[...]... exactly how wireless communication will fit into the final picture, even if a field as dynamic as this can be imagined to have a final state Some people (many of whom seem to work for wireless phone companies) have suggested that eventually wireless phones will replace wireline equipment, and everyone will have one phone (with one number) which they will carry with them everywhere Wired communication. .. is very serious development work underway involving high-bandwidth wireless communication for world-wide web access from portable devices, for instance If it is unclear even to the experts what the future holds, we must be careful in our predictions This much is certain though: wireless communication will be a large part of the total communication picture, and a knowledge of the technologies involved... to remember from this chapter are: ( Any wireless communication system requires a transmitter and a receiver connected by a channel ( Simplex communication systems allow communication in one direction only Half-duplex systems are bidirectional, but work in only one direction at a time Full-duplex systems can communicate in both directions simultaneously ( Most wireless networks are variations of the... them on a power-frequency plane frequency-division multiplexing combining of several signals into one communication channel by assigning each a different carrier frequency full-duplex communication two-way communication in which both terminals can transmit simultaneously half-duplex communication two-way communication system in which only one station can transmit at a time handoff transfer of a call in... consistent with reliable communication, thereby allowing frequencies to be reused at quite small distances Such schemes can use spectrum very efficiently 28 ! CHAPTER 1 ' 1.7 ' Summary “Convergence” and Wireless Communication There has been much talk recently about “convergence,” the merger of all kinds of previously separate electronic systems, for example, telephony (both wireline and wireless) , broadcast... real-time communication is required—in a telephone call, for instance The reader may have experienced this tradeoff of time for bandwidth in downloading an audio or video file from the internet If the bandwidth of the connection is low, such a file may take much longer to download than it does to play Frequency Reuse Spectrum space in wireless systems is nearly always in short supply Even with the communication. .. CONCEPTS ! 29 ( The ratio of signal power to noise power is one of the most important specifications for any communication system Thermal noise is the most important type of noise in most wireless systems ( The frequency domain is useful for the observation and understanding of both signals and noise in communication systems ( Many signals can be analyzed in the frequency domain with the aid of Fourier series... MHz (cell phone range) (b) 1.9 GHz (Personal Communication Systems range) (c) 28 GHz (used for Local Multipoint Distribution Systems (LMDS) for local delivery of television signals by microwave) SOLUTION For all of these the method is the same The problem is repeated to give the reader a feeling for some of the frequencies and wavelengths used in wireless communication Simply rewrite Equation (1.12)... phones? 6 Explain the differences among simplex, half-duplex, and full-duplex communication 7 Identify each of the following communication systems as simplex, half-duplex, or full-duplex (a) cordless telephone (b) television broadcast (c) intercom with push-to-talk bar 8 Why is it necessary to use a high-frequency carrier with a radio communication system? 9 Name the three basic modulation methods 10 Suppose... Medium Waves frequency ranges and their associated wavelength ranges Note that microwaves and millimeter waves are wavelength designations and fit only approximately into the frequency designations Wireless communication as described in this book occupies mainly the VHF, UHF, and SHF portions of the spectrum Lower-frequency systems need inconveniently large antennas and involve methods of signal propagation . to: ( Explain the nature and importance of wireless communication. ( Outline the history of wireless communication. ( Explain the necessity for modulation in a radio communication system. ( Outline the. of full-duplex communication, however. Figure 1.3 shows a half-duplex communication system. Wireless Networks The full- and half-duplex communication systems shown so far involve communication. borderline applications that are called wireless without falling exactly into the above definition. Wireless communication is the fastest-growing part of the very dynamic field of electronic communication. It is