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OOK is on off keying
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Power present means 1 , no power means 0
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Each bit 0 or 1 is supported by modulation symbol
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It’s simple
- But not suitable for high capacity Links
- The spectral efficiency is very low
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OOK depends on amplitude to represent the information
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Phase is zero
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To increase the capacity of link we have to use more complex modulation types
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In M ary modulation we use amplitude and phase
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This type is more complex than OOK and higher sensitive to noise
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But it’s spectral efficiency is higher
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Spectral efficiency means higher capacity and higher bits can be transmitted per bandwidth of channel
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If M is the number of symbols
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Then we can tramsmit 3 bits per symbol
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In 16 Qam modulation we have 16 symbol
- So we have 4 bits per symbol
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In 74 Qam modulation we have 64 symbol
- 6 bits / symbol
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Ss capacity increasing, number of bits per symbol increase , number of symbols increasing
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Then the distance between symbols in I - Q space is small, then the decision area is too small
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So there’s not too much margin for errors
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