JP6346522B2 - Cross polarization interference canceller - Google Patents

Description

  The present invention relates to a cross-polarization interference canceller that removes cross-polarization interference components when receiving a digital signal transmitted using multiple types of polarization.

  In satellite broadcasting systems and satellite communication systems, right-handed and left-handed circularly polarized waves and horizontal and vertical linearly polarized waves are used for effective use of frequency resources. Thereby, signals for two channels can be transmitted in the same frequency band.

  For example, in a satellite broadcasting system, as shown in FIG. 5, a digital signal is transmitted from a transmission device 1 to a repeater 2 of a real satellite using right-handed and left-handed circularly polarized waves. This digital signal is relayed and transmitted to the receiving device 3. The receiving device 3 includes a demodulation processing unit 31 and a decoding processing unit 32. The demodulation processing unit 31 receives a channel selection signal related to a desired channel from the decoding processing unit 32 side, receives a modulated wave having a polarization corresponding to the channel, and first demodulates and decodes a transmission control signal (TMCC signal). Then, the desired wave (main signal) is demodulated from the polarized modulated wave received according to the transmission control signal (TMCC signal), and the demodulated desired wave (main signal) is output to the decoding processing unit 32 together with the corresponding TMCC signal. To do. The decoding processing unit 32 performs decoding processing on the desired wave demodulated by the decoding processing unit 32 based on the control information (coding rate or the like) of the TMCC signal, and restores the digital signal.

  As an aspect in which a digital signal is transmitted using such a plurality of types of polarized waves, an individual channel number is shown and described in order to enhance the understanding, as shown in FIG. The digital signal is transmitted in a frequency band in which the right-handed circularly polarized wave of the channel and the left-handed circularly polarized wave of the even channel cross each other, and the frequency of the right-handed circularly polarized wave of the odd-numbered channel as shown in FIG. It is possible to transmit an even channel left-hand circularly polarized digital signal in a frequency band different from the band.

  In general, the odd-numbered channel right-handed circularly polarized wave and even-numbered channel left-handed circularly polarized wave shown in FIG. 6 are encoded and modulated with different modulation schemes (and different coding rates). Thus, the right-handed circularly polarized wave of the odd channel can be configured to have a lower required C / N (Carrier to Noise) than the left-handed circularly polarized wave of the even-numbered channel. An individual modulation scheme and coding rate can be arbitrarily set for each channel.

  6A and 6B, the cross polarization may be an interference wave with respect to the desired wave of the desired channel, and the level difference between the desired wave and the cross polarization is calculated. The cross polarization discrimination degree (XPD: Cross Polarization Discrimination) of an antenna for receiving satellite broadcasts in a general home is about 20 dB in fine weather.

  In the broadcasting system ISDB-S (Integrated Services Digital Broadcasting for Satellite) used in the current BS (Broadcasting Satellite) digital broadcasting and broadband CS (Communications Satellite) digital broadcasting, the modulation scheme TC8PSK (Trellis Coded 8 Phase-Shift) Keying), coding rate 2/3 is adopted, and the required C / N is 10.7 dB.

  On the other hand, as a transmission method for an ultra-high-definition television service, which is a high-quality service exceeding HDTV (High-definition television), it is based on the transmission channel coding method of the advanced broadband satellite digital broadcasting of the standard ARIB STD-B44. The use of the modulation method 16APSK (Amplitude and Phase-Shift Keying) has been studied (for example, see Non-Patent Document 1). 8K Super Hi-Vision, an ultra-high-definition television service, is assumed to have a transmission speed of about 100 Mbps, and the required C / N of 16APSK corresponding to the transmission speed is 12 dB or more. / N is about 18 dB.

Information and Communication Council, Ministry of Internal Affairs and Communications, “Information and Communication Technology Subcommittee (101st) Handouts, Summary of Meetings, Minutes (Document 101-3-1 Broadcast System Committee Report, Document 101-3-2 Broadcast System Committee) Report, Document 101-3-3 Report (Draft) ”, [online], March 25, 2014, Broadcasting System Committee, [Search June 4, 2014], Internet <URL: http: / /www.soumu.go.jp/main_content/000282014.pdf>, <URL: http://www.soumu.go.jp/main_content/000282016.pdf>, <URL: http: //www.soumu.go .jp / main_content / 000282017.pdf>

  As described above, in the satellite broadcasting system, as shown in FIG. 5, the digital signal is transmitted from the transmission device 1 to the repeater 2 of the actual satellite using the right-handed and left-handed circularly polarized waves, and the repeater 2 relays this digital signal and transmits it to the receiver 3. The signal input to the receiving device 3 is C / (N + I) [dB] by adding the interference component I and the noise component N to the desired wave C [dB]. The relationship between C / (N + I) and C / N [dB] and C / I [dB] is expressed by the following equation.

  As expressed by the above formula, when the cross polarization discrimination (XPD) is small, C / I becomes small. Therefore, C / (N + I) when cross polarization exists is small, and the required C / N is reduced. The margin of reception C / N (reception margin of the desired wave) becomes small.

  Also, when different encoding / modulation schemes (different coding rates and / or different modulation schemes) are used for each channel using right-handed and left-handed circularly polarized waves, the required C / N will be different. When the required C / N of the cross polarization is less than or equal to the required C / N of the desired wave, the reception margin of the desired wave is smaller than the reception margin of the cross polarization, so that the cross polarization can be received well. Even in a difficult environment, the influence of the cross-polarized interference component appearing in the received signal of the desired wave becomes so large that it cannot be ignored, and the required C / N of the desired wave is deteriorated.

  Therefore, when the required C / N of the cross polarization is equal to or less than the required C / N of the desired wave, when interference due to the cross polarization occurs in the desired wave, the required C / N for the desired wave having a high required C / N. A technique for suppressing deterioration is desired.

  In view of the above-described problems, an object of the present invention is to provide a cross-polarization interference canceller that removes cross-polarization interference components when receiving digital signals transmitted using multiple types of polarization. There is.

  The cross polarization interference cancellation apparatus of the present invention supports cross polarization from a received signal when a coding / modulation method having a required C / N lower than the desired wave is used for the cross polarization that is an interference wave. The received signal is demodulated, re-modulated, added with transmission path distortion whose interference component is estimated, and then subtracted from the received signal to obtain a desired wave.

  That is, the cross polarization interference canceller of the present invention is a cross polarization interference canceller that removes cross-polarization interference components when receiving a digital signal transmitted using a plurality of types of polarization. Distribution means for distributing received digital signals of plural kinds of polarization signals to desired waves and cross polarization signals; and cross polarization signals for processing the cross polarization signals and generating replica signals of interference components for the desired waves A processing unit compares a required C / N value determined in advance with respect to the coding / modulation information from the coding / modulation information of the desired wave and the cross polarization, and When the required C / N of the wave is determined to be less than or equal to the required C / N of the desired wave, the required C / N determination control for controlling the cross polarization processing means to generate a replica signal of the interference component And a replica of the interference component from the signal of the desired wave Signal subtraction to, characterized in that it comprises a desired signal processing means for demodulating.

  In the cross polarization interference cancellation apparatus of the present invention, the digital signal is transmitted as a broadcast wave using a plurality of types of polarization.

  Further, in the cross polarization interference canceling apparatus of the present invention, the cross polarization processing means is configured to obtain a replica signal of each of the interference components with respect to the desired wave with respect to cross polarizations in a plurality of predetermined different frequency bands. It is comprised so that it may generate | occur | produce.

  In the cross polarization interference cancellation apparatus of the present invention, when the required C / N determination control means determines that the required C / N of the cross polarization is not less than or equal to the required C / N of the desired wave, The desired wave processing means is controlled to demodulate the signal of the desired wave distributed by the distributing means.

  Further, in the cross polarization interference cancellation apparatus of the present invention, the cross polarization processing means adds transmission path distortion by estimating a transmission path response accompanying equalization processing using a pilot signal of each cross polarization, and A replica signal of an interference component for a desired wave is generated.

  According to the present invention, when the desired wave has an encoding / modulation scheme that has a required C / N higher than the cross polarization, it is possible to suppress the required C / N degradation for the desired wave.

  That is, when the desired wave has a required C / N higher than the cross polarization, the reception margin of the desired wave is smaller than that of the cross polarization, but even in such a case, the cross polarization interference cancellation according to the present invention is performed. By providing the apparatus in the receiving apparatus instead of the existing modulation processing unit, it is possible to effectively suppress the influence of interference due to cross polarization and improve the receiving performance of the receiving apparatus.

It is a block diagram which shows schematic structure of the cross polarized-wave interference cancellation apparatus of one Embodiment by this invention. It is a figure which shows an example of the cross polarization in which the interference component by the desired wave input into the cross polarization process part in the cross polarization interference removal apparatus of one Embodiment by this invention was superimposed. It is a figure which shows an example of the desired wave with which the interference component by a cross polarized wave input into the desired wave process part in the cross polarization interference removal apparatus of one Embodiment by this invention was superimposed. It is a figure which shows an example of the required C / N table utilized with the cross polarization interference cancellation apparatus of one Embodiment by this invention. It is a figure which shows schematic structure of a satellite broadcast system. (A), (B) is a figure which shows the example of the aspect which transmits a digital signal using multiple types of polarization.

  Hereinafter, a cross polarization interference cancellation device 5 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a cross polarization interference cancellation device 5 according to an embodiment of the present invention. The cross polarization interference cancellation device 5 can be installed in place of the demodulation processing unit 31 of the reception device 3 in the satellite broadcasting system shown in FIG. Therefore, as in the conventional case, the digital signal is transmitted from the transmitter 1 to the repeater 2 of the actual satellite using the right-handed and left-handed circularly polarized waves, and the repeater 2 relays this digital signal. Transmit to the receiver 3. Here, the receiving device 3 includes a cross polarization interference removing device 5 and a decoding processing unit 32. The cross polarization interference cancellation apparatus 5 receives a channel selection signal related to a desired channel from the decoding processing unit 32 side, receives a modulated wave of the polarization corresponding to the channel, and first transmits a transmission control signal (TMCC signal). Demodulate / decode, demodulate desired wave (main signal) from modulated wave of polarization received according to transmission control signal (TMCC signal), and decode demodulated desired wave (main signal) together with corresponding TMCC signal 32. The decoding processing unit 32 performs decoding processing on the desired wave demodulated by the decoding processing unit 32 based on the control information (coding rate or the like) of the TMCC signal, and restores the digital signal.

  Here, the cross polarization interference removal apparatus 5 is configured to remove cross polarization interference components when receiving digital signals transmitted using a plurality of types of polarization. Hereinafter, with reference to FIG. 1, the cross polarization interference cancellation apparatus 5 of one Embodiment is demonstrated in detail.

  As shown in FIG. 1, the cross polarization interference canceling device 5 receives a plurality of types of polarization digital signals received by the receiving antenna 5a, and distributes the cross polarization interference components with respect to the desired wave. And 50, 51, a first cross polarization processing unit 52, a second cross polarization processing unit 53, a desired wave processing unit 54, a required C / N determination control unit 55, and a channel control unit 56. The first cross polarization processing unit 52 and the second cross polarization processing unit 53 are respectively TMCC decoding units 520 and 530, demodulation processing units 521 and 531, decoding processing units 522 and 532, encoding processing units 523 and 533, and modulation. Processing units 524 and 534 and transmission path distortion addition units 525 and 535 are provided. The desired wave processing unit 54 includes a delay processing unit 541, a subtraction processing unit 542, a demodulation processing unit 543, and a TMCC decoding unit 544.

  First, the channel control unit 56 receives a channel selection signal related to a desired channel from the decoding processing unit 32 side, sets a band corresponding to the channel selection signal as a desired wave, and cross-balances a band that can be an interference component of the desired wave. Waves (in this example, two cross-polarized waves) are used, and distributors 50 and 51 are controlled so as to distribute digital signals of a plurality of types of polarized waves received by receiving antenna 5a for the desired wave and the two cross-polarized waves. . At the same time, the channel control unit 56 outputs information indicating that the desired wave and the two cross polarized waves are distributed to the required C / N determination control unit 55.

  The distributor 50 desires a signal of a desired wave among digital signals of a plurality of types of polarization received by the reception antenna 5a with a predetermined cross polarization discrimination degree (cross polarization discrimination degree mainly depending on the antenna 5a). The power is distributed to the wave processing unit 54, and the signal including the two cross-polarized bands is distributed to the distributor 51.

  The distributor 51 has a predetermined cross polarization discrimination degree (a cross polarization discrimination degree mainly depending on the antenna 5a) and separates signals including the bands of the two cross polarization bands obtained from the distributor 50 into individual cross polarizations. Each of the two cross-polarized signals is distributed to the first cross-polarized wave processing unit 52 and the second cross-polarized wave processing unit 53 so as to be a wave signal.

  For example, referring to the example of FIG. 6A, for the channel number (2n-1) of the desired wave (n is an integer of 1 or more), the band that can be an interference component of the desired wave is the channel number. Assuming that (2n-2) and the channel number (2n), as shown in FIG. 2, the cross-polarized signal w1 of the channel number (2n-2) is input to the first cross-polarization processing unit 52, The two cross polarization processing unit 53 receives the cross polarization signal w2 of the channel number (2n). At this time, each cross-polarized signal distributed by the distributor 51 has a predetermined cross-polarization discrimination (cross-polarization discrimination mainly depending on the antenna 5a) and a power amplitude larger than the desired wave. The desired wave components are input to the first cross polarization processing unit 52 and the second cross polarization processing unit 53 in a manner in which the desired wave components interfere with each other.

  As shown in FIG. 3, the desired wave signal w0 distributed by the distributor 50 has a predetermined cross polarization discrimination degree (a cross polarization discrimination degree mainly depending on the antenna 5a) and The power amplitude is larger than that of the polarization, and the two cross-polarization components interfere with each other and are input to the desired wave processing unit 54.

  The first cross polarization processing unit 52 and the second cross polarization processing unit 53 receive the respective cross polarization signals w1 and w2, and first, the demodulation processing units 521 and 531 perform the cross polarization signal w1 and w2, respectively. The TMCC signal multiplexed separately from each main signal of w2 is demodulated, and then TMCC signals are decoded by the TMCC decoding units 520 and 530.

  Further, the desired wave processing unit 54 receives the desired wave signal w0, and first, the demodulation processing unit 543 demodulates the TMCC signal multiplexed separately from the main signal of the desired wave signal w0. The TMCC signal is decoded by the TMCC decoding unit 544. At this time, the delay processing unit 541 delays the desired wave signal w0 by a delay amount corresponding to the processing time of the first cross polarization processing unit 52 and the second cross polarization processing unit 53, but the desired wave signal w0. This does not affect the demodulation and decoding of the TMCC signal multiplexed in the.

  The subtraction processing unit 542 operates to subtract the interference component obtained from the first cross polarization processing unit 52 and the second cross polarization processing unit 53 from the desired wave signal. There is no input from the first cross polarization processing unit 52 and the second cross polarization processing unit 53, or a null value signal is input, which does not affect the demodulation and decoding of the TMCC signal. Note that the TMCC signal uses, for example, a modulation system BPSK (Binary Phase-Shift Keying) in ISDB-S and a modulation system π / 2 shift BPSK in ARIB STD-B44, which is lower than the main signal. It is possible to receive without error by C / N.

  The required C / N determination control unit 55 acquires and compares the information on the encoding / modulation methods included in the TMCC signals of the desired wave and the two cross polarizations from the TMCC decoding units 520, 530, and 544, and performs cross-polarization. Confirm that the required C / N of the wave is less than or equal to the required C / N of the desired wave. When this condition is satisfied, the required C / N determination control unit 55 determines that the interference component for the desired wave is so large that it cannot be ignored, and the interference component by the first cross polarization processing unit 52 and the second cross polarization processing unit 53 is determined. The TMCC decoding units 520, 530, and 544 are instructed to perform the generation operation of and the interference wave removal operation from the desired wave by the desired wave processing unit 54. In response to this instruction, the TMCC decoding units 520, 530, and 544 send control signals for controlling the operations of the first cross polarization processing unit 52, the second cross polarization processing unit 53, and the desired wave processing unit 54 to the respective units. Supply.

  In order to confirm that the required C / N of the cross polarization is equal to or less than the required C / N of the desired wave, the required C / N determination control unit 55 uses, for example, FIG. It is preferable to hold a table indicating the required C / N values associated with the relationship between the modulation scheme and the coding rate as shown in FIG. The required C / N value stored in the table is preferably a value that matches the actual transmission method, but does not require strictness. Therefore, instead of holding the table, a simple formula that can obtain the required C / N value associated with the relationship between the modulation scheme and the coding rate may be determined and held.

  On the other hand, the required C / N determination control unit 55 acquires and compares the information on the encoding / modulation method included in each TMCC signal of the desired wave and the two cross polarizations from the TMCC decoding units 520, 530, and 544, When the required C / N of the cross polarization is not less than or equal to the required C / N of the desired wave, the TMCC decoding units 520 and 530 are configured to perform the same operation as the existing demodulation process (for example, the demodulation processing unit 31 shown in FIG. 5). , 544. In response to this instruction, the TMCC decoding units 520, 530, and 544 send control signals for controlling the operations of the first cross polarization processing unit 52, the second cross polarization processing unit 53, and the desired wave processing unit 54 to the respective units. Supply. In this case, the desired wave processing unit 54 operates so that the demodulation processing unit 543 performs a demodulation process on the desired wave. At this time, the arithmetic processing unit 542 is configured such that there is no input from the first cross polarization processing unit 52 and the second cross polarization processing unit 53, or a null value signal is input, and the main signal of the desired wave is input. It operates so as not to affect the demodulation and decoding of the signal.

  Hereinafter, an operation when the required C / N of the cross polarization is equal to or less than the required C / N of the desired wave will be described. Each of the first cross polarization processing unit 52 and the second cross polarization processing unit 53 demodulates the input cross polarization main signal by the demodulation processing units 521 and 531 based on the information of each TMCC signal. After that, the decoding processing units 522 and 532 perform error correction decoding processing.

  Subsequently, each of the first cross polarization processing unit 52 and the second cross polarization processing unit 53 repeats the replica signal of the interference component for the desired wave with respect to the digital signal of the main signal decoded by the decoding processing units 522 and 532. Are generated by the encoding processing units 523 and 533 based on the information of each TMCC signal, and then modulated by the modulation processing units 524 and 534. The transmission path distortion is added to the modulated wave by the transmission path distortion adding sections 525 and 535 by estimating the transmission path response accompanying the equalization processing using the cross-polarized pilot signals, and the interference component for the desired wave. The replica signal is generated. By adding this transmission line distortion, it is possible to generate a replica signal of an interference component for a desired wave with high accuracy.

  In addition, the replica signal is attenuated in power corresponding to a predetermined cross polarization discrimination (a cross polarization discrimination mainly depending on the antenna 5a) so as to be equal to the power amplitude of the interference component with respect to the desired wave. And output from each of the first cross polarization processing unit 52 and the second cross polarization processing unit 53. In order to realize this power attenuation, a predetermined attenuation amount may be set, or it may be configured to be settable from the outside according to the antenna 5a to be used. Also, a cross-polarization power ratio calculation unit that obtains a cross-polarization power ratio between the desired wave and the cross-polarization based on a transmission path response using a pilot signal obtained by demodulating each of the desired wave and the cross-polarization (Not shown) may be provided in the cross polarization interference canceller 5 so that the amount of attenuation is added based on the obtained cross polarization power ratio.

  As described above, each of the first cross polarization processing unit 52 and the second cross polarization processing unit 53 generates a replica signal of an interference component for the desired wave according to the modulation / coding method of each cross polarization. . Therefore, in this example, two replica signals of interference components for the desired wave are generated.

  That is, the replica signal generated by the transmission path distortion adding units 525 and 535 has a power amplitude substantially equal to the cross polarization interference components w1 and w2 for the desired wave w0 shown in FIG. The signal is input to the subtraction processing unit 542 of the desired wave processing unit 54.

  On the other hand, in the desired wave processing unit 54, a delay amount corresponding to the processing time of the first cross polarization processing unit 52 and the second cross polarization processing unit 53 is input to the desired wave input from the distributor 50 by the delay processing unit 541. The subtraction processing unit 542 inputs the replica signal obtained from the transmission path distortion adding units 525 and 535, and subtracts the replica signal from the desired wave signal.

  In this way, the cross-polarization interference canceller 5 according to the present embodiment suppresses the cross-polarization interference component when the cross-polarization required C / N is equal to or less than the desired C / N of the desired wave. A wave signal (main signal) can be obtained.

  The desired wave signal (main signal) from which the cross polarization interference component has been removed by the subtraction processing unit 542 is demodulated by the demodulation processing unit 543 based on the information of the TMCC signal. The demodulation processing unit 543 outputs the main signal of the desired wave together with the TMCC signal to the decoding processing unit 32 (see FIG. 5).

  Based on the information of the TMCC signal, the decoding processing unit 32 decodes the main signal of the desired wave in a decoding process corresponding to the error correction encoding process of the transmission apparatus 1.

  Therefore, according to the cross polarization interference cancellation apparatus 5 of the present embodiment, when the desired wave has a required C / N that is higher than the cross polarization, the required C / N degradation with respect to the desired wave. Can be suppressed. In particular, when a modulation method and a coding rate having a large required C / N are used for the desired wave, the reception margin becomes smaller, so that the operation and effect of the cross polarization interference cancellation apparatus 5 of the present embodiment becomes larger. It is possible to effectively suppress the influence of interference caused by cross polarization.

  The present invention should not be construed as limited by the above-described embodiments, but only by the claims. For example, right-handed and left-handed circularly polarized waves have been described as examples, but the present invention can also be applied to a mode using horizontal polarization and vertical polarization. Further, the present invention can also be applied to an aspect using a right-slanted 45 ° polarized wave and a left-slanted 45 ° polarized wave.

  In the description of the above-described embodiment, an example in which two interference wave component replica signals are generated for two types of polarization has been described. However, one or more interference wave component replica signals may be generated. Can do.

  According to the present invention, when the desired wave is a coding / modulation system having a required C / N higher than the cross polarization, the required C / N deterioration for the desired wave can be suppressed. This is useful for removing cross-polarization interference components related to waves.

DESCRIPTION OF SYMBOLS 1 Transmission apparatus 2 Repeater 3 Reception apparatus 5 Cross polarization interference removal apparatus 5a Reception antenna 31 Demodulation process part 32 Decoding process part 50,51 Divider 52 1st cross polarization process part 53 2nd cross polarization process part 54 Hope Wave processing unit 55 Required C / N determination control unit 56 Channel control unit 520, 530 TMCC decoding unit 521, 531 Demodulation processing unit 522, 532 Decoding processing unit 523, 533 Encoding processing unit 524, 534 Modulation processing unit 525, 535 Transmission Path distortion adding unit 541 Delay processing unit 542 Subtraction processing unit 543 Demodulation processing unit 544 TMCC decoding unit

Claims (5)

A cross polarization interference canceller that removes cross polarization interference components when receiving a digital signal transmitted using multiple types of polarization,
Distributing means for distributing the received digital signal of multiple types of polarization to the desired wave and cross polarization,
Cross-polarization processing means for processing the cross-polarized signal to generate a replica signal of an interference component for the desired wave;
Based on the information on the coding / modulation method of the desired wave and the cross polarization, a predetermined required C / N value is compared with the information on the coding / modulation method, and the required C of the cross polarization is calculated. When it is determined that / N is equal to or less than the required C / N of the desired wave, the required C / N determination control unit controls the generation of a replica signal of the interference component by the cross polarization processing unit;
Desired wave processing means for subtracting and demodulating the replica signal of the interference component from the desired wave signal;
A cross polarization interference cancellation apparatus comprising:   The cross polarization interference canceling apparatus according to claim 1, wherein the digital signal is transmitted as a broadcast wave using a plurality of types of polarized waves.   The cross polarization processing means is configured to generate a replica signal of each interference component for cross polarizations in a plurality of predetermined different frequency bands with respect to the desired wave. The cross polarization interference canceller according to claim 1 or 2.   When the required C / N determination control means determines that the required C / N of the cross polarization is not less than or equal to the required C / N of the desired wave, the required C / N determination control means outputs the desired wave signal distributed by the distributing means. The cross polarization interference cancellation apparatus according to claim 1, wherein the desired wave processing means is controlled to demodulate.   The cross polarization processing means generates a replica signal of an interference component for the desired wave by adding a transmission line distortion by estimating a transmission line response accompanying an equalization process using a pilot signal of each cross polarization. The cross-polarization interference canceller according to any one of claims 1 to 4, wherein the cross-polarization interference canceller is characterized by the following.