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.

Mobile communication method and relay node

Abstract: A mobile communication method according to the present invention includes a step in which, when a relay node RN, which is subordinate to a radio base station DeNB and is in an “RRC_CONNECTED state”, received an “RRC connection release message” from the radio base station DeNB, the relay node RN is transitioned to an “RRC_IDLE state” after transmitting an “RRC connection release message” to a mobile station UE, which is subordinate to the relay node RN and is in the “RRC_CONNECTED state”, and a predetermined time T2 elapses.

High-Resolution TOA Estimation with Multi-Band OFDM UWB Signals

Abstract: In this paper, we propose a simple model-based time-of-arrival (TOA) estimation technique for multi-band orthogonal frequency division multiplexing (MB-OFDM) signals based on the ECMA-368 standard [1]. The proposed technique does not need oversampling at the receiver. The key idea is to minimize the energy leakage from the first channel path due to mis-sampling. We use realistic channel models and assume that no channel statistical information is known at the receiver. In our approach, the multi-band signals are coherently combined in order to improve the resolution of the TOA estimation. We compare the performance of the proposed scheme with the well-known maximum-likelihood based algorithm, namely, space-alternating generalized expectation-maximization (SAGE). Simulations based on the ECMA-368 standard parameters in both IEEE 802.15.3a and IEEE 802.15.4a standard channel models show that our approach outperforms the SAGE algorithm by avoiding the local maxima. Furthermore, we have also shown that our approach can achieve a root mean square error of TOA estimation much smaller than the receiver sampling interval and it is robust to the narrowband interference.

Design and operation of Blind Interference Alignment in cellular and cluster-based systems

Abstract: We consider the use of Blind Interference Alignment (BIA) in a cellular environment as a means for supporting downlink Multi-User MIMO (MU-MIMO) transmission without the need for channel state information at the transmitter (CSIT). This “CSIT-blind” characteristic of BIA is of particular interest for Frequency Division Duplex (FDD) systems, since it allows one to eliminate overheads and impairments due to downlink pilot training and CSIT quantization and feedback. As we demonstrate, when properly applied over cellular, BIA can enable control of both intra-cell and inter-cell interference. In this context, we explore the aspects of power-allocation, frequency reuse, and alignment-code reuse and their effect on cellular performance. BIA can also be jointly applied over clusters of cells. Cluster operation leads to lower inter-cell interference levels and potentially improved BIA system performance. BIA however, has some interesting operational aspects when used with clusters. These include some benefits over CSIT-based MU-MIMO since individual cells do not need to share channel knowledge and can transmit independent information streams, some challenges in more complex receiver hardware, and relationships to cellular with code-reuse. We discuss such aspects and investigate the application of BIA in both cellular and cluster deployments.

Mobile interaction with static and dynamic NFC-based displays

Abstract: This paper reports on a development framework, two prototypes, and a comparative study in the area of multi-tag Near-Field Communication (NFC) interaction. By combining NFC with static and dynamic displays, such as posters and projections, services are made more visible and allow users to interact with them easily by interacting directly with the display with their phone. In this paper, we explore such interactions, in particular, the combination of the phone display and large NFC displays. We also compare static displays and dynamic displays, and present a list of deciding factors for a particular deployment situation. We discuss one prototype for each display type and developed a corresponding framework which can be used to accelerate the development of such prototypes whilst supporting a high level of versatility. The findings of a controlled comparative study indicate, among other things, that all participants preferred the dynamic display, although the static display has advantages, e.g. with respect to privacy and portability.

Mobile terminal apparatus and radio base station apparatus

Abstract: There is provided a mobile terminal apparatus and a radio base station apparatus capable of transmitting a downlink signal using an optimum feedback parameter even when a control delay exists and improving throughput characteristics of a downlink channel. A mobile terminal apparatus (1) measures a feedback parameter for a radio base station apparatus (3) using a received signal, obtains a feedback value, predicts a feedback parameter after a control delay in which the feedback value is reflected on transmission of a downlink shared channel to obtain a feedback predicted value, transmits the feedback predicted value to the radio base station apparatus, and the radio base station apparatus (3) selects a precoding weight of MIMO channel transmission using the feedback predicted value and schedules the downlink shared channel using the feedback predicted value.