# Channel Measurement and Feasibility Test for Wireless Avionics Intra-Communications
## 3 Experimental Setup
### Measurement Environment  
The main objectives of our experiment were to measure wireless channel and to test the feasibility of adopting IEEE 802.11 physical layer specification in the real aircraft. We performed our experiment in a flight test site located in South Korea. The target aircraft was KT-1 Woongbi, shown in Figure 5, which is used for basic training aircraft in Korean, Indonesian, Turkish, and Peruvian Air Forces. WAIC is designed to reduce the use of cable, eventually resulting in the weight of a big-sized aircraft and saving fuel. However, it is worth noting that the basic cover material for both KT-1 Woongbi and a WAIC-targeted aircraft such as a passenger plane (e.g., airbus A380) would be similar, so-called _poly-fiber_[13]. From the perspective of the wireless communication, a major difference between wireless networks in the big-sized aircraft and the small-sized one would be the number  
Figure 4: Measured performance of the designed monopole antenna. Figure 3: Structure and prototype of the designed monopole antenna. of multi-hops including relay nodes. Thus, there are two advantages of doing the field test on the small-sized aircraft such as KT-1 Woongbi: (1) Our experiment implies all feasibility tests based on in a single-hop network, which could be a part of a local network in the big-sized aircraft. (2) Our approach provides clear intuitions on the feasibility of WAIC by analyzing the small-sized aircraft such as a module of the big-sized aircraft, instead of a relatively complicated experiment in the big-sized aircraft. (Since our experiment on the small-sized aircraft can be considered as a module test of the big-sized aircraft, a combining test should be done (i.e., combining multiple single hop networks to one multi-hop network. However, this is beyond the scope of this paper.) The specification of this aircraft is briefly summarized in Table 2[14]. Specifically, we set several measurement points in KT-1 Woongbi for our experiment, as described in Figure 6. At each point, we obtained multiple measurement samples to remove the effect of white noise based on time (or frequency) domain averaging. Additionally, we performed measurements by changing spatial positions in one point (e.g., P1) for spatial averaging. Note that a distance between measurement points is specified in Section 4. Please refer to Appendix A for inside photos of KT-1 Woongbi at each measurement point. Figure 7 shows measurement example in our experiment including antenna setup example. Figure 7a depicts an example of setting the monopole antenna at measurement point P2 (left rear room). Note that we put the antenna at the desired point after open the cover, and obtained measurement \begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Description** \\ \hline Crew & two in tandem \\ Length & 10.26 m \\ Wingspan & 10.59 m \\ Height & 3.68 m \\ Wing area & 16.01 m\({}^{2}\) \\ Empty weight & 1910 kg \\ Loaded weight & 2540 kg \\ Max. takeoff weight & 3331 kg \\ Powerplant & Pratt \& Whitney Canada PT6A-62 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Specification of KT-1 Woongbi [14]. Figure 5: The appearance of KT-1 Woongbi. Figure 6: Measurement points in KT-1 Woongbi and their descriptions. results after closing the cover. To properly close the cover and prevent damage to the antenna cable, we set small materials (e.g., sphere-type styrofoam, \(\circled{\circ}\) in Figure 6(a)) at the corner of the cover closure. Figure 6(b) shows an overall measurement setup between P0 (cockpit) and P1 (engine room) after the cover is closed. During our experiment, we measured a _single_ transmitter-receiver link at _one time_ instead of multiple links simultaneously. (If we measured multiple links simultaneously at the same frequency band, channel measurement could be distorted by interference between multiple links.) Obviously, there was interference when we considered multiple data transmission at the same time (e.g., transmission of measured data by multiple sensors).