## 2 System Model of Aircraft  
### Network Model  
In this paper, we assume that there are three nodes (a source node, a relay node, and a destination node) as shown in Figure 1, the source node and the relay node are fixed in different places of the aircraft cabin, and the destination node is fixed at the aircraft wing. In general, a monopole antenna is equipped with the nodes instead of a dipole antenna due to space problem, which can make an omni-directional beam pattern as shown in Figure 1a. In contrast, to focus on the beam pattern to one point, an array antenna is used as shown in Figure 1b. The reason for the use of the beamforming technique is that it can enhance SNR at a particular point. Furthermore, the beamforming direction can be steered by adjusting the physical location or phase of each antenna [27]. In the case of time slot, the eight schemes need one or two time slots to complete the transmission in the wireless sensor networks. In this paper, the performance of each scheme in the aircraft channel environment can be found by each related equation in Section 3, which considers time slots of each scheme based on TDMA (time-division multiple access). In addition, we explain the relationship of the time slot in detail in terms of energy consumption. In the case of the single-hop scheme, the source node sends a signal to the destination node by using one time slot. Thus, the energy consumption is represented by TX power (the source node) and RX power (the destination node). In the case of the ABF and DBF schemes, the communication process is the same as the single-hop scheme. Thus, like the single-hop scheme the energy consumption is represented by TX and RX power. However, in the beamforming schemes the ABF and DBF schemes use several antennae, which should be considered in RX power. The single-hop and the beamforming schemes are shown in Figure 1c. Furthermore, in the case of the multi-hop scheme, in the fist time slot the source node sends a signal to a optimal neighbor node by using the source node routing table and the second time the relay node delivers the signal from the source node. Thus, the energy consumption of two links should be considered for the total energy consumption. In the case of the DF and AF scheme, in the first time slot the source node broadcasts a signal to the relay node and destination node. In the second time slot, the relay node delivers the signal from the source node to the destination node. Thus, the energy consumption of three links should be considered for the total energy consumption. In the case of the IDF and IAF schemes, in the first time slot the source node broadcasts a signal to the relay node and destination node, and after checking the signal, the destination node sends an ACK (acknowledgement) or a NACK (negative ACK). If both the source node and relay node receive the NACK, in the second time slot the relay node delivers the signal to the destination node. Contrarily, if those nodes receive the ACK, the relay node stops to deliver and the source node sends a new signal to the destination node. Thus, via the feedback from the destination node, the IDF and the IAF schemes can reduce the total energy consumption by saving the time slot. The multi-hop, DF, AF, IDF, and IAF schemes are shown in Figure 1d. In this paper, BPSK (binary phase shift keying) modulation is applied to all nodes when transmitting data in half-duplex mode and selection combining (SC) technique that compares the SNR from a relay node and a source node and selects the strongest to be applied to cooperative schemes. Finally, we assume that all of nodes have complete information of the channel state and the three nodes for cooperative communication are synchronized.