tailieunhanh - Chapter 16 Wireless WANs: Cellular Telephone and Satellite Networks

Cellular telephony is designed to provide communications between two moving units, called mobile stations (MSs), or between one mobile unit and one stationary unit, often called a land unit. | Chapter 16 Wireless WANs: Cellular Telephone and Satellite Networks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 16. 16-1 CELLULAR TELEPHONY Cellular telephony is designed to provide communications between two moving units, called mobile stations (MSs), or between one mobile unit and one stationary unit, often called a land unit. Frequency-Reuse Principle Transmitting Receiving Roaming First Generation Second Generation Third Generation Topics discussed in this section: 16. Figure Cellular system 16. Figure Frequency reuse patterns 16. AMPS is an analog cellular phone system using FDMA. Note 16. Figure Cellular bands for AMPS 16. Figure AMPS reverse communication band 16. Figure Second-generation cellular phone systems 16. Figure D-AMPS 16. D-AMPS, or IS-136, is a digital cellular phone system using TDMA and FDMA. Note 16. Figure GSM bands 16. Figure GSM 16. Figure Multiframe components 16. GSM is a digital cellular phone system using TDMA and FDMA. Note 16. Figure IS-95 forward transmission 16. Figure IS-95 reverse transmission 16. IS-95 is a digital cellular phone system using CDMA/DSSS and FDMA. Note 16. The main goal of third-generation cellular telephony is to provide universal personal communication. Note 16. Figure IMT-2000 radio interfaces 16. 16-2 SATELLITE NETWORKS A satellite network is a combination of nodes, some of which are satellites, that provides communication from one point on the Earth to another. A node in the network can be a satellite, an Earth station, or an end-user terminal or telephone. Orbits Footprint Three Categories of Satellites GEO Satellites MEO Satellites LEO Satellites Topics discussed in this section: 16. Figure Satellite orbits 16. What is the period of the Moon, according to Kepler’s law? Example Here C is a constant approximately equal to 1/100. The period is in seconds and the distance in kilometers. 16. Example (continued) Solution The Moon is located approximately 384,000 km above the Earth. The radius of the Earth is 6378 km. Applying the formula, we get. 16. According to Kepler’s law, what is the period of a satellite that is located at an orbit approximately 35,786 km above the Earth? Example Solution Applying the formula, we get 16. This means that a satellite located at 35,786 km has a period of 24 h, which is the same as the rotation period of the Earth. A satellite like this is said to be stationary to the Earth. The orbit, as we will see, is called a geosynchronous orbit. Example (continued) 16. Figure Satellite categories 16. Figure Satellite orbit altitudes 16. Table Satellite frequency bands 16. Figure Satellites in geostationary orbit 16. Figure Orbits for global positioning system (GPS) satellites 16. Figure Trilateration 16. Figure LEO satellite system 16. Figure Iridium constellation 16. The Iridium system has 66 satellites in six LEO orbits, each at an altitude of 750 km. Note 16. Iridium is designed to provide direct worldwide voice and data communication using handheld terminals, a service similar to cellular telephony but on a global scale. Note 16. Figure Teledesic 16. Teledesic has 288 satellites in 12 LEO orbits, each at an altitude of 1350 km. Note 16.