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neoflash
Joined: 02 Jul 2005
Posts: 348
Helped: 7
Location: Asia
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 30 Jan 2006 10:33 duo-binary signal coding SNR requirement |
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Why duo-binary signal coding SNR requirement is 2.5dB more than normal binary coding?
According to my understanding, duo-binary coding will have 3 voltage level, binary code will only have two.
Thus the SNR ratio between them are 2/3, the difference should not be 2.5dB, it should be 3.5dB.
Any inputs?
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mehtesham
Joined: 14 Nov 2005
Posts: 111
Helped: 12
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| 01 Feb 2006 9:37 Re: duo-binary signal coding SNR requirement |
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2.5dB more transmit powre is needed for duobinary for having the same error probability as binary.
as Pe of duobinary and binary are known:
Pe(duobinary)=Pe(binary) ---> St(duobinary)~=1.8*St(binary) ---> St(duo,dB)~=2.5dB+St(binary,dB)
St is transmit power.
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neoflash
Joined: 02 Jul 2005
Posts: 348
Helped: 7
Location: Asia
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| 01 Feb 2006 12:29 duo-binary signal coding SNR requirement |
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| where is 1.8 coming from?
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mehtesham
Joined: 14 Nov 2005
Posts: 111
Helped: 12
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| 01 Feb 2006 16:11 Re: duo-binary signal coding SNR requirement |
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you know:
St(duo)/St(bin)=[(4*Q^-1(2*Pe/3)/pi)^2]/[(Q^-1(Pe))^2]
Q^-1(x) is inverse of Q(x) function,pi=3.14
calculating numerically (from table) :
for example : Pe=10^-3 then Q^-1(2/3*10^-3)=3.26 , Q^-1(10^-3)=3.09 you have (4*3.26/pi)^2/(3.09)^2~=1.8
for Pe=10^-4,... you will get about 1.8
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