacent either to both of them or to neither of them. By analogy, we shall call vertices x and y antitwins if every vertex distinct from x and y is adjacent to precisely one of them. Lovasz proved that no minimal imperfect graph has twins. The purpose of this note is to prove the analogous statement for antitwins.
33854490
On sources in comparability graphs, with applications
Abstract We characterize sources in comparability graphs and show that our result provides a unifying look at two recent results about interval graphs.