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.

Map information display device, map information display method, and map information display program

Abstract: A map information display device (1) comprises: a touch panel (11) for displaying map information while accepting a touch operation from a user; a touch position detector (12) for detecting a touch position on a touch panel (11); a building determination unit (16) for determining whether or not a building with displayable internal information exists in the map information displayed on the touch panel (11); and a floor-selection menu display processing unit (18) for displaying a floor selection menu having selection items corresponding to displayable floors near the touch position on the touch panel (11) when the building determination unit (16) determines that a building with displayable internal information exists.

Differential Codebook MIMO Precoding Technique

Abstract: In this paper, we present a differential codebook precoding technique for MIMO spatial multiplexing systems. The proposed scheme updates the precoding matrix by multiplying the codebook matrix specified by the receiver to the previous precoding matrix. The codebook matrices are designed to include quasi-diagonal matrices for finer quantization of the channel. We analyze the capacity of the differential precoding scheme as well as existing precoding schemes by taking into account various practical aspects such as precoding update interval, feedback delay, and feedback error. Simulation results show that in a MIMO system with four transmit and two receive antennas, the proposed precoding scheme requires smaller codebook size by about 1 - 2 bits than the one-shot precoding scheme with Grassmannian codebook to achieve the same capacity level when the channel variation is relatively small. Finally, we show that the proposed precoding scheme provides similar throughput performance gain in MIMO-OFDM systems in frequency selective fading channels.

Method for iterative interference cancellation for co-channel multi-carrier and narrowband systems

Abstract: In a co-channel deployment of narrowband and multi-carrier technologies (e.g., a femtocell and a macrocell), a method provides cancelling of interference which treats the co-channel signals as desired signals and enhances each of them iteratively. At each iteration, each signal is demodulated and regenerated based on symbol decisions already made and a predetermined channel impulse response. To estimate the other (interfering) co-channel signal, the regenerated signal is subtracted from the aggregate signal. Simulations have shown that a method of the present invention can provide fundamental improvement in the performances of both interfering systems in as few as two iterations. The fundamental performance gain that can be obtained outweigh the required computational burden.

Secure route optimization for mobile network using multi-key cryptographically generated address

Abstract: A method allows a mobile router that uses the Mobile Internet Protocol version 6 (Mobile IPv6) for mobility management to optimize routing by securely sending binding update messages directly to correspondent nodes on behalf of each mobile network node, even if the node does not perform Mobile IPv6 functions. Since the network address for each mobile network node is generated from the public keys of both the mobile network node and the mobile router, the mobile router is authorized to use the generated address on behalf of the mobile network node. If the mobile router changes its point of attachment, it sends signed binding update messages to the correspondent nodes of the mobile network nodes. When the correspondent nodes verify the binding update message and the correct public keys, the correspondent nodes can communicate with the mobile network node without going through the home agent. Therefore, secure proxy binding update messages can be sent from the mobile router.

Message transmission system and message transmission method

Abstract: A message transmission system includes a registration accepting part for accepting a membership number, a subscriber telephone number, and a subscribed service ID; a subscriber information storage for storing membership numbers, subscriber telephone numbers, and subscribed service IDs in association with each other; a transmission request receiver for receiving a membership number of a message destination and a service ID of a Web server from the Web server or from communication terminal; a communication address converter for referring to the subscriber information storage on the basis of the received membership number and service ID to retrieve the subscriber telephone number corresponding to the membership number and service ID; and a message output part for outputting a predetermined message while designating the retrieved subscriber telephone number.