EPON

The Broadband Passive Optical Network (PON) technology is a promising approach to establish a cost-effective access network. It is intended to provide a simple, low cost, scalable solution capable of delivering broadband access to end users, by passively sharing a single optical fiber transmission system between several packets. While downstream traffic is broadcast to all packets, the access of upstream traffic to the fiber has to be arbitrated in order to avoid collisions. This arbitration mechanism and more generally, bandwidth distribution and QoS Provisioning, have been left to the implementer. Interleaved Polling with Adaptive Cycle Time (IPACT) is one of the earliest proposed schemes for bandwidth distribution in Ethernet PON (EPON) and has been extensively used as a benchmark by many subsequent allocation schemes. In this paper, we propose an analytical model which yields approximate values for mean queue length and mean packet delay in an EPON with the Gated IPACT scheme under the assumption of Poisson arrivals. We show by simulation that the model is remarkably accurate over the whole load range. We use the model to demonstrate that all ONUs experiment performance degradation in case of local overload by some ONUs, thus showing the necessity of correcting somehow the Gated policy in order to avoid this phenomenon.

Στους διατυπωμένους στόχους της ΕΠΟΝ περιλαμβανόταν η υπεράσπιση των "εκπολιτιστικών και μορφωτικών δικαιωμάτων και επιδιώξεων" της νέας γενιάς. Έτσι, ως αποτέλεσμα σχεδιασμένης δράσης, σε πολλές περιοχές αναπτύχθηκε σημαντική πολιτιστική δραστηριότητα. Με πολιτική αφετηρία την "ανακήρυξη του λαού μόνου παράγοντα και φορέα ειρήνης και πολιτισμού", διερευνήθηκε σε θεωρητικό και πρακτικό επίπεδο "το κοινό σημείο όπου συναντιούνται η επιστημονική δραστηριότητα, η καλλιτεχνική έκφραση, η ηθική και πολιτική δράση".

Le mouvement résistant grec s'est révélé particulièrement important et dynamique sous deux aspects: la résistance armée du maquis d'une part et d'autre part la résistance civile. C'est de cette dernière que nous traiterons principalement, en prenant comme objet de notre étude un cas spécial en Grèce, la très massive organisation résistante de la jeunesse, l'EPON, créée en février 1943 .

We study the ability of low-rate Serially-Concatenated Low Density Generator Matrix (SCLDGM) codes to approach theoretical limits. Although two layer SCLDGM codes approach capacity for medium rates (0.25 <; R <; 0.9), they do not perform adequately for lower rates. In this case, substantial performance improvements are obtained using three layers.

... Hassan Naser Department of Software Engineering Lakehead University Thunder Bay, Ontario, Canada hnaser@lakeheadu.ca Hussein T. Mouftah School of Information Technology and Engineering University of Ottawa Ottawa, Ontario, Canada mouftah@site.uottawa.ca ...

Dynamic bandwidth allocation (DBA) schemes in Ethernet passive optical networks (EPONs) have been studied by several investigators. However, most of these schemes cannot provide efficient network utilization while supporting fair, deterministic service to end-users. In this letter, a novel OLT-based bandwidth allocation model is proposed that employs a credit pooling technique to partition the network bandwidth among different classes of service. High network utilization is achieved by embedding ONU scheduling decisions in time and by eliminating the channel idle-time overhead, associated with many earlier DBA schemes.