# On Localized Countermeasure Against Reactive Jamming Attacks in Smart Grid Wireless Mesh Networks
## 5 Localized Trigger Identification Algorithm
### Trigger Nodes Detection Procedure
#### 5.2.2 Identification of a Single Trigger Node (ISTN) Algorithm
Because \(r=20\) and \(\alpha=\frac{R}{r}=3\) with \(J\in[1,10]\) are sufficient parameters to analyze the performance with a massive number of jammers over \(n=3000\) in Smart Grid wireless mesh networks, no more jammers over \(J=10\) are investigated. As the number of jammers swells up to 10 times the initial count, just 130 additional testing rounds are required from \(J=1\) with around 70 initial tests to \(J=10\) in _TNI-SGT_. Consequently, even with massive impact scenario against the wireless mesh networks from more jammers, the localized algorithm on the identification of trigger devices supports the feasibility on practical Smart Grid wireless mesh networks with great robustness. Finally, the testing rounds shows diversity due to the distance among interference-free testing groups according to the size of \(\alpha=\frac{R}{r}\), while parameter \(\alpha\) value bigger than 8 would be impractically scenarios. As indicated by Algorithm 2, disjoint interference-free testing groups have to be far away at least \(R+r\), therefore the distance between parallel testing groups is tightly related to the number of colors. Due to the fact that bigger \(\alpha\) results in more colors with smaller number of interference-free testing groups, Figure 5c discloses increasing trends of tests in both _TNI_ algorithms. #### 7.1.2 The Number of Nodes in Quarantine Areas

After the construction of a jamming-resistant message delivery path by shifting all the identified trigger devices to receivers only, it would be possible for them to be _unreachable triggers_ which are located too deep to receive messages in the case that a trigger would be not able to communicate with others but with triggers only. The number of unreachable trigger devices in the network is to be compared with the volume of jammed devices from _JAM_ algorithm, which is helpful to determine the actual size of quarantine regions out of wireless communication. This is because not only the unreachable triggers in our approach but also the jammed devices in the JAM scheme [12] cannot receive any messages. In accordance with Figure 6, the volume of unreachable trigger devices is always substantially less than the number of jammed devices from the JAM approach. Especially, in Figure 6a, less than a couple of devices are unreachable triggers and could not receive any wireless messages where \(n\in[1000,5000]\), but jammed devices in the JAM scheme get significantly larger within the higher network density. In Figure 6b, as predicted, the size of unreachable triggers remains small, less or equal to 10 jammers, but the jammed devices sprout with higher population with more jamming devices in the mesh networks. With a fixed number of jammers and wireless nodes, larger size of \(\alpha\) results in bigger impact from jammers, which implies more jammed nodes in the JAM algorithm. Yet, importantly, our identification approaches will not get affected by \(\alpha\) in terms of unreachable trigger nodes. That is, by utilizing the successful identification of all trigger nodes, actual jammed areas in which no node would be able to send out any messages to avoid a reactive jamming signal would be very small, so that substantially more devices would be participating in unsecured communications than in the JAM approach. Figure 6: _Cont._

## 8 Conclusions and Further Discussion

In this paper, we introduce a novel localized countermeasure to effectively tackle the reactive jamming threat to the Smart Grid wireless mesh networks by the identification of trigger devices. Our localized approach for the identification of all triggers accomplishes high implementable feasibility with low computational overhead in terms of message complexity and latency in time by the hexagon tiling scheme and the sequential group testing techniques. We design the hexagon tiling coloring algorithm to employ the availability on the spatial parallelism to perform the identification of triggers in the Smart Grid wireless mesh networks by reducing the overall latency of the group testing.