Abstract: An OFDM communication apparatus comprises subcarrier selecting means for selecting subcarriers to be transmitted for each branch in accordance with the number of retransmissions of transmitting signals and transmitting means for providing TIFFT processing to transmitting signals arranged in said subcarriers for each branch to transmit the resultant.

Abstract: A wireless communication apparatus and a receiving scheme selection method are provided for improved overall system throughput. SIR measurer (106) measures the SIR of a known signal. Doppler frequency detector (108) detects the Doppler frequency from the received signal and measures the Doppler shift amount. The Doppler shift amount serves as an indicator of the moving speed of the mobile station apparatus. Interference power measurer (110) measures interference power from other cells. Known signal obtainer (104), SIR measurer (106), Doppler frequency detector (108), and interference power measurer (110) constitute a propagation environment estimator in this embodiment. Based on the SIR, Doppler shift amount, and interference power, receiving scheme selector (112) selects a receiving scheme of either RAKE reception or linear equalization.

Abstract: The number of multiplexing of individual transmit symbols is selected by means of selection sections B1 through B5. The number of spread signals selected by selection sections B1 through B5 are multiplexed adders C1 through C5. By this means, it is possible to select inter-code interference in code division multiplexed signal transmission on a symbol-by-symbol basis, enabling error rate characteristic quality to be selected on a symbol-by-symbol basis. As a result, if a symbol for which the number of multiplexing is reduced and error rate characteristics are made good is selected as appropriate, error rate characteristics can be improved without degrading frequency characteristics so much.

Abstract: A radio receiving system, which receives an input signal in a direct conversion receiving mode through the use of a plurality of cascaded channel filters, each including a complex coefficient filter, to obtain a desired waveform, wherein a center frequency of a preliminary channel filter corresponds more closely with the frequency of the desired waveform than a center frequency of a subsequent channel filter.

Abstract: A transmission-reception apparatus does not configure ARQ control information from only sequence number, but the transmission-reception apparatus configures the ARQ control information such that the ARQ control information is comprised of one sequence number containing first occurrence of a corresponding packet's error, and bit information representing existence of retransmission requirements about sequence numbers followed on the heels of such the one sequence number.

Abstract: A transmit signal is spread by a plurality of spreading sections 103, 104, 105, and 106, using different spreading codes. A selection section 107 increases the number of spread signals to be output as the number of retransmissions increases. By this means, a retransmission signal spread by means of many spreading codes is code division multiplexed. As a result, retransmission signal error rate characteristics are improved on the receiving side by despreading this code division multiplexed signal using the same plurality of spreading codes as on the transmitting side, and selecting or combining the despreading results with the greatest correlation power thereamong. Also, since the degree of code multiplexing is increased proportionally as the number of retransmissions increases, retransmission signal error rate characteristics can be improved without lowering spectral efficiency unnecessarily.

Abstract: Modulation system estimator 108 sets an amplitude value of a signal modulated with a multivalue modulation with the less number of bits per symbol among two modulation systems selectively used at a reference amplitude value, and estimates the modulation system applied on a received signal from a level of a difference between an amplitude value of a received signal and the reference amplitude value. First decider 109 makes a decision on a received symbol based on a first modulation system, second decider 110 makes a decision on a received symbol based on a second modulation system, and based on a modulation system estimated by modulation system estimator 108, selector 111 selects either output from first decider 109 or second decider 110 to output.

Abstract: The OFDM reception apparatus according to the present invention comprising: FFT processor for performing a FFT processing on a reception signal; a plurality of demodulators capable of performing mutually different demodulation processes on the FFT-processed reception signal; and a selector for selecting, among the plurality of demodulators, a demodulator that should perform the demodulation process on the FFT-processed reception signal according to a factor that influences the quality of a demodulated signal and letting the selected demodulator perform the demodulation process.

Abstract: Synchronization symbol insertion section 102 inserts a synchronization symbol into a signal digital-modulated by modulation section 101. 0 symbol insertion section 103 inserts a 0 symbol into the signal with the synchronization symbol inserted. The signal with the synchronization symbol and 0 symbol inserted in this way is sent to IFFT section 104 to be subjected to an IFFT calculation. Then, guard interval insertion section 105 inserts a guard interval into the IFFT-transformed signal waveform. Then, the signal with the guard interval inserted in this way is D/A-converted by D/A converter 106. The D/A-converted signal is subjected to normal radio transmission processing and then transmitted.

Abstract: Diversity control section 111 calculates received amplitude levels of all subcarrier signals from all branches, and selects a branch providing the largest amplitude level for each subcarrier signal. Based on the above selection result, selectors 104 are switched to transmit respective subcarrier signals from the selected branch, and selectors 112 are switched to receive respective subcarrier signals from the selected branch.

Abstract: A data retransmission method, providing a practical ARQ (Automatic Repeat request) scheme in multicarrier communication such as OFDM. According to this method, all the carriers (i.e. subcarriers) are divided into a number of groups in advance, and these groups serve as the unit of data retransmission. An error detection code is attached on a per transmission symbol basis and transmission is performed, and, when mobile terminal apparatus 100 at the receiving end detects an error, subcarrier information obtainer 130 counts the number of carriers having received level below predetermined standard on a per group basis, and makes the group having the count value above a threshold level subject to retransmission request.

Abstract: When OFDM signals are transmitted from a plurality of antennas, a pilot carrier is transmitted from one antenna among the plurality of antennas, and a null signal is transmitted from an antenna other than that antenna by a subcarrier of the frequency band that transmits the pilot carrier.

Abstract: In the case of transmitting a signal of at least three bits in one symbol, when receiving a retransmission request signal from a radio station of a communication partner, a transmission apparatus 10A retransmits only the bits (lower bits) that are susceptible to error, without retransmitting the bits (higher bits) that are not readily susceptible to error and that are obtained by processing in a modulation section 11. A reception apparatus 10B of the communication partner performs error correction processing using the bits (higher bits) and that are stored in memories 16 and 17 and that are not readily susceptible to error, and the bits that are obtained by retransmission and that are susceptible to error (lower bits).

Abstract: When transmission is performed using the OFDM-CDMA method, subcarriers #1 through #m, #2m+1 through #3m, #3m+1 through #4m, and #4m+1 through #5m in which spread signals are allocated only in the frequency axis direction, and subcarriers #m+1 through #2m in which spread signals are allocated in both the frequency axis direction and the time axis direction, are formed, and these are transmitted simultaneously.

Abstract: A method and appparatus for setting a guard interval in an OFDM communication. The method includes attaching a part of a first valid symbol to the first valid symbol as a guard interval and attaching a part of a second valid symbol requiring higher channel quality than the first valid symbol, to the second valid symbol as a guard interval, and providing the guard interval of the second valid symbol at a length greater than the guard interval of the first valid symbol.

Abstract: An average value of reception power of subcarriers A to D is calculated by a control circuit 162, and the average value is divided by envelops of received signals of subcarriers A to D, respectively, so as to calculate a coefficient signal of each subcarrier. Multipliers 106 to 109 multiply transmitting signals of subcarriers A to D output from mapping circuits 102 to 105 by the coefficient signals, respectively. Whereby, power between the subcarriers at a reception time can be maintained substantially constant so as to improve an error rate characteristic.

Abstract: The degree of multiplexing of a code division multiplexed signal transmitted by subcarriers is selected on a subcarrier-by-subcarrier basis. As a result, inter-code interference on the propagation path and degradation on the propagation path are lower for a code division multiplexed signal allocated to subcarriers with a low degree of signal multiplexing (G1) than for transmit signals allocated to subcarriers with a high degree of multiplexing. By this means, it is possible to prevent degradation of the error rate characteristics of important information without lowering spectral efficiency significantly as compared with the case in which the degree of signal multiplexing is decided uniformly for all subcarriers, and to achieve compatibility between spectral efficiency and error rate characteristics.

Abstract: The subtractor of the reception system calculates the channel quality using an optimal guard interval length detection signal inserted into one carrier by the transmission system, then the optimal guard interval length detector calculates the minimum guard interval length necessary to eliminate delayed signals using this calculated channel quality, inserts the control signal indicating this guard interval length into one carrier and the reception system sets the guard interval length using this control signal.

Abstract: The transmitting side is equipped with chip steering section 30 that performs a chip steering that shifts the allocation of N×M chip elements upon their respective subcarriers by one chip for every transmission unit in sequence, and the receiving side is equipped with a parallel/serial conversion section and an inverse chip steering section that rearranges the allocation of the chip elements shifted in chip steering section 30 back to original.

Abstract: Level detectors 305 to 312 detect reception levels of uplink bursts received by their respective subcarriers/branches, then interpolation sections 313 to 320 estimate reception levels of the next uplink burst from the reception levels of a plurality of uplink bursts detected, select the branch with the maximum estimated value for each subcarrier and sends each subcarrier of the next downlink burst to be transmitted using this selected branch.