Evaluating Communication Architectures

1. CACTUS Communication Scenario Manager: Evaluating Communication Architectures Jan de Jongh, TNO Telecom, J.F.C.M.DeJongh@FEL.TNO.NL, http://www.telecom.tno.nl Context Over the past decade, a large number of novel communication paradigms have emerged. Many of these, such as WLAN-based ad hoc networks, hotspot-centered networks, and meshed networks, are attractive alternatives to future 3G-networks, such as based upon UMTS. Attractive in the sense that such networks can be cheaper and provide higher bandwidth. The price to be paid is twofold: (1) WLANs operate in license-free frequency bands and there is virtually no protection against interference from other applications in the same frequency band; (2) there are severe restrictions on the transmission power and, as a result, the transmission range is usually limited to a few hundred meters at best. Obviously, these two constraints on WLAN-based networks severely degrade their reliability. However, their availability introduces interesting economical and technical trade-offs in the design of a communication architecture for present and future services to mobile users. Within the context of the Freeband-Impulse CACTUS (Context Aware Communication, Terminal and User) project, we therefore designed and realized a suite of software tools for the design and evaluation of communication and information architectures. • Features • The scenario-manager software consists of an extensible suite of Java tools, several example scenarios, and the following modules: • Graphical Core • The graphical core of the scenario manager deals with user-defined symbols and timed events that operate on these symbols. A symbol can either be created by canonical vectorized symbols (triangles, polygons, rectangles, ellipses, etc.), or read from a file containing a bitmapped image (e.g., a background map). An interesting feature of the graphical core is the ability to define symbols with a finite state machine, e.g., • Mobility Models • The Mobility module features the definition of nodes and their mobility. Numerous stochastic models are available, all waypoint-based, such as Random Waypoint, Reference-Point Group Mobility, Ornstein-Uhlenbeck, Wiener, Gauss-Markov, etc. • Link-Availability Models • The LinkAvailability module features link-availability models that describe when nodes, depending on their distance and, for instance, obstruction data, are able to communicate. The model also supports micro-cellular models. In such models the topology of the network is largely determined by creating, splitting, and merging groups of nodes. Such models are applicable to, for instance, the CACTUS scenario. • Traffic Models • The Traffic module features the definition of messages and message exchanges between nodes. Several stochastic models are available for, e.g., the message length and message inter-arrival time. • Information Storage and Retrieval • The Information module features the placement of databases, mechanisms such as caching, replication, and synchronization, and performance measures such as information timeliness, accuracy, and completeness. • Objectives • The communication scenario manager was designed with the following objectives in mind: • to gain insight into the communication aspects of a mobile information and/or entertainment system; • to study feasibility of and trade-offs in using/deploying a communication infrastructure; • to study feasibility of and trade-offs in the information architecture (e.g., the locations of databases, the use of caching, replication, and synchronization, and their joint effects on information timeliness, accuracy, and completeness); • to not study these aforementioned trade-offs in isolation, but to stay in the problem domain. J. de Jongh v03 20030822 • Applications • The scenario manager can be employed in many different problem domains. This is best illustrated by the three predefined scenarios: • CACTUS: a scenario of tourists visiting a city and exchanging multimedia content; • a Traffic and Control scenario; • a military scenario.