Summary: | 碩士 === 國立中央大學 === 通訊工程學系 === 105 === In this thesis, we propose a non-orthogonal multiple access systems based on orthogonal frequency division multiplexing system to reduce the total transmit power. In this system, each subcarrier can be assigned to two users for data transmission and transmits data with a lower power modulation mode. The major problem of non-orthogonal multiple access is the co-channel interference because it shares the same spectrum. Successive interference cancellation is a technique to eliminate the interference derived from the weak user and suffer from the interference from the strong user. Because the system is based on orthogonal frequency division multiple access, primary user is more important than secondary user, we ensure that all assigned subcarriers transmit data to the primary user in the system. The secondary user will transmit data with the primary user on some subcarriers, but it is not possible that the subcarrier is assigned to the secondary user individually. There are two situations in the NOMA allocation, we discuss how the primary and secondary user do resource allocation under conditions of different subcarriers and channel gains. Based on the statement, using the non-orthogonal multiple access allocation result to allocate bits and transmit power lead to the simulation result show that the proposed scheme outperforms the conventional OFDM system.
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