Showing papers by "NTT DoCoMo published in 2018"

Toward the Standardization of Non-Orthogonal Multiple Access for Next Generation Wireless Networks

Abstract: Non-orthogonal multiple access (NOMA) as an efficient method of radio resource sharing has its roots in network information theory. For generations of wireless communication systems design, orthogonal multiple access schemes in the time, frequency, or code domain have been the main choices due to the limited processing capability in the transceiver hardware, as well as the modest traffic demands in both latency and connectivity. However, for the next generation radio systems, given its vision to connect everything and the much evolved hardware capability, NOMA has been identified as a promising technology to help achieve all the targets in system capacity, user connectivity, and service latency. This article provides a systematic overview of the state-of-theart design of the NOMA transmission based on a unified transceiver design framework, the related standardization progress, and some promising use cases in future cellular networks, based on which interested researchers can get a quick start in this area.

Stochastic Geometry Analysis of Cellular Networks

Abstract: Achieve faster and more efficient network design and optimization with this comprehensive guide. Some of the most prominent researchers in the field explain the very latest analytic techniques and results from stochastic geometry for modelling the signal-to-interference-plus-noise ratio (SINR) distribution in heterogeneous cellular networks. This book will help readers to understand the effects of combining different system deployment parameters on key performance indicators such as coverage and capacity, enabling the efficient allocation of simulation resources. In addition to covering results for network models based on the Poisson point process, this book presents recent results for when non-Poisson base station configurations appear Poisson, due to random propagation effects such as fading and shadowing, as well as non-Poisson models for base station configurations, with a focus on determinantal point processes and tractable approximation methods. Theoretical results are illustrated with practical Long-Term Evolution (LTE) applications and compared with real-world deployment results.

User equipment and base station

Abstract: A user equipment UE includes: a measurer that measures, for each of a plurality of candidate beams, a benchmark pertaining to communication quality; a comparer that compares the benchmark with a first threshold value and a second threshold value; and a feedback unit that transmits the benchmark to the base station as feedback information pertaining to an interference beam if the benchmark is the first threshold value or higher and lower than the second threshold value, transmits the benchmark to the base station as feedback information pertaining to a desired beam if the benchmark is the second threshold value or higher, and transmits no feedback information to the base station if the benchmark is lower than the first threshold value, based on the comparison results of the comparer.

On Constellation Rotation of NOMA With SIC Receiver

Abstract: In this letter, we exploit constellation rotation to enhance the performance of uplink non-orthogonal multiple access (NOMA) with a successive interference cancellation receiver. We characterize the received signal with a Gaussian mixture model (GMM), where optimal rotation angle is obtained by maximizing the entropy of GMM. Then, we efficiently solve the entropy maximization problem by deriving an optimal closed-form approximate problem via variational approximation. Performance analysis and simulation results show that the proposed scheme achieves larger capacity and lower bit error rate compared with conventional NOMA. The performance gain is more significant with fewer receiving antennas or with smaller channel gain difference between multiplexed users.

Mobile edge computing with network resource slicing for Internet-of-Things

Abstract: Network slicing is an end-to-end concept that encompasses network functions, radio accesses, and clouds for enabling customized information-centric Internet-of-Things (IoT) services. The key idea is to virtualize all the resources from radio accesses to IoT service layers, so that IoT service providers can automate resource provisioning and management for users. This paper introduces the recent standards effort on network slicing for IoT in various standards bodies such as 3 GPP, NGMN, IETF, ET SI and oneM2M. In particular, standards activities on ET SI Multi-Access Edge Computing (MEC), NGMN and 3GPP Network Slicing and Virtualization, IETF slicing on transport networks and oneM2M IoT service layer resource slicing are introduced. Finally, this paper proposes a novel Edge Computing architecture customizing required network resources at the edge cloud, as close to users as possible, to minimize network signaling overhead in providing optimal IoT services.

Hybrid Beamforming With Selection for Multiuser Massive MIMO Systems

Abstract: This paper studies a variant of hybrid beamforming, namely, hybrid beamforming with selection (HBwS), as an attractive solution to reduce the hardware cost of multiuser Massive Multiple-Input-Multiple-Output systems, while retaining good performance. Unlike conventional hybrid beamforming, in a transceiver with HBwS, the antenna array is fed by an analog beamforming matrix with $\bar{L}$ input ports, where $\bar{L}$ is larger than the number of up/down-conversion chains $\bar{K}$ . A bank of switches connects the instantaneously best $\bar{K}$ out of the $\bar{L}$ input ports to the up/down-conversion chains. The analog beamformer is designed based on average channel statistics and therefore needs to be updated only infrequently, while the switches operate based on instantaneous channel knowledge. HBwS allows use of simpler hardware in the beamformer that only need to adjust to the statistics, while also enabling the effective analog beams to adapt to the instantaneous channel variations via switching. This provides better user separability, beamforming gain, and/or simpler hardware than some conventional hybrid schemes. In this paper, a novel design for the analog beamformer is derived and approaches to reduce the hardware and computational cost of a multiuser HBwS system are explored. In addition, we study how $\bar{L}$ , the switch bank architecture, the number of users and the channel estimation overhead impact system performance.

Coverage Enhancement for mm Wave Communications using Passive Reflectors

Abstract: Millimeter wave (mmWave) technology is expected to dominate the future 5G networks mainly due to large spectrum available at these frequencies. However, coverage deteriorates significantly at mm Wave frequencies due to higher path loss, especially for the non-line-of-sight (NLOS) scenarios. In this work, we explore the use of passive reflectors for improving mm Wave signal coverage in NLOS indoor areas. Measurements are carried out using the PXI-based mmWave transceiver platforms from National Instruments operating at 28 GHz, and the results are compared with the outcomes of ray tracing (RT) simulations in a similar environment. For both the measurements and ray tracing simulations, different shapes of metallic passive reflectors are used to observe the coverage (signal strength) statistics on a receiver grid in an NLOS area. For a square metallic sheet reflector of size 24 × 24 in2 and 33 × 33 in2, we observe a significant increase in the received power in the NLOS region, with a median gain of 20 dB when compared to no reflector case. The cylindrical reflector shows more uniform coverage on the receiver grid as compared to flat reflectors that are more directional.

Beam selection method, mobile station and base station

Abstract: A beam selection method, a mobile station and a base station are disclosed. A mobile station according to an aspect of the present invention, includes a receiving section configured to receive information for indicating a first quantity of reference signal resources and to receive beams corresponding to reference signals in the first quantity of reference signal resources, based on said information; and a selecting section configured to carry out channel estimation based on the received beams. The mobile station can reduce its workload and signaling overhead by carrying out channel estimation and feedback based on reference signals in the reference signal resources notified by a base station.

Channel Models and Measurements for 5G

Abstract: The fifth generation (5G) is expected to include new requirements, applications, and scenarios, and it will need massive and 3D multiple-input multiple output (MIMO), and increased spectrum via the use of millimeter-wave (mmWave) bands. The emerging techniques also pose new challenges to channel models. The articles in this special section examine the differences between propagation characteristics at microwave bands and at mmWave bands, summarize the current status of the 5G wireless channel modeling, and demonstrate the performance impact of channel models on system design and deployment. These considerations will enable simulation, evaluation, performance optimization, and network deployment of future 5G systems.

Fog Massive MIMO: A User-Centric Seamless Hot-Spot Architecture

Abstract: The decoupling of data and control planes, as proposed for 5G networks, will enable the efficient implementation of multitier networks where user equipment (UE) nodes obtain coverage and connectivity through the top-tier macro-cells, and, at the same time, achieve high-throughput low-latency communication through lower tiers in the hierarchy. This paper considers a new architecture for such lower tiers, dubbed fog massive MIMO, where the UEs are able to establish high-throughput low-latency data links in a seamless and opportunistic manner, as they travel through a dense fog of high-capacity wireless infrastructure nodes, referred to as remote radio heads (RRHs). Traditional handover mechanisms in dense multicell networks inherently give rise to frequent handovers and pilot sequence re-assignments, incurring, as a result, excessive protocol overhead and significant latency. In the proposed fog massive MIMO architecture, UEs seamlessly and implicitly associate themselves to the most convenient RRHs in a completely autonomous manner. Each UE makes use of a unique uplink pilot sequence, and pilot contamination is mitigated by a novel coded "on-the-fly" pilot contamination control mechanism. We analyze the spectral efficiency and the outage probability of the proposed architecture via stochastic geometry, using some recent results on unique coverage in Boolean models, and provide a detailed comparison with respect to an idealized baseline massive MIMO cellular system, that neglects protocol overhead and latency due to explicit user-cell association. Our analysis, supported by extensive system simulation, reveals that there exists a "sweet spot" of the per-pilot user load (number of users per pilot), such that the proposed system achieves spectral efficiency close to that of an ideal cellular system with the minimum distance user-base station association and no pilot/handover overhead.

Base station, user equipment, and method for determining precoding matrix

Abstract: A base station that communicates with a user equipment using multiple antenna ports includes an uplink channel estimation unit that estimates uplink channel states, a downlink channel estimation unit that estimates downlink channel states based on the estimated uplink channel states and channel reciprocity of uplink and downlink, a receiver unit that receives from the user equipment CSI feedback information, and a precoder generating unit that determines a precoding matrix of downlink based on Channel State Information (CSI) indicating the estimated downlink channel states and on the CSI feedback information.

Dynamic TDD and interference management towards 5G

Abstract: Dynamic time division duplex (TDD) is one promising way to improve the spectrum efficiency of the wireless communication networks since flexible traffic adaptation can be achieved by dynamically changing uplink (UL) or downlink (DL) transmission direction. However, it also brings some new challenges because of the introduction of cross-link interference, including DL-to-UL interference (e.g., gNB-to-gNB interference) and UL-to-DL interference (UE-to-UE interference). Besides, fully dynamic TDD is promising for 5G, which makes the interference management more intractable. In this paper, we investigate the interference management schemes for 5G dynamic TDD and propose a new interference suppression schemes using advanced receivers, e.g., minimum mean square error interference rejection and cancellation (MMSE-IRC) receiver and enhanced MMSE-IRC (eMMSE-IRC) receiver. The analytic expressions of MMSE-IRC and eMMSE-IRC receiver for dynamic TDD interference suppression are given by theoretical analysis. Also, one interference measurement scheme is proposed to support the proposed interference suppression schemes. The simulation results confirm the performance gain of the proposed interference suppression schemes compared with the baseline minimum mean square error (MMSE) receiver and show promising performance gain of dynamic TDD.

Key Technology for 5G New Radio

Abstract: The articles in this special section focus on 5G mobile communication. With initial commercialization expected in 2020, fifth generation (5G) mobile communications is gathering increased interest and momentum around the world. Following discussions on the 5G vision and key requirements such as high data rate, low latency, and massive connectivity, various candidate technologies have been proposed and investigated. These new technologies include massive antenna technologies to provide beamforming gain and support increased capacity, new waveforms to flexibly accommodate various services and applications with different requirements, and new multiple access schemes to support massive connections. From a spectrum point of view, there is also increased interest in the use of spectrum above 6 GHz for 5G mobile communications.

Combination of NOMA and MIMO: Concept and Experimental Trials

Abstract: Non-orthogonal multiple access (NOMA) is a novel multi-user multiplexing scheme that improves spectral efficiency for LTE enhancements and 5G. By overlapping radio resources (e.g., time/frequency/code), but assigning different powers to the multiplexed users, NOMA is able to improve the system performance and fairness. In this paper, we review the concept of combining downlink NOMA with MIMO. Then, we introduce our experiment trials conducted to assess the performance of downlink NOMA combined with MIMO under realistic conditions. The sets of experimental trials are conducted in outdoor environments, one using NOMA combined with open-loop 2×2 MIMO and another using NOMA combined with closed-loop 4×2 MIMO.

Enhanced uplink non-orthogonal multiple access for 5G and beyond systems

Abstract: Uplink non-orthogonal multiple access (NOMA) is a promising technique to meet the requirements of the fifth generation (5G) and beyond systems. Various NOMA schemes have been proposed in both academia and industry. However, most existing schemes assume equal average received power, which limits the performance. We propose three enhancements of uplink NOMA to achieve the requirements of massive connectivity and high reliability in 5G, where unequal average received power is exploited as part of the multiple access signature. First, the optimal sequences targeting to generalized Welch-bound equality (GWBE) are obtained for unequal average received power. Then user grouping with multi-level received powers is proposed for better successive interference cancellation (SIC) at the receiver. Finally, sequence grouping based on the cross-correlation properties of sequences is proposed to reduce inter- and intra-group interference. Simulation results show that by incorporating multi-level received powers and sequence grouping into existing NOMA schemes, for an NOMA system with 400% overloading and fixed signature allocation, 3 dB and 10 dB signal-to-noise ratio (SNR) gains at 0.1 block error rate (BLER) target can be achieved compared with existing NOMA schemes and orthogonal multiple access (OMA), respectively. Besides, 0.01 BLER target can be achieved while an error floor exists in existing NOMA schemes. Under random sequence selection, collision probability is reduced by multi-level powers. In addition, GWBE sequences achieve lower BLER than existing sequences and the gain is large especially for low BLER requirements. This shows that the proposed scheme can support larger connectivity and higher reliability.

Maritime 5G Experiment in Windsurfing World Cup by Using 28 GHz Band Massive MIMO

Abstract: The fifth-generation (5G) mobile communication system has attracted much attention to provide various kinds of services and applications for 2020 and later. To verify the feasibility of high presence public viewing service, the world's first maritime 5G experiment is conducted in Windsurfing World Cup 2018. In the experiment, 5G is used for 4K video transmission from a ship to public viewing area at land. This paper briefly reports that downlink and uplink maritime transmission performance of 5G employing 28 GHz band Massive MIMO (Multiple Input Multiple Output) and the success of the public viewing trial.

Non-Orthogonal Pilot Designs for Joint Channel Estimation and Collision Detection in Grant-Free Access Systems

Abstract: In this paper, we consider a densely deployed phantom cell system providing a low latency network for massive connectivity. Non-orthogonal pilot designs serve as a promising solution to support a large number of users, but fast collision detection at the receiver is needed for low latency networks. Recently, a nice solution based on an on–off type non-orthogonal pilot design with collision detection capability has been proposed. It can serve more users than the orthogonal pilot design but at the cost of degraded channel estimation performance compared to the orthogonal optimum pilot design. We propose a new non-orthogonal pilot design with collision detection capability and improved channel estimation performance. An optimum threshold-based detection criterion is developed. We further show that a dynamically calculated optimum threshold-based detection outperforms a fixed threshold-based detection. Next, we investigate non-orthogonal pilot designs for fractional bandwidth allocation. We propose two new non-orthogonal pilot designs for physical resource block based resource allocation. Both of the new designs support fast collision detection at the receiver. Performance evaluation results show that the proposed schemes provide equivalent or better channel estimation performance and support much more users than the orthogonal pilots defined in the current 4G standards. Finally, we explore sparse channel estimation with compressed sensing technique. We prove several propositions regarding compressed sensing based estimation performance. Using these propositions, two novel orthogonal pilot designs are developed for sparse channel estimation with optimized performances. Finally, utilizing these orthogonal pilot sets, we propose a non-orthogonal pilot design with collision detection capability for sparse channel estimation.

Improving Channel Capacity in Indoor $4 \times 4$ MIMO Base Station Utilizing Small Bidirectional Antenna

Abstract: Preparing toward the new-generation communication by improving the capacity in the channel can be achieved by employing a MIMO system with polarization diversity means. This paper presents a low-profile $4 \times 4$ MIMO bidirectional antenna consisting of two composite antennas mounted on a ground plane. The composite antenna is constructed by stacking a notch antenna and a loop antenna on top of each other and each antenna is fed independently. This antenna is capable of dual-polarized radiation patterns pointing in two different directions, where the notch antenna produces a horizontally polarized wave in the ${x}$ -axis direction while the loop antenna gives a vertically polarized wave in the ${y}$ -axis direction. The combination of two composite antennas has good isolation between the elements and is capable of improving the channel capacity for indoor MIMO base station applications. This paper includes the validation of both the fabrication of the proposed antenna design and the channel propagation measurement using the proposed antenna, confirming the excellent antenna performance for long term evolution application at a frequency of 3.5 GHz.

Method of wireless communication and user equipment

Abstract: A method of wireless communication using an unlicensed band includes performing, with a first transceiver, Listen-Before-Talk (LBT) in the unlicensed band, after the first transceiver has performed the LBT, transmitting a first signal from the first transceiver to a second transceiver in the unlicensed band, and after the first transceiver has transmitted the first signal, transmitting a second signal from the second transceiver to the first transceiver in the unlicensed band without the second transceiver performing the LBT.

Chemotherapy for Well-Differentiated Pancreatic Neuroendocrine Tumours with a Ki-67 Index ≥10%: Is There a More Effective Antitumour Regimen? A Retrospective Multicentre Study of the French Group of Endocrine Tumours (GTE)

Abstract: Background: The best chemotherapy regimen for well- differentiated pancreatic neuroendocrine tumours (pNETs) with a Ki-67 index ≥10% is still debated. We evaluate

Effect of Passive Reflectors for Enhancing Coverage of 28 GHz mmWave Systems in an Outdoor Setting

Abstract: The availability of large unused spectrum at millimeter wave (mmWave) frequency bands has steered the future 5G research towards these bands. However, mmWave signals are attenuated severely in the non-lineof-sight (NLOS) scenarios, thereby leaving the strong link quality by a large margin to line-of-sight (LOS) links. In this paper, a passive metallic reflector is used to enhance the coverage for mmWave signals in an outdoor, NLOS propagation scenarios. The received power from different azimuth and elevation angles are measured at 28 GHz in a parking lot setting. Our results show that using a 33 inch by 33 inch metallic reflector, the received power can be enhanced by 19 dB compared to no reflector case.

On-the-Fly Large-Scale Channel-Gain Estimation for Massive Antenna-Array Base Stations

Abstract: We propose a novel scheme for estimating the large- scale gains of the channels between user terminals (UTs) and base stations (BSs) in a cellular system. The scheme leverages TDD operation, uplink (UL) training by means of properly designed non-orthogonal pilot codes, and massive antenna arrays at the BSs. Subject to Q resource elements allocated for UL training and using the new scheme, a BS is able to estimate the large- scale channel gains of K users transmitting UL pilots in its cell and in nearby cells, provided K <=Q^2. Such knowledge of the large-scale channel gains of nearby out-of-cells users can be exploited at the BS to mitigate interference to the out-of-cell users that experience the highest levels of interference from the BS. We investigate the large-scale gain estimation performance provided by a variety of non-orthogonal pilot codebook designs. Our simulations suggest that among all the code designs considered, Grassmannian line-packing type codes yield the best large-scale channel gain estimation performance.

CamTrackPoint: Camera-Based Pointing Stick Using Transmitted Light through Finger

Abstract: We present CamTrackPoint, a new input interface that can be controlled by finger gestures captured by front or rear cameras of a mobile device. CamTrackPoint mounts a 3D-printed ring on the camera's bezel, and it senses the movements of the user's finger by tracking the light passed through the finger. The proposed method provides mobile devices with a new input interface that offers physical force feedback like a pointing stick. The cost of our method is low as it needs only a simple ring-shaped part on the camera bezel. Moreover, the ring doesn't disturb the functions of the camera, unless a user uses the interface. We implement a prototype for a smartphone; two CamTrackPoint rings are made for the front and rear cameras. We evaluate its performance and characteristics in an experiment. The proposed technique provides smooth scrolling and would give better game experience on the available smartphone.

Physiological Stress Level Estimation Based on Smartphone Logs

Abstract: Recently, inferring the state of people’s mental health via passive mobile sensing has attracted significant attention. Previous studies have used the self-assessed stress levels as the ground truth; however, these are subjective measures. In this study, we use a physiologically-assessed stress metric to minimize the effect of participant subjectivity and further estimate it using behavioral features based on the smartphone usage logs. We initially requested the study participants (39 participants) to attach heart rate sensors for 8 hours per day and simultaneously collected continuous heart rate data and smartphone logs for 42 days. Further, we divided the participants into four types via clustering using the behavioral features derived from their smartphone sensor logs and trained each model via supervised learning using the heart rate data as the ground truth. Our results exhibit that the proposed method is more accurate (71%) as compared to the baseline method (54%). This demonstrates that physiologically-assessed stress levels can be estimated based on the implicit features that are gathered from the smartphone logs.

5G Downlink Throughput Performance of 28 GHz Band Experimental Trial at 300 km/h

Abstract: Field trials of the fifth-generation (5G) mobile communication system using 28 GHz band at which almost 1-GHz band will be available have been performed all over the world. To realize large coverage at such a high frequency band, beamforming by Massive MIMO (Multiple Input Multiple Output) is necessary to compensate large path loss. Furthermore, beam tracking which adaptively changes beam direction according to user location is an important function to support user mobility. Authors already conducted high mobility trials at a velocity of 150 km/h using 28 GHz-band 5G prototypes implementing beam tracking. To support ultra-high mobility on a bullet train, in April 2018, we conducted outdoor trials using the specially customized vehicle with the velocity of up to 300 km/h. This paper reveals the latest downlink performance results of the trial.

Progressive Neural Network-based Knowledge Transfer in Acoustic Models

Abstract: This paper presents a novel deep neural network architecture for transfer learning in acoustic models. A well-known approach for transfer leaning is using target domain data to fine-tune a pre-trained model with source model. The model is trained so as to raise its performance in the target domain. However, this approach may not fully utilize the knowledge of the pre-trained model because the pre-trained knowledge is forgotten when the target domain is updated. To solve this problem, we propose a new architecture based on progressive neural networks (PNN) that can transfer knowledge; it does not forget and can well utilize pre-trained knowledge. In addition, we introduce an enhanced PNN that uses feature augmentation to better leverage pre-trained knowledge. The proposed architecture is challenged in experiments on three different recorded Japanese speech recognition tasks (one source and two target domain tasks). In a comparison with various transfer learning approaches, our proposal achieves the lowest error rate in the target tasks.

Rate-Adaptive Multiple Access for Uplink Grant-Free Transmission

Abstract: Grant-free transmission, which simplifies the signaling procedure via uplink instant transmission, has been recognized as a promising multiple access protocol to address the massive connectivity and low latency requirements for future machine type communications. The major drawback of grant-free transmission is that the contaminations among uncoordinated transmissions can reduce the data throughput and deteriorate the outage performance. In this paper, we propose a rate-adaptive multiple access (RAMA) scheme to tackle the collision problems caused by the grant-free transmission. Different from the conventional grant-free (conv-GF) scheme which transmits a single signal layer, RAMA transmits the signals with a multilayered structure, where different layers exhibit unequal protection property. At the receiver, the intra- and interuser successive interference cancellation (SIC) receiving algorithm is employed to detect multiple data streams. In RAMA, the users can achieve rate adaptation without the prior knowledge of the channel conditions, since the layers with high protection property can be successfully recovered when the interference is severe, while other layers can take advantage of the channel when the interference is less significant. Besides, RAMA also facilitates the SIC receiving since the multiple layers in the transmission signals can provide more opportunities for interference cancellation. To evaluate the system performance, we analyze the exact expressions of the throughout and the outage probability of both conv-GF and RAMA. Finally, theoretical analysis and simulation results validate that the proposed RAMA scheme can simultaneously achieve higher average throughput and lower outage performance than conv-GF. Meanwhile, RAMA shows its robustness with large user activation probability, where the collisions among users are severe.

Effectiveness of mobile application for menstrual management of working women in Japan: randomized controlled trial and medical economic evaluation

Abstract: Aims: Hormonal imbalances can affect a woman’s physical and mental condition, impacting her daily life and productivity. A mobile application, “Karada-no-kimochi”, predicts the menstrual cycle based on recorded data, and provides the information regarding menstruation. This study investigates the effectiveness of the application from health condition and labor productivity loss perspectives, and evaluates its cost-effectiveness for employed women in Japan.Materials and methods: A randomized controlled trial (RCT) was performed to compare the use of the application and non-intervention in female workers (20–45 years) based on an online survey. A discrete-event model based on the RCT data, published literature, and claims data was used for the cost-effectiveness analysis.Results: The intervention and non-intervention groups comprised 612 and 914 women, respectively. In the intervention group, the incidences of depression (0.16%) and dysmenorrhea (0.33%) were significantly lower than those of the non...