Multi-Thread Polling: A Dynamic Bandwidth Distribution Scheme in Long-Reach PON

With the development of optical technology, the span of a broadband access network using passive optical network (PON) technology can be increased from today's standard of 20 km to 100 km or higher. As a result, we have the long-reach (LR) PON which not only has extended reach, but which can also support a large base of users by employing wavelength-division multiplexing (WDM) for its data transmissions. However, a major challenge in the LR-PON is that the propagation delay (for data as well as control signals) between the telecom central office (CO) and the end user is increased by a very significant amount. Now, traditional PON algorithms for scheduling the upstream transmission, such as dynamic bandwidth allocation (DBA) algorithms, may not be sufficient; actually, they may lead to degraded performance because of the long delay of the "control loop" between the CO and the users. This challenge motivates us to investigate a multi-thread polling algorithm to distribute the upstream bandwidth dynamically in the LR-PON. In this study, we analyze key parameters of the algorithm, such as initiating and tuning multiple threads. We then demonstrate the algorithm's advantage to decrease the average packet delay under varying offered loads.