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.

Wireless communication device, a wireless communication system and a wireless communication method

Abstract: A wireless communication device, a wireless communication system and a wireless communication method for preventing buffer over flow in the wireless communication device acting as a relay node, and for improving throughput within the whole system are disclosed. The wireless communication device includes an information acquisition unit configured to acquire information on the amount of data relay processing in the wireless communication device and/or a neighbor wireless communication device; a priority calculation unit configured to calculate transmission priority of the wireless communication device, based on the acquired information; and a priority determination unit configured to determine a priority related parameter for data transmission from the wireless communication device, based on the transmission priority.

Wireless communication system

Abstract: The present invention provides a wireless communication system that comprises a plurality of communication networks operating with different communication parameters and protocols and at least one communication terminal having multiple communication modules each adapted to operate with specific communication parameters and protocol for access to at least one corresponding communication network operating with the same communication parameters and protocol. A module in the communication terminal is activated to prepare for communication with the corresponding network when it is expected likely that the communication terminal is heading to access the corresponding network. The activated module is deactivated when the same is expected unlikely. The communication terminal is usually battery-powered. Since modules are deactivated when not necessary, the battery life can be prolonged.

On time-of-arrival positioning in a multipath environment

Abstract: Wireless geolocation in a multipath environment is of particular interest for wideband communications. The conventional approach makes use of first-arriving signals only. In this paper, we investigate whether and under what conditions processing multipath delays should enhance the positioning accuracy. The best achievable positioning accuracy is evaluated in terms of the Cramer-Rao low bound (CRLB) and the generalized-CRLB (G-CRLB), depending on whether prior statistics of non-line-sight (NLOS) induced errors are available. We then show that such prior statics are critical to the accuracy improvement when the multipath delays are processed. Furthermore, the degree of accuracy enhancement depends on two major factors: the strength of multipath components and the variance of NLOS induced errors. The corresponding positioning receivers are also discussed. In previous work (Y. Qi and H. Kobayashi, Proc. 2002 IEEE Int. Conf. on Acoustic Speech and Sig. Proc., pp. 2473-2476, 2002, and Proc. IEEE Vehicle Tech. Conf., pp. 285-288, 2002), we developed an analysis of the time-of-arrival (TOA) positioning method in an NLOS environment, assuming single path propagation. The main results obtained there are extended and applied to the multipath case in this paper.

Data packet communications taking into account channel quality and buffered data amount

Abstract: Base station (100) includes a channel quality detecting unit (120) that detects channel quality between the base station and a mobile station (200), a buffered data amount monitoring unit (130), and a modulation and coding set determination unit (150). The modulation and coding set determination unit determines a modulation and coding set, as a downlink modulation scheme for packet communications, such that a prescribed communication condition corresponding to the channel quality is satisfied, and that padding added to the data buffered in a transmission buffer (140) for subsequent transmission to the mobile station becomes the minimum.

A relaying scheme using QR decomposition with phase control for MIMO wireless networks

Abstract: Multiple-input multiple-output (MIMO) wireless networks are wireless communication systems composed of multiple nodes, each of which is equipped with multiple antennas. As proven by earlier studies, point-to-point MIMO systems offer significant capacity through spatial multiplexing and diversity techniques. Furthermore, recent studies have shown that the capacity of MIMO wireless networks can be greatly improved by using multiple relay nodes to relay messages simultaneously from source to destination. This paper proposes a relaying scheme for MIMO wireless networks. Its major concepts are: 1) performing QR decomposition on backward and forward channels in conjunction with phase control at each relay node, and 2) conducting successive interference cancellation (SIC) at the destination node. Such operations enable the wireless network to obtain distributed array gain among multiple relay nodes and receive array gain while maintaining maximum spatial multiplexing gain. Numerical examples have shown that the proposed relaying scheme is superior to previously proposed ones in both ergodic and outage capacity perspective.