8
DYNAMIC BANDWIDTH ALLOCATION IN EPON AND GPON
8.1 INTRODUCTION
Dynamic bandwidth allocation (DBA) in passive optical networks (PON) presents a key issue for providing efficient and fair utilization of the PON upstream bandwidth while supporting the quality of service (QoS) requirements for different traffic classes. A PON consists of an optical line terminal (OLT) located at the provider central office and a number of optical network units (ONUs) or optical network terminals (ONTs) at the customer premises. In time-division multiplexing (TDM), PON downstream traffic is handled by broadcasts from the OLT to all connected ONUs, while in the upstream direction an arbitration mechanism is required so that only a single ONU is allowed to transmit data at a given point in time because of the shared upstream channel (see Figure 8.1). The start time and length of a transmission timeslot for each ONU are scheduled using a bandwidth allocation scheme. A merit of TDM-PON is the possibility to exploit the statistical multiplexing of network traffic in access networks by oversubscribing the shared optical distribution network in order to achieve high network utilization. A prerequisite for exploiting these multiplexing gains in the upstream is a well-designed and efficient DBA algorithm.
Figure 8.1. Schematic view of TDM-PON.
In this chapter we present an overview of DBA schemes for the two major standards for TDM-PON, namely, ...
