Batch scheduling algorithm for SUCCESS WDM-PON

In this paper we study the problem of scheduling variable-length frames in WDM-PON under Stanford University aCCESS (SUCCESS), a next-generation hybrid WDM/TDM optical access network architecture. The SUCCESS WDM-PON architecture has unique features that have direct impact on the design of scheduling algorithms: First, tunable transmitters and receivers at OLT are shared by ONUs to reduce transceiver counts; Second, the tunable transmitters not only generate downstream data traffic but also provide ONUs with optical Continuous Wave (CW) bursts for upstream transmissions. To provide efficient bidirectional transmissions between OLT and ONUs, we propose a batch scheduling algorithm based on the sequential scheduling algorithm previously studied. The key idea is to provide room for optimization and priority queueing by scheduling over more than one frame. In the batch scheduling, frames arrived at OLT during a batch period are stored in Virtual Output Queues (VOQs) and scheduled at the end of the batch period. Through simulation with various configurations, we demonstrate that the proposed batch scheduling algorithm, compared to the original sequential scheduling algorithm, provides higher throughput, especially when the system load is high, and better fairness between up- and downstream transmissions.