December 2014
Journal of Theoretical & Applied Information Technology;12/31/2014, Vol. 70 Issue 3, p496
Academic Journal
Frequency Division Multiple Access (FDMA) is one of the important features of Long Term Evolution Advanced (LTE-A). For LTE-A downlink, Orthogonal FDMA (OFDMA) scheme is used to provide frequency orthogonality. Whereas, for uplink, Signal Carrier FDAM (SC-FDMA) is preferred since it provides improved PAPR performance over OFDMA. Interleaved FDMA (IFDMA) and Localized FDMA (LFDMA) are forms of SC-FDMA usually used in LTE-A. User subcarrier allocation method is the main distinction between IFDMA and LFDMA schemes. Users are allocated destributed frequency carriers in IFDMA while they are allocated localized carriers in LFDMA. Whereas IFDMA scheme provides better PAPR performance over LFDMA scheme, the latter has lower complexity requirements. In this paper a new user subcarrier allocation scheme is introduced. The proposed scheme provides a variable interleaved allocation of subcarriers in the bandwidth, hence it is named Generalized FDMA (GFDMA). This variable interleaved allocation scheme made the transition from IFDMA to LFDMA to be seamless. Theoritical derivation of the proposed scheme shows that both IFDMA and LFDMA are subclasses of GFDMA. Simulation results of the proposed GFDMA show that the signal PAPR calculated varies according to the interleave level selected. The simulation has been conducted for different QAM modulation schemes and bandwidths. In all the cases, GFDMA PAPR performance is in good match to the calculated IFDMA and LFDMA PAPR. Moreover, further enhancement in GFDMA PAPR is achieved as the number of users in a given bandwidth increased.


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