## 5 Conclusions  
This paper proposes a dependable wireless system with shortened code using distance information between integrated terminals. The proposed wireless system has three features to enhance resistance from cybererrorists. First, integrated terminals with multiple RATs and CODEC communicate encoded information using multiple RATs. Even if some RATs are attacked, the transmitted information can be recovered using encoded information received by other RATs. Even if some RATs are wiretapped,  
Figure 12: Characteristics of the mutual information versus the shortened information length when the sender and the receiver communicate using three RATs. The circle marks and the square marks indicate the mutual information between the sender and receiver when two and one RAT(s) cannot be used for communication due to an attack, respectively. The triangle marks and the cross marks indicate the mutual information between the sender and the cyberterrorist when two and one RAT(s) are/is wiretapped, respectively. Figure 13: Characteristics of the secrecy capacity versus the shortened information length when the sender and the receiver communicate using three RATs. The circle marks, the square marks, the triangle marks, and the cross marks indicate the secrecy capacity of the cyberterrorist attacking on three RATs, attacking on two RATs and wiretapping on one RAT, attacking on one RAT and wiretapping on two RATs, and wiretapping on three RATs, respectively. the transmitted information cannot be recovered using less encoded information. Second, the shortened code is adopted as an error correction code. If the receiver knows the shortened information and the cybererrorist does not know it, it is possible to provide a high correction capability to the receiver and low correction capability to the cybererrorist. Finally, the distance information between integrated terminals can be measured securely and accurately using UWB. This can improve the capability to protect against wiretapping and attacks in a practical system. It was confirmed that when two RATs were used for communication, by increasing the shortened information length, the secrecy capacity defined by the maximum transmission rate between the sender and the receiver when the cybererrorist cannot receive any information could be over 0.7, and that it could be further increased by using three RATs. Although the proposed scheme has a limited capability to protect against wiretapping and attacks, the information-theoretic security capability can be improved. Since the degree of freedom of countermeasures increases as the number of RATs used for communication increases, various countermeasures can be implemented depending on the assumed cybererrorist by changing the shortened information length. The following points are mentioned as topics for future work. * Though the shortened information length is the parameter which decides the wiretapping resistance and attack resistance, it is necessary to investigate optimization of the shortened information length and quantization technique, because it is also related to error resistance of distance information. * It is necessary to examine the effect of the shortened information predicted by the cybererrorist and the countermeasures and to analyze the performance limit and drawback. * The evaluation assumes that RAT communication is completely lost due to the attack, but it is necessary to evaluate the actual attack pattern and the impact of attack resistance on each RAT. * It is necessary to analyze performance degradation due to measured distance error or accuracy. * It is necessary to examine the application to other codes, because large gain can be obtained by using powerful codes. * Evaluation of dependability properties based on heuristic strategies such as \"what-if analysis\" and \"robustness checking\" are described in [2]. * Finally, an evaluation using a real system is necessary. **Author Contributions:** Conceptualization, Y.A. and R.K.; methodology, Y.A. and R.K.; software, Y.A. ; validation, Y.A.