# Traffic-Based Heuristics for Regenerator Placement in Translucent Dynamic Optical Networks
## 5 Simulation Setup  
We use two topologies to evaluate the performance of the RPP algorithms: CoreNet (75 nodes and 99 bi-directional links) [32] and EuroNet (28 nodes and 41 bidirectional links) [33], both with 96 wavelengths per link, each transmitting 100 Gb/s PDM-QPSK. In the simulations, the transmission rate only affects the MOR and, unless stated otherwise, it is used the same values for 100 Gb/s adopted by [PERSON] [2]: \(T_{R}=2000\) km, and \(\epsilon=60\) km. However, we have also investigated the cases for \(T_{R}=1600\) km, \(\epsilon=60\) km and \(T_{R}\ =\ 2400\) km, \(\epsilon=60\) km to validate the effectiveness of the proposed method under different transmission reaches. Uniform traffic (UT) and non-uniform traffic (nUT) are considered during simulations. Under uniform traffic, \(\omega_{ij}=L/(N\cdot(N-1))\) and under non-uniform traffic,\(\omega_{ij}=(\sigma_{ij}\cdot a\cdot L)/(N\cdot(N-1))\). The \(\sigma_{ij}\) is a random number uniformly distributed on the interval \([0.5;2.5]\) and the constant \(a\) is such that: \(a=(N\cdot(N-1))/(\sum_{i=1}^{N}\sum_{j=1}^{N}\sigma_{ij})\). The random \(\sigma_{ij}\in[0.5;2.5]\) means that the load between the nodes \(i\) and \(j\) for nUT traffic may vary from 50% to 250% of the load for the same pair under UT traffic, maintaining; however, the same total network load for both traffics. There are two approaches mentioned in the literature and used in the industry to perform 3R in optical networks: (1) a shared pool of regenerators per node [1; 2; 11]; (2) the use of not assigned (i.e., free) add-drop interfaces to perform back-to-back regeneration [23]. In this paper, we assume that there is a pool of shared devices in each node exclusively dedicated to providing 3R capability and they can perform both wavelength conversion and signal regeneration. The node architecture assumed in this paper is shown in Figure 1. It is composed by a colorless/directionless/contentionless (CDC) ROADM, de/multiplexers, add/drop interfaces, and a shared bank of 3R regenerators. Using this architecture, it is possible to decide, by using the ROADM switch fabric, whether the optical signal should be added/dropped, be bypassed, or undergo to the 3R shared bank to be regenerated. The node shown in Figure 1 supports a pair of fibers in each direction, the fibers arriving at the node are connected to ROADM switching fabric through the DEMUXes, whereas the fibers leaving the node are connected via MUXes. For example, signals from a client/user connected to a network node can be transmitted (or received) by accessing the \"Add/Drop interfaces\" block (bottom left in the figure). Then, they can be optically switched by ROADM to one of its outputs (or inputs), connected to a MUX (or DEMUX), until the signal may reach one of the output (or input) fibers of the node. On the other hand, an optical signal that is being transmitted along with the network and that arrives at a node (via fiber + DEMUX input) can be switched to an output port (via fiber + MUX output), or it can undergo electronic regeneration, being switched by the ROADM to the shared 3R regenerator bank (bottom right in the figure). In this case, the signal is regenerated by one of the 3R regenerators available in the bank and then inserted again into one of the input ports of the ROADM to be forwarded to one of the output fibers (fiber + MUX). The call requests are generated under a Poisson stochastic process in which the call duration follows an exponential distribution. Upon a call request, the shortest path (in terms of distance) from the source to the destination node is found using [PERSON]'s algorithm (we also investigated some cases using the k-shortest path routing algorithm as discussed in Section 6). The route is then segmented into TSs using the same RA used in [4] considering the MOR instead of OSNR as the QoT criterion.