Ntt Docomo, Inc.

Shigeru Tomisato

Takahiro Asai

Hirohito Suda

Hiromasa Fujii

Takefumi Yamada

Tetsushi Abe

Tadashi Matsumoto

Yukihiko Okumura

Masato Maeda

Masaharu Hata

A receiver that receives a signal from a transmitter, including: a plurality of antennas; a channel estimation unit; a channel accumulation unit; a transmission weight generator; a feedback information transmission unit; and a reception weight generator. The plurality of antennas receive a second signal from the transmitter, the second signal being transmitted by using first feedback information. The channel estimation unit estimates a communication channel state on the basis of the second signal, and then outputs second channel estimation information. The reception weight generator generates reception weight information to be multiplied by the second signal, on the basis of first channel estimation information accumulated in the channel accumulation unit and a first transmission weight.

Multiple-output multiple-input (MIMO) communication system, MIMO receiver and MIMO receiving method

This invention provides an MIMO communication system and MIMO communication method. An MIMO receiver estimates state of each communication channel from the received signals received by #1 to #L antennas, generates feedback information according to the information of channel state, sends the feedback information to a transmitter through a feedback path, processes the feedback information in order to compensate feedback-delay of the feedback path, generate K*L proper reception weights by using the information of channel state and processed feedback information, multiplies the received #1 to #L substreams of respective #1 to #K signal streams by the proper #1 to #L reception weights, respectively, composes the #1 to #L weighted substreams to obtain respective composed #1 to #K signal streams and demodulate the composed #1 to #K signal streams, respectively, and combines the demodulated K signal streams to reproduce an original transmission signal.

Symbols converted by a serial-to-parallel converting part () from serial to parallel form are subjected to inverse Fourier transform processing in an inverse Fourier transform part () as sub-carrier signal components of a frequency interval equal to the symbol rate, then the levels of the resulting time domain signal components are compared with a permissible peak level Cin a peak component detecting part () to detect peak components, and the peak components are transformed by a Fourier transform part () to frequency domain components, which are subtracted by subtractors (to) from the corresponding sub-carrier signal components to thereby reduce the peak power.

Orthogonal frequency multi-carrier transmission device and transmission method

An object of the present invention is to provide a communications system etc., which can reduce the influence of interference from other systems which results from a difference in symbol length, in an area where a plurality of systems using different transmission methods are mixed. The present invention relates to a communications system in which a plurality of systems share the same frequency bandwidth so as to transmit information symbols. One of the plurality of systemsincludes an identifying unitconfigured to identify the symbol length of an information symbol transmitted in a different system; and an adjusting unitconfigured to adjust the symbol length of an information symbol to be transmitted, in accordance with an identified symbol length.

Communications system, communications method, transmitting apparatus, receiving apparatus and control program to variably adjust a symbol length

An OFDM signal frame generator includes a rate determiner configured to determine rate information to generate a signal frame to be transmitted as an OFDM signal based on a value of a received signal quality. The signal frame generator further includes a pilot and data arrangement format determiner configured to determine a pilot and data arrangement format of the signal that is to be transmitted; power amplification rate determiner configured to determine a power amplification rate for the signal frame; data symbol generator configured to generate data symbol series to be transmitted based on the rate information and based on the power amplification rate; and transmission signal frame generator configured to generate the signal frame based on the generated data symbol series, on the number of pilot symbols, and based on the pilot & data arrangement format.

OFDM signal frame generator, transmitter, signal transmission system and OFDM signal frame generating method

A mobile terminal comprises a transmitter/receiver configured to transmit/receive a signal to/from a base station, a communication state determination unit configured to determine a communication state of the transmitter/receiver, a movement state measurement unit configured to measure a movement state of the mobile terminal, and a reception period controller configured to control a reception period for receiving a control signal transmitted from the base station by the transmitter/receiver, based on a communication state determination result determined by the communication state determination unit and a movement state measurement result measured by the movement state measurement unit.

Mobile terminal, control device, communication system and communication method with multistate reception control

In an adaptive equalizing apparatus for MIMO (Multi-Input Multi-Output) turbo reception, an interference component in a received signal is subtracted therefrom using a replica of an interference component in an interference canceling part, the subtracted output is filtered by a filter, to cancel the remaining interference component and to perform multi-path combining, and in a degree-of-interference-cancellation estimation part 41the degree of interference cancellation &#x3b2;(i) is set such that it is 0 for the iteration number i=1, 0.8+0.05 (i&#x2212;1) for 5&#x2267;i&#x2267;2 and 1 for i&#x2267;6, and at the beginning of each iteration filter coefficients are calculated using &#x3b2;(i) and a channel estimation value in a filter coefficient calculating part 33and the filter coefficient thus calculated are set in the filter. An average value of soft decision symbol estimation values used in the interference canceling part may be used as &#x3b2;.

Adaptive equalizing apparatus and program therefor

The accuracy of an equalization start timing, an equalization duration and a channel estimation is improved in an application including an increased number of users. An equalization start timing tan equalization duration te and channel H estimation are performed for each user signal, and using these, received signal replicas Rero Refor the respective users are generated. The replicas are subtracted from the received signal to provide an error signal, and Reto Reare added to Es to provide an interference suppressed received signals for the usersto N. to, te, H and Reto Reare generated from these to generate Es in a repeated fashion to improve the accuracy of tte and H.

MIMO receiver and method of reception therefor

A correlation between a received signal and a sync word signal is calculated. A window signal having a time span which is equal to an equalization range for an adaptive equalizer is defined. A power sum of the correlation output signal in each of window signals #, . . . are calculated by sequentially shifting the window signal in the time domain, and a rising edge of the particular window signal whose power sum maximum defines a symbol sync timing.

Adaptive equalization apparatus and method

An impluse response h(q) of each transmission path is estimated from N received signals r(m=1, . . . , M) and a known signal (for a number of users equal to N, n=1, . . . , N). M&#xd7;N matrix H (q) having h(q) as an element and a Q&#xd7;Q matrix H having H(q) as an element are determined (where Q represents a number of multipaths of each transmitted wave and q=0, . . . , Q&#x2212;1). A soft decision value b'(k) is determined from decoded &#x3bb;[b(k)], and this is used to generate an interference component matrix B&#x2032;(k) to generate an interference replica H&#xb7;B&#x2032;(k). The interference replica H&#xb7;B&#x2032;(k) is subtracted from a received matrix y(k) to determine y&#x2032;(k). y(k) and H are used to determine an adaptive filter coefficient w(k) to be applied to an n-th user in order to eliminate residual interference components in y&#x2032;(k) according to the minimum mean square error criteria. y(k) is passed through w(k) to provide a log-likelihood ratio as a received signal from the user n from which interferences are eliminated.

Turbo-reception method and turbo-receiver

A radio receiver includes a plurality of antenna elements for receiving a radio signal from a radio transmitter; a setting part changing an impedance of at least one of the plurality of antenna elements according to an instruction signal; a measuring part measuring a change in throughput in a received signal caused due to the change in the impedance; and an instruction part providing the instruction signal which is changed in response to the measurement result.

Radio receiver, radio transmitter and impedance control method

Outputs from respective elements of an array antennaare demodulated, and the demodulated outputs are stored in storage means. The demodulated outputs are multiplied by tap coefficients of adaptive array antenna, then the multiplied outputs are combined by combining means, and the combined output is provided via a feed forward filterto an adaptive equalizer, wherein it is equalized to obtain a decision symbol. During reception of a training signal the tap coefficients of adaptive array antenna and tap coefficients of the adaptive equalizerare subjected to convergence processing by tap coefficient calculating meansso that an error signal becomes small, and then tap coefficients of the feed forward filterand the adaptive equalizerare subjected to convergence processing by tap coefficient calculating meansso that an error signal becomes small. Thereafter, the convergence processing by the meansandis repeated, during which a training signal stored in storage meansis used, results of the immediately preceding convergence processing are used as initial values, and it is decided by receiving quality estimating meanswhether the error signal has become sufficiently small relative to the received signal power.

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Okayama, Japan

Shigeru Tomisato