Receiving device, wireless transmission system

Abstract

To enable a user side to perform operation for improving a reception state on the basis of the present reception margin.SOLUTION: A signal quality level calculation section 50 for recognizing a signal quality level of the present reception signal is used, where the recognized signal quality level is a C / N ratio. A reception margin calculation section 70 recognizes a difference between the C / N ratio and a Cn0 as a reception margin and causes the result to be displayed on a display section 80. Further, a transmission parameter calculation section 90 for calculating a transmission parameter and the like for reducing a BER in the present reception state is also provided. The transmission parameter calculation section 90 calculates a reception margin (temporary reception margin) in the case of a transmission parameter (temporary transmission parameter) differing from the present transmission parameter at the present C / N ratio and causes it to be displayed on the display section 80.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a receiving apparatus that receives a digitally modulated signal and a wireless transmission system using this receiving apparatus.

Background Art

[0002] In digital communication, various encoding processes are performed so that digital signals are transmitted without error regardless of the reception state. By this encoding process, even when some bits of the digital signal cannot be accurately recognized due to a poor reception state, error correction processing is performed and the original digital signal is accurately decoded. However, there are cases where the reception state deteriorates to such an extent that decoding by such error correction processing cannot be performed. Since the reception state changes moment by moment, it is important to recognize how different the current reception state is (how much reception margin there is) compared to the state at the limit point (reception limit point) where accurate decoding cannot be performed, even if accurate decoding is being performed in the current reception state.

[0003] Patent Document 1 describes a receiving apparatus that can appropriately display such a reception margin. When the actual reception state (C / N ratio: carrier-to-noise ratio) changes, the change in BER (bit error rate) is steep, so in fact, the change in this reception margin is also steep and difficult to recognize. In this technology, an amount called virtual BER, which corresponds to the actual BER but has a more gradual change, is introduced, and the reception margin is presented to the user using the virtual BER. As a result, the user can qualitatively and accurately recognize the current state.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0005] In conventional receiving devices, including the technology described in Patent Document 1, the receiving margin is recognized and displayed when the receiving margin is positive, that is, when the reception state is better than the reception limit point (the C / N ratio is higher than the reception limit point). On the other hand, when the receiving margin is negative (the C / N ratio is lower than the reception limit point), although there are some communication problems, certain operations are often possible. For this reason, it is preferable that the user be able to recognize the negative receiving margin as well.

[0006] On the other hand, if the current receiving margin is recognized as negative, the user can take measures to improve the situation once they become aware of it. Therefore, there was a need for technology that could appropriately present this to the user even when the receiving margin is negative, and enable them to improve the situation. Furthermore, even when the receiving margin is positive, there was a need for technology that could similarly enable the user to take actions to improve the receiving state based on the current receiving margin.

[0007] This invention has been made in view of these circumstances and aims to solve the above-mentioned problems. [Means for solving the problem]

[0008] The receiving device of the present invention is a receiving device used in a transmission system that transmits a digital signal that has been subjected to error correction coding and modulated using predetermined transmission parameters, comprising: a digital demodulation unit that demodulates the digital signal from the received signal; a signal quality level calculation unit that calculates the signal quality level of the received signal; and a receiving margin which is the difference between the signal quality level of the received signal and the receiving limit point, which is the lower limit of the signal quality level that is permissible when the transmission parameters are used. , from negative values ​​where transmission is impossible due to the low signal quality level, to positive values,The system comprises: a receiver margin calculation unit; a transmission parameter calculation unit that calculates a provisional receiver margin, which is the difference between the signal quality level of the received signal and the receiver limit point when a provisional transmission parameter, which is a transmission parameter different from the current transmission parameter, is used, and that proposes a provisional transmission parameter such that the provisional receiver margin is larger than the receiver margin; and a display unit that displays the receiver margin, or the provisional receiver margin and the corresponding provisional transmission parameter. 。 Furthermore, the receiving device may include a storage unit that stores the reception limit points corresponding to multiple types of transmission parameters. Furthermore, the signal quality level calculation unit may calculate the modulation error ratio (MER) from the received signal and calculate the carrier / noise ratio (C / N ratio) as the signal quality level from the modulation error ratio. Furthermore, the transmission parameter calculation unit may calculate the provisional transmission parameters such that the value of the provisional reception margin falls within the required range. The wireless transmission system of the present invention comprises a receiving device and a transmitting device that transmits the received signal to the receiving device side by wireless communication, and is a wireless transmission system that enables bidirectional communication between the transmitting device and the receiving device, wherein the receiving device transmits the receiving margin, or the provisional receiving margin and the corresponding provisional transmission parameters to the transmitting device side. [Effects of the Invention]

[0009] According to the present invention, the user can perform operations to improve the reception status based on the current reception margin. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the configuration of a receiving device according to an embodiment of the present invention. [Figure 2] This figure shows the general dependence of BER on the C / N ratio. [Figure 3] This is an example of a method for displaying the recognized reception margin in a receiving device according to an embodiment of the present invention. [Figure 4] This figure shows the dependence of BER on the C / N ratio for multiple types of modulation schemes. [Figure 5] This is an example of a method for displaying the provisional reception margin in a receiving device according to an embodiment of the present invention.

[0011] Next, a receiving device that embodies the present invention will be specifically described. In this receiving device, a receiving status display method that embodies the present invention is implemented. This receiving device will be described below.

[0012] Figure 1 shows the configuration of the receiving device 1. This receiving device is part of a receiving system for, for example, an FPU (Field Pickup Unit: a wireless relay transmission device for television broadcasting), and operates in accordance with ARIB STD-B71. For encoding the digital signal transmitted here, LDPC code is used as the internal error correction code, and BCH code is used as the external error correction code. Figure 1 is a block diagram showing the configuration of the receiving device 1. Here, the configuration related to the decoded digital signal (TS signal for broadcasting) is irrelevant to the present invention and is therefore omitted from the description. In addition, signal processing before demodulation of the received signal includes, for example, the generation of a frequency-converted signal (IF signal) to an intermediate frequency, but here, the part that performs such pre-demodulation processing on the signal received from the antenna 10 is described as a single receiving high-frequency unit 20.

[0013] The digital demodulation unit 30 demodulates this IF signal according to the modulation scheme (OFDM, single-carrier QAM, etc.). However, the demodulated signal contains coding errors depending on the reception conditions. Therefore, this demodulated digital signal is input to the error correction decoding unit 40, where error correction processing is performed, thereby improving the coding error rate (BER) of this digital signal. Subsequently, the TS signal is output. The configuration for the TS signal from this point onward is the same as that of conventional receiving devices, such as the receiving device described in Patent Document 1, etc.

[0014] However, in this receiving device 1, the modulation method or transmission parameters of the received signal are not fixed, and various modulation methods and transmission parameters (hereinafter referred to as transmission parameters, etc.) are available. For this reason, the digital demodulation unit 30, etc. recognizes the currently used transmission parameters, etc., and performs the above demodulation based on them. The transmission parameters referred to here include "64QAM", "32QAM", "16QAM", "coding rate 1 / 2", etc., and include not only those that can be simply specified as numerical values, but also types of specifications that cannot be specified as simple numerical values.

[0015] Here, in order for the error correction processing by the error correction decoding unit 40 to be performed properly and for a proper TS signal to be output, the BER after the error correction processing by the error correction decoding unit 40 must be below a certain value (allowable upper limit). On the other hand, this BER depends on the reception state (C / N ratio (carrier / noise ratio: unit dB) of the received signal), and when the C / N ratio is small, the BER will be large, and when the C / N ratio is large, the BER will be small.

[0016] Therefore, a signal quality level calculation unit 50 is used here to recognize the signal quality level of the current received signal from the demodulation status of the digital demodulation unit 30. The signal quality level recognized here is the C / N ratio. The signal quality level calculation unit 50 can recognize the MER (modulation error ratio: in dB) in the constellation according to the modulation scheme such as OFDM or single-carrier QAM performed by the digital demodulation unit 30. Since there is a certain relationship between MER and the C / N ratio, the C / N ratio of the current received signal can be calculated from this relationship. This relationship can be stored in the storage unit 60, which will be described later.

[0017] Figure 2 shows the dependence of BER on the C / N ratio. For example, when conforming to ARIB STD-B11 and ARIB STD-B33, Viterbi decoding is used for error correction, and in this case the reception limit point is BER 1 × 10⁻⁶. -4This results in a point where, in FIG. 2, the C / N ratio in this case is Cn0. Therefore, the reception margin is positive when the C / N ratio > Cn0 and negative when the C / N ratio < Cn0. As will be described later, the characteristics of FIG. 2 vary depending on transmission parameters and the like. For this reason, in FIG. 1, the C / N ratio dependency of the BER illustrated in FIG. 2 is stored in the storage unit 60 composed of a hard disk or the like according to the transmission parameters and the like. In the storage unit 60, instead of storing the characteristics of FIG. 2 for each transmission parameter and the like, only Cn0 for each transmission parameter and the like may be stored.

[0018] The reception margin calculation unit 70 in FIG. 1 can recognize the current transmission parameters and the like from the digital demodulation unit 30. Based on this, the corresponding C / N ratio dependency or Cn0 of the BER can be recognized from the storage unit 60. On the other hand, the reception margin calculation unit 70 can recognize the current C / N ratio from the signal quality level calculation unit 50, recognize the difference between this C / N ratio and the above Cn0 as the reception margin, display this result on the display unit 80 having a display, and allow the user to recognize it. This reception margin is the difference between the current C / N ratio and Cn0, and is displayed on the display unit 80 regardless of the positive or negative of the reception margin.

[0019] FIG. 3 is an example of the display on the display unit 80 showing such a current reception margin. Here, the reception margin is displayed as a bar graph in dB units, and the first range (+11 to +15 dB, a range of a very good reception state), the second range (+1 to +10 dB, a range of a good reception state), and the third range (-15 to 0 dB, a range of a non-good reception state) are each displayed in different colors (hatches in the figure), and the bar corresponding to the recognized reception margin (here, -3 dB) is set to blink. As a result, the user can easily recognize the current reception margin. In particular, it is possible to easily recognize which of the above ranges the current reception state is in.

[0020] Furthermore, in FIG. 1, a transmission parameter calculation unit 90 is also provided for calculating transmission parameters and the like that reduce the BER more in the current reception state. As described above, since the storage unit 60 stores the characteristics of FIG. 2 or Cn0 in each transmission parameter and the like, it is possible to calculate the reception margin when the transmission parameter and the like are different from the current ones.

[0021] FIG. 4 shows the C / N ratio dependence of BER when the modulation schemes are BPSK, QPSK, 8PSK, 16QAM, 32QAM, and 64QAM (all with a coding rate of 1 / 2). As shown here, among these, the BER in the case of BPSK is the smallest (the characteristic is at the bottom), and the BER in the case of 64QAM is the largest (the characteristic is at the top). Alternatively, when the BER corresponding to the reception limit point is a constant value (for example, 1×10 -4 ), the corresponding Cn0 is the smallest in the case of BPSK and the largest in the case of 64QAM. As described above, these characteristics, or the Cn0 in each characteristic when the BER of the reception limit point is fixed, can be stored in the storage unit 60.

[0022] In this case, for example, when the current modulation scheme is 64QAM, if the C / N ratio < Cn0, it is possible to change the modulation scheme to 32QAM or 16QAM so that the C / N ratio > Cn0. The transmission parameter calculation unit 90 can display such a situation on the display unit 80. That is, the transmission parameter calculation unit 90 calculates the reception margin (temporary reception margin) when the transmission parameter (temporary transmission parameter) is other than the current transmission parameter at the current C / N ratio (signal quality level), and displays it on the display unit 80. Here, in particular, the result (temporary transmission parameter and the corresponding temporary reception margin) when the temporary reception margin is larger than the current reception margin is calculated and displayed.

[0023] Figure 5 shows an example of the display in this case, using the same display method as in Figure 3. Here, it is shown that if the current modulation scheme is 64QAM and the reception margin is -3dB, changing the modulation scheme to 32QAM or 16QAM will improve the reception margin to 0dB and +3dB, respectively. By looking at this display, the user can recognize that it is preferable to change the modulation scheme (transmission parameters) to 32QAM or 16QAM. For example, the user can decide to set the modulation scheme to 32QAM if the current reception situation is at its worst and it is clear that it will improve in the future, or to set the modulation scheme to 16QAM if the prospects for future reception conditions are unknown. However, the user may be allowed to set the required (provisional) reception margin value (range), and the transmission parameter calculation unit 90 may calculate and display the (provisional) transmission parameters that will obtain such a (provisional) reception margin.

[0024] Such changes to the modulation scheme (transmission parameters) must be made simultaneously on both the receiving and transmitting sides, and the user can have this change made after the above decision. If the communication method in the wireless transmission system in which this receiving device is used is such that communication only occurs from the transmitting device to this receiving device, then it is effective to give such instructions to the user on the receiving side.

[0025] On the other hand, if the communication method in the wireless transmission system using this receiving device is bidirectional, then the results of the receiving margin calculation unit 70 and the transmission parameter calculation unit 90 can be transmitted from the receiving device to the transmitting device, these results can be shared between the receiving and transmitting devices, and the transmitting device can display these results. In this case, the transmitting and receiving devices can simultaneously make changes to preferred transmission parameters, or these changes can be made automatically.

[0026] In the example above, the signal quality level was set as the C / N ratio, but similarly, any other quantity can be used as the signal quality level as long as it is a quantity that allows the reception limit point to be recognized as the lower limit for each transmission parameter. Similarly, transmission parameters can be set as long as they are quantities (or types) that allow the reception limit point to be recognized for each transmission parameter, as described above.

[0027] The present invention has been described above based on embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in the combination of these components, and that such modifications also fall within the scope of the present invention. [Explanation of symbols]

[0028] 1. Receiving device 10 Antennas 20 Receiving high-frequency section 30 Digital demodulation section 40 Error Correction and Decoding Unit 50 Signal Quality Level Calculation Unit 60 Storage section 70 Receiving margin calculation unit 80 Display section 90 Transmission parameter calculation unit

Claims

1. A receiving device used in a transmission system that transmits a digital signal that has been subjected to error correction coding and modulated using predetermined transmission parameters, A digital demodulation unit that demodulates the digital signal from the received signal, A signal quality level calculation unit that calculates the signal quality level of the received signal, A receiver margin calculation unit calculates a receiver margin, which is the difference between the signal quality level of the received signal and the receiver limit point, which is the lower limit of the signal quality level that is permissible when the transmission parameters are used, over a range from a negative value where transmission is impossible due to a low signal quality level to a positive value. A transmission parameter calculation unit calculates a provisional reception margin, which is the difference between the signal quality level of the received signal and the reception limit point when a provisional transmission parameter, which is a transmission parameter different from the current transmission parameter, is used, and proposes a provisional transmission parameter such that the provisional reception margin is larger than the reception margin. A display unit that displays the reception margin, or the provisional reception margin and the corresponding provisional transmission parameters, A receiving device characterized by comprising the following:

2. The receiving device is, The receiving device according to claim 1, further comprising a storage unit that stores the reception limit points corresponding to multiple types of transmission parameters.

3. The receiving device according to claim 1 or 2, characterized in that the signal quality level calculation unit calculates the modulation error ratio (MER) from the received signal and calculates the carrier / noise ratio (C / N ratio) as the signal quality level from the modulation error ratio.

4. The transmission parameter calculation unit, The receiving device according to claim 1 or 2, characterized in that it calculates the provisional transmission parameters such that the value of the provisional reception margin falls within a requested range.

5. A wireless transmission system comprising a receiving device according to claim 1 or 2, and a transmitting device that transmits the received signal to the receiving device side by wireless communication, wherein bidirectional communication is possible between the transmitting device and the receiving device, A wireless transmission system characterized in that the receiving device transmits the receiving margin, or the provisional receiving margin and the corresponding provisional transmission parameters to the transmitting device.

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