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Ikeda K.,KDDI R and D Laboratories Inc. | Bernstein M.S.,Stanford University
Conference on Human Factors in Computing Systems - Proceedings | Year: 2016

Paid crowdsourcing marketplaces have gained popularity by using piecework, or payment for each microtask, to incentivize workers. This norm has remained relatively unchallenged. In this paper, we ask: is the pay-per-task method the right one? We draw on behavioral economic research to examine whether payment in bulk after every ten tasks, saving money via coupons instead of earning money, or material goods rather than money will increase the number of completed tasks. We perform a twenty-day, between-subjects field experiment (N=300) on a mobile crowdsourcing application and measure how often workers responded to a task notification to fill out a short survey under each incentive condition. Task completion rates increased when paying in bulk after ten tasks: doing so increased the odds of a response by 1.4x, translating into 8% more tasks through that single intervention. Payment with coupons instead of money produced a small negative effect on task completion rates. Material goods were the most robust to decreasing participation over time.

Liu L.,KDDI R and D Laboratories Inc. | Tsuritani T.,KDDI R and D Laboratories Inc. | Morita I.,KDDI R and D Laboratories Inc. | Guo H.,Beijing University of Posts and Telecommunications | Wu J.,Beijing University of Posts and Telecommunications
Optics Express | Year: 2011

OpenFlow, as an open-source protocol for network virtualization, is also widely regarded as a promising control plane technique for heterogeneous networks. But the utilization of the OpenFlow protocol to control a wavelength switched optical network has not been investigated. In this paper, for the first time, we experimentally present a proof-of-concept demonstration of OpenFlow-based wavelength path control for lightpath provisioning in transparent optical networks. We propose two different approaches (sequential and delayed approaches) for lightpath setup and two different approaches (active and passive approaches) for lightpath release by using the OpenFlow protocol. The overall feasibility of these approaches is experimentally validated and the network performances are quantitatively evaluated. More importantly, all the proposed methodologies are demonstrated and evaluated on a real transparent optical network testbed with both OpenFlow-based control plane and data plane, which allows their feasibility and effectiveness to be verified, and valuable insights of the proposed solutions to be obtained for deploying into real OpenFlow controlled optical networks. © 2011 Optical Society of America.

Peng W.-R.,KDDI R and D Laboratories Inc. | Morita I.,KDDI R and D Laboratories Inc. | Takahashi H.,KDDI R and D Laboratories Inc. | Tsuritani T.,KDDI R and D Laboratories Inc.
Journal of Lightwave Technology | Year: 2012

In this paper, we propose and experimentally demonstrate the direct-detection optical orthogonal-frequency-division-multiplexing superchannel (DDO-OFDM-S) and optical multiband receiving method (OMBR) to support >100-Gb/s data rate and a longer distance for direct-detection systems. For the new OMBR, we discuss the optimum carrier-to-sideband power ratio (CSPR) both in the cases of back-to-back and after transmission, and derive the analytical form for CSPR which is verified with numerical results. An overhead-efficient training method for in-phase/quadrature-phase imbalance estimation is also introduced in order to obtain a better performance while maintaining the high throughput of the system. With experimental setups, we evaluate the two systems with 1) 16-QAM, 214-Gb/s (190 Gb/s without overhead) and 2) 4-QAM, 117-Gb/s (100 Gb/s without overhead) systems. The new proposals enable the record data rate per wavelength (214 Gb/s) and record distance of 720-km standard single-mode fiber (SSMF) for the >100-Gb/s DDO-OFDM systems, and achieve the record optical signal-to-noise ratio sensitivity of 21.2 dB and record distance of 1200-km SSMF ∼1 dB penalty) for the 100-Gb/s class DDO-OFDM systems. © 2012 IEEE.

Minamikawa A.,KDDI R and D Laboratories Inc. | Yokoyama H.,KDDI R and D Laboratories Inc.
Proceedings of the ACM Conference on Computer Supported Cooperative Work, CSCW | Year: 2011

In this paper, we investigate personality estimation from Japanese weblog text. Among various personality types, we focus on Egogram, which has been used in Transactional Analysis and is strongly related to the communicative behavior of individuals. Estimation is performed using the Multinomial Naïve Bayes classifier with some feature words that are selected based on the information gain. The validity of this approach was evaluated with real weblog text of 551 subjects. The results show that our approach achieved 12-25% improvement from baseline. The feature words selected for the estimation are strongly correlated with the characteristics of Egogram. Copyright 2011 ACM.

Peng W.-R.,KDDI R and D Laboratories Inc. | Tsuritani T.,KDDI R and D Laboratories Inc. | Morita I.,KDDI R and D Laboratories Inc.
Journal of Lightwave Technology | Year: 2013

In this paper we demonstrate high-baud generation and transmission of PDM-64QAM signals. The 64QAM signal is generated using one single in-phase/quadrature (I/Q) modulator driven with eight-level signals synthesized by all binary electrical inputs. With hard-decision forward error correction (HD-FEC), we first demonstrate 11.2-GBd and 22.4-GBd PDM-64QAM transmissions over 320-km standard single mode fiber (SSMF). Then we specifically introduce a long memory filter (LMF) and prove its effectiveness in reflection compensation both theoretically and experimentally. With the aid of soft-decision FEC (SD-FEC), optical pre-shaping, and LMF, we transmit a 41.4-GBd PDM-64QAM signal over 1200-km SSMF. Finally, using per-channel 41.6-GBd PDM-64QAM with SD-FEC, we successfully demonstrate 50-GHz-spaced, 8 × 499-Gb/s transmission over 720-km SSMF. This is the first demonstration of400-Gb/s/ch WDM transmission on the 50-GHz ITU grid that uses a per-channel single-carrier scheme. © 1983-2012 IEEE.

Martinez R.,Catalonia Technology Center of Telecomunications | Casellas R.,Catalonia Technology Center of Telecomunications | Munoz R.,Catalonia Technology Center of Telecomunications | Tsuritani T.,KDDI R and D Laboratories Inc.
Journal of Lightwave Technology | Year: 2010

In the evolution from opaque networks, using 3R regenerators and OEO conversions for every wavelength channel, towards transparent networks, relying on end-to-end all-optical connections, translucent networks is considered as an intermediate step. A translucent network is a cost-efficient infrastructure between opaque and transparent networks, that aims at attaining an adequate trade-off between network construction cost (i.e., due to the high cost of 3R regenerators) and the service provisioning performance (i.e., end-to-end optical signal quality). This article addresses the dynamic provisioning of connections within a GMPLS-enabled translucent wavelength switched optical network with sparse 3R regenerators. To this end, translucent-oriented GMPLS protocol extensions are proposed to, on the one hand, disseminate required per node regenerator availability and OSNR-related link and node attributes and, on the other hand, allocate regenerator resources when setting up connections. An on-line OSNR-based impairment-aware RWA algorithm is devised to compute routes aiming at satisfying two constraints: the wavelength continuity constraint and the end-to-end optical signal quality. If either constraint cannot be satisfied, available regenerators along the route are used. To the best of our knowledge, the novelty and progress of this work is that, for the first time, both the proposed translucent GMPLS protocol enhancements and the performance of the RWA algorithm are combined within an experimental control plane network scenario (CTTC's ADRENALINE testbed). This allows validating and evaluating the feasibility of the described translucent GMPLS routing strategy when being potentially deployed into real WSON networks. Several configurations with numbers of 3R regenerators and wavelength channels per link, are experimentally evaluated and compared mainly in terms of the connection blocking probability. Although concrete details about the measured average setup delay are also discussed. © 2010 IEEE.

Konishi S.,KDDI R and D Laboratories Inc.
IEICE Transactions on Communications | Year: 2013

We have seen a rapid increase in mobile data traffic in cellular networks, especially in densely populated areas called "hotspots." In order to deal with this trend, heterogeneous networks (HetNet) are attracting much attention as a method of effectively accommodating such traffic increases using the Long Term Evolution (LTE)-Advanced system in the 3rd Generation Partnership Project (3GPP). This paper first presents an overview of HetNet, where various wireless nodes can be deployed over the coverage area formed by macro base stations (BSs). Next, various evaluation results are provided for HetNet, where pico BSs ("Pico-BSs") are deployed over the coverage area of macro BSs ("Macro-BSs"). Then, this paper presents a comprehensive analysis, not only of the effect of overlaying Pico-BSs but also a detailed analyses of the techniques called "cell range expansion (CRE)" and "enhanced inter-cell interference coordination (eICIC)" for facilitating the offloading of user terminals (UEs) from Macro-BSs to Pico-BSs and mitigating interference, respectively, for both downlink and uplink. Noteworthy outcomes found through the comprehensive study are that CRE provides throughput improvements for uplinks, especially for UE connected to Pico-BSs. In addition, this paper demonstrates that CRE contributes to improving downlink throughput especially for low traffic loads. The outcome regarding eICIC is that eICIC provides improvements in total throughput, in spite of the fact that eICIC causes unfairness between UE connected to the Pico-BSs and those with Macro-BSs. Copyright © 2013 The Institute of Electronics.

Suzuki M.,KDDI R and D Laboratories Inc.
2013 IEEE Photonics Society Summer Topical Meeting Series, PSSTMS 2013 | Year: 2013

Space-division multiplexing (SDM) via multicore/multimode fibers is currently being actively explored to overcome the capacity limit of single-mode fiber. In this paper, recent progress in R&D on SDM in Japan will be introduced. © 2013 IEEE.

Choi H.Y.,KDDI R and D Laboratories Inc. | Tsuritani T.,KDDI R and D Laboratories Inc. | Morita I.,KDDI R and D Laboratories Inc.
Optics Express | Year: 2012

We propose a new optical transmitter which is capable of changing flexibly the modulation format of the optical signal. By using this transmitterwe can handle and assign various modulation formats: binary phase shift keying (BPSK)quadrature phase shift keying (QPSK)8-ary quadrature amplitude modulation (8QAM)and 16QAM. The proposed transmitter is based on a combination of a dual-drive Mach-Zehnder modulator (DD-MZM) and a dual-parallel MZM (DP-MZM) with electrical binary drive signals. DD-MZM is a key element to produce the 8QAM and 16QAM formats where each arm of DD-MZM is driven by independent binary data. This is because we can modulate the amplitude and phase of the optical signal by using a frequency chirp of the modulator when we adjust properly the amplitudes of the electrical drive signals. In additionwe show an algorithm by which the proposed transmitter can intelligently select the modulation format in accordance with the signal quality. © 2012 Optical Society of America.

Nanba S.,KDDI R and D Laboratories Inc. | Agata A.,KDDI R and D Laboratories Inc.
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2013

In the Centralized-RAN (C-RAN), some baseband units (BBUs) are centralized in the same location, which is typically less than 20 km away from remote radio heads (RRHs) locally distributed. Each RRH is connected to BBUs via front-haul link by optical fibers which convey the digital IQ data by CPRI protocol. This paper proposes a new IQ data compression scheme with 1/2 compression ratio, which can be easily implemented by using both IQ bit width reduction and a common lossless audio compression scheme. Through performance evaluation, it is verified that the proposed method meets the requirements from an implementation point of view. By applying the proposed scheme to the front-haul link, the installation cost of optical fibers can be reduced by half. © 2013 IEEE.

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