Showing papers by "Hiroshi Harada published in 2007"

Bullet-train Network Architecture for Broadband and Real-time Access

Abstract: New services on trains are attracting a great deal of attention throughout Europe and Asia where trains are one of the most important forms of transportation. We introduced two information services on bullet-trains; Internet access and video. There are three technical challenges posed by seamless handover at 300 km/h, aggregation of multiple access, and attack-tolerant communications. We proposed a network architecture to solve them based on the requirements of these services. Due to its extendibility and flexibility, new services that will be introduced in the future can be integrated easily. We are currently developing a testbed for experimental evaluations.

0.4-5.2GHz SiGe-MMIC Direct Conversion Mixer for Cognitive Radio Receiver

Abstract: 0.4-5.2 GHz broad-band SiGe-MMIC direct conversion quadrature mixer (Q-MDC) has been developed for multi-band multi-mode cognitive radio receivers by using 0.35 mum SiGe BiCMOS process. To realize broad-band characteristic, a static frequency divider with two-stage emitter follower is used as 90 degree power divider for LO and broad-band doubly balanced mixers are used as I/Q unit mixers. The 90 degree power divider enable to achieve multi-octave operation for LO which covers whole band of 0.4-5.2 GHz. Broad-band unit mixers also enable to achieves wide RF band (0.4-5.2 GHz) and wide base band (up to 500 MHz). The fabricated Q-MIX performs EVM of less than 3% over the whole RF frequency range of 0.4 -5.2 GHz and shows the dynamic range of more than 40 dB for 0.4 GHz UHF application (16 QAM/OFDM), 0.8 GHz/2 GHz W-CDMA (QPSK) and 5.2 GHz IEEE 802.11a W-LAN (64 QAM/OFDM) receptions

Communication control apparatus, communication terminal apparatus, wireless communication system, and communication method

Abstract: The amount of information reported by a communication terminal apparatus to a communication control apparatus is reduced based on the congestion status of communication. Communication control 100 apparatus communicates with a communication terminal apparatus using frequency channels composed of two or more sub-channels defined by a predetermined frequency band includes: receiver 113 for receiving information data destined to the terminal apparatus; scheduler 113 for generating assignment information indicating the status of assignment of the received information data to each sub-channel; congestion information generator 103 for generating congestion information indicating the congestion degree of each sub-channel based on the generated assignment information; control information generator 104 for generating control information including the generated congestion information; and transmitter 111 for transmitting the generated control information to the terminal apparatus.

A Highly Mobile SDM-OFDM System Using Reduced-Complexity-and-Latency Processing

Abstract: We propose a new space division multiplexing-orthogonal frequency division multiplexing system using reduced-complexity-and-latency detection and channel estimation algorithms. It is important to reduce a latency from receiver processing because the latency degrades performances of wireless systems in a mobile fading environment. In this paper, we evaluate and discuss bit error rate performance and computational complexity of the proposed system. From simulation results, we observe that our proposed estimation scheme improves the accuracy more than conventional minimum mean square error based schemes, and that the proposed system outperforms a maximum likelihood detection based system in a mobile fading environment. Moreover, we confirm that the proposed system is superior to the conventional schemes from the points of not only the performance but also the complexity.

Communication control device, communication terminal device, radio communication system, and communication method

Abstract: The amount of information reported by a communication terminal apparatus to a communication control apparatus is reduced based on the congestion status of communication Communication control 100 apparatus communicates with a communication terminal apparatus using frequency channels composed of two or more sub-channels defined by a predetermined frequency band includes: receiver 113 for receiving information data destined to the terminal apparatus; scheduler 113 for generating assignment information indicating the status of assignment of the received information data to each sub-channel; congestion information generator 103 for generating congestion information indicating the congestion degree of each sub-channel based on the generated assignment information; control information generator 104 for generating control information including the generated congestion information; and transmitter 111 for transmitting the generated control information to the terminal apparatus

A Carrier Interferometry Based Channel Estimation Technique for MIMO-OFDM/TDMA Systems

Abstract: SUMMARY This paper proposes a channel estimation technique for the dynamic parameter controlled — orthogonal frequency and time division multiple access (DPC-OF/TDMA) systems studied as one of the candidates of the beyond third generation (B3G) systems. In the proposed scheme, the impulse response, which represents the channel state information (CSI) is estimated using carrier interferometry (CI) which is equivalent to impulse signal transmission. Moreover, because the minimum number of subcarriers allocated to terminals is 64, in order to estimate a CSI with its spreading factor of 64, we employ a code-multiplexed CI signal for a cell search process and a time-domain-multiplexed CI signal for transmit antenna identification. Furthermore, we also propose a flexible CSI estimation scheme that supports two cases: multiple subchannel block assignment and MIMO transmission cases. Computer simulation confirms that the pro

A Study of Radio-information Services for Networks of Cognitive Radios

Abstract: The next generation of wireless networks, as envisioned by recent advances in cognitive radio (CR) technologies, will be autonomic and able to adjust their configurations to changes in the communications environment. There are three types of CRs, such as IEEE 802.22 radio, multiple-radio with CR functions, and so- called fully configurable radios. Reconfigurable networks use these CRs and spectra efficiently. This paper discusses various cognitive radios from the viewpoint of re-configurable radio-information management for CR networks. We then propose a flexible and scalable network architecture for CR networks that enables management of re-configurable radio information. We classify radio information and propose the summarization of re-configuration information to enable efficient data exchanges between mobile terminals and the network. We intend to evaluate the efficiency of information services in the near future focusing on network traffic on wireless links.

Network and access technologies for new generation mobile communications—overview of National R&D Project in NICT

Abstract: Summary R&D on new generation mobile network has attracted a growing interest over the world on the background of rapid market growth for 2nd and 3rd generation cellular networks and wireless LANs/MANs. The National Institute of Information and Communications Technology (NICT) started the New Generation Mobile Network Project in April 2002, and has developed fundamental technologies to enable seamless and secure integration of various wireless access networks such as existing cellular networks, wireless LANs, home networks, intelligent transport systems (ITS), the Beyond-3G (B3G) cellular and other wireless access systems. This paper overviews the achievements of the project focusing on network and access technologies. Copyright © 2007 John Wiley & Sons, Ltd.

Radio-wave transparent surface containing lines loaded with impedance at regular intervals

Abstract: The vector effective length of a half wavelength-dipole becomes almost zero when a reactance of about 500 ohm is loaded to its center. Since the current integral is almost zero when the vector effective length is zero, the electric influence on other antennas and to the radiation field is smaller than an open-circuited dipole. On the other hand, although other antennas affect the amplitude of the current distribution, the shape of the distribution does not change. Therefore, the vector effective length should be kept to zero. Accordingly, not only the influence on other antennas but also the influence by other antennas can be neglected. Dipoles are, therefore, thought to be almost electrically invisible. Lines composed with electrically invisible dipoles joined in series with a connector of open stubs are also thought to be electrically invisible. A surface containing such lines arranged in parallel is thought to be electrically transparent for radio waves at the same frequency at which the dipoles become electrically invisible. In this paper, we examine analytically the transparency of such surfaces.

Reduced-Complexity Detection for DPC-OF/TDMA System Enhanced by Multi-Layer MIMO-OFDM in Wireless Multimedia Communications

Abstract: During these years, we have been focusing on developing ultra high-data-rate wireless access systems for future wireless multimedia communications. One of such kind of systems is called DPC-OF/TDMA (dynamic parameter controlled orthogonal frequency and time division multiple access) which targets at beyond 100 Mbps data rate. In order to support higher data rates, e.g., several hundreds of Mbps or even Gbps for future wireless multimedia applications (e.g., streaming video and file transfer), it is necessary to enhance DPC-OF/TDMA system based on MIMO-OFDM (multiple-input multiple-output orthogonal frequency division multiplexing) platform. In this paper, we propose an enhanced DPC-OF/TDMA system based on Multi-Layer MIMO-OFDM scheme which combines both diversity and multiplexing in order to exploit potentials of both techniques. The performance investigation shows the proposed scheme has better performance than its counterpart based on full-multiplexing MIMO-OFDM scheme. In addition to the Exhaustive Detection (EXD) scheme which applies the same detection algorithm on each subcarrier independently, we propose the Reduced-Complexity Detection (RCD) scheme. The complexity reduction is achieved by exploiting the suboptimal Layer Detection Order and subcarrier correlation. The simulation results show that huge complexity can be reduced with very small performance loss, by using the proposed detection scheme. For example, 60.7% complexity can be cut off with only 1.1 dB performance loss for the 8 × 8 enhanced DPC-OF/TDMA system.

Device and method for decoding signal, program, and information recording medium

Abstract: PROBLEM TO BE SOLVED: To provide high-speed and large-capacity communication and to perform high-precision decoding SOLUTION: An initial channel estimation section 31 estimates an initial channel by using a pilot symbol added to the head of each packet After the replica of a transmission symbol is generated, CCI components of every L transmitting antennas are generated as to a received signal vector and removed from the received signal vector by a CCI canceler 33 After a received symbol vector after CCI component removal is obtained, a divider 34 acquires an instantaneous estimated value An update condition decision section 35 detects deterioration in channel response amplitude based upon a threshold An instantaneous estimated value decided to be deficient in SNR is discarded A channel response estimation matrix at time t+1 is output from an averaging circuit 36 through averaging processing and supplied to a symbol decoding section 13 COPYRIGHT: (C)2007,JPO&INPIT