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.

Considerations on downlink non-orthogonal multiple access (NOMA) combined with closed-loop SU-MIMO

Abstract: As a promising downlink multiple access scheme for further cellular enhancements toward 5G, non-orthogonal multiple access (NOMA) improves both cell average and cell-edge user throughput compared to orthogonal multiple access (OMA) in the cellular downlink. When NOMA is combined with multi-antenna technology in practice, some aspects are of great interest, such as error propagation (EP) of successive interference cancellation (SIC) receiver and user velocity. This paper investigates the system-level throughput of NOMA with closed-loop single-user multiple-input multiple-output (SU-MIMO) in the cellular downlink and clarifies the potential gains over OMA with SU-MIMO taking into account these practical aspects. Two EP models are presented into the NOMA with closed-loop (CL) SU-MIMO. Their impacts on performance of NOMA with CL SU-MIMO are investigated by system-level simulations with practical assumptions. Furthermore, impact of user velocity on performance gain of NOMA with CL SU-MIMO is also evaluated. Simulation results show that even with the worst case EP model, NOMA with CL SU-MIMO can still provide large performance gains for both low and high mobility scenarios.

Security group management system

Abstract: A security group management system includes a cellular mobile station ( 2 ), two or more devices ( 3 ) belonging to a group, and a group management server ( 1 ). The group management server comprises a storage unit ( 11, 13 ) configured to store information about the cellular mobile station registered by a member of the group and group information about the group in advance; and a group information providing unit ( 16 ) configured to supply the group information in response only to an access from the registered cellular mobile station. The cellular mobile station has a group information transmission unit ( 23 ) configured to supply the group information to the devices so as to allow the devices to recognize that the devices belong to the group and to perform secure mutual connection and/or resource sharing among the devices.

Method and associated apparatus for pre-authentication, preestablished virtual private network in heterogeneous access networks

Abstract: A method of coordinating the handoff of a mobile carrier between a first access network and a second access network. The method including establishing a contract between a user of a mobile carrier and a hyper operator and attempting a hand off from a first access network that the mobile carrier is currently operating within to a second access network, wherein the attempting includes authenticating at the hyper operator only that the user may have access to the second access network via the contract. Handing off to the second access network if the authenticating is successful.

Base station, receiving device, mobile terminal and frequency sharing method

Abstract: A disclosed base station is used in a first wireless communication system using a first frequency band that is the same as or adjacent to a second frequency band used by a second wireless communication system, and includes a propagation loss estimation unit configured to estimate propagation loss of a signal in the first frequency band when the signal arrives at a receiving device of the second wireless communication system; a frequency difference calculation unit configured to calculate a frequency difference between the first frequency band and the second frequency band; a maximum transmission power determining unit configured to determine maximum transmission power based on the estimated propagation loss and the calculated frequency difference; and a transmission control unit configured to transmit a signal with transmission power less than or equal to the maximum transmission power determined by the maximum transmission power determining unit.

Turbo-reception method and turbo-receiver

Abstract: An impluse response hmn(q) of each transmission path is estimated from N received signals rm (m=1, . . . , M) and a known signal (for a number of users equal to N, n=1, . . . , N). M×N matrix H (q) having hmn(q) as an element and a Q×Q matrix H having H(q) as an element are determined (where Q represents a number of multipaths of each transmitted wave and q=0, . . . , Q−1). A soft decision value b′n(k) is determined from decoded λ2 [bn(k)], and this is used to generate an interference component matrix B′(k) to generate an interference replica H·B′(k). The interference replica H·B′(k) is subtracted from a received matrix y(k) to determine y′(k). y(k) and H are used to determine an adaptive filter coefficient wn(k) to be applied to an n-th user in order to eliminate residual interference components in y′(k) according to the minimum mean square error criteria. y(k) is passed through wn(k) to provide a log-likelihood ratio as a received signal from the user n from which interferences are eliminated.