University:
California State University, Northridge
Course:
COMP 528 | Mobile Computing
Academic year:

2016
Views:

114

Pages:

15
Author:

Fradeaniwj4

10 CHAPTER Wireless, Mobile Computing, and Mobile Commerce 1 10.1 Wireless Technologies • Wireless Devices – Dematerialization: “Doing more w less” • Wireless Transmission Media 6 Figure 10.1: Dematerialization with Smartphones 7 Wireless Devices Wireless Devices Provide Three Major Advantages: 1. Small enough to easily carry or wear 2. Sufficient computing power to perform productive tasks. 3. Can communicate wirelessly with the Internet and other devices. 8 Table 10.1 Advantages & Disadvantages of Wireless Media 9 Wireless Transmission Media: Microwave • Advantages of Microware – High bandwidth – Relatively inexpensive • Disadvantages of Microwave – Must have unobstructed line of sight – Susceptible to environmental interference 10 Wireless Transmission Media: Satellite • Advantages of Satellite – High bandwidth – Large coverage area • Disadvantages of Satellite – Expensive – Must have unobstructed line of sight – Signals experience propagation delay – Must use encryption for security 11 Satellites • Three Types of Satellites Circling Earth 1. Geostationary-Earth-Orbit (GEO) • 22,300 miles • 111 miles to 1,243 miles 2. Medium-Earth-Orbit (MEO) 3. Low-Earth-Orbit (LEO) • Footprint • Propagation Delay • Internet over Satellite (IoS) 12 Table 10.2: Three Basic Types of Telecommunications Satellites 13 Satellites: GeostationaryEarth-Orbit (GEO) • • • • • • • 22,300 miles above earth Stationary relative to a point on Earth Transmission delay (.25 seconds) Longest orbital life (many years) Few Needed for Global Coverage Used for Television Signals Most Expensive to Build and Launch 14 Satellites: Medium-EarthOrbit (MEO) • 6,434 miles above earth • Satellites moves relative to a point on Earth • Negligible transmission delay • Moderate orbital life (6-12 years) • Moderate number needed for global coverage • Used for Global Positioning Systems • Less Expensive to Build and Launch 15 Satellites: Low-Earth-Orbit (LEO) • 400-700 miles above earth • Move rapidly in relation to a point on Earth • Negligible transmission delay • Shortest orbital life (low as 5 years) • Large Number Needed for Global Coverage • Least Expensive to Build and Launch 16 ’S ABOUT BUSINESS 10.1 • Skybox Imaging Provides Commercial Images from Earth’s Orbit 1. Describe other applications of Skybox Imaging (not mentioned in the case). 2. Why might the U.S. government object to Skybox Imaging’s business? Provide specific examples in your answer. 3. Might other nations object to Skybox Imaging’s business? If so, which ones, and why? 17 Wireless Transmission Media: Radio • Advantages of Radio – High bandwidth – Signals pass through walls – Inexpensive and easy to install • Disadvantages of Radio – Creates electrical interference problems – Susceptible to snooping unless encrypted 18 Wireless Transmission Media: Infrared • Advantages of Infrared – Low to medium bandwidth • Disadvantages of Infrared – Must have unobstructed line of sight – Used only for short distances 19

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