Analysis of Modulation Order to Guarantee Real-Time Service Throughputs in OFDMA-PON

In an orthogonal frequency-division multiple access passive optical network (OFDMA-PON), each optical network unit (ONU) chooses a modulation format based on the signal-to-noise ratio (SNR) at its receiver. An ONU with a high SNR can use a high-order modulation format to increase its transmission efficiency. When upstream resources are fully utilized, this increases an aggregated upstream throughput by ONUs, but the throughput is varied by ONUs' modulation orders. To guarantee upstream throughputs of real-time services, we first estimate the network throughout in a case that a total upstream resource is fully and fairly distributed to ONUs. By using the estimation, then, we present the lowest order of available modulation formats for the throughput guarantee. We investigate how the modulation order affects the number of ONUs that can be serviced in the OFDMA-PON.