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京都大学0048新制・課程博士博士(情報学)甲第14001号情博第316号新制||情||60(附属図書館)UT51-2008-C917京都大学大学院情報学研究科通信情報システム専攻(主査)教授 吉田 進, 教授 高橋 達郎, 教授 守倉 正博学位規則第4条第1項該当Doctor of InformaticsKyoto UniversityDA

Optimum practical design of distributed and asynchronous power control for wireless networks with shared bands

Multi-dimensional Mobile Information NetworksThe present paper proposes two novel and practical schemes for distributed and asynchronous power control in wireless ad hoc networks, in which users dynamically share several frequency bands as in "cognitive radio" networks. These schemes iteratively adjust transmit powers of individual network transmitters with respect to mutually caused interference in the shared bands. Their most attractive feature is that they find network-wide acceptable trade-offs to diverse signal-to-noise and interference (SINR) requirements and efficiently use techniques of stochastic approximation and time-averaging to guarantee a robust performance in random channels. Advantageously, both proposed algorithms do not assume any particular modulation, coding, QoS measure definition or network architecture, which assures their high applicability in the industry and research. Moreover, the broad definition and non-linear nature of these schemes mathematically generalize and thus encompass as a special case many widely deployed power control schemes such as e.g. those for achieving fixed SINR targets or using game-theoretic utility maximization. Simulations are provided to illustrate our approach and its better performance compared to standard algorithms

Unitary checkerboard precoded OFDM for low-PAPR optical wireless communications

Future 6G wireless networks will once again have to raise the performance in most technology domains by a factor of 10-100. Depending on the application, future requirements include peak data rates of 1 Tb/s per user, 0.1 ms latency, less than one out of a million outage, centimeter accurate positioning, near zero energy consumption at the device, and operation in different environments including factories, vehicles, and more. Optical wireless communications (OWCs) have the potential to provide ultrahigh data rates in a cost effective way, due to the vast and freely available light spectrum, and the availability of devices for transmitters and receivers. 5G New Radio architecture permits the integration of stand-alone OWC nodes on network layers. Current 6G research investigates advanced physical layer designs including OWC-compatible waveforms. In this context, in this paper, a new precoded orthogonal frequency division multiplexing (OFDM) waveform is proposed that is tailored to OWCs' specific needs. Its prime advantage compared to OFDM is the ultralow peak-to-average power ratio, while preserving other benefits, such as high spectral efficiency, flexible subcarrier nulling, and low computational complexity

Low-latency communications in LTE using spatial diversity and encoding redundancy

Control of data delivery latency in wireless mobile networks is an open problem due to the inherently unreliable and stochastic nature of wireless channels. This paper explores how the current best-effort throughput-oriented wireless services could be evolved into latency-sensitive enablers of new mobile applications such as remote 3D graphical rendering for interactive virtual/augmented-reality overlay. Assuming that the signal propagation delay and achievable throughput meet the basic latency requirements of the user application, we examine the idea of trading excess/federated bandwidth for the elimination of non-negligible data re-ordering delays, caused by temporal transmission failures and buffer overflows. The general system design is based on (i) spatially diverse delivery of data over multiple paths with uncorrelated outage likelihoods, and (ii)forward packet protection based on encoding redundancy that enables proactive recovery of lost or intolerably delayed data without end-to-end re-transmissions. Our analysis is based on traces of real-life traffic in live carrier-grade LTE networks