FIELD

The embodiments discussed herein are related to a re-transmission control method, a radio terminal and a radio base station, and more particularly to a technology of appropriately performing re-transmission control in an ultra-reliable and low-latency communication.

BACKGROUND

In recent years, in a radio communication system (also referred to as a mobile communication system) such as a mobile phone system (cellular system), a next generation radio communication technique for achieving higher speed and larger capacity of radio communication has been discussed. For example, the 3rd Generation Partnership Project (3GPP) that is a standardization organization has already developed a specification for a communication standard called Long-Term Evolution (LTE) or a communication standard called LTE-Advanced (LTE-A) based on the radio communication technique of LTE, and continuously has performed work for expansion of the function thereof. For example, standardization of a fifth generation mobile communication system (also referred to as a 5G system) for realizing operation scenarios or contents of technical requirements presented by International Telecommunication Union Radiocommunication sector (ITU-R) has been under discussion.

In the LTE radio communication system (LTE system), hybrid automatic repeat request (HARQ) using a combination of error correction (forward error correction: FEC) and re-transmission control (automatic repeat request: ARQ) is employed. In the 5G system, employing HARQ is examined as a re-transmission control method. In a radio communication system employing HARQ, in a case where an occurrence of a transmission error of an information bit is detected by a receiver, a re-transmission request is performed from the receiver, and re-transmission control is performed from a transmitter in response to the re-transmission request.

In a case of the LTE system, a block as a re-transmission unit in performing re-transmission control is a transport block, and the number of transport blocks in the re-transmission unit is determined in accordance with the number of transmission antennas. For example, in a case where the number of transmission antennas is one, the number of transport blocks is set to 1. In a case where the number of transmission antennas is two, the number of transport blocks is set to 2. A code rate is fixed at 1/3 both in re-transmission and in initial transmission.

Examples of the related art include PTL 1: Japanese Laid-open Patent Publication No. 2010-219818, NPL 1: 3GPP TS 36.211 V14.2.0(2017-03), NPL 2: 3GPP TS 36.212 V14.2.0(2017-03), NPL 3: 3GPP TS 36.213 V14.2.0(2017-03), NPL 4: 3GPP TS 36.300 V14.2.0(2017-03), NPL 5: 3GPP TS 36.321 V14.2.0(2017-03), NPL 6: 3GPP TS 36.322 V14.0.0(2017-03), NPL 7: 3GPP TS 36.323 V14.2.0(2017-03), NPL 8: 3GPP TS 36.331 V14.2.0(2017-03), NPL 9: 3GPP TS 36.413 V14.2.0(2017-03), NPL 10: 3GPP TS 36.423 V14.2.0(2017-03), NPL 11: 3GPP TS 36.425 V14.0.0(2017-03), NPL 12: 3GPP TR 38.801 V14.0.0(2017-03), NPL 13: 3GPP TR 38.802 V14.0.0(2017-03), NPL 14: 3GPP TR 38.803 V14.0.0(2017-03), NPL 15: 3GPP TR 38.804 V14.0.0(2017-03), NPL 16: 3GPP TR 38.900 V14.2.0(2016-12), NPL 17: 3GPP TR 38.912 V14.0.0(2017-03), NPL 18: 3GPP TR 38.913 V14.0.0(2017-03), NPL 19: Y. Saito, Y. Kishiyama, A. Benjebbour, T. Nakamura, A. Li, and K. Higuchi, “Non-orthogonal multiple access (NOMA) for future radio access,” Proc. IEEE VTC2013-Spring, pp. 1-5, Dresden, Germany, June 2013

SUMMARY

According to one aspect of the disclosed technology, a re-transmission control method of downlink data to be transmitted from a radio base station to a radio terminal includes: by the radio terminal, transmitting information regarding decoding performance of the radio terminal to the radio base station; receiving the downlink data from the radio base station; transmitting a re-transmission request of the downlink data to the radio base station in a case where an error in the downlink data is detected; receiving a re-transmission configuration based on the information regarding decoding performance of the radio terminal, from the radio base station in a physical downlink control channel (PDCCH), after transmission of the re-transmission request; receiving the downlink data re-transmitted from the radio base station; and decoding the re-transmitted downlink data in accordance with the re-transmission configuration.

The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention.

