# Development, Implementation and Evaluation of An Epidemic Communication System
## 3 Implementation Method for Epidemic Communication
### Interference between Multiple Nodes and Transmission Area  
The proposed model of the epidemic communication system employs a network in which drones relay images of flowers, as shown in Figure 3. The background of this system model is an autonomous drone system for pollinating tomato flowers or pear flowers, where clustered drones fly around the stem of a tomato or the tree of a pear, searching for pollinatable flowers [13, 14, 15, 16]. The drones are equipped with cameras, and by relaying the captured images of flowers to an external network, an external server performs artificial intelligence (AI) image classification. In this system, drones capture flower images repeatedly, relay data to other drones during exploration, and deliver the image data to an external server using the epidemic communication. The epidemic communication used in the proposed system is in the broadcast mode. In the broadcast mode, whenever a drone with flower data encounters another drone, it transfers the data. Therefore, as shown in Figure 4, each wireless station autonomously transfers data to nearby wireless stations during relay transmission. However, in the circled part of the figure, simultaneous communication between different wireless stations occurs, leading to radio interference. Figure 5 illustrates the conditions for the interference. In this interference model, wireless station A was assumed to transfer data to wireless station B, and simultaneously, wireless station C transferred data to wireless station D in its vicinity. The desired signal from C to D is omnidirectional and propagates to its surroundings, thereby causing interference with the desired signal from A to B. While increasing the distance between B and C reduces the interference, it decreases the node density within the cluster, resulting in a lower encounter probability between drones and a reduction in the infection speed. In addition, modulation schemes with interference have lower modulation orders, resulting in a decrease in the transmission rate. To address these challenges, the available transmission rates based on the distance between B and C were calculated using the following formula and Table 1. In this study, it is necessary to evaluate the effects of interference and other factors in order to design a transmission system suitable for epidemic communication for implementation in drones. However, there are no wireless devices dedicated to epidemic communications. Therefore, we adopted a wireless LAN system as a wireless device that we can develop. For the IEEE 802.11g wireless LAN standard, we calculated the available transmission rate based on the relationship between the minimum received sensitivity level and the signal-to-noise-plus-interference ratio (SINR) [36], which includes the amount of interference, using Equations (1) to (3). \[P_{\text{RX}}=P_{\text{TX}}-20\log\biggl{(}\frac{4\pi df}{c}\biggr{)}+G_{\text {TX}}+G_{\text{RX}}+10\log W \tag{1}\]In Equation (1), \(d\) represents the distance between antennas (inter-wireless station distance), \(c\) denotes the speed of light, and \(f\) represents the frequency. Additionally, let \(W\) be the bandwidth, \(G_{\text{TX}}\) be the antenna gain of the transmitting station, and \(G_{\text{RX}}\) be the antenna gain of the receiving station. In Equation (1), the transmit power is denoted as \(P_{\text{TX}}\), and the received power \(P_{\text{RX}}\) is calculated. To determine the inter-wireless station transmission rate, the signal-to-noise-plus-interference ratio (SINR) is computed, including the noise power (NP). In Equation (1), \(P_{\text{RX}}^{A,B}\) represents the received power between wireless stations \(A\) and \(B\), while \(P_{\text{RX}}^{B,C}\) denotes the received power between wireless stations \(B\) and \(C\). \[\text{SINR}=\frac{P_{\text{RX}}^{A,B}}{\text{NP}+P_{\text{RX}}^{B,C}} \tag{2}\]  
Equation (2) calculates the SINR. \[R_{\text{min}}=\text{SINR}-91\text{ dB} \tag{3}\]  
Equation (3) determines the minimum receive sensitivity level (\(R_{\text{min}}\)).