ch03 - 1 CHAPTER 3 WIRED & WIRELESS...

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Unformatted text preview: 1 CHAPTER 3 WIRED & WIRELESS COMMUNICATION 1.1. 1.1. 1.1. 1.1. Bandwidth, and b andwidth, and b andwidth, and b andwidth, and bandwidth needs of typical users andwidth needs of typical users andwidth needs of typical users andwidth needs of typical users c Signals can be: h Analog – data is in continuous waveforms h Digital – data is in discontinuous pulses (0’s & 1’s) Bandwidth refers to the amount of data that can be transmitted through a given communications channel. For sending and receiving textual data only, a transmission medium with a low bandwidth of 56 Kbps is sufficient. That rate, however, is often painfully slow for the highly graphical Web (unless you're really patient). Exploring the Web is a more pleasant proposition if you use a transmission medium with high bandwidth or a data transfer rate of 128 Kbps or faster. Moving Data: Bandwidth and Modems Bandwidth—the amount of data that can be transmitted through a given communications channel. Analog measured in cycles per second (Hz). Digital measured in bits per second (bps). Broadband—any transmission medium that transports high volumes of data at high speeds. 2 1.2. 1.2. 1.2. 1.2. How modems transform digital compu ow modems transform digital compu ow modems transform digital compu ow modems transform digital computer sign ter sign ter sign ter signals into analog signals als into analog signals als into analog signals als into analog signals Modems are communications devices used to transmit data over telephone lines. On the sending end, the modem uses a process called modulation to transform the computer's digital signals into analog tones that can be conveyed through the telephone system. On the receiving end, the process used is demodulation, whereby the other modem transforms the signal from analog back to digital. 1.3. 1.3. 1.3. 1.3. Transmission media and several tra ransmission media and several tra ransmission media and several tra ransmission media and several transmission methods nsmission methods nsmission methods nsmission methods Twisted pair is inexpensive copper cable used for telephone and data communications. Twisted pair carries data at transfer rates of 1 Kbps. Coaxial cable is a high-bandwidth connecting cable in which an insulated wire runs through the middle of the cable; it has a data transfer rate of 10 Mbps. Fiber-optic cable is a network cable made from tiny strands of glasslike material that transmit light pulses with very high efficiency and can carry massive amounts of data—with a data transfer rate of 1 Gbps. Infrared is a wireless system that includes a transmitter and receiver for sending and receiving signals. No wires are required, but the transmitter and receiver must be in line of sight or the signal is lost. An IRDA port is required for computers to utilize infrared technology. 3 Radio is a wireless transmission medium that carries data via radio frequency signals. Wireless LANs in a home or business are one type of radio technology. Radio signals can be long are one type of radio technology....
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ch03 - 1 CHAPTER 3 WIRED & WIRELESS...

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