Verifying the Safety of a Flight-Critical System

This paper describes our work on demonstrating verification technologies on a flight-critical system of realistic functionality, size, and complexity. Our work targeted a commercial aircraft control system named Transport Class Model (TCM), and involved several stages: formalizing and disambiguating requirements in collaboration with do- main experts; processing models for their use by formal verification tools; applying compositional techniques at the architectural and component level to scale verification. Performed in the context of a major NASA milestone, this study of formal verification in practice is one of the most challenging that our group has performed, and it took several person months to complete it. This paper describes the methodology that we followed and the lessons that we learned.Comment: 17 pages, 5 figure

Performance Comparison Of Hybrid 1-d Wdm/ocdma And 2-d Ocdma Towards Future Access Network Migration Scenario

In this paper, we provide a performance comparison and analysis between a hybrid 1-D WDM/OCDMA system and a 2-D WHTS OCDMA system. In the hybrid system, OOC is employed as users code sequence of the OCDMA dimension. The simulation results show that the hybrid system presents better performance than the 2-D WHTS OCDMA system, and show also that under a standard BER scenario, i.e., BER 10 9, the hybrid system can support at least 75% more simultaneous users than the 2-D OCDMA system for the analyzed case study. The analysis suggests that the hybrid 1-D WDM/OCDMA system is a qualified migration scenario since it can provide a smooth migration path from current networks towards OCDMA networks. © 2012 IEEE.Beyranvand, H., Salehi, J.A., Multirate and multi-quality-of-service passive optical network based on hybrid WDM/OCDM system (2011) IEEE Communications Magazine, 49, pp. 39-44Kitayama, K., Wang, X., Wada, N., OCDMA over WDM PON solution path to gigabit-symmetric FTTH (2006) J. Lightwave Technol., 24, pp. 1654-1662. , AprSanches, A.L., Dos Reis Jr., J.V., Borges, B.-H.V., Analysis of high-speed optical wavelength/time CDMA networks using pulse-position modulation and forward error correction techniques (2009) J. Lightwave Technol., 27 (22), pp. 5134-5144. , NovRaddo, T.R., Sanches, A.L., Dos Reis Jr., J.V., Borges, B.-H.V., A new approach for evaluating the BER of a multirate, multiclass OFFH-CDMA system (2012) IEEE Communications Letters, 16 (2), pp. 259-261. , FebYang, G.-C., Kwong, W.C., Performance comparison of multiwavelength CDMA and WDMA+OCDMA for fiber-optics networks (2002) Trans. of Communications, 45, pp. 1426-1434Shurong, S., Yin, H., Wang, Z., A new family of 2-D optical orthogonal codes and analysis of its performance in optical CDMA access networks (2006) J. Lightwave Technol., 24 (4), pp. 1646-1652. , AprYin, H., Richardson, D., (2007) Optical Code Division Multiple Access Communication, p. 123. , Ed. SpringerWang, X., Wada, N., Hamanaka, T., Miyazaki, T., Cincotti, G., Kitayama, K., OCDMA over WDM transmission (2007) Proc. ICTON 2007, , Rome, Italy, July, paper Tu.B1.

Formal Verification of Curved Flight Collision Avoidance Maneuvers: A Case Study

under contracts no. 2008TJ1860, and by the Air Force (University of Vanderbilt) under contract no. 18727S3. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressed or implied, of any sponsoring institution or government. Keywords: formal verification of hybrid systems, deduction, air traffic control, logic for hybrid Aircraft collision avoidance maneuvers are important and complex applications. Curved flight exhibits nontrivial continuous behavior. In combination with the control choices during air traffic maneuvers, this yields hybrid systems with challenging interactions of discrete and continuous dynamics. As a case study illustrating the use of a new proof assistant for a logic for nonlinear hybrid systems, we analyze collision freedom of roundabout maneuvers in air traffic control, where appropriate curved flight, good timing, and compatible maneuvering are crucial for guaranteeing safe spatial separation of aircraft throughout their flight. We show that formal verification of hybrid systems can scale to curved flight maneuvers required in aircraft control applications. We introduce a fully flyable variant of the roundabout collision avoidance maneuver and verify safety propertie