Abstract: A base station configured to communicate with a mobile station includes a controlling-information transmitting unit and a receiving unit. The controlling-information transmitting unit is configured to transmit to the mobile station as a set of controlling information, an information set indicating an environment of a cell which is resided by the mobile station, or an information set indicating power of interference from surrounding cells, or an information set indicating a condition of propagation channel. The receiving unit is configured to receive a signal transmitted from the mobile station, based on said set of controlling information, via a variably-controlling process of a spreading factor and a number of chip repetitions.

Abstract: A transmitter used in a wireless communication system based on an orthogonal frequency division multiplexing (OFDM) scheme includes a determination unit that determines a spreading factor and an amplitude for a control channel based on at least one of signal quality information and interference information in data transmission. The transmitter also includes a multiplexing unit that multiplexes a data channel with the control channel having been code-spread based on the spreading factor and the amplitude. A modulator then modulates the multiplexed signal in the OFDM scheme for transmission as OFDM symbols.

Abstract: A mobile station that wirelessly transmits to a base station by DS-CDMA a signal spread by multiplying a spreading code includes a chip-pattern generating unit that generates a predetermined chip pattern by performing chip repetition for a predetermined number of repetitions to a spreading chip sequence, and a multiplying unit that multiplies to a signal including the predetermined chip pattern generated by the generating unit a phase specific to the mobile station.

Abstract: A radio transmission system is configured to, on the occasion of radio transmission of information between a transmitter and a receiver, perform the radio transmission of information using an orthogonal frequency and code division multiplexing transmission scheme of parallelly transmitting identical information by a plurality of sub-carriers. The radio transmission system has a spreading factor variable control transmitting device for parallelly converting information channel-coded at the transmitter, according to symbols transmitted simultaneously, and for spreading a sequence of parallelized symbols in at least one of a frequency direction and a time direction by a spreading code sequence of a designated spreading factor.

Abstract: A mobile communication system 1 according to the present invention comprises base station 30 and mobile station 10. The base station 30 sends a pilot symbol sequence known to the mobile station 10, to the mobile station 10, using a plurality of carriers for downward channels, and performs communication with the mobile station 10 while multiplying the channels by frequencywise same scrambling codes every symbol period. The mobile station 10 is provided with a peak detector 17 for calculating cross correlation allowing for a phase difference of the scrambling codes, between frequencywise pilot symbol sequences received from the base station 30, thereby detecting a radio frame boundary.

Abstract: The present invention provides a single carrier/DS-CDMA packet transmission method wherein a predetermined time slot is assigned to reservation demand packet transmission in regard to a spreading code, and the reservation demand packet and data packets are time-multiplexed for transmission. An uplink packet transmission method in a multi-carrier/DS-CDMA mobile communication system is also provided, wherein frames are set up in each communication channel of a subcarrier, time slots which are time-segments of the frames are set up further, and a mobile station spreads a packet to be transmitted by a spreading code and the information signal is transmitted to a base station in a predetermined time slot.

Abstract: The present invention provides a single carrier/DS-CDMA packet transmission method wherein a predetermined time slot is assigned to reservation demand packet transmission in regard to a spreading code, and the reservation demand packet and data packets are time-multiplexed for transmission. An uplink packet transmission method in a multi-carrier/DS-CDMA mobile communication system is also provided, wherein frames are set up in each communication channel of a subcarrier, time slots which are time-segments of the frames are set up further, and a mobile station spreads a packet to be transmitted by a spreading code and the information signal is transmitted to a base station in a predetermined time slot.

Abstract: The present invention provides a single carrier/DS-CDMA packet transmission method wherein a predetermined time slot is assigned to reservation demand packet transmission in regard to a spreading code, and the reservation demand packet and data packets are time-multiplexed for transmission. An uplink packet transmission method in a multi-carrier/DS-CDMA mobile communication system is also provided, wherein frames are set up in each communication channel of a subcarrier, time slots which are time-segments of the frames are set up further, and a mobile station spreads a packet to be transmitted by a spreading code and the information signal is transmitted to a base station in a predetermined time slot.

Abstract: A multi-carrier CDMA transmission system signal format that reproduces data symbols, aligns the reproduced data symbols along a frequency axis, multiplies the reproduced data symbols by a spreading code, and conducts multiplex transmission of data using a plurality of sub-carriers of different frequencies, in which a common pilot symbol inserted in a transmission signal for estimating a variation in channel and estimating a channel common to each of a plurality of users, and a user-specific individual pilot symbol transmitted along a channel different from the above-described channel.

Abstract: Received signals of the respective sub-carriers are multiplied by a weighting controlled for each sub-carrier, using a weighting control part 2-8 and multipliers 2-9, so that the mean square error between the signals following despreading and the signals that are actually transmitted is minimized. Afterward, MMSE combining is performed.

Abstract: A communication system and method includes the steps of: a) transmitting an ACK signal indicating a received packet includes no error or a NACK signal indicating the received packet includes error from a reception end to a transmission end, and performing automatic repeat request; b) obtaining reliability of the received packet when demodulating it at the reception end; and c) reporting from the reception end to the transmission end the reliability of the received packet utilizing the ACK/NACK signal by using not less than three levels.

Abstract: The transmission system of the present invention is designed to transmit a plurality of signals between the transmitter and the receiver using a plurality of carriers and comprises a radio link characteristics estimator 4 configured to estimate the characteristics of a radio link between the transmitter and the receiver and a carrier quantity determination unit 3 configured to determine the number of carriers according to the result of the estimate by the radio link characteristics estimator 4. The radio link characteristics estimator 4 estimates the characteristics according to an interval in delay time of multipath signals and the number of the multipath signals. The carrier quantity determination unit 3 determines fewer carriers when multipath interference is small, and determines more carriers when the multipath interference is great.

Abstract: A channel estimation circuit (101) of the present invention includes: a tentative channel estimation unit (102) for performing channel estimation by making use of a received signal and outputting the result of estimation as a tentative channel estimation signal; a noise/interference power estimation unit (103) for estimating noise and interference power by making use of the received signal and outputting the result of estimation as a noise/interference power estimation signal; a threshold decision unit (104) for establishing a threshold signal by making use of the noise/interference power estimation signal to output the threshold signal; and an effective path detection unit (105) for outputting, as a channel estimation signal, paths of the tentative channel estimation signal that remains after noise paths having powers smaller than the threshold signal have been removed.

Abstract: A radio transmitter-receiver wherein a pilot symbol is used in the transmitter that has undergone M-chip spreading on the frequency axis and N-chip spreading on the time axis by a spreading code of M×N chip length (where M and N are any integers equal to or greater than 2), and in the receiver, a spreading code that is not used in spreading said pilot signal is used as a despreading code to despread a received signal and then estimate noise and interference power. The spreading code that is used to spread the pilot symbol and the despreading code that is used in despreading are assigned so as to be orthogonal even if only in N chips on the time axis.

Abstract: A receiver, comprising a plurality of antennas configured to receive signals that are obtained by multiplying a plurality of data symbols transmitted over a plurality of data channels using spreading codes for each of the data channels, the data symbol being transmitted over a plurality of sub-carriers having different frequencies; a spreading code multiplier configured to multiply reception signals received by the plurality of antennas using spreading codes for the data channels corresponding to the reception signals; a weight controller configured to adjust antenna weights by which a reception signal received by each antenna is to be multiplied, and sub-carrier weights by which a reception signal received over each sub-carrier is to be multiplied; a weight multiplier configured to multiply the reception signals by the antenna weights and the sub-carrier weights adjusted by the weight controller; and a combining unit configured to combine the reception signals multiplied by the antenna weights and the sub-ca

Abstract: A pilot extract section 14 extracts a pilot signal from received signal. An adder 21 in-phase adds a plurality of correlated values of pilot signals for respective subcarriers. Delay devices 201-1 to 201-6 temporarily maintain one in-phase added value. Multiplier 202-1 to 202-6 multiplies a predetermined coefficient to the in-phase added value that is output from the delay device. The predetermined coefficient reflects the result, which is obtained by correcting for multiple times the difference of channel variation in the different subcarriers that is generated when noise power per one subcarrier is calculated. Each of the multiplying results is added by an adder 24, and is squared by a square device 25. A cumulative adder 26 cumulative-adds the squared values for the whole subcarrier. A multiplier 203 averages by multiplying predetermined values to the cumulative-added values.

Abstract: A communication device includes at least one of path search means for detecting respective timings of path components included a signal received via a multipath propagation path using pilot symbols of a known phase included in said received signal and channel estimation means for estimating channel variation using the pilot symbols. The path search means includes a first path search part for detecting respective timings of path components using pilot symbols and a second path search part for detecting respective timings of path components using information symbols derived from a signal demodulated according to the timings detected in the first path search part and pilot symbols. The channel estimation means includes a pilot symbol acquiring part for acquiring pilot symbols included in the received signal and a channel estimation part for implementing channel estimation using the acquired pilot symbols.

Abstract: A multi-carrier CDMA radio transmitting method replicates each information symbol and disposes thus-obtained information symbols along a frequency axis, multiplies the thus-obtained information symbols with a spreading code along the frequency axis, spreads the information symbols into components of a plurality of sub-carriers having different frequencies. The transmission rate of the information is changed by controlling the amount of information transmitted simultaneously by controlling the number of the information symbols to be used for spreading for the plurality of sub-carrier components for each user to which the information is to be transmitted.

Abstract: A base station, a mobile station, a radio communications system, and a radio transmission method are disclosed. The base station includes a control information determining unit configured to determine control information that includes a spreading factor, the number of chip repetitions, and a phase unique to the mobile station, based on at least one of information about the type of cell environments in which the mobile station is present, information about the number of mobile stations that are present in the cell, information about information rate required by the mobile station, information about a type of traffic, information about a radio parameter of the mobile station, information about a propagation path condition, and information about interference from an adjacent cell, and configured to transmit the spreading factor, the number of chip repetitions, and the unique phase of the mobile station that is determined to the mobile station.

Abstract: A transmitter (200) used in a wireless communication system based on an orthogonal frequency division multiplexing (OFDM) scheme includes a determination unit (216) configured to determine a spreading factor and an amplitude for a control channel based on at least one of signal quality information and interference information in data transmission, a multiplexing unit (212) configured to multiplex a data channel with the control channel having been code-spread based on the spreading factor and the amplitude, and means (214) configured to modulate the multiplexed signal in the OFDM scheme and transmit the modulated signal as OFDM symbols.