In a typical mobile phone system with hexagonal cells, it is forbidden to reuse a frequency band in an adjacent cell. If 840 frequencies are available, how many can be used in a given cell?
Answer to relevant QuestionsThe actual layout of cells is seldom as regular that as shown in Fig. 2-41. Even the shapes of individual cells are typically irregular. Give a possible reason why this might be.Suppose that A, B, and C are simultaneously transmitting 0 bits, using a CDMA system with the chip sequences of Fig. 2-45(b). What is the resulting chip sequence?Using the spectral allocation shown in Fig. 2-48 and the information given in the text, how many Mbps does a cable system allocate to upstream and how many to downstream?Can you think of any circumstances under which an open-loop protocol, (e.g., a Hamming code) might be preferable to the feedback-type protocols discussed throughout this chapter?Data link protocols almost always put the CRC in a trailer rather than in a header. Why?
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