Gerstlauer, Andreas:
Simulation verschiedener Permit-Zuweisungsverfahren in einem ATM-Zugangsnetz
1st Semster Project Thesis (1. Studienarbeit), Dept. of Electrical Engineering, University of Stuttgart, Germany, 1994.


In these times we are witnessing an increasing development towards an information society, including a trend to integrate new services with even higher requirements in the area of public communication. To meet these demands a broadband integrated services digital network (B-ISDN) based on the asynchronous transfer mode (ATM) using optical fibers is about to be introduced.

But especially residential customers for whom cost is also a major factor won't permanently need the full capacity. Therefore, european researchers are working on a project to develop an access network where the customers are connected to a passive optical tree, sharing the existing components and the available bandwidth.

The fact that a customer doesn't know when another customer is sending poses a special problem to the realization of the media access protocol. To avoid collisions a central arbiter generates so-called `permits' granting access to a time slot. Of central importance in this protocol is the algorithm distributing the permits among the customers requesting the permission to send.

The goal of this work was to investigate the performance of the three algorithms being proposed (Global FIFO, Dynamic Allocation, Queue Length). Therefore, an existing simulation program for the access network was extended to include the missing algorithms. With the results of the simulations for different traffic scenarios the alternatives were then judged and compared.

It turned out that both, the Queue Length and the Dynamic Allocation algorithms already have conceptional weaknesses in their specifications. However, even when looking at parameters like loss, delay and delay variation, the Global FIFO algorithm generally achieves the better performance.

Andreas Gerstlauer <>
Center for Embedded Computer Systems
University of California, Irvine CA 92697-2625, USA
Last modified: 12 Jan 1998