An algorithm for reduction of packet delay and waiting time for unstable ONUs in PON

Abstract

Passive optical network (PON) is a highly dynamic access network that effectively converges several service providers. In a time cycle, some optical network units (ONUs) of a PON may miss the usual polling instant. In that case, the ONUs those miss the usual polling instants are called unstable ONUs. According to the existing early dynamic bandwidth allocation (E-DBA) algorithm, once an ONU miss the usual polling instant it needs to be waited until the end of upstream transmissions from the entire stable ONUs in the PON. That is why, the unstable ONUs suffers from more waiting time than the stable ONUs of a PON. This paper proposes a new DBA algorithm called modified E-DBA (ME-DBA) algorithm, for reduction of waiting times of the unstable ONUs in the PON. In the proposed ME-DBA algorithm, total ONUs in a PON are divided into several small groups. The data packets from all the stable ONUs of a group are transmitted 1st and then the data packets from the unstable ONUs of that group are transmitted. We have analyzed and compared the performance of the proposed ME-DBA algorithm with the existing E-DBA algorithm in terms of the average packet delay and waiting time of the unstable ONUs by using computer simulations. The simulation results show that the proposed algorithm provides lower end-to-end packet delay and waiting time for the unstable ONUs than that of the existing E-DBA algorithm.