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.

Downlink mimo transmission control method and base station apparatus

Abstract: A method of controlling downlink transmission from a base station having multiple antennas to a mobile station having multiple antennas includes the steps of applying open loop-type MIMO diversity to one or more common control channels, an MBMS channel, and an L1/L2 control channel; and applying closed loop-type MIMO multiplexing and/or MIMO diversity to a shared data channel.

Differential multiple-length transmit and reception diversity

Abstract: The present invention achieves differential transmit diversity and related diversity reception schemes transmit symbol constellations which are extended to multiple levels. Heretofore, a group of transmission bits is divided into a first sub-group of transmission bits and a second sub-group of transmission bits. Then, the first sub-group of transmission bits is mapped (14) onto constellation points of a differential transmit diversity coding scheme from an orthogonal design for coding of the first sub-group of transmission bits. Then, after differential encoding of the constellation points (32, 34, 36, 40) a length of the transmission symbol vector is scaled (38) for coding the second sub-group of transmission bits. Therefore, the present invention overcomes restrictions implied through unit length requirements for previously known differential transmit diversity schemes from orthogonal designs.

Investigation on elevation beamforming for future LTE-Advanced

Abstract: This paper investigates and analyzes three typical elevation beamforming scenarios which are most likely to be applied in future LTE-Advanced systems: vertical sectorization with same carrier frequency, vertical sectorization with different carrier frequency based on carrier aggregation, and user-specific elevation beamforming. Preliminary evaluation using WINNERII/WINNER+ based 3D MIMO channel modeling is carried out to compare these scenarios with the conventional system with single downtilting. It is shown that the latter two elevation beamforming scenarios can achieve good performance.

Peer Assisted Video Streaming With Supply-Demand-Based Cache Optimization

Abstract: In this paper, we consider a hybrid P2P video on-demand architecture that utilizes both the server and the peer resources for efficient transmission of popular videos. In our system architecture, each peer dedicates some cache space to store a particular segment of a video file as well as some of its upload bandwidth to serve the cached segment to other peers. Peers join the system and issue a streaming request to a control server. Control server directs the peers to streaming servers or to other peers who have the desired video segments. Control server also decides which peer should cache which video segment. Our main contribution in this paper is to determine the proper caching strategies at peers such that we minimize the average load on the streaming servers. To minimize the server load, we pose the caching problem as a supply-demand-based utility optimization problem. By exploiting the inherent structure of a typical on-demand streaming application as well as the availability of a global view on the current supply-demand at the control server, we demonstrate how the system performance can be significantly improved over the brute-force caching decisions. In our analysis, we mainly consider three caching mechanisms. In the first mechanism (cache prefetching), a segment is prefetched to a given peer for caching purposes upon peer's arrival to the system regardless of whether that segment is currently demanded by that peer or not. In the second mechanism (opportunistic cache update), a peer has the option of replacing the segment that is currently in its cache with the last segment that it finished streaming. In the third mechanism, we combine both mechanisms as a hybrid caching strategy. In particular, we find that a dynamic-programming (DP)-based utility maximization solution using only the cache update method performs significantly better in reducing the server load. Furthermore, our findings suggest that even less sophisticated cache update solutions can perform almost as good as prefetching strategies in interesting regions of operation.

Transmitting apparatus and transmitting method

Abstract: A transmitting apparatus uses one or more frequency blocks, each of which includes one or more carrier frequencies, to transmit data to the other end(s) of communication, which is in a better channel condition, on a priority basis. The transmitting apparatus comprises a selecting means that evaluates the channel condition of each of the other ends of communication for each frequency block and selects at least one of the other ends of communication; a deciding means that decides at least a modulation scheme in accordance with the evaluated channel condition; a means that creates a control channel indicative of the decided modulation scheme and also indicative of one or more frequency blocks that can be used for the selected other end of communication to receive the data; and a transmitting means that transmits, to the selected other end of communication, the control channel and a data channel modified by use of the foregoing modulation scheme.