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.

Toward LTE commercial launch and future plan for LTE enhancements (LTE-Advanced)

Abstract: As a promising radio access technology for next generation mobile communication systems, LTE (Long-Term Evolution) is being standardized by the 3rd Generation Partnership Project (3GPP) international standardization organization. LTE Release 8 has many advantages to the other systems, e.g., the peak throughput is 300Mbps in Downlink (DL) and 75Mbps in Uplink (UL), 2–3 time higher spectrum efficiency than Rel. 6 HSPA (High Speed Packet Access), very low latency around 5msec in RAN (Radio Access Network) and 100msec for connection setup time. With Release 8, the first version for LTE specification, being completed in March 2009, the LTE standard is now being developed towards commercialization in various countries in the world. This paper addresses the plan for LTE commercial launch in NTT DOCOMO and future plan for LTE Rel. 9 and LTE-Advanced (LTE Rel. 10 and beyond).

Transmission control scheme

Abstract: The present invention provides a transmission control scheme for wireless digital networks comprised of a plurality of access points each communicating with access terminals, which improves data throughput to access terminals located in areas where interference from the neighboring access points are high. Generally, under the transmission control scheme according to the present invention, the access points are controlled so that neighboring access points will not transmit signals simultaneously with transmission parameters providing high robustness. The transmission parameters include, for instance, transmission power, a modulation scheme and a coding rate. Higher power transmission achieves higher robustness. Transmission at a lower modulation level achieves higher robustness. Transmission at a lower coding rate achieves higher robustness. Transmission providing high or low robustness will expand or narrow a virtual communication zone, which is defined in this application as an area within which it is feasible at a given level of error performance for access terminals to communicate with the access point in the zone. The access points may change their transmission parameters according to predetermined schedules, such as at regular intervals.

Radio base station and mobile communication method

Abstract: A radio base station includes a resource assignment unit for assigning a resource candidate for transmitting a semi-persistent scheduling transmission acknowledgement signal to a first mobile station during a semi-persistent scheduling bearer setting process. The resource candidate for transmitting a semi-persistent scheduling transmission acknowledgement signal is formed by a combination of a frequency direction resource and a code direction resource by which the first mobile station transmits a transmission acknowledgement signal after a predetermined timing from a timing of receiving downlink data, to the downlink data that has been scheduled by semi-persistent scheduling and has been transmitted via a downlink data channel. The resource assignment unit is configured to assign the resource candidate for transmitting a semi-persistent scheduling transmission acknowledgement signal to the first mobile station based on a number of assignments of predetermined resources formed by a combination of a frequency direction resource and a code direction resource.

Rethinking network MIMO: Cost of CSIT, performance analysis, and architecture comparisons

Abstract: We compare the downlink throughput of various cellular architectures with multi-antenna base stations and multiple single-antenna users per cell, by considering a number of inherent physical layer issues such as path-loss and time and frequency selective fading. In particular, we focus on Multiuser MIMO (MU-MIMO) downlink techniques that require channel state information at the transmitter (CSIT). Our analysis takes explicit account of the cost of CSIT estimation and illuminates the tradeoffs between CSIT, estimation error, and system resource dedicated to training. This tradeoff shows that the number of antennas that can be jointly coordinated (either on the same base station or across multiple base stations) is intrinsically limited not just by “external factors,” such as complexity and rate of the backbone wired network, but by the inherent time and frequency variability of the fading channels. Our analysis, in agreement with a number of recent simulation results, shows that conventional MU-MIMO cellular architectures may outperform schemes based on coordinated transmission from base stations (referred to as Network MIMO schemes, NW-MIMO), at the negligible cost of a few extra antennas per station. In light of these results, it appears that the inherent bottleneck of NW-MIMO systems is not the backbone network (which here is assumed ideal with infinite capacity) but the intrinsic dimensional limitation of estimating the channels.

Mobile communication terminal and card information reading device

Abstract: A mobile communication terminal (the mobile station 100), served in a mobile communication network for performing wireless communications, comprises a transmitter-receiver 110, a controller 120, a user interface 130, a data input/output terminal 140, a magnetic writer 150, and a magnetic stripe 160. Control programs stored in a program ROM 122 include a program for controlling the magnetic writer such as writes or deletes various information into/from the magnetic stripe 160. In a credit card ROM 123 are stored information on the attributes of a credit card contract concluded in advance between a user and a credit card company. The magnetic writer 150 writes credit card contract information provided from the controller 120 to the magnetic stripe 160 or deletes the credit card contract information from the magnetic stripe 160.