JP4193810B2 - Wireless communication method, wireless communication system, wireless base station, and wireless communication terminal - Google Patents

Description

The present invention is, for example, a suitable wireless communication method applied to a wireless communication system that performs data communication or the like, a wireless communication system, related to the radio base station and radio communication terminal end, particularly OFDM (Orthogonal Frequency Division Multiplex: orthogonal frequency division The present invention relates to a device suitable for wireless transmission using a multiplex) modulation method.

  Attempts have been made to use a wireless communication system developed as a wireless LAN system for transmitting information by the OFDM modulation system for public multicell service. In the case of the OFDM modulation scheme, a plurality of subcarriers are prepared in one prepared transmission channel, and information to be transmitted to each subcarrier is distributed and modulated to be transmitted. A wireless communication system using the OFDM modulation scheme is excellent in multipath resistance because the time length of one OFDM symbol can be made longer than the delay time of a multipath delay wave in mobile communication, and is suitable for mobile high-speed data communication. Is suitable.

  FIG. 29 is a diagram illustrating a carrier arrangement example of a conventional wireless communication system. Here, the carrier arrangement determined by a method called HiSWANa is shown. As center carrier frequencies, 5.17 GHz, 5.19 GHz, 5.21 GHz, and 5.23 GHz are defined, and each carrier is given a signal band of 20 MHz including a guard band.

  FIG. 30 is a diagram illustrating an example of subcarrier arrangement of one transmission channel in a conventional wireless communication system. In each 20 MHz band shown in FIG. 29, subcarrier groups generated by OFDM modulation are arranged every 312.5 kHz, and a total of 53 subcarriers are occupied for information transmission. Here, the subcarrier centered on DC in the equivalent baseband system (corresponding to the subcarrier having the center frequency f0 in the carrier frequency band), which is the center of the 53 subcarriers, is a null carrier in which information is not transmitted. (Null carrier). The frequency band used for information transmission is 16.5625 MHz, and approximately 1.7 MHz on both sides is reserved and not used as a guard band for isolation from adjacent carriers.

  FIG. 31 shows an example of a control signal transmission format in a conventional wireless communication system. In the system shown here, a transmission / reception unit called a MAC frame with a period of 2 msec is defined. One radio frame has a length of 2 msec, and is roughly divided into broadcast burst, downlink phase, uplink phase, contention. It consists of four parts of phase. In FIG. 3131, only the broadcast burst and the downlink phase are shown, and the downlink phase is shown as a downlink burst payload (DL burst payload).

  The broadcast burst and the downlink phase are sections in which transmission is performed from the base station to the terminal station, and the broadcast burst is a section in which control signals transmitted mainly to all terminal stations under the broadcast burst are transmitted in the downlink phase. Is a section mainly composed of a plurality of downlink bursts for transmitting traffic data to each terminal station. The uplink phase and the contention phase are sections in which transmission from the terminal station to the base station is performed. The broadcast burst includes a broadcast preamble, a BCH for broadcasting base station information, an FCH for notifying each terminal station of traffic channel allocation in the same frame, and an RCH used for a call from the terminal station. The ACH to which a response is made is included.

  The downlink phase includes SCH, which is a short traffic channel, and LCH, which is a long traffic channel. In the period of the downlink phase, a plurality of SCHs and / or LCHs can be used concatenated to one mobile station, and this is called a PDU (protocol data unit) train. A downlink preamble is added to the head of each PDU train. A PDU train with a downlink preamble added is called a downlink burst. In the uplink burst period, the short traffic channel SCH and the long traffic channel LCH are included. Also in the uplink, a PDU train is formed in the same manner as in the downlink, and an uplink preamble is added to the head of each PDU train. An uplink burst added to one PDU train is called an uplink burst. The contention phase includes an RCH used for a call from a mobile station, and an uplink preamble is added to the head of each RCH to form an uplink burst.

  The broadcast preamble has a length of 16 μsec, and the terminal station receives this section to perform base station search after power-on, initial synchronization acquisition, frame synchronization, frequency error correction, symbol synchronization, and the like. The downlink preamble has a length of 8 μsec, and the terminal station receives this section to perform more accurate timing correction, frequency error correction, symbol synchronization, and the like. The uplink preamble has a length of 16 μsec, and the base station receives this section to perform timing correction, frequency error correction, symbol synchronization, etc. for the transmission signal from the terminal station.

  In such a system, the terminal station call signal is transmitted as traffic channel assignment information to each terminal station in the FCH, and the terminal station in the standby mode waiting for being called up transmits all the BCH and FCH of the broadcast burst. After receiving it, it is determined whether or not you are called.

  In addition, in order to increase the standby time in the terminal station, the operation is such that the frame interval to be received is thinned out by the negotiation between the base station and the terminal station, rather than receiving the BCH and FCH of the broadcast burst at the head of every frame. A method is also possible.

  FIG. 32 shows a configuration example of a terminal station 300 in a wireless communication system to which a conventional OFDM modulation scheme is applied. First, the configuration of the transmission system will be described along the signal flow. In the case of audio communication, an audio signal is input to the data input / output processing unit 301 in the case of data communication connected to a computer, and converted into an appropriate digital data string. The output is input to the transmission data processing unit 311. If necessary, the control unit 302 receives communication control data to be transmitted to another OFDM radio apparatus (base station) that is a radio communication partner (not shown), After plexing, a frame or slot structure for transmission in the radio section is formed and output.

  The output is input to a CRC (Cyclic Redundancy Check) adding unit 312 and added with redundancy for error detection on the receiving side and output. The output is input to the encryptor 313, encrypted and output. The output is input to a scrambler 314, which is subjected to a scramble process that becomes pseudo-random according to a predetermined algorithm and is output. The output is input to the encoder 315, subjected to error correction encoding, and output. Various types of encoding are known, such as convolutional encoding, turbo encoding, Reed-Solomon encoding, or concatenated encoding using a combination of a plurality of encodings.

  The output of the encoder 315 is input to an interleaver 316 and subjected to interleaving to rearrange the encoded bit string according to a specific rule so that a burst error can be converted into a random error by performing a reverse operation on the receiving side. Is output. The output is input to the modulator 317 and mapped to a signal point at the time of transmission, and an in-phase component (I component) and a quadrature component (Q component) are output. The output is input to the complex IFFT unit 318, subjected to OFMD modulation by performing inverse FFT (Inverse Fast Fourier Transform), and output.

  The output is input to the time waveform shaping unit 319, for example, provided with a guard time by adding a cycle prefix, and subjected to a windowing process that smoothes the rise and fall of the OFDM modulation symbol and is output. The output is input to the DA converter 320, converted from a digital waveform to an analog waveform, and output. The output is input to the RF transmitter 321. In this RF transmitter 321, filtering, vector modulation by I and Q components, frequency conversion to an appropriate transmission frequency channel, transmission power control, amplification, etc. are performed and output.

  An output signal from the RF transmitter 321 is input to the antenna duplexer 322, and an output from the antenna duplexer 322 is input to the antenna 323, and finally transmitted from the antenna 323 as an electromagnetic wave. This transmission signal is received by another OFDM radio apparatus (base station) which is a radio communication partner (not shown). The antenna duplexer 323 is used to separate a transmission signal and a reception signal. An antenna switch is generally used in the TDD method and FDD / TDMA method in which transmission and reception are performed at different timings, and a duplexer is generally used in other methods. used.

  Next, the configuration of the reception system of the terminal station 300 will be described. Here, the signal received by the terminal station 300 is transmitted by another OFDM wireless device (base station) that is a wireless communication partner (not shown), and the same processing as the transmission system of the terminal station 300 described above. It is assumed that a transmission signal is made by performing the above.

  A transmission signal from another OFDM wireless device (base station) that is a wireless communication partner (not shown) is received by the antenna 323 as an electromagnetic wave. The signal is separated from the transmission signal of the local station by the antenna duplexer 322 and input to the RF receiver 331 which is a circuit of the reception system. In this RF receiver 331, amplification, attenuation of unnecessary frequency components, selection of a desired frequency channel, frequency conversion, reception signal amplitude level control, vector detection for separating I and Q components, band limitation, etc. are performed. I component and Q component are output. The output from the RF receiver 331 is input to the AD converter 332, converted from an analog waveform to a digital waveform, and output.

  The output is input to the synchronization circuit 333 and output after being subjected to frame synchronization, frequency error correction, and the like. When searching for a possible communication partner immediately after power-on or the like, the synchronization circuit 333 is configured to detect a synchronization signal or perform initial synchronization. The output of the synchronization circuit 333 is input to the time waveform shaping unit 334, and is output after being subjected to time waveform shaping that removes a guard time by adding a cycle prefix, for example. This output is input to the complex FFT unit 335, and subjected to OFDM demodulation by performing FFT (Fast Fourier Transform), and then output. This output is input to the equalizer 336.

  The equalizer 336 performs transmission path estimation and equalization based on the estimation result. In some cases, information of the synchronization circuit 333 is also input to the equalizer 336 and used for transmission path estimation and the like. The output of the equalizer 336 is input to the demodulator 337, subjected to signal point determination, and a received bit estimated value is output. The output is input to a deinterleaver 338, which is subjected to deinterleaving for rearranging the encoded bit string according to a specific rule and output. The output is input to the decoder 339, and the error correction code applied on the transmission side is decoded and output.

  The output is input to the descrambler 340, and descramble processing which is the inverse transform of scramble performed on the transmission side is performed and output. The output is input to the descrambler 341, and the encryption applied on the transmission side is released and output. The output is input to the CRC check unit 342, and the data from which the CRC has been removed and the CRC check result of the received block are output. The output is input to the reception data processing unit 343. If it is determined that there is no error as a result of the CRC check of the received block, the frame structure or slot structure applied for transmission in the wireless section is removed and output. The output is input to the data input / output processing unit 301. In the case of voice communication, an audio signal is converted into a data signal in the case of data communication connected to a computer and output.

  If the received data includes communication control data transmitted from a base station which is a wireless communication partner (not shown), the received data processing unit 343 extracts and outputs that portion, and the output is the reception system control line. The control unit 302 interprets the received control data and performs operation control of each unit of the terminal station 300 in accordance with the instruction.

  If an ARQ (Automatic Request for Reception) system is adopted, the reception data processing unit 343 operates as follows. That is, if the input signal from the CRC check unit 342 includes information that the reception block does not contain an error, the reception block is output to the reception data processing unit 343 as described above, The fact that no error is included in the block is output to the control unit 302 via the reception system control line 304, and the control unit 302 that has received this outputs another OFDM radio apparatus (base station) that is a radio communication partner (not shown). The transmission data processing unit 311 is instructed to transmit an ACK signal to the station) via the transmission system control line 303. The transmission data processing unit 311 multiplexes the transmission ACK signal into the transmission data, and so on, so that the ACK signal is transmitted to the base station by the processing of the transmission system already described.

  Conversely, if the input signal from the CRC check unit 342 includes information that the received block contains an error, the received block as described above is not output to the received data processing unit 343. The fact that the reception block contains an error is output to the control unit 302 via the reception system control line 304. Receiving this, the control unit 302 instructs the transmission data processing unit 311 via the transmission system control line 303 to transmit a NAK signal to a base station which is a wireless communication partner (not shown), and the transmission data processing unit 311 performs transmission. The NAK signal is transmitted to the base station according to the transmission system processing as described above, for example, by multiplexing the NAK signal into transmission data. The base station receiving this retransmits the block to which the NAK signal has been sent.

  In addition, in the case of stream communication such as voice communication in which retransmission such as ARQ is not used, the received data processing unit 343 operates as follows. That is, when the input signal from the CRC check unit 342 includes information that the reception block does not contain an error, the reception block is output to the reception data processing unit 343 as described above. On the other hand, if the input signal from the CRC check unit 342 includes information indicating that the received block contains an error, the received data processing unit 343 discards the received block and treats it as an erasure. Processing such as complementing using the previous reception block is performed.

  Each part of the transmission system is connected to the control unit 302 via a transmission system control line 303, and the control unit 302 performs on / off control of the transmission system, operation control / status monitoring of the RF transmitter 331, and transmission via this. It controls and monitors the operation of various transmission systems such as fine adjustment of timing, change of coding method and signal point mapping method, and retransmission control described above. Each unit of the reception system is connected to the control unit 302 via the reception system control line 304, and the control unit 302 controls the on / off control of the reception system, the operation control / status monitoring of the RF receiver 331, and the reception via the control unit 302. It controls and monitors the operation of various receiving systems such as fine adjustment of timing, change of decoding method and signal point demapping method, and retransmission control described above.

  In such an OFDM communication system, a signal for calling a terminal station from the base station side is transmitted by carrying information on all the subcarriers in the transmission band, and the terminal station receives all the subcarriers and receives the paging signal. I was doing. In other words, regardless of the presence or absence of data to be transmitted / received, a band signal of 20 MHz must be received and decoded every 2 milliseconds. Therefore, even when information data is not transmitted and received, a great deal of signal processing is imposed. In particular, when the terminal station is a movable station that is driven by a battery, there is a problem that the battery is wasted.

  In order to alleviate this problem, an operation method is generally known in which a frame interval to be received is thinned out by negotiation between a base station and a terminal station, instead of receiving a control signal field in every MAC frame. .

  However, even when the frame interval to be received is thinned out, the same reception as in the case of transmitting and receiving information is necessary in the frame period to be received, and the burden on the terminal station is not reduced so much.

  An object of the present invention is to reduce a burden on a base station or a terminal station when a control signal is transmitted from the base station to the terminal station in this type of wireless communication system.

In the present invention, when information transmission is performed between a base station and a terminal station using a multicarrier signal according to the OFDM modulation scheme, a control signal addressed to the terminal station transmitted from the base station is transmitted to the multicarrier signal. Transmission is performed using one subcarrier that occupies the bands of a plurality of adjacent subcarriers on the frequency centered on the DC subcarrier in the band .

According to such invention, when receiving only a portion of the control signal at the terminal station, when receiving only the bands of a plurality of adjacent subcarriers on a frequency around the DC sub-carrier in the band of the multicarrier signal Get better.

According to the present invention, when wireless communication is performed between a base station and a terminal station using an OFDM modulation communication method, when only a control signal is received at the terminal station, some subcarriers in the multicarrier signal are received. It is only necessary to receive the carrier band . Therefore, when receiving only the control signal, it is not necessary to receive all the subcarriers for the multicarrier signal, which is a heavy burden on the reception processing system, and the low current consumption in the time zone when the terminal station does not transmit / receive information data It is possible to extend the battery driving time. In addition, even when only a plurality of adjacent subcarrier bands on the frequency centered on the DC subcarrier are being received, it is possible to hold the frame timing of the carrier performing transmission / reception of information data, and it is suspended for a while. It is assumed that data transmission and reception can be performed immediately even at a terminal station that meets the requirements.

In this case, the control signal of the terminal station addressed transmitted from the base station using a specific subcarrier, by which a part of the signal for the signal or a call for calling the terminal station, the base This makes it possible to efficiently execute standby processing for calling from a station with low power consumption.

Moreover, multi-carrier signal by using a single subcarrier occupying band of the plurality of sub-carriers around the DC subcarrier in the equivalent baseband system, control for control signals, for transmitting information It becomes possible to transmit with power larger than that of the subcarrier, and it is possible to easily receive at the terminal station.

In addition, the base station transmits a control signal addressed to a terminal station transmitted in a plurality of adjacent subcarrier bands on a frequency centered on the DC subcarrier in synchronization with the frame position for information transmission. On the terminal station side, the frame timing can be captured simply by receiving a specific subcarrier band .

In addition, a control signal addressed to a terminal station that is transmitted from a base station using a plurality of subcarrier bands adjacent on a frequency centered on a DC subcarrier is transmitted in an encoded format that does not require transmission path estimation. Thus, when the terminal station receives a band of a plurality of subcarriers adjacent to each other on a frequency centered on the DC subcarrier, a simple reception process that does not require estimation of the transmission path of the received signal can be executed. It becomes like this.

Further, as a signal transmitted from a base station using a plurality of adjacent subcarrier bands on a frequency centered on a DC subcarrier, the same data is repeatedly transmitted an even number of times. The half of the code is a code in which the polarity of the code constituting the data is inverted, and a signal transmitted using a plurality of adjacent subcarrier bands on the frequency centered on the DC subcarrier is received at the receiving side. The DC offset can be easily removed, and a part of the transmitted control signal can be received with high accuracy.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  First, a configuration example of the wireless communication system of this example will be described with reference to FIG. Here, one base station 1 is connected to an external network 2 connected by wire, and the base station 1 is configured to perform wireless communication with a plurality of terminal stations (mobile stations) 3 and 4. Although only two terminal stations are shown here, it is possible to prepare a larger number of terminal stations. Each of the terminal stations 3 and 4 is configured to perform wireless communication with the base station 1 in principle. As a method for performing wireless communication, the OFDM modulation method using a multicarrier signal described in the section of the prior art is applied, and here, a wireless communication method called HiSWANa is basically used.

  The configuration of the base station will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration of the transmission unit 100 of the base station. In the base station, digital signals for voice signals and data communication are converted into an appropriate digital data string by a data input / output processing unit (not shown), and the output is input to the transmission data processing unit 110. Here, if necessary, a frame or slot structure for receiving communication control data to be transmitted to a terminal station which is a wireless communication partner (not shown) from the control unit 101 and transmitting the data in a wireless section after multiplexing it appropriately. Is output.

  The output of the transmission data processing unit 110 is input to the CRC adding unit 112, and is added with redundancy for error detection on the receiving side. The output of the CRC adding unit 112 is input to the encryptor 113 and is output after being encrypted. The output of the encryptor 113 is input to a scrambler 114, which is subjected to a scramble process that becomes pseudo-random according to a predetermined algorithm and is output. The output of the scrambler 114 is input to the encoder 115, subjected to error correction encoding, and output. As the encoding here, various types of encoding such as convolutional encoding, turbo encoding, Reed-Solomon encoding, or concatenated encoding using a combination of a plurality of encodings can be applied.

  The output of the encoder 115 is input to the interleaver 116, and is subjected to interleaving for rearranging the encoded bit string according to a specific rule so that a burst error can be converted into a random error by performing a reverse operation on the receiving side. Is done. The output of the interleaver 116 is input to the modulator 117, mapped to the signal point at the time of transmission, and an in-phase component (I component) and a quadrature component (Q component) are output. The output of each component is input to a complex IFFT (Inverse Fast Fourier Transform) unit 118, and subjected to OFDM modulation by performing an inverse Fast Fourier Transform process, and then output.

  The OFDM-modulated signal is input to the adder 119, but is usually output as it is without being performed here. The output is input to the time waveform shaping unit 120, for example, provided with a guard time by adding a cycle prefix, and subjected to a windowing process that smoothes the rise and fall of the OFDM modulation symbol and is output. The output is input to the DA converter 121, converted from a digital waveform to an analog waveform, and output. The output is input to the RF transmitter 122. In this RF transmitter 122, filtering, vector modulation by I and Q components, frequency conversion to an appropriate transmission frequency channel, transmission power control, amplification, etc. are performed and output.

  An output signal from the RF transmitter 122 is input as a transmission signal from the base station transmitter 100 to an antenna duplexer (not shown), and an output from the antenna duplexer is input to an antenna (not shown), and finally the antenna Transmitted as electromagnetic waves. This transmission signal is received by the terminal station that is the counterpart of the wireless communication.

  The description of the transmission system so far is normal transmission processing. However, when it is necessary to transmit specific control data addressed to the terminal station from the base station, the base station transmission unit 100 performs the following operation. Do. That is, when the control unit 101 recognizes that there is specific control data addressed to the terminal station, the control unit 101 sends the specific control data addressed to the terminal station to the terminal station control signal waveform generation unit 103 via the transmission system control signal line 102. The terminal station control signal waveform creation unit 103 creates a signal waveform corresponding to the received data. The created signal waveform is input to the adder 119, added with the signal from the complex IFFT unit 118, and output. The subsequent processing is the same as in the case of the normal transmission signal described above.

  In addition, when the position where the signal waveform of specific control data is added by the adder 119 is a position that overlaps the OFDM modulated wave created by the complex IFFT unit 118, the OFDM modulated wave at the overlapping position is invalid. Make it data. That is, via the transmission system control signal line 102, the bit sequence created by the transmission data creation unit 111 is instructed to fill the portion of data transmitted by the subcarrier with nulls, and the transmission data creation unit 401 performs the processing. . From CRC adding section 112 to complex IFFT section 118, assuming that there is no data for that portion, the same processing as usual is performed. Then, the adder 119 adds the signal waveform created by the terminal station control signal waveform creation unit 103 to the portion without the data, and performs transmission processing.

  The base station configured in this way is also configured to transmit a control signal to the terminal station, and a specific control signal (generated by the control signal waveform generating unit 103) is included in the control signal. The control signal is transmitted separately from the OFDM-modulated multicarrier signal. Here, an outline of the arrangement of specific control signals in this example will be described. FIG. 3 is a diagram showing an example of carrier arrangement in the wireless communication system of this example.

  Here, information communication carriers C1, C2, C3, C4,... Are arranged at intervals of 20 MHz (5.17 GHz, 5, 19 GHz, 5, 21 GHz,...), And each information communication carrier is a multi-carrier. An OFDM modulated signal as a signal is transmitted. Up to this point, the frequency arrangement shown in FIG. 29 is the same as that of the conventional example. However, in this example, a narrow band control signal carrier is located at the guard band of the information communication carrier arranged every 20 MHz. C11, C12, C13, ... are arranged. This narrow-band control signal carrier is located at a distance of 10 MHz from the center frequency of the information communication carrier and is located at the center of the guard band. Using this narrowband control signal carrier, a part of the control signal addressed to the terminal station is transmitted from the base station.

  As shown in FIG. 3, by arranging narrow band carriers, for example, in order to receive a narrow band carrier at a terminal station, a frequency synthesizer that determines a reception channel of the terminal station is conventionally used. In the case of this example, if the configuration is changed in 10 MHz steps, the narrow band carrier can be received. A specific configuration of the terminal station will be described later. The signal bandwidth of the narrow band carrier is preferably an integer fraction of the symbol rate or sample rate of the information communication carrier. The band in which the narrow band carrier is arranged is a frequency band corresponding to a guard band, and does not hinder communication in other bands as long as there is no power leakage to the adjacent band.

  The signal transmitted from the base station by the narrow band carrier is frame-synchronized with the signal transmitted by the information communication carrier. That is, FIG. 4 shows the transmission format of the control signal in the wireless communication system of this example. The control signal Db transmitted by the base station using the narrowband carrier is the frame of the signal Da transmitted by the information communication carrier. It is transmitted according to the transmission start time of the MAC frame, which is a cycle. As described with reference to FIG. 31 in the conventional example, the MAC frame is a transmission / reception unit that is periodically set every certain time (here, 2 msec), and is the information communication carrier shown in FIG. The basic configuration of the transmitted signal Da is the same as that of the conventional signal shown in FIG.

  In the first half of each MAC frame, a downlink channel signal transmitted from the base station to each terminal station is transmitted using the information communication carrier, and the second half of the MAC frame is an uplink channel from each terminal station to the base station. This is the timing at which is sent. The transmission of the control signal Db from the base station to the terminal station using the narrow band carrier is performed within the signal transmission period of the downlink channel in the MAC frame. Here, as shown in FIG. 4, the transmission of the narrowband carrier is started from the beginning of one unit of the MAC frame, and the transmission of the narrowband carrier is ended before the downlink burst payload in the frame is completed.

  By transmitting the narrowband signal from the base station in this way, the terminal station recognizes the break of the MAC frame of the information communication carrier in the base station even when only the narrowband signal is received. If it becomes clear that the information obtained by receiving the narrowband signal should start reception on the information communication carrier or start transmission on the information communication carrier, immediately It becomes possible to recognize the break of the MAC frame and perform a desired process.

  As a part of the control signal transmitted from the base station to the terminal station using the narrow band carrier, for example, a call signal for calling the terminal station individually or for each group is used. By receiving this signal at the terminal station, the terminal station can determine that there is a call from the base station. A specific example of processing using this call signal will be described later. In the case of this example, even if the call signal of the terminal station is transmitted from the base station using the narrowband carrier, the control signal transmission section in the MAC frame is used using the information communication carrier. Also, the call signal of the terminal station is transmitted in a configuration as determined in advance by the system. However, transmission of a part of the call signal of the terminal station using the information communication carrier may be omitted.

  When transmitting using narrowband carriers as described so far, the base station transmits each separate signal using a plurality of narrowband carriers arranged in each guard band as shown in FIG. In this way, for example, a terminal station (or group) assigned to one narrowband carrier may be determined in advance.

  Alternatively, the same signal may be transmitted using a plurality of narrowband carriers. This is particularly effective when the transmission path is affected by frequency selective fading due to multipath with delay, and a signal transmitted by a narrowband carrier disposed below the information communication carrier is fading. Even if it falls in the valley, it is possible to obtain a frequency diversity effect that the signal transmitted by the narrow band carrier arranged above the information communication carrier does not fall in the fading valley. In such a case, the terminal station can receive the better one of the narrow band carrier arranged above and the narrow band carrier arranged below.

  3 and 4, the narrowband carrier is arranged at the center of the guard band of the OFDM modulation signal, but it may not be at the center of the guard band. For example, as shown in FIG. 5, a narrowband carrier for a control signal is adjacent to the subcarrier of the highest or lowest frequency in the OFDM modulated signal C1 in which a plurality of subcarriers are arranged at a constant frequency interval. C11 'may be arranged. In this case, the frequency interval between the narrowband carrier C11 ′ for the control signal and the adjacent subcarrier may be set equal to the frequency interval of the subcarrier of the OFDM modulated signal.

  As shown in FIG. 5, by arranging narrow band carriers for control signals, the process of placing narrow band carriers on the base station side can be performed simultaneously with other signals within the block that generates the OFDM modulated signal. become. That is, in this case, the transmission data processing unit 111 to the modulator 117 simultaneously perform the transmission processing for the control signal for the narrowband carrier, and the complex IFFT unit 118 adds one subcarrier to the OFDM modulated signal. Should be generated. When the transmission process is performed with the carrier arrangement of FIG. 5, the terminal station control signal waveform creation unit 103 and the adder 119 are not necessary, and the configuration of the transmission system of the base station is simplified accordingly.

  Further, in addition to the center of the guard band and the position adjacent to the subcarriers constituting the OFDM modulated signal, a narrowband carrier for the control signal may be arranged for wireless transmission.

  Next, the configuration of the terminal station used in the wireless communication system of this example will be described. FIG. 6 is a diagram illustrating an example of the configuration of the terminal station apparatus 200 in the wireless communication system of this example. The terminal station device 200 is configured as a portable mobile station using, for example, a built-in battery as a power source.

  First, the configuration of the transmission system of the terminal station device 200 will be described. In the case of voice communication, the output of the voice coder is input to the data input / output processing unit 201 in the case of data communication connected to a computer, and converted into an appropriate digital data string. The output is input to the transmission data processing unit 211. If necessary, the control unit 202 receives communication control data to be transmitted to another OFDM wireless device (base station) that is a partner of wireless communication (not shown), After plexing, a frame or slot structure for transmission in the radio section is formed and output.

  The output of the transmission data processing unit 211 is input to the CRC adding unit 212, and is added with redundancy for error detection on the receiving side. The output is input to the encryptor 213, encrypted, and output. The output is input to the scrambler 214, and is subjected to a scramble process that becomes pseudo-random according to a predetermined algorithm and is output. The output is input to the encoder 215, subjected to error correction encoding and output. Various types of encoding such as convolutional encoding, turbo encoding, Reed-Solomon encoding, or concatenated encoding using a combination of a plurality of encodings can be applied.

  The output of the encoder 215 is input to the interleaver 216 and subjected to interleaving for rearranging the encoded bit string according to a specific rule so that a burst error can be converted into a random error by performing a reverse operation on the receiving side. Is done. The output is input to the modulator 217, mapped to a signal point at the time of transmission, and an in-phase component (I component) and a quadrature component (Q component) are output. The output of each component is input to the complex IFFT unit 218, and is subjected to OFDM modulation by performing inverse fast Fourier transform processing, and then output. The output is input to the time waveform shaping unit 219, for example, provided with a guard time by adding a cycle prefix, and subjected to a windowing process that smoothes the rise and fall of the OFDM modulation symbol and is output.

  The output of the time waveform shaping unit 219 is input to the DA converter 220, converted from a digital waveform to an analog waveform, and output. The output of the DA converter 220 is input to the RF transmitter 221. In this RF transmitter 221, filtering, vector modulation by I and Q components, frequency conversion to an appropriate transmission frequency channel, transmission power control, amplification, etc. are performed and output. An output signal from the RF transmitter 221 is input to the antenna duplexer 222, an output from the antenna duplexer 222 is input to the antenna 223, and finally transmitted from the antenna 223 as an electromagnetic wave. This transmission signal is received by the base station that is the counterpart of the wireless communication. The antenna duplexer 222 is for separating a transmission signal and a reception signal, and an antenna switch or a duplexer is generally used.

  Next, the configuration of the reception system of the terminal station will be described. First, the processing configuration of the reception system when the terminal station 200 receives normal traffic on the information communication carrier will be described. Here, the signal received by the terminal station 200 is transmitted by the base station that is the counterpart of the wireless communication.

  A signal transmitted from the base station is received by the antenna 223 as an electromagnetic wave. The signal is separated from the transmission signal from the terminal station by the antenna duplexer 222 and then input to the RF receiver 230. In the RF receiver 230, the received signal is amplified by the RF amplifier 231, and the amplified output is mixed in the sine wave generated by the frequency synthesizer 233 with the quadrature detector 232, so that the I component and the Q having a center frequency of DC and Q Only the band of a specific signal is filtered by the first and second filters 234 and 235. The first filter 234 is a filter for extracting a specific control signal transmitted by a narrowband carrier or a specific subcarrier, which will be described later. The first filter 234 has a narrower passband width than the second filter 235. is there. The second filter 235 is a filter for extracting a signal of normal traffic, and is a filter for extracting a signal of one unit transmission channel subjected to OFDM modulation.

  The output of the first filter 234 is input to the first AD converter 241 and converted from an analog waveform to a digital waveform. The output of the first AD converter 241 is input to the control signal receiver 242. The control signal receiver 242 detects a control signal from the base station, and transmits the detection information to the control unit 202 via a control signal line (call notification signal line described later) 205. The control signal detected by the control signal receiver 242 includes, for example, a signal indicating that the base station calls the own station or a group to which the own station belongs.

  The output of the second filter 235 is input to the second AD converter 251, converted from an analog waveform to a digital waveform, and output. This output may be oversampled, for example, and a means for filtering only a desired signal band by a digital filter or the like may be added. The output of the second AD converter 251 is input to the synchronization circuit 252 and output after being subjected to frame synchronization, frequency error correction, and the like. When searching for a possible communication partner immediately after power-on or the like, the synchronization circuit 252 is configured to detect a synchronization signal or perform initial synchronization.

  The output of the synchronization circuit 252 is input to the time waveform shaping unit 253, and is output after being subjected to time waveform shaping that removes a guard time by adding a cycle prefix, for example. This output is input to a complex FFT (Fast Fourier Transform) unit 254, and subjected to OFDM demodulation by performing Fast Fourier Transform processing, and then output. This demodulated output is input to the equalizer 255. The equalizer 255 performs transmission path estimation and equalization based on the estimation result. In some cases, information of the synchronization circuit 254 is also input to the equalizer 255 and used for transmission path estimation and the like. The output of the equalizer 255 is input to the demodulator 256, where signal point determination is performed and a received bit estimation value is output. The output is input to the deinterleaver 257, and is subjected to deinterleaving for rearranging the encoded bit string in accordance with a specific rule. The output is input to the decoder 258, and the error correction code applied on the transmission side is decoded and output.

  The output of the decoder 258 is input to a descrambler 259, and descrambled, which is the inverse scramble conversion performed on the transmission side, is performed and output. The output is input to the descrambler 260, and the encryption applied on the transmission side is released and output. The output is input to the CRC check unit 261, and the data from which the CRC code has been removed and the CRC check result of the received block are output. The output is input to the received data processing unit 262. If it is determined that there is no error as a result of the CRC check of the received block, the frame structure or slot structure applied for transmission in the wireless section is removed and output. The output is input to the data input / output processing unit 201. In the case of voice communication, an audio signal is converted into a data signal in the case of data communication connected to a computer and output.

  When communication control data from the base station is included in the received data, the received data processing unit 262 extracts and outputs that portion, and the output is input to the control unit 202 via the reception system control line 204. The control unit 202 interprets the received control data and controls the operation of each unit of the terminal station 200 according to the instruction.

  If the ARQ method is adopted, the reception data processing unit 262 operates as follows. That is, if the input signal from the CRC check unit 261 includes information that the received block does not contain an error, the received block is output to the received data processing unit 262 as described above, while the received block is received. The fact that no error is included in the block is output to the control unit 202 via the reception system control line 204, and the control unit 202 that has received this outputs a transmission system control line so as to transmit an ACK signal to the base station. The transmission data processing unit 211 instructs the transmission data processing unit 211 via 203, and the transmission data processing unit 211 multiplexes the transmission ACK signal into the transmission data. It is transmitted wirelessly to the station.

  Conversely, if the input signal from the CRC check unit 261 includes information that the received block contains an error, the received block as described above is not output to the received data processing unit 262. The fact that an error is included in the reception block is output to the control unit 202 via the reception system control line 204, and the control unit 202 that has received this outputs the transmission system control line so as to transmit the NAK signal to the base station. The transmission data processing unit 211 instructs the transmission data processing unit 211 via 203, and the transmission data processing unit 211 multiplexes the transmission NAK signal into the transmission data. Sent to the station. The base station receiving this retransmits the block to which the NAK signal has been sent.

  In the case of stream communication such as voice communication in which retransmission such as ARQ is not used, the reception data processing unit 262 operates as follows. That is, if the input signal from the CRC check unit 261 includes information that the received block does not contain an error, the received block is output to the received data processing unit 266 as described above. On the other hand, if the input signal from the CRC check unit 261 includes information that the received block contains an error, the received data processing unit 262 discards the received block and treats it as an erasure. Processing such as complementing using the previous reception block is performed.

  Each part of the transmission system is connected to the control unit 202 via the transmission system control line 203, and the control unit 202 controls the on / off of the transmission system, the operation control / status monitoring of the RF transmitter 221, and the transmission via the control unit 202. It controls and monitors the operation of various transmission systems such as fine adjustment of timing, change of coding method and signal point mapping method, and retransmission control described above. Each part of the reception system is connected to the control unit 202 via the reception system control line 204, and the control unit 202 controls the ON / OFF of the reception system, the operation control / status monitoring of the RF receiver 230, and the reception via this. It controls and monitors the operation of various receiving systems such as fine adjustment of timing, change of decoding method and signal point demapping method, and retransmission control described above.

  Next, the operation at the time of standby of the terminal station 200 in the communication system of this example will be described with reference to FIG. The standby here is a state in which information communication with the base station is not performed but a response is made when called from the base station. In the following description, it is assumed that the control signal transmitted by the narrowband carrier is specifically signal data for calling the terminal station or a part of signal data for the call.

  First, after the power is turned on (step S11), the terminal station 200 associates with the base station and enters a call code or data corresponding thereto before entering a standby operation (step S11). Step S12). It is also agreed that the frame interval to be received is negotiated by negotiation between the base station and the terminal station, and the time interval and the reference time are also set in the control unit 202 of the terminal station 200.

  When the control signal transmitted by the narrow band carrier is received after the setting up to this point, only the basic frequency oscillator in the terminal station and the counter in the control unit 202 always operate, and In this state, the timer set for measuring the timing to be received is started and all other parts are turned off by the control from the control unit 202 via the reception control signal line 204. The sleep state is set (step S13).

  When the time to be received approaches in this sleep state, the control unit 202 takes into account the frequency error of the fundamental frequency oscillator and the rise time after power-on of the terminal station receiver. Control is performed so as to turn on the power of the part necessary for reception of the standby signal via the control signal line 204 of the reception system slightly earlier than the expected time.

  Then, when it is time to receive a control signal transmitted by a narrow band carrier, only the first filter 234, the first AD converter 241 and the control signal receiver 242 start operation and are transmitted from the base station. Among the received signals, the control signal band transmitted by the narrow band carrier is received (step S14). At this time, the RF receiver 230 except for the second filter 235, the first AD converter 241 and the control signal receiver 242 are only turned on, and the other receiving units in the terminal station are not turned on.

  Specifically, the received signal is band-limited by the first filter 234 so that only the first bandwidth corresponding to the bandwidth of the narrow-band carrier passes, and the output is input to the first AD converter 241. The The analog reception signal whose band is limited in this manner is sampled by the first AD converter 241 at a frequency of 1 or more times, preferably 2 or more times the frequency of the first bandwidth, and converted into a digital signal. It is converted and output. The output digital signal is input to a control signal receiver 242 that detects a call signal from the base station, and determines whether the call group including itself (the own station) or itself is not called.

  When the control signal receiver 242 determines that the user or the call group including the user is being called, the control signal receiver 242 notifies the control unit 202 that the call is being made via the call notification signal line 205, and The process proceeds to the case where the station is called (step S15). For example, the control unit 202 can receive a control signal including a normal paging signal, which is originally prepared in the system and is transmitted at the beginning of the OFDM modulation signal of the next MAC frame. The receiving system is operated via the control unit 204. In this case, when the carrier arrangement is the setting shown in FIG. 3, for example, the reception frequency changes at least 10 MHz because the reception shifts from the reception of the narrowband carrier to the reception of the OFDM modulated signal. Then, it judges the frequency and time slot assigned to its own station indicated by the control signal arranged in the received MCA frame, and transmits information using the indicated frequency and slot. This is performed (step S16).

  If it is determined that the local station (or the group to which the local station belongs) has not been called in the reception of the narrow band carrier in step S14, the process returns to the sleep state in step S13 until the next narrow band carrier is received. stand by. Then, it is determined that the local station (or the group to which the local station belongs) has been called by the reception of the narrow band carrier in step S14, and the control signal including the regular calling signal in step S15 is received. When the time slot is not allocated to the station, it is determined that another terminal in the call group including the own station has been called or the reception determination of the call signal is wrong, and the control unit 202 While resetting the counter, the power supply other than the basic frequency oscillator (not shown) and the counter inside the control unit 202 is controlled to be turned off via the reception system control signal line 204, and the terminal station 200 returns to the standby sleep state in step S13. .

  Note that in the example of FIG. 7 showing the state transition from the standby state, the process moves to the transmission / reception of traffic only by the reception process of the control signal transmitted from the base station, but the process moves to the transmission / reception of traffic at the terminal station. The present invention is also applicable to a system that needs to transmit a signal for access from the terminal station to the base station side. FIG. 8 is a diagram showing an example of state transition in this case.

  In the case of the example in FIG. 8, when it is determined in step S14 that a narrowband carrier has been received and a call to the own station (or a group to which the own station belongs) is determined, the process proceeds to step S17, and the control unit 202 The power of the transmission system is turned on via the control signal line 203 and transmitted by the uplink random access channel in the MAC frame, and the control unit 504 operates the reception system via the reception system control signal line 204 at an appropriate timing. Then, turn on the power of all receiving systems except the first filter 234, the first AD converter 241 and the control signal receiver 242, and receive the downstream response from the base station in the MAC frame, Based on the response, whether the call was actually addressed to the own station, whether the call group including the own station was called and the own station was being called, or the call group including the own station was called In fact, it was confirmed that the local station was not called, or that it was not a call signal for the calling group addressed to or including the local station in the first place. In such a case, control is performed so as to enter a normal call connection start procedure and to move to the transmission / reception of traffic in step S18.

  As a result of checking using the random access channel and the response as described above, it is found that the user has not been called. The control unit 202 resets the internal counter and controls the power supply other than the basic frequency oscillator (not shown) and the counter inside the control unit 202 to be turned off via the reception system control signal line 204, and the terminal The station 200 returns to the standby sleep state in step S13. When the control signal receiver 242 determines that the own station or the call group including the own station is not called, the control signal receiver 242 notifies the control unit 202 that the call is not called via the call notification signal line 205. . Upon receiving the notification, the control unit 202 resets the internal counter and controls the power supply other than the basic frequency oscillator (not shown) and the counter inside the control unit 202 to be turned off via the reception system control signal line 204, Returns to the standby sleep state in step S13. The other processing of the state transition diagram of FIG. 8 is the same as the state transition processing shown in FIG.

  Next, an example of a signal system of a control signal transmitted / received by a narrow band carrier will be described. In the case of this example, the control signal transmitted / received by the narrowband carrier adopts a signal of a modulation scheme different from the signal transmitted as the OFDM modulation signal in the MAC frame. The received signal can be easily detected. Here, it is assumed that a part of the control signal is transmitted by a narrowband carrier, and is a process applied when only information of about several bits per MAC frame is transmitted, for example.

  First, FIG. 9 shows a part of the control signal transmission configuration on the base station side. The base station may divide the currently accommodated terminal stations into several groups, and may call each group in a time division manner. In this case, the terminal station knows in advance by negotiation which timing the call signal addressed to itself is transmitted, and intermittently receives only at that timing.

  The base station picks up a terminal station to be actually called from a group of terminal stations to be called at the timing of each MAC frame. This pick-up operation is performed by the calling terminal determination means 131 shown in FIG. This result is sent to the transmission bit string determining means 132, and a bit string previously associated with the terminal station (which may be a plurality of terminals) to be called is generated. This bit string is sent to the M-ary signal generating means 133 and converted into an M-ary code corresponding to the input bit string.

  11A to 11H are diagrams illustrating examples of M-ary codes. Here, an example in which 3-bit data is converted into an 8-symbol M-ary code is shown. This is an encoding method in which vectors orthogonal to each other are assigned to each data, and a simple correlation is performed on the receiving side. It is a code having a feature that the transmitted data can be detected by detection.

  The signal generated by the M-ary signal generation unit 133 in this way is multiplied by the pseudo-random sequence generated by the PN (Pseudo Noise) sequence generation unit 135 by the multiplier 134 (polarity inversion). Lightly spread spectrum. In the example of FIG. 9, a case where the signal is spread seven times is shown, and a total of 56 symbols are finally output. For example, in the case of a frequency arrangement in which a narrow band carrier is arranged at the center of the guard band shown in FIG. 3, the output symbol is processed within a base station at a location 10 MHz away from the OFDM modulation signal. And sent. Further, for example, when a narrowband carrier is arranged adjacent to the OFDM modulation signal as shown in FIG. 5, the symbols generated in the configuration of FIG. 9R> 9 are complex IFFT units for transmission processing in the base station. And multiplexed with the signal of the information communication carrier and transmitted.

  Next, a configuration in which the terminal station side receives the signal generated in the base station and transmitted by the narrowband carrier will be described with reference to FIG. FIG. 10 is a diagram illustrating a part of the reception configuration in the terminal station 200. Specifically, the internal configuration of the control signal receiver 242 in FIG. 6 is shown.

  The first AD converter 241 disposed in the previous stage of the control signal receiver 242 illustrated in FIG. 6 is operated at a symbol rate that is twice the symbol rate of the narrowband signal, for example, and the first AD converter 241 The output is passed to the input terminal 270 shown in FIG. 10 after the signal band is limited by a digital filter (LPF) (not shown). This signal is subjected to signal despreading processing and decoding processing while correcting the reception timing by DLL (Delayed Lock Loop).

  The specific signal processing will be described with reference to FIG. 10. The input signal is divided into three systems, each of which is shifted by one sample time using the delay circuits 271 and 272, and the signal of each system is determined. The symbol rates are doubled by the conversion circuits 273, 274, and 275. Then, a PN sequence similar to the PN sequence used at the time of spectrum spread on the transmission side is generated by the PN sequence generation means 281, and the signals of each system are multiplied by the PN sequence by multipliers 276, 277 and 278, and Perform diffusion processing. Of the three systems of signals obtained by the despreading process, the signal with the middle timing is the decoding target, and the other two signals are subtracted by the subtractor 282 and then sent to a reception timing control means (not shown). Sent. The reception timing control means performs timing control so that the reception timing does not drift by the same control process as the reception timing control process using a normal DLL.

  On the other hand, the signal of the system subjected to decoding processing is sent to the reception bit string estimation means 279, and the M-ary encoded signal by correlation detection is subjected to MLSE (Maximum Likelihood Sequence Estimator) processing and received. Output the estimated value of the bit string. This received bit string estimated value is sent to the calling terminal estimating means 280. The calling terminal estimating means 280 determines whether or not the own terminal station is called at the timing, and performs processing according to the determination result.

  In this way, by generating a control signal with the configuration of FIG. 9 and transmitting it from a base station using a narrow band carrier or the like, it is not necessary to estimate a transmission path as a reception configuration on the terminal station side. As described above, it is possible not only to decode a signal transmitted by simple processing, but also to provide communication having high noise resistance characteristics. Also, the reception timing control can be realized only with simple processing, which contributes to further reduction of current consumption in the terminal station.

  In the control signal transmission processing configuration shown in FIG. 9 and FIG. 10, the M-ary code is used to enable transmission with a simple configuration that does not require channel estimation such as channel response. Instead of M-ary modulation, a pilot symbol which is a known symbol may be added, and then spread spectrum processing may be performed for transmission. FIG. 12 is a diagram illustrating an example of the encoding process on the transmission side (base station) when this pilot symbol is added. In this example, the output of the calling terminal determining means 131 is sent to the transmission bit string determining means 132, a bit string previously associated with the terminal station desired to be called is generated, the generated bit string is sent to the pilot adding means 136, and a known symbol is used. A certain pilot symbol is added.

  The signal to which the pilot symbol is added by the pilot adding means 136 is multiplied by the pseudo-random sequence generated by the PN sequence generating means 135 by the multiplier 134 and spread spectrum, and the spread output is obtained in the case of the example of FIG. In the same manner as described above, processing for wireless transmission using a narrow band carrier or a specific subcarrier is performed. When transmitting from the base station with the configuration shown in FIG. 12, the reception configuration at the terminal station is the same as the configuration shown in FIG. 10, except that the internal processing of the received bit string estimation means is different. The decryption process is possible.

  Further, as a transmission processing configuration of a control signal such as a calling signal, an encoding format that can easily remove a DC offset may be adopted. That is, for example, as shown in FIG. 13A, when transmitting signal data for calling a mobile station or a part of signal data for calling using a subcarrier, the same data is repeated an even number of times. The half of the even number is transmitted with the data polarity reversed. In this example, assuming that the signal data for calling the mobile station or a part of the signal data for calling is composed of 6 bits such as “111010”, BPSK is used as data modulation. Assume that data is mapped to -1 and +1 as in modulation. By repeating the transmission evenly while inverting the polarity in this way, even if a DC offset occurs in the waveform obtained by the receiver in the terminal station, for example, as shown in FIG. By using the received signal, as shown in FIG. 13C, the cross-correlation waveform can be easily made a waveform from which the DC offset is removed.

  If transmission of an even number of times is not performed while inverting the polarity of half of the data, even if the same data is repeatedly transmitted from the base station a plurality of times as shown in FIG. 14A, for example, reception at the terminal station When the DC offset shown in FIG. 14B occurs in the waveform, the DC offset remains as it is in the cross-correlation waveform on the receiving side shown in FIG. 14C. However, by performing transmission processing as shown in FIG. Such a problem can be easily avoided.

  The number of bits required for the above-described M-ary encoding is limited (for example, when the information bits are n bits, 2 ^ n bits are required for transmission by M-ary encoding). If the number of bits cannot be transmitted in operation, it is preferable to perform transmission processing as shown in FIG. For example, it is assumed that the signal data for calling the mobile station limited by the usable DC subcarrier band or the symbol length of a part of the signal data for the calling is 3.2 μsec. At this time, it is assumed that the time during which this data can be transmitted was 44 μsec.

  Under this assumption, the signal data for calling the terminal station or a part of the signal data for the call is 44 ÷ 3.2 = 13.75, and only 13 symbols are transmitted. Not very suitable for encoding. In such a case, the signal data for calling the mobile station, or a part of the signal data for the call, has a 6-bit length, which is repeatedly transmitted a plurality of times, in this case, twice. To do. At this time, the symbol length necessary for transmission is 38.4 μsec, and transmission is not performed for the remaining time.

  In the example shown in FIG. 13, an example has been described in which a bit string with the polarity reversed is transmitted after the entire bit string is transmitted once as repeated transmission. However, for example, an inverted bit is set every other bit. For example, “111010” may be converted to “101010011001”.

  Here, an example of reception processing at the terminal station when the control signal is transmitted from the base station as shown in FIG. 13 will be described with reference to FIG. FIG. 15 is a diagram showing a configuration example of the control signal receiver 242 in the terminal station 200 shown in FIG. The example of FIG. 15 is an example of a configuration for receiving a control signal using simple cross-correlation detection. Here, the control signal receiver 242 includes a complex cross-correlation calculator 243, a reference signal generator 244, a comparator 245, and a correlation threshold setting unit 246.

  First, when a code for distinguishing the own station or a call group including the own station is transmitted to the reference signal generator 244 by the control from the control unit 202 via the reception system control signal line 204. Bit string is set. From this bit string, the reference signal generator 244 generates a baseband waveform when transmitted in the band of at least one subcarrier in the vicinity of the DC subcarrier in the equivalent baseband system, and sends the reference signal to the complex cross-correlation calculator 243. Enter as.

  On the other hand, the correlation threshold value setter 246 determines that the calculated cross-correlation value is that of itself or a group including itself is called by control from the control unit 202 via the reception system control signal line 204. A threshold value is determined and input to the comparator 245 as the threshold value. The received digital waveform output from the first AD converter 241 is input to the complex cross-correlation calculator 243 where the cross-correlation with the reference signal input from the correlation threshold setting unit 244 is calculated and the value is output. Is done. The output is input to the comparator 245, where it is compared with the threshold set by the correlation threshold setting unit 245, and if it is determined that the correlation is higher than the threshold, it is called via the call notification signal line 205. To the control unit 202. When it is determined that the correlation is lower than the threshold value, the control unit 202 is notified that the call is not made via the call notification signal line 205. Note that the correlation threshold setting unit 246 may be dynamically controlled by the control unit 202 in accordance with the state of the radio propagation path, the state of interference, and the like.

  As described above, by using a method for obtaining a complex correlation as the control signal receiver 242, it is possible to detect a call signal with a relatively simple configuration and low power consumption.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  Also in the case of the present embodiment, as in the case of the first embodiment described above, an OFDM modulated signal is wirelessly transmitted between the base station and the terminal station, and the basic information transmission is performed. The configuration is the same as that described in the first embodiment. In this example, in the first embodiment, a narrow band carrier or the like is prepared in order to transmit a specific control signal such as a call signal and is transmitted in a guard band. A specific control signal such as a paging signal is transmitted using a specific subcarrier.

  FIG. 16 is a diagram showing an arrangement of subcarriers of one transmission channel in this example. A plurality of subcarriers are arranged at regular frequency intervals to form an OFDM modulated signal. For example, subcarrier groups are arranged every 312.5 kHz, and a total of 53 subcarriers are prepared. In this example, the subcarrier SC1 centering on DC in the equivalent baseband system, which is the center of the 53 subcarriers (corresponding to the subcarrier having the center frequency f0 in the carrier frequency band), and its center A total of two subcarriers of subcarrier SC2 adjacent to the subcarrier SC1 (adjacent to the upper side in this case) are used for transmission of a specific control signal such as a paging signal in a specific section in each MAC frame. Constitute.

  FIG. 17 is a diagram illustrating a configuration example of one MAC frame in this example. Here, a transmission / reception unit called a MAC frame with a period of 2 msec is defined, and is roughly composed of four parts: a broadcast burst, a downlink phase, an uplink phase, and a contention phase. FIG. 17 shows only the broadcast burst and the downlink phase.

  A broadcast burst is a BCH for broadcasting broadcast preamble, base station information, etc., an FCH for notifying each terminal station of traffic channel allocation in the same frame, and a response to an RCH used for a call from the terminal station. ACH etc. for which is performed are prepared. In the case of this example, the two subcarriers SC1 and SC2 shown in FIG. 16 described above are used for transmission of a specific control signal in the section of the broadcast preamble, BCH and FCH in this broadcast burst.

  In each MAC frame, the two subcarriers SC1 and SC2 of the ACH section of the broadcast burst and the section of the downlink phase and the uplink phase are not used for transmission of a specific control signal. In a section not used for transmission of this specific control signal, the two subcarriers SC1 and SC2 may be null carriers in which no information is transmitted, or may be used for some information transmission. Further, only the subcarrier SC1 with the center frequency f0 may be used as a null carrier in the section after the ACH, and the adjacent subcarrier SC2 may be used for information transmission in the section after the ACH.

  As a configuration for radio transmission from the base station with such a subcarrier arrangement, for example, the transmission configuration shown in FIG. 2 described in the first embodiment can be applied, and the two subcarriers SC1 and SC2 can be applied. A specific control signal such as a terminal station calling signal may be arranged in the arranged data. In this case, with respect to signals transmitted using these two subcarriers SC1 and SC2, as in the case already described with reference to FIGS. 9 to 12 of the first embodiment, M-ary encoding or the like is performed. Transmission may be performed after simple encoding capable of simple and low power consumption processing. Further, similarly to the case described with reference to FIGS. 13 to 15, a transmission process in which the same data is repeatedly inverted and transmitted to remove the DC offset may be performed. Or you may make it transmit with the same encoding format as the signal transmitted with another subcarrier.

  Next, a configuration example of a terminal station that receives a signal transmitted from the base station in this way will be described with reference to FIG. The terminal station 200 ′ shown in FIG. 18 has the same configuration as that of the terminal station 200 shown in FIG. The configuration of the receiving system of the terminal station 200 ′ will be described. A radio signal from the base station is received by the antenna 223 and input to the RF receiver 230 ′ via the antenna duplexer 222. In the RF receiver 230 ′, the received signal is amplified by the RF amplifier 231, and the amplified output is mixed in the sine wave generated by the frequency synthesizer 233 with the quadrature detector 232, and an I component having a center frequency of DC and The signal is separated into Q components, and only a signal in a specific band is filtered by the passband variable filter 236.

  The pass band variable filter 236 is a filter whose pass band is variably set under the control of the control unit 202. At the time of normal reception, a wide pass band is set through which all (53 in this case) subcarriers prepared in one transmission band shown in FIG. 16 are passed. Further, at the time of standby reception, a narrow pass band is set through which only the two subcarriers SC1 and SC2 at the center pass.

  The output of the passband variable filter 236 is input to the AD converter 263 and converted from an analog waveform to a digital waveform. The AD converter 263 here is a sampling rate variable AD converter so that it can cope with a variable sampling rate between standby reception and normal reception. This sampling rate is set by control from the control unit 202.

  The output of the AD converter 263 is input to the control signal receiver 264 and the synchronization circuit 252. The control signal receiver 264 detects a control signal from the base station, and transmits the detection information to the control unit 202 via a control signal line (call notification signal line to be described later) 205. As a control signal detected by the control signal receiver 264, for example, there is a signal indicating that the base station is calling the own station or a group to which the own station belongs.

  The signal input to the synchronization circuit 252 is subjected to frame synchronization, frequency error correction, and the like and output. The reception processing system from the synchronization circuit 252 to the reception data processing unit 262 has the same configuration as that of the terminal station 200 shown in FIG. 6, and the output of the reception data processing unit 262 is input to the data input / output processing unit 201, In the case of communication, an audio signal is converted into a data signal and output in the case of data communication connected to a computer.

  Next, the operation at the time of standby of the terminal station 200 ′ in the communication system of this example will be described with reference to FIG. The standby here is a state in which information communication with the base station is not performed but a response is made when called from the base station. In the following description, it is assumed that the control signal transmitted by the narrowband carrier is specifically signal data for calling the terminal station or a part of signal data for the call.

  First, after the terminal station 200 'is turned on (step S11), it associates with the base station and enters a code for calling or data corresponding thereto before entering a standby operation. (Step S12). It is also agreed that the frame interval to be received is negotiated by negotiation between the base station and the terminal station, and the time interval and the reference time are also set in the control unit 202 of the terminal station 200 ′.

  When the control signal transmitted by the narrow band carrier is received after the setting up to this point, only the basic frequency oscillator in the terminal station and the counter in the control unit 202 always operate, and In this state, the timer set for measuring the timing to be received is started and all other parts are turned off by the control from the control unit 202 via the reception control signal line 204. The sleep state is set (step S13).

  When the time to be received approaches in this sleep state, the control unit 202 takes into account the frequency error of the fundamental frequency oscillator and the rise time after power-on of the terminal station receiver. Control is performed so as to turn on the power of the part necessary for reception of the standby signal via the control signal line 204 of the reception system slightly earlier than the expected time.

  When it is time to receive the control signal transmitted by the narrow band carrier, the filter 236 is set to the narrow band, the AD converter 263 is set to the sampling rate for standby reception, and the RF receiver 230 ′ Only the control signal receiver 264 starts operation, and receives only two subcarriers SC1 and SC2 among the signals transmitted from the base station (step S14). As reception timing, only the broadcast preamble, BCH, and FCH sections in each MAC frame are received. At this time, only the power of the RF receiver 230 ', the AD converter 263, and the control signal receiver 264 is turned on, and the other receiving units in the terminal station are not turned on.

  By performing the receiving operation in this way, the call signal from the base station transmitted on the subcarriers SC1 and SC2 is input to the control signal receiver 264, and the call group including itself (the own station) or itself is called Determine if it has not been called.

  When the control signal receiver 264 determines that the user or the call group including the user is being called, the control signal receiver 264 notifies the control unit 202 that the call is being made via the call notification signal line 205, and The process proceeds to the case where the station is called (step S19). Here, the filter 236 is set to a wide band, the AD converter 263 is set to a sampling rate for normal reception, and the reception system from the synchronization circuit 252 to the reception data processing unit 262 is also operated with the power on. It is made possible to receive a control signal including a regular paging signal, which is originally prepared in the system and transmitted at the head part of the OFDM modulation signal of the MAC frame. Then, it judges the frequency and time slot assigned to its own station indicated by the control signal arranged in the received MCA frame, and transmits information using the indicated frequency and slot. It performs (step S20).

  If it is determined that the own station (or the group to which the own station belongs) is not called by receiving only the subcarriers SC1 and SC2 in step S14, the process returns to the sleep state in step S13, and the next subcarrier SC1. , Waits until the reception timing of SC2. Then, the reception of only the subcarriers SC1 and SC2 in step S14 determines that the own station (or the group to which the own station belongs) has been called, and the wideband reception in step S19 determines the time slot allocation for the own station. If not, it is determined that another terminal in the call group including the own station has been called or the reception determination of the call signal is incorrect, and the control unit 202 resets the internal counter and receives the reception signal. The terminal station 200 returns to the standby sleep state in step S13 by controlling the power supply other than the fundamental frequency oscillator (not shown) and the counter inside the control unit 202 to be turned off via the system control signal line 204.

  By configuring the system as shown in the second embodiment and operating the system, it is sufficient to intermittently receive only a specific subcarrier in the vicinity of the center frequency f0 in the carrier frequency band when waiting at the terminal station, Standby reception can be realized with simple processing, which contributes to low power consumption during standby at the terminal station. In this case, the reception frequency itself received by the RF receiver 230 in the terminal station is exactly the same as in normal communication. For example, a reception frequency step such as 20 MHz can be set exactly the same as that of a conventional terminal device. The complexity of the configuration can be avoided.

  In the example of FIG. 19 showing the state transition from the standby state, the process is shifted to the transmission / reception of traffic only by the reception process of the control signal transmitted from the base station. However, in the first embodiment, FIG. As in the case of the state transition example shown in Fig. 2, the narrow band of this example is applied to a system that requires transmission of a signal for access from the terminal station to the base station side before moving to transmission / reception of traffic at the terminal station. It is also possible to apply performing standby signal reception and broadband reception.

  Further, in the subcarrier arrangement of FIG. 16 shown as an example of transmission in the second embodiment, there are two subcarriers SC1 having a center frequency f0 in the carrier frequency band and subcarriers SC2 adjacent to the subcarrier SC1. The terminal station call signal (or a part of the terminal station call signal) is transmitted using one subcarrier, but one or more other specific subcarriers near the carrier center frequency within one transmission band. May be used for transmission of a specific control signal such as a call signal.

  For example, FIG. 20 shows another example of the arrangement of subcarriers. When an OFDM modulated signal is composed of a plurality of subcarriers such as one transmission band of 53, a subband having a center frequency f0 in the carrier frequency band is shown. The terminal station is called by three subcarriers, that is, the carrier SC1, the subcarrier SC2 adjacent to the upper frequency position of the subcarrier SC1, and the subcarrier SC3 adjacent to the lower frequency position of the subcarrier SC1. A specific control signal such as a signal (or a part of the calling signal of the terminal station) is transmitted.

  The broadcast burst and downlink phase in one MAC frame in the case of FIG. 20 are shown in FIG. 21. In this example, the broadcast preamble, BCH, and FCH in this broadcast burst are shown in FIG. The subcarriers SC1, SC2, and SC3 are used for specific control signal transmission. In a section not used for transmission of a specific control signal of each MAC frame, the three subcarriers SC1, SC2, and SC3 may be null carriers on which no information is transmitted, or may be used for some information transmission. . Further, only the subcarrier SC1 with the center frequency f0 may be used as a null carrier in the section after the ACH, and the adjacent subcarriers SC2 and SC3 may be used for information transmission in the section after the ACH.

  In the section in which a specific control signal is transmitted by the three subcarriers SC1, SC2, and SC3, as already described, an encoding format that can be received and processed with simple and low power consumption, such as correlation detection, or a DC offset. A control signal may be transmitted using an encoding format that can be easily removed.

  As another example of subcarrier arrangement, the configuration shown in FIG. That is, as shown in FIG. 22, when an OFDM modulated signal is composed of a plurality of subcarriers such as 53 transmission bands, subcarrier SC1 (equivalent baseband system) of center frequency f0 in the carrier frequency band. A specific control signal such as a terminal station call signal (or a part of the terminal station call signal) is transmitted using only one subcarrier (DC subcarrier).

  The broadcast burst and downlink phase in one MAC frame in the case of FIG. 22 are shown in FIG. 23. In this example, the broadcast preamble, BCH, and FCH in this broadcast burst are shown in FIG. The subcarriers SC1, SC2, and SC3 are used for specific control signal transmission. In a section not used for transmission of a specific control signal of each MAC frame, the subcarrier SC1 may be a null carrier through which no information is transmitted, or may be used for some information transmission.

  In the section in which a specific control signal is transmitted by the subcarrier SC1, as already described, an encoding format that can be received with simple and low power consumption, such as correlation detection, or an encoding format that can easily remove a DC offset. May be used to transmit the control signal.

  Also, when the position of multiple subcarriers centered on the center frequency f0 in the carrier frequency band is assigned for the transmission of a specific control signal such as a paging signal, the band where the multiple subcarriers are allocated is occupied. One subcarrier may be arranged. That is, for example, as shown in FIG. 24, a single subcarrier SCa is used by using a band where three subcarriers SC1, SC2, and SC3 are originally arranged around a center frequency f0 in the carrier frequency band. Arrange and transmit from the base station. Then, a specific control signal such as a calling signal of the terminal station is transmitted using one subcarrier SCa having a wide bandwidth.

  FIG. 25 shows the broadcast burst and downlink phase in one MAC frame in the case of FIG. 24. In this example, in the broadcast preamble, BCH, and FCH in this broadcast burst, One subcarrier SCa is used for specific control signal transmission. In a section not used for transmission of a specific control signal of each MAC frame, three subcarriers SC1, SC2, and SC3 having the same bandwidth as other subcarriers are arranged in a band used for transmission of the subcarrier SCa. Used for information transmission.

  In a section in which a specific control signal is transmitted on a subcarrier SCa having a wide bandwidth, as described above, a control signal is transmitted by adopting a coding format that can be received and processed with simple and low power consumption, such as correlation detection. You may make it do.

  If the specific control signal is transmitted on the subcarrier SCa having a wide bandwidth as in the examples of FIGS. 24 and 25, the terminal station can easily receive the specific control signal transmitted on the subcarrier SCa. As a result, the signal can be received satisfactorily with simple and low power consumption and without erroneous detection. However, in the example of FIGS. 24 and 25, the orthogonality with other subcarriers is lost. In addition, it is necessary to pay attention to selection of the transmission power of the subcarrier SCa so that the transmission characteristics of data transmitted using other subcarriers do not deteriorate.

  Next, a third embodiment of the present invention will be described with reference to FIGS.

  Also in the case of this embodiment, as in the case of the first and second embodiments described above, an OFDM modulated signal is wirelessly transmitted between the base station and the terminal station, and information transmission is performed. The basic configuration to be performed is the same as the configuration described in the first and second embodiments. In this example, transmission of a specific control signal such as a calling signal of a terminal station from the base station is performed at a timing prepared exclusively for the MAC frame.

  That is, in the first and second embodiments already described, the transmission of a specific control signal is transmitted using a predetermined narrow band carrier or a specific subcarrier. In this case, transmission is performed using a section dedicated for transmitting a specific control signal in one MAC frame.

  Specifically, for example, as described in the first embodiment, one MAC frame is composed of four parts of a broadcast burst, a downlink phase, an uplink phase, and a contention phase. At the end, a section dedicated to call signals is prepared. For example, as shown in FIG. 28, as a configuration within one MAC frame, it is used for transmission of a broadcast burst (BCH, FCH, ACH, etc.) for transmitting a control signal from the base station, and an information signal from the base station to the terminal station. A downlink phase (DL phase), an uplink phase (UL phase) used for transmission of information signals and the like from the terminal station to the base station, and a contention phase including an RCH used for outgoing calls from the terminal station; The configuration up to is prepared as described in the first embodiment.

  In this example, as shown in FIG. 28, a call signal transmission section is prepared after the RCH in the contention phase in one MAC frame, and each terminal station is called from the base station in the call signal section. Send a signal. Note that this calling signal section may use, for example, a period not used for communication, which is prepared at the end of the already proposed frame configuration.

  The signal transmitted from the base station in this call signal transmission section may be, for example, an OFDM-modulated multicarrier signal that is a signal of the same modulation scheme as a signal arranged in another section in one MAC frame. Thus, a signal that can easily process the received signal may be transmitted.

  For example, a signal having a low clock frequency may be transmitted as a signal transmitted in the calling signal transmission section. As a signal with a low clock frequency, for example, in the first embodiment, the M-ary encoding described in FIG. 11 or the encoding that performs the repeated transmission processing of the even number described in FIG. 13 may be applied. good. In any case, in the paging signal transmission section, a modulated signal that can be received by a relatively simple reception process different from the OFDM modulated signal is wirelessly transmitted.

  In this case, for example, the configuration shown in FIG. 26 is applicable as the terminal station. FIG. 26 is a diagram showing a configuration for supplying a clock or the like to the reception system of the terminal station. The signal received by the antenna 223 is amplified by the RF amplifier 231, and the amplified output is mixed by the sine wave generated by the frequency synthesizer 233 and the quadrature detector 232, and a reception signal of a specific transmission frequency is extracted and received. It is supplied to the processing unit 250. Reception processing such as demodulation of a received signal is performed in the reception processing unit 250. As a clock to be supplied to the reception processing unit 250, an output of the basic clock generator 292 and generation of a low frequency clock having a frequency lower than the basic clock are generated. The output of the device 293 is selectively supplied by switching with the changeover switch 291. Instead of providing the low frequency clock generator 293, the output of the basic clock generator 292 may be divided by a frequency divider to obtain a low frequency clock.

  The reception processing unit 250 performs reception processing using the output of the basic clock generator 292 during normal reception, and the reception processing unit 250 using the output of the low frequency clock generator 293 during standby at the terminal station. Receive processing. The reception at the terminal station is basically performed by intermittent reception in which only the call signal transmission section shown in FIG. 28 is received, and can be received only once every several frames.

  For the other configurations of the terminal station and the configuration of the base station, the configurations described in the first and second embodiments are applicable, and the description thereof is omitted here.

  By configuring in this way and performing reception during standby in the terminal station, power consumption during standby in the terminal station can be effectively reduced. In this case, in the case of this example, since the OFDM modulation signal is not transmitted in the call signal transmission section, there is no influence on the transmission of other OFDM modulation signals, and other embodiments in which the call signal has already been described. There is a high possibility of transmission under better conditions than in the case of. Further, the frequency of radio transmission is exactly the same in the calling signal transmission section and other sections, and the frequency steps created by the frequency synthesizer 233 need not be changed at all, and the configuration of the terminal station Is not complicated.

  When the transmission band of the signal transmitted in the calling signal transmission section is narrower than the bandwidth of the signal transmitted in the other section, the reception system may be configured to pass the band filter when receiving the calling signal. . That is, for example, as shown in FIG. 27, the output of the quadrature detector 232 that mixes the output of the RF amplifier 231 and the output of the frequency synthesizer 233 is supplied to the changeover switch 294 and passed through the bandpass filter 295. A system that can be switched to a system that does not pass the filter is used. Then, the output of the system that has passed through the band filter 295 and the output of the system that has not passed through the filter are selected by the changeover switch 296 and input to the reception processing unit 250. The band filter 295 is a filter that extracts the transmission band of the call signal transmitted in the call signal transmission section. The clock supplied to the reception processing unit 250 is configured to selectively supply the output of the basic clock generator 292 and the output of the low frequency clock generator 293 by switching with the changeover switch 291.

  The changeover switches 291, 294, and 296 are switched under the control of the control unit in conjunction with the reception state of the terminal station. That is, when receiving a call signal from the base station when the terminal station is in a standby state, the selector switch 291 for selecting a clock is set to the low frequency clock generator 293 side, and a switch for selecting use or non-use of a filter is selected. The switches 294 and 296 are on the side where the band filter 295 is used. In the normal reception state in which information transmission or the like is performed at the terminal station, the selector switch 291 for selecting the clock is set to the basic clock generator 292 side, and the selector switches 294 and 296 for selecting use / non-use of the filter are provided. It is assumed that the band filter 295 is not used. In addition, when the transmission frequency of the call signal transmitted in the call signal transmission section is different from the frequency transmitted from the base station at the time of information transmission or the like, the output frequency of the frequency synthesizer 233 is also changed in conjunction. There is a need.

  By configuring the terminal station in this way, it becomes possible to easily cope with not only the change in the clock frequency but also the change in the transmission band.

  In each of the embodiments described so far, the example applied to a wireless communication method called HiSWANa has been described as a basic example. However, the present invention can also be applied to a system that performs wireless communication by applying another OFDM modulation method. is there. In that case, it is necessary to appropriately change the number of subcarriers constituting one unit of OFDM modulation signal, the frequency arrangement, and the like.

  In each of the above-described embodiments, the terminal station call signal (or part of the call signal) is arranged as a specific control signal transmitted by a narrowband carrier or a specific subcarrier. Other specific control signals may be arranged and wirelessly transmitted.

  In the first embodiment described above, the terminal station has a configuration such as a filter or an AD converter for receiving a specific control signal transmitted by a narrow band carrier and all of one transmission band at the time of normal reception. In the second embodiment, a filter and an AD converter that can be variably set are prepared and used in common. However, it is also possible to apply the configuration of each terminal station to another example of the embodiment. Also in the third embodiment, any configuration described in the first and second embodiments may be applied to the filter and the AD converter.

  In each of the embodiments described so far, a processing circuit for transmitting or receiving a specific control signal such as a paging signal is configured in each of a base station and a terminal station that perform radio communication using the OFDM modulation scheme. However, for example, a control program that executes similar transmission processing and / or reception processing is created as software, and the control program is installed in the base station or terminal station so that the same transmission operation and reception operation are performed. Anyway. In this case, the control program may be stored (recorded) on a medium such as a disk or a tape and distributed to a company that operates the base station or distributed to a user who owns the terminal station. Alternatively, it may be distributed via a transmission medium such as the Internet.

It is explanatory drawing which showed the system configuration example to which this invention is applied. It is the block diagram which showed the structural example of the transmission part of the base station by the 1st Embodiment of this invention. It is the frequency characteristic figure which showed the example of carrier arrangement | positioning by the 1st Embodiment of this invention. FIG. 5 is a timing diagram showing an example of a signal transmission state according to the first embodiment of the present invention. FIG. 6 is a frequency characteristic diagram showing another example of subcarrier arrangement according to the first embodiment of the present invention. It is the block diagram which showed the structural example of the terminal station by the 1st Embodiment of this invention. It is explanatory drawing which showed the state transition example (example 1) of the terminal station by the 1st Embodiment of this invention. It is explanatory drawing which showed the state transition example (example 2) of the terminal station by the 1st Embodiment of this invention. It is the block diagram which showed a part of structure of the base station by the 1st Embodiment of this invention. It is the block diagram which showed a part of structure of the terminal station by the 1st Embodiment of this invention. It is explanatory drawing which showed an example of M-ary encoding applied to this invention. It is the block diagram which showed a part of other structural example of the base station by the 1st Embodiment of this invention. It is explanatory drawing which showed the example of a transmission process of the control signal from which DC offset is removed. It is explanatory drawing which showed the example in case DC offset is not removed. It is the block diagram which showed an example of the structure of the principal part of the terminal station by the 1st Embodiment of this invention. It is the frequency characteristic figure which showed the example of subcarrier arrangement | positioning by the 2nd Embodiment of this invention. It is the timing diagram which showed the example of the control signal transmission state by the 2nd Embodiment of this invention. It is the block diagram which showed the structural example of the terminal station by the 2nd Embodiment of this invention. It is explanatory drawing which showed the state transition example of the terminal station by the 2nd Embodiment of this invention. It is the frequency characteristic figure which showed the other example of the subcarrier arrangement | positioning by the 2nd Embodiment of this invention. FIG. 21 is a timing diagram illustrating an example of a control signal transmission state in the example of FIG. 20. It is the frequency characteristic figure which showed the further another example of the subcarrier arrangement | positioning by the 2nd Embodiment of this invention. FIG. 23 is a timing chart showing an example of a control signal transmission state in the example of FIG. 22. It is the frequency characteristic figure which showed the further another example of the subcarrier arrangement | positioning by the 2nd Embodiment of this invention. FIG. 25 is a timing diagram illustrating an example of a control signal transmission state in the example of FIG. 24. It is the block diagram which showed the structural example which changes the clock frequency in the terminal station by the 3rd Embodiment of this invention. It is the block diagram which showed the structural example which changes the clock frequency and filter in the terminal station by the 3rd Embodiment of this invention. It is explanatory drawing which showed the example of a frame structure by the 3rd Embodiment of this invention. It is the frequency characteristic figure which showed the example of carrier arrangement | positioning of the conventional radio | wireless communications system. It is the frequency characteristic figure which showed the example of subcarrier arrangement | positioning of the conventional radio | wireless communications system. It is explanatory drawing which showed the example of the control signal transmission state of the conventional radio | wireless communications system. It is the block diagram which showed the structural example of the conventional terminal station.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base station, 2 ... External network, 3, 4 ... Terminal station (mobile station), 100 ... Base station transmission part, 101 ... Control part, 102 ... Control signal line, 103 ... Terminal station control signal waveform preparation part, 111 ... Transmission data processing unit, 112 ... CRC addition unit, 113 ... Encryptor, 114 ... Scrambler, 115 ... Encoder, 116 ... Interleaver, 117 modulator, 118 ... Complex IFFT (Inverse Fast Fourier Transform) unit, 119 DESCRIPTION OF SYMBOLS ... Adder, 120 ... Time waveform shaping unit, 121 ... DA converter, 122 ... RF transmitter, 131 ... Calling terminal determination means, 132 ... Transmission bit string determination means, 133 ... M-ary signal generation means, 134 ... Mixer 135, PN sequence generation unit, 136, pilot addition means, 200, 200 ′, terminal station, 201, data input / output processing unit, 202, control unit, 203, 204, 05 ... control signal line 211 ... transmission data processing unit 212 ... CRC adding unit 213 ... encryptor 214 ... scrambler 215 ... encoder 216 ... interleaver 217 ... modulator 218 ... complex IFFT ( Inverse fast Fourier transform) unit, 219 ... time waveform shaping unit, 220 ... DA converter, 221 ... RF transmitter, 222 ... antenna duplexer, 223 ... antenna, 230, 230 '... RF receiver, 231 ... RF amplifier, 232 ... Quadrature detector, 233 ... Frequency synthesizer, 234 ... First filter, 235 ... Second filter, 236 ... Passband variable filter, 241 ... First AD converter, 242 ... Control signal receiver, 243 ... complex cross-correlation calculator, 244 ... reference signal generator, 245 ... comparator, 246 ... correlation threshold setting unit, 250 ... reception processing unit, 251 ... second AD Converter 252 ... Synchronous circuit 253 Time waveform shaping section 254 Complex FFT (fast Fourier transform) section 255 Equalizer 256 256 Demodulator 257 Deinterleaver 258 Decoder 259 Descrambler, 260 ... Decryptor, 261 ... CRC checker, 262 ... Received data processor, 263 ... Sampling rate variable AD converter, 264 ... Control signal receiver, 271, 272 ... Delay circuit, 273, 274, 275 ... Coefficient multipliers, 276, 277, 278 ... Mixer, 279 ... Received bit string estimation means, 280 ... Calling terminal estimation means, 281 ... PN sequence generation unit, 282 ... Subtractor, 291 ... Changeover switch, 292 ... Basic clock generation , 293 ... low frequency clock generator, 294 ... changeover switch, 295 ... band filter, 296 ... changeover switch, DESCRIPTION OF SYMBOLS 300 ... Terminal station, 301 ... Data input / output processing part, 302 ... Control part, 303, 304 ... Control signal line, 311 ... Transmission data processing part, 312 ... CRC addition part, 313 ... Encryption, 314 ... Scrambler, 315 ... Encoder, 316 ... Interleaver, 317 ... Modulator, 318 ... Complex IFFT (Inverse Fast Fourier Transform) section, 319 ... Time waveform shaping section, 320 ... DA converter, 321 ... RF transmitter, 322 ... Shared antenna 323 ... antenna, 331 ... RF receiver, 332 ... AD converter, 333 ... synchronization circuit, 334 ... time waveform shaping unit, 335 ... complex FFT (fast Fourier transform) unit, 336 ... equalizer, 337 ... demodulation , 338 ... Deinterleaver, 339 ... Decryptor, 340 ... Descrambler, 341 ... Decryptor, 342 ... CRC check unit, 343 ... Received data Data processing unit

Claims (12)

In a wireless communication method for performing information transmission between a base station and a terminal station using a multicarrier signal according to an OFDM modulation scheme,
A control signal transmitted and received between a base station and a terminal station is transmitted as a single subcarrier that occupies a band of a plurality of subcarriers adjacent to each other on a frequency centered on a DC subcarrier in the band of the multicarrier signal. Use to transmit
No line communication method. In a wireless communication system that performs information transmission between a base station and a terminal station using a multicarrier signal according to an OFDM modulation scheme,
As the base station, a control signal addressed to the terminal station is used by using one subcarrier that occupies a band of a plurality of adjacent subcarriers on a frequency centered on a DC subcarrier within the band of the multicarrier signal. Transmission signal generating means for modulating;
Transmission processing means for arranging and transmitting the multicarrier signal generated by the transmission signal generating means and the signal of the one subcarrier in a prepared frequency band;
Position where the terminal station receives a multicarrier signal transmitted using a prepared frequency band and a plurality of subcarriers adjacent to each other on a frequency centering on a DC subcarrier in the frequency band painting Bei and reception processing means for selectively performing the reception only
Radio communications system. The wireless communication system according to claim 2 , wherein
The control signal addressed to the terminal station transmitted from the base station using the one subcarrier occupying the band of the specific subcarrier is a signal for calling the terminal station, or a signal for the call. As part
The reception processing means of the terminal station periodically receives a band of a plurality of subcarriers adjacent to each other on a frequency centered on the DC subcarrier when waiting for a call from the base station , and receives the DC subcarrier. When it is determined that there is a call with a signal transmitted using one subcarrier that occupies bands of a plurality of adjacent subcarriers on the center frequency, wireless communication is switched to reception of the multicarrier signal. system. In a radio base station that performs information transmission using a multicarrier signal according to an OFDM modulation scheme with a terminal station,
The information to be transmitted is modulated by an OFDM modulation method to generate a multicarrier signal, and a control signal addressed to the terminal station is transmitted to a plurality of sub-carriers adjacent to each other on a frequency centered on a DC subcarrier within the band of the multicarrier signal. Transmission signal generating means for modulating with one subcarrier occupying the carrier band ;
A radio base station comprising: a transmission processing unit configured to transmit the multicarrier signal generated by the transmission signal generation unit and the signal of the one subcarrier in a prepared frequency band. In the radio base station according to claim 4 ,
The control signal addressed to the terminal station modulated by the one subcarrier occupying a plurality of subcarrier bands by the transmission signal generating means is a signal for calling the terminal station or one of signals for the call. A radio base station. In the radio base station according to claim 4 ,
The transmission processing means transmits a part of the control signal addressed to the terminal station using the one subcarrier occupying the bands of the plurality of subcarriers at a timing synchronized with the frame position for information transmission. Perform a radio base station. In a wireless communication terminal that performs information transmission with a base station using a multicarrier signal according to an OFDM modulation scheme,
Reception of a multicarrier signal transmitted using a prepared frequency band and reception of only a position where a plurality of adjacent subcarriers are arranged on a frequency centering on a DC subcarrier in the frequency band. A reception processing means for selectively performing;
Control for selecting a reception state in the reception processing means in accordance with an operation state and detecting a control signal from a base station from reception signals of a plurality of subcarriers adjacent on the frequency centering on the DC subcarrier. and means,
When the reception processing means receives only a band in which a plurality of subcarriers adjacent to each other on the frequency centered on the DC subcarrier are received, the decoding processing is performed without performing transmission path estimation processing. Wireless communication that performs reception processing of signals transmitted in the carrier band and performs decoding processing by estimating the transmission path when a multicarrier signal transmitted using the prepared frequency band is received Terminal. In a wireless communication terminal that performs information transmission with a base station using a multicarrier signal based on an OFDM modulation scheme,
Reception of a multicarrier signal transmitted using a prepared frequency band and reception of only a position where a plurality of adjacent subcarriers are arranged on a frequency centering on a DC subcarrier in the frequency band. A reception processing means for selectively performing;
Control for selecting a reception state in the reception processing means in accordance with an operation state and detecting a control signal from a base station from reception signals of a plurality of subcarriers adjacent on the frequency centering on the DC subcarrier. Means and
The reception processing means performs reception processing on a signal transmitted using a plurality of adjacent subcarrier bands on a frequency centered on the DC subcarrier for an even number of times, and removes an offset of the received signal. Wireless communication terminal. In a wireless communication system that performs information transmission between a base station and a wireless communication terminal using a multicarrier signal according to an OFDM modulation scheme,
As the wireless communication terminal,
Reception of a multicarrier signal transmitted using a prepared frequency band and reception of only a position where a plurality of adjacent subcarriers are arranged on a frequency centering on a DC subcarrier in the frequency band. A reception processing means for selectively performing;
Control for selecting a reception state in the reception processing means in accordance with an operation state and detecting a control signal from a base station from reception signals of a plurality of subcarriers adjacent on the frequency centering on the DC subcarrier. Means and
When the reception processing means receives only the bands of a plurality of subcarriers adjacent on the frequency centered on the DC subcarrier, the reception processing means performs a decoding process without performing a transmission path estimation process. If the multicarrier signal transmitted using the prepared frequency band is received, the transmission path is estimated and the decoding process is performed.
Wireless communication system. In a wireless communication system that performs information transmission between a base station and a wireless communication terminal using a multicarrier signal according to an OFDM modulation scheme,
As the wireless communication terminal,
Reception of a multicarrier signal transmitted using a prepared frequency band and reception of only a position where a plurality of adjacent subcarriers are arranged on a frequency centering on a DC subcarrier in the frequency band. A reception processing means for selectively performing;
The reception processing means selects the reception state according to the operation status, and the control signal from the base station is detected from the reception signals of a plurality of adjacent subcarrier bands on the frequency centered on the DC subcarrier. Control means for
The reception processing means performs reception processing on a signal transmitted using a plurality of adjacent subcarrier bands on a frequency centered on the DC subcarrier for an even number of times, and removes an offset of the received signal.
Wireless communication system. In a wireless communication method for performing information transmission between a base station and a terminal station using a multicarrier signal according to an OFDM modulation scheme,
In the terminal station, reception processing of a multicarrier signal transmitted using a prepared frequency band and a plurality of subcarriers adjacent to each other on a frequency centering on a DC subcarrier in the frequency band are arranged. Selectively receive only the position,
The reception process is selected according to an operation situation, and a control signal from a base station is detected from reception signals of a plurality of subcarriers adjacent on a frequency centered on the DC subcarrier,
When reception processing is performed only at a position where a plurality of subcarriers adjacent to each other on a frequency centered on the DC subcarrier is performed, decoding processing is performed without performing transmission path estimation processing, and the bandwidth of this subcarrier is determined. When a multi-carrier signal transmitted using a prepared frequency band is received, a transmission path estimation process is performed and a decoding process is performed.
Wireless communication method. In a wireless communication method for performing information transmission between a base station and a terminal station using a multicarrier signal according to an OFDM modulation scheme,
In the terminal station, reception processing of a multicarrier signal transmitted using a prepared frequency band and a plurality of subcarriers adjacent to each other on a frequency centering on a DC subcarrier in the frequency band are arranged. Selectively receive only the position,
The reception process is selected according to an operation situation, and a control signal from a base station is detected from reception signals in a plurality of adjacent subcarrier bands on the frequency centered on the DC subcarrier.
In the reception processing, a signal transmitted using a plurality of adjacent subcarrier bands on the frequency centered on the DC subcarrier is subjected to reception processing for an even number of times, and the received signal offset is removed.
Wireless communication method.

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