5 citations · 10 across the 11 of their papers we have counts for
13 papers
Physical-Layer Aspects of Repeater-Assisted MIMO
Diana P. M. Osorio, Kohei Ueda, Anubhab Chowdhury +4
Network-controlled repeaters (NCRs) are emerg- ing as low-cost, band-selective active scatterers that can re- shape the wireless propagation environment without backhaul or tight p…
Z-Opt: A Near-Optimal Reduced-Complexity Two-Dimensional Grassmannian Constellation
Kotaro Shigenaga, Hiroki Iimori, Yuto Hama +3
Grassmannian constellations achieve the capacity of noncoherent communications over Rayleigh fading channels at high SNR, yet their efficient construction remains challenging. In t…
Sparsification of Precoding Codebooks for PAPR Reduction via Grassmannian Representations
Joe Asano, Yuto Hama, Hiroki Iimori +2
In this letter, we propose a sparsification method for precoding codebooks that reduces the peak-to-average power ratio (PAPR) while preserving the achievable rate. By exploiting t…
Repeater-Assisted MIMO Can Also Boost Frequency Diversity: A Semi-Analytic Study
Hiroki Iimori, Yuto Hama
Massive multiple-input multiple-output (MIMO) has enabled substantial spatial multiplexing and array gains in real-world systems, while distributed MIMO (D-MIMO) improves macro-div…
Low-Complexity and Power-Efficient Precoding Codebook Design on Sparse Grassmannian
Joe Asano, Yuto Hama, Hiroki Iimori +3
We propose a sparse Grassmannian design for precoding codebooks. Due to their sparse structure, our proposed codebooks achieve low peak-to-average power ratio (PAPR), low complexit…
Reciprocity Calibration of Dual-Antenna Repeaters via MMSE Estimation
Shoma Hara, Takumi Takahashi, Hiroki Iimori +2
This paper proposes a novel Bayesian reciprocity calibration method that consistently ensures uplink and downlink channel reciprocity in repeater-assisted multiple-input multiple-o…
Sparse Grassmannian Design for Noncoherent Codes via Schubert Cell Decomposition
Joe Asano, Yuto Hama, Hiroki Iimori +3
In this paper, we propose a method for designing sparse Grassmannian codes for noncoherent multiple-input multiple-output systems. Conventional pairwise error probability formulati…
Joint Pilot Allocation and Sequence Design for MIMO-OFDM Systems With Channel Sparsity
Kabuto Arai, Koji Ishibashi, Hiroki Iimori +3
This paper proposes a joint optimization of pilot subcarrier allocation and non-orthogonal sequence for multiple-input-multiple-output (MIMO)-orthogonal frequency-division multiple…
Maximizing Spectrum Efficiency of Data-Carrying Reference Signals via Bayesian Optimization
Taiki Kato, Hiroki Iimori, Chandan Pradhan +2
Data-carrying reference signals are a type of reference signal (RS) constructed on the Grassmann manifold, which allows for simultaneous data transmission and channel estimation to…
Superimposed Pilot-Based OTFS: Will It Work?
Yuta Kanazawa, Hiroki Iimori, Chandan Pradhan +2
Orthogonal time frequency space (OTFS) modulation is a promising solution to handle doubly-selective fading, but its channel estimation is a nontrivial task in terms of maximizing…
Covert Communications Without Pre-Sharing of Side Information and Channel Estimation Over Quasi-Static Fading Channels
Hiroki Fukada, Hiroki Iimori, Chandan Pradhan +2
We propose a new covert communication scheme that operates without pre-sharing side information and channel estimation, utilizing a Gaussian-distributed Grassmann constellation for…
Achieving Distributed MIMO Performance with Repeater-Assisted Cellular Massive MIMO
Sara Willhammar, Hiroki Iimori, Joao Vieira +3
In what ways could cellular massive MIMO be improved? This technology has already been shown to bring huge performance gains. However, coverage holes and difficulties to transmit m…
Boosting Spectral Efficiency with Data-Carrying Reference Signals on the Grassmann Manifold
Naoki Endo, Hiroki Iimori, Chandan Pradhan +2
In wireless networks, frequent reference signal transmission for accurate channel reconstruction may reduce spectral efficiency. To address this issue, we consider to use a data-ca…