Hitachi, Ltd.

Renesas Technology Corp.

Hitachi Metals, Ltd.

Hitachi Engineering Co., Ltd.

Hitachi Computer Engineering Co., Ltd.

Masaaki Shida

Takashi Yano

Tomoaki Ishifuji

Shigenori Hayase

Keisuke Yamamoto

Nobukazu Doi

Takeshi Saitoh

Atsushi Ogino

Ryota Yamasaki

Katsuhiko Tsunehara

Tatemi Ido

Tsuyoshi Tamaki

Hideya Suzuki

Hidehiko Jusa

Takao Kobayashi

Kazuhiko Kawai

Kazuko Hamaguchi

Toshikazu Nishino

Yunjian Jia

Masato Hirai

Shinji Murai

Kenichiro Orita

Takaharu Aoyama

A radio communication system for a communication between a base station and a mobile terminal. The radio communication system repeats a signal transmitted from the base station at repeaters that are multistage-connected by a leaky coaxial cable. Each repeater converts a frequency of an input signal into a different frequency and outputs the frequency-converted signal to the leaky coaxial cable connected to the repeater. The repeaters are provided between the leaky coaxial cables connected in series.

Radio communication system and a repeater

A distributed antenna system includes a first antenna disposed covering a predetermined communication range, the first antenna carrying out a communication at least at a low-frequency band, and a plurality of second antennas disposed covering the predetermined communication range, the plurality of second antennas carrying out a communication at a high-frequency band. The distributed antenna system is operable to carry out a communication between the first antenna and the second antennas, and a mobile terminal located within the predetermined communication range by means of carrier aggregation using the low-frequency band and the high-frequency band. The distributed antenna system further includes a BB module equipped in a base station for carrying out a communication within the predetermined communication range, the first antenna and the second antennas being each connected to the one BB module via an RF module.

Distributed antenna system

In a MIMO wireless communication system, the transformation process synthesizes the eigenmodes having a large singular value (i.e. a high effective SNR) and the eigenmodes having a small singular value (i.e. a low effective SNR). Thereby, the former eigenmodes are converted into modes having suppressed effective SNR which do not require a large number of levels of modulation, and the latter eigenmodes are converted into modes having increased effective SNR instead. In a MIMO wireless communication system for eigenmode transmission, a large communication capacity is realized without increasing the number of levels of modulation even in a communication environment capable of achieving a high SNR.

MIMO wireless data communication system, MIMO wireless data communication method and MIMO wireless data communication apparatus

In a system in which a host and a plurality of terminals simultaneously communicate with each other under the SDMA scheme, transmission parameters to be used for generating frames for SDMA transmission to the respective terminals are adjusted in consideration of the transmission time durations necessary for transmission of other frames to be transmitted simultaneously with the first-mentioned frames, so that differences between the frame transmission time durations are reduced.

Wireless communication method, wireless communication apparatus and access point apparatus

In a wireless communication system for communicating with a plurality of stations at the same point of time with the same frequency using a Space Division Multiple Access (SDMA), wireless resources are allocated by a first decision unit which evaluates performance of each station obtained when the SDMA is used and which determines periods of time to be allocated to groups of stations formed according to the SDMA technique. Using a first evaluation unit and a second evaluation unit to evaluate performance required by each station and each application, the first decision unit allocates the wireless resources to the stations. It is therefore possible that the wireless resources are efficiently allocated to the stations while preventing an event in which the wireless resources are excessive or insufficient for required quality of service.

Systems and methods for wireless communication using SDMA

In a wireless communication system in which a sending side derives transmit weight vectors based on feedback information and carries out precoding, performance degradation is caused when the channel at the time when the transmit weight vectors are derived and the true channel are different from each other. Along with variations in the channel, the power allocation to a plurality of effective streams formed in MIMO is caused to approach asymptotically to uniform power allocation from the value determined based on the channel state information that the sending side has.

Wireless communication system and wireless communication method

A method for suppressing the peak-to-average power ratio (PAPR) while limiting deterioration in signal characteristics in wireless communication devices utilizing wireless communication methods (OFDM method, MIMO method) for multiplexing and sending multiple signals. A weight calculator unit sets a large weight for transmit signals whose channel quality is poor, relative to the weight of each base component based on the acquired channel quality. A peak detector unit detects the peak from the signal string after unitary conversion, and extracts a distortion component to apply for suppressing the peak. A peak suppression signal generation unit calculates the peak signal from the distortion component and weight of each base component, to add to each base component, and adds the peak suppression signal to each base component prior to unitary transformation.

Apparatus and method for peak suppression in wireless communication systems

In a MIMO wireless transceiver, priority control that judges priority of transmit data and a transmission mode table are provided to control an option as to which transmission system SDM or STBC is selected, coding rate and modulation method based on a transmission mode for a transmission destination that is determined by priority of transmission data and status of a communication matrix at the time of data transmission. With such arrangement, a wireless communication system composed of the MIMO wireless transceiver can control coding, MIMO signal processing and modulation methods according to priority of transmit data. More specifically, it is possible to ensure transmission of data having higher priority and improve throughput in total when a plurality of types of data are transmitted.

Wireless transceiver

A MIMO wireless data transmission system including a data arrangement in which data to be sent is divided for each transmission stream of MIMO with adding an error detection code thereto and thereby resending a subframe's worth of data when an error occurred at the time of resending. It therefore becomes to avoid the same frame being sent again at the time of resending.

MIMO wireless data transmission system

Disclosed is a wireless communication system capable of performing demodulation at the receiving side without substantially deteriorating BER characteristics, regardless of carrier frequency error existing among plural wireless communication systems in SDMA of uplink. The wireless communication system includes plural antennas; a MIMO processor that decomposes a reception signal the plural antennas received from plural transmitters into transmission signals transmitted from the respective transmitters; a FFT processor that carries out OFDM demodulation; and a demapping unit that obtains data from signals which were previously converted into sub-carrier signals by the FFT processor, in which the MIMO processor is installed ahead of the FFT processor for sake of the processing sequence of a receive signal, and even though a carrier frequency offset exists in the reception signal MIMO processing is performed prior to OFDM demodulation to split the reception signal from plural transmitters.

Radio communication device

Wireless transceiver having plural transmission methods

A demodulating semiconductor integrated circuit device used in a wireless communication system of an FM-modulation scheme, wherein a circuit for canceling a frequency offset is made of a digital circuit, so as to make a high-accuracy decision as to received data and prevent error frequency offset cancel due to a pseudo pattern contained in the received data. Consequently, a high-accuracy received data decision is carried out.

Frequency offset cancellation circuit for data determination in wireless communications

A method, system, and apparatus are provided for detecting a position of a terminal in a network accurately without a GPS receiver. In one example, a method for locating a position of a terminal includes calculating a position of a base station; detecting a clock time difference between the base station and another base station; measuring a reception timing of a signal received by the base station from the terminal; and locating the position of the terminal using at least the position of the base station, the clock time difference, and the reception timing.

Growing community of inventors

Hachioji, Japan

Masaaki Shida