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.

Barrier coverage with line-based deployed mobile sensors

Abstract: Barrier coverage of a wireless sensor network is a critical issue in military and homeland security applications, aiming to detect intruders that attempt to cross the deployed region. While a range of problems related to barrier coverage have been investigated, little effort has been made to explore the effects of different sensor deployment strategies and mechanisms to improve barrier coverage of a wireless sensor network after it is deployed. In this paper we study the barrier coverage of a line-based sensor deployment strategy and explore how to exploit sensor mobility to improve barrier coverage. We first establish a tight lower bound for the existence of barrier coverage under the line-based deployment. Our results show that the barrier coverage of the line-based deployment significantly outperforms that of the Poisson model when the random offsets are relatively small compared to the sensor's sensing range. To take advantage of the performance of line-based deployment, we further devise an efficient algorithm to relocate mobile sensors based on the deployed line so as to improve barrier coverage. The algorithm finds barrier gaps and then relocates mobile sensors to fill the gaps while at the same time balancing the energy consumption among mobile sensors. Simulation results show that the algorithms can effectively improve the barrier coverage of a wireless sensor network for a wide range of deployment parameters. Therefore, in wireless sensor network applications, the coverage goal, possible sensor deployment strategies, and sensor mobility must be carefully and jointly considered. The results obtained in this paper will provide important guidelines and insights into the deployment and performance of wireless sensor networks for barrier coverage.

Frequency selection apparatus, a mobile communications system, and a multi-band frequency resource management method

Abstract: A frequency selection apparatus, a mobile communications system, and a multi-band resource management method are disclosed. The frequency selection apparatus includes an acquisition unit configured to collect environmental information about a mobile station for each frequency band according to system frequency bands that a mobile station can use, and a frequency selection unit configured to determine the frequency band to be used and the system to be connected to, based on the environmental information and information provided by the mobile station.

Secure intra- and inter-domain handover

Abstract: To achieve a secure and fast handover in a distributed mobile communication environment (10), the control functionality is lying at the borderline between wireless and wire-bound communication network elements, and it is proposed to, firstly, execute a mutual authentication between a mobile device (26) and a new access point (14) using security context information previously transmitted to the new access point. Then, after successful mutual authentication, a handover will be executed from the current access point (12) to the new access point (14).

Wireless positioning approach using time delay estimates of multipath components

Abstract: A wireless positioning apparatus includes a multipath delay estimator configured to estimate multipath delay components from one or more received signals; a selector configured to select appropriate delay estimates from the estimated multipath delay components according to a predetermined criterion; a storage configured to store an NLOS delay function defining prior statistics of information about non-line-of-sight delays; and a position estimator configured to estimate a position of a mobile station based on the selected delay estimates and the NLOS delay function read out from the storage.

Mobile terminal having international dial operation function and international dial system

Abstract: A mobile terminal having an international dial operation function for performing with a simple operation, conversion to an international telephone number, which has been complicated, and conversion to an appropriate telephone number according to the position of the mobile terminal. The position of a user mobile terminal is identified by a position identification unit and according to the identified position, it is decided whether the destination is in a country of a caller or outside the country. When the destination is outside the country of the caller, an international prefix is identified in accordance with the identified position. Furthermore, the country number is set to a number corresponding to the caller’s country or identified from the destination telephone number which has been input. These are used for conversion to an international telephone number and calling. When the destination is in the caller’s country, the domestic telephone number is directly used for calling. The number after the conversion is displayed on the operation screen and can be checked by the caller.