# Chaotic Orthogonal Composite Sequence for 5G NR Time Service Signal Capture Algorithm
## 1 Introduction  
To date, major countries around the world have proposed the establishment of a national comprehensive Positioning, Navigation and Timing (PNT) system. This refers to a national information infrastructure that, under unified organization and coordination at the national level, serves the purposes of national defense, the economy and society. It undertakes tasks such as the establishment and maintenance of national spatiotemporal benchmarks, the dissemination and acquisition of spatiotemporal information, and PNT services and applications [1, 2]. Based on the existing need for more ubiquitous, integrated and intelligent systems, and also considering the actual needs and application scenarios of various users, the primary goal of the comprehensive PNT system is to provide adaptive and resilient PNT application services. A resilient comprehensive PNT application service system and network should be the main future development direction. \"Resilience\" here means that PNT services are not affected by environmental factors and have high availability, continuity and reliability [3, 4]. The national comprehensive PNT system is an integral spatiotemporal information network that combines satellite navigation systems as the core with low-orbit satellites, ground-based 5G communications, pseudolites, autonomous sensors, and other PNT means [5, 6]. It merges the capabilities of unified spatiotemporalbenchmarks, network interconnection and resilient collaborative operation [7; 8]. Among them, ground-based 5G communication technology is expected to become an important component of the comprehensive PNT system [9; 10; 11], playing a crucial role in completing the entire comprehensive PNT system and building a global intelligent society based on spatiotemporal information [12]. In recent years, the rapid development of 5G communication technology, relative to 4G communication, has achieved a communication rate of up to 10 Gbps, latency reduced to 1 ms, and the ability to connect millions of terminals per square kilometer. 5G communication technology will greatly promote the development of fields such as artificial intelligence, cloud computing, big data, autonomous driving, and the Internet of Everything, making a significant contribution to the national economy. When broadcasting timing signals using 5G communication technology, timing information can reach the nanosecond level, as opposed to the microsecond level of 4G [13; 14; 15]. With the deployment of 5G macro base stations and micro base stations, 5G can provide signal coverage both indoors and outdoors, allowing users to receive signals without environmental restrictions. This also makes the further exploration of 5G-based timing modes possible. [PERSON] et al. [16] proposed a new carrier phase positioning technology suitable for new 5G wireless cellular networks, developing a clock offset estimation method based on carrier phase to achieve picosecond-level clock synchronization between base stations, which gradually converges to the Cramer-Rao lower bound (CRLB). [PERSON] et al. [17] proposed a precise time protocol (M-PTP) to address the high cost of hop-by-hop deployment of IEEE 1588 PTP, achieving an precision of 11.61 ns at 5 hops according to the experimental results. [PERSON] et al. [18] analyzed the synchronization problem of longitudinal differential protection time in distribution networks based on 5G networks and proposed a time synchronization algorithm built on the NTP protocol. [PERSON], [PERSON] et al. [19] asserted that 5G-Advanced networks would become a fully feasible technological alternative or a supplement to global navigation satellite systems (GNSS) for providing time synchronization with UTC or any well-defined time reference. [PERSON], [PERSON] et al. [20] proposed the application of related space satellites based on RTK positioning algorithms as a binary formation system to improve the timing error (TE) between user equipment (UE) and base stations, thereby enhancing the performance of 5G timing synchronization.