spans the frequency range from 1164 to 1214 MHz, contains two signals, denoted E5a and E5b, which are centered at 1176.45 and 1207.140 MHz, respectively. Each signal has an in‐phase component and a quadrature component. Both components use spreading codes with a chipping rate of 10.23 Mcps (million chips per second). The in‐phase components are modulated by navigation data, while the quadrature components, called pilot signals, are data‐free. The data‐free pilot signals permit arbitrarily long coherent processing, thereby greatly improving detection and tracking sensitivity. A major feature of the E5a and E5b signals is that they can be treated as either separate signals or a single wide‐band signal. Low‐cost receivers can use either signal, but the E5a signal might be preferred, since it is centered at the same frequency as the modernized GPS L5 signal and would enable the simultaneous reception of E5a and L5 signals by a relatively simple receiver without the need for reception on two separate frequencies. Receivers with sufficient bandwidth to receive the combined E5a and E5b signals would have the advantage of greater ranging accuracy and better multipath performance.
Even though the E5a and E5b signals can be received separately, they actually are two spectral components produced by a single modulation called alternate binary offset carrier (AltBOC) modulation. This form of modulation retains the simplicity of standard binary offset carrier (BOC) modulation (used in the modernized GPS M‐code military signals) and has a constant envelope while permitting receivers to differentiate the two spectral lobes.
The in‐phase component of the E5a signal is modulated with 50 sps (symbols per second) navigation data without integrity information, and the in‐phase component of the E5b signal is modulated with 250 sps data with integrity information. Both the E5a and E5b signals are available to the OS and CS services.
E6 Band
This band spans the frequency range from 1260 to 1300 MHz and contains a C/NAV signal and a G/NAV signal, each centered at 1278.75 MHz. The C/NAV signal is used by the CS service and has both an in‐phase and a quadrature pilot component using a BPSK spreading code modulation of 5 × 1.023 Mcps. The in‐phase component contains 1000‐sps data modulation, and the pilot component is data‐free. The G/NAV signal is used by the PRS service and has only an in‐phase component modulated by a BOC(10,5) spreading code and data modulation with a symbol rate that is to be determined.
L1/E1 Band
The L1/E1 band (sometimes denoted as L1 for convenience) spans the frequency range from 1559 to 1591 MHz and contains a G/NAV signal used by the PRS service and an I/NAV signal used by the OS and CS services. The G/NAV signal has only an in‐phase component with a BOC spreading code and data modulation. The I/NAV signal has an in‐phase and quadrature component. The in‐phase component contains 250‐sps data modulation with a BOC(1,1) spreading code. The quadrature component is data‐free and utilizes a combined BOC signal.
1.2.4 BeiDou
The BeiDou Navigation Satellite System (BDS) is being developed by the People's Republic of China (PRC), starting with regional services and expanding to global services. Phase I was established in 2000. Phase II (BDS‐2) provides service for areas in China and its surrounding areas. Phase III (i.e. BDS‐3) is being deployed to provide global service.
1.2.4.1 BeiDou Satellites
BeiDou will consist of 27 MEO satellites, including 5 geostationary Earth orbit (GEO) satellites and 3 inclined geosynchronous orbit (IGSO) satellites. The GEO and IGSO satellites will be at longitudes to support the China and the surround areas of Southeast Asia.
1.2.4.2 Frequency
The BDS‐2 and BDS‐3 operate on various frequencies in the L1 (BDS‐3 B1C signal at 1575.42 MHz), E6 (BDS B3I signal at 1268.5 MHz), E5 (BDS‐2 and BDS‐3 at 1207.14 MHz; and BDS‐3 (B2a) at 1176.45 MHz). These signals use various navigation data formats from the BDS MEO, GEO, or IGSO satellites to support global and regional civil services. Details of this section are given in Chapter 4.
1.2.5 Regional Satellite Systems
There are several regional satellite systems that provide regional navigation and/or augmentation service.
1.2.5.1 QZSS
Quasi‐Zenith Satellite System (QZSS) is satellite‐based navigation system being developed by the Japanese government. QZSS has a constellation of four IGSO satellites that provide navigation and augmentation to GPS over Japan and Southeast Asia. The system transmits GPS‐type signals: L1 (L1 C/A and L1C), L2C, and L5, as well as, augmentation signals to support submeter and centimeter level services. Details of this section are given in Chapter 4.
1.2.5.2 NAVIC
The Indian Regional Navigation Satellite Systems, operationally known as NAVIC, is a regional satellite navigation system developed by the Indian Space Research Organization (ISRO). NAVIC constellation consists of eight satellites operation in GEO‐ and IGSO‐type orbits, where satellites transmit navigation signal in the L5 and S‐band. Details of this section are given in Chapter 4.
1.3 Inertial Navigation Overview
The following is a more‐or‐less heuristic overview of inertial navigation technology. Chapter 3 has the essential technical details about hardware and software used for inertial navigation, and Chapter 11 is about analytical methods for statistical characterization of navigation performance.
1.3.1 History
Although the theoretical foundations for inertial navigation have been around since the time of Isaac Newton (1643–1727), the technology for reducing it to practice would not become available until the twentieth century. This history can be found in the accounts by Draper [22], Gibson [23], Hellman [24], Mackenzie [2], Mueller [18], Wagner [25], and Wrigley [26]. For an account of the related computer hardware and software developments through that period, see McMurran [27].
1.3.1.1 Theoretical Foundations
It has been called “Newtonian navigation” [28] because its theoretical foundations have been known since the time of Newton.2
Given the position x(t0) and velocity v(t0) of a vehicle at time t0, and its acceleration a(s) for times s > t0, then its velocity v(t) and position x(t) for all time t > t0 can be defined as
(1.1)
(1.2)
It follows that given the initial position x(t0) and velocity v(t0) of a vehicle or vessel, its subsequent position depends only on its subsequent accelerations. If these accelerations could be measured and integrated, this would provide
