Data Communications and Computer Networks: A Business User's Approach
Format: PDF / Kindle (mobi) / ePub
Data communications and computer networks are vital in today's business world. Whether your career entails business management, computer programming, system design, or a related area, DATABASE COMMUNICATIONS AND COMPUTER NETWORKS, 7th Edition will give you the thorough understanding you need of basic features, operations, and limitations of different types of computer networks. The Seventh Edition retains many of the elements that made past editions so popular, including readability, coverage of the most current technologies, and a balanced presentation of both technical and practical everyday aspects of data communications. This book offers full coverage of wireless technologies, industry convergence, compression techniques, network security, LAN technologies, VoIP, and error detection and correction.
most explosive areas of growth in recent years has been cell phone networks. Figure 1-10 shows an example of a handheld PDA that, along with making telephone calls, can transmit and receive data. The PDA has a modem installed, which transmits the PDA’s data across the cell phone network to the 12 Chapter 1 cell phone switching center. The switching center then transfers the PDA’s data over the public telephone network or through a connection onto the Internet. Many newer handheld devices have
disadvantages Ê Identify the different data codes and how they are used in communication systems Fundamentals of Data and Signals WE CAN’T SAY we weren’t warned. The U.S. government told us years ago that someday all analog television signals would cease and they would be replaced by the more modern digital signals. Digital signals, we were told, would provide a much better picture. Beginning in 1998, some television stations across the United States began broadcasting digital pictures and
frequency, and phase. A sine wave is used to represent an analog signal, as shown in Figure 2-6. The amplitude of a signal is the height of the wave above (or below) a given reference point. This height often denotes the voltage level of the signal (measured in volts), but it also can denote the current level of the signal (measured in amps) or the power level of the signal (measured in watts). That is, the amplitude of a signal can be expressed as volts, amps, or watts. Note that a signal can
Cellular 94 Chapter 3 systems are widespread and expanding continuously. New technologies such as fourth-generation cell phones and WiMax show promise for expandability. Incidentally, when it comes to wireless technologies, it is important not to confuse the various application areas. Bluetooth and infrared are strictly for short distances. Wi-Fi is designed for local area networks and has a maximum range of a few thousand feet (corresponding to a few hundred meters). WiMax is designed for
to meet users’ needs is called fiber exhaust. For many years, technology specialists saw few ways to resolve fiber exhaust other than by installing additional fiber lines, sometimes at great expense. Now there appears to be an attractive solution that takes advantage of currently installed fiber-optic lines: wavelength division multiplexing. 132 Chapter 5 Wavelength division multiplexing (WDM) multiplexes multiple data streams onto a single fiber-optic line. It is, in essence, a frequency