Abstract: A clock-frequency-deviation detecting unit detects a clock-frequency deviation based on a synchronization signal for taking a frame synchronization included in a reception signal. A clock-frequency-deviation compensating unit compensates a clock-frequency deviation of the reception signal in a former stage of an FFT unit. A timing control unit controls a frame pulse position indicating a head of a frame, based on the synchronization signal. The FFT unit performs an FFT on the reception signal with the frame pulse position as a frame head position, and a demodulating unit demodulates an output of the FFT unit.

Abstract: A preamble design method of generating a preamble for a plurality of symbols using time waveform data of a specific symbol in an OFDM communication system includes a dividing step of dividing the time waveform data of the specific symbol into a plurality of blocks equivalent to number of symbols in the preamble, a symbol-unit-block selecting step of selecting a separate block from among divided blocks in units of symbols in the preamble, and a symbol-unit time-waveform-data generating step of generating time waveform data having a different pattern for each of the symbols by generating time waveform data for a single symbol in which a selected block is set as a leading block and data are cyclically arranged from leading data in the selected block.

Abstract: A clock-frequency-deviation detecting unit detects a clock-frequency deviation based on a synchronization signal for taking a frame synchronization included in a reception signal. A clock-frequency-deviation compensating unit compensates a clock-frequency deviation of the reception signal in a former stage of an FFT unit. A timing control unit controls a frame pulse position indicating a head of a frame, based on the synchronization signal. The FFT unit performs an FFT on the reception signal with the frame pulse position as a frame head position, and a demodulating unit demodulates an output of the FFT unit.

Abstract: A preamble design method of generating a preamble for a plurality of symbols using time waveform data of a specific symbol in an OFDM communication system includes dividing the time waveform data of the specific symbol into a plurality of blocks equivalent to a number of symbols in the preamble, selecting a separate block from among divided blocks in units of symbols in the preamble, and generating time waveform data having a different pattern for each of the symbols by generating time waveform data for a single symbol in which a selected block is set as a leading block and data are cyclically arranged from leading data in the selected block.

Abstract: The transmitter comprises a data/modulation control section (4) which sets predetermined parameters necessary for demodulation processing, sub-carrier group modulation processing sections (6a to 8c) which perform frequency spreading for each sub-carrier signal in the sub-carrier group, and time spreading sections (10a to 10c) which multiplex all signals after the modulation processing and the frequency spreading for each sub-carrier signal, and perform time spreading with respect to the multiplexed signals. The receiver comprises time despreading sections (35a to 35c) which perform time despreading for each sub-carrier signal, and sub-carrier group demodulation processing sections (36a to 38c) which perform frequency despreading for each sub-carrier signal after the time despreading.

Abstract: The transmitter comprises a data/modulation control section (4) which sets predetermined parameters necessary for demodulation processing, sub-carrier group modulation processing sections (6a to 8c) which perform frequency spreading for each sub-carrier signal in the sub-carrier group, and time spreading sections (10a to 10c) which multiplex all signals after the modulation processing and the frequency spreading for each sub-carrier signal, and perform time spreading with respect to the multiplexed signals. The receiver comprises time despreading sections (35a to 35c) which perform time despreading for each sub-carrier signal, and sub-carrier group demodulation processing sections (36a to 38c) which perform frequency despreading for each sub-carrier signal after the time despreading.

Abstract: In an interference wave detection/study process, counters m.sub.i (t.sub.j), n.sub.i (t.sub.j) are set by an initial value "zero" to set the detection number of an interference wave of not less than a threshold power level per channel i and per time period ti. The m.sub.i (t.sub.j) is updated, then the power U.sub.i of a measured interference wave is compared with the threshold value r. The n.sub.i (t.sub.j) is updated only when U.sub.i .gtoreq.r. The n.sub.i (t.sub.j) is divided by m.sub.i (t.sub.j) to obtain the arriving probability of an interference wave. These processes are repeated over all channels. In a channel search/allocation process, the power U.sub.i of the interference wave in the smallest W.sub.i (t.sub.j) is compared with a value r, When U.sub.i (t.sub.j).gtoreq.r, the channel having the second smaller W.sub.i (t.sub.j) is selected and the above processes are repeated. it becomes a calling loss when all channels are searched. When U.sub.i <r, this channel is allocated.

Abstract: A carrier phase estimation apparatus include a base band converter and a phase estimator. A received IF signal is converted to an in-phase component In and an quadrature component Qn of a digital base band signal in the base band converter. In the phase estimator, a non-linear circuit executes a non-linear operation of the components In and Qn to output non-linearly converted in-phase component In' and quadrature component Qn' of the digital base band signal and the components In' and Qn' are input to a pair of filters. In each filter, the components In' or Qn' are stored into shift registers at a predetermined timing and the signals stored in the shift registers are multiplied by respective weighting factors C.sub.k in respective multipliers. The multiplied values are summed by an adder and the obtained sum is divided by a stage number N of the shift register in a divider to obtain filtering signals Xn and Yn.

Abstract: A radio communication system represented by a micro cellular system and a channel allocation method suitable therefor. A receive signal level is measured in response to a call request issued from a mobile station. A search start channel is determined based on a measured level, and a search is sequentially made on a plurality of radio communication channels, starting with the thus determined search start channel, being a starting point. A radio communication channel specified by this search is subjected to evaluation of communication quality. The above search and communication quality evaluation are repeated while advancing the starting point to the subsequent radio communication channel until the evaluation result equals or exceeds a predetermined value. When the evaluation result equals or exceeds the predetermined value, radio communication is initiated between the mobile station and a base station by way of a specified radio communication channel.

Abstract: A spread spectrum demodulator for use with a phase-shift-keying modulated spread spectrum signal used in mobile satellite communications. An objective of the spread spectrum demodulator is to perform tracking by producing from a correlation pulse signal an error signal having a time discrimination characteristic. The spread spectrum demodulator generates from the correlation pulse signal an error signal whose level varies in response to a phase difference between a pseudonoise signal contained in a received signal and a reference pseudonoise signal. A clock in synchronism with the received signal is generated from this error signal, thereby demodulating the received signal.