The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Akira Hirano - One of the best experts on this subject based on the ideXlab platform.
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a novel elastic optical path network that utilizes bitrate specific anchored Frequency Slot arrangement
Optics Express, 2014Co-Authors: Zhishu Shen, Kenichi Sato, Hiroshi Hasegawa, Takafumi Tanaka, Akira HiranoAbstract:We propose a novel elastic optical path network where each specific bitrate signal uses its own dedicated fixed grid and one edge of its Frequency grid is anchored at a specific Frequency. Numerical evaluations using various bitrate signal patterns and network topologies show that the network proposal can almost match the performance of conventional flexible grid networks, while greatly mitigating the hardware requirements: it allows the use of the tunable filters for the fixed grid systems.
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Virtualization in optical networks from network level to hardware level [invited]
Journal of Optical Communications and Networking, 2013Co-Authors: Masahiko Jinno, Hidehiko Takara, Kazushige Yonenaga, Akira HiranoAbstract:Elastic optical networking is attracting much attention as a promising solution to achieve spectrum-efficient transport of higher data rates at 100 Gbits/s and beyond. If we draw an analogy to virtualization in cloud computing, it can be seen as network level resource virtualization of optical networks where spectrum resources in optical links are segmented as shareable resources and adaptively aggregated to create a wide variety of optical channels (OChs). In this paper, we discuss the benefits of introducing virtualization into the optical domain from the viewpoints of the network level and the hardware level. In elastic optical networks, a Frequency Slot through which an OCh is transported and the OCh itself are explicitly decoupled. While the adaptability in the Frequency Slot is brought about by bandwidth variable wavelength-selective switches, the adaptability in an OCh is yielded by digital coherent technology that is employed in transponders and regenerators. It is emphasized that in order to achieve transponders and regenerators that accommodate heterogeneous traffic demands in an economical manner, simply being adaptive is not enough, and being shareable is essential. We refer to this concept as hardware level virtualization. As examples, we describe a multiflow transponder and an elastic regenerator with results that show proof of concept. Based on the hardware virtualization concept, we propose an elastic optical transport system (EOTS) architecture that enables cost- and energy-efficient IP traffic offloading to the optical domain and improves programmability and automation of optical networks.
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dynamic routing and Frequency Slot assignment for elastic optical path networks that adopt distance adaptive modulation
Optical Fiber Communication Conference, 2011Co-Authors: Tatsumi Takagi, Akira Hirano, Hiroshi Hasegawa, Kenichi Sato, Yoshiaki Sone, Bartlomiej Kozicki, Masahiko JinnoAbstract:We propose a dynamic routing and Frequency Slot assignment algorithm for SLICE networks that employ distance adaptive modulation. We verify that the spectrum utilization penalty that stems from non-uniform bandwidth allocation is marginal.
Giuseppe Caire - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of massive mimo for cell boundary users
IEEE Transactions on Wireless Communications, 2015Co-Authors: Chanbyoung Chae, Giuseppe CaireAbstract:In this paper, we consider massive multiple-input–multiple-output systems for both downlink and uplink scenarios, where three radio units connected via one digital unit support multiple user equipments at the cell-boundary through the same radio resource, i.e., the same time–Frequency Slot. For downlink transmitter options, the study considers zero forcing (ZF) and maximum ratio transmission (MRT), whereas for uplink receiver options, it considers ZF and maximum ratio combining (MRC). For the sum rate of each of these, we derive simple closed-form formulas. In the simple but practically relevant case where uniform power is allocated to all downlink data streams, we observe that, for the downlink, vector normalization is better for ZF whereas matrix normalization is better for MRT. For a given antenna and user configuration, we also analytically derive the signal-to-noise-ratio level below which MRC should be used instead of ZF. Numerical simulations confirm our analytical results.
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airsync enabling distributed multiuser mimo with full spatial multiplexing
IEEE ACM Transactions on Networking, 2013Co-Authors: Horia Vlad Balan, Ryan Rogalin, Antonios Michaloliakos, Konstantinos Psounis, Giuseppe CaireAbstract:The enormous success of advanced wireless devices is pushing the demand for higher wireless data rates. Denser spectrum reuse through the deployment of more access points (APs) per square mile has the potential to successfullymeet such demand. In principle, distributed multiuser multiple-input-multiple-output (MU-MIMO) provides the best approach to infrastructure density increase since several access points are connected to a central server and operate as a large distributed multiantenna access point. This ensures that all transmitted signal power serves the purpose of data transmission, rather than creating interference. In practice, however, a number of implementation difficulties must be addressed, the most significant of which is aligning the phases of all jointly coordinated APs. In this paper, we propose AirSync, a novel scheme that provides timing and phase synchronization accurate enough to enable distributed MU-MIMO. AirSync detects the Slot boundary such that all APs are time-synchronous within a cyclic prefix (CP) of the orthogonal Frequency-division multiplexing (OFDM) modulation and predicts the instantaneous carrier phase correction along the transmit Slot such that all transmitters maintain their coherence, which is necessary for multiuser beamforming. We have implemented AirSync as a digital circuit in the field programmable gate array (FPGA) of the WARP radio platform. Our experimental testbed, comprising four APs and four clients, shows that AirSync is able to achieve timing synchronization within the OFDM CP and carrier phase coherence within a few degrees. For the purpose of demonstration, we have implemented two MU-MIMO precoding schemes, Zero-Forcing Beamforming (ZFBF) and Tomlinson-Harashima Precoding (THP). In both cases, our system approaches the theoretical optimal multiplexing gains. We also discuss aspects related to the MAC and multiuser scheduling design, in relation to the distributed MU-MIMO architecture. To the best of our knowledge, AirSync offers the first realization of the full distributed MU-MIMO multiplexing gain, namely the ability to increase the number of active wireless clients per time-Frequency Slot linearly with the number of jointly coordinated APs, without reducing the per client rate.
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performance analysis of massive mimo for cell boundary users
arXiv: Information Theory, 2013Co-Authors: Yeongeun Lim, Chanbyoung Chae, Giuseppe CaireAbstract:In this paper, we consider massive multiple-input multiple-output (MIMO) systems for both downlink and uplink scenarios, where three radio units (RUs) connected via one digital unit (DU) support multiple user equipments (UEs) at the cell-boundary through the same radio resource, i.e., the same time-Frequency Slot. For downlink transmitter options, the study considers zero-forcing (ZF) and maximum ratio transmission (MRT), while for uplink receiver options it considers ZF and maximum ratio combining (MRC). For the sum rate of each of these, we derive simple closed-form formulas. In the simple but practically relevant case where uniform power is allocated to all downlink data streams, we observe that, for the downlink, vector normalization is better for ZF while matrix normalization is better for MRT. For a given antenna and user configuration, we also derive analytically the signal-to-noise-ratio (SNR) level below which MRC should be used instead of ZF. Numerical simulations confirm our analytical results.
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on the coexistence of macrocell spatial multiplexing and cognitive femtocells
arXiv: Information Theory, 2012Co-Authors: Ansuman Adhikary, Giuseppe CaireAbstract:We study a two-tier macrocell/femtocell system where the macrocell base station is equipped with multiple antennas and makes use of multiuser MIMO (spatial multiplexing), and the femtocells are "cognitive". In particular, we assume that the femtocells are aware of the locations of scheduled macrocell users on every time-Frequency Slot, so that they can make decisions on their transmission opportunities accordingly. Femtocell base stations are also equipped with multiple antennas. We propose a scheme where the macrocell downlink (macro- DL) is aligned with the femtocells uplink (femto-UL) and, Vice Versa, the macrocell uplink (macro-UL) is aligned with the femtocells downlink femto-DL). Using a simple "interference temperature" power control in the macro-DL/femto-UL direction, and exploiting uplink/downlink duality and the Yates, Foschini and Miljanic distributed power control algorithm in the macro- UL/femto-DL direction, we can achieve an extremely attractive macro/femto throughput tradeoff region in both directions. We investigate the impact of multiuser MIMO spatial multiplexing in the macrocell under the proposed scheme, and find that large gains are achievable by letting the macrocell schedule groups of co-located users, such that the number of femtocells affected by the interference temperature power constraint is small.
Masahiko Jinno - One of the best experts on this subject based on the ideXlab platform.
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Virtualization in optical networks from network level to hardware level [invited]
Journal of Optical Communications and Networking, 2013Co-Authors: Masahiko Jinno, Hidehiko Takara, Kazushige Yonenaga, Akira HiranoAbstract:Elastic optical networking is attracting much attention as a promising solution to achieve spectrum-efficient transport of higher data rates at 100 Gbits/s and beyond. If we draw an analogy to virtualization in cloud computing, it can be seen as network level resource virtualization of optical networks where spectrum resources in optical links are segmented as shareable resources and adaptively aggregated to create a wide variety of optical channels (OChs). In this paper, we discuss the benefits of introducing virtualization into the optical domain from the viewpoints of the network level and the hardware level. In elastic optical networks, a Frequency Slot through which an OCh is transported and the OCh itself are explicitly decoupled. While the adaptability in the Frequency Slot is brought about by bandwidth variable wavelength-selective switches, the adaptability in an OCh is yielded by digital coherent technology that is employed in transponders and regenerators. It is emphasized that in order to achieve transponders and regenerators that accommodate heterogeneous traffic demands in an economical manner, simply being adaptive is not enough, and being shareable is essential. We refer to this concept as hardware level virtualization. As examples, we describe a multiflow transponder and an elastic regenerator with results that show proof of concept. Based on the hardware virtualization concept, we propose an elastic optical transport system (EOTS) architecture that enables cost- and energy-efficient IP traffic offloading to the optical domain and improves programmability and automation of optical networks.
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dynamic routing and Frequency Slot assignment for elastic optical path networks that adopt distance adaptive modulation
Optical Fiber Communication Conference, 2011Co-Authors: Tatsumi Takagi, Akira Hirano, Hiroshi Hasegawa, Kenichi Sato, Yoshiaki Sone, Bartlomiej Kozicki, Masahiko JinnoAbstract:We propose a dynamic routing and Frequency Slot assignment algorithm for SLICE networks that employ distance adaptive modulation. We verify that the spectrum utilization penalty that stems from non-uniform bandwidth allocation is marginal.
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algorithms for maximizing spectrum efficiency in elastic optical path networks that adopt distance adaptive modulation
European Conference on Optical Communication, 2010Co-Authors: Tatsumi Takagi, Hiroshi Hasegawa, Kenichi Sato, Yoshiaki Sone, Bartlomiej Kozicki, Takafumi Tanaka, Masahiko JinnoAbstract:We propose optical path routing and Frequency Slot assignment algorithms that suit elastic optical paths and the distance adaptive modulation scheme. The algorithms are proven to yield high spectrum efficiency for the distant-adaptive Frequency allocation scheme.
Hiroshi Hasegawa - One of the best experts on this subject based on the ideXlab platform.
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network expansion strategy for elastic optical networks that considers channel capacity upgrades
Proceedings of SPIE, 2017Co-Authors: Takuma Yasuda, Hiroshi Hasegawa, Yojiro Mori, Kenichi SatoAbstract:We propose introducing aligned Frequency assignment to each bandwidth channel, i.e., the semi-flexible grid, with the goal of minimizing Frequency Slot fragmentation under dynamic flexible-grid network expansion considering the expected need for channel capacity upgrades. In semi-flexible grid networks, for each set of channels having the same Frequency bandwidth, a regular grid is defined where its spacing is the same as the required bandwidth and channels are aligned to their corresponding grids. A network expansion algorithm is developed that maximizes the efficiency of semiflexible grid assignment to achieve efficient channel bandwidth upgrading. Numerical experiments prove that the number of fibers necessary and the degree of fragmentation in the Frequency domain are reduced by 15% and 80%, respectively, compared to conventional flexible grid networks accommodating the same traffic.
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a novel elastic optical path network that utilizes bitrate specific anchored Frequency Slot arrangement
Optics Express, 2014Co-Authors: Zhishu Shen, Kenichi Sato, Hiroshi Hasegawa, Takafumi Tanaka, Akira HiranoAbstract:We propose a novel elastic optical path network where each specific bitrate signal uses its own dedicated fixed grid and one edge of its Frequency grid is anchored at a specific Frequency. Numerical evaluations using various bitrate signal patterns and network topologies show that the network proposal can almost match the performance of conventional flexible grid networks, while greatly mitigating the hardware requirements: it allows the use of the tunable filters for the fixed grid systems.
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a novel semi flexible grid optical path network that utilizes aligned Frequency Slot arrangement
European Conference on Optical Communication, 2013Co-Authors: A Hirano, Hiroshi Hasegawa, Kenichi Sato, T Tanaka, Zhishu ShenAbstract:We propose a novel elastic optical path network where each specific bitrate signal uses its own dedicated fixed grid and a Slot-width-edge anchor Frequency. Numerical evaluations verify that the proposed networks can almost match the performance of conventional flexible grid networks, while allowing tunable filters to be used in a fixed grid system.
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dynamic routing and Frequency Slot assignment for elastic optical path networks that adopt distance adaptive modulation
Optical Fiber Communication Conference, 2011Co-Authors: Tatsumi Takagi, Akira Hirano, Hiroshi Hasegawa, Kenichi Sato, Yoshiaki Sone, Bartlomiej Kozicki, Masahiko JinnoAbstract:We propose a dynamic routing and Frequency Slot assignment algorithm for SLICE networks that employ distance adaptive modulation. We verify that the spectrum utilization penalty that stems from non-uniform bandwidth allocation is marginal.
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algorithms for maximizing spectrum efficiency in elastic optical path networks that adopt distance adaptive modulation
European Conference on Optical Communication, 2010Co-Authors: Tatsumi Takagi, Hiroshi Hasegawa, Kenichi Sato, Yoshiaki Sone, Bartlomiej Kozicki, Takafumi Tanaka, Masahiko JinnoAbstract:We propose optical path routing and Frequency Slot assignment algorithms that suit elastic optical paths and the distance adaptive modulation scheme. The algorithms are proven to yield high spectrum efficiency for the distant-adaptive Frequency allocation scheme.
Kenichi Sato - One of the best experts on this subject based on the ideXlab platform.
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network expansion strategy for elastic optical networks that considers channel capacity upgrades
Proceedings of SPIE, 2017Co-Authors: Takuma Yasuda, Hiroshi Hasegawa, Yojiro Mori, Kenichi SatoAbstract:We propose introducing aligned Frequency assignment to each bandwidth channel, i.e., the semi-flexible grid, with the goal of minimizing Frequency Slot fragmentation under dynamic flexible-grid network expansion considering the expected need for channel capacity upgrades. In semi-flexible grid networks, for each set of channels having the same Frequency bandwidth, a regular grid is defined where its spacing is the same as the required bandwidth and channels are aligned to their corresponding grids. A network expansion algorithm is developed that maximizes the efficiency of semiflexible grid assignment to achieve efficient channel bandwidth upgrading. Numerical experiments prove that the number of fibers necessary and the degree of fragmentation in the Frequency domain are reduced by 15% and 80%, respectively, compared to conventional flexible grid networks accommodating the same traffic.
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a novel elastic optical path network that utilizes bitrate specific anchored Frequency Slot arrangement
Optics Express, 2014Co-Authors: Zhishu Shen, Kenichi Sato, Hiroshi Hasegawa, Takafumi Tanaka, Akira HiranoAbstract:We propose a novel elastic optical path network where each specific bitrate signal uses its own dedicated fixed grid and one edge of its Frequency grid is anchored at a specific Frequency. Numerical evaluations using various bitrate signal patterns and network topologies show that the network proposal can almost match the performance of conventional flexible grid networks, while greatly mitigating the hardware requirements: it allows the use of the tunable filters for the fixed grid systems.
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a novel semi flexible grid optical path network that utilizes aligned Frequency Slot arrangement
European Conference on Optical Communication, 2013Co-Authors: A Hirano, Hiroshi Hasegawa, Kenichi Sato, T Tanaka, Zhishu ShenAbstract:We propose a novel elastic optical path network where each specific bitrate signal uses its own dedicated fixed grid and a Slot-width-edge anchor Frequency. Numerical evaluations verify that the proposed networks can almost match the performance of conventional flexible grid networks, while allowing tunable filters to be used in a fixed grid system.
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dynamic routing and Frequency Slot assignment for elastic optical path networks that adopt distance adaptive modulation
Optical Fiber Communication Conference, 2011Co-Authors: Tatsumi Takagi, Akira Hirano, Hiroshi Hasegawa, Kenichi Sato, Yoshiaki Sone, Bartlomiej Kozicki, Masahiko JinnoAbstract:We propose a dynamic routing and Frequency Slot assignment algorithm for SLICE networks that employ distance adaptive modulation. We verify that the spectrum utilization penalty that stems from non-uniform bandwidth allocation is marginal.
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algorithms for maximizing spectrum efficiency in elastic optical path networks that adopt distance adaptive modulation
European Conference on Optical Communication, 2010Co-Authors: Tatsumi Takagi, Hiroshi Hasegawa, Kenichi Sato, Yoshiaki Sone, Bartlomiej Kozicki, Takafumi Tanaka, Masahiko JinnoAbstract:We propose optical path routing and Frequency Slot assignment algorithms that suit elastic optical paths and the distance adaptive modulation scheme. The algorithms are proven to yield high spectrum efficiency for the distant-adaptive Frequency allocation scheme.
