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Configurable Soft Output Demapper

Noesis Technologies Soft Output Demapper is a structural element of any modern telecom system. The receiver extracts the phase and magnitude of the carrier signal. Subsequently a decision must be taken on the actual transmitted bits. Due to channel noisy conditions, the received signal has been distorted and there are positional errors on the constellation points. The ntSOD Soft Output Demapper IP Core implements the LLR (Log Likelihood Ratio) algorithm to convert the received distorted modulated signal from its complex I, Q form to a bit stream. It identifies the actual transmitted symbol bits and assigns to each bit a level of confidence in the format of a soft value. It sup-ports various modulation levels such as BPSK, QPSK, 16 QAM and 64 QAM. This soft-bit information can be subsequently used during ECC decoding process by a soft-input ECC decoder such as Viterbi Decoder. Soft decision ECC decoding can provide a coding gain of 2 dB for 3 soft-bits per encoded bit or 2.2 dB for 4 soft bits per encoded bit when compared with hard decision ECC decoding. The soft-bit infor-mation can be configured in sign-magnitude or 2’s complement format.