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.

Efficient constructions of variable-input-length block ciphers

Abstract: Existing block ciphers operate on a fixed-input-length (FIL) block size (e.g., 64-bits for DES). Often, one needs a variable-input-length (VIL) primitive that can operate on a different size input; it is, however, undesirable to construct this primitive from “scratch.” This paper contains two constructions that start with a fixed-input-length block cipher and show how to securely convert it to a variable-input-length block cipher without making any additional cryptographic assumptions. Both constructions model the FIL block cipher as a pseudorandom permutation (PRP) – that is, indistinguishable from a random permutation against adaptive chosen plaintext attack. The first construction converts it to a VIL PRP and is an efficiency improvement over the scheme of Bellare and Rogaway [4]. The second construction converts it to a VIL super pseudorandom permutation (SPRP) – that is, the resulting VIL block cipher is indistinguishable from a random permutation against adaptive chosen plaintext and ciphertext attack.

Capacity analysis of LTE-Advanced HetNets with reduced power subframes and range expansion

Abstract: The use of reduced power subframes in LTE Rel. 11 can improve the capacity of heterogeneous networks (HetNets) while also providing interference coordination to the picocell-edge users. However, in order to obtain maximum benefits from the reduced power subframes, setting the key system parameters, such as the amount of power reduction, carries critical importance. Using stochastic geometry, this paper lays down a theoretical foundation for the performance evaluation of HetNets with reduced power subframes and range expansion bias. The analytic expressions for average capacity and 5th percentile throughput are derived as a function of transmit powers, node densities, and interference coordination parameters in a two-tier HetNet scenario and are validated through Monte Carlo simulations. Joint optimization of range expansion bias, power reduction factor, scheduling thresholds, and duty cycle of reduced power subframes is performed to study the trade-offs between aggregate capacity of a cell and fairness among the users. To validate our analysis, we also compare the stochastic geometry-based theoretical results with the real macro base station (MBS) deployment (in the city of London) and the hexagonal grid model. Our analysis shows that with optimum parameter settings, the LTE Rel. 11 with reduced power subframes can provide substantially better performance than the LTE Rel. 10 with almost blank subframes, in terms of both aggregate capacity and fairness.

Adaptive terminal middleware for session mobility

Abstract: The Various network resources, including wireless access and multimedia devices, expected in ubiquitous computing environments, have limited geographical service areas and different attributes. This paper proposes adaptive terminal middleware that performs policy-based dynamic resource selection and host-based session management to hide session failures and resource changes from applications and a user. The middleware realizes a Virtual Socket, on top of real sockets, which employs a seamless session handoff mechanism for resource changes, and a resume and retransmission mechanism against disconnection of the wireless link. We implemented the middleware and a test application on top of it to evaluate the performance.

Location registration area configuring method, mobile communication system, base station, and location management server

Abstract: An object of the invention is to make improvement in the configuration of location registration areas. When a base station 13P is newly installed in a location registration area 30A, the base station 13P recognizes a location of its own with GPS or the like and performs communication with a plurality of surrounding base stations 13Q to select a location registration area 30A to which it should belong, based on the belonging status of the surrounding base stations 13Q and the location of its own. If the base station 13P is located near a boundary between location registration areas and if the surrounding base stations 13Q belong to a plurality of location registration areas, the location registration area to which the base station 13P should belong may be selected so as to average traffics in the respective location registration areas, or the location registration area with the smallest number of base stations belonging thereto may be selected so as to average the numbers of base stations in the respective location registration areas. The base station 13P broadcasts an area identifier of its belonging location registration area 30A to mobile stations under control thereof and starts provision of service thereto.

Mechanisms of ovarian cancer metastasis: biochemical pathways.

Abstract: Ovarian cancer is the most lethal gynecologic malignancy. Despite advances in chemotherapy, the five-year survival rate of advanced ovarian cancer patients with peritoneal metastasis remains around 30%. The most significant prognostic factor is stage, and most patients present at an advanced stage with peritoneal dissemination. There is often no clearly identifiable precursor lesion; therefore, the events leading to metastatic disease are poorly understood. This article reviews metastatic suppressor genes, the epithelial-mesenchymal transition (EMT), and the tumor microenvironment as they relate to ovarian cancer metastasis. Additionally, novel chemotherapeutic agents targeting the metastasis-related biochemical pathways are discussed.