## 3 FloatingBlue  
\"FloatingBlue\" is a WSN communication architecture in which the main elements are Data Mules (DMs) that communicate among themselves via DTN and with sensor nodes using the BLE protocol in broadcasting mode.  
Sensing is challenging in large plantations and forested areas, such as those in the Amazonian jungle, due to the distances involved. Many sensors are battery-powered, and frequent replacement in remote locations can be impractical or costly. Energy-efficient technologies like BLE are crucial for extending sensor lifespans, especially in applications with sporadic data transmission. Therefore, the need for an architecture like \"FloatingBlue\" becomes evident as it optimizes sensor coverage and energy efficiency in challenging environments.  
Continuous connectivity is a challenge in remote locations with adverse environmental conditions. Connectivity can often be intermittent, making real-time data transmission difficult. DTN offers solutions to these situations by enabling data transmission in high-latency and frequently disconnected scenarios. Moreover, deploying communications infrastructure in remote areas can be relatively inexpensive. \"FloatingBlue\" proposes a solution that minimizes the need for fixed infrastructure by relying on data mules to transport information from sensors to a central station.  
The \"FloatingBlue\" architecture was explicitly developed to address these challenges. Using drones equipped with DTN as data mules and sensors that communicate with these drones via BLE, \"FloatingBlue\" provides broader coverage and energy-efficient transmission even in adverse conditions. This combination enables farmers and environmental managers to obtain monitoring data without needing extensive and costly network infrastructure.  
Figure 1 illustrates the proposed architecture. DM1 (3) is a mobile microcontroller device that can be attached to a vehicle, manned or unmanned, depending on the application, with each DM responsible for a sub-network. A sub-network consists of DMs and static SN, such as (4, 5). DM1 follows a movement routine to capture information from SNs as they enter their communication range. The data from SNs are transmitted and stored in DM1, then forwarded to other DM nodes (1) until they are offloaded at a central processing station (2).  
Each DM performs periodic scanning routines, while the SN transmits advertising packets with data collected by the integrated sensors. The DM nodes communicate with each other using Bundle Protocol 7, and, at the lower layers, TCP/IP (Transmission Control  
Figure 1: Proposal of the WSN FloatingBlue architecture.  
The DM node operates in two modes: collection mode and forwarding mode. In the collection mode, the DM implements both protocols, using BLE to receive data transmitted by SNs, and DTN Protocol 7 to encode the data into the bundle format for transmission to the destination entity. In the forwarding node mode, the node implements Bundle Protocol 7, performing store-and-forward mechanisms for the bundles.  
In the application layer of the protocol stack, software services form the \"FloatingBlue Manager\" layer, as shown in Figure 2. Two services are executed in this layer: \"BLE Handler\" and \"DTN Handler\". These applications integrate the DTN Protocol 7 and the BLE protocol stacks. The interaction dynamics and message flow between these services in the application layer are further detailed in Figure 3.  
The cycle begins with receiving an advertising signal (1) from a previously registered SN by the DM. When a registered SN is detected, the _BLE Handler_ service collects the data, formats it, and saves it into a text file (2). Subsequently, the _DTN Handler_ service transforms this file into a bundle (3), preparing it for transmission to the destination node (4).