A processing device that transmits analog signals to a wireless device

Abstract

To provide a technique for transmitting control information to a wireless device with a simple configuration.SOLUTION: A processing device transmits an analog signal to a wireless device that generates a wireless signal on the basis of the analog signal and transmits it. The processing device includes control means for generating a pulse signal that conveys control information to the wireless device and a low-pass filter that restricts the maximum frequency of the pulse signal, multiplexing means for multiplexing the pulse signal that has passed through the low-pass filter and the analog signal and outputting a multiplexed signal, and modulation means for generating modulated light by modulating carrier light with the multiplexing signal and transmitting the modulated light to the wireless device.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a technique for transmitting, via an optical fiber, an analog signal for generating a wireless signal to a wireless device that transmits and receives the wireless signal.

Background Art

[0002] FIG. 1 shows a configuration in which the functions of a base station device of a mobile communication network are divided into a processing device 1 and a wireless device 2, the wireless device 2 is disposed at an antenna site 200 where an antenna is installed, and the processing device 1 is disposed at a housing site 100 that is geographically different from the antenna site. The wireless device 2 has a function of transmitting and receiving a wireless signal to and from a wireless device (WD) or a user equipment (UE) of a mobile communication network via the antenna, and a function of processing the wireless signal. On the other hand, the processing device 1 has a function of processing a baseband signal of the wireless signal transmitted and received by the wireless device 2. The processing device 1 and the wireless device 2 are connected by an optical transmission line 3 including an optical fiber.

[0003] Non-Patent Document 1 discloses CPRI, which is a communication interface between the processing device 1 and the wireless device 2. Specifically, the processing device 1 samples the signal waveform of the baseband signal and transmits the sampling value as a digital value to the wireless device 2. In CPRI, control information transmitted from the processing device 1 to the wireless device 2 is time-division multiplexed with a digital value indicating the sampling value. Currently, transmission via CPRI has become inefficient due to an increase in the transmission capacity to the WD.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to cope with the increase in the transmission capacity to the WD, in the processing device 1, an IF signal in the intermediate frequency (IF) band or an RF signal in the radio frequency (RF) band is generated from the baseband signal, and the modulation light generated by modulating the carrier light with the IF signal or the RF signal is transmitted to the wireless device 2. A configuration can be considered. The wireless device 2 demodulates the modulated light to restore and generate the IF signal or RF signal transmitted by the processing device 1, converts these signals into wireless signals of a predetermined frequency in the radio frequency band, and then performs necessary processing such as amplification and outputs them from the antenna. When the frequency of the RF signal matches the predetermined frequency, the frequency conversion can be omitted.

[0006] FIG. 2 shows the frequency components of exemplary modulated light generated by the processing device 1 in such a configuration. According to FIG. 2, the modulated light carries four frequency-division multiplexed IF signals 81 to 84. Here, if another optical transmission line 3 is used to transmit and receive control information between the processing device 1 and the wireless device 2, the configuration becomes complicated and the cost increases.

[0007] The present invention provides a technique for transmitting control information to a wireless device with a simple configuration.

Means for Solving the Problems

[0008] According to one aspect of the present invention, in a wireless device that generates and transmits a wireless signal based on an analog signal, the processing device that transmits the analog signal includes a control means for generating a pulse signal that carries control information to the wireless device, and a low-pass filter that limits the maximum frequency of the pulse signal, and a multiplexing means for multiplexing the pulse signal that has passed through the low-pass filter and the analog signal to output a multiplexed signal, and a modulation means for generating modulated light by modulating the carrier light with the multiplexed signal and transmitting the modulated light to the wireless device. selection means for receiving the multiplexed signal and the pulse signal and outputting either the multiplexed signal or the pulse signal to the modulation means; comprising wherein, when the maximum frequency required for transmission of the pulse signal is within the passband of the low-pass filter, the control means controls the selection means so that the multiplexed signal is output to the modulation means, and when the maximum frequency required for transmission of the pulse signal is outside the passband of the low-pass filter, the control means controls the selection means so that the pulse signal is output to the modulation means 。

Effects of the Invention

[0009] According to the present invention, control information can be transmitted to a wireless device with a simple configuration.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of the features described in the embodiments are essential to the invention. Two or more of the plurality of features described in the embodiments may be arbitrarily combined. Also, the same or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0012] <First Embodiment> FIG. 3 is a configuration diagram of a base station system including a processing device 1 and a wireless device 2 according to the present embodiment. The control unit 10 controls the processing device 1 and generates a control signal to be transmitted to the wireless device 2. The control signal is a signal that carries control information. In the present embodiment, the control signal is a digital signal, that is, a pulse signal. For example, the control signal may be a signal conforming to a standard used in a local area network (LAN). The pulse signal may be a Non-Return-to-Zero (NRZ) signal or a Return-to-Zero (RZ) signal. Note that at the same transmission speed, the NRZ signal has a narrower bandwidth than the RZ signal, so the NRZ signal is preferred. The control unit 10 outputs the control signal to the low-pass filter (LPF) 11 of the multiplexing unit 13. The LPF 11 has a passband below a threshold frequency f1 and restricts the frequency band of the control signal. An intermediate frequency (IF) signal or a radio frequency (RF) signal that carries information to be transmitted to the WD, or a frequency-division multiplexed signal obtained by frequency-division multiplexing them, is input to the high-pass filter (HPF) 12 of the multiplexing unit 13. The IF signal or the RF signal, or the frequency-division multiplexed signal obtained by frequency-division multiplexing them, is an analog signal. In the following description, the IF signal or the RF signal, or the frequency-division multiplexed signal thereof input to the HPF 12 is collectively referred to as an "analog signal". Note that the lowest frequency of the analog signal is set to be higher than the threshold frequency f1. The HPF 12 suppresses unnecessary frequency components below the threshold frequency f1.

[0013] The multiplexing unit 13 outputs a multiplexed signal obtained by multiplexing the filtered control signal and the analog signal to the modulation unit 14. The modulation unit 14 generates modulated light by modulating the carrier light with the multiplexed signal and transmits the modulated light to the wireless device 2. FIG. 4 shows the frequency components of the modulated light. The entire reference numerals 81 to 84 in FIG. 4 are analog signals, and the reference numerals 81 to 84 correspond to four IF signals, respectively. The reference numeral 80 in FIG. 4 corresponds to the control signal.

[0014] The demodulation unit 24 demodulates the modulated light received from the processing device 1 and outputs a multiplexed signal to the separation unit 23. The separation unit 23 separates the multiplexed signal and then outputs a control signal via the LPF 21 and outputs an analog signal via the HPF 22. The passbands of the LPF 21 and the HPF 22 are the same as those of the LPF 11 and the HPF 12, respectively. The control unit 20 receives the control signal from the LPF 21 and controls the wireless device 2 based on the control signal. The analog signal output by the HPF 22 is converted into a wireless signal by a circuit (not shown) and transmitted toward the WD.

[0015] As described above, in the present embodiment, a control signal, which is a pulse signal for controlling the wireless device 20, and an analog signal for carrying information to be transmitted to the WD are multiplexed, and the multiplexed signal is used to modulate the carrier light and transmitted to the wireless device 20. With this configuration, the control signal and the analog signal can be transmitted through the same optical fiber. Further, since the control information is transmitted as a baseband signal (for example, an NRZ pulse signal) without modulating (for example, ASK, PSK, QAM, etc.) the electrical signal of the sine wave carrier based on the control information, the configuration for transmitting the control information can be simplified. Note that the configuration in the direction from the wireless device 2 to the processing device 1 is the same, and the control signal from the control unit 20 to the control unit 10 can be used, for example, as a response to the control signal received by the control unit 20 from the control unit 10.

[0016] <Second Embodiment> Subsequently, the differences between the second embodiment and the first embodiment will be mainly described. For example, when the amount of control information to be transmitted to the wireless device 2 increases, such as when the wireless device 2 is installed, the time required to transmit the control signal to the wireless device 2 becomes longer in the bandwidth less than the threshold frequency f1. Therefore, in the present embodiment, the threshold frequency is made variable according to the amount of control information to be transmitted, that is, the transmission speed required for the control signal.

[0017] FIG. 5 is a configuration diagram of the processing device 1 and the wireless device 2 according to the present embodiment. Note that the same reference numerals are given to the components similar to those in FIG. 3 of the first embodiment, and the following description will focus on the differences. The control unit 10 also outputs a control signal to the LPF 15 of the multiplexing unit 17. The LPF 15 has a passband less than the threshold frequency f2 and suppresses unnecessary high-frequency components. Note that the threshold frequency f2 is greater than the threshold frequency f1. The analog signal is also input to the HPF 16 of the multiplexing unit 17. The HPF 16 suppresses unnecessary frequency components less than the threshold frequency f2. The multiplexing unit 17 multiplexes the filtered control signal and the analog signal to generate a multiplexed signal.

[0018] The selection unit 18 receives the multiplexed signal from the multiplexing unit 13 and the multiplexed signal from the multiplexing unit 17. While transmitting the first control signal capable of limiting the maximum frequency to less than the threshold frequency f1, the control unit 10 controls the selection unit 18 to output the multiplexed signal from the multiplexing unit 13 to the modulation unit 14. On the other hand, while transmitting the second control signal capable of limiting the maximum frequency to be greater than the threshold frequency f1 but less than the threshold frequency f2, the control unit 10 controls the selection unit 18 to output the multiplexed signal from the multiplexing unit 17 to the modulation unit 14. For example, the first control signal can be 100 MbE and the second control signal can be 1 GbE.

[0019] Further, before switching from the first control signal to the second control signal at a predetermined timing, the control unit 10 notifies the wireless device 2 of a first switching timing for switching from the first control signal to the second control signal by the first control signal. Similarly, before switching from the second control signal to the first control signal at a predetermined timing, the control unit 10 notifies the wireless device 2 of a second switching timing for switching from the second control signal to the first control signal by the second control signal. When the first switching timing arrives, the control unit 20 of the wireless device 2 controls the selection unit 28 to output the multiplexed signal output from the demodulation unit 24 to the separation unit 27. Also, when the second switching timing arrives, the control unit 20 controls the selection unit 28 to output the multiplexed signal output from the demodulation unit 24 to the separation unit 23. The separation unit 27 outputs the second control signal to the control unit 20 via the LPF 25 and outputs an analog signal via the HPF 26. The pass bands of the LPF 25 and the HPF 26 are the same as those of the LPF 15 and the HPF 16, respectively.

[0020] Note that while the second control signal is being used, the available bandwidth for the analog signal becomes smaller. For this reason, the control unit 10 limits the amount of information transmitted to the WD and reduces the bandwidth of the analog signal during the period when the second control signal is being used. Also, in this embodiment, two multiplexing units including an LPF and an HPF are used, but three or more may be used. Note that the pass bands of the LPF and the HPF of each of the three or more multiplexing units are different, and the control unit 10 selects a multiplexing unit to which the multiplexed signal is output to the modulation unit 14 according to the speed of the control signal to be transmitted. Note that the multiplexing unit to be selected is selected from the multiplexing units having an LPF whose pass band includes the maximum frequency required for transmitting the control signal. For example, the multiplexing unit to be selected can be a multiplexing unit having the lowest pass band among the multiplexing units having an LPF whose pass band includes the maximum frequency required for transmitting the control signal.

[0021] As described above, according to this embodiment, when the amount of information to be transmitted increases, the speed of the control signal can be increased.

[0022] <Third Embodiment> Next, regarding the third embodiment, the differences from the second embodiment will be mainly described. In the second embodiment, two or more multiplexing units including an LPF and an HPF were used so that the speed of the control signal could be increased. In this embodiment, the number of multiplexing units to be used is one.

[0023] FIG. 6 is a configuration diagram of the processing device 1 and the wireless device 2 according to this embodiment. The control unit 10 also outputs a control signal to the selection unit 18. While transmitting a first control signal whose maximum frequency can be limited to less than the threshold frequency f1, the control unit 10 controls the selection unit 18 to output the multiplexed signal from the multiplexing unit 13 to the modulation unit 14. On the other hand, while transmitting a third control signal whose maximum frequency cannot be limited to less than the threshold frequency f1, the control unit 10 controls the selection unit 18 to output the control signal from the control unit 10 to the modulation unit 14.

[0024] Also, the control unit 10 notifies the control unit 20 of the switching timing between the first control signal and the third control signal in the same manner as in the second embodiment. Therefore, the first control signal is input to the control unit 20 from the selection unit 28 via the separation unit 23, and the third control signal is input to the control unit 20 directly from the selection unit 28.

[0025] Note that, unlike the second embodiment, while using the third control signal, the control unit 10 temporarily stops the transmission to the WD and does not transmit the analog signal. In many cases, the increase in the information amount of the control signal is during the period of establishing a link between the processing device and the wireless device before starting the transmission and reception of the wireless signal (including during reboot, etc.). By making the above-described functions work only during that period, it is possible to obtain a desired effect with a simpler configuration than the second embodiment.

[0026] <Fourth Embodiment> In this embodiment, by using a control signal, the quality of the optical transmission path 3 from the processing device 1 to the wireless device 2 is measured, and the quality of the analog signal carried on the optical transmission path 3 is determined. Specifically, the control unit 10 transmits data of a known pattern to the control unit 20 by means of a control signal, and the control unit 20 determines whether an error has occurred based on this data of the known pattern. By measuring the known pattern while changing the level of the carrier light, the signal-to-noise ratio (SN ratio) of the optical transmission path 3 from the processing device 1 to the wireless device 2 can be determined.

[0027] With the above configuration, a control signal can be transmitted to the wireless device with a simple configuration. Therefore, it becomes possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

Description of Reference Numerals

[0028] 13: Multiplexer, 14: Modulator

Claims

1. A processing device that transmits an analog signal to a wireless device that generates and transmits a wireless signal based on the analog signal, control means for generating a pulse signal carrying control information for said wireless device; a combining means including a low-pass filter for limiting a maximum frequency of the pulse signal, the combining means combining the pulse signal that has passed through the low-pass filter with the analog signal and outputting a combined signal; a modulation means for modulating a carrier light with the multiplexed signal to generate modulated light and transmitting the modulated light to the wireless device; a selection means for receiving the combined signal and the pulse signal and outputting either the combined signal or the pulse signal to the modulation means; Equipped with The control means controls the selection means so that the combined signal is output to the modulation means when the maximum frequency required to transmit the pulse signal is within the passband of the low-pass filter, and controls the selection means so that the pulse signal is output to the modulation means when the maximum frequency required to transmit the pulse signal is outside the passband of the low-pass filter.

2. A processing device that transmits an analog signal to a wireless device that generates and transmits a wireless signal based on the analog signal, control means for generating a pulse signal carrying control information for said wireless device; a plurality of multiplexing means each including a low-pass filter for limiting a maximum frequency of the pulse signal, the multiplexing means multiplexing the pulse signal that has passed through the low-pass filter with the analog signal and outputting a multiplexed signal; a modulation means for generating modulated light by modulating a carrier light with one of the multiplexed signals output by the multiplexing means, and transmitting the modulated light to the wireless device; a selection means for outputting the one of the plurality of combined signals to the modulation means; Equipped with the passbands of the low-pass filters of the multiplexing means are different from each other; The control means selects the one combined signal to be output by the selection means to the modulation means in accordance with a maximum frequency required for transmission of the pulse signal.

3. 3. The processing device according to claim 2, wherein the control means selects the one combined signal by selecting one of the first combining means from among the plurality of combining means, the first combining means being equipped with the low-pass filter that sets the maximum frequency required for transmitting the pulse signal within a passband.

4. 4. The processing device according to claim 3, wherein the one multiplexing means is a first multiplexing means having the low-pass filter with the lowest pass band among the one or more first multiplexing means.

5. 5. The processing device according to claim 1, wherein the control means controls the bandwidth of the analog signal depending on a maximum frequency required for transmission of the pulse signal.

6. 6. The processing device according to claim 1, wherein said control means transmits predetermined data by said pulse signal in order to measure a transmission quality in an optical transmission path from said processing device to said wireless device.

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