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.

Menu element selecting device and method

Abstract: A desired function is started promptly by selecting it from a function menu of an electronic device having a plurality of functions. An annular menu is displayed on a main LCD (21). Function electments are shifted one by one by operating a cross key of a main control section (25) horizontally, and so the active element is changed to the one opposed to the active element by operating the cross key vertically.

Theoretical analysis of handover failure and ping-pong rates for heterogeneous networks

Abstract: In this paper, we characterize the relation between handover failure and ping-pong rates in a 3GPP heterogeneous network scenario as a function of relevant system parameters such as time-to-trigger, user equipment velocity, range expansion bias, etc. Under the assumptions that the picocell coverage and radio link failure areas are circular regions, and that users follow linear trajectories, handover failure and ping-pong rates are derived in closed-form expressions. Simulation results verify the accuracy of our analytical derivations, which shed new light on key aspects of the handover process in a heterogeneous network.

Secure authentication system for public WLAN roaming

Abstract: A serious challenge for seamless roaming between independent wireless LANs (WLANs) is how best to confederate the various WLAN service providers, each having different trust relationships with individuals and each supporting their own authentication schemes, which may vary from one provider to the next. We have designed and implemented a comprehensive single sign-on (SSO) authentication architecture that confederates WLAN service providers through trusted identity providers. Users select the appropriate SSO authentication scheme from the authentication capabilities announced by the WLAN service provider, and can block the exposure of their privacy information while roaming. In addition, we have developed a compound Layer 2 and Web authentication scheme that ensures cryptographically protected access while preserving pre-existing public WLAN payment models. Our experimental results, obtained from our prototype system, show that the total authentication delay is about 2 seconds in the worst case. This time is dominated primarily by our use of industry-standard XML-based protocols, yet is still small enough for practical use.

Time-Varying Path-Shadowing Model for Indoor Populated Environments

Abstract: This paper presents a path-shadowing model for indoor populated environments that has been developed based on computer simulations. The propagation paths between the transmitting and receiving points in an empty rectangular space are determined using the ray-tracing method, in which moving quasi-human bodies that are modeled as cylinders with a finite height are generated in the space, and intersections of the paths with the bodies are counted. From the results, the shadowing probabilities, durations, and intervals are evaluated for each propagation path, and this shadowing process is characterized as a Markov process. This paper proposes a method that individually generates the shadowing effects on each propagation path. The measurement results of the path-shadowing characteristics using a 5.2-GHz high-resolution channel sounder are presented, and the validity of this model is confirmed. Similar measurement results using a photoelectric sensor are also presented to reinforce the channel-sounding measurement results.