Yuta Sagae

Bio: Yuta Sagae is an academic researcher from NTT DoCoMo. The author has contributed to research in topics: Base station & Communications system. The author has an hindex of 12, co-authored 76 publications receiving 480 citations.

Mobile communication method, wireless base station, and mobile station

Abstract: An objective is to improve communication quality by reducing an insertion loss or the like of a diplexer inserted to reduce a leakage from an uplink band to a downlink band in different bands. A mobile communication method according to the present invention includes the steps of: transmitting simultaneous transmission capability information from a mobile station UE to a radio base station eNB, the simultaneous transmission capability information indicating whether or not the mobile station UE can transmit uplink data signals via multiple carriers in the same sub-frame while performing uplink CA; performing scheduling for the mobile station UE by the radio base station eNB on the basis of the simultaneous transmission capability information; and performing communication by the mobile station UE on the basis of the scheduling information.

Component Carrier Management for Carrier Aggregation in LTE-Advanced System

Abstract: This paper focuses on investigating appropriate management of Component Carriers(CCs) in carrier aggregation( CA) system, which is identified as one of the most distinct features of 4G systems including Long Term Evolution- Advanced (LTE-A). An LTE-A user equipment (UE) is allowed to concurrently utilize multiple carriers, which leads to scalable increase in user throughput. However, in certain circumstances, aggregating entire available carriers for a UE is not meaningful due to probably low channel quality or high traffic load in some of the CCs. Therefore, how to make good use of multiple carriers in real deployment scenarios is an important issue. Based on the analysis of resource allocation across multiple carriers in Layer-2, two CC management methods in Layer- 3 are proposed. The proposed method is shown by simulation results to be effective in providing comparable user throughput with lower implementation complexity, as compared to solely ingenious resource allocation.

Radio communication system, user terminal and radio communication method

Abstract: The present invention is designed to provide a radio communication system, a user terminal and a radio communication method that make it possible to monitor communication quality adequately even when a new radio resource structure is employed. A radio communication system is provided, which transmits downlink control information from a radio base station to a user terminal by using an enhanced downlink control channel that is frequency-division-multiplexed with a downlink shared data channel, and which also monitors downlink quality based on the received quality of downlink reference signals that are transmitted from the radio base station to the user terminal, and, in this radio communication system, the user terminal determines radio link failures by comparing the received quality of the downlink reference signals transmitted from the radio base station, against one or both of first criteria, which are constituted of two thresholds that correspond to predetermined block error rates of a downlink control channel, and second criteria, which are constituted of two thresholds that are different from the two thresholds of the first criteria.

Base station, mobile station, measurement result information control method

Abstract: A base station, which uses a plurality of component carriers to perform communications, comprises: a measurement result receiving unit that receives, from each of a plurality of mobile stations, a measurement result of reception environment; a determining unit that determines, based on the received measurement result, whether or not a change will occur in a primary or subsidiary cell allocated to the mobile station; and an initializing unit that initializes information including the measurement result of reception environment acquired from the mobile station of the component carrier corresponding to the primary or subsidiary cell where a change will occur.

Investigation on Interference Rejection Combining Receiver for Space–Frequency Block Code Transmit Diversity in LTE-Advanced Downlink

Abstract: The interference rejection combining (IRC) receiver, which can strictly suppress intercell interference based on the minimum mean square error (MMSE) criteria, is effective in improving cell-edge user throughput. When assuming the Long Term Evolution (LTE) or LTE-Advanced downlink and open-loop transmit diversity employing the space-frequency block code (SFBC) using Alamouti coding, the IRC receiver must detect the Alamouti coded signals and suppress the interference signals using a couple of received signals in the frequency domain at the same time. To achieve this, the IRC receiver weight matrix, which consists of the channel matrix of the serving cell and the statistics of the covariance matrix, including the interference and thermal noise components, must be extended in the frequency domain, i.e., due to the effect of Alamouti coding, in addition to the spatial domain. These extended matrices can be estimated using the downlink reference signals (RSs) from the serving cell. However, some elements, including the effect of Alamouti coding in the extended covariance matrix, cannot be estimated using a practical estimation scheme that subtracts the replica symbols of the serving cell generated by the estimated channel matrix and the known RS sequence from the received RSs of the serving cell. This is because the RSs in LTE/LTE-Advanced are not transmitted using two adjacent subcarriers. This paper investigates the statistics of these unknown elements and proposes appropriate values, specifically inserting zero values, for these elements assuming the LTE/LTE-Advanced downlink. The results of simulations show that the IRC receiver using the proposed scheme, which has two receiver antenna branches, suppresses the intercell interference and improves the throughput by more than 10% compared with that for the conventional maximal ratio combining (MRC) receiver when a cell-edge environment is assumed.

User terminal, radio base station and radio communication method

Abstract: The present invention is designed to provide a user terminal, a radio base station and a radio communication method of novel structures that can achieve a good communication environment. A radio base station non-orthogonal-multiplexes downlink signals for a plurality of user terminals over a given radio resource, a user terminal having received the downlink signals for the plurality of user terminals decodes downlink signal for another user terminal, judges whether or not the downlink signal for the other user terminal has been successfully received, based on the decoding result of the downlink signal, reports a judgement result as to whether or not the downlink signal for the other user terminal has been successfully received and a judgement result as to whether or not a downlink signal for the user terminal has been successfully received, to the radio base station, and then the radio base station executes retransmission control of downlink signals based on reports from the user terminal.

Radio base station, user terminal, and radio communication method

Abstract: The present invention is designed to improve spectral efficiency in a radio communication system which can use non-orthogonal multiple access (NOMA). Steps are provided in which a radio base station configures one of a plurality of transmission mode including a first transmission mode, which groups a plurality of transmission methods including a transmission method to employ non-orthogonal multiple access (NOMA) and multiple-user multiple-input and multiple-output (MU-MIMO), and a second transmission mode, which groups a plurality of transmission methods including a transmission method to employ this NOMA and open-loop transmit diversity, and transmits a downlink signal for this user terminal based on the configured transmission mode.

User terminal, wireless base station, and wireless communication method

Abstract: In order that a user terminal properly identifies a connection cell in a radio communication system (LTE-U) for operating LTE in an unlicensed band, a user terminal for communicating with a radio base station in an unlicensed band is provided with a detection section that detects a synchronization signal transmitted from a radio base station using a dummy cell ID used in common among a plurality of radio base stations, an estimation section that performs channel estimation using a reference signal, and a reception processing section that performs reception processing of system information transmitted from a radio base station using a channel estimation result.

Terminal device, base station device, and communication method

Abstract: A first UL-DL configuration configured by using a common RRC message is set; an antenna port for one enhanced physical downlink control channel in a subframe is set based on whether or not the subframe is a predetermined special subframe in the first UL-DL configuration; and in a case where a second UL-DL configuration indicated by downlink control information which is transmitted on a physical downlink control channel is set, an antenna port for one enhanced physical downlink control channel in the subframe is set based on whether or not the subframe is the predetermined special subframe in the second UL-DL configuration.

Selective specific absorption rate adjustment

Abstract: An electronic device provides a capability of distinguishing between human tissue and a non-human object in proximity of a transmission source. In this manner, transmission power adjustments to the transmission source can be made selectively, depending on whether human tissue or a non-human object is detected in the proximity of the RF transmitter. Distinguishing between human tissue and other non-human-tissue objects in proximity of the transmission source provides for selective control of SAR adjustments. Accordingly, an electronic device can avoid certain communication performance reductions introduced by decreases in transmission power effected to comply with SAR standards by reducing transmission power when human tissue is detected in the proximity but not reducing transmission power when a non-human object (but no human tissue) is detected in the proximity.