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.

Methods and apparatus for wideband transmission based on multi-user mimo and two-way training

Abstract: A method, apparatus and system is disclosed herein for wireless transmission based on MU-MIMO and two-way training. In one embodiment, the system comprises a set of K receivers and at least one transmitter having a set of N transmit antennas, where the transmitter is operable to precode a signal for downlink transmission to each receiver in the set of K receivers based on multi-user MIMO using precoding derived based on two-way channel training between the set of K receivers and the set of N transmit antennas. In another embodiment, the method comprises a transmitter receiving K pilot symbols, each K pilot symbol being transmitted by one of the set of K receivers; estimating channels directly at the transmitter based on received K pilot symbols; deriving a MU-MIMO precoder using the channel estimates; transmitting 1 to K pilot symbols using the MU-MIMO precoder to the set of K receivers to enable the K receivers to estimate their respective effective channels; and sending a downlink transmission using the MU-MIMO precoder to at least one of the set of K receivers.

Content distribution system, description data distribution apparatus, content location management apparatus, data conversion apparatus, reception terminal apparatus, and content distribution method

Abstract: A content distribution system includes plurality of cache server apparatus configured to obtain content from a distribution apparatus, and to store the content temporarily; a location information data storage unit configured to store location information data, which indicates location information of each cache server apparatus; a description data storage unit configured to store at least one item of description data, which includes the location information of a distribution apparatus; a converter configured to convert the location information of a distribution apparatus storing a requested content, which is included in description data, into location information of a specified cache server apparatus, by referring to the location information data; and a reception terminal apparatus configured to obtain the description data converted by the converter, and to receive the requested content from the specified cache server apparatus.

Degrees of Freedom Characterization: The 3-User SISO Interference Channel with Blind Interference Alignment

Abstract: We characterize the degrees of freedom (DoF) of the 3-user Gaussian interference channel where each transmitter is equipped with a single conventional antenna and each receiver is equipped with one multi-mode antenna. By assuming that the channel is unknown to the transmitters and only known to the receivers, we show that by using linear blind interference alignment (BIA) with antenna switching at the receivers only, the sum DoF are \frac{6}{5}. The new insight behind this result is that any vector of a user aligned at one unintended receiver cannot be aligned at the other unintended receiver. This is the first complete characterization of the sum DoF when using BIA over the Gaussian Interference Channel. The DoF result under the temporal correlated channels is also discussed.

Base station apparatus, user equipment and method in mobile communication system

Abstract: A downlink control channel transmitted from a base station apparatus includes multiple control channel elements (CCEs), and different PUCCH resources are determined depending on which CCEs are associated with control information destined for user equipments. If a PDSCH in a certain subframe is assigned to a user equipment in an old system, the control information destined for the user equipment is assigned to a certain CCE, and a PDSCH in a subframe after a predefined time period from the certain subframe is assigned to a user equipment in a new system, the control information destined for the user equipment may be associated with a CCE different from the certain CCE. Alternatively, the control information destined for the user equipment in the second system may be associated with the same CCE as the control information destined for the user equipment in the first system but may be spread with different spread codes.

Controller, mobile station, mobile communication system and control method

Abstract: A disclosed control apparatus performs packet communications with a mobile station and divides a coverage area into plural sectors so as to control the communications. The control apparatus comprises a transmission allocation portion that selects at least two transmission sectors to perform transmission to the mobile station in accordance with reception quality imparted from the mobile station so as to perform a transmission allocation for the mobile station; and a transmission portion that uses an identical scramble code for sector identification so as to perform transmission to the mobile station.