HLA-Transparent Distributed Simulation of Agent-based Systems

Applied mathematic

The IEEE802.16d Fixed WMAN – a definitive description of the network to be simulated

The purpose of this document is to understand the details of the IEEE 802.16d, or fixed WMAN standard. Specifically to understand the air interface and the general architecture of the protocol in order to represent these as accurately as needed in a simulation. The various assumptions that are needed to abstract the system are given in the conclusion

Modelling Internet Workloads for IEEE 802.16

The IEEE 802.16-2004 standard contains the wireless MAN (WMAN) air interface specification. WMAN has become a major part of the emerging broadband wireless access technology particularly since it accounts for differentiated traffic classes (TCs). Differentiated traffic is immediately associated with Quality of Service (QoS) and this then becomes the objective of many WMAN studies. Since it is unrealistic to experiment with a real WMAN, the obvious alternative is to model its performance. Our objective is thus to develop a WMAN Base Station (BS) and Subscriber Station (SS) simulation model operating in the point-to-multipoint (PMP) architecture mode. As important as the simulation itself is a model representing the load or traffic. In this document we report on an IEEE 802.16 synthetic Workload Model (WLM) with a WLM Generator (WLG) and associated generators (TGs) that represent and generate internet traffic. Underlying the WLM is a Markov Modulated Arrival Process (MMBP) to combine the various WLGs

Ontology-based specification of simulation sequences

The specification of a simulation model includes the description of the input sequences while the simulation output can be described by the produced sequences. The input sequences describe the characteristics of the simulated scenarios and are to be chosen in a way to preserve the real system representativeness; while the output sequences can be used as a proof of such representativeness. Producing the appropriate input sequences and validating the output sequences against the model specification is therefore fundamental to the validation of the simulation model. In this paper, we propose an ontology-based specification of simulation input sequences. The ontology gives a methodology to formalize the sequence specification and output sequence validation by providing the semantic basis for the sequences formal description. In the model specification, the input sequences are described in terms of ontology concepts and properties values, and in the model implementation the deployed sequences can be thus automatically derived by mapping them on the ontology concepts. Sequence validation may be carried out by establishing the congruence between the ontology concepts and the deployed sequences

Software technologies for the interoperability, reusability and adaptability of distributed simulators

Giving interoperability and reusability capabilities to distributed simulators is fundamental to the widespread use of distributed simulation. The HLA standard has introduced considerable improvements with respect to previous standards, though it suffers from shortcomings such as (1) lack of interoperability among different IEEE-compliant implementations, (2) no support to the adaptation and integration of individual federates and (3) poor reusability, which is limited to entire federates only. In this paper, we present two independent technologies that overcome such shortcomings. The first technology consists of a CORBA-HLA architecture that overcomes limitation (1), the second technology is a new development framework called SimJ that overcomes limitations (2) and (3). The CORBA-HLA architecture decouples federates from the specific HLA implementation so that federates can be effortlessly run on top of any HLA implementation that exposes services through an IEEE-complaint IDL interface. The SimJ framework eases the development of individual federates by providing a uniform and standard interface for local and distributed simulators, and makes it possible the reuse of components smaller than entire federates in both local and distributed simulators

SimJ: a framework to develop distributed simulators

A distributed simulation (DS) is based on the use of several simulators distributed over a network infrastructure. Existing DS standards (e.g., HLA) only specify distribution services without giving support for developing individual simulators in a way to be compliant to the given standard. Traditionally, the development of individual simulators was facilitated by use of simulation languages (e.g., Csim, Arena, Extend, Modline, etc.) which however do not provide support to obtain interaction according to a given DS standard. The extension of such languages to include DS support is very problematic, especially in case of proprietary languages. For these reasons, the development of DS-compliant individual simulators is mostly done by use of standard programming languages (e.g., C, Java, etc.) with the additional effort of developing simulation mechanisms, model components and interfaces to the DS standard. This paper introduces SimJ, a Java library that minimizes such efforts, so that simulators can be developed as to be run on a single local host and can then be partitioned to be run over a set of networked hosts according to a given DS standard. The simulators SimJ addresses are discrete-event simulators (DES) and are easily portable to different DS standards. The paper illustrates the design guidelines of SimJ and presents an example use based on the HLA DS standard

Chapter HLA-Transparent Distributed Simulation of Agent-based Systems

Applied mathematic