Dynamically Changing the Data Transmission Sequence of ONUs to Enhance the QoSs in PON Systems

In the existing passive optical network (PON), the occupying time-slot by optical network units (ONUs) for upstream data transmission is followed first-in first-out (FIFO) basis. Sometimes a heavily loaded ONU needs to wait for data transmission up to the end of its previous ONUs data transmission, where there is lightly loaded ONUs in behind. That is quit unfair where lightly loaded ONUs send its upstream data before heavily loaded ONUs only because of pursue of FIFO technique. Meanwhile, the heavily loaded ONUs in a time cycle is always vulnerable for full of buffer size and exacerbate the packet loss possibility. In our proposed scheme, we concentrate to priorities the ONUs based on the buffer occupancy. Data transmission sequence of ONUs is changed based on the Report message size and traffic incoming status. Occupying time slot of ONUs to transmit data is exactly followed the sorted output sequence. The great favor of proposed scheme is that the data transmission sequence of ONUs is not fixed. Hence, in every time cycle, waiting time to transmit data for heavily loaded ONUs is reduced significantly. Obtained simulated results strongly confirm that, cycle time utilization ratio is significantly increased, whereas buffering delay and probability of packet loss of heavily loaded ONUs is reduced compared to the conventional scheme.