HW 4_Cell_BT_W_9_Sol

# HW 4_Cell_BT_W_9_Sol - Prof. Dzhanidze R. CS M117, HW #4 1...

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Prof. Dzhanidze R. CS M117, HW #4 UNIVERSITY OF CALIFORNIA, LOS ANGELES CS M117 Homework #4 With solution TA ___________________ Theory Section Cellular communications 1. 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? 2. Sometimes when a mobile user crosses the boundary from one cell to another cell, the current cell is abruptly terminated, even though all transmitters and receivers are functioning perfectly. Why? 3. D-AMPS has appreciably worse speech quality than GSM. Is this due to the requirement that D-AMPS be backward compatibility with AMPS, whereas GSM had no such constraint? If not, what is the cause? Frequencies cannot be reused in adjacent cells, so when a user moves from one cell to another, a new frequency must be allocated for the call. If a user moves into a cell, all of whose frequencies are currently in use, the user’s call must be terminated. 1 Each cell has six neighbors. If the central cell uses frequency group A, its six neighbors can use B, C, B, C, B and C respectively. In other words, only 3 unique cells are needed. Consequently, each cell can have 840/3=280 frequencies.

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Prof. Dzhanidze R. CS M117, HW #4 4. Calculate the maximum number of users that D-AMPS can support simultaneously within a single cell. Do the same calculation for GSM. Explain the difference.
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## This note was uploaded on 06/14/2009 for the course CS M117 taught by Professor Dzhanidze during the Spring '09 term at UCLA.

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HW 4_Cell_BT_W_9_Sol - Prof. Dzhanidze R. CS M117, HW #4 1...

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