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LGRS.2011.2107500

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10.1109/JSTARS.2014.2320298

DOI: 10.1109/TGRS.2012.2230401

(GNSS+R); West Lafayette, IN; 2012. pp. 1–4

**Chapter 6**

**Provisional chapter**

**GNSSs, Signals, and Receivers**

**GNSSs, Signals, and Receivers**

DOI: 10.5772/intechopen.74677

This chapter describes Global Navigation Satellite Systems (GNSSs) and their signal characteristics, beginning with an overview of Global Positioning System (GPS) architecture and describing its three primary segments: control, space, and user segments. After that, it addresses the GPS modernization program including the new civilian and military signals and their significance. It continues by outlining the GPS signal characteristics and the sources of GPS measurement error. GPS receivers as well are briefly described. Then, it gives an overview of the GLONASS and describes its modernization program. Additionally, it delves into many aspects the GLONASS, including GLONASS signal characteristics, the GLONASS radio frequency (RF) plan, pseudorandom (PR) ranging codes, and the intra-system interference navigation message. Finally, GPS and GLONASS are compared to highlight the advantages of combined GPS and GLONASS

Navigation solutions have become part of our daily life due to their widespread use in a range of applications including agriculture, navigation by land vehicles, and pedestrian navigation. A key navigation technology used in such applications is Global Navigation Satellite Systems (GNSSs), and several such systems currently provide this service. The US Global Positioning System (GPS) was this first such fully functional system. GLONASS, the Russian system, was the second to be active, and it also has global coverage. Similarly, the European Union satellite

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Mohamed Tamazin, Malek Karaim and

Mohamed Tamazin, Malek Karaim and

http://dx.doi.org/10.5772/intechopen.74677

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

measurements over the GPS-only measurements.

**Keywords:** GNSS, GPS, GLONASS, signals, GNSS modernization

navigation system, Galileo, is scheduled to be fully operational in 2018.

Aboelmagd Noureldin

Aboelmagd Noureldin

**Abstract**

**1. Introduction**

#### **Chapter 6 Provisional chapter**

#### **GNSSs, Signals, and Receivers GNSSs, Signals, and Receivers**

Mohamed Tamazin, Malek Karaim and Aboelmagd Noureldin Mohamed Tamazin, Malek Karaim and Aboelmagd Noureldin

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.74677

#### **Abstract**

This chapter describes Global Navigation Satellite Systems (GNSSs) and their signal characteristics, beginning with an overview of Global Positioning System (GPS) architecture and describing its three primary segments: control, space, and user segments. After that, it addresses the GPS modernization program including the new civilian and military signals and their significance. It continues by outlining the GPS signal characteristics and the sources of GPS measurement error. GPS receivers as well are briefly described. Then, it gives an overview of the GLONASS and describes its modernization program. Additionally, it delves into many aspects the GLONASS, including GLONASS signal characteristics, the GLONASS radio frequency (RF) plan, pseudorandom (PR) ranging codes, and the intra-system interference navigation message. Finally, GPS and GLONASS are compared to highlight the advantages of combined GPS and GLONASS measurements over the GPS-only measurements.

DOI: 10.5772/intechopen.74677

**Keywords:** GNSS, GPS, GLONASS, signals, GNSS modernization

#### **1. Introduction**

Navigation solutions have become part of our daily life due to their widespread use in a range of applications including agriculture, navigation by land vehicles, and pedestrian navigation. A key navigation technology used in such applications is Global Navigation Satellite Systems (GNSSs), and several such systems currently provide this service. The US Global Positioning System (GPS) was this first such fully functional system. GLONASS, the Russian system, was the second to be active, and it also has global coverage. Similarly, the European Union satellite navigation system, Galileo, is scheduled to be fully operational in 2018.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

While each of these systems has unique characteristics, all have major aspects in common. Each has a space segment, control segment, and user segment. What is more, all are based on transmitting radio frequency (RF) signals in a one-way fashion from satellites to receivers on and near the Earth's surface. Using measurements obtained from these signals, a GNSS receiver can find its position, velocity, and time (PVT) solution. Moreover, all GNSS systems use the notion of time-of-arrival (TOA) ranging. This requires measuring the signal transit time and the time interval the signal takes to travel between the satellite and the receiver to calculate the receiver-to-satellite range [1]. The transmitter-to-receiver distance can then be obtained by multiplying the signal transit time by the speed of light.

This chapter provides an overview of Global Positioning System (GPS) and GLONASS and their signals. First, it describes the system architecture in terms of the three main segments: control, space, and user. Then, it addresses the new civilian and military GPS signal characteristics, highlighting their significance. Following that, it briefly discusses the GPS measurement error sources. The chapter also covers essential aspects of the GLONASS system, including GLONASS signal characteristics, the GLONASS modernization program, the GLONASS Radio Frequency (RF) plan, pseudorandom (PR) ranging codes, and the intra-system interference navigation message. Finally, advantages of combining both GPS and GLONASS are listed to give the reader insight into the benefits of such integration.

**3. The GPS structure**

by the red dot [4].

**3.1. The space segment**

discussed in greater detail in this section.

estimate position, velocity, and time.

Block IIF ("Follow-on"), and GPS III [10].

As mentioned earlier, the GPS is composite of three segments [7]: the space segment, a constellation of satellites orbiting the Earth at very high altitudes; the control segment, made up of a group of ground control stations; and the user segment, a user's equipment or simply the variety of military and civilian receivers. **Figure 2** illustrates the three segments, which are

**Figure 1.** The concept of position fixing by trilateration using signals from three satellites. The user's position is indicated

GNSSs, Signals, and Receivers

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http://dx.doi.org/10.5772/intechopen.74677

The GPS space segment is made up of a constellation of satellites that continuously broadcasts RF signals to users. In recent years, the US Air Force has operated 32 GPS satellites, of which 24 are available 95% of the time [4]. GPS satellites travel in medium Earth orbit (MEO) at an altitude of approximately 20,200 km, and each circles the Earth twice a day, meaning that the orbital period is approximately 12 h [7]. These satellites are distributed among six equally-spaced orbital planes, each having a target inclination of 55° [6], a satellite distribution that improves the visibility of satellites to GPS users across the globe, thereby enhancing navigation accuracy. GPS satellites broadcast RF signals containing coded information and navigation data, enabling a receiver to calculate pseudoranges and Doppler measurements to

In June 2011, the US Air Force successfully expanded its GPS constellation, known as the "Expandable 24" configuration [9]. Three of the 24 slots were upgraded, and six satellites were repositioned; thus, three additional satellites were added to the constellation. With a 27-slot constellation, GPS improved satellite visibility across the globe. **Table 1** summarizes the features of the current and future generations of GPS satellites, including Block IIA (second generation, "Advanced"), Block IIR ("Replenishment"), Block IIR (M) ('Modernized"),
