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.

On Constellation Rotation of NOMA With SIC Receiver

Abstract: In this letter, we exploit constellation rotation to enhance the performance of uplink non-orthogonal multiple access (NOMA) with a successive interference cancellation receiver. We characterize the received signal with a Gaussian mixture model (GMM), where optimal rotation angle is obtained by maximizing the entropy of GMM. Then, we efficiently solve the entropy maximization problem by deriving an optimal closed-form approximate problem via variational approximation. Performance analysis and simulation results show that the proposed scheme achieves larger capacity and lower bit error rate compared with conventional NOMA. The performance gain is more significant with fewer receiving antennas or with smaller channel gain difference between multiplexed users.

CDMA and IDMA: Iterative Multiuser Detections for Near-Far Asynchronous Communications

Abstract: This paper provides comprehensive comparison of the iterative multiuser detection techniques for code division multiple access (CDMA) and interleave division multiple access (IDMA). We investigate the performance in various scenarios such as user-asynchronism, multipath channels, near-far problem, and overloaded scenarios. We develop our system model which is general enough to take into account the above mentioned scenarios as well as being capable of incorporating aspects relevant to these access schemes. We provide formal descriptions of both schemes using our system model that illuminates the similarities and differences of the two different schemes. Computer simulations are performed in a variety of scenarios. It is observed that IDMA performs better than or as good as CDMA despite its simplicity

Situational reasoning for task-oriented mobile service recommendation

Abstract: We study the case of integrating situational reasoning into a mobile service recommendation system. Since mobile Internet services are rapidly proliferating, finding and using appropriate services require profound service descriptions. As a consequence, for average mobile users it is nowadays virtually impossible to find the most appropriate service among the many offered. To overcome these difficulties, task navigation systems have been proposed to guide users towards best-fitting services. Our goal is to improve the user experience of such task navigation systems making them context-aware (i.e. to optimize service navigation by taking the user's situation into account). We propose the integration of a situational reasoning engine that applies classification-based inference to qualitative context elements, gathered from multiple sources and represented using ontologies. The extended task navigator enables the delivery of situation-aware recommendations in a proactive way. Initial experiments with the extended system indicate a considerable improvement of the navigator's usability.

Scalable routing easy as PIE: A practical isometric embedding protocol

Abstract: We present PIE, a scalable routing scheme that achieves 100% packet delivery and low path stretch. It is easy to implement in a distributed fashion and works well when costs are associated to links. Scalability is achieved by using virtual coordinates in a space of concise dimensionality, which enables greedy routing based only on local knowledge. PIE is a general routing scheme, meaning that it works on any graph. We focus however on the Internet, where routing scalability is an urgent concern. We show analytically and by using simulation that the scheme scales extremely well on Internet-like graphs. In addition, its geometric nature allows it to react efficiently to topological changes or failures by finding new paths in the network at no cost, yielding better delivery ratios than standard algorithms. The proposed routing scheme needs an amount of memory polylogarithmic in the size of the network and requires only local communication between the nodes. Although each node constructs its coordinates and routes packets locally, the path stretch remains extremely low, even lower than for centralized or less scalable state-of-the-art algorithms: PIE always finds short paths and often enough finds the shortest paths.

Indoor/outdoor decision apparatus and indoor/outdoor decision method

Abstract: An appropriate indoor/outdoor decision is made for a mobile communication terminal in accordance with a purpose of selection of a positioning method or the like A positioning server 10 is an indoor/outdoor decision apparatus for making an indoor/outdoor decision on whether a mobile communication terminal 20 is located indoors or outdoors, which has: a communication information acquiring unit 11 which acquires communication information about wireless communication at the mobile communication terminal 20; an environment information acquiring unit 12 which acquires environment information indicative of an environment associated with the mobile communication terminal 20; a criterion setting unit 13 which sets a criterion for the indoor/outdoor decision according to the environment information; and a deciding unit 14 which makes the indoor/outdoor decision with reference to the communication information on the basis of the set criterion