China Satellite Navigation Office 2020 BeiDou Navigation Satellite System Signal In Space Interface Control Document Precise Point Positioning Service Signal PPP-B2b (Version 1.0) China Satellite Navigation Office July, 2020 China Satellite Navigation Office 2020 TABLE OF CONTENTS 1 Statement ····························································································· 1 2 Scope ·································································································· 2 3 BDS Overview ······················································································· 3 3.1 Space Constellation ········································································· 3 3.2 Coordinate System ·········································································· 3 3.3 Time System ················································································· 4 4 Signal Characteristics ··············································································· 5 4.1 Signal Structure ·············································································· 5 4.2 Signal Modulation ··········································································· 5 4.3 Logic Levels ·················································································· 6 4.4 Signal Polarization ·········································································· 6 4.5 Carrier Phase Noise ········································································· 6 4.6 Spurious ······················································································· 6 4.7 Correlation Loss ············································································· 6 4.8 Data/Code Coherence ······································································· 6 4.9 Signal Coherence ············································································ 7 4.10 Received Power Levels on Ground ······················································ 7 5 Ranging Code Characteristics ······································································ 8 6 Navigation Message Structure ···································································· 10 6.1 Message Format ············································································ 10 6.1.1 Brief Description ··································································· 10 6.1.2 Cyclic Redundancy Check ························································ 11 6.1.3 Coding Methods and Coding Parameters ······································· 11 6.2 Message Content ············································································ 13 6.2.1 Message Type Description ························································ 13 6.2.2 Message Type 1 ( Satellite Mask) ················································ 15 I BDS-SIS-ICD-PPP-B2b-1.0 2020-07 China Satellite Navigation Office 2020 6.2.3 Message Type 2 (Orbit Correction Parameters and User Range Accuracy Index) ························································································· 17 6.2.4 Message Type 3 (Differential Code Bias Correction) ························· 20 6.2.5 Message Type 4 (Clock Correction Parameters) ······························· 22 6.2.6 Message Type 5 (User Range Accuracy Index) ································ 25 6.2.7 Message Type 6 (Clock Correction and Orbit Correction - combination 1) 27 6.2.8 Message Type 7 (Clock Correction and Orbit Correction - combination 2) 29 6.2.9 Message Types 63 ·································································· 31 6.3 Information Validity ········································································ 31 7 User Algorithms ····················································································· 32 7.1 The Target Systems for the PPP-B2b Service ··········································· 32 7.2 Time and Space Coordinate System······················································ 32 7.3 Differential Code Bias Correction ························································ 32 7.4 Orbit Correction ············································································ 33 7.5 Clock Correction ············································································ 34 7.6 User Range Accuracy Index (URAI) ····················································· 34 7.7 System Time Solution ······································································ 34 8 Abbreviations ······················································································· 35 Annex Non-binary LDPC Encoding and Decoding Methods ··································· 37 II BDS-SIS-ICD-PPP-B2b-1.0 2020-07 China Satellite Navigation Office 2020 LIST OF FIGURES Figure 5-1 Ranging code generator of the PPP-B2b_I ············································ 8 Figure 6-1 The PPP-B2b_I navigation message frame structure ······························· 10 Figure 6-2 H81, 162 reading flow chart ······························································· 13 Figure 6-3 Bit allocation of message type 1 ······················································· 15 Figure 6-4 Bit allocation of message type 2 ······················································· 17 Figure 6-5 Bit allocation of message type 3 ······················································· 20 Figure 6-6 Bit allocation of message type 4 ······················································· 23 Figure 6-7 Bit allocation of message type 5 ······················································· 25 Figure 6-8 Bit allocation of message type 6 ······················································· 27 Figure 6-9 Bit allocation of message type 7 ······················································· 29 LIST OF TABLES Table 3-1 Parameters of the BDCS Reference Ellipsoid ·········································· 4 Table 4-1 Structure of the PPP-B2b signal ························································· 5 Table 4-2 Logic to signal level assignment ························································· 6 Table 5-1 Ranging code parameters of the PPP-B2b_I ··········································· 9 Table 6-1 Defined message types ··································································· 13 Table 6-2 Parameters of message type 1 ··························································· 15 Table 6-3 Parameters of message type 2 ··························································· 17 Table 6-4 Parameters of message type 3 ··························································· 20 Table 6-5 Definitions of signal and tracking modes ·············································· 22 Table 6-6 Parameters of message type 4 ··························································· 23 Table 6-7 Correspondence of SubType1 and satellites in message type 4 ····················· 24 Table 6-8 Parameters of message type 5 ··························································· 25 Table 6-9 Correspondence of SubType2 and satellites in message type 5 ····················· 26 III BDS-SIS-ICD-PPP-B2b-1.0 2020-07 China Satellite Navigation Office 2020 Table 6-10 Parameters of message type 6 ·························································· 27 Table 6-11 Parameters of message type 7 ·························································· 30 Table 6-12 Nominal validity ········································································· 31 IV BDS-SIS-ICD-PPP-B2b-1.0 2020-07 China Satellite Navigation Office 2020 1 Statement China Satellite Navigation Office is responsible for the preparation, revision, distribution, and retention of the BeiDou Navigation Satellite System (BDS) Signal In Space Interface Control Documents (hereinafter referred to as SIS ICD), and reserves the rights for final interpretation of this document. 1 BDS-SIS-ICD-PPP-B2b-1.0 2020-07 China Satellite Navigation Office 2020 2 Scope The construction and development of the BeiDou Navigation Satellite System is divided into three phases: BDS-1, BDS-2, and BDS-3 in sequence. This document defines the characteristics of the BDS Precise Point Positioning (PPP) Service Signal PPP-B2b. Transmitted by the BDS-3 Geostationary Earth Orbit (GEO) satellites, the PPP-B2b signal serves as the data broadcasting channel for correction parameters, such as satellite precise orbit and clock offset parameters of BDS-3 and other Global Navigation Satellite Systems (GNSS), and provides PPP services for users in China and surrounding areas. 2 BDS-SIS-ICD-PPP-B2b-1.0 2020-07 China Satellite Navigation Office 2020 3 BDS Overview 3.1 Space Constellation The nominal space constellation of BDS-3 consists of 3 GEO satellites, 3 IGSO satellites, and 24 MEO satellites. According to actual situation, spare satellites may be deployed in orbit. The GEO satellites operate in orbit at an altitude of 35,786 kilometers and are located at 80°E, 110.5°E, and 140°E respectively. The IGSO satellites operate in orbit at an altitude of 35,786 kilometers and an inclination of the orbital planes of 55 degrees with reference to the equatorial plane. The MEO satellites operate in orbit at an altitude of 21,528 kilometers and an inclination of the orbital planes of 55 degrees with reference to the equatorial plane. 3.2 Coordinate System BDS adopts the BeiDou Coordinate System (BDCS) whose definition complies with the standards of the International Earth Rotation and Reference System Service (IERS). The definition is also consistent with that of