Computer Networks 5th By Andrew S. Tanenbaum (International Economy Edition)
Language: English
Pages: 960
ISBN: 9332518742
Format: PDF / Kindle (mobi) / ePub
Same Content as US Edition in Different Softcover Design
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3-29. The four Configure- types allow the initiator (I) to propose option values and the responder (R) to accept or reject them. In the latter case, the responder can make an alternative proposal or announce that it is not willing to negotiate certain options at all. The options being negotiated and their proposed values are part of the LCP frames. Figure 3-29. The LCP frame types. The Terminate- codes shut a line down when it is no longer needed. The Code-reject and Protocol-reject codes.
Satellites can be spaced as close as 1 degree. However, another problem exists: rain. Water is an excellent absorber of these short microwaves. Fortunately, heavy storms are usually localized, so using several widely separated ground stations instead of just one circumvents the problem but at the price of extra antennas, extra cables, and extra electronics to enable rapid switching between stations. Bandwidth has also been allocated in the Ka (K above) band for commercial satellite traffic, but.
Frequency bands. Nowadays, each transponder beam is divided into time slots, with various users taking turns. We will study these two techniques (frequency division multiplexing and time division multiplexing) in detail later in this chapter. The first geostationary satellites had a single spatial beam that illuminated about 1/3 of the earth's surface, called its footprint. With the enormous decline in the price, size, and power requirements of microelectronics, a much more sophisticated.
Government should not be in the standardization business, so it left digital to the marketplace. This decision resulted in different equipment manufacturers producing different kinds of mobile phones. As a consequence, the U.S. now has two major incompatible digital mobile phone systems in operation (plus one minor one). Despite an initial lead by the U.S., mobile phone ownership and usage in Europe is now far greater than in the U.S. Having a single system for all of Europe is part of the.
Receivers. None of this will be even mentioned below. Each frequency band is 200 kHz wide, as shown in Fig. 2-43. A GSM system has 124 pairs of simplex channels. Each simplex channel is 200 kHz wide and supports eight separate connections on it, using time division multiplexing. Each currently active station is assigned one time slot on one channel pair. Theoretically, 992 channels can be supported in each cell, but many of them are not available, to avoid frequency conflicts with neighboring.