NTT DoCoMo

About: NTT DoCoMo is a based out in . It is known for research contribution in the topics: Base station & Mobile station. The organization has 4032 authors who have published 8655 publications receiving 160533 citations.

Resource control method, mobile communication system, base station and mobile station

Abstract: To provide a service with fairness by providing QoS of approximately an equal degree among users of the same service class to keep fairness of the service as well as by maintaining a transmission rate at a predetermined ratio among users of different service classes to relatively keep QoS among service classes. A resource control method which is executed by a base station in a mobile communication between the base station and each of a plurality of mobile stations, the method comprising: an unallocated resource measurement step of measuring an amount of unallocated resources, when one mobile station originates a new connection request or a handover request; a service quality calculation step of calculating a service quality which can be provided to the one mobile station with the amount of the unallocated resources obtained by the measurement; a decision step of deciding whether the service quality obtained by the calculation is within a predetermined range in accordance with a service class to which the one mobile station belongs; and a reassignment step for reassigning the resources to each mobile station depending on the service class to which each mobile station belongs, when the service quality is not within the predetermined range in accordance with the service class to which the one mobile station belongs.

Absence of mutagenic effects of 2.45 GHz radiofrequency exposure in spleen, liver, brain, and testis of lacZ-transgenic mouse exposed in utero.

Abstract: A possible mutagenic effect of 2.45 GHz radiofrequency exposure was examined using lacZ-transgenic Muta mice. Pregnant animals were exposed intermittently at a whole-body averaged specific absorption rate of 0.71 W/kg (10 seconds on, 50 seconds off which is 4.3 W/kg during the 10 seconds exposure). Offspring that were exposed in utero for 16 hours a day, from the embryonic age of 0 to 15 days, were examined at 10 weeks of age. To minimize thermal effects, the exposure was given in repeated bursts of 10 seconds of exposure followed by 50 seconds of no exposure. Mutation frequencies at the lacZ gene in spleen, liver, brain, and testis were similar to those observed in non-exposed mice. Quality of mutation assessed by sequencing the nucleotides of mutant DNAs revealed no appreciable difference between exposed and non-exposed samples. The data suggest that the level of radiofrequency exposure studied is not mutagenic when administered in utero in short repeated bursts.

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.

Plug-and-Play Composition of Features and Feature Interactions with Statechart Diagrams.

Abstract: This paper presents a new approach for modular design of highly-entangled software components by statechart diagrams. We structure the components into features, which represent reusable, self-contained services. These are modeled individually by statechart diagrams. For composition of components from features, we need to consider the interactions between the features. These feature interactions, well known in the telecommunications area, typically describe special cases or cooperations which only occur when two features are combined. We describe these interactions graphically by refinement relations between statecharts. The main novelty is that full component descriptions are created in a plug-and-play fashion by combining the statecharts for the required features and interactions. Furthermore, we develop different classes of statecharts and show the interactions on a case-by-case basis. For composition, we use semantic refinement concepts for statecharts which preserve the original behavior.

Digital predistorter using power series model

Abstract: A digital predistorter compensates for nonlinear distortion of a power amplifier using a power series model. The digital predistorter includes a distortion generating unit configured to introduce a nonlinear distortion component of a prescribed order into a digital input signal supplied to the digital predistorter. The distortion generating unit has a multiplier configured to raise the digital input signal to a power consistent with the prescribed order of the nonlinear distortion component, and a finite impulse response filter connected in series with the multiplier. The digital predistorter also includes an adaptive controller configured to receive a reference signal and adaptively adjust the tap coefficient of the finite impulse response filter so as to bring the reference signal to a desired level.