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Kyoto University Develops New Highly Spectrum-Efficient Communication Scheme UTW-OFDM for 5G Mobile Communication System

[3rd March 2016]

The research group of Prof. Keiichi Mizutani and Prof. Hiroshi Harada at the Graduate School of Informatics, Kyoto University, Japan, has developed a new highly spectrum-efficient communication scheme and system, dubbed UTW-OFDM (Universal Time-domain Windowed OFDM), with low out-of-band emission in order to improve spectrum efficiency for the 5th-generation mobile communication system (5G) that will be introduced from 2020 or later. The developed system apply flexible parameterized time-domain windowing with low complexity and can reduce the out-of-band emission by more than 30 dB comparing with the conventional CP-OFDM that is applied to the 4G LTE system. The UTW-OFDM achieves more highly dense channel allocation and it is expected that the more highly communication quality can be provided to the large number of user terminals as the same time.

Background

The 5th-generation mobile communication system (5G) that will be started from 2020 or later has been developed internationally toward more highly efficient and multipurpose communications such as very-high speed communications and low-speed high-density sensor communications. However, frequency resources suitable for mobile communications have become starved. Therefore, the development of the high spectrum-efficient system maintaining backward compatibility with the conventional 4G LTE system is an urgent matter.

Achievements

The research group of Prof. Keiichi Mizutani and Prof. Hiroshi Harada, has developed a new highly spectrum-efficient communication scheme and system, dubbed UTW-OFDM (Universal Time-domain Windowed OFDM), with low out-of-band emission in order to improve spectrum efficiency. In conventional systems, the filtering process is a major factor in baseband to suppress the out-of-band emission dramatically. However, the complexity of the filtering process becomes very high.

In the proposed system, only time-domain windowing processing with low complexity is applied to the transmitter. The parameters of the time-domain windowing coefficients, i.e. windowing function type and size, can be variable flexibly for multipurpose use with multi-requirement systems. In the proposed UTW-OFDM system, large window size is applied to reduce the out-of-band emission dramatically.

This time, the characteristics of transmission signals of the proposed UTW-OFDM with LTE parameters were experimentally evaluated by using signal generator and spectrum analyzer. Additionally, bit-error-rate characteristics of the proposed UTW-OFDM with LTE parameters including convolutional turbo coding technology were evaluated by computer simulations. As a result, it was shown that the proposed system can achieve a dramatic out-of-emission suppression performance (more than 30 dB improvement comparing with the conventional CP-OFDM of the LTE) and fulfill the physical layer requirement of LTE.

» Figure 1 : Experimentally measured spectrum of the proposed UTW-OFDM scheme with 5 MHz mode LTE parameters.

Future prospects

These results of the research will be presented in IEICE mobile communications workshop (From 2nd to 4th March, Tokyo). Our research group will conduct field experiments of the proposed UTW-OFDM on the developing platform and make contributions for the 5G system development.

Acknowledgement:
This research was conducted under a contract of R&D for radio resource enhancement, organized by the Ministry of Internal Affairs and Communications, Japan.

[Technical Contact] Keiichi Mizutani, Hiroshi Harada Digital Communications Laboratory, Graduate School of Informatics, Kyoto University Tel: +81-75-753-5317, Fax: +81-75-753-4982 E-mail: contact@dco.cce.i.kyoto-u.ac.jp