Most individual data communicating devices require

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2. Most individual data communicating devices require relatively modest datarate support.2.15 How is interference avoided by using frequency division multiplexing? 6). Each signal requires a certain bandwidth centered on its carrier frequency, referred to as a channel . To prevent interference, the channels are separated by guard bands ,
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which are unused portions of the spectrum (not shown in the figure). 2.16 Explain how synchronous time division multiplexing works. synchronous TDM , referring to the fact that time slots are preassigned and fixed. Hence the timing of transmission from the various sources is synchronized. In contrast, asynchronous TDM allows time on the medium to be allocated dynamically. Unless otherwise noted, the term TDM will be used to mean synchronous TDM. A number of signals [ mi ( t ), i = 1, n ] are to be multiplexed onto the same transmission medium. The signals carry digital data and are generally digital signals. The incoming data from each source are briefly buffered. Each buffer is typically one bit or one character in length. The buffers are scanned sequentially to form a composite digital data stream mc ( t ). The scan operation is sufficiently rapid so that each buffer is emptied before more data can arrive. Thus, the data rate of mc ( t ) must at least equal the sum of the data rates of the mi ( t ). The digital signal mc ( t ) may be transmitted directly, or passed through a modem so that an analog signal is transmitted. In either case, transmission is typically synchronous.
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  • Spring '19
  • Wavelength, Bit rate, Time-division multiplexing

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