JP2020053787A - Wireless communication device - Google Patents

Abstract

To provide a wireless communication device that can calculate an effective and practical reception margin value in all areas from the vicinity of a reception limit point to an area where a C/N value is high and the reception condition is relatively good in reception margin calculation using a bit error rate.SOLUTION: A wireless communication device is used in a wireless communication system that modulates an error correcting digital signal composed of a combination of a predetermined error correcting inner code and an error correcting outer code into a predetermined modulation method and transmits the modulated signal. The wireless communication device includes a RAW-BER calculation unit that calculates a bit error rate (RAW-BER) before error correcting inner decoding from a signal before and after error correcting inner decoding, a BER calculation unit that calculates a bit error rate (BER) before error correcting outer decoding from a signal before and after error correcting outer decoding, and a margin calculation unit that calculates a reception margin value on the basis of the RAW-BER value calculated by the RAW-BER calculation unit and the BER value calculated by the BER calculation unit.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a wireless communication device, and is applicable to, for example, a digital wireless communication device having a unit for calculating a margin (reception margin) of a transmission path state.

In a conventional digital wireless transmission system, a reception limit point (for example, BER (Bit Error Rate (bit error rate)) determined by a modulation method and an error correction code capability: C / N (Carrier to carrier) corresponding to 1 × 10 ^−4. Noise (carrier-to-noise)) ratio), there is a reception margin as an index for grasping how much margin is being received in a line state. Here, the digital wireless communication system is, for example, digital terrestrial broadcasting or digital FPU. An FPU (Field Pickup Unit) is a wireless relay transmission device for television broadcasting.

  As a method for calculating the reception margin, there is a method using bit error rate information. It is a method of calculating an error rate from the number of data corrected by error correction inner decoding or error correction outer decoding, and obtaining a line state (equivalent to a reception margin value) from the value and a C / N conversion table stored in advance. (Patent Documents 1 and 2).

  Patent Literature 1 compares a signal before and after an error correction inner decoding unit to obtain a BER (hereinafter, RAW-BER) value of a signal input to the error correction inner decoding unit, and obtains the value and a C / C value stored in advance. It is characterized in that a margin value for a limit point is calculated from a conversion table of N vs. RAW-BER characteristics.

  Patent Literature 2 compares a signal before and after an error correction outside decoding unit to obtain a BER value of a signal input to an error correction inside decoding unit, and converts the value into a C / N to BER characteristic conversion table stored in advance. It is characterized by calculating a margin value with respect to the reception limit point.

JP-A-2006-128841 JP 2003-23070 A

ARIB STB-B11 Portable microwave digital radio transmission system for television broadcast program material transmission ARIB STB-B33 Portable OFDM Digital Wireless Transmission System for Television Broadcast Program Material Transmission ARIB STB-B57 Portable OFDM digital wireless transmission system for 1.2GHz / 2.3GHz band television broadcast program material transmission

  The method of calculating the reception margin from the C / N vs. RAW-BER characteristics of Patent Document 1 is effective in calculating the margin in an area where the C / N value is high and the reception state is relatively good, but the C / N value is low. This is not a sufficiently effective method for calculating a margin near the reception limit point (reception margin 0 dB) because the characteristic curve is saturated.

  Further, in the method of calculating the reception margin from the C / N versus BER characteristics in Patent Document 2, the C / N value is low and is effective in calculating the margin near the reception limit point (reception margin 0 dB). It is not practical to calculate a margin in a region having a high value and a relatively good reception state because of lack of real-time property.

  According to the present disclosure, in a reception margin calculation using a bit error rate, an effective and practical reception margin value in all areas from a vicinity of a reception limit point (reception margin 0 dB) to a region having a high C / N value and a relatively good reception state. It is an object of the present invention to provide a wireless communication device capable of calculating the following.

The following is a brief description of an outline of a typical one of the present disclosure.
That is, the wireless communication device is used in a wireless communication system that modulates an error-corrected digital signal composed of a combination of a predetermined error-correcting inner code and an error-correcting outer code into a predetermined modulation method and transmits the modulated signal. The wireless communication apparatus includes: a RAW-BER calculating unit that calculates a bit error rate (RAW-BER) before error-correction decoding from signals before and after error-correction decoding; And a margin calculation unit that calculates a reception margin value based on the RAW-BER value calculated by the RAW-BER calculation unit and the BER value calculated by the BER calculation unit. And.

  According to the wireless communication apparatus, it is possible to calculate an effective and practical reception margin in all areas from around the reception limit point (reception margin 0 dB) to a region where the C / N value is high and the reception state is relatively good. Become.

FIG. 1 is a diagram illustrating a configuration of a wireless communication device according to an embodiment. FIG. 4 is a diagram illustrating an example of a reception margin versus a RAW-BER characteristic and a reception margin versus a BER characteristic shared by each modulation scheme according to the embodiment. 6 is a diagram illustrating an example of a conversion table of a reception margin versus a BER characteristic and a reception margin versus a RAW-BER characteristic according to the embodiment; FIG. 8 is a diagram illustrating an example of margin calculation by switching control of the reception margin and the BER characteristic and the reception margin and the RAW-BER characteristic according to the embodiment; FIG. FIG. 4 is a diagram showing an example of C / N vs. RAW-BER characteristics before decoding inside an error correction and C / N vs. BER characteristics before decoding outside an error correction in a digital FPU.

  First, the C / N vs. RAW-BER characteristics and the C / N vs. RAW-BER characteristics will be described with reference to FIG. FIG. 5 is a diagram showing an example of C / N vs. RAW-BER characteristics before error correction inner decoding and C / N vs. BER characteristics before error correction inner decoding in digital FPUs described in Non-Patent Documents 1 to 3. is there.

  In FIG. 5, Viterbi decoding is used as the inner error correction decoding, and Reed-Solomon decoding is used as the outer error correction decoding. The convolutional coding rate is 1/2, and the modulation method is C / N versus RAW- in each of 64 QAM, 32 QAM, and 16 QAM. The BER characteristic curve (E) and the C / N vs. BER characteristic curve (F) are described.

The C / N vs. RAW-BER characteristic is characterized by a saturation curve as the error rate increases. In particular, the BER value, which is the limit point of the most important error-correction outside decoding (Reed-Solomon decoding), is 1 × 10 ^{−1 of} the RAW-BER characteristic curve (E) corresponding to around 1 × 10 ⁻⁴ (reception margin: 0 dB). Since there is almost no slope of the curve in the above area (slope saturation area (G)), it is a very critical area to convert the detected RAW-BER value to C / N (for example, 1 dB step). , Not a valid indicator.

The C / N vs. BER characteristics before error-correction-out decoding has a linear slope, but since the BER value, which is the limit point of Reed-Solomon decoding, is 1 × 10 ⁻⁴ points (reception margin: equivalent to 0 dB), an error has occurred. Until a point less than 1 × 10 ⁻⁹ that can be determined as free, there is a feature that there is only a narrow area of about 4 dB in C / N value.

  Further, as can be said with respect to both the C / N vs. RAW-BER characteristic curve (E) and the C / N vs. BER characteristic curve (F), even if different modulation modes such as 64 QAM, 32 QAM, and 16 QAM are used, the relative When viewed from the viewpoint, the slope of each characteristic curve with respect to the C / N value is substantially the same.

As shown in FIG. 5, the C / N vs. RAW-BER characteristic has such a curve that a curve near a BER value: 1 × 10 ⁻⁴ point (reception margin: 0 dB), which is the most important reception limit point, is saturated. Therefore, Patent Document 1 cannot be said to be a sufficiently effective method for calculating the reception margin.

As shown in FIG. 5, the C / N vs. BER characteristic before decoding outside error correction has a linear slope, but a BER value which is a limit point of Reed-Solomon decoding: 1 × 10 ⁻⁴ points (receiving Since the C / N value is only about 4 dB from the margin of 0 dB) to less than 1 × 10 ^{−9 at} which it can be determined to be error-free, it is difficult to calculate the margin of 5 dB or more in Patent Document 2. Here, by calculating a BER characteristic of less than 1 × 10 ^−9, it is possible to detect a margin of 5 dB or more. For example, to calculate 1 × 10 ⁻¹⁰ , the number of data samples is ^1/1 × 10 ^{−. 10} = 10 ¹⁰ pieces are required. Even receiving the number of data samples requires a few seconds and is not an effective method because real-time performance is lost. Generally, it is usually determined that the error is less than 1 × 10 ⁻⁹ as error-free (no error).

  In addition, Patent Document 2 discloses a method of obtaining amplitude information of digitally demodulated I / Q mapping points, and obtaining a line state (equivalent to a reception margin value) from the value and a C / N conversion table stored in advance. I have. In this system, when preparing a C / N ratio conversion table corresponding to each amplitude information of an I / Q mapping point, a conversion table is prepared for each modulation system such as 64QAM, 32QAM, 16QAM, QPSK, and BPSK. There is a need. Further, in addition to the above-described modulation schemes, the reception limit point varies depending on the error correction code rate such as 1/2, 2/3, 3/4, and 5/6. It is necessary to prepare a conversion table of the combination of the combinations, and there is a problem that the circuit scale tends to be large.

  Hereinafter, embodiments will be described with reference to the drawings. However, in the following description, the same components will be denoted by the same reference symbols, and repeated description may be omitted.

FIG. 1 is a diagram illustrating a configuration of the wireless communication device according to the embodiment.
The wireless communication device 10 according to the embodiment includes a receiving antenna 1, a down converter 2, a digital demodulator 3, a Viterbi decoder 4, a RAW-BER calculator 5, a Reed-Solomon decoder 6, and a BER calculator. 7 and a margin calculator 8.

  The receiving antenna 1 receives a digital signal transmitted from a digital transmitting device (not shown). The digital signal is, for example, error-corrected from a combination of a predetermined error-correcting inner code such as a Viterbi code (convolutional code) and an error-correcting outer code such as a Solomon code from a digital FPU described in Non-Patent Documents 1 to 3. Applied OFDM modulation signal or single carrier QAM modulation signal.

  The down-converter unit 2 converts a digital signal received by the receiving antenna 1 into a baseband signal of a predetermined level (for example, a 130 MHz band signal) by performing frequency conversion processing, AGC control, and the like. The digital demodulation unit 3 digitally demodulates the baseband signal and converts it into an I / Q signal.

  The Viterbi decoding unit 4 outputs data obtained by subjecting the I / Q signal to intra-error-correction decoding processing. The Reed-Solomon decoding unit 6 further performs an error-correction-out decoding process on the data subjected to the error-correction-in decoding, and outputs an original coded video / audio signal. Actually, processes such as deinterleaving and energy despreading are included before and after the Viterbi decoding unit 4 and the Reed-Solomon decoding unit 6, but are omitted.

  The RAW-BER calculation unit 5 calculates a bit error rate (RAW-BER) of the I / Q signal input to the Viterbi decoding unit 4 before error correction. More specifically, the data obtained by subjecting the data corrected by the Viterbi decoding unit 4 to the error correction inner coding process again and the I / Q signal input to the Viterbi decoding unit 4 are delayed by a predetermined time. By comparing the data with the phase-adjusted data, it is possible to detect data that has been error-corrected by the Viterbi decoding unit 4. The RAW-BER can be calculated by counting the number of error-corrected data for a predetermined period and dividing the counted number by the total number of data received in the same period.

  The BER calculator 7 calculates the bit error rate (BER) of the data after performing the error correction inner decoding (Viterbi decoding) input to the Reed-Solomon decoder 6. More specifically, the data corrected by the Reed-Solomon decoding and the data input to the Reed-Solomon decoding unit 6 are delayed by a predetermined time and phase-adjusted, so that the Reed-Solomon decoding unit 6 compares the data. Error-corrected data can be detected. The BER can be calculated by counting the number of error-corrected data for a predetermined period and dividing the counted number by the total number of data received in the same period.

  Next, the margin calculator 8 will be described. The margin calculator 8 calculates a margin value from the RAW-BER and the BER information thus obtained.

In the present embodiment, the C / N vs. RAW-BER characteristics before decoding inside the error correction and the C / N vs. BER characteristics before decoding outside the error correction shown in FIG. 5 are different modulation modes such as 64 QAM, 32 QAM and 16 QAM. However, since there is a characteristic that the slope of the characteristic curve with respect to C / N has relatively the same characteristic, they are considered to be equivalent. More specifically, a C / N conversion table from a RAW-BER value and a BER value based on a C / N value corresponding to a reception margin: 0 dB (BER: 1 × 10 ⁻⁴ points) is shared, and a circuit is used. The scale can be reduced.

FIG. 2 is a diagram illustrating an example of a reception margin vs. RAW-BER characteristic and a reception margin vs. BER characteristic shared by each modulation scheme according to the embodiment. A reception limit point (BER value: C / N value corresponding to 1 × 10 ⁻⁴ ) is defined as a 0 dB margin (C), and a margin value (margin) converted therefrom is converted into C / N (1 dB step). It is a graph with the horizontal axis. As described above, the circuit scale is reduced by using a common conversion table corresponding to the reception margin versus BER characteristic curve (A) and the reception margin versus RAW-BER characteristic curve (B) in each modulation scheme.

  FIG. 3 is a diagram illustrating an example of a conversion table of the reception margin versus the BER characteristic and the reception margin versus the RAW-BER characteristic according to the embodiment. FIG. 3 is a table showing a reception margin versus BER characteristic curve (A) and a reception margin versus RAW-BER characteristic curve (B) in FIG. 2.

In FIG. 2, as described above, the reception margin versus BER characteristic curve (A) has a linear slope, but corresponds to the switching control point (D) from the margin 0 dB (C) which is the limit point of Reed-Solomon decoding. There is a narrow area of about 4 dB up to a point of less than 1 × 10 ⁻⁹ that can be judged as error-free, and the margin calculation of a larger area is not practical because of lack of real-time property. Also, the reception margin versus RAW-BER characteristic curve (B) becomes a saturation curve as the error rate increases, and thus corresponds to a margin 0 dB point (C) corresponding to a reception limit point to a switching control point (D). There is almost no slope of the characteristic curve up to a margin of 4 dB, and converting the detected RAW-BER value to C / N (for example, in 1 dB steps) is a very critical area, and cannot be said to be an effective means. .

  In the present embodiment, the reception margin is calculated effectively by switching the reception margin vs. BER characteristic curve (A) and the reception margin vs. RAW-BER characteristic curve (B) under predetermined conditions.

  FIG. 4 is a diagram illustrating an example of calculating a margin by the switching control of the reception margin versus the BER characteristic and the reception margin versus the RAW-BER characteristic according to the embodiment.

The RAW-BER calculator 5 calculates a RAW-BER value, and the BER calculator 7 calculates a BER value (step S1). The margin calculator 8 determines whether the BER value is equal to or greater than 1 × 10 ⁻⁹ (step S2). If it is 1 × 10 ⁻⁹ or more, the BER calculation unit 7 refers to the BER value calculated and the reception margin-to-BER conversion table shown in FIG. 3 (step S3) to calculate the reception margin (step S5). On the other hand, if the difference is less than 1 × 10 ⁻⁹ , the RAW-BER value calculated by the RAW-BER calculation unit 5 and the reception margin-to-RAW-BER conversion table shown in FIG. 3 are referred to (step S4). It is calculated (step S5). Thus, the margin calculation unit 8 can calculate the margin value from the RAW-BER value and the BER value.

The wireless communication apparatus 10 according to the embodiment includes a RAW-BER calculation unit 5 that calculates a RAW-BER before error correction inner decoding from signals before and after error correction inner decoding (Viterbi decoding), and error correction outside decoding (Reed-Solomon decoding). A BER calculator 7 for calculating a BER before error-correction-based decoding from signals before and after, and a reception margin value based on the RAW-BER value calculated by the RAW-BER calculator 5 and the BER value calculated by the BER calculator 7. And a margin calculating unit 8 for calculating. The margin calculation unit 8 includes a RAW-BER conversion table in which reception margin values corresponding to RAW-BER determined by the modulation scheme and the error correction coding rate are stored in advance, and a BER conversion in which reception margin values corresponding to BER are stored in advance. Provide a table. When the BER value calculated by the BER calculation unit 7 is error-free (for example, less than 1 × 10 ⁻⁹ ), the margin calculation unit 8 calculates a reception margin value from the RAW-BER conversion table, and the BER value is not error-free. In the case (for example, 1 × 10 ⁻⁹ or more), a switching means for calculating a reception margin value from a BER conversion table is provided.

  According to the present embodiment, by switching and referencing only an effective area of the reception margin vs. BER characteristic and the reception margin vs. RAW-BER characteristic, the C / N ratio near the reception limit point (reception margin 0 dB) can be obtained. It is possible to calculate an effective and practical reception margin in all areas where the value is high and the reception state is relatively good. Further, in each modulation method, the circuit scale can be reduced by using a common conversion table for the reception margin versus BER characteristic and the reception margin versus the RAW-BER characteristic.

  As described above, the invention made by the present inventor has been specifically described based on the embodiment. However, it is needless to say that the present invention is not limited to the above embodiment and can be variously modified.

DESCRIPTION OF SYMBOLS 1 ... Receiving antenna 2 ... Down converter part 3 ... Digital demodulation part 4 ... Viterbi decoding part 5 ... RAW-BER calculation part 6 ... Reed-Solomon decoding part 7 ... BER calculation Unit 8 Margin calculation unit 10 Wireless communication device

Claims (5)

A wireless communication device used in a wireless communication system that transmits a digital signal subjected to error correction comprising a combination of a predetermined error correction inner code and an error correction outer code by modulating the digital signal into a predetermined modulation method,
A RAW-BER calculation unit that calculates a bit error rate (RAW-BER) before error correction decoding from signals before and after error correction decoding;
A BER calculator for calculating a bit error rate (BER) before error-correction decoding from signals before and after error-correction decoding;
A margin calculation unit that calculates a reception margin value based on the RAW-BER value calculated by the RAW-BER calculation unit and the BER value calculated by the BER calculation unit;
A wireless communication device comprising:   The margin calculator is configured to previously store a RAW-BER conversion table in which a reception margin value corresponding to a RAW-BER determined by the modulation scheme and an error correction coding rate, and a reception margin value corresponding to a BER are stored in advance. A BER conversion table is provided, and the BER value calculated by the BER calculation section is switched to the RAW-BER conversion table and the BER conversion table with a margin value corresponding to error free to calculate a reception margin value. The wireless communication device according to claim 1, wherein:   The wireless communication apparatus according to claim 1, wherein the predetermined error-correcting inner decoding is Viterbi decoding, and the non-error-correcting decoding is Reed-Solomon decoding. The wireless communication device according to claim 2, wherein the error-free BER value is less than 1 × 10 ⁻⁹ .   The wireless communication device according to claim 1, further comprising a down converter unit and a digital demodulation unit.

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