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Maximizing the spectral efficiency of coded CDMA under successive decoding

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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

g (dB)

R (bit/symbol)

Rate-threshold for LDPC codes with QPSK modulation

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0 1 2 3 4 5 6

0 5 10 15 20

ρ (bit/s/Hz)

β (user/chip)

CDMA, QPSK vs. Gaussian inputs

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