# Exploring a New Adaptive Routing Based on the Dijkstra Algorithm in Optical Networks-on-Chip
## 3 Adaptive Power Control of ONoCs Based on the Dijkstra Algorithm
### Network Architecture
The average output power of the transmitter in network links is \(\overline{P}_{T(x,y)}\) and the formula is shown in (26). \(M\) and \(N\) represent network sizes, and \((x,y)\) represents the location of source node in network link. \(P_{T(x,y)}\) represents the output power required by the optical transmitter of the source node in a network link. \[\overline{P}_{T(x,y)}=\frac{\sum_{y=1}^{M}\sum_{x=1}^{N}P_{T(x,y)}}{M\times N} \tag{26}\]

Figure 8 shows the average output power of the optical transmitter under traditional power control, adaptive power control, and optimized power control when the network sizes are \(5\times 5\), \(6\times 6\), \(7\times 7\), and \(8\times 8\). The transmission losses caused by increasing the numbers of optical switch devices and waveguides constitute the main reason that the output power of the transmitter increases with the expansion of the network. From Figure 8, it can be concluded that the average output power of the transmitter under the traditional power control is the highest, followed by the adaptive power control, and the optimized power control has the lowest output power. Hence, the optimized power control could realize the minimum output power of transmitter of links. End-to-end (ETE) delay and throughput are important indicators for evaluating network performance. We constructed a simulation of an optimized network and a traditional network with the aid of OPNET simulation software, which is based on discrete event scheduling works. In order to better analyze the network performance under different network sizes, we implemented four network sizes for analysis: \(5\times 5\), \(6\times 6\), \(7\times 7\), and \(8\times 8\). Figure 7: The average reduction of link transmission loss in \(M\times N\) mesh-based ONoCs. Figure 9 demonstrates that when the packet size is 1024 bits, the ETE-delay of the traditional network is a bit lower than that in the optimized network. What is more, with the expansion of network sizes, network congestion is serious, resulting in the vastly increasing ETE-delay. When the network size is \(5\times 5\), \(6\times 6\), \(7\times 7\), or \(8\times 8\), the offered loads for the traditional network and optimized network reach saturation--0.1, 0.08, 0.06, and 0.04 respectively. ### Network Performance Evaluation

It is shown for the network throughput in Figure 10. Under the same load, the network based on the Dijkstra algorithm has almost the same throughput compared with the network based on the dimensional-order routing algorithm with the increasing of the network size. Furthermore, as the load is increasing, the throughput of the traditional network and the optimized network gradually increase to saturation. Figure 8: The average output power of the optical transmitter in \(M\times N\) mesh-based ONoCs. Figure 9: The ETE-delay in \(M\times N\) mesh-based ONoCs. ## 5 Conclusions

In conclusion, a new adaptive routing algorithm based on the Dijkstra algorithm realizes the selection of routing path with minimum transmission loss in the paper. Taking mesh-based ONoCs as an example, the optimized path based on the Dijkstra algorithm can achieve the minimum link transmission loss, and the average link transmission loss is significantly reduced compared with the traditional dimensional routing path under different network sizes. At the same time, compared with the traditional power control and adaptive power control, the optimized power-control-based Dijkstra algorithm has a significant advantage in reducing power consumption. In terms of network performance, we verified the feasibility of this adaptive routing algorithm to realize the selection of minimum transmission loss routing path with the aid of simulation software. According to the simulation results, the ETE-delay of the optimized network is a little larger than that in the traditional network. Moreover, with the expansion of the network scale, the throughput was almost the same as that in the traditional network based on dimensional routing algorithm.