## 5 Discussion of the Results
### Federations While Releasing the Balloons  
Other federations are established while the balloons start to lift. Figure 14 presents the packet sequence of a set of them when Balloon A is raising. In this case, the customer of the  
Figure 13: Buffer usage of Balloon C (green) and Balloon B (red) in data packet unit. federation is Balloon B which requests up to eight federations in more than three minutes. Specifically, the ground station opens the downlink connection with Balloon A at 12:12:46, which starts to download its data. Then, it publishes the service to the others. Balloon B requests the service at 12:12:54, which is suddenly accepted by Balloon A, starting the first federation. Balloon B downloads its data using the federation, which remains open until Balloon B empties its buffer (at 12:13:20). At this moment, the federation is no longer needed, and Balloon B triggers the closure phase. After the correct three packet exchange, the federation is closed, and Balloon A starts to publish the service again (because the downlink is still open). Please note that Balloon A keeps downloading its data while it is publishing the service. A new service request from Balloon B is performed at 12:13:32, because it has generated an additional data packet. After downloading the packet, Balloon B closes again the federation. This situation is periodically repeated due to the data generation of Balloon B. Please note that during all these federations, Balloon B is placed on ground, while Balloon A is flying. This means that Balloon B can download data to the ground station using the relay of Balloon A which is indeed over both nodes, as Figure 15 shows. From the first federation until the last one, Balloon A follows a trajectory that reaches elevation angles close to 90\({}^{\circ}\). This high elevation provokes the retransmission of some packets that are lost. It is the case of the last federation, which indeed the connection is not established. Therefore, asymmetric links exist in this scenario. Figure 14: Sequence of packets exchanged in federations while the balloons start to be released. Figure 15: Representation of the federation established while balloons being released. The buffer usage, presented in Figure 16, highlights this data download with the federation. When the downlink is established, Balloon A downloads all its data and empties its buffer. Then, Balloon B can also empty its buffer thanks to the federation with Balloon A. After that, both buffers remain empty thanks to the multiple federations. Once the communication is not feasible, Balloon B increases its buffer with new data (at 12:15:30). The global throughputs achieved in this scenario remains similar to the ground case, being 790.6 bps for downlink communications and 167.4 bps for federation communications. This performance is achieved because the PER also remains similar, with 0.0% for downlink, and 15.6% for federation. This throughput is equivalent to 43.8% and 63.0% (respectively) of the maximum throughput, defined in Equation (6). After finishing this interaction, Balloon B starts to fly. At this moment, the communications between Balloon A and the ground station experienced a degradation in the link quality, making it difficult to keep the connection open. For that reason, the operator switched to Balloon B to download data from Balloon A, as represented in Figure 6. Figure 17 presents the packet sequence during this situation, demonstrating the establishment of multiple federations that enabled downloading Balloon A data. As in the previous cases, the ground station opens the downlink connection with Balloon B at 12:18:40, and this one starts to download data. After finishing, it starts to publish the service, which Balloon A requests periodically. These federations help to connect Balloon A with the ground station (over Balloon B), which the communication was no longer feasible. Please note that some packets are retransmitted due to the asymmetric link created between balloons, as in the previous case.