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.

Correlation detector and communication apparatus

Abstract: A correlation detector for CDMA communication receivers, which can establish synchronization at a high speed, can extract mutually correlated components, and can perform highly accurate tracking. The received signal (21) is fed to a matched filter (43) when the initial synchronization is established. When a synchronization judging circuit (45) judges that the filter (43) detects synchronization, the switching circuit (42) feeds the signal (21) to multipliers (47, 48), and resets a VCCG (29) and a spread-spectrum code replica generator (30). After the synchronization is established, the spread-spectrum signal is detected quasi-synchronously, the received signal quasi-synchronously detected is multiplied by replical codes having advanced and lagged phases, and correlation detection signals are extracted from the multiplication results. The square components are generated, added together in opposite phases, and averaged in the time direction. The received spread-spectrum signal is multiplied by the codes whose phases are synchronous, and the results are integrated over chips. The signal, after the averaging processing, is reversely modulated by use of the identification signal of the received data obtained by compensation for the phase error of the received signal in order to generate a phase error signal. The replica code generator is driven by a clock the phase of which is controlled by the phase error signal.

Secure network access method

Abstract: The present invention provides network-layer authentication protocols for authenticating mobile client and access router to each other. The present invention uses Router Discovery as a carrier to implement the authentication protocols. In an embodiment of the present invention, a mobile client sends out a solicitation message to request connectivity service. The solicitation message contains a proof of identity of the mobile client. An access router that receives the solicitation message will not respond to it until the proof of the identity is verified. Only when the proof of identity of the mobile client is verified, will the access router respond and return an advertising message to the mobile client, thereby preventing unauthorized mobile clients from obtaining network access.

Wireless base station network system, control station, base station switching method, signal processing method, and handover control method

Abstract: A wireless base station network system in which base stations arranged at a plurality of cells and a control station for controlling the base stations are connected through optical fibers by wavelength-division multiplexing transmissions. The base station is provided with a wavelength-variable transmitter for transmitting optical signals of a predetermined wavelength, and an optical coupler for multiplexing optical signals from the wavelength-variable transmitter for the wavelength-division multiplexing transmissions. The control station is provided with a plurality of optical receivers for receiving the divided and multiplexed wavelengths of the optical signals, and an optical coupler for branching the optical signals having been divided and multiplexed from the plurality of base stations, individually to the wavelengths. Where the wireless communication terminal to communicate with the base station moves to change its communicating base station, a new base station, to which the wireless communication terminal has moved, controls the wavelength of the wavelength variable transmitter and transmits the optical signal wavelength identical to that transmitted by the base station before the movement, to the control station.

Performance evaluation of inter-cell interference coordination and cell range expansion in heterogeneous networks for LTE-Advanced downlink

Abstract: In Long-Term Evolution (LTE)-Advanced, heterogeneous networks where femtocells and picocells are overlaid onto macrocells are extensively discussed in addition to traditional well-planned macrocell deployment to improve further the system throughput. In heterogeneous network deployment, combined usage of inter-cell interference coordination (ICIC) and cell range expansion (CRE) is very effective in improving the system and cell-edge throughput. In this combined usage, the fraction of the sets of user equipment (UEs) connected to the picocells, which are controlled through CRE, and that connected to macrocells affect the gain from the ICIC. Therefore, this paper evaluates the performance of ICIC and CRE in picocell deployments in the LTE-Advanced downlink. Simulation results (4 picocells and 30 UEs are located within 1 macrocell) assuming a full buffer model show that when the CRE offset value is set between 8 to 20 dB, almost the same user throughput performance is obtained by allocating the appropriate resources to protect UEs that connect to the picocells.

Radio propagation modeling for 5G mobile and wireless communications

Abstract: This article first identifies requirements of 5G radio propagation models for relevant propagation scenarios and link types derived from the analysis of recently discussed 5G visions and respective 5G technology trends. A literature survey reveals that none of the state-of-the-art propagation models such as WINNER/IMT-Advanced, COST 2100, and IEEE 802.11 fully satisfies the model requirements without significant extensions, and therefore there is room for a new framework of propagation models. We then present a novel map-based propagation model that satisfies the model requirements, and also introduce new extensions to existing stochastic models. Several open issues are finally identified that require further studies in 5G propagation modeling.