Principles of Information Systems, 13
th
Edition
so the line of sight between the transmitter and receiver must be unobstructed.
Typically, microwave stations are placed in a series—one station receives a
signal, amplifies it, and retransmits it to the next microwave transmission tower.
Such stations can be located roughly 30 miles apart before the curvature of the
Earth makes it impossible for the towers to “see” one another. Because they are
line-of-sight transmission devices, microwave dishes are frequently placed in
relatively high locations, such as mountains, towers, or tall buildings.
7.The first generation (1G) of wireless communications standards originated in the
1980s and was based on analog communications. The second-generation (2G)
networks were fully digital, superseding 1G networks in the early 1990s. With 2G
networks, phone conversations were encrypted, mobile phone usage was
expanded, and short message services (SMS)—or texting—was introduced. 3G
wireless communications supports wireless voice and broadband speed data
communications in a mobile environment at speeds of 2 to 4 Mbps. Additional
capabilities include mobile video, mobile e-commerce, location-based services,
mobile gaming, and the downloading and playing of music.
4G broadband mobile wireless delivers more advanced versions of enhanced
multimedia, smooth streaming video, universal access, and portability across all
types of devices; eventually 4G will also make possible worldwide roaming. 4G
can deliver 3 to 20 times the speed of 3G networks for mobile devices such as
smartphones, tablets, and laptops.
8.Network-management software is software that enables a manager on a
networked desktop to monitor the use of individual computers and shared
hardware (such as printers), scan for viruses, and ensure compliance with
software licenses. Network-management software also simplifies the process of
updating files and programs on computers on the network—a manager can make
changes through a communications server instead of having to visit each
individual computer. In addition, network-management software protects software
from being copied, modified, or downloaded illegally. It can also locate
communications errors and potential network problems.
Mobile device management (MDM) software manages and troubleshoots mobile
devices remotely, pushing out applications, data, patches, and settings. With the
software, a central control group can maintain group policies for security, control
system settings, ensure malware protection is in place for mobile devices used
across the network, and make it mandatory to use passwords to access the
network.
9.J.C.R. Licklider of MIT first proposed a global network of computers in 1962,
and moved over to the Defense Advanced Research Projects Agency (DARPA) in
late 1962 to head the work to develop it. Leonard Kleinrock of MIT and later
UCLA developed the theory of packet switching, which was to form the basis of
Internet connections. Lawrence Roberts of MIT connected a Massachusetts