Flexible Multi-Thread Dynamic Bandwidth Allocation Algorithm in VPONs Based on LR WDM/TDM PON

With the smooth upgrade of the access network, multiple tuning-time devices will coexist in the long-reach access network, and the subsequent problems of high round-trip time (RTT) and optical network unit (ONU) tuning delay need to be solved urgently. In this paper, a multi-thread multiple tuning-time devices coexistence (MT-MTDC) bandwidth allocation algorithm is proposed. This algorithm can solve the problems of high RTT and ONU tuning delay in virtual passive optical network (VPON) based on long-reach wavelength division multiplexing/time division multiplexing passive optical network (LR WDM/TDM PON). Firstly, Multi-threaded polling mechanism is introduced into multi-mode coexistence VPON. Next, the number of wavelengths and threads is selected adaptively to ensure high bandwidth utilization. Then, the mechanism of dynamically adjusting the thread window is proposed. The mechanism strengthens the collaboration ability between threads and solves the degradation problem of the multi-thread algorithm. Furthermore, the construction of tuning buffer and the setting of time flag effectively solve the problem of more frequent ONU tuning pressure and ONU transmission conflict caused by multi-threaded polling algorithm. Finally, by comparing with the multi-thread longest-first first-available (MT-LFFA) algorithm and the multi-tuning-time ONU scheduling (MOS) algorithm, the proposed algorithm demonstrates its effectiveness in terms of polling cycle time, average tuning delay, bandwidth utilization and average packet delay.