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.

IP-based IMT network platform

Abstract: This article describes a network platform with future IP-based techniques for "beyond IMT-2000." First, it presents a vision for beyond IMT-2000 in terms of requirements for service and network capabilities. Next, it shows a general architecture of the IP-based IMT network platform (IP/sup 2/). Then it discusses the study of key network techniques (location management, routing/handover, and service management) featured in the proposed platform architecture.

Moving picture encoding/transmission system, moving picture encoding/transmission method, and encoding apparatus, decoding apparatus, encoding method decoding method and program usable for the same

Abstract: An object of the present invention is to allow portions which are subjected to a coding in inter-frame prediction mode and portions which are subjected to coding in intra-frame prediction mode to be mixed in one macro block without changing the framework of macro blocks. The present invention provides an encoder which encodes each of first image blocks of a video. The encoder includes prediction mode selection information generating means for generating prediction mode selection information which indicates that a first prediction mode for reducing temporal redundancy is applied to each of second image blocks or that a second prediction mode for reducing spatial redundancy is applied to each of the second image blocks. The second image blocks are obtained by dividing the first image blocks. The encoder includes predictive residual signal generating means for generating a predictive residual signal by applying the selected first or second prediction mode to each of the second image blocks. The encoder includes transmitting means for transmitting the prediction mode selection information in association with the predictive residual signal.

Subspace Alignment Chains and the Degrees of Freedom of the Three-User MIMO Interference Channel

Abstract: We show that the 3 user M_T x M_R MIMO interference channel has d(M,N)=min(M/(2-1/k),N/(2+1/k)) degrees of freedom (DoF) normalized by time, frequency, and space dimensions, where M=min(M_T,M_R), N=max(M_T,M_R), k=ceil{M/(N-M)}. While the DoF outer bound is established for every M_T, M_R value, the achievability is established in general subject to normalization with respect to spatial-extensions. Given spatial-extensions, the achievability relies only on linear beamforming based interference alignment schemes with no need for time/frequency extensions. In the absence of spatial extensions, we show through examples how essentially the same scheme may be applied over time/frequency extensions. The central new insight to emerge from this work is the notion of subspace alignment chains as DoF bottlenecks. The DoF value d(M,N) is a piecewise linear function of M,N, with either M or N being the bottleneck within each linear segment. The corner points of these piecewise linear segments correspond to A={1/2,2/3,3/4,...} and B={1/3,3/5,5/7,...}. The set A contains all values of M/N and only those for which there is redundancy in both M and N. The set B contains all values of M/N and only those for which there is no redundancy in either M or N. Our results settle the feasibility of linear interference alignment, introduced by Cenk et al., for the 3 user M_T x M_R MIMO interference channel, completely for all values of M_T, M_R. Specifically, the linear interference alignment problem (M_T x M_R, d)^3 (as defined in previous work by Cenk et al.) is feasible if and only if d<=floor{d(M,N)}. With and only with the exception of the values M/N\in B, we show that for every M/N value there are proper systems that are not feasible. Our results show that M/N\in A are the only values for which there is no DoF benefit of joint processing among co-located antennas at the transmitters or receivers.

Position registration method, information distribution method, mobile communication network, and mobile communication terminal

Abstract: A base station (21) provided in a specific portion of a position registration area broadcasts an ID signal representing the base station ID. A mobile station (10) residing in a radio zone of the base station (21), on receiving the ID signal, transmits a position registration request signal including the base station ID and the mobile station ID to the base station (21). In a home memory (23), the base station ID and the mobile station ID are registered as small zone position registration information. An IP server (40a) acquires position-associated information from a position-associated information database (41a) and sends it to a gateway server (25). The gateway server (25) specifies the object to which the received position-associated information is to be sent referring to the home memory (23) and sends it to the mobile station (10).

Theoretical analysis of reverse link capacity for an SIR-based power-controlled cellular CDMA system in a multipath fading environment

Abstract: Capacity estimation in a code-division multiple-access system is closely related to power control schemes, which complicates the analysis due to the interaction between the signal power and the interference from other users and from other paths. For a signal-to-interference ratio (SIR)-based power control scheme, most previous work has been restricted to a single-cell system or to a multiple-cell system neglecting the effect of multipath fading. This paper is to give a theoretical foundation to the possible reverse link capacity of a multiple-cell system with perfect SIR-based power control, assuming two different multipath Rayleigh fading channel models: uniform and exponential power delay profiles. The effects of the numbers of resolvable propagation paths and RAKE fingers, and other system parameters such as the required E/sub b//I/sub 0/, the processing gain, and the maximum allowable transmit power of a mobile station, are investigated. The results are compared between single- and multiple-cell systems. When the number of resolvable paths is one or the number of Rake fingers is one, the link capacity becomes zero in a multiple-cell environment. This can be avoided by the use of antenna diversity. Antenna diversity reception is found to linearly increase the link capacity as the number of antennas increases.