JP4962410B2 - Receiver - Google Patents

Description

  The present invention encodes transmission data with an error correction code, receives a transmission radio wave from a transmission device that wirelessly transmits the rearranged bit arrangement of the encoded data by interleaving, and transmits the original transmission from the received signal. The present invention relates to a receiving apparatus for restoring data.

  Conventionally, as a wireless communication system that transmits and receives data between a plurality of communication devices via a wireless transmission path, a communication device that intends to transmit data detects a free state of a communication channel used for data communication by carrier sense, After that, a CSMA / CA wireless communication system configured to start data transmission if a communication channel is free even after a predetermined random time (backoff time) has elapsed is known.

  In this wireless communication system, access control based on carrier sense prevents a plurality of communication devices from starting data transmission at the same time, and prevents transmission radio waves from each communication device from interfering. On the side of the communication device that receives the transmission radio wave from the communication device, the transmission radio wave from each transmission device interferes, and data may not be received normally.

  For example, as shown in FIG. 6, when a CSMA / CA communication device is mounted on a plurality of vehicles and vehicle-to-vehicle communication is performed, the vehicle B and the vehicle C to transmit data are separated from each other, and When the other party's transmission radio wave cannot be received, the vehicles B and C acquire the transmission right on the same communication channel and start data transmission by access control based on carrier sense.

  However, when the vehicle A exists between the vehicle B and the vehicle C at a position where the transmission radio waves from the vehicles B and C can be received, the radio waves from the vehicles B and C interfere at the position of the vehicle A. The vehicle A cannot normally receive the transmission data from the vehicles B and C.

  On the other hand, as a radio communication system suitable for preventing such reception failure due to interference, on the transmitting device side that transmits data, transmission data is encoded with an error correction code (Viterbi code) and the encoded data It is known that a bit sequence for transmission is generated by rearranging the bit arrangement of the signal by interleaving, the bit sequence is modulated into a signal for wireless transmission (for example, OFDM modulation) in a symbol unit of a predetermined bit length, and transmitted wirelessly. ing.

  In this type of wireless communication system, the receiving device side demodulates the received signal in order to restore the received data more accurately without being affected by radio wave interference on the receiving device side. For example, a baseband signal (a signal corresponding to a bit string) obtained by performing OFDM demodulation is soft-determined for each bit, and the arrangement of each bit string is restored (deinterleaved), and obtained by the soft-decision. It is known to perform error correction decoding based on soft decision values.

In addition, when performing such error correction decoding, if an interference wave is superimposed on the radio wave being received (desired wave), the soft decision value may be affected by the interference wave and error correction may not be executed normally. When the signal level of the received signal increases during error correction decoding, it is determined that an interference wave is superimposed on the desired wave (in other words, radio wave interference has occurred), and the soft decision value is a value with a likelihood of zero It is also proposed that the soft decision value does not contribute to error correction decoding (Viterbi decoding) by correcting to (for example, see Patent Document 1).
JP 2001-257604 A

  According to the radio communication system proposed above, so-called NULL control is performed on the receiving device side, when an interference wave is superimposed on a desired wave, detecting that fact and correcting the soft decision value to a value of zero likelihood. Therefore, it is possible to prevent the received signal obtained during the interference period from being used for restoration of received data, and to improve the reliability of data reception.

  However, in the proposed wireless communication system, the interference wave is a pulsed radio wave transmitted from another system (for example, a weather radar), and the transmission power of the interference wave is much more extreme than the desired wave. The radio wave interference is detected from the signal level of the received signal as being large (in other words, the reception power difference between the interference wave and the desired wave is extremely large).

  Therefore, like the wireless communication system that performs vehicle-to-vehicle communication shown in FIG. 6, the transmission power from the communication devices mounted on the vehicles B and C is substantially the same, and the transmission radio waves from the vehicles B and C are received. On the vehicle A side, in a system where the signal level of the received signal does not change significantly before and after the radio wave interference (in other words, the difference in received power between the interference wave and the desired wave is small), There is a problem that it is not possible to detect and implement countermeasures at the time of interference such as NULL control.

  The present invention has been made in view of these problems, and in a receiving apparatus that performs error correction decoding of received data by soft decision and deinterleaving of a signal demodulated from a received signal, an interference wave is superimposed on the radio wave being received / demodulated. When it is done, even if the level fluctuation of the received signal is small, the purpose is to detect that fact accurately and to suppress the influence of the interference wave on the decoding operation.

In order to achieve this object, the receiving apparatus according to claim 1, wherein the transmission data is encoded with an error correction code, and the bit arrangement is rearranged over a plurality of symbols by interleaving to generate a bit string for transmission. This is for receiving transmission radio waves from a transmitting device that wirelessly transmits a signal obtained by OFDM-modulating the generated bit string in symbol units of a predetermined bit length, and for restoring transmission data. Transmission from the transmitting device An antenna for receiving radio waves is provided.

  Then, the demodulating means receives the received signal from the antenna, and OFDM demodulates the signal corresponding to the bit string generated on the transmitting device side, and the decoding means performs soft decision and deinterleave on the demodulated signal, Transmission data is restored by performing error correction decoding based on the soft decision value obtained by the soft decision.

In addition, the receiving apparatus according to claim 1 is provided with dispersion calculating means for calculating a dispersion value representing the dispersion of the signal within one symbol of the OFDM signal for each symbol of the OFDM signal demodulated by the demodulation means. When the dispersion value calculated by the dispersion calculation means exceeds a preset threshold value, the interference detection means detects that the interference wave is superimposed on the radio wave (desired wave) being received by the antenna. To do.

  That is, in the demodulation means, the OFDM signal is restored by down-conversion of the received signal, filtering, etc., but since the OFDM signal is composed of a plurality of subcarriers in an orthogonal relationship, The variance of the signal within one OFDM signal symbol increases.

Therefore, in the receiving apparatus according to claim 1, for each symbol of the OFDM signal demodulated by the demodulating means , a variance value representing the variance of the signal within one symbol of the OFDM signal is calculated, and the variance value is a threshold value. When this happens, radio wave interference is detected.

  For this reason, according to the first aspect of the present invention, even when the level fluctuation of the received signal is small, it is possible to detect radio wave interference from the received signal and take measures such as the above-described NULL control. become able to.

In the receiving apparatus according to claim 1 , when the interference detecting unit detects the superposition of the interference wave on the desired wave (that is, radio wave interference), as described in claim 2 , The soft decision value used for error correction decoding may be corrected so as to reduce the contribution to error correction decoding. At this time, according to the interleaving of the present invention, each bit before the interleaving is different in each packet according to a predetermined rule so that the continuous arrangement between the bits constituting the input bit string before the interleaving becomes discontinuous. It is desirable to distribute over a plurality of symbols received at the time.

  In other words, in this way, even if radio wave interference occurs in the latter half of the packet, for example, the interfering bits due to deinterleaving can be scattered in the packet, and the soft decision value is error corrected. In order not to contribute to decoding, it is possible to improve the restoration accuracy of transmission data from a desired wave.

  The soft decision value may be corrected such that the soft decision value is corrected so that the likelihood is zero, as in the above-described NULL control, or depending on the degree of radio wave interference. The soft decision value may be corrected.

  In addition, when interference of radio waves is detected by the interference detection means, in addition to the operation of restoring the transmission data from the desired wave, the operation of restoring the transmission data from the interference wave is executed in parallel. Data may be restored from each interference wave.

Next, the receiving device according to claim 3 encodes transmission data with an error correction code, generates a bit string for transmission by rearranging the bit arrangement by interleaving, and generates the generated bit string with a predetermined bit length. This is for receiving a transmission radio wave from a transmission device that wirelessly modulates a signal for radio transmission in units of symbols and restoring transmission data from the received signal, and receives a transmission radio wave from the transmission device Provide an antenna.

  The demodulating means receives the received signal from the antenna, demodulates the signal corresponding to the bit string generated on the transmitting device side, and the decoding means performs soft decision and deinterleave on the demodulated signal, and performs soft decision. Transmission data is restored by performing error correction decoding based on the soft decision value obtained by the decision.

The receiving apparatus according to claim 3 is provided with data length measuring means for measuring the length of data being received by the antenna from the signal level of the received signal, and the length of the measured data is When the preset packet length is exceeded, the interference detection unit detects that the interference wave is superimposed on the radio wave being received by the antenna.

That is, in order to enable the reception apparatus according to claim 3 to detect an interference wave even if the reception signal is a signal modulated by OFDM or a signal modulated by another modulation method, When the antenna measures the length of data being received and the measured data length is longer than the preset packet length, an interference wave is transmitted during reception of the desired wave, and the data reception period ( It is determined that (data length) has become longer (in other words, radio wave interference has occurred).

Therefore, according to the receiving device according to claim 3 , like the receiving device according to claims 1 and 2 , the radio signal interference is detected from the received signal even when the level fluctuation of the received signal is small. In addition, the present invention can also be applied to a wireless communication system in which the transmission radio wave modulation scheme is different from that of the OFDM scheme.

Note that in the receiving device according to claim 3 , the interference detecting means determines the radio wave interference from the data reception time (data length) and the packet length, but the packet length transmitted from the transmitting device is the transmission data. Therefore, if the data length that the transmission device transmits in one transmission operation is not fixed, the packet length used for determination changes according to the length of the transmission data from the transmission device. It is necessary to let

For this purpose, as described in claim 4 , the interference detection means obtains the packet length of the data being received by the antenna from the header area of the received data that has been subjected to error correction decoding by the decoding means, The acquired packet length may be set as the packet length for interference wave detection.

Further, in the receiving device according to claims 3 and 4 , interference is detected from the data length measured by the data length measuring means, but the measured data length is longer than a preset packet length, and radio wave interference Even if the interference occurs, if the level of the interference wave with respect to the desired wave is low, transmission data may be restored from the desired wave without correcting the soft decision value by NULL control or the like.

Therefore, in order to detect radio wave interference and take measures such as NULL control only when transmission data cannot be restored, the interference length detection unit includes a data length measurement unit as described in claim 5. If it is determined that the length of the data measured in step 1 exceeds the preset packet length, the power of the interference wave is obtained from the signal level of the received signal that exceeds the packet length, and the power is set in advance. When the threshold value is exceeded, it may be determined that the interference wave is superimposed on the desired wave.

Next, in the receiving device according to any one of claims 3 to 5 , since the interference of the radio wave is determined based on the data length measured by the data length measuring unit, the interference detecting unit detects the radio wave interference. The timing of the transmission is after the transmission of the desired wave from the transmission device is completed, and the control is performed to detect the interference wave in real time during the reception of the desired wave and to improve the accuracy of transmission data restoration (that is, soft decision value correction). Can not be executed.

Therefore, in the receiving apparatus according to claims 3 to 5 , when radio wave interference is detected, the soft decision value is corrected in the same manner as in claim 2 so as to increase the restoration accuracy of transmission data. According to a sixth aspect of the present invention , there is provided storage means for storing the output from the demodulation means, and when the interference detection means detects that the interference wave is superimposed on the radio wave being received by the antenna, the data length measurement means The interference wave superposition position is identified from the measured data length and the preset packet length, and the contribution of the soft decision values after the superposition position to the error correction decoding is reduced for the decoding means. The received data may be restored based on the signal stored in the storage means while correcting the correction.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a wireless communication apparatus according to the first embodiment to which the present invention is applied.

The wireless communication apparatus according to the present embodiment is mounted as an in-vehicle device in various automobiles in order to construct a wireless communication system that performs vehicle-to-vehicle communication as shown in FIG.
As shown in FIG. 1, the wireless communication device receives a transmission request from a transmission device 10 and a reception device 20 connected to an antenna 4 via a circulator 2 and an electronic control device (not shown) mounted on the vehicle. A transmission control unit 6 that performs CSMA / CA access control and permits data transmission from the transmission device 10.

  The transmission apparatus 10 also includes an error correction encoder 12 that encodes transmission data input from the electronic control apparatus using an error correction code (for example, a convolutional code), and data encoded by the error correction encoder 12. An interleaver 14 that performs interleave processing for rearranging the bit arrangement, a preamble insertion unit 16 that inserts preamble data into the output from the interleaver 14, and data in which the preamble has been inserted by the preamble insertion unit 16 are set to a predetermined bit length. And a transmitter 18 that performs OFDM modulation in units of symbols.

  When the transmission apparatus 10 receives a transmission permission from the transmission control unit 6, the error correction encoder 12, the interleaver 14, and the preamble insertion unit 16 encode the transmission data with an error correction code, interleave, and preamble. Is inserted, and a bit string for transmission is generated, and the transmitter 18 performs OFDM modulation on the bit string in symbol units of a predetermined bit length and outputs the result to the circulator 2, so that the surroundings of the vehicle can be obtained from the antenna 4. To transmit transmission data wirelessly.

Note that, in the transmission apparatus 10, the transmitter 18 includes, for example, a mapper that maps the output from the preamble insertion unit 16 to 2 ^N QAM symbol points every N bits, and the mapper output (hereinafter referred to as a primary modulation symbol). Two data sequences representing the I component and the Q component of an OFDM symbol (hereinafter referred to as a secondary modulation symbol) by performing an inverse FFT transform corresponding to M subcarriers used for orthogonal frequency multiplexing (OFDM) A D / A converter that generates two baseband signals representing an I component and a Q component by performing digital-analog conversion on each of two data strings generated by the OFDM modulator, and a D / A conversion A quadrature modulator that generates a transmission signal by mixing two baseband signals generated by the transmitter, and a transmission generated by the quadrature modulator No. up-converts the signal of the predetermined frequency band is composed of a RF transmitting unit for outputting to the circulator 2,.

  Next, when the transmission control unit 6 receives a transmission request from the electronic control unit, the transmission control unit 6 determines the free state of the communication channel based on the carrier sense signal CS output from the receiver 22 in the receiving device 20, and the free state is predetermined. It is a well-known one that determines that the transmission right on the communication channel has been acquired when the random time (back-off time) continues, and permits data transmission from the transmission device 10.

  On the other hand, the receiving device 20 is for capturing the received signal from the antenna 4 via the circulator 2 and restoring the transmission data from the transmitting device 10 of the wireless communication device mounted on the automobile around the host vehicle. Based on the receiver 22 that demodulates the primary modulation symbols corresponding to the M subcarriers generated on the transmission side by processing the received signal and performing OFDM demodulation, and the primary modulation symbols demodulated by the receiver 22 The N bit soft decision value is generated, and the order of the code string composed of the soft decision value is rearranged in the original order by the deinterleaving process, and error correction (maximum likelihood decoding) is performed. The decoder 24 to be generated and the reception signal processing for extracting the transmission data from the reception bit string generated by the decoder 24 and outputting this as reception data to the electronic control unit. Comprises a section 26, the.

  Note that the receiver 22 includes, for example, an RF receiving unit that down-converts a received signal into a signal in a frequency band suitable for signal processing, a filter that removes unnecessary frequency components from the output of the RF receiving unit, and a filter that passes through the filter. An automatic gain control (AGC) amplifier that amplifies the received signal while adjusting the gain so that the average power becomes a predetermined target value, and a baseband representing the I component and the Q component from the received signal amplified by the AGC amplifier A quadrature demodulator that generates a signal, an AD converter that samples two baseband signals generated by the quadrature demodulator, and generates two data strings representing an I component and a Q component, and an AD converter An OFDM demodulator that demodulates primary modulation symbols corresponding to M subcarriers by performing FFT conversion on the two data strings. That.

  In addition, the receiver 20 includes a variance calculator 30 that calculates a variance value σ representing the variance of a signal (spectrum) within one OFDM signal symbol based on the primary modulation symbol demodulated by the receiver 22; The dispersion value σ calculated by the dispersion calculator 30 is compared with a preset dispersion threshold σth, and if the dispersion value σ is equal to or greater than the dispersion threshold σth, the interference signal is superimposed on the received signal ( That is, a comparator 32 for determining that radio wave interference has occurred) is provided.

  When the comparator 32 detects the interference of the interference wave with the desired wave, the comparator 32 evaluates the degree of variation of the received signal from the dispersion value σ and the like, and is a weighting that is a correction value for the soft decision value generated in the decoder 24. The null control information for correcting the value or the soft decision value to a value indicating the likelihood of zero is set and output to the decoder 24 so that the contribution of the error correction decoding to the decoder 24 is reduced. Causes the soft decision value to be corrected.

  As described above, in the receiving apparatus 20 of the present embodiment, the variance calculator 30 calculates the variance value σ representing the variance of the signal for each symbol of the OFDM signal received / demodulated by the receiver 22. When the calculated dispersion value σ becomes equal to or greater than a preset dispersion threshold σth, the comparator 32 determines that an interference wave (interference wave) is superimposed on the currently received radio wave (desired wave). Thus, the soft decision value generated in the decoder 24 is corrected by the weighted value or NULL control information so that the contribution to the error correction decoding is reduced.

  For this reason, according to the receiving apparatus 20 of the present embodiment, even when the signal level of the interference wave is low and the level fluctuation of the reception signal when the interference wave is superimposed on the desired wave is small, Thus, the soft decision value can be corrected and the decoding accuracy of transmission data can be improved.

Note that the receiving device 20 of the present embodiment corresponds to the receiving device described in claim 1. The receiver 22 corresponds to the demodulation means of the present invention, the decoder 24 corresponds to the decoding means of the present invention, the variance calculator 30 corresponds to the variance calculation means of the present invention, and the comparator 32 This corresponds to the interference detection means of the present invention.
[Reference example]
Next, FIG. 2 is a block diagram illustrating a configuration of the receiving device 20 of the reference example .

Similar to the receiving apparatus 20 of the first embodiment , the receiving apparatus 20 of the present reference example includes a receiver 22 as a demodulating unit, a decoder 24 as a decoding unit, and a received signal processing unit 26.

In the receiving apparatus 20 of this reference example , instead of the dispersion detector 30 and the comparator 32 shown in FIG. 1, symbols corresponding to the GI period and the guard interval (GI) period for each OFDM signal symbol are provided. During the backward data period, the GI extractor 42 and the symbol backward extractor 44 that capture the output from the receiver 22 are compared with the signals captured by these extractors 42 and 44, respectively, and the difference Δ When the difference ΔD between the subtraction unit 46 that calculates D and the signal calculated by the subtraction unit 46 is equal to or greater than a preset threshold ΔDth, the interference signal is superimposed on the received signal (that is, the radio wave And a comparator 48 that determines that interference is occurring).

That is, in wireless communication using the OFDM scheme, in order to be able to restore transmission data without being affected by multipaths on the receiving device side, a part of the transmission data behind (for example, by copying 1 / 4,1 / 8,1 / 16, ...) to directly head portion, since the guard interval as the redundant portion of data (GI) is applied, in the present reference example, each of these periods The signal demodulated by the receiver 22 is sampled by the GI extractor 42 and the symbol backward extractor 44, and the sampled signals are compared with each other to obtain a signal difference ΔD during each period. When the difference ΔD is equal to or greater than the threshold ΔDth, radio wave interference is detected.

Therefore, according to the receiving device 20 of the present reference example , as in the first embodiment, the signal level of the interference wave is low, and the level fluctuation of the reception signal when the interference wave is superimposed on the desired wave is small Even so, radio wave interference can be detected from the received signal.

  Similarly to the comparator 32 of the first embodiment, when the comparator 48 detects interference of the interference wave with the desired wave, the comparator 48 evaluates the degree of variation in the received signal from the subtraction result (ΔD) in the subtracting unit 46. Then, by setting a weighting value or NULL control information for the soft decision value generated in the decoder 24 and outputting it to the decoder 24, the degree of contribution to the error correction decoding is reduced for the decoder 24. Thus, the soft decision value is corrected.

Accordingly, in the receiving device 20 of the present reference example , as in the first embodiment, when radio wave interference is detected, the soft decision value is corrected according to the degree of the interference (correction by weighting values, or Correction to a value indicating a likelihood of zero) and the decoding accuracy of transmission data can be increased.

Here, in this reference example , in order to detect the interference of the interference wave (interference wave) with the desired wave, a subtracting unit 46 is provided, and the difference Δ between the signals sampled by the GI extractor 42 and the symbol backward extractor 44. As described in FIG. 3, a correlation calculation unit 47 is provided instead of the subtraction unit 46, and the correlation value C of the signal sampled by the GI extractor 42 and the symbol backward extractor 44 is obtained as shown in FIG. The comparator 48 may detect radio wave interference when the correlation value C is equal to or less than a preset threshold value ΔCth.

In this reference example , the signal in the GI period is compared with the data period behind the symbol corresponding to the GI period. However, the influence of multipath is large, and a signal in the previous symbol is mixed in the signal in the GI period. If you want to. In that case, it is only necessary to limit to a section in which the influence of multipath is small in the GI period and compare them.
[Second Embodiment]
FIG. 4A is a block diagram illustrating a configuration of the receiving device 20 of the second embodiment , and FIG. 4B is a time chart illustrating an interference detection operation in the receiving device 20 of the second embodiment .

The receiving device 20 according to the present embodiment corresponds to the receiving device according to claim 3 , and similarly to the receiving device 20 according to the first embodiment , the receiver 22 as a demodulating unit and the decoder as a decoding unit. 24 and a received signal processing unit 26.

  Of the outputs from the receiver 22, the preamble (P) symbol is output as it is to the decoder 24, and the data (D) symbol following the preamble symbol is temporarily stored in the memory 28. .

  The receiver 22 is configured to measure the signal level (power) of the received signal that has passed through the filter and output an RSSI (Receive Signal Strength Indicator) signal representing the measurement result. The received power is monitored based on the RSSI signal, and when the received power is equal to or higher than a preset threshold value, it is determined that a transmission radio wave from another wireless communication device is received, and the reception duration time A received power monitoring unit 50 that counts the time is provided.

  In addition, the receiving device 20 according to the present embodiment includes a time count Ta measured by the received power monitoring unit 50 and a packet length Tp of transmission data actually transmitted by another wireless communication device (specifically, a time representing the packet length). ) And when the time count Ta is larger than the packet length Tp, it is determined that the interference signal is superimposed on the received signal (that is, radio wave interference has occurred), and the interference time of the interference wave with respect to the desired signal There is also provided an interference time calculation unit 52 for calculating.

  As shown in FIG. 4B, the interference time calculation unit 52 starts receiving the desired wave at the receiver 22 (time t1), and is added to the head of the received signal at the decoder 24. When the present preamble (P) is decoded, the packet length Tp of the received data received this time is acquired from the preamble (P), and this packet length Tp is compared with the time measured Ta by the received power monitoring unit 50 To do.

  If the time count Ta and the packet length Tp match (or substantially match), the decoder 24 decodes the received data using the data (D) symbol stored in the memory 28 (described above). Soft decision, deinterleave, error correction).

  On the other hand, even when the time count Ta reaches the packet length Tp (time t3), the time measurement by the received power monitoring unit 50 ends when the RSSI signal does not become less than the threshold and the time measurement by the received power monitoring unit 50 continues. At the time t4, the normal reception period τ in which the desired wave is not affected by the interference wave is obtained by subtracting the packet length Tp from the measured time Ta finally obtained by the reception power monitoring unit 50, and the receiver 22 The time t2 when the normal reception period τ has elapsed from the time t1 at which reception of the desired wave is started is set as the radio wave interference start timing (in other words, the interference wave superposition position).

  Thereafter, the decoder 24 decodes the received data using the data (D) symbol stored in the memory 28 (the soft decision, deinterleave, and error correction described above). Among the soft decision values set from the data (D) symbols stored in the memory 28, the soft decision values corresponding to the data (D) symbols obtained after the interference start timing t2 are weighted values or By setting the NULL control information, the soft decision value is corrected so that the degree of contribution to error correction decoding decreases.

  As described above, in the receiving device 20 of the present embodiment, based on the RSSI signal representing the signal level of the received signal, the data reception time (in other words, the length of the received data) by the receiver 22 is measured. When the measured time (timed time) Ta exceeds the packet length Tp acquired from the preamble data added to the header area of the received signal, it is determined that the interference wave is superimposed on the desired wave.

Therefore, according to the receiving device 20 of the present embodiment, as in the first embodiment , when the signal level of the interference wave is low and the level fluctuation of the received signal when the interference wave is superimposed on the desired wave is small Even so, radio wave interference can be detected from the received signal.

  Further, in the receiving device 20 of the present embodiment, the interference detection timing is determined by detecting radio wave interference by comparing the time count Ta indicating the data length of the received data with the packet length Tp of the transmission data. After the reception of the desired wave is completed, the transmission data cannot be restored by detecting the interference wave in real time during the reception of the desired wave.

  However, in the present embodiment, the output from the receiver 22 is stored in the memory 28 to determine the presence or absence of radio wave interference, and then the decoder 24 receives from the receiver 22 stored in the memory 28. The transmission data can be restored based on the output, and when radio wave interference is detected, the interference start timing is specified, and the soft decision value obtained by the decoding process by the decoder 24 after the interference start timing. Is corrected so that the degree of contribution to error correction decoding decreases.

For this reason, also in the receiving apparatus 20 of this embodiment, when the interference wave is superimposed on the desired wave, the soft decision value is corrected to improve the decoding accuracy of the transmission data, as in the first embodiment. Can do.

  In the present embodiment, the received power monitoring unit 50 corresponds to the data length measurement unit of the present invention, the interference time calculation unit 52 corresponds to the interference detection unit of the present invention, and the memory 28 corresponds to the present invention. It corresponds to storage means.

  Here, in the present embodiment, when the measured time Ta by the received power monitoring unit 50 becomes longer than the packet length Tp, it is determined that an interference wave (interference wave) is superimposed on the desired wave, and the degree of contribution to error correction decoding However, when the signal level of the interference wave with respect to the desired wave is sufficiently low, the transmission data is restored from the desired wave without correcting the soft decision value. There are things you can do.

  For this reason, for example, in the receiving apparatus 20 of the present embodiment, as shown in FIG. 5, when the interference time calculating unit 52 determines that the timed time Ta is longer than the packet length Tp, the receiver 22 thereafter. If the interference wave power P exceeds the preset threshold value Pht, the soft decision value needs to be corrected in order to restore the transmission data normally. An interference power calculation unit 54 that determines that there is a weight and outputs a weighting value or NULL control information to the decoder 24 may be provided.

Note that the receiving device 20 shown in FIG. 5 corresponds to the receiving device according to claim 5 , and that the interference time calculation unit 52 and the interference power calculation unit 54 correspond to the interference detection means of the present invention. Become.
[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.

For example, the receiving device of the second embodiment measures the reception continuation time of transmission radio waves from other wireless communication devices based on the signal level of the received signal, and the measured time Ta is longer than the packet length Tp of the transmission data. Sometimes, since radio wave interference is detected, the present invention can be applied even to a radio communication system in which the modulation scheme of the transmission radio wave is different from that of the OFDM scheme.

  In the above-described embodiment, the case where the present invention is applied to a wireless communication device mounted on a vehicle for performing inter-vehicle communication has been described. Any receiving apparatus that receives data in which the bit arrangement is rearranged and restores the original data can be applied in the same manner as in the above-described embodiment to obtain the same effect.

It is a block diagram showing the structure of the radio | wireless communication apparatus of 1st Embodiment. It is a block diagram showing the structure of the receiver of a reference example . It is a block diagram showing the modification of the receiver of a reference example . It is explanatory drawing showing the receiver of 2nd Embodiment and its interference detection operation | movement. It is a block diagram showing the modification of the receiver of 2nd Embodiment . It is explanatory drawing explaining the problem of the radio wave interference which generate | occur | produces in vehicle-to-vehicle communication.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Circulator, 4 ... Antenna, 6 ... Transmission control part, 10 ... Transmission apparatus, 12 ... Error correction encoder, 14 ... Interleaver, 16 ... Preamble insertion part, 18 ... Transmitter, 20 ... Reception apparatus, 22 ... Reception 24 ... decoder 26 ... received signal processor 28 ... memory 30 ... dispersion calculator 32 ... comparator 42 ... GI extractor 44 ... symbol backward extractor 46 ... subtractor 47 ... correlation Calculation unit 48... Comparator 50. Received power monitoring unit 52. Interference time calculation unit 54. Interference power calculation unit

Claims (6)

The transmission data is encoded with an error correction code, and a bit string for transmission is generated by rearranging the bit arrangement over a plurality of symbols by interleaving, and the bit string is OFDM-modulated in symbol units of a predetermined bit length. A reception device that receives a transmission radio wave from a transmission device that wirelessly transmits by an antenna and restores the transmission data,
Demodulation means for OFDM-demodulating a signal corresponding to the bit string from a received signal from the antenna;
Decoding means for restoring the transmission data by performing soft correction and deinterleaving on the signal demodulated by the demodulation means, and performing error correction decoding based on the soft decision value obtained by the soft decision;
Dispersion calculating means for calculating a dispersion value representing dispersion of the signal within one symbol of the OFDM signal for each symbol of the OFDM signal demodulated by the demodulation means;
An interference detection means for detecting that an interference wave is superimposed on a radio wave being received by the antenna when the dispersion value calculated by the dispersion calculation means is equal to or greater than a preset threshold;
A receiving apparatus comprising: When the interference detection unit detects that an interference wave is superimposed on a radio wave being received by the antenna, the interference detection unit converts a soft decision value used for error correction decoding in the decoding unit to a degree of contribution to the error correction decoding. The receiving apparatus according to claim 1 , wherein correction is performed so as to decrease. The transmission data is encoded with an error correction code, and a bit sequence for transmission is generated by rearranging the bit arrangement by interleaving, and the bit sequence is modulated into a signal for radio transmission in symbol units of a predetermined bit length. A reception device that receives a transmission radio wave from a transmission device that wirelessly transmits by an antenna and restores the transmission data,
Demodulating means for demodulating a signal corresponding to the bit string from a received signal from the antenna;
Decoding means for restoring the transmission data by performing soft correction and deinterleaving on the signal demodulated by the demodulation means, and performing error correction decoding based on the soft decision value obtained by the soft decision;
Data length measuring means for measuring the length of data being received by the antenna from the signal level of the received signal;
When the length of the data measured by the data length measuring unit exceeds a preset packet length, the interference detecting unit detects that an interference wave is superimposed on the radio wave being received by the antenna;
A receiving apparatus comprising: The interference detection means acquires the packet length of the data being received by the antenna from the header area of the received data that has been error correction decoded by the decoding means, and uses the acquired packet length as a packet for interference wave detection. The receiving apparatus according to claim 3 , wherein the receiving apparatus is set as a length. When the data length measured by the data length measurement unit exceeds the packet length, the interference detection unit obtains the power of the interference wave from the signal level of the received signal, and the power is set to a preset threshold value. 5. The receiving apparatus according to claim 3 , wherein the antenna determines that an interference wave is superimposed on a radio wave being received by the antenna when the frequency exceeds. Storage means for storing the output from the demodulation means;
When the interference detection unit detects that the interference wave is superimposed on the radio wave being received by the antenna, the interference detection unit determines the superimposed position of the interference wave from the data length measured by the data length measurement unit and the packet length. The received data is restored based on the signal stored in the storage means while identifying and correcting the decoding means so that the soft decision value after the specified superposition position is reduced in the contribution to error correction decoding. The receiving device according to claim 3, wherein