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.

Certificate-Based Encryption and the Certificate Revocation Problem.

Abstract: We introduce the notion of certificate-based encryption. In this model, a certificate – or, more generally, a signature – acts not only as a certificate but also as a decryption key. To decrypt a message, a keyholder needs both its secret key and an up-to-date certificate from its CA (or a signature from an authorizer). Certificate-based encryption combines the best aspects of identity-based encryption (implicit certification) and public key encryption (no escrow). We demonstrate how certificate-based encryption can be used to construct an efficient PKI requiring less infrastructure than previous proposals, including Micali’s Novomodo, Naor-Nissim and Aiello-Lodha-Ostrovsky. Comment: This is a version of the Eurocrypt 2003 paper, identical except for this comment and a correction in Section 3.2. I’m posting it online to make it more widely available, particularly since a couple of recent works propose essentially the same idea.

Analysis of wireless geolocation in a non-line-of-sight environment

Abstract: We present an analysis of the time-of-arrival (TOA), time-difference-of-arrival (TDOA), angle-of-arrival (AOA) and signal strength (SS) based positioning methods in a non-line-of-sight (NLOS) environment. Single path (line-of-sight (LOS) or NLOS) propagation is assumed. The best geolocation accuracy is evaluated in terms of the Cramer-Rao lower bound (CRLB) or the generalized CRLB (G-CRLB), depending on whether prior statistics of NLOS induced errors are unavailable or available. We then show that the maximum likelihood estimator (MLE) using only LOS estimates and the maximum a posteriori probability (MAP) estimator using both LOS and NLOS data can asymptotically achieve the CRLB and the G-CRLB, respectively. Hybrid schemes that adopt more than one type of position-pertaining data and the relationship among the four methods in terms of their positioning accuracy are also investigated.

Network coding for efficient communication in extreme networks

Abstract: Some forms of ad-hoc networks need to operate in extremely performance-challenged environments where end-to-end connectivity is rare. Such environments can be found for example in very sparse mobile networks where nodes "meet" only occasionally and are able to exchange information, or in wireless sensor networks where nodes sleep most of the time to conserve energy. Forwarding mechanisms in such networks usually resort to some form of intelligent flooding, as for example in probabilistic routing.We propose a communication algorithm that significantly reduces the overhead of probabilistic routing algorithms, making it a suitable building block for a delay-tolerant network architecture. Our forwarding scheme is based on network coding. Nodes do not simply forward packets they overhear but may send out information that is coded over the contents of several packets they received. We show by simulation that this algorithm achieves the reliability and robustness of flooding at a small fraction of the overhead.

Portable base station device

Abstract: This invention provides a mobile base station device which allows tamper resistance to be adequately secured even when the housing is opened illicitly. In a mobile base station device 1, when a housing 2 is opened illicitly, a user ID or similar is transmitted to a service management server 20, and the user attempting an illicit operation is identified. By registering the identified user on a blacklist, subsequent use of the mobile base station device 1 by this user can be prohibited. Also, in the mobile base station device 1, together with transmission of the user ID, a communication control program 7 is deleted from a communication control module 6, so that the interior of the housing 2 is rendered a “black box”, and modification and illicit use of the communication control program can be deterred. As a result, even when the housing 2 of the mobile base station device 1 is opened illicitly, tamper resistance can be adequately secured.

A novel architecture for LTE-B :C-plane/U-plane split and Phantom Cell concept

Abstract: This paper introduces a novel approach in increasing the capacity of LTE cellular networks. The solution is based on massive deployment of small cells by leveraging high frequency reuse at high frequency bands in conjunction with a Macrocell. The presence, discovery and usage of the small cells are controlled dynamically by a Macrocell in a master-slave configuration hence they are called Phantom Cells. To realize this concept, a new method of managing the connections between mobile terminals and small cell nodes is introduced. It is achieved by splitting the Control and User (C/U) planes of the radio link. The combination of C/U-plane split and Phantom Cells can achieve high capacity enhancement using small cells at the same time taking into consideration mobility, scalability and flexibility requirements for massive deployment. The advantages of this approach as well as the implementation aspects are described in the paper. Simulations were also conducted to verify the concept and the results show some promising capacity enhancements. The rest of the paper describes the Phantom Cell concept as well as the challenges of deploying small cells in LTE networks.