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Distinguish Between Link and Channel in Multiplexing

1. In multiplexing, a link refers to the physical path that carries transmissions, while a channel refers to the portion of a link dedicated to a single transmission between two points. One link can contain multiple channels. 2. Spread spectrum techniques spread transmitted signals across a wide frequency spectrum. The two main techniques are frequency hopping spread spectrum (FHSS), which shifts carriers across channels pseudorandomly, and direct sequence spread spectrum (DSSS), which combines data with a high-rate bit sequence. 3. Frequency division multiplexing (FDM) divides the frequency spectrum into multiple non-overlapping bands, with each band carrying a separate signal. Time division multiplexing (TDM) allows multiple

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3K views7 pages

Distinguish Between Link and Channel in Multiplexing

1. In multiplexing, a link refers to the physical path that carries transmissions, while a channel refers to the portion of a link dedicated to a single transmission between two points. One link can contain multiple channels. 2. Spread spectrum techniques spread transmitted signals across a wide frequency spectrum. The two main techniques are frequency hopping spread spectrum (FHSS), which shifts carriers across channels pseudorandomly, and direct sequence spread spectrum (DSSS), which combines data with a high-rate bit sequence. 3. Frequency division multiplexing (FDM) divides the frequency spectrum into multiple non-overlapping bands, with each band carrying a separate signal. Time division multiplexing (TDM) allows multiple

Uploaded by

ZAINALABDEN ALNAWA
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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1- Distinguish between link and channel in multiplexing

In multiplexing, the word link refers to the physical path. The word channel refers to the
portion of a link that carries a transmission between a given pair of lines. One link can
have many (n) channels
2- Define spread spectrum and its goal List the two techniques
and explain each of them with diagram.
- Spread spectrum is a technique used for transmitting radio or telecommunications
signals. The term refers to the practice of spreading the transmitted signal
- his goal: occupy the frequency spectrum available for transmission.
- The major spread spectrum techniques are :
1. Frequency Hopping Spread Spectrum (FHSS) (Analog) : is a method of transmitting radio signals
by shifting carriers across numerous channels with pseudorandom sequence which is already known to the sender and
receiver.
2. Direct Sequence Spread Spectrum Synchronous (DSSS) (Digital) : is a transmission
technology used in local area wireless network transmissions. In this technology, a data signal at the sending station is
combined with a high data rate bit sequence, which divides user data based on a spreading ratio.
3- Difference between FDM,TDM and WDM

4- Define FHSS and explain with example how it achieves


bandwidth spreading
The frequency hopping spread spectrum (FHSS) technique uses M different carrier
frequencies that are modulated by the source signal. At one moment, the signal
modulates one carrier frequency; at the next moment, the signal modulates another
carrier frequency.
5- Define DSSS and explain with example how it achieves
bandwidth spreading
The direct sequence spread spectrum (DSSS) technique expands the bandwidth of the
original signal. It replaces each data bit with n bits using a spreading code." With
telecommunications, primary-succession propagate variety (DSSS) is usually a intonation
process.
6- Difference between Synchronous and statistical TDM.
7- assume that a voice channel occupies a bandwidth of 4 khz.
we need to multiplex 10 voice channels with guard bands of 500
HZ using FDM . calculate the required bandwidth

8- Draw and explain time vs frequency diagram for FDM,TDM


and WDM
9- Advantage and disadvantage of FDM,TDM and WDM.
Advantage of FDM Disadvantage of FDM
•It does not need synchronization between its transmitter and
1. The communication channel must have a very large
receiver.
bandwidth.
•Frequency division multiplexing (FDM) is simpler and easy
demodulation.
2. Large number of modulator and filter are required.
•Due to slow narrow band fading only one channel gets
affected.
3. FDM suffers from the problem of crosstalk.
•It is used for analog signals.
•A large number of signals (channels) can be transmitted
4. All the FDM channels get affected due to wideband fading.
simultaneously.

Advantage of WDM Disadvantage of WDM


➨Full duplex transmission is possible.
➨Signals can not be very close.
➨Easier to reconfigure.
➨Light wave carrying WDM are limited to 2-point circuit.
➨Optical components are similar and more reliable.
➨Scalability is a concern
➨It provides higher bandwidth.
➨Cost of system increases with addition of optical components.
➨This could be the best approach as it is simple to
➨(WDM in PON:) Inefficiency in BW utilization, difficulty in
implement.
wavelength tuning, difficulty in cascaded topology
➨High security
Advantage of TDM Disadvantage of TDM
•Time division multiplexing systems are more flexible than •Synchronization is required in time division multiplexing.
frequency division multiplexing. •Complex to implement.
•Time division multiplexing circuitry is not complex. •Due to slow narrowband fading, all the TDM channels may get
•Problem of cross talk is not severe. wiped out.
•Full available channel bandwidth can be utilized for each
channel.

10- Numerical based on FDM and TDM

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