| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 106 === Non-orthogonal multiple access (non-OMA) schemes can potentially achieve capac-
ities higher than those of existing orthogonal MA schemes by allowing multi-user or
multi-stream superposition transmission. Unlike OMA that assign each user to an or-
thogonal channel, non-OMA schemes allow multiple user or multiple data stream to
share the same channel. The performance of such a system depends on the design of
multiuser multidimensional signal and the associated receiver. The receiver needs to sup-
press the superposition-induced co-channel multiuser interference (MUI) with a proper
multi-user detector (MUD) so that the superimposed data streams can be separated.
In this thesis, we present a class of spread spectrum MA schemes that combine inter-
leaved coding, transform domain spreading and multidimensional modulation. In addi-
tion to the user-dependent sparse spreading over the available time-frequency resources,
extra data-dependent spreading is performed locally on each modulated symbol's spread
chips (resource units). The local spreading (scrambling) re-shapes or re-labels the mul-
tiple dimensional constellation that helps improving 'sub-codeword' distance and sepa-
rating co-channel symbols and improving the spectral eciency. Numerical results show
that, by using an iterative receiver structure, our scheme outperforms some known MA
schemes in both AWGN and frequency selective fading channels.
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