Abstract: A retransmission control apparatus for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, the apparatus comprising a transmitter which transmits to a radio station a data sequence, which serves as communication data that has been transformed into a time waveform of an orthogonal frequency division multiplexing symbol; a receiver which receives from the radio station a retransmission request for retransmitting the communication data; a transformation mechanism configured to transform, in response to the retransmission request, the data sequence of the communication data to be retransmitted into an orthogonal frequency division multiplexing symbol having a time waveform different from the time waveform of the orthogonal division multiplexing symbol which had been sent before the retransmission request; and a retransmitting mechanism configured to retransmit the communication data transformed by the transformation mechanism to the radio station.

Abstract: An orthogonal frequency division multiplexing (OFDM) receiving signal from a plurality of antenna elements having identical characteristics is supplied to an excitation weight calculating part. An excitation weight is calculated for use in controlling excitation for each antenna element and each subcarrier based on the element intervals of the antenna elements and the frequency intervals of OFDM subcarriers. A receiving signal from the antenna elements is assigned the calculated excitation weight by an excitation weight assigning part. Thus, the optimum array pattern is obtained in a desired direction in all bands of the OFDM signal, thereby realizing the transmission and reception without an influence of interference waves.

Abstract: A coherent detection type OFDM receiver is disclosed. The coherent detection type OFDM receiver demodulates a digital data sequence. The OFDM receiver obtains a channel frequency response with a frequency spectrum of a received signal and a frequency spectrum of a reference signal. The channel frequency response is filtered in the frequency domain by a filter. At this point, the OFDM receiver estimates delay time of a received delayed signal and designates the bandwidth of the filter with the estimated result. The OFDM receiver compensates the distortion of the waveform of the received signal with the channel frequency response that has been filtered by the filter and demodulates a digital data sequence with the received waveform that has been compensated.

Abstract: According to the present invention, there is provided an adaptive array antenna including a plurality of antenna elements for receiving radio waves transmitted via multi-carrier waves, weighting means for weighting received signals received by the plurality of antenna elements with weight amounts for the respective antenna elements, adding means for adding up weighted signals by the weighting means, extracting means for extracting particular carrier components from the received signals received by the plurality of antenna elements, and weight setting means for setting the weight amounts for the respective antenna elements to the weighting means on the basis of the particular carrier components extracted by the extracting means.

Abstract: A large amount of user information is transmitted with good efficiency by means of a high-speed downlink by making transmission rates of an uplink circuit and a downlink asymmetrical. The radio communication system includes a plurality of base stations, a plurality of terminals, an uplink established between each of the base stations and each of the terminals for the purpose of radio transmission of prescribed information from a terminal to a base station, and a downlink circuit established between each of the terminals and each of the base station for the purpose of radio transmission of prescribed data from a base station to a terminal.

Abstract: A sampling phase synchronizing apparatus includes a received signal memory for storing a received signal partially including training codes, a channel response calculator for calculating the time response of a channel (to be referred to as a channel response hereinafter) unique to the reception time using a partial sequence of the training codes included in the received signal stored in the received signal memory, a power ratio calculator for calculating the ratio between the power of the channel response calculated by the channel response calculator, and the power of a portion of the channel response, a power ratio memory for storing the power ratio calculated by the power ratio calculator, and a sampling phase deciding section for determining a sampling phase using the power ratio stored in the power ratio memory. The apparatus samples the received signal with reference to the sampling phase determined by the sampling phase deciding section.

Abstract: A large amount of user information is transmitted with good efficiency by means of a high-speed downlink by making transmission rates of an uplink circuit and a downlink asymmetrical. The radio communication system includes a plurality of base stations, a plurality of terminals, an uplink established between each of the base stations and each of the terminals for the purpose of radio transmission of prescribed information from a terminal to a base station, and a downlink circuit established between each of the terminals and each of the base station for the purpose of radio transmission of prescribed data from a base station to a terminal.

Abstract: An adaptive maximum likelihood sequence estimation apparatus includes a first estimation unit for estimating a transmission signal sequence from received signals on the basis of an estimated transmission path impulse response. A second estimation unit estimates an estimated received signal at time k on the basis of a known signal sequence or the transmission signal sequence estimated by the first estimation unit, and a transmission path impulse response estimated at time k-1. An error signal generation unit generates an error signal on the basis of a received signal at time k and the estimated received signal at time k. A third estimation unit estimates a transmission path impulse response at time k using a predetermined adaptive algorithm on the basis of the error signal.

Abstract: A sampling phase synchronizing apparatus includes a received signal memory for storing a received signal partially including training codes, a channel response calculator for calculating the time response of a channel (to be referred to as a channel response hereinafter) unique to the reception time using a partial sequence of the training codes included in the received signal stored in the received signal memory, a power ratio calculator for calculating the ratio between the power of the channel response calculated by the channel response calculator, and the power of a portion of the channel response, a power ratio memory for storing the power ratio calculated by the power ratio calculator, and a sampling phase deciding section for determining a sampling phase using the power ratio stored in the power ratio memory. The apparatus samples the received signal with reference to the sampling phase determined by the sampling phase deciding section.

Abstract: An adaptive maximum likelihood sequence estimation apparatus includes a first estimation unit for estimating a transmission signal sequence from received signals on the basis of an estimated transmission path impulse response. A second estimation unit estimates an estimated received signal at time k on the basis of a known signal sequence or the transmission signal sequence estimated by the first estimation unit, and a transmission path impulse response estimated at time k-1. An error signal generation unit generates an error signal on the basis of a received signal at time k and the estimated received signal at time k. A third estimation unit estimates a transmission path impulse response at time k using a predetermined adaptive algorithm on the basis of the error signal.

Abstract: A demodulation apparatus incorporating an adaptive equalizer, capable of realizing a highly reliable communication, lower power consumption, and a compact size. In the demodulation apparatus, an output of one of two demodulators, at least one of which including an equalizer, is selected according to a presence or absence of multipath which is determined from a non-coincidence of bit codes, eye apertures, bit error ratea, or a matched filter output, while the operation of the other demodulator is stopped for reduction of power consumption, by stopping a supply of power or clock signals to the other demodulator. In a case using a frequency offset detection unit and a frequency offset memory, one of these is selected according to a convergence or divergence of an error signal from an equalizer, while the operation of the other one is stopped for reduction of power consumption.

Abstract: A method of equalization in a digital mobile communication capable of realizing an improved tracking of the variations of the transmission path characteristics, such that it becomes possible to achieve the good error rate characteristic. In the method, the forward and backward equalizations are carried out, while the forward and backward evaluation functions indicating reliabilites of the forward and backward equalizations are calculated by using the signal sequence, and a final equalization output is obtained by selecting for each bit of the signal sequence one of the forward and backward equalization outputs for which the reliability indicated by corresponding one of the forward and backward evaluation functions is higher as final equalization output for each bit. The detection of an abnormal state such as a sudden drop of a signal strength of the signal sequence or a limit cycle state of an equalizer may be used instead of the evaluation functions.

Abstract: A demodulation apparatus incorporating an adaptive equalizer, capable of realizing a highly reliable communication, lower power consumption, and a compact size. In the demodulation apparatus, an output of one of two demodulators, at least one of which including an equalizer, is selected according to a presence or absence of multipath which is determined from a non-coincidence of bit codes, eye apertures, bit error rates, or a matched filter output, while the operation of the other demodulator is stopped for reduction of power consumption, by stopping a supply of power or clock signals to the other demodulator. In a case using a frequency offset detection unit and a frequency offset memory, one of these is selected according to a convergence or divergence of an error signal from an equalizer, while the operation of the other one is stopped for reduction of power consumption.

Abstract: A demodulation apparatus incorporating an adaptive equalizer, capable of realizing a highly reliable communication, lower power consumption, and a compact size. In the demodulation apparatus, an output of one of two demodulators, at least one of which including an equalizer, is selected according to a presence or absence of multipath which is determined from a non-coincidence of bit codes, eye apertures, bit error rates, or a matched filter output, while the operation of the other demodulator is stopped for reduction of power consumption, by stopping a supply of power or clock signals to the other demodulator. In a case using a frequency offset detection unit and a frequency offset memory, one of these is selected according to a convergence or divergence of an error signal from an equalizer, while the operation of the other one is stopped for reduction of power consumption.