Next Generation Ethernet Access Networks: GPON vs. EPON T. ORPHANOUDAKIS 1 , H.-C. LELIGOU 2 , J. D. ANGELOPOULOS 2 1: University of Peloponnese, Karaiskaki str., 22100, Tripolis, Greece 2: National Technical University of Athens, Heroon Poloytechneiou 9, Zographou Campus, Athens, Greece Abstract: Recently both ITU and IEEE have standardized solutions for Passive Optical Networks operating at gigabit per second line rates and optimized for the transport of packet-based traffic to improve the efficiency of previously standardized broadband PONs, which were based on ATM. The efficiency and performance of PON systems, depends mainly on the implemented medium access protocol. The latter is not part of the standards and left to the implementer, however the standards describe a set of control fields that constitute the tool-set for the MAC operation. In this paper we compare the efficiency and performance of the two systems under as close as possible MAC. Key-Words: - Passive Optical Networks, Broadband Access Networks, MAC protocol, Last mile 1. Introduction In response to the steadily increasing demand for bandwidth and networking services for residential users as well as enterprise customers, Passive Optical Networks (PONs) have emerged as a promising access technology that offers flexibility, broad area coverage, and cost-effective sharing of the expensive optical links compared to the conventional point-to-point transport solutions. In addition, they inherently concentrate traffic and greatly reduce the number of input ports in the access multiplexer, both important for the cost-sensitive residential access market. Due to these advantages, PONs have generated during the last decade substantial commercial activity also reflected in the work of several standardization bodies. Since the initial standardization of ATM-based PONs (APONs or alternatively named in ITU-T G.983.1 standard [1] Broadband PONs - BPONs) newer standards support multi-gigabit rates and better adapt to the packet-based Internet applications. In January 2003, the GPON (Gigabit PON) standards were ratified by ITU-T and were included in the G.984.x series of ITU-T Recommendations ([2], [3]). Driven by a closed group of worldwide system vendors and national telecom operators, they are designed to support a mix of TDM, ATM and packet based services, reaching symmetrical transmission rates of up to 1.244Gbps or 2.488Gbps At the same time IEEE, through the activities of Ethernet in the First Mile (EFM) 802.3ah group, has standardized a Gigabit Ethernet-friendly technology ([4]) called Ethernet PON (EPON), with the objective to leverage the great success of Ethernet as a LAN technology and exploit the economies of scale that the dominance of Ethernet has generated. Although PONs can achieve economical deployment and operation, which are a major concern to operators and service providers, high and fair resource utilization is equally important. Due to the multiple access nature of PONs in the upstream direction, the performance of a PON in terms of delay, delay variation and throughput strongly depends on the upstream bandwidth allocation function of the Medium Access Controller (MAC) residing at the Optical Line Termination (OLT). In the following section we discuss the details of the TDMA based operation of the MAC protocol in each case, identify the critical parameters of each technology that affects performance and derive relevant measures used in our simulations for comparison and collection of quantitative performance results that we present in the last section. 7th WSEAS Int. Conf. on Electronics, Hardware, Wireless and Optical Communications, Cambridge, UK, February 20-22, 2008 ISSN: 1790-5117 Page 122 ISBN: 978-960-6766-40-4