# Performance Analysis of Latency-Aware Data Management in Industrial IoT Networks +
## 5 Implementation and Experimental Evaluation  
### Experimental Strategy  
Strategic purpose: The strategic purpose of the experimental evaluation with real devices is to provide a realistic demonstration of how efficient data management methods can significantly improve the data access latency in industrial IoT networks, by using a limited number of proxies. The realistic approach is of paramount importance in our implementation strategy. For this reason, we follow some important steps. For the experimental implementation and evaluation, we use the Euratech testbed from the FIT IoT-LAB platform [14]. We use a network with technical specifications representative of the industrial IoT paradigm (e.g., low-power nodes, IEEE 802.15.4 radio interface, large number of devices, etc.). We carefully choose the \(L_{\max}\) threshold, according to actual industrial requirements and expert groups' recommendations. In order to have a benchmark for the performance of our method, we also implement two additional representative methods, based on routing mechanisms that are usual in current industrial IoT networks. We vary several experimental parameters so as to investigate the performance consistency of our method under different settings. Finally, we validate a simulation model based on the real-world settings, with which we can further investigate the changing parameters that are impossible or too time-consuming to investigate on the testbed. Experiment design: We use a total number of \(n=95\) nodes in the Euratech testbed, which form a 2D horizontal grid, as shown in Figure 3(a). Occasionally, during the experiments, there are some dead nodes, that is nodes that have run out of available power and are not able to function. This occasional unavailability of a subset of nodes renders the experiment even more realistic, since dead node situations frequently occur in real industrial IoT networks. The nodes that were used in the experiments are WSN430 open nodes, the design of which is displayed in Figure 3(b). The WSN430 open node is a note based on a low-power MSP430-based platform, with a set of standard sensors and an IEEE 802.15.4 radio interface at 2.4 GHz, using a CC2420 antenna [32], which can support, e.g., WirelessHART settings, typical of industrial communications. We used the TinyOS configuration for CC2420, which uses a MAC protocol that is compatible with 802.15.4 and is in principle a CSMA/CA scheme. We programmed and operated the nodes under TinyOS 2.1.1, a reference operating system for sensor nodes. Since the testbed nodes are placed a short distance from each other, we adjust their transmission range, so as to obtain a realistic multi-hop topology. We configured the antenna TX power such that, according to the CC2420 antenna datasheet [32] and the measurements provided in [33], the transmission range is about 3 m. However, given that this value has been measured in ideal conditions, without taking into account external factors such as obstacles and interference, we program every node \(u\in S\) to consider as a neighbor every other node \(v\in S\) with \(\epsilon(u,v)\leq 1\) m. Given this configuration, we obtain the topology that is depicted in Figure 4(a). Note that the three \"gaps\" in the topology are a result of the dead nodes of the deployment, which are unable to communicate with other nodes. We set the percentage of requesting nodes to \(m=0.1\cdot|S|\), selected uniformly at random from \(S\), and we set \(C=s_{1}\) as the central network controller, which corresponds to the node with \(\mathtt{node\_id}=1\) in the Euratech testbed (lower left node in Figure 4(a)). Setting the \(L_{\max}\) threshold: In order to perform the experiments in the most realistic way, it is important that the \(L_{\max}\) value be aligned with the official communication requirements of future network-based communication solutions for Industry 4.0, for the targeted industrial applications.