Pulse Interval Modulation-Advantages, disadvantages, comparison
This page describes Digital Pulse Interval Modulation (PIM) basics, PIM advantages and PIM disadvantages. It mentions comparison between PIM, PCM and PPM.
As we know FSO (Free Space Optics) based solutions are used in fiber optic communication systems.
Following pulse modulation schemes are employed which can provide higher average power efficiency
at the expense of higher bandwidth requirement.
• On-OFF Keying (OOK)
• Pulse Position Modulation (PPM)
• Pulse Interval Modulation (PIM)
It stands for On-Off Keying which is simple modulation scheme based on intensity modulation.
In this scheme, '0' is indicated by zero intensity and '1' is indicated by positive intensity.
Refer difference between OOK vs ASK vs FSK >> for more information.
As mentioned PPM is short form of Pulse Position Modulation in which relative position of pulse is
proportional to amplitude of the modulating signal. It is similar to phase modulation (PM).
Refer advantages and disadvantages of pulse modulation schemes such as PAM vs PWM vs PPM >> for more information.
What is Pulse Interval Modulation (PIM)?
In this modulation scheme, data bits (in pairs) are encoded as number of time intervals between successive pulses as shown in the figure below.
Image Courtesy: slideplayer.com
The figure-1 depicts digital PIM (Pulse Interval Modulation) waveform. It also shows table with digital bit pairs and their pulse representations.
Benefits or advantages of Pulse Interval Modulation (PIM)
Following are the benefits or advantages of Pulse Interval Modulation (PIM):
➨It offers high APE (Average Power Efficiency) compare to OOK modulation.
➨There is no symbol level synchronization is required.
➨It offers high information capacity.
➨It offers simple receiver architecture.
Drawbacks or disadvantages of Pulse Interval Modulation (PIM)
Following are the drawbacks or disadvantages of Pulse Interval Modulation (PIM):
➨It has APE (Average Power Efficiency) lower than PPM modulation.
Comparison between PIM, PCM and PPM
Following points summarize comparison between PIM, PCM and PPM modulation types.
• PCM : In PCM, the analog speech waveform is sampled and converted directly into a multibit digital code by an Analog to Digital converter. In PCM samples are represented by digital binary form. Read more on advantages and disadvantages of PCM modulation >>.
• PPM : In PPM, relative position of pulse is proportional to amplitude of the modulating signal.
• PIM : In PIM, data bits (in pairs) are encoded as number of time intervals between successive pulses as shown in the table above.
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