Nobuhiko Miki - RankMe

98 papers B 8C 2Misc 1Journal 34Unranked 53

Year	Rank	Type	Title / Venue / Authors
2025	—	`conf`	Information Set Optimization of Polar Codes Under BP Decoder Based on Union Bound. CCNC Tomoya Okamura, Satoshi Suyama, Satoshi Nagata, Nobuhiko Miki
2025	J	`jnl`	Performance of Iterative Decision Feedback Channel Estimation in Turbo FDE for DFT-Spread OFDM. IEICE Trans. Commun. Chihiro Mori, Mamoru Sawahashi, Nobuhiko Miki, Satoshi Suyama
2024	—	`conf`	Impact of Wi-Fi Network Traffic Load on Video Transmission and Remote Control of Unmanned Guided Vehicle. APWCS Shunsuke Takebe, Junji Terai, Nobuhiko Miki
2024	—	`conf`	Investigation on Information Set Optimization of Neural Network Decoders Suitable for Polar and Convolutional Polar Codes. ICOIN Yuto Nakamura, Satoshi Suyama, Satoshi Nagata, Nobuhiko Miki
2024	C	`conf`	Investigation on Information Set Optimization of Polar Codes Using Concatenated NNDs. APCC Tsukasa Bando, Satoshi Suyama, Satoshi Nagata, Nobuhiko Miki
2024	—	`conf`	Investigation on Variable Coding Rate and Code Length for Relaxed Polar Codes. ICSPCS Nobuhiko Miki, Tatsunori Obara, Satoshi Nagata, Satoshi Suyama
2024	—	`conf`	Local 5G Received Signal Power Measurement in Presence of Building. ICAIIC Ryuya Sembo, Junji Terai, Nobuhiko Miki
2024	—	`conf`	Outdoor RSSI Measurements Using Open-Source Hardware-Based 3D Positioning Device. APWCS Asuka Tada, Junji Terai, Nobuhiko Miki
2023	—	`conf`	Information Set Optimization for Polar Codes Under BP Decoder. APWCS Kohei Ueda, Satoshi Suyama, Satoshi Nagata, Nobuhiko Miki
2023	—	`conf`	Investigation on Offset Optimization for Cell Range Expansion Using Neural Networks in Conjunction with Convex Optimization. APWCS Mitsuto Sato, Yuki Kusaka, Nobuhiko Miki
2023	J	`jnl`	Open-Source Hardware-Based Three-Dimensional Positioning Device for Indoor Measurement and Positioning. IEEE Access Issei Makino, Nobuhiko Miki
2023	J	`jnl`	Small-Scale Demonstration of Remote Control of Patrol and Work Robot with Arms Employing Local 5G System. IEICE Trans. Commun. Issei Makino, Junji Terai, Nobuhiko Miki
2022	J	`jnl`	Throughput and Delay Performance Measurements in Multi-Floor Building Employing Private LTE. IEEE Access Issei Makino, Zhao Wang, Junji Terai, Nobuhiko Miki
2021	—	`conf`	Indoor Local 5G Measurements Employing Automatic Guided Vehicle. WPMC Issei Makino, Junji Terai, Nobuhiko Miki
2021	—	`conf`	Influence of Design-SNR on BER Performance under BP Decoder. APWCS Kohei Ueda, Satoshi Suyama, Takahiro Asai, Nobuhiko Miki
2021	—	`conf`	Performance Evaluation of Neural Network-based Offset Optimization in Cell Range Expansion for Multiple Frequency Bands. APWCS Ryuya Sembo, Nobuhiko Miki
2021	J	`jnl`	Performance of Circular 32QAM/64QAM Schemes Using Frequency Domain Equalizer for DFT-Precoded OFDM. IEICE Trans. Commun. Chihiro Mori, Miyu Nakabayashi, Mamoru Sawahashi, Teruo Kawamura, Nobuhiko Miki
2020	—	`conf`	Combined Usage of Convex Optimization and Neural Network for Resource Allocation. ICSPCS Shoya Tabuchi, Issei Makino, Nobuhiko Miki
2020	J	`jnl`	Joint Optimization for User Association and Inter-Cell Interference Coordination Based on Proportional Fair Criteria in Small Cell Deployments. IEICE Trans. Commun. Nobuhiko Miki, Yusaku Kanehira
2020	—	`conf`	Three-dimensional Scanner for Multipath Fading Measurement. ICTC Issei Makino, Nobuhiko Miki
2019	—	`conf`	Investigation on Distributed Joint Optimization of User Association and ICIC Based on PF Criteria in Small Cell Deployments. ISPACS Takuya Matsumoto, Nobuhiko Miki
2019	—	`conf`	Investigation on Distributed Optimization of User Association and Inter-Cell Interference Coordination Based on Proportional Fair Criteria. CCNC Nobuhiko Miki, Yusaku Kanehira
2019	—	`conf`	Performance of Polar Codes under Successive Cancellation Decoding Employing Approximation Algorithm. ICSPCS Nobuhiko Miki, Satoshi Suyama, Satoshi Nagata
2018	—	`conf`	Investigation on Rate-Compatible Polar Codes Achieving Required Block Error Rates. ICSPCS Taku Sugimoto, Satoshi Suyama, Satoshi Nagata, Nobuhiko Miki
2018	—	`conf`	Joint Optimization of User Association and Resource Allocation Employing Inter-Cell Interference for Multiple Frequency Bands. ISPACS Takaaki Kazumoto, Yusaku Kanehira, Nobuhiko Miki
2018	J	`jnl`	Performance of Interference Rejection Combining Receiver Employing Minimum Mean Square Error Filter for Licensed-Assisted Access. IEICE Trans. Commun. Jumpei Yamamoto, Shunichi Bushisue, Nobuhiko Miki
2018	—	`conf`	User Association and Radio Resource Allocation Combined with Multiple Frequency Bands and ICIC in Small Cell Deployments. ISPACS Nobuhiko Miki
2017	—	`conf`	Investigation on joint optimization for user association and inter-cell interference coordination based on proportional fair criteria. ICSPCS Nobuhiko Miki, Yusaku Kanehira, Hiroaki Tokoshima
2017	J	`jnl`	Performance Comparison of List Viterbi Algorithm of Tail-Biting Convolutional Code for Future Machine Type Communications. IEICE Trans. Commun. Shunichi Bushisue, Satoshi Suyama, Satoshi Nagata, Nobuhiko Miki
2017	—	`conf`	Performance evaluation of inter-cell interference coordination with multiple interference pattern based on proportional fair criteria. WPMC Yusaku Kanehira, Nobuhiko Miki
2017	—	`conf`	Performance evaluation of rate-compatible polar codes using puncturing/shortening. WPMC Taku Sugimoto, Satoshi Suyama, Satoshi Nagata, Nobuhiko Miki
2015	C	`conf`	Investigation on dynamic point selection scheme based on proportional fair criteria. APCC Takeshi Takemoto, Nobuhiko Miki
2015	—	`conf`	Investigation on resource selection scheme based on proportional fair criteria. ICTC Nobuhiko Miki, Takeshi Takemoto
2015	J	`jnl`	Performance of Outer-Loop Control for Adaptive Modulation and Coding Based on Mutual Information in OFDM MIMO SDM. IEICE Trans. Commun. Teppei Ebihara, Yasuhiro Kuge, Hidekazu Taoka, Nobuhiko Miki, Mamoru Sawahashi
2014	J	`jnl`	Investigation on Interference Rejection Combining Receiver for Space-Frequency Block Code Transmit Diversity in LTE-Advanced Downlink. IEEE Trans. Veh. Technol. Yusuke Ohwatari, Nobuhiko Miki, Yuta Sagae, Yukihiko Okumura
2014	J	`jnl`	Performance of Star 16/64QAM Schemes Using Turbo FDE with Iterative Decision-Directed Channel Estimation for DFT-Precoded OFDMA. J. Commun. Chihiro Mori, Mamoru Sawahashi, Teruo Kawamura, Nobuhiko Miki
2013	J	`jnl`	A Simple Scheduling Restriction Scheme for Interference Coordinated Networks. IEICE Trans. Commun. Moo Ryong Jeong, Nobuhiko Miki
2013	J	`jnl`	Investigation of Inter-Cell Interference Coordination Applying Transmission Power Reduction in Heterogeneous Networks for LTE-Advanced Downlink. IEICE Trans. Commun. Akihito Morimoto, Nobuhiko Miki, Yukihiko Okumura
2013	—	`conf`	Investigation on LLR Computation at FDE Output with Receiver Diversity Using Low-Rate Turbo Code for DFT-Precoded OFDMA. VTC Fall Keita Miwa, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2013	J	`jnl`	Investigation on Transmission Power Control Suitable for Heterogeneous Network Employing Cell Range Expansion in LTE-Advanced Uplink. IEICE Trans. Commun. Akihito Morimoto, Nobuhiko Miki, Hiroyuki Ishii, Daisuke Nishikawa, Yukihiko Okumura
2013	—	`conf`	Investigation on interference rejection combining receiver in heterogeneous networks for LTE-Advanced downlink. SPAWC Yusuke Ohwatari, Akihito Morimoto, Nobuhiko Miki, Yukihiko Okumura
2013	J	`jnl`	Performance Evaluation of Interference Rejection Combining Receiver in Heterogeneous Networks for LTE-Advanced Downlink. IEICE Trans. Commun. Yusuke Ohwatari, Akihito Morimoto, Nobuhiko Miki, Yukihiko Okumura
2013	—	`conf`	Performance Evaluation of Reduced Power Inter-cell Interference Coordination for Downlink in LTE-Advanced Heterogeneous Networks. EW Akihito Morimoto, Nobuhiko Miki, Yukihiko Okumura
2013	—	`conf`	Performance of turbo FDE using two-dimensional LMMSE based iterative decision-directed channel estimation for DFT-precoded OFDMA. WCSP Chihiro Mori, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2013	—	`conf`	Performance of turbo frequency domain equalizer using iterative decision-directed channel estimation for DFT-precoded OFDMA. WPMC Chihiro Mori, Yoshikazu Tanaka, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2012	—	`conf`	A Simple Scheduling Restriction Scheme for Interference Coordinated Networks. VTC Fall Moo Ryong Jeong, Nobuhiko Miki
2012	B	`conf`	A comparative study on scheduling restriction schemes for LTE-Advanced networks. PIMRC Moo Ryong Jeong, Nobuhiko Miki
2012	J	`jnl`	Impact on Inter-Cell Interference of Reference Signal for Interference Rejection Combining Receiver in LTE-Advanced Downlink. IEICE Trans. Commun. Yousuke Sano, Yusuke Ohwatari, Nobuhiko Miki, Yuta Sagae, Yukihiko Okumura, Yasutaka Ogawa, Takeo Ohgane, Toshihiko Nishimura
2012	—	`conf`	Investigation on Advanced Receiver Employing Interference Rejection Combining in Asynchronous Network for LTE-Advanced Downlink. VTC Spring Yusuke Ohwatari, Nobuhiko Miki, Tetsushi Abe, Hidekazu Taoka
2012	J	`jnl`	Investigation on Interference Coordination Employing Almost Blank Subframes in Heterogeneous Networks for LTE-Advanced Downlink. IEICE Trans. Commun. Nobuhiko Miki, Yuya Saito, Masashige Shirakabe, Akihito Morimoto, Tetsushi Abe
2012	—	`conf`	Investigation on Transmission Power Control in Heterogeneous Network Employing Cell Range Expansion for LTE-Advanced Uplink. EW Akihito Morimoto, Nobuhiko Miki, Hiroyuki Ishii, Daisuke Nishikawa
2012	B	`conf`	Investigation on advanced receiver employing interference rejection combining for space-frequency block code transmit diversity in LTE-Advanced downlink. PIMRC Yusuke Ohwatari, Nobuhiko Miki, Yuta Sagae, Yukihiko Okumura
2012	—	`conf`	Investigation on link performance modeling of advanced receiver employing interference rejection combining in system level evaluation for LTE-Advanced downlink. ISWCS Yousuke Sano, Yusuke Ohwatari, Nobuhiko Miki, Akihito Morimoto, Yukihiko Okumura
2012	J	`jnl`	Link Performance Modeling of Interference Rejection Combining Receiver in System Level Evaluation for LTE-Advanced Downlink. IEICE Trans. Commun. Yousuke Sano, Yusuke Ohwatari, Nobuhiko Miki, Akihito Morimoto, Yukihiko Okumura
2012	—	`conf`	Link-level performance of star 32/64QAM schemes using frequency domain equalizer for DFT-precoded OFDMA. WPMC Chihiro Mori, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2012	J	`jnl`	Performance Evaluation in Heterogeneous Networks Employing Time-Domain Inter-Cell Interference Coordination and Cell Range Expansion for LTE-Advanced Downlink. IEICE Trans. Commun. Masashige Shirakabe, Akihito Morimoto, Nobuhiko Miki
2012	J	`jnl`	Performance Evaluation of Joint MLD with Channel Coding Information for Control Signals Using Cyclic Shift CDMA and Block Spread CDMA. IEICE Trans. Commun. Teruo Kawamura, Ryota Takahashi, Hideyuki Numata, Nobuhiko Miki, Mamoru Sawahashi
2012	—	`conf`	Performance comparisons of localized and distributed transmissions using iterative decision-directed channel estimation in DFT-precoded OFDMA. WPMC Keita Miwa, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2012	—	`conf`	Performance of Decision-Directed Channel Estimation Using Low-Rate Turbo Codes for DFT-Precoded OFDMA. VTC Spring Keita Miwa, Nobuhiko Miki, Teruo Kawamura, Mamoru Sawahashi
2012	—	`conf`	Performance of Outer-Loop Control for AMC Based on Mutual Information in MIMO-OFDM Downlink. VTC Spring Teppei Ebihara, Hidekazu Taoka, Nobuhiko Miki, Mamoru Sawahashi
2012	Misc	`conf`	Performance of decision-feedback channel estimation for TDM based control signals in OFDMA downlink. ICCS Shunsuke Okaniwa, Nobuhiko Miki, Teruo Kawamura, Mamoru Sawahashi
2012	—	`conf`	Performance of star 16QAM using iterative decision-directed channel estimation for DFT-precoded OFDMA. WCSP Chihiro Mori, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2012	J	`jnl`	Throughput Comparisons of 32/64APSK Schemes Based on Mutual Information Considering Cubic Metric. IEICE Trans. Commun. Reo Kobayashi, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2011	J	`jnl`	Enhanced Inter-cell Interference Coordination for Heterogeneous Networks in LTE-Advanced: A Survey CoRR Lars Lindbom, Robert Love, Sandeep Krishnamurthy, Chunhai Yao, Nobuhiko Miki, Vikram Chandrasekhar
2011	—	`conf`	Femto-to-Macro Control Channel Interference Mitigation via Cell ID Manipulation in LTE. VTC Fall Zubin Bharucha, Gunther Auer, Tetsushi Abe, Nobuhiko Miki
2011	—	`conf`	Hybrid reference signal multiplexing using combination of block spread and cyclic shift CDMA for uplink control signals in DFT-precoded OFDMA. WCSP Yuichiro Hikosaka, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2011	—	`conf`	Inter-Code Interference Canceller for Control Signals Using Cyclic Shift CDMA in LTE Uplink. VTC Spring Yuichiro Hikosaka, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2011	—	`conf`	Investigation on Cell Selection Methods Associated with Inter-cell Interference Coordination in Heterogeneous Networks for LTE-Advanced Downlink. EW Jaturong Sangiamwong, Yuya Saito, Nobuhiko Miki, Tetsushi Abe, Satoshi Nagata, Yukihiko Okumura
2011	J	`jnl`	Investigation on Data Signal Muting to Improve Channel Estimation Accuracy in Downlink Coordinated Multiple-Point Transmission in LTE-Advanced. IEICE Trans. Commun. Yusuke Ohwatari, Nobuhiko Miki, Tetsushi Abe, Satoshi Nagata, Yukihiko Okumura
2011	J	`jnl`	Investigation on Downlink Control Channel Structure Using Cross-Carrier Scheduling for Carrier Aggregation-Based Heterogeneous Network in LTE-Advanced. IEICE Trans. Commun. Nobuhiko Miki, Anxin Li, Kazuaki Takeda, Yuan Yan, Hidetoshi Kayama
2011	—	`conf`	Investigation on Mobility Management for Carrier Aggregation in LTE-Advanced. VTC Fall Kengo Yagyu, Takeshi Nakamori, Hiroyuki Ishii, Mikio Iwamura, Nobuhiko Miki, Takahiro Asai, Junichiro Hagiwara
2011	J	`jnl`	Investigation on Signaling Overhead for Mobility Management with Carrier Aggregation in LTE-Advanced. IEICE Trans. Commun. Kengo Yagyu, Takeshi Nakamori, Hiroyuki Ishii, Mikio Iwamura, Nobuhiko Miki, Takahiro Asai, Junichiro Hagiwara
2011	J	`jnl`	Performance Investigation on Cell Selection Schemes Associated with Downlink Inter-Cell Interference Coordination in Heterogeneous Networks for LTE-Advanced. IEICE Trans. Commun. Yuya Saito, Jaturong Sangiamwong, Nobuhiko Miki, Satoshi Nagata, Tetsushi Abe, Yukihiko Okumura
2011	—	`conf`	Performance evaluation of inter-cell interference coordination and cell range expansion in heterogeneous networks for LTE-Advanced downlink. ISWCS Masashige Shirakabe, Akihito Morimoto, Nobuhiko Miki
2011	—	`conf`	Performance of Advanced Receiver Employing Interference Rejection Combining to Suppress Inter-Cell Interference in LTE-Advanced Downlink. VTC Fall Yusuke Ohwatari, Nobuhiko Miki, Takahiro Asai, Tetsushi Abe, Hidekazu Taoka
2011	J	`jnl`	Performance of Interference Rejection Combining Receiver to Suppress Inter-Cell Interference in LTE-Advanced Downlink. IEICE Trans. Commun. Yusuke Ohwatari, Nobuhiko Miki, Takahiro Asai, Tetsushi Abe, Hidekazu Taoka
2011	—	`conf`	Performance of decision-directed channel estimation using low-rate turbo codes for OFDM. ISPACS Keita Miwa, Nobuhiko Miki, Mamoru Sawahashi
2011	—	`conf`	Search Space Design for Cross-Carrier Scheduling in Carrier Aggregation of LTE-Advanced System. ICC Anxin Li, Kazuaki Takeda, Nobuhiko Miki, Yuan Yan, Hidetoshi Kayama
2011	—	`conf`	Study on resource allocation for VoIP traffic with subframe bundling in LTE uplink. WPMC Masashige Shirakabe, Yoshiaki Ofuji, Akihito Hanaki, Nobuhiko Miki, Takahiro Asai, Junichiro Hagiwara
2011	—	`conf`	Throughput comparisons of star 32/64 QAM schemes based on mutual information considering cubic metric. WCSP Reo Kobayashi, Teruo Kawamura, Nobuhiko Miki, Mamoru Sawahashi
2009	J	`jnl`	Block-Wise Resource Block-Level Distributed Transmission for Shared Data Channel in OFDMA Evolved UTRA Downlink. IEICE Trans. Commun. Satoshi Nagata, Yoshiaki Ofuji, Yoshihisa Kishiyama, Nobuhiko Miki, Kenichi Higuchi, Mamoru Sawahashi
2009	—	`conf`	Effects of Wideband Scheduling and Radio Resource Assignment in OFDMA Radio Access. VTC Fall Kazuaki Takeda, Satoshi Nagata, Yoshihisa Kishiyama, Nobuhiko Miki, Motohiro Tanno
2009	J	`jnl`	Experimental Evaluation of Time Diversity Effect in Hybrid ARQ Considering Space and Path Diversity for Downlink OFDM-Based Broadband Radio Access. IEICE Trans. Commun. Nobuhiko Miki, Hiroyuki Atarashi, Kenichi Higuchi, Mamoru Sawahashi, Masao Nakagawa
2009	J	`jnl`	Layered OFDMA and Its Radio Access Techniques for LTE-Advanced. IEICE Trans. Commun. Motohiro Tanno, Yoshihisa Kishiyama, Hidekazu Taoka, Nobuhiko Miki, Kenichi Higuchi, Mamoru Sawahashi
2009	—	`conf`	MLD Based MIMO-OFDM Demodulation and Decoding LSI with Low Power Consumption for Release 8 LTE. VTC Fall Nobuhiko Miki, Hiroyuki Kawai, Hidekazu Taoka, Kenichi Higuchi, Mamoru Sawahashi, Hiroyuki Matsuno, Hiroyuki Nagasaka
2009	J	`jnl`	Optimum Adaptive Modulation and Channel Coding Scheme for Frequency Domain Channel-Dependent Scheduling in OFDM Based Evolved UTRA Downlink. IEICE Trans. Commun. Nobuhiko Miki, Yoshihisa Kishiyama, Kenichi Higuchi, Mamoru Sawahashi, Masao Nakagawa
2009	—	`conf`	Performance Comparison Between Cyclic Shift and Block Spreading CDMA Using MLD with Channel Coding Information for Uplink Control Signals. VTC Fall Ryota Takahashi, Mamoru Sawahashi, Teruo Kawamura, Nobuhiko Miki
2009	J	`jnl`	Performance Comparison between Turbo Code and Rate-Compatible LDPC Code for Evolved UTRA Downlink OFDM Radio Access. IEICE Trans. Commun. Naoto Okubo, Nobuhiko Miki, Yoshihisa Kishiyama, Kenichi Higuchi, Mamoru Sawahashi
2008	—	`conf`	Layered OFDMA Radio Access for IMT-Advanced. VTC Fall Motohiro Tanno, Yoshihisa Kishiyama, Hidekazu Taoka, Nobuhiko Miki, Kenichi Higuchi, Mamoru Sawahashi
2007	B	`conf`	Investigation on Optimum Coding and Multiplexing Schemes for L1/L2 Control Signals in OFDM based Evolved UTRA Downlink. PIMRC Nobuhiko Miki, Yoshihisa Kishiyama, Kenichi Higuchi, Mamoru Sawahashi
2007	B	`conf`	Optimum Adaptive Modulation and Channel Coding Scheme for Frequency Domain Channel-Dependent Scheduling in OFDM Based Evolved UTRA Downlink. WCNC Nobuhiko Miki, Yoshihisa Kishiyama, Kenichi Higuchi, Mamoru Sawahashi
2005	J	`jnl`	Comparison of Throughput Employing Hybrid ARQ Packet Combining in Forward Link OFCDM Broadband Packet Wireless Access. IEICE Trans. Commun. Nobuhiko Miki, Hiroyuki Atarashi, Sadayuki Abeta, Mamoru Sawahashi
2004	B	`conf`	Effect of time diversity in hybrid ARQ considering space and path diversity for VSF-OFCDM downlink broadband wireless access. PIMRC Nobuhiko Miki, Hiroyuki Atarashi, Mamoru Sawahashi
2004	B	`conf`	Field experiments on low-rate turbo coding and soft-decision decoding for broadband packet DS-CDMA wireless access in reverse link. PIMRC Shingo Suwa, Nobuhiko Miki, Motohiro Tanno, Kenichi Higuchi, Mamoru Sawahashi
2003	B	`conf`	Experimental evaluation on effect of hybrid ARQ with packet combining in forward link for VSF-OFCDM broadband wireless access. PIMRC Nobuhiko Miki, Hiroyuki Atarashi, Kenichi Higuchi, Sadayuki Abeta, Mamoru Sawahashi
2002	J	`jnl`	Comparison of Hybrid ARQ Packet Combining Algorithm in High Speed Downlink Packet Access in a Multipath Fading Channel. IEICE Trans. Fundam. Electron. Commun. Comput. Sci. Nobuhiko Miki, Hiroyuki Atarashi, Sadayuki Abeta, Mamoru Sawahashi
2002	B	`conf`	Evaluation of throughput employing hybrid ARQ packet combining in forward link OFCDM broadband wireless access. PIMRC Nobuhiko Miki, Sadayuki Abeta, Mamoru Sawahashi
2001	—	`conf`	Multipath interference canceller using soft-decision replica combined with hybrid ARQ in W-CDMA forward link. VTC Fall Nobuhiko Miki, Sadayuki Abeta, Hiroyuki Atarashi, Mamoru Sawahashi