Masashi Iwabuchi

5G Field Trials: OFDM-Based Waveforms and Mixed Numerologies

Service diversity is expected in the upcoming fifth-generation (5G) cellular networks, which poses great challenges to the underlying waveforms to accommodate heterogeneous service requirements in a flexible way. By dividing the bandwidth into several subbands, each having a different numerology, this paper reports a field trial in time division duplex downlink conducted on a configurable test bed in a real-world environment for the performance evaluations of orthogonal frequency-division multiplexing (OFDM)-based 5G waveform candidates, i.e., cyclically prefixed OFDM (CP-OFDM), windowing OFDM (W-OFDM), and filtered OFDM (f-OFDM), in the presence of mixed numerologies. Field trial results confirm the feasibility of mixed numerologies and reveal the impact of several important system parameters, e.g., guard bandwidth, data bandwidth, signal-to-noise ratio (SNR), and transmit power. The results also suggest that f-OFDM outperforms CP-OFDM and W-OFDM in terms of both the spectrum efficiency and robustness in a high SNR regime, and the gain increases with a higher inter-numerology out-of-band interference. In some specific scenarios, ideal spectrum utilization can be realized by f-OFDM which completely removes the guard band.

5G Field Experimental Trial on Frequency Domain Multiplexing of Mixed Numerology

This paper presents a field experimental trial on frequency-domain multiplexing of a mixture of multiple numerologies. The goal is to support diverse applications and services in the fifth generation mobile communications (5G) system. Frequency-domain multiplexing of mixed numerology has been discussed for 5G in order to flexibly support the variety of requirements introduced by future applications. However, frequency-domain multiplexing of mixed numerology causes inter sub-band interference. In this paper, we apply filtered-orthogonal frequency division multiplexing (f-OFDM), which is a new waveform, in order to reduce the inter sub-band interference. Through the field trial, we show that f-OFDM realizes mixed numerology while reducing the impact from inter sub-band interference compared to conventional cyclic prefix OFDM. The field trial results show that f-OFDM has no throughput degradation when using more than one guard subcarrier.