Low-Latency Dynamic Bandwidth Allocation for 100 km Long-Reach EPONs

Abstract

We propose a new dynamic bandwidth allocation (DBA) method for long-reach passive optical networks that can reduce the upstream latency. With this method, an optical line terminal allocates bandwidth to long-distance (up to 100 km) optical network units (ONUs) with a transmission request prediction and reduces the latency of the long-distance ONUs. This has no influence on the latency of short-distance ONUs even if they coexist with long-distance ONUs. The results of real machine experiments show that this new DBA method achieves a smaller latency with long-distance ONUs than the conventional DBA technique, and that there is no influence on short-distance ONUs. The latency time and jitter are kept below 1300 µs and 1000 µs, respectively, for both long-and short-distance ONUs. The experimental results also reveal the effect of the proposed method on bandwidth utilization efficiency and fairness. The degradation in bandwidth utilization efficiency when one long-distance ONU is added is small (0.3%), and the fairness index degradation is negligible (less than 0.1%), when the parameters are optimized. These results indicate the validity of the proposed DBA method.

PID Controller Based on a Self-Adaptive Neural Network to Ensure QoS Bandwidth Requirements in Passive Optical Networks

“…To design the neural network that tunes the controller we apply one alternative formula for the control signal of the PID in the discrete time. This expression is represented in equation (2), where Kp is the proportional constant, Ki is the integral constant and Kd is the derivative constant. In this way, the tuning parameters using neural networks will be Kp, Ki and Kd.…”

“…The superscripts in the different equations (1, 2, 3) are associated with the layer, that is, input, hidden and output layer. Moreover, the superscript of the weights refers to weights between two layers, for example (1,2) ij w correspond to the weights between the input and the hidden layer.…”

“…i Ok follow equation ( 5) and (6). In this equations, (1,2) ij w are the weights between the input layer and the hidden layer. As it was said before, the sigmoid function (with positive and negative symmetry) is chosen as the activation function for this layer ( ) tanh( )…”

“…Finally, with these expressions we can simplify the formula for the weighted factors (2,3) () li wk  of the output layer, as it is shown in (equation ( 13)).…”

“…As a consequence, a MAC (Medium Access Control) protocol is required to manage data collisions of different users (ONUs). Dynamic Bandwidth Allocation (DBA) algorithms, based on the TDMA (Time Division Multiple Access) protocol, is the most extended option, as they dynamically distribute the available bandwidth depending on the real time bandwidth demand or the Quality of Service (QoS) requirements contracted by end users [2][3][4][5][6][7][8][9]. On the other hand, the connectivity in the downstream channel (from the OLT to the ONUs) is pointto-point so the optical splitter (Fig.…”