JP7145709B2 - Radio equipment for mobile communication networks - Google Patents

Description

The present invention relates to a radio equipment of a base station equipment using a radio over fiber (RoF) system.

For example, fifth generation mobile communication networks use high frequencies such as millimeter waves for broadband (high speed) communication. Since the propagation distance of such high-frequency radio signals is short, base station apparatuses using high frequencies must be arranged at a high density. For this reason, as shown in FIG. 1, a base station apparatus is composed of a radio apparatus (child apparatus) that transmits and receives radio signals, baseband signal processing, and frequency conversion processing between baseband signals and radio frequency signals. A configuration in which the processing is divided into a processing device (parent device) that performs the processing is being studied. Processing devices that perform a large amount of processing can be centrally arranged at a certain location, and a large number of wireless devices can be arranged at a high density, thereby increasing the area in which high frequencies can be efficiently used. In the configuration shown in FIG. 1, a so-called radio-over-fiber (RoF) method is applied for communication between the processing device and the wireless device. Specifically, the processing device converts the baseband signal into a radio frequency signal, modulates continuous light with the radio frequency signal, and transmits an optically modulated signal to the radio device. The radio device photoelectrically converts the optically modulated signal received from the processing device to extract a radio frequency signal, performs necessary processing such as amplification and filtering, and then transmits the radio signal as a downstream radio signal from an antenna.

On the other hand, the wireless device modulates continuous light based on the wireless signal received from the user device and transmits the modulated continuous light to the processing device. Here, if the radio signal received from the user equipment has a high frequency, eg, 60 GHz, the radio equipment needs to modulate continuous light with an electrical signal of 60 GHz. Such a configuration for modulating continuous light with a high-frequency electrical signal is very complicated, and if such a configuration is applied to wireless devices that need to be arranged at a high density, the cost of the communication network increases. put away. Therefore, in the upstream direction, a radio signal received from the user equipment is down-converted to a lower frequency, for example, 1 GHz, and the down-converted signal (hereinafter referred to as an IF signal) is used to modulate continuous light. can be considered. However, if each radio device is provided with a local oscillator that generates a signal for frequency conversion, the cost of the radio device increases.

Here, Patent Literature 1 discloses a configuration in which a control station (parent station) generates a frequency conversion signal used for frequency conversion in an antenna station (child station) and transmits the generated signal to the antenna station. Further, Patent Literature 2 discloses a configuration in which a master station generates a reference signal to be used by the slave station's PLL and transmits it to the slave station.

JP-A-2001-53688 JP 2009-94572 A

The configurations of Patent Documents 1 and 2 transmit frequency-converted signals and reference signals used by slave stations separately from communication signals. Therefore, when the configurations of Patent Documents 1 and 2 are applied to a base station apparatus composed of a processing device and a radio device, separate communication devices for transmitting frequency-converted signals and reference signals between the processing device and the radio device are used. Equipment is required, which increases costs.

The present invention provides techniques for performing frequency conversion in wireless devices without increasing costs.

According to one aspect of the present invention, during downstream communication, an optical signal including a first continuous light having a first frequency and a modulated light obtained by modulating a second continuous light having a second frequency different from the first frequency. and receiving an optical signal containing the first continuous light and the second continuous light during uplink communication includes photoelectric conversion means for photoelectrically converting the received optical signal; During downlink communication, a first modulated signal obtained by the beat of the modulated light and the first continuous light output from the photoelectric conversion means is converted into a first radio signal and transmitted to the user device, and the uplink communication is performed. communication means for converting a second radio signal received from the user equipment into a second modulated signal and outputting the second modulated signal during uplink communication; and the second modulated signal output by the communication means during uplink communication, By the frequency conversion means for frequency-converting the signal obtained by the beat of the first continuous light and the second continuous light output from the photoelectric conversion means, and the second modulated signal after the frequency conversion by the frequency conversion means and modulating means for modulating the third continuous light.

Advantageous Effects of Invention According to the present invention, frequency conversion can be performed in wireless devices without increasing costs.

The block diagram of the base station apparatus by one Embodiment. 1 is a configuration diagram of a wireless device according to an embodiment; FIG. FIG. 3 is a diagram showing an optical signal received by a wireless device and a signal after photoelectric conversion according to an embodiment; 1 is a configuration diagram of a wireless device according to an embodiment; FIG. FIG. 3 is a diagram showing an optical signal received by a wireless device and a signal after photoelectric conversion according to an embodiment; 1 is a configuration diagram of a wireless device according to an embodiment; FIG. 1 is a configuration diagram of a wireless device according to an embodiment; FIG.

Exemplary embodiments of the invention will now be described with reference to the drawings. In addition, the following embodiments are examples, and the present invention is not limited to the contents of the embodiments. Also, the present invention is applied to a base station apparatus that communicates with a user apparatus by time division duplex (TDD) and is composed of the processing apparatus and radio apparatus described above. Note that, in each drawing below, constituent elements that are not necessary for the description of the embodiment are omitted from the drawing. Specifically, for example, filters, amplifiers, and the like that are not necessary for the description of the embodiments are omitted from the drawings.

<First embodiment>
In the present embodiment, during downstream communication, the processing device, as shown in FIG. and continuous light of frequency f2 to the wireless device. In this example, the processing device removes the lower sideband component (frequency f1-α) and transmits modulated light containing the carrier wave component (frequency f1) and the upper sideband component (frequency f1+α). do. On the other hand, during upstream communication, the processor transmits continuous light of frequency f1 and continuous light of frequency f2 to the wireless device, as shown in FIG. 3B. As a specific numerical example, it is assumed that the frequency f3=f2-f1 is 60 GHz and α is 1 GHz.

FIG. 2 is a configuration diagram of a wireless device according to this embodiment. In FIG. 2, the frequencies above and on the right side of the arrow indicate the frequencies of the signals during downlink communication, and the frequencies below and on the left side of the arrow indicate the frequencies of the signals during uplink communication. . The same applies to other drawings.

First, the downlink communication will be described. The photoelectric conversion unit 11 photoelectrically converts an optical signal received from the processing device and outputs an electrical signal to a bandpass filter (BPW) 12 . BPW 12 has a passband near frequency f3. The photoelectric conversion unit 11 outputs an electric signal (beat signal) centering on the frequency difference for each combination of two of the three optical signals shown in FIG. 3(A). Specifically, the photoelectric converter 11 outputs an electrical signal (sine wave signal) with a frequency f3=f2-f1 as a beat signal of a carrier wave component (frequency f1) and continuous light (frequency f2). Further, the photoelectric converter 11 outputs an electric signal (modulation signal) of frequency f3-α as a beat signal of the upper waveband component (frequency f1+α) and continuous light (frequency f2). In this example, the frequency f3 is 60 GHz and the frequency f3-α is 59 GHz. Although the photoelectric converter 11 also outputs a beat signal including a carrier wave component (frequency f1) and an upper waveband component (frequency f1+α), the BPW 12 blocks these unnecessary signal components. FIG. 3C shows a signal input from the BPW 12 to the switching unit 13 during downlink communication.

During downlink communication, the switching unit 13 outputs the input signal only to the BPW 14 . BPW 14 blocks the sine wave signal of frequency f3 and outputs the modulated signal of frequency f3−α to switching section 15 . During downlink communication, the switching unit 15 outputs the modulated signal of frequency f3-α only to the antenna 19 . Therefore, the antenna 19 transmits a radio signal of frequency f3-α (59 GHz in this example).

Next, the uplink communication will be described. A radio signal of frequency f3-α transmitted by the user equipment is converted into a modulated signal of frequency f3-α by antenna 19 and output to switching section 15 . During upstream communication, the switching unit 15 outputs the modulated signal of frequency f3-α only to the frequency conversion unit 16 . On the other hand, during upstream communication, the photoelectric conversion unit 11 outputs only an electrical signal (sine wave signal) of frequency f3 as shown in FIG. 3(D). This sine wave signal of frequency f3 is input to the switching section 13 via the BPW 12 . During upstream communication, the switching unit 13 outputs the input signal only to the frequency conversion unit 16 . The frequency conversion unit 16 down-converts the modulated signal of frequency f3-α input from the switching unit 15 with the sine wave signal of frequency f3 input from the switching unit 13, and outputs the modulated signal of frequency α. The BPW 17 is a filter that passes a band including the frequency α, and the optical modulator 18 modulates continuous light with a modulation signal of the frequency α and transmits the modulated signal to the processing device.

As described above, the processing device uses a so-called two-tone method for downstream communication. That is, modulated light obtained by modulating continuous light (frequency f1) with a radio frequency signal of frequency α and continuous light of frequency f2 are transmitted to a wireless device, and the wireless device responds to the frequency difference between the modulated light and the continuous light. A radio frequency signal (59 GHz in this example) is generated and this radio frequency signal is transmitted as a radio signal. On the other hand, normally, during upstream communication, the processing device does not transmit a signal to the wireless device. is photoelectrically converted to generate a sine wave signal of frequency f3=f2-f1 (60 GHz in this example), thereby down-converting the modulated signal of radio frequency (59 GHz in this example) received from the user equipment. With this configuration, the wireless device receives signals from the user equipment without providing a local oscillator in the wireless device or providing additional equipment for transmitting signals for down-conversion between the processing device and the wireless device. It is possible to perform frequency conversion of the modulated signal of the radio frequency band to be used.

<Deformed form>
In this embodiment, the processing device intensity-modulates the continuous light of frequency f1, and transmits the modulated light containing the carrier wave component of frequency f1 and the upper sideband component of frequency f1+α to the wireless device. However, the processor can also phase-modulate or QAM-modulate the continuous light of frequency f1. FIG. 5 shows each signal in this case. As shown in FIG. 5A, the modulated light is centered on frequency f1 and has a bandwidth corresponding to the symbol rate. Further, as shown in FIG. 5C, the photoelectric conversion unit 11 outputs a modulated signal with frequency f3. FIG. 5B showing the signal output by the processing device during upstream communication, and FIG. 5D showing the electrical signal output by the photoelectric conversion unit 11 are shown in FIGS. ) is the same as FIG. 4 shows signal frequencies for each functional block of the wireless device. In this case, the frequency converter 16 outputs a baseband signal, and the optical modulator 18 modulates continuous light with the baseband signal. Also, the BPW 14 can be omitted.

In addition, in this embodiment, a circulator can be used instead of the switching unit 15 .

<Second embodiment>
Next, the second embodiment will be described, focusing on differences from the first embodiment. In this embodiment, as shown in FIG. 6, a splitter 20 is used in place of the switching section 13 of the first embodiment. A first output port of the splitter 20 is connected to the BPW 14, a second output port of the splitter 20 is connected to the frequency conversion section 16, and the splitter 20 always converts the input electrical signal to output to Specifically, during downstream communication, a sine wave signal of frequency f3 and a modulated signal of frequency f3−α are output to BPW 14 and frequency converter 16 . The processing from the BPW 14 to the antenna 19 during downlink communication is the same as in the first embodiment. On the other hand, in this embodiment, the sine wave signal of frequency f3 and the modulated signal of frequency f3-α are output to the frequency converter 16 during downlink communication. Since no signal is input from the switching unit 15 to the frequency conversion unit 16 during downlink communication, the frequency conversion unit 16 outputs the sine wave signal of the frequency f3 and the modulated signal of the frequency f3-α to the BPW 17 as they are. However, since the sinusoidal signal of frequency f3 and the modulated signal of frequency f3-α are signals in the stopband of BPW 17, no signals are transmitted from the wireless device to the processing device.

On the other hand, during upstream communication, splitter 20 outputs a sine wave signal of frequency f3 to BPW 14, but this signal is blocked by BPW 14. FIG. Further, during upstream communication, splitter 20 outputs a sine wave signal of frequency f3 to frequency conversion section 16, and switching section 15 outputs a modulated signal of frequency f3-α to frequency conversion section 16. FIG. The processing from the frequency converter 16 to the optical modulator 18 during downlink communication is the same as in the first embodiment. It should be noted that in this embodiment as well, the processor can use phase modulation or QAM modulation. In this case, during upstream communication, the sine wave signal of frequency f3 output from the splitter 20 to the switching section 15 is blocked by the switching section 15 and is not transmitted as a radio signal.

<Third embodiment>
Next, the third embodiment will be described, focusing on differences from the first embodiment. In this embodiment, the processing device transmits modulated light obtained by modulating continuous light of frequency f1 by an arbitrary modulation method and continuous light of frequency f2 to the wireless device during downstream communication. On the other hand, the processor transmits continuous light of frequency f1' and continuous light of frequency f2' to the wireless device during upstream communication. Note that the frequency difference between the frequencies f2 and f1 is f3, and the frequency difference between the frequencies f2' and f1' is f3'. Also, α is the difference between the frequency f3 and the frequency f3'. For example, if frequency f3 is 60 GHz and frequency f3' is 59 GHz, α is 1 GHz. FIG. 7 is a configuration diagram of a wireless device according to this embodiment. The frequencies shown in FIG. 7 indicate the case where the processing device QAM-modulates the continuous light of frequency f1 during upstream communication.

In this embodiment, a filter 30 is used instead of the switching unit 13 of the first embodiment. Filter 30 outputs a signal of frequency f3 to switching section 15 and a signal of frequency f3′ to frequency conversion section 16 . Therefore, during downlink communication, a modulated signal of frequency f3 (60 GHz in this example) is transmitted to the user equipment as a radio signal. On the other hand, during upstream communication, a modulated signal of frequency f3 received from the user equipment is converted into a modulated signal of frequency α by a sine wave signal of frequency f3′ from filter 30 .

Also in this embodiment, the switching unit 15 can be replaced with a circulator. Also, the switching unit 13 can be used in place of the filter 30, as in the first embodiment. Furthermore, the splitter 20 can be used in place of the filter 30 as in the second embodiment. Also, one of frequency f1' and frequency f2' transmitted by the processing device may be the same as frequency f1 or frequency f2.

11: photoelectric converter, 19: antenna, 16: frequency converter, 18: optical modulator

Claims (5)

During downstream communication, receiving an optical signal containing a first continuous light of a first frequency and a modulated light obtained by modulating a second continuous light of a second frequency different from the first frequency, and performing upstream communication a wireless device that receives an optical signal including the first continuous light and the second continuous light,
photoelectric conversion means for photoelectrically converting the received optical signal;
At the time of communication in the downlink direction, converting a first modulated signal obtained by the beat of the modulated light and the first continuous light output from the photoelectric conversion means into a first radio signal and transmitting the first radio signal to the user device, communication means for converting a second radio signal received from the user equipment into a second modulated signal and outputting the second modulated signal during uplink communication;
During upstream communication, the second modulated signal output by the communication means is frequency-converted by a signal obtained by the beat of the first continuous light and the second continuous light output by the photoelectric conversion means. frequency conversion means;
a modulating means for modulating the third continuous light with the second modulated signal after frequency conversion by the frequency converting means;
A wireless device comprising: During downstream communication, the signal output by the photoelectric conversion means is output to the communication means, and during upstream communication, the signal output by the photoelectric conversion means is output to the frequency conversion means. 2. The wireless device of claim 1, further comprising switch means. a splitter for outputting the signal output by the photoelectric conversion means from a first output port and a second output port;
During the downlink communication, the signal output from the first output port of the splitter is input to the communication means, and during the uplink communication, the second modulated signal output from the communication means is subjected to the frequency conversion. switch means for inputting to the means;
a filter provided between the frequency conversion means and the modulation means;
further comprising
2. The radio apparatus according to claim 1, wherein the signal output from said second output port of said splitter is input to said frequency conversion means. A wireless device for receiving an optical signal containing a first continuous light and a modulated light during downstream communication, and receiving an optical signal containing a second continuous light and a third continuous light during upstream communication,
a frequency difference between the first continuous light and the modulated light is a first frequency; a frequency difference between the second continuous light and the third continuous light is a second frequency different from the first frequency;
The wireless device
photoelectric conversion means for photoelectrically converting the received optical signal;
At the time of communication in the downlink direction, converting a first modulated signal obtained by the beat of the modulated light and the first continuous light output from the photoelectric conversion means into a first radio signal and transmitting the first radio signal to the user device, communication means for converting a second radio signal received from the user equipment into a second modulated signal and outputting the second modulated signal during uplink communication;
During upstream communication, the second modulated signal output by the communication means is frequency-converted by a signal obtained by the beat of the second continuous light and the third continuous light output by the photoelectric conversion means. frequency conversion means;
a modulating means for modulating the third continuous light with the second modulated signal after frequency conversion by the frequency converting means;
A wireless device comprising: The first modulated signal output by the photoelectric conversion means is output to the communication means, and the signal obtained by the beat of the second continuous light and the third continuous light output by the photoelectric conversion means is transmitted to the 5. The radio apparatus according to claim 4, further comprising branching means for outputting to the frequency conversion means.

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