Tutorial_Sheet_5 - ET4254 Communications and Networking 1...

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Unformatted text preview: ET4254 Communications and Networking 1 Tutorial Sheet 5 Short Questions: 1. Why is multiplexing so cost-effective? 2. How is interference avoided by using frequency division multiplexing? 3. What is echo cancellation? 4. Define upstream and downstream with respect to subscriber lines. 5. Explain how synchronous time division multiplexing (TDM) works. 6. Why is a statistical time division multiplexor more efficient than a synchronous time division multiplexor? 7. Using Table 1 as a guide, indicate the major difference between North American and international TDM carrier standards. 8. Using Figure 1 as a guide, indicate the relationship between buffer size and line utilisation. Dr. Kevin Murphy University of Limerick ET4254 Communications and Networking 1 Tutorial Sheet 5.1 Table 1: North American and International TDM Carrier Standards North American International (ITU-T) Designation Number of Voice Channels Data Reate (Mbps) Level Number of Voice Channels Data Reate (Mbps) DS-1 24 1,544 1 30 2,048 DS-1C 48 3,152 2 120 8,448 DS-2 96 6,312 3 480 34,368 DS-3 672 44,736 4 1920 139,264 DS-4 4032 274,176 5 7680 565,148 ET4254 Communications and Networking 1 Tutorial Sheet 5 Dr. Kevin Murphy University of Limerick ET4254 Communications and Networking 1 Tutorial Sheet 5.2 ET4254 Communications and Networking 1 Tutorial Sheet 5 Problems: 1. The information in four analog signals is to be multiplexed and transmitted over a telephone line that has 400- to 3100Hz-bandpass. Each of the analog baseband signals is bandlimited to 500Hz. Design a communications system (block diagram) that will allow the transmission of these four sources over the telephone channel using a. Frequency division multiplexing with SSB (single sideband) subcarriers b. Time division multiplexing using PCM: assume 4-bit samples Show the block diagrams of the complete system, including the transmission, channel, and reception portions. Include the bandwidth of the signals at the various points in the system....
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Tutorial_Sheet_5 - ET4254 Communications and Networking 1...

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