Design and evaluation of EPONs

Students: Swapnil Bhatia, Ehteshamul Haque, and Dmitri Garbuzov
Faculty: Radim Bartoš

An Ethernet Passive Optical Network (EPON) is a point-to-multipoint, bidirectional, high rate optical network for providing subscribers with access to the backbone WAN. The EPON link is shared by multiple users. Each user connects to the EPON link through a device known as an Optical Network Unit (ONU). Since the link is shared, scheduling of link use must be centrally arbitrated. This function is performed by a single special device called the Optical Line Terminator (OLT). The direction of communication from the ONUs to the OLT is known as upstream direction whereas the direction from the OLT to the ONUs is known as the downstream direction. The data rate in each direction is set to 1 Gbps by the IEEE EPON standard. Overall, the link exhibits a tree topology with the OLT at the root of the tree and the ONUs at the leaves. The EPON link is shared by all users in the upstream direction and is divided into discrete time slots. When ONUs join the network, they must register themselves with the OLT through a Discovery protocol. After registration, the OLT schedules which ONU is allowed to transmit data and for how many time slots. Appended to the data traffic, the ONU transmits a control message containing a report of the number of bytes buffered in its queue, waiting for a transmission opportunity. Using these reports, the OLT is free to come up with a schedule that maximizes throughput, link utilization and minimizes the delay experienced by user traffic. We have characterized the performance of the IEEE Discovery scheme and designed and investigated the performance of dynamic bandwidth allocation schemes for EPONs.

This project is a part of our broader effort on the design and evaluation of access networks.

Peer-reviewed publications:

  • S. Bhatia and R. Bartoš ``IPACT with Smallest Available Report First: A New DBA Algorithm for EPON,'' in the Proc. of the IEEE International Conference on Communications 2007 (ICC 2007) , Glasgow, Scotland, June 24-28, 2007. [PDF 178K]
  • S. Bhatia, D. Garbuzov and R. Bartoš ``Analysis of the Gated IPACT scheme for EPONs,'' in the Proc. of the IEEE International Conference on Communications 2006 (ICC 2006) , Istanbul, Turkey, 2006. [PDF 1.2M]
  • S. Bhatia ``Design of DBA Algorithms for EPONs,'' (abstract) in the Proc. of the IEEE INFOCOM 2006 Students Workshop, , Barcelona, Spain, April 2006. [PDF 40K]
  • S. Bhatia, and R. Bartoš, ``Closed-form expression for the collision probability in the IEEE Ethernet Passive Optical Network registration scheme,'' Journal of Optical Networking, Vol. 5, No. 1, pp. 1-14, Jan. 2006. [ Journal Website, preliminary version (PDF 383k) presented at IEEE Globecom 2005]
  • S. Bhatia, and R. Bartoš, ``Performance of the IEEE 802.3 Registration Scheme Under High Load,'' in Proc. of the SPIE Optics East Conference (ITCom 2004) on Performance, Quality of Service, and Control of Next Generation Communication Networks II, Philadelphia, USA, Oct. 2004. [PDF 166K]

Support:

The project was funded in part in part by two grants from the Cisco University Research Program.