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Soft Decision/Hard Decision

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text2babu

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hard decision vs soft decision

Hello,

Can u give some brief explanation on soft and hard decision in GSM channel decoding techniques, which is better to use and why
 

soft decision hard decision

Hi
Hard/Soft decoding is not for just GSM.
In hard decision decoding, every received samples from channel pass through limiter and output are 1 and 0 (or 1 and -1) then they pass to decoder. But in soft decision decoder received samples from channel pass directly to decoder.
Hard decoding is simpler than soft but soft decoding has a better performanse most of the time.
Hard/Soft decoding is common in convolutional codes.
 

soft demapping

if group of bits is the input, then how does this behave
 

soft decision vs hard decision

For a groups of bits, you need first do the soft-demapping using likelihood ratio testing to get the bits streams, then apply soft decoder for the bits stream. The soft decoder could provide 2-3 dB improvement than hard decoder.
 

soft decision and hard decision

Soft and hard decision is channel characterstic, and u can never send bits directly through channel u must have to do modulation & demodulation ( mapping / demapping stuff mentioned in spweda post)....

if we talk in cellular arena..... Hard/ Soft decision is taken for handover

Hard Handover-- Perform "break before make"-- current channel with the old BS is released b4 the new channel with the new BS is setup. its used in FDMA/TDMA and GSM system

Soft Handover-- Perform " make before break"-- new channel with the new BS is setup in paralled with the current channel with old BS. Both new and old channel are used simultaneously for the communciation. used in IS-95, CDMA2000 and WCDMA
 

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