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.

Sparse orthonormal transforms for image compression

Abstract: We propose a block-based transform optimization and associated image compression technique that exploits regularity along directional image singularities. Unlike established work, directionality comes about as a byproduct of the proposed optimization rather than a built in constraint. Our work classifies image blocks and uses transforms that are optimal for each class, thereby decomposing image information into classification and transform coefficient information. The transforms are optimized using a set of training images. Our algebraic framework allows straightforward extension to non-block transforms, allowing us to also design sparse lapped transforms that exploit geometric regularity. We use an EZW/SPIHT like entropy coder to encode the transform coefficients to show that our block and lapped designs have competitive rate-distortion performance. Our work can be seen as nonlinear approximation optimized transform coding of images subject to structural constraints on transform basis functions.

How does randomized beamforming improve the connectivity of ad hoc networks

Abstract: This paper analyzes the impact of beamforming antennas on the topological connectivity of multihop wireless networks. As a metric for the connectivity of the network, we use the percentage P(path) of nodes that are connected via a multihop path. We show that simple randomized beamforming - i.e., each node adjusts its main beam into a randomly chosen direction for transmission and reception - significantly improves P(path) compared to networks with omnidirectional antennas employing the same power and sensitivity. The study is performed using accurate, analytical antenna models for uniform linear and circular antenna arrays. Already small arrays with four antenna elements give high gains of P(path). These gains are achieved although the nodes' average number of neighbors does not necessarily increase.

Quality-of-experience driven adaptive HTTP media delivery

Abstract: This paper presents a Quality of Experience (QoE) driven approach for multi-user resource optimization in Dynamic Adaptive Streaming over HTTP (DASH) over next generation wireless networks. Our objective is to enhance the user experience in adaptive HTTP streaming by jointly considering the characteristics of the media content and the available wireless resources in the operator network. Specifically, we propose a proactive QoE-based approach for rewriting the client HTTP requests at a proxy in the mobile network. The advantage of the proposed approach is its applicability for over-the-top (OTT) streaming as it requires no adaptation of the media content. We compare our proposed scheme to both reactive QoE-optimized and to standard-DASH HTTP streaming. Our contributions are: 1) We first show that standard OTT DASH leads to unsatisfactory performance since the content agnostic resource allocation by the LTE scheduler is far from optimal, and we can achieve a clear QoE improvement when considering the content characteristics. 2) We additionally show that proactively rewriting the client requests gives control of the video content adaptation to the network operator which has better information than the client on the load and radio conditions in the cell. This results in additional gains in user perceived video quality. 3) A standard unmodified DASH client remains unaware of the proposed rewriting of the HTTP requests and can decode and play the redirected media segments.

Distributions of Transmit Power and SINR in Device-to-Device Networks

Abstract: We study the spatial distribution of transmit powers and signal to interference plus noise ratio (SINR) in device-to-device (D2D) networks. Using homogeneous Poisson Point Processes (PPP), cumulative distribution function (CDF) of the transmit power and SINR are analytically derived for a D2D network employing power control. Then, computer simulations are performed for the same network architecture and it is shown that device location modeling and analytical methods from stochastic geometry can enable us to obtain transmit power and SINR distributions of a D2D network.

Experimental mm wave 5G cellular system

Abstract: Bolstered by the ever increasing processing power of smart devices and combined with the new innovative applications, cellular data traffic demand is expected to increase a 10000x by 2025. Simultaneously, the telecommunication industry is converging on a common set of 5G requirements specifying 10x peak rates, 10x reductions in latency and 100x increases in cell edge rates over 4G cellular. Researchers are now looking to higher frequencies to meet demand and achieve the new requirements. This paper describes an experimental 5G system designed to operate at 73.5 GHz with a 1 GHz BW. The system communicates using a 28 dB gain antenna having a narrow 3 degree half-power beamwidth serving fully mobile user devices moving at pedestrian speeds. This experimental system is implemented in collaboration with Nokia and NTT DOCOMO [1][2].