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On Spectral Efficiency of Asynchronous GFDMA and SC-FDMA in Frequency Selective Channels

In the fifth-generation mobile communications, futuristic wireless services such as remote surgery, streaming gaming, tactile internet, and augmented reality are envisioned, which require real- time end-to-end communication with near-zero latency. One of the essential enablers of near-zero latency may be asynchronous multiple-access for uplink, in which each user transmits instantaneously without waiting for the next frame to start. Generalized frequency division multiple-access (GFDMA) has been studied as a promising candidate for asynchronous multiple-access, however, conventional single-carrier FDMA (SC-FDMA) can also be adapted in an asynchronous manner for low latency. In this paper, via extensive numerical simulations, the spectral efficiency of GFDMA and conventional SC-FDMA is investigated in the asynchronous scenario with the presence of inter-user interference due to non-zero out-of-band emission of the spectrum. Simulation results show that the superiority between the two techniques is determined depending on the system parameters such as user density, number of guard band subcarriers, signal-to-noise ratio, and etc.