11 papers
Z-Opt: A Near-Optimal Reduced-Complexity Two-Dimensional Grassmannian Constellation
Kotaro Shigenaga, Hiroki Iimori, Yuto Hama +3
Grassmannian constellations are known to achieve the capacity of noncoherent communications over Rayleigh fading channels in the high-SNR regime, yet their efficient construction r…
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…
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…
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…