## 1 Introduction  
The simulation is defined as the imitative representation of the functioning of one system or process by means of the function of another and the modeling is defined as producing a representation or simulation [1]. Navigation warfare is defined as protecting the use of PNT (position, navigation and timing) information by friendly forces against the hostile attack with the electronic warfare method [2]. Since the received Global Navigation Satellite System (GNSS) signal strength is very weak and the signal structure of GNSS for civil use is open to the public, GNSS can be easily attacked by jamming, meaconing, and spoofing under the navigation warfare [3, 4]. In order to overcome this weak point of the GNSS, other radio navigation systems can be integrated with the GNSS [3; 5; 6]. The FAA (Federal Aviation Administration) in the U.S. has announced a plan to use ground-based radio navigation systems when the GPS (Global Positioning System) is attacked by jamming and/or spoofing [6; 7]. An alternative navigation system with enhanced Long-range navigation (eLoran) and the GNSS for marine navigation was proposed by the GLA (General Lighthouse Authority) in the U.K. [8]. Research on the multi-radio integrated navigation system has been conducted in Korea [9; 10; 11; 12; 13]. A regional satellite navigation system and ground-based radio navigation systems are additionally used with GPS in order to have a continuous navigation solution [9; 10; 14]. The regional satellite navigation system with seven satellites, called the KNSS (Korean Navigation Satellite System), will be deployed by the Korean government. Ground-based radio navigation systems include DME (Distance Measuring Equipment), Loran-C (Long-range navigation), e-Loran, and VOR (Very high-frequency Omnidirectional Radio range). Even though the KNSS and ground-based radio navigation systems are used with GPS, navigation performance can be unsatisfactory. In this case, fixed and/or moving pseudo-satellites (pseudolites) will be additionally integrated. Before real-time radio navigation systems are deployed, lots of tests and performance evaluations should be carried out. The M&S (modeling and simulation) software can be used for performance evaluation in order to save cost and time [9; 15]. When the software is not complicated, it may be efficient to design the software in one module. However, when the software is sophisticated, it is more efficient to design a modularized software. By modularizing, it is easy to modify and/or to replace the software [16; 17; 18; 19; 20]. In this paper, a message broker-based M&S software design method was proposed. The whole M&S software was divided into function modules in the proposed design method. All the messages were transferred through the message broker in order to be exchanged between the function modules. Due to the message broker, each function module could be independently operated. A message broker-based multi-radio integrated navigation M&S software was designed using the proposed method. The M&S software was comprised of a GUI module, a navigation environment generation module, a navigation algorithm module, a coverage analysis module, and an M&S message broker. In order to show the feasibility of the proposed design method, the M&S software was implemented for GPS, KNSS, eLoran, Loran-C, and DME/VOR. The M&S software was programmed in Visual C++ under a Windows 10 operating system. The performance of the multi-radio integrated navigation system was evaluated under the navigation warfare environment through the M&S software. The results of the multi-radio integrated navigation system were compared with those of GPS only navigation when the GPS was attacked by a jammer. This is an extension of the authors' conference paper [21]. The effect of the jammer power to GPS measurements was modeled and included in the navigation environment generation module of the implemented M&S software. The navigation warfare scenario editor was added in the graphical user interface (GUI) for the M&S parameter setting.