Scalable routing strategies for ad hoc wireless networks

We consider a large population of mobile stations that are interconnected by a multihop wireless network. The applications of this wireless infrastructure range from ad hoc networking (e.g., collaborative, distributed computing) to disaster recovery (e.g., fire, flood, earthquake), law enforcement (e.g., crowd control, search-and-rescue), and military (automated battlefield). Key characteristics of this system are the large number of users, their mobility, and the need to operate without the support of a fixed (wired or wireless) infrastructure. The last feature sets this system apart from existing cellular systems and in fact makes its design much more challenging. In this environment, we investigate routing strategies that scale well to large populations and can handle mobility. In addition, we address the need to support multimedia communications, with low latency requirements for interactive traffic and quality-of-service (QoS) support for real-time streams (voice/video). In the wireless routing area, several schemes have already been proposed and implemented (e.g., hierarchical routing, on-demand routing, etc.). We introduce two new schemes-fisheye state routing (FSR) and hierarchical state routing (HSR)-which offer some competitive advantages over the existing schemes. We compare the performance of existing and proposed schemes via simulation     

Evaluation of Underwater Optical-Acoustic Hybrid Network

The deployment of underwater networks allows researchers to collect explorative and monitoring data on underwater ecosystems.The acoustic medium has been widely adopted in current research and commercial uses,while the optical medium remains experimental only.According to our survey onthe properties of acoustic and optical communicationsand preliminary simulation results have shown significant trade-offs between bandwidth,propagation delay,power consumption,and effective communication range.We propose a hybrid solution that combines the use of acoustic and optical communication in order to overcome the bandwidth limitation of the acoustic channel by enabling optical communicationwith the help of acoustic-assisted alignment between optical transmitters and receivers.     

Buzz-Net: A Hybrid Token/Random Access LAN

Buzz-net is a local network supported by a pair of unidirectional buses to which stations are connected via passive interfaces. The access protocol is a hybrid which combines random access and virtual token features. More precisely, the network operates in random access mode at light load and virtual token mode at heavy load. Because of the virtual token implementation, Buzz-net retains high efficiency even at very high bus speeds. Efficiency at high speeds and bus unidirectionality make Buzz-net particularly suitable for fiber optics media. This paper describes the protocol, develops approximate analytic models for performance evaluation, and compares Buzz-net performance results to those of other unidirectional bus schemes.     

Generated necessities and possibilities

A necessity measure is a function n from a Boolean algebra B to the real interval [0,1] such that n(x∧y) = min{n(x),n(y)} for every x,y ? B and n(0) = 0, n(1) = 1. Necessities are strictly related to Shafer's consonant belief functions and are basic tools when dealing with imprecision and uncertainty. In this article we propose a technique to generate necessities given a collection of items of information quantified by an initial valuation. the method we employ enables us to define conditional necessities in a very natural way and the composition of two necessities by a rule analogous to Dempster's rule. This is obtained by skipping the condition n(0) = 0 and therefore considering necessities with a nonzero “degree of inconsistency.” © 1992 John Wiley & Sons, Inc.     

Topology design and bandwidth allocation in ATM nets

The design of a P/S network embedded into a backbone facility network is discussed. The problem is formulated as a network optimization problem where a congestion measure based on the average packet delay is minimized, subject to capacity constraints posed by the underlying facility trunks. The variables in this problem are the routing on the express pipes (i.e. the channels that interconnect the P/S modes) and the allocation of bandwidth to such pipes. An efficient algorithm is presented for the solution of the above problem and it is applied to some representative examples. It is shown that for some test cases the congestion measure is substantially reduced with respect to the values obtained when the embedded topology is kept identical to the backbone topology. Dynamic reconfiguration schemes where the embedded topology is periodically adjusted to track the fluctuations in traffic requirements are discussed     

Mobility prediction and routing in ad hoc wireless networks

By exploiting non-random behaviors for the mobility patterns that mobile users exhibit, we can predict the future state of network topology and perform route reconstruction proactively in a timely manner. Moreover, by using the predicted information on the network topology, we can eliminate transmissions of control packets otherwise needed to reconstruct the route and thus reduce overhead. In this paper, we propose various schemes to improve routing protocol performances by using mobility prediction. We then evaluate the effectiveness of using mobility prediction via simulation. Copyright © 2001 John Wiley & Sons, Ltd.     

The design, implementation, and performance evaluation of theon-demand multicast routing protocol in multihop wireless networks

Multicasting has emerged as one of the most focused areas in the field of networking. As the technology and popularity of the Internet grow, applications such as video conferencing that require the multicast feature are becoming more widespread. Another interesting development has been the emergence of dynamically reconfigurable wireless ad hoc networks to interconnect mobile users for applications ranging from disaster recovery to distributed collaborative computing. In this article we describe the on-demand multicast routing protocol for mobile ad hoc networks. ODMRP is a mesh-based, rather than conventional tree-based, multicast scheme and uses a forwarding group concept (only a subset of nodes forwards the multicast packets packets via scoped flooding). It applies on-demand procedures to dynamically build routes and maintain multicast group membership. We also describe our implementation of the protocol in a real laptop testbed     

Tree multicast strategies in mobile,multihop wireless networks

Tree multicast is a well established concept in wired networks. Two versions, persource tree multicast (e.g., DVMRP) and shared tree multicast (e.g., Core Based Tree), account for the majority of the wireline implementations. In this paper, we extend the tree multicast concept to wireless, mobile, multihop networks for applications ranging from ad hoc networking to disaster recovery and battlefield. The main challenge in wireless, mobile networks is the rapidly changing environment. We address this issue in our design by: (a) using soft state (b) assigning different roles to nodes depending on their mobility (2level mobility model); (c) proposing an adaptive scheme which combines shared tree and persource tree benefits, and (d) dynamically relocating the shared tree Rendezvous Point (RP). A detailed wireless simulation model is used to evaluate various multicast schemes. The results show that persource trees perform better in heavy loads because of the more efficient traffic distribution; while shared trees are more robust to mobility and are more scalable to large network sizes. The adaptive tree multicast scheme, a hybrid between shared tree and persource tree, combines the advantages of both and performs consistently well across all load and mobility scenarios. The main contributions of this study are: the use of a 2level mobility model to improve the stability of the shared tree, the development of a hybrid, adaptive persource and shared tree scheme, and the dynamic relocation of the RP in the shared tree.     

Enhancing Transport Layer Capability in HAPS–Satellite Integrated Architecture

The use of HAPS/UAV to enhance telecommunication capabilities has been proposed as an effective solution to support hot spot communications in limited areas. To ensure communication capabilities even in case of emergency (earthquake, power blackout, chemical/nuclear disaster, terrorist attack), when terrestrial fixed and mobile infrastructures are damaged or become unavailable, the access to satellites represents a reliable solution with worldwide coverage, even though it may suffer from shadowing impairment, especially in an urban environment. In this paper we approach an innovative and more challenging architecture foreseeing HAPS/UAV connected to the satellite in order to enlarge coverage and to allow interconnection with very remote locations. In this scenario, we have analysed TCP-based applications proposing some innovative techniques, both at protocol and at architectural level, to improve performance. In particular, we propose the use of a PEP technique, namely splitting, to speed up window growth in spite of high latency, combined with TCP Westwood as a very efficient algorithm particularly suitable and well performing over satellite links.Cesare Roseti graduated cum laude in 2003 in Electronic Engineering at University of Rome “Tor Vergata”. In 2003 and 2004, he was a visiting student at Computer Science Department of University of California, Los Angeles (UCLA). Since 2004 he is a PhD student at the Electronic Engineering Department and his research interests include satellites communications and transport protocols in heterogeneous (wired/wireless) systems.Claudio Enrico Palazzi studied computer science at University of Bologna, Campus of Cesena. He has been a student representative in several bodies of University of Bologna and, in particular, from 2000 to 2001 he was part of the Board of Governors. In 2001, he received the Sigillum Magnum of Alma Mater Studiorum University of Bologna. He graduated cum laude in 2002 with a thesis on transport protocols in wireless environments. In 2003, he was the first student enrolled in the Interlink joint PhD program in computer science by which he is currently a PhD student in Computer Science at both University of Bologna and University of California, Los Angeles (UCLA). His research interests include protocol design, implementation and performance analysis for wired/wireless networks.Michele Luglio received the Laurea degree in electronic engineering from the University of Rome “Tor Vergata”. He received the PhD degree in telecommunications in 1994. From August to December 1992 he worked as visiting staff engineering at Microwave Technology and Systems Division of Comsat Laboratories (Clarksburg, Maryland, USA). He received the Young Scientist Award from ISSSE’95. Since October 1995, he is research and teaching assistant at University of Rome “Tor Vergata” where he works on designing satellite systems for multimedia services both mobile and fixed, in the frame of projects funded by EC, ESA and ASI. He taught signal theory and collaborated in teaching digital signal processing and elements of telecommunications. In 2001 and 2002 he was visiting professor at the Computer Science Department of University of California Los Angeles (UCLA) to teach Satellite Networks class. Now he teaches satellite telecommunications and signals and transmission. He is a member of IEEE.Mario Gerla received a graduate degree in engineering from the Politecnico di Milano in 1966, and the MS and PhD degrees in engineering from UCLA in 1970 and 1973, respectively. After working for Network Analysis Corporation from 1973 to 1976, he joined the Faculty of the Computer Science Department at UCLA where he is now professor. His research interests cover the performance evaluation, design and control of distributed computer communication systems; high-speed computer networks; wireless LANs; and ad hoc wireless networks. He has worked on the design, implementation and testing of various wireless ad hoc network protocols (channel access, clustering, routing and transport) within the DARPA WAMIS, GloMo projects. Currently, he is leading the ONR MINUTEMAN project at UCLA, and is designing a robust, scalable wireless ad hoc network architecture for unmanned intelligent agents in defense and homeland security scenarios. He is also conducting research on QoS routing, multicasting protocols and TCP transport for the Next-Generation Internet (see www.cs.ucla.edu/NRL for recent publications). He became IEEE Fellow in 2002.M. Yahya “Medy” Sanadidi was born in Damanhour, Egypt. He received his high school diploma from College Saint Marc, and his BSc in electrical engineering (computer and automatic control section) from the University of Alexandria, Egypt. Dr. Sanadidi received his PhD in computer science from UCLA in 1982. He is currently a research professor at the UCLA Computer Science Department. As co-principal investigator on NSF-sponsored research, he is leading research in modeling and evaluation of high-performance Internet protocols. He teaches undergraduate and graduate courses at UCLA on queuing systems and computer networks. Dr. Sanadidi was a manager and senior consulting engineer at Teradata/AT&T/NCR from 1991 to 1999 and led several groups responsible for performance modeling and analysis, operating systems, and parallel query optimization. From 1984 to 1991, he held the position of computer scientist at Citicorp, where he pursued R&D projects in wireless metropolitan area data communications and other networking technologies. In particular, between 1984 and 1987, he lead the design and prototyping of a wireless MAN for home banking and credit card verification applications. From 1981 to 1983, Dr. Sanadidi was an assistant professor at the Computer Science Department, University of Maryland, College Park, Maryland. There, he taught performance modeling, computer architecture and operating systems, and was principal investigator for NSA-sponsored research on global data communications networks. Dr. Sanadidi has consulted for industrial concerns, has co-authored conference as well as journal papers, and holds two patents in performance modeling. He participated as reviewer and as program committee member of professional conferences. His current research interests are focused on congestion control and adaptive multimedia streaming protocols in heterogeneous (wired/wireless) networks.James Stepanek received his BS in computer science from Harvey Mudd College in 1994 and his MS in computer science from University of California, Los Angeles (UCLA) in 2001 where he is currently enrolled in the PhD program. He is also currently a member of the technical staff in the Computer Systems Research Department of The Aerospace Corporation. His research interests include wireless and satellite networks.