# A Novel Signal Design and Performance Analysis in NavCom Based on LEO Constellation
## 1 Introduction  
The global navigation satellite system (GNSS), as a national critical infrastructure (NCI), offers position, velocity, and time (PVT) services to various users around the world. Recently, the phase 3 BeiDou navigation satellite system (BDS) has also assisted in the launch of the 31 st satellite. In this era of global networking [1], it is the third GNSS system to provide global spatio-temporal services after GPS and GLONASS. Due to the vulnerability of the GNSS system itself, the service cannot meet various requirements, especially requirements related to accuracy, availability, integrity, and anti-jamming indicators, directly leading to huge restrictions being placed on satellite navigation applications. To meet the diversification requirements for positioning, navigation, and timing (PNT) capabilities, communication and remoting technologies can be used to extend signal coverage, called PNTRC. The concept of PNTRC was proposed to integrate positioning, navigation, timing, remoting, and communication services into one concept [2]. It corresponds to integration sensing and communication (ISAC) in B5G/6G and has received positive responses from Chinese scholars such as Prof. [PERSON], Prof. [PERSON], and Prof. [PERSON] [3; 4; 5]. The concept of integrated navigation and communication (NavCom) was first proposed in a U.S. report in 1977 [6]. Since then, the concept of NavCom has been adopted for the spatio-temporal grid and been widely mentioned in various fields. The concept of Aided GPS (A-GPS) was first proposed in the U.S. and originated from the application of inertial navigation and the Loran-C system in the maritime industry [7; 8]. However, the Boeing company led the combined Iridium with the GPS (iGPS) program and building of an LEO/MEO satellite hybrid system that combined communication satellite assets, including Iridium, to provide users with enhanced services and innovations regarding the integrity of iGPS [9]. In 2013, Germany proposed the L-band-based LDACS1 solution, based on the OFDM broadband system combined with the L-band broadband multi-carrier communication (B-AMC) and P34 system, for air traffic management (ATM) to achieve a ground-air data link connection fusion on the road [10; 11; 12]. Xibe, a seamless combination indoor and outdoor positioning system, solves the problem of the positioning and navigation access methods used by the end-users in the Asia-Pacific [13] region. Similarly, the Hongyan constellation plan was proposed by China and provides both broadband communication and space-based augmentation system (SBAs) services to end-users all over the world [14; 15]. With the large-scale application of 5G communication technology and the rapid development of multi-function micro-satellites or pico-satellites, signal design carried out under a multi-source signal system aiming at achieving \"one world, one network\" has become a \"conduction fusion\" (NAV/COM), which is the key link needing to be solved urgently. Prof. [PERSON] and his team from Beijing University proposed a TC-OFDM scheme integrated signal system for NavCom, which forms high-precision synchronization between ground base stations and satellites. After actual measurement and evaluation have been carried out, the accuracy of the signal can reach the meter level [16; 17; 18]. Prof. [PERSON] and her team at Wuhan University proposed a signal based on MSK and OFDM modulation and evaluated these two signals through navigation attributes and tracking performance. They believed that these two signals have better performance than other signals studied in the paper [19]. [PERSON] et al. proposed a navigation modulation method based on a multi-carrier composite carrier. Compared with the existing modulation signal, it has outstanding performance in terms of tracking accuracy, anti-interference, and spectrum utilization and can even be used as a signal for a ground-based augmentation system [20; 21; 22].