Introduction

Navigation signals serve as a core technology of satellite navigation systems, with their performance directly determining the system's service capability. High-performance navigation signals compatible with and interoperable with existing systems such as GPS represent a critical factor for the BeiDou Navigation Satelite System (BDS) to achieve world-class status, drive industry development, and deliver global services.

Chinese-Characteristic, World-Class Navigation Signal System

1. The project invented Quadrature Multiplexed Binary Offset Carrier (QMBOC) modulation. It overcame the challenge of orthogonal combination across frequency, phase, and code domains under ITU spectrum constraints, achieving 20% lower ranging error compared to GPS L1C. The BDS B1C signal based on QMBOC enhances ranging accuracy and multipath mitigation significantly.

2. The project invented a Constant Envelope Multiplexing with Intermodulation Construction (CEMIC) method.It resolved the challenge of constant-envelope multiplexing for signals with arbitrary power ratios and phase relationships, achieving an 83.6% multiplexing efficiency. It enables high-efficiency broadcasting of two generation signals in the B1 band, ensuring a smooth transition from BDS-2 to BDS-3.

3. The project invented Asymmetric Constant Envelope Binary Offset Carrier (ACEBOC) modulation. It solved the challenge of constant-envelope synthesis for dual-frequency mulf-components with arbitrary power ratios, achieving 33% lower ranging error compared to Galileo E5a/b. The B2a/b signal based on ACEBOC enables five services broadcasting with a unified architecture across satellites, supporting the world's first multi-functional hybrid constellation for BDS-3.

BeiDou Signal: Global Coverage, Leading Performance

The project has received the 2025 First Prize of Technological Invention from the Ministry of Education of China's (pending award) and the 2020 Special Prize for Satelite Navigation Science and Technology from the GNSS and LBS Association of China. It has secured 28 Chinese and 48 foreign patents, and facilitated the China-US BDS/GPS bilateral statement. It has been applied to all 35 BDS-3 satellites providing global services and field tests demonstrate world-leading positioning accuracy. It has driven the formation of a 5-tilion-yuan satellite navigation industry in China, and been incorporated into national standards and international standards such as ICAO, IMO, and 3GPP. The project now serves over 200 countries and regions with billions of users worldwide.

The project's patents include signal transmission and signal reception, and have been authorized in 17 countries and regions globally. It has laid a solid technical foundation for developing high-performance, low-power receiver chips, propelling the global navigation industry forward. According to data from the GNSS and LBS Association of China (GLAC), the core output value of terminal chips components, and algorithms relying directly on satellite navigation signals in China reached 96.6 billion yuan in the past three years; with a 1% contribution rate, the project's technological achievements have generated approximately 960 million yuan in economic benefits over the same period.

BeiDou of China, BeiDou for the World

The project proposed BDS-3 B1 and B2 signal schemes addressed challenges such as spectrum resource scarcity, transmission power limitations, multi-signal and multi-sevice broadcasting, smooth transition requirements, and compatibility and interoperability constraints. To date, all 35 networking satellites have adopted the project's achievements, providing services globally. According to the GNSS Service Monitoring and Assessment Monthly Report released by the Test and Assessment Research Center of China Satellite Navigation Office, since its official launch in July 2020, BDS-3 has maintained world-class service performance with positioning accuracy ranking first globally.

In international collaboration and exchanges, the compatibility and interoperability of navigation signals are critical to fostering international partnerships. Following spectrum coordination under the ITU framework, the QMBOC-based B1C signal directly facilitated the successful completion of the China-U.S. B1C and L1C signal interoperability negotiations in 2017, culminating in a joint statement between the two countries and removing the last obstacle in BDS-3's development. Subsequently, BDS-3 has been integrated into international standards set by organizations such as ICAO, IMO, 3GPP, and COSPAS-SARSAT, and the research enabled BDS-3 to serve the global community and benefit humanity.