New ranging algorithm for pre-assigned equalization delay in ATM-PON system

Abstract

The optical fiber access network is expected as the most attractive solution to provide multimedia services in the future. Access systems using ATM-PON technology will make it possible to provide faster service at lower cost in the near future. In ATM-PON system using Time Division Multiplexing Access (TDMA) for upstream traffic, Each ONU has to process to upstream data in such a way that optical signal collisions are prevented. This can be done by placing all ONUs at the same virtual distance from the OLT. The procedure of measuring the distance and placing all ONUs at the same virtual distance is called as ranging. In the ITU-T/FSAN, a full digital in-band based ranging method should be used in PON systems to measure the logical reach distances between each ONU and the OLT. However. This method has a drawback. An ONU transmits ranging cells while other ONU(s) do not transmit data signals on the same channel in order to avoid collisions in warm-PON system. Although pre-assigned equalization delay ($T_e$) is referred as its solution, there is no way how to assign equalization delay. Therefore, we propose the two ranging algorithms for acquiring pre-assigned equalization delay that can reduce window size. The proposed algorithms can be automatically performed under the control of the OLT. Corresponding Serial Number Mask algorithm, one of the proposed algorithms is that the grouped ONUs correspond to branches of a splitter with specific serial number mask. And, we also propose Controllable Coarse Ranging algorithm using low power low frequency signal, which prevent collision of upstream data traffic. These two new algorithms can be applied in case of not only the serial number of the ONU is registered at the OLT (Method A) but also the serial number of the ONU is not registered at the OLT (Method B) during ranging procedure. Especially, at Method B, Corresponding SN Mask algorithm can prevent a Controllable Coarse Ranging method using coarse ranging signal f...