Quiz2_Solution_Tues_Evening - EE3015 Computer Networks Quiz...

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EE3015 Computer Networks Quiz 2 (Solution) Tues. evening Semester A, 2010/11 1. (9%) The pulse coded modulation is the most common technique to change an analog signal to digital data (digitization). The pulse coded modulation has three steps : 1) The analog signal is sampled. 2) The sampled signal is quantized. 3) The quantized values are encoded as streams of bits. 2. (8%) There is a sudden change of the density between core and cladding in multimode step-index fiber. However, in graded-index fiber, density is highest at the center of the core and decreases gradually to its lowest at the edge. 3. (8%) It is difficult to implement collision detection in a wireless LAN. Two fundamental reasons: 1) the hidden terminal problem makes it is impossible for all communicating stations to “hear” a transmission. 2) When a node is transmitting it cannot also receive at the same time due to the generally very low signal level of a received signal (or receiver shut off when transmitting). 4. (9%) In random access, there is no scheduled time for a station to transmit. Transmission is random among the stations. And no rules specify which station
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Quiz2_Solution_Tues_Evening - EE3015 Computer Networks Quiz...

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